feat: SMP stage 1 (4 harts, per-hart guarded stacks, home-core affinity, IPIs, TLB shootdown, one temporary kernel lock), 4-core storm

- caps record parent (mint/delegate/ipc), CapRef w/ pid+slot gens
- Revoke = delete subtree, keep self; drop/death re-parents children
- CreateRegion/MapRegion; mapping lives only as long as its cap
- drop Permission::Revoke + object-wide revoke
- mint any cap (badge only ep/ntfn), process caps delegable
- kani: descendants == subtree; model-based fuzz vs spec

.cargo/config.toml

@@ -1,3 +1,7 @@
 [target.riscv64gc-unknown-none-elf]
 runner = "qemu-system-riscv64 -machine virt -nographic -bios default -kernel"
 rustflags = ["-C", "panic=abort"]
+
+[env]
+# Kernel tables are large fixed arrays; tests build `Kernel` by value.
+RUST_MIN_STACK = "33554432"

Cargo.lock

@@ -245,7 +245,6 @@ dependencies = [
 name = "platform"
 version = "0.1.0"
 dependencies = [
- "domain",
  "types",
 ]
 

Cargo.toml

@@ -123,3 +123,10 @@ panic = "abort"
 
 [profile.dev]
 panic = "abort"
+
+# The randomized kernel invariant tests are too slow unoptimized.
+[profile.test.package.kernel]
+opt-level = 2
+
+[profile.test.package.domain]
+opt-level = 2

Makefile

@@ -1,10 +1,27 @@
-.PHONY: check fmt clippy test kani build all image run
+.PHONY: check fmt clippy test kani build all image run ci kernel-fmt kernel-clippy kernel-test
 
 RISCV_TARGET = riscv64gc-unknown-none-elf
 KERNEL_BIN = target/$(RISCV_TARGET)/release/adapter-riscv
+# Harts QEMU boots; `make run-gui SMP=1` for a single core.
+SMP ?= 4
+
+KERNEL_CRATES = -p types -p domain -p kernel -p platform
 
 all: check fmt clippy test
 
+# Gate for kernel work: formatting, lints, unit tests, Kani proofs, RISC-V build.
+ci: kernel-fmt kernel-clippy kernel-test kani build
+
+kernel-fmt:
+	cargo fmt $(KERNEL_CRATES) -p adapter-riscv -- --check
+
+kernel-clippy:
+	cargo clippy $(KERNEL_CRATES) --all-targets -- -D warnings
+	cargo clippy -p adapter-riscv --target $(RISCV_TARGET) --no-deps -- -D warnings
+
+kernel-test:
+	cargo test $(KERNEL_CRATES)
+
 check:
 	cargo check --workspace
 
@@ -17,14 +34,17 @@ clippy:
 test:
 	cargo test --workspace
 
+# CBMC can eat all RAM and take the desktop down with it; cap each run.
+KANI = systemd-run --user --scope -q -p MemoryMax=12G -p MemorySwapMax=0 cargo kani
+
 kani-types:
-	cargo kani -p types
+	$(KANI) -p types
 
 kani-domain:
-	cargo kani -p domain
+	$(KANI) -p domain
 
 kani-kernel:
-	cargo kani -p kernel
+	$(KANI) -p kernel
 
 kani: kani-types kani-domain kani-kernel
 
@@ -38,17 +58,17 @@ image: build
 	scripts/make-disk-image.sh
 
 run: build
-	qemu-system-riscv64 -machine virt -nographic -bios default \
+	qemu-system-riscv64 -machine virt -smp $(SMP) -nographic -bios default \
 		-kernel $(KERNEL_BIN)
 
 run-disk: image
-	qemu-system-riscv64 -machine virt -nographic -bios default \
+	qemu-system-riscv64 -machine virt -smp $(SMP) -nographic -bios default \
 		-kernel $(KERNEL_BIN) \
 		-drive file=boot.img,if=none,format=raw,id=hd0 \
 		-device virtio-blk-device,drive=hd0
 
 run-gui: image
-	qemu-system-riscv64 -machine virt -bios default \
+	qemu-system-riscv64 -machine virt -smp $(SMP) -bios default \
 		-kernel $(KERNEL_BIN) \
 		-drive file=boot.img,if=none,format=raw,id=hd0 \
 		-device virtio-blk-device,drive=hd0 \

crates/adapter-riscv/linker.ld

@@ -1,36 +1,60 @@
 OUTPUT_ARCH(riscv)
-ENTRY(_start)
 
+/* The kernel runs in the upper half: linked at its physical load address
+   plus PHYS_OFFSET (mmu::PHYS_OFFSET), loaded at the physical address.
+   Firmware jumps to the physical entry with the MMU off; _start switches
+   to the high mapping before any Rust code runs. */
+PHYS_OFFSET = 0xFFFFFFC000000000;
+LOAD_ADDRESS = 0x80200000;
+ENTRY(_start_phys)
+
+/* Every boundary below is page aligned: the kernel maps each range with
+   its own permissions (W^X), see mmu::init_kernel_page_table. */
 SECTIONS {
-    . = 0x80200000;
+    . = PHYS_OFFSET + LOAD_ADDRESS;
+    _text_start = .;
 
-    .text : {
+    .text : AT(ADDR(.text) - PHYS_OFFSET) {
         *(.text.entry)
         *(.text .text.*)
     }
 
     . = ALIGN(4096);
-    .rodata : {
+    _text_end = .;
+
+    .rodata : AT(ADDR(.rodata) - PHYS_OFFSET) {
         *(.rodata .rodata.*)
+        *(.srodata .srodata.*)
+    }
+    .eh_frame : AT(ADDR(.eh_frame) - PHYS_OFFSET) {
+        *(.eh_frame)
     }
 
     . = ALIGN(4096);
-    .data : {
+    _rodata_end = .;
+
+    .data : AT(ADDR(.data) - PHYS_OFFSET) {
         *(.data .data.*)
+        *(.sdata .sdata.*)
     }
 
     . = ALIGN(4096);
-    .bss : {
+    .bss : AT(ADDR(.bss) - PHYS_OFFSET) {
         _bss_start = .;
         *(.bss .bss.*)
         *(.sbss .sbss.*)
         _bss_end = .;
     }
 
+    /* One kernel stack per hart (smp::MAX_HARTS, smp::STACK_SLOT): each
+       slot is an unmapped guard page, so overflowing a stack faults
+       instead of silently overwriting what lies below, then the stack. */
     . = ALIGN(4096);
-    _stack_bottom = .;
-    . += 0x80000;
-    _stack_top = .;
+    _stacks_start = .;
+    . += 8 * (4096 + 0x80000);
+    _stacks_end = .;
 
     _heap_start = .;
 }
+
+_start_phys = _start - PHYS_OFFSET;

crates/adapter-riscv/src/board.rs

@@ -8,3 +8,29 @@ pub const CLINT_BASE: usize = 0x02000000;
 pub const USER_POOL_BASE: usize = 0x84000000;
 pub const USER_POOL_PAGES: usize = 4096;
 pub const TICK_INTERVAL: u64 = 10_000_000;
+
+/// QEMU virt's PLIC lines.
+const UART_IRQ: u16 = 10;
+const VIRTIO_IRQ_BASE: u16 = 1;
+const VIRTIO_SLOT_SIZE: usize = 0x1000;
+const VIRTIO_SLOTS: usize = VIRTIO_SIZE / VIRTIO_SLOT_SIZE;
+
+/// Every device userspace may drive: the UART and each VirtIO MMIO slot.
+/// The PLIC, CLINT and RAM stay the kernel's.
+pub fn devices() -> Option<[kernel::BoardDevice; 1 + VIRTIO_SLOTS]> {
+    use types::{address::PhysicalAddress, bounded::PageCount, id::IrqId};
+    let one = PageCount::new(1)?;
+    let device = |base: usize, irq: u16| kernel::BoardDevice {
+        base: PhysicalAddress::from_raw(base),
+        pages: one,
+        irq: Some(IrqId::from_raw(irq)),
+    };
+    let mut all = [device(UART_BASE, UART_IRQ); 1 + VIRTIO_SLOTS];
+    for (i, d) in all.iter_mut().skip(1).enumerate() {
+        *d = device(
+            VIRTIO_BASE + i * VIRTIO_SLOT_SIZE,
+            VIRTIO_IRQ_BASE + i as u16,
+        );
+    }
+    Some(all)
+}

crates/adapter-riscv/src/boot/caps.rs

@@ -22,37 +22,85 @@ pub fn grant_all(
         .with(types::permission::Permission::Read)
         .with(types::permission::Permission::Execute);
 
-    let storage_ep = kern().create_endpoint()
+    let storage_ep = kern()
+        .create_endpoint(storage_pid)
         .unwrap_or_else(|_| crate::halt(uart, "storage endpoint failed"));
 
-    kern().grant_capability(init_pid, domain::resource::Resource::Process(storage_pid), all_perms)
+    kern()
+        .grant_capability(
+            init_pid,
+            domain::resource::Resource::Process(storage_pid),
+            all_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
-    kern().grant_capability(init_pid, domain::resource::Resource::Endpoint(storage_ep), all_perms)
+    kern()
+        .grant_capability(
+            init_pid,
+            domain::resource::Resource::Endpoint(storage_ep),
+            all_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
 
-    kern().grant_capability(storage_pid, domain::resource::Resource::Endpoint(storage_ep), ipc_perms)
+    kern()
+        .grant_capability(
+            storage_pid,
+            domain::resource::Resource::Endpoint(storage_ep),
+            ipc_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
 
-    let display_ep = kern().create_endpoint()
+    let display_ep = kern()
+        .create_endpoint(display_pid)
         .unwrap_or_else(|_| crate::halt(uart, "display endpoint failed"));
 
-    kern().grant_capability(display_pid, domain::resource::Resource::Endpoint(display_ep), ipc_perms)
+    kern()
+        .grant_capability(
+            display_pid,
+            domain::resource::Resource::Endpoint(display_ep),
+            ipc_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
 
-    kern().grant_capability(init_pid, domain::resource::Resource::Endpoint(display_ep), all_perms)
+    kern()
+        .grant_capability(
+            init_pid,
+            domain::resource::Resource::Endpoint(display_ep),
+            all_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
-    kern().grant_capability(init_pid, domain::resource::Resource::Process(display_pid), all_perms)
+    kern()
+        .grant_capability(
+            init_pid,
+            domain::resource::Resource::Process(display_pid),
+            all_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
 
-    let input_ep = kern().create_endpoint()
+    let input_ep = kern()
+        .create_endpoint(input_pid)
         .unwrap_or_else(|_| crate::halt(uart, "input endpoint failed"));
 
-    kern().grant_capability(input_pid, domain::resource::Resource::Endpoint(input_ep), ipc_perms)
+    kern()
+        .grant_capability(
+            input_pid,
+            domain::resource::Resource::Endpoint(input_ep),
+            ipc_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
 
-    kern().grant_capability(init_pid, domain::resource::Resource::Endpoint(input_ep), all_perms)
+    kern()
+        .grant_capability(
+            init_pid,
+            domain::resource::Resource::Endpoint(input_ep),
+            all_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
-    kern().grant_capability(init_pid, domain::resource::Resource::Process(input_pid), all_perms)
+    kern()
+        .grant_capability(
+            init_pid,
+            domain::resource::Resource::Process(input_pid),
+            all_perms,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "grant failed"));
 
     uart.write_str("k-os: capabilities granted\n");

crates/adapter-riscv/src/boot/hardware.rs

@@ -1,6 +1,6 @@
 use crate::hw::uart::Uart;
 use crate::hw::virtio_blk::VirtioBlk;
-use crate::{board, kernel_cell::KernelCell, mmu, platform, trap, KERNEL};
+use crate::{KERNEL, board, mmu, platform, trap};
 
 unsafe extern "C" {
     static _bss_start: u8;
@@ -8,26 +8,66 @@ unsafe extern "C" {
     static _heap_start: u8;
 }
 
-pub fn init(uart: &Uart) -> &'static mut mmu::PageTable {
+pub fn init(uart: &Uart, boot_hart: usize) -> &'static mut mmu::PageTable {
     zero_bss();
 
     let heap_start = unsafe { &_heap_start as *const u8 as usize };
     mmu::init_allocator(heap_start);
     let kernel_pt = mmu::init_kernel_page_table();
+    let harts = crate::smp::probe_harts();
+    if boot_hart >= harts {
+        crate::halt(uart, "boot hart outside the hart range");
+    }
+    crate::smp::init(
+        boot_hart,
+        harts,
+        mmu::virt_to_phys(kernel_pt as *const mmu::PageTable as usize),
+    );
     mmu::activate(kernel_pt);
     uart.write_str("k-os: MMU enabled (Sv39)\n");
+    match mmu::check_wx(kernel_pt) {
+        Ok(code_pages) => {
+            uart.write_str("k-os: W^X verified, ");
+            uart.write_dec(code_pages);
+            uart.write_str(" code pages\n");
+        }
+        Err(v) => {
+            let (what, va) = match v {
+                mmu::page_table::WxViolation::WritableCode(va) => ("writable code", va),
+                mmu::page_table::WxViolation::ExecutableData(va) => ("executable data", va),
+                mmu::page_table::WxViolation::MappedHole(va) => ("mapped hole", va),
+                mmu::page_table::WxViolation::LowerHalf(va) => ("lower-half mapping", va),
+            };
+            uart.write_str("k-os: W^X violation: ");
+            uart.write_str(what);
+            uart.write_str(" at ");
+            uart.write_hex(va);
+            uart.put_char(b'\n');
+            crate::halt(uart, "kernel page table violates W^X");
+        }
+    }
 
     trap::init();
     crate::hw::timer::init();
     crate::hw::plic::Plic::init();
     uart.write_str("k-os: traps and timer initialized\n");
 
-    let riscv_platform = platform::RiscVPlatform::new(kernel_pt as *const mmu::PageTable as usize);
-    let pool = domain::memory::page_pool::PagePool::new(
+    if board::USER_POOL_PAGES > domain::memory::frame::MAX_FRAMES {
+        crate::halt(uart, "user pool larger than the frame table");
+    }
+    let riscv_platform =
+        platform::RiscVPlatform::new(kernel_pt as *const mmu::PageTable as usize, harts as u8);
+    // SAFETY: `init_in_place` writes every field of the kernel.
+    unsafe {
+        KERNEL.init_with(|slot| {
+            kernel::Kernel::init_in_place(
+                slot,
+                riscv_platform,
                 types::address::PhysicalAddress::from_raw(board::USER_POOL_BASE),
                 board::USER_POOL_PAGES,
-    );
-    KERNEL.init(kernel::Kernel::new(riscv_platform, pool));
+            )
+        });
+    }
 
     kernel_pt
 }

crates/adapter-riscv/src/boot/loader.rs

@@ -1,84 +1,74 @@
 use crate::hw::uart::Uart;
 use crate::hw::virtio_blk::VirtioBlk;
 use crate::{boot_fs, mmu};
+use types::address::VirtualAddress;
 use types::id::{ProcessId, ThreadId};
+use types::mapping::PagePerms;
 
+const PAGE_SIZE: usize = mmu::PAGE_SIZE;
 const USER_VA_BASE: usize = 0x10000;
+/// The stack sits just below the image and stops short of the null page.
+const USER_STACK_PAGES: usize = USER_VA_BASE / PAGE_SIZE - 1;
 const MAX_FILE_SIZE: usize = 64 * 1024;
 
 pub struct LoadedProcess {
     pub pid: ProcessId,
-    pub entry: usize,
 }
 
 fn kern() -> &'static mut kernel::Kernel<crate::platform::RiscVPlatform> {
     unsafe { &mut *crate::kernel_ptr() }
 }
 
-pub fn load_init(
-    uart: &Uart,
-    blk: &mut VirtioBlk,
-    kernel_pt: &mmu::PageTable,
-) -> (LoadedProcess, ThreadId) {
+/// Scratch space for reading ELF files, allocated once from the boot heap.
+fn elf_buffer() -> &'static mut [u8] {
+    static mut BUF: usize = 0;
+    // SAFETY: boot is single threaded; the buffer is kernel-only memory
+    // from the boot allocator and is never handed to a process.
+    unsafe {
+        if BUF == 0 {
+            BUF = mmu::allocator::alloc_zeroed_page();
+            for _ in 1..MAX_FILE_SIZE / PAGE_SIZE {
+                mmu::allocator::alloc_zeroed_page();
+            }
+        }
+        core::slice::from_raw_parts_mut(BUF as *mut u8, MAX_FILE_SIZE)
+    }
+}
+
+pub fn load_init(uart: &Uart, blk: &mut VirtioBlk) -> (LoadedProcess, ThreadId) {
     let (pid, tid) = kern()
-        .boot(types::bounded::Priority::DEFAULT, types::time::TimeSlice::DEFAULT)
+        .boot(
+            types::bounded::Priority::DEFAULT,
+            types::time::TimeSlice::DEFAULT,
+        )
         .unwrap_or_else(|_| crate::halt(uart, "boot failed"));
 
-    let entry = load_elf(blk, kernel_pt, pid, b"init.elf");
-    if entry == 0 { crate::halt(uart, "init.elf not found"); }
+    let entry = load_elf(uart, blk, pid, b"init.elf");
     setup_thread(tid, entry);
     uart.write_str("k-os: init loaded\n");
 
-    (LoadedProcess { pid, entry }, tid)
+    (LoadedProcess { pid }, tid)
 }
 
 pub fn load_server(
     uart: &Uart,
     blk: &mut VirtioBlk,
-    kernel_pt: &mmu::PageTable,
     filename: &[u8],
     label: &str,
 ) -> LoadedProcess {
-    let pid = kern().create_process_internal()
+    let pid = kern()
+        .create_process_internal()
         .unwrap_or_else(|| crate::halt(uart, "process create failed"));
-    let entry = load_elf(blk, kernel_pt, pid, filename);
-    if entry == 0 { crate::halt(uart, "elf not found"); }
-    let tid = kern().spawn_thread_internal(pid)
+    let entry = load_elf(uart, blk, pid, filename);
+    let tid = kern()
+        .spawn_thread_internal(pid)
         .unwrap_or_else(|| crate::halt(uart, "thread spawn failed"));
     setup_thread(tid, entry);
     uart.write_str("k-os: ");
     uart.write_str(label);
     uart.write_str(" loaded\n");
 
-    LoadedProcess { pid, entry }
-}
-
-pub fn enter_userspace(pid: ProcessId, entry: usize, shared_buf_va: usize) -> ! {
-    let pt_addr = kern().platform_mut().page_table_for(pid);
-    if pt_addr != 0 {
-        mmu::activate(unsafe { &*(pt_addr as *const mmu::PageTable) });
-    }
-
-    let kernel_sp: usize;
-    unsafe { core::arch::asm!("mv {0}, sp", out(reg) kernel_sp) };
-    crate::trap::set_kernel_stack(kernel_sp);
-
-    unsafe {
-        core::arch::asm!(
-            "csrc sstatus, {spp}",
-            "csrs sstatus, {spie}",
-            "csrw sepc, {entry}",
-            "mv sp, {stack}",
-            "mv a0, {arg}",
-            "sret",
-            spp = in(reg) 1usize << 8,
-            spie = in(reg) 1usize << 5,
-            entry = in(reg) entry,
-            stack = in(reg) USER_VA_BASE,
-            arg = in(reg) shared_buf_va,
-            options(noreturn),
-        );
-    }
+    LoadedProcess { pid }
 }
 
 fn setup_thread(tid: ThreadId, entry: usize) {
@@ -89,88 +79,89 @@ fn setup_thread(tid: ThreadId, entry: usize) {
     }
 }
 
-fn load_elf(
-    blk: &mut VirtioBlk,
-    kernel_pt: &mmu::PageTable,
-    pid: ProcessId,
-    filename: &[u8],
-) -> usize {
-    let buf_base = mmu::allocator::alloc_zeroed_page();
-    let file_pages = MAX_FILE_SIZE / 4096;
-    for _ in 1..file_pages {
-        mmu::allocator::alloc_zeroed_page();
-    }
-    let buf = unsafe { core::slice::from_raw_parts_mut(buf_base as *mut u8, MAX_FILE_SIZE) };
-
-    let file_size = boot_fs::read_file_from_disk(blk, filename, buf).unwrap_or(0);
-    if file_size == 0 { return 0; }
-
-    let elf_info = match elf::parse(&buf[..file_size]) {
-        Ok(info) => info,
-        Err(_) => return 0,
+/// Copies `data` into `pid`'s already mapped pages starting at `va`.
+fn copy_to_user(pid: ProcessId, va: usize, data: &[u8]) -> bool {
+    let mut done = 0;
+    while done < data.len() {
+        let addr = va + done;
+        let page = addr & !(PAGE_SIZE - 1);
+        let offset = addr - page;
+        let Some(pa) = kern().user_page_frame(pid, VirtualAddress::from_raw(page)) else {
+            return false;
         };
-
-    let user_pt = mmu::create_user_page_table(
-        kernel_pt,
-        types::address::PhysicalAddress::from_raw(0),
-        0,
-        types::address::VirtualAddress::from_raw(USER_VA_BASE),
-    );
-
-    for segment in elf_info.segments() {
-        let page_start = segment.vaddr & !0xFFF;
-        let offset_in_page = segment.vaddr & 0xFFF;
-        let total_size = offset_in_page + segment.mem_size;
-        let seg_pages = (total_size + 4095) / 4096;
-
-        for p in 0..seg_pages {
-            let page = mmu::allocator::alloc_zeroed_page();
-            let page_va = page_start + p * 4096;
-            let seg_file_start = if p == 0 { 0 } else { p * 4096 - offset_in_page };
-            let dest_off = if p == 0 { offset_in_page } else { 0 };
-            let copy_len = if seg_file_start < segment.file_size {
-                (segment.file_size - seg_file_start).min(4096 - dest_off)
-            } else { 0 };
-
-            if copy_len > 0 {
-                let src = segment.file_offset + seg_file_start;
-                if src + copy_len <= file_size {
+        let len = (PAGE_SIZE - offset).min(data.len() - done);
+        // SAFETY: `pa` is a pool frame the kernel just mapped for `pid`;
+        // pool frames are RAM, mapped at `phys_to_virt`.
         unsafe {
             core::ptr::copy_nonoverlapping(
-                            buf.as_ptr().add(src),
-                            (page as *mut u8).add(dest_off),
-                            copy_len,
+                data.as_ptr().add(done),
+                (mmu::phys_to_virt(pa.raw()) as *mut u8).add(offset),
+                len,
             );
         }
+        done += len;
+    }
+    true
+}
+
+fn segment_perms(flags: elf::SegmentFlags) -> Option<PagePerms> {
+    match (flags.write, flags.execute) {
+        (true, true) => None,
+        (false, true) => Some(PagePerms::ReadExecute),
+        (true, false) => Some(PagePerms::ReadWrite),
+        (false, false) => Some(PagePerms::ReadOnly),
     }
 }
 
-            let flags = if segment.flags.execute {
-                mmu::Sv39Flags::user_rx()
-            } else if segment.flags.write {
-                mmu::Sv39Flags::user_rw()
-            } else {
-                mmu::Sv39Flags::user_rx()
-            };
-            mmu::map(user_pt, mmu::Mapping {
-                va: types::address::VirtualAddress::from_raw(page_va),
-                pa: types::address::PhysicalAddress::from_raw(page),
-                pages: 1,
-                flags,
-            });
+/// Loads `filename` into `pid` through the kernel's own mapping API, so
+/// every page is tracked, charged and checked like any other. Halts on any
+/// malformed or overlapping image: boot servers are trusted to be sane.
+fn load_elf(uart: &Uart, blk: &mut VirtioBlk, pid: ProcessId, filename: &[u8]) -> usize {
+    let buf = elf_buffer();
+    let file_size = boot_fs::read_file_from_disk(blk, filename, buf).unwrap_or(0);
+    if file_size == 0 {
+        crate::halt(uart, "ELF not found");
+    }
+    let file = &buf[..file_size];
+    let elf_info = elf::parse(file).unwrap_or_else(|_| crate::halt(uart, "bad ELF"));
+
+    for segment in elf_info.segments() {
+        let perms =
+            segment_perms(segment.flags).unwrap_or_else(|| crate::halt(uart, "W+X segment"));
+        let page_start = segment.vaddr & !(PAGE_SIZE - 1);
+        let offset_in_page = segment.vaddr - page_start;
+        let pages = offset_in_page
+            .checked_add(segment.mem_size)
+            .map(|total| total.div_ceil(PAGE_SIZE))
+            .unwrap_or_else(|| crate::halt(uart, "segment too large"));
+        if pages == 0 {
+            continue;
+        }
+
+        kern()
+            .map_fresh_range(pid, VirtualAddress::from_raw(page_start), pages, perms)
+            .unwrap_or_else(|_| crate::halt(uart, "cannot map segment"));
+
+        let copy_len = segment.file_size.min(segment.mem_size);
+        let data = segment
+            .file_offset
+            .checked_add(copy_len)
+            .and_then(|end| file.get(segment.file_offset..end))
+            .unwrap_or_else(|| crate::halt(uart, "segment outside file"));
+        if !copy_to_user(pid, segment.vaddr, data) {
+            crate::halt(uart, "segment copy failed");
         }
     }
 
-    for i in 0..16usize {
-        let sp = mmu::allocator::alloc_zeroed_page();
-        mmu::map(user_pt, mmu::Mapping {
-            va: types::address::VirtualAddress::from_raw(USER_VA_BASE - (16 - i) * 4096),
-            pa: types::address::PhysicalAddress::from_raw(sp),
-            pages: 1,
-            flags: mmu::Sv39Flags::user_rw(),
-        });
-    }
+    let stack_bottom = USER_VA_BASE - USER_STACK_PAGES * PAGE_SIZE;
+    kern()
+        .map_fresh_range(
+            pid,
+            VirtualAddress::from_raw(stack_bottom),
+            USER_STACK_PAGES,
+            PagePerms::ReadWrite,
+        )
+        .unwrap_or_else(|_| crate::halt(uart, "cannot map stack"));
 
-    kern().platform_mut().set_page_table(pid, user_pt as *const mmu::PageTable as usize);
     elf_info.entry_point
 }

crates/adapter-riscv/src/boot_fs.rs

@@ -1,11 +1,9 @@
 use crate::hw::virtio_blk::VirtioBlk;
 
 const SECTOR_SIZE: usize = 512;
-const MAX_FILE_SIZE: usize = 64 * 1024; // 64K max for init binary
 
 struct BootFat16 {
     reserved_sectors: u16,
-    sectors_per_fat: u16,
     root_dir_start: u32,
     root_dir_sectors: u32,
     data_start: u32,
@@ -19,7 +17,9 @@ impl BootFat16 {
         }
 
         let bytes_per_sector = u16::from_le_bytes([boot_sector[11], boot_sector[12]]);
-        if bytes_per_sector != SECTOR_SIZE as u16 { return None; }
+        if bytes_per_sector != SECTOR_SIZE as u16 {
+            return None;
+        }
 
         let sectors_per_cluster = boot_sector[13];
         let reserved_sectors = u16::from_le_bytes([boot_sector[14], boot_sector[15]]);
@@ -29,12 +29,11 @@ impl BootFat16 {
 
         let fat_start = reserved_sectors as u32;
         let root_dir_start = fat_start + (num_fats as u32) * (sectors_per_fat as u32);
-        let root_dir_sectors = ((root_entry_count as u32) * 32 + 511) / 512;
+        let root_dir_sectors = ((root_entry_count as u32) * 32).div_ceil(512);
         let data_start = root_dir_start + root_dir_sectors;
 
         Some(Self {
             reserved_sectors,
-            sectors_per_fat,
             root_dir_start,
             root_dir_sectors,
             data_start,
@@ -50,7 +49,9 @@ impl BootFat16 {
 fn to_fat_name(name: &[u8]) -> [u8; 11] {
     let mut fat = [b' '; 11];
     let dot_pos = name.iter().position(|&b| b == b'.').unwrap_or(name.len());
-    for i in 0..dot_pos.min(8) { fat[i] = name[i].to_ascii_uppercase(); }
+    for i in 0..dot_pos.min(8) {
+        fat[i] = name[i].to_ascii_uppercase();
+    }
     if dot_pos < name.len() {
         for i in 0..(name.len() - dot_pos - 1).min(3) {
             fat[8 + i] = name[dot_pos + 1 + i].to_ascii_uppercase();
@@ -67,7 +68,9 @@ pub fn read_file_from_disk(
     let mut sector_buf = [0u8; SECTOR_SIZE];
 
     // Read boot sector
-    if !blk.read_sector(0, &mut sector_buf) { return None; }
+    if !blk.read_sector(0, &mut sector_buf) {
+        return None;
+    }
     let fs = BootFat16::parse(&sector_buf)?;
 
     let fat_name = to_fat_name(filename);
@@ -78,36 +81,52 @@ pub fn read_file_from_disk(
     let mut found = false;
 
     for s in 0..fs.root_dir_sectors {
-        if !blk.read_sector((fs.root_dir_start + s) as u32, &mut sector_buf) { continue; }
+        if !blk.read_sector(fs.root_dir_start + s, &mut sector_buf) {
+            continue;
+        }
         for i in 0..(SECTOR_SIZE / 32) {
             let off = i * 32;
-            if sector_buf[off] == 0x00 { break; }
-            if sector_buf[off] == 0xE5 { continue; }
+            if sector_buf[off] == 0x00 {
+                break;
+            }
+            if sector_buf[off] == 0xE5 {
+                continue;
+            }
             if sector_buf[off..off + 11] == fat_name {
                 first_cluster = u16::from_le_bytes([sector_buf[off + 26], sector_buf[off + 27]]);
                 file_size = u32::from_le_bytes([
-                    sector_buf[off + 28], sector_buf[off + 29],
-                    sector_buf[off + 30], sector_buf[off + 31],
+                    sector_buf[off + 28],
+                    sector_buf[off + 29],
+                    sector_buf[off + 30],
+                    sector_buf[off + 31],
                 ]);
                 found = true;
                 break;
             }
         }
-        if found { break; }
+        if found {
+            break;
+        }
     }
 
-    if !found { return None; }
+    if !found {
+        return None;
+    }
 
     let size = (file_size as usize).min(out_buf.len());
     let mut read = 0;
     let mut cluster = first_cluster;
     let sectors_per_cluster = fs.sectors_per_cluster as u32;
 
-    while read < size && cluster >= 2 && cluster < 0xFFF8 {
+    while read < size && (2..0xFFF8).contains(&cluster) {
         for s in 0..sectors_per_cluster {
-            if read >= size { break; }
+            if read >= size {
+                break;
+            }
             let sector = fs.cluster_to_sector(cluster) + s;
-            if !blk.read_sector(sector, &mut sector_buf) { return Some(read); }
+            if !blk.read_sector(sector, &mut sector_buf) {
+                return Some(read);
+            }
             let chunk = (size - read).min(SECTOR_SIZE);
             out_buf[read..read + chunk].copy_from_slice(&sector_buf[..chunk]);
             read += chunk;
@@ -117,7 +136,9 @@ pub fn read_file_from_disk(
         let fat_offset = (cluster as u32) * 2;
         let fat_sector = fs.reserved_sectors as u32 + fat_offset / SECTOR_SIZE as u32;
         let fat_byte = (fat_offset % SECTOR_SIZE as u32) as usize;
-        if !blk.read_sector(fat_sector, &mut sector_buf) { break; }
+        if !blk.read_sector(fat_sector, &mut sector_buf) {
+            break;
+        }
         cluster = u16::from_le_bytes([sector_buf[fat_byte], sector_buf[fat_byte + 1]]);
     }
 

crates/adapter-riscv/src/devices/gpu_setup.rs

@@ -1,13 +1,9 @@
+use super::{dma_buffer, info_page, kern, map_mmio};
 use crate::hw::uart::Uart;
 use crate::hw::virtio_gpu::VirtioGpu;
-use crate::mmu;
 use types::display::Dimension;
 use types::id::ProcessId;
 
-fn kern() -> &'static mut kernel::Kernel<crate::platform::RiscVPlatform> {
-    unsafe { &mut *crate::kernel_ptr() }
-}
-
 const GPU_VA: usize = 0x20000;
 const VQUEUE_VA: usize = 0x21000;
 const CMDBUF_VA: usize = 0x23000;
@@ -15,6 +11,8 @@ const PHYSINFO_VA: usize = 0x24000;
 const FB_VA: usize = 0x100000;
 const DEFAULT_WIDTH: Dimension = Dimension::new(640);
 const DEFAULT_HEIGHT: Dimension = Dimension::new(480);
+/// The framebuffer alone is ~1000 pages at 1280x800.
+const DISPLAY_PAGE_LIMIT: usize = 2048;
 
 pub fn configure(uart: &Uart, display_pid: ProcessId) {
     let gpu = match VirtioGpu::probe() {
@@ -25,28 +23,24 @@ pub fn configure(uart: &Uart, display_pid: ProcessId) {
         }
     };
 
-    let pt_addr = kern().platform_mut().page_table_for(display_pid);
-    let pt = unsafe { &mut *(pt_addr as *mut mmu::PageTable) };
+    kern()
+        .set_page_limit(display_pid, DISPLAY_PAGE_LIMIT)
+        .unwrap_or_else(|_| crate::halt(uart, "display quota"));
 
-    map_page(pt, GPU_VA, gpu.base());
-
-    let vq_phys = alloc_contiguous(2);
-    map_range(pt, VQUEUE_VA, vq_phys, 2);
-
-    let cmd_phys = mmu::allocator::alloc_zeroed_page();
-    map_page(pt, CMDBUF_VA, cmd_phys);
+    map_mmio(uart, display_pid, GPU_VA, gpu.base(), 1);
+    let vq_phys = dma_buffer(uart, display_pid, VQUEUE_VA, 2);
+    let cmd_phys = dma_buffer(uart, display_pid, CMDBUF_VA, 1);
 
     gpu.init_device(vq_phys);
 
-    let queue = hw_virtio::queue::VirtioQueue::new(
-        hw_virtio::queue::QueueAddrs::from_base(vq_phys),
-    );
+    let queue = hw_virtio::queue::VirtioQueue::new(hw_virtio::queue::QueueAddrs::from_base(
+        crate::mmu::phys_to_virt(vq_phys),
+    ));
     let dma = hw_virtio::gpu::GpuDmaAddrs {
         cmd_pa: types::address::PhysicalAddress::from_raw(cmd_phys),
-        cmd_va: types::address::VirtualAddress::from_raw(cmd_phys),
+        cmd_va: types::address::VirtualAddress::from_raw(crate::mmu::phys_to_virt(cmd_phys)),
         resp_pa: types::address::PhysicalAddress::from_raw(cmd_phys + 512),
     };
-    use hw_virtio::mmio::MmioAccess;
 
     let (width, height) = match hw_virtio::gpu::get_display_info(gpu.mmio(), &queue, &dma) {
         Some((w, h)) => {
@@ -63,20 +57,21 @@ pub fn configure(uart: &Uart, display_pid: ProcessId) {
         }
     };
 
-    let fb_pages = (width.raw() as usize * height.raw() as usize * 4 + 4095) / 4096;
-    let fb_phys = alloc_contiguous(fb_pages);
-    map_range(pt, FB_VA, fb_phys, fb_pages);
+    let fb_pages = (width.raw() as usize * height.raw() as usize * 4).div_ceil(4096);
+    let fb_phys = dma_buffer(uart, display_pid, FB_VA, fb_pages);
 
-    let info_phys = mmu::allocator::alloc_zeroed_page();
-    map_page(pt, PHYSINFO_VA, info_phys);
-    unsafe {
-        let info = info_phys as *mut u64;
-        core::ptr::write_volatile(info, cmd_phys as u64);
-        core::ptr::write_volatile(info.add(1), (cmd_phys + 512) as u64);
-        core::ptr::write_volatile(info.add(2), fb_phys as u64);
-        core::ptr::write_volatile(info.add(3), width.raw() as u64);
-        core::ptr::write_volatile(info.add(4), height.raw() as u64);
-    }
+    info_page(
+        uart,
+        display_pid,
+        PHYSINFO_VA,
+        &[
+            cmd_phys as u64,
+            (cmd_phys + 512) as u64,
+            fb_phys as u64,
+            width.raw() as u64,
+            height.raw() as u64,
+        ],
+    );
 
     if gpu.setup_framebuffer(cmd_phys, vq_phys, fb_phys, width, height) {
         uart.write_str("k-os: VirtIO GPU configured\n");
@@ -84,26 +79,3 @@ pub fn configure(uart: &Uart, display_pid: ProcessId) {
         uart.write_str("k-os: VirtIO GPU setup failed (display will be headless)\n");
     }
 }
-
-fn map_page(pt: &mut mmu::PageTable, va: usize, pa: usize) {
-    mmu::map(pt, mmu::Mapping {
-        va: types::address::VirtualAddress::from_raw(va),
-        pa: types::address::PhysicalAddress::from_raw(pa),
-        pages: 1,
-        flags: mmu::Sv39Flags::user_rw(),
-    });
-}
-
-fn map_range(pt: &mut mmu::PageTable, va_base: usize, pa_base: usize, count: usize) {
-    for i in 0..count {
-        map_page(pt, va_base + i * 4096, pa_base + i * 4096);
-    }
-}
-
-fn alloc_contiguous(pages: usize) -> usize {
-    let first = mmu::allocator::alloc_zeroed_page();
-    for _ in 1..pages {
-        mmu::allocator::alloc_zeroed_page();
-    }
-    first
-}

crates/adapter-riscv/src/devices/input_setup.rs

@@ -1,5 +1,6 @@
+use super::{dma_buffer, info_page, map_mmio};
+use crate::board;
 use crate::hw::uart::Uart;
-use crate::{board, mmu};
 use types::id::ProcessId;
 
 const UART_VA: usize = 0x20000;
@@ -8,34 +9,23 @@ const INPUT_VQUEUE_VA: usize = 0x26000;
 const INPUT_EVBUF_VA: usize = 0x28000;
 const INPUT_PHYSINFO_VA: usize = 0x29000;
 
-fn kern() -> &'static mut kernel::Kernel<crate::platform::RiscVPlatform> {
-    unsafe { &mut *crate::kernel_ptr() }
-}
-
 pub fn configure(uart: &Uart, input_pid: ProcessId) {
-    let pt_addr = kern().platform_mut().page_table_for(input_pid);
-    let pt = unsafe { &mut *(pt_addr as *mut mmu::PageTable) };
-
     // Always map UART for fallback
-    map_page(pt, UART_VA, board::UART_BASE);
+    map_mmio(uart, input_pid, UART_VA, board::UART_BASE, 1);
 
     // Try to find VirtIO input device
-    if let Some(mmio) = hw_virtio::mmio::scan_for_device(hw_virtio::mmio::DEVICE_ID_INPUT) {
-        let base = mmio.base();
-        map_page(pt, INPUT_MMIO_VA, base);
-
-        let vq_phys = alloc_contiguous(2);
-        map_range(pt, INPUT_VQUEUE_VA, vq_phys, 2);
-
-        let evbuf_phys = mmu::allocator::alloc_zeroed_page();
-        map_page(pt, INPUT_EVBUF_VA, evbuf_phys);
-
-        let info_phys = mmu::allocator::alloc_zeroed_page();
-        map_page(pt, INPUT_PHYSINFO_VA, info_phys);
-        unsafe {
-            core::ptr::write_volatile(info_phys as *mut u64, evbuf_phys as u64);
-            core::ptr::write_volatile((info_phys as *mut u64).add(1), vq_phys as u64);
-        }
+    let first = crate::mmu::phys_to_virt(hw_virtio::mmio::MMIO_FIRST);
+    if let Some(mmio) = hw_virtio::mmio::scan_for_device(first, hw_virtio::mmio::DEVICE_ID_INPUT) {
+        let base = crate::mmu::virt_to_phys(mmio.base());
+        map_mmio(uart, input_pid, INPUT_MMIO_VA, base, 1);
+        let vq_phys = dma_buffer(uart, input_pid, INPUT_VQUEUE_VA, 2);
+        let evbuf_phys = dma_buffer(uart, input_pid, INPUT_EVBUF_VA, 1);
+        info_page(
+            uart,
+            input_pid,
+            INPUT_PHYSINFO_VA,
+            &[evbuf_phys as u64, vq_phys as u64],
+        );
 
         hw_virtio::mmio::init_legacy_device(&mmio, vq_phys, 32);
         uart.write_str("k-os: VirtIO keyboard configured\n");
@@ -43,26 +33,3 @@ pub fn configure(uart: &Uart, input_pid: ProcessId) {
         uart.write_str("k-os: UART mapped for input\n");
     }
 }
-
-fn map_page(pt: &mut mmu::PageTable, va: usize, pa: usize) {
-    mmu::map(pt, mmu::Mapping {
-        va: types::address::VirtualAddress::from_raw(va),
-        pa: types::address::PhysicalAddress::from_raw(pa),
-        pages: 1,
-        flags: mmu::Sv39Flags::user_rw(),
-    });
-}
-
-fn map_range(pt: &mut mmu::PageTable, va_base: usize, pa_base: usize, count: usize) {
-    for i in 0..count {
-        map_page(pt, va_base + i * 4096, pa_base + i * 4096);
-    }
-}
-
-fn alloc_contiguous(pages: usize) -> usize {
-    let first = mmu::allocator::alloc_zeroed_page();
-    for _ in 1..pages {
-        mmu::allocator::alloc_zeroed_page();
-    }
-    first
-}

crates/adapter-riscv/src/devices/mod.rs

@@ -1,3 +1,91 @@
 pub mod gpu_setup;
 pub mod input_setup;
 pub mod storage_setup;
+
+use crate::hw::uart::Uart;
+use types::address::{PhysicalAddress, VirtualAddress};
+use types::bounded::PageCount;
+use types::id::ProcessId;
+use types::mapping::PagePerms;
+
+// Boot-time device wiring. Everything here goes through the kernel's
+// mapping API so the kernel knows about every page a driver can touch.
+// Device regions come from the board table and belong to init, which
+// also holds capabilities to them; moving drivers onto those caps is
+// userspace work.
+
+fn kern() -> &'static mut kernel::Kernel<crate::platform::RiscVPlatform> {
+    unsafe { &mut *crate::kernel_ptr() }
+}
+
+fn pages(uart: &Uart, n: usize) -> PageCount {
+    u16::try_from(n)
+        .ok()
+        .and_then(PageCount::new)
+        .unwrap_or_else(|| crate::halt(uart, "bad page count"))
+}
+
+/// Maps the board device region at `pa` into `pid` at `va`. The region
+/// belongs to init (see `kernel::Kernel::register_board`); `n` must match
+/// its size.
+pub(crate) fn map_mmio(uart: &Uart, pid: ProcessId, va: usize, pa: usize, n: usize) {
+    let id = kern()
+        .device_region_at(PhysicalAddress::from_raw(pa))
+        .unwrap_or_else(|| crate::halt(uart, "no such board device"));
+    if kern().region_pages(id).map(|p| p.value() as usize) != Some(n) {
+        crate::halt(uart, "device size mismatch");
+    }
+    kern()
+        .map_region(id, pid, VirtualAddress::from_raw(va), PagePerms::ReadWrite)
+        .unwrap_or_else(|_| crate::halt(uart, "device map failed"));
+}
+
+/// Physically contiguous, zeroed DMA memory for `owner`, mapped read-write
+/// at `va`. Returns its physical base for programming the device.
+pub(crate) fn dma_buffer(uart: &Uart, owner: ProcessId, va: usize, n: usize) -> usize {
+    let id = kern()
+        .create_pool_region(owner, pages(uart, n))
+        .unwrap_or_else(|_| crate::halt(uart, "DMA region failed"));
+    kern()
+        .map_region(
+            id,
+            owner,
+            VirtualAddress::from_raw(va),
+            PagePerms::ReadWrite,
+        )
+        .unwrap_or_else(|_| crate::halt(uart, "DMA map failed"));
+    kern()
+        .region_base(id)
+        .unwrap_or_else(|| crate::halt(uart, "DMA region vanished"))
+        .raw()
+}
+
+/// Shares a fresh region between `owner` and `other` at the same `va`.
+pub(crate) fn shared_buffer(uart: &Uart, owner: ProcessId, other: ProcessId, va: usize, n: usize) {
+    let id = kern()
+        .create_pool_region(owner, pages(uart, n))
+        .unwrap_or_else(|_| crate::halt(uart, "shared region failed"));
+    for pid in [owner, other] {
+        kern()
+            .map_region(id, pid, VirtualAddress::from_raw(va), PagePerms::ReadWrite)
+            .unwrap_or_else(|_| crate::halt(uart, "shared map failed"));
+    }
+}
+
+/// Writes `words` into a fresh page mapped at `va` in `pid`, so a driver
+/// can learn the physical addresses of its DMA buffers.
+pub(crate) fn info_page(uart: &Uart, pid: ProcessId, va: usize, words: &[u64]) {
+    let va = VirtualAddress::from_raw(va);
+    kern()
+        .map_fresh_range(pid, va, 1, PagePerms::ReadOnly)
+        .unwrap_or_else(|_| crate::halt(uart, "info page failed"));
+    let pa = kern()
+        .user_page_frame(pid, va)
+        .unwrap_or_else(|| crate::halt(uart, "info page vanished"));
+    let info = crate::mmu::phys_to_virt(pa.raw()) as *mut u64;
+    for (i, &w) in words.iter().enumerate() {
+        // SAFETY: `pa` is a pool frame just mapped for `pid`, reachable at
+        // `phys_to_virt`, and `words` fits in one page.
+        unsafe { core::ptr::write_volatile(info.add(i), w) };
+    }
+}

crates/adapter-riscv/src/devices/storage_setup.rs

@@ -1,11 +1,7 @@
+use super::{dma_buffer, info_page, map_mmio, shared_buffer};
 use crate::hw::uart::Uart;
-use crate::mmu;
 use types::id::ProcessId;
 
-fn kern() -> &'static mut kernel::Kernel<crate::platform::RiscVPlatform> {
-    unsafe { &mut *crate::kernel_ptr() }
-}
-
 const VIRTIO_VA: usize = 0x20000;
 const VQUEUE_VA: usize = 0x21000;
 const REQHDR_VA: usize = 0x23000;
@@ -13,102 +9,28 @@ const PHYSINFO_VA: usize = 0x24000;
 const SHARED_BUF_VA: usize = 0x30000;
 const SHARED_BUF_PAGES: usize = 16;
 
-pub fn configure(
-    uart: &Uart,
-    init_pid: ProcessId,
-    storage_pid: ProcessId,
-    virtio_base: usize,
-) {
-    let storage_pt = get_pt(storage_pid);
-    let init_pt = get_pt(init_pid);
-
-    map_virtio_mmio(storage_pt, virtio_base);
-    let vqueue_phys = alloc_and_map_virtqueue(storage_pt);
-    let reqhdr_phys = alloc_and_map_reqhdr(storage_pt);
-    write_phys_info(storage_pt, reqhdr_phys);
+pub fn configure(uart: &Uart, init_pid: ProcessId, storage_pid: ProcessId, virtio_base: usize) {
+    map_mmio(uart, storage_pid, VIRTIO_VA, virtio_base, 1);
+    let vqueue_phys = dma_buffer(uart, storage_pid, VQUEUE_VA, 2);
+    let reqhdr_phys = dma_buffer(uart, storage_pid, REQHDR_VA, 1);
+    info_page(
+        uart,
+        storage_pid,
+        PHYSINFO_VA,
+        &[
+            reqhdr_phys as u64,
+            (reqhdr_phys + 16) as u64,
+            (reqhdr_phys + 32) as u64,
+        ],
+    );
     reinit_device(virtio_base, vqueue_phys);
     uart.write_str("k-os: VirtIO configured for storage\n");
 
-    map_shared_buffer(init_pt, storage_pt);
+    shared_buffer(uart, init_pid, storage_pid, SHARED_BUF_VA, SHARED_BUF_PAGES);
     uart.write_str("k-os: shared buffer mapped\n");
 }
 
-fn get_pt(pid: ProcessId) -> &'static mut mmu::PageTable {
-    let addr = kern().platform_mut().page_table_for(pid);
-    unsafe { &mut *(addr as *mut mmu::PageTable) }
-}
-
-fn map_virtio_mmio(pt: &mut mmu::PageTable, virtio_base: usize) {
-    mmu::map(pt, mmu::Mapping {
-        va: types::address::VirtualAddress::from_raw(VIRTIO_VA),
-        pa: types::address::PhysicalAddress::from_raw(virtio_base),
-        pages: 1,
-        flags: mmu::Sv39Flags::user_rw(),
-    });
-}
-
-fn alloc_and_map_virtqueue(pt: &mut mmu::PageTable) -> usize {
-    let phys = mmu::allocator::alloc_zeroed_page();
-    mmu::allocator::alloc_zeroed_page();
-    for i in 0..2usize {
-        mmu::map(pt, mmu::Mapping {
-            va: types::address::VirtualAddress::from_raw(VQUEUE_VA + i * 4096),
-            pa: types::address::PhysicalAddress::from_raw(phys + i * 4096),
-            pages: 1,
-            flags: mmu::Sv39Flags::user_rw(),
-        });
-    }
-    phys
-}
-
-fn alloc_and_map_reqhdr(pt: &mut mmu::PageTable) -> usize {
-    let phys = mmu::allocator::alloc_zeroed_page();
-    mmu::map(pt, mmu::Mapping {
-        va: types::address::VirtualAddress::from_raw(REQHDR_VA),
-        pa: types::address::PhysicalAddress::from_raw(phys),
-        pages: 1,
-        flags: mmu::Sv39Flags::user_rw(),
-    });
-    phys
-}
-
-fn write_phys_info(pt: &mut mmu::PageTable, reqhdr_phys: usize) {
-    let phys = mmu::allocator::alloc_zeroed_page();
-    mmu::map(pt, mmu::Mapping {
-        va: types::address::VirtualAddress::from_raw(PHYSINFO_VA),
-        pa: types::address::PhysicalAddress::from_raw(phys),
-        pages: 1,
-        flags: mmu::Sv39Flags::user_rw(),
-    });
-    unsafe {
-        let info = phys as *mut u64;
-        core::ptr::write_volatile(info, reqhdr_phys as u64);
-        core::ptr::write_volatile(info.add(1), (reqhdr_phys + 16) as u64);
-        core::ptr::write_volatile(info.add(2), (reqhdr_phys + 32) as u64);
-    }
-}
-
 fn reinit_device(base: usize, vqueue_phys: usize) {
-    let mmio = hw_virtio::mmio::DirectMmio::new(base);
+    let mmio = hw_virtio::mmio::DirectMmio::new(crate::mmu::phys_to_virt(base));
     hw_virtio::mmio::init_legacy_device(&mmio, vqueue_phys, hw_virtio::queue::QUEUE_SIZE as u32);
 }
-
-fn map_shared_buffer(init_pt: &mut mmu::PageTable, storage_pt: &mut mmu::PageTable) {
-    for i in 0..SHARED_BUF_PAGES {
-        let page = mmu::allocator::alloc_zeroed_page();
-        let va = SHARED_BUF_VA + i * 4096;
-        let mapping = mmu::Mapping {
-            va: types::address::VirtualAddress::from_raw(va),
-            pa: types::address::PhysicalAddress::from_raw(page),
-            pages: 1,
-            flags: mmu::Sv39Flags::user_rw(),
-        };
-        mmu::map(init_pt, mapping);
-        mmu::map(storage_pt, mmu::Mapping {
-            va: types::address::VirtualAddress::from_raw(va),
-            pa: types::address::PhysicalAddress::from_raw(page),
-            pages: 1,
-            flags: mmu::Sv39Flags::user_rw(),
-        });
-    }
-}

crates/adapter-riscv/src/hw/plic.rs

@@ -1,21 +1,37 @@
 use crate::board;
 
-const PLIC_PRIORITY: usize = board::PLIC_BASE;
-const PLIC_S_ENABLE: usize = board::PLIC_BASE + 0x2080;
-const PLIC_S_THRESHOLD: usize = board::PLIC_BASE + 0x201000;
-const PLIC_S_CLAIM: usize = board::PLIC_BASE + 0x201004;
+const PLIC: usize = crate::mmu::phys_to_virt(board::PLIC_BASE);
+const PLIC_PRIORITY: usize = PLIC;
+
+// External interrupts go to the boot hart only: its supervisor context is
+// 2 * hart + 1 on QEMU virt (even contexts are machine mode).
+fn context() -> usize {
+    2 * crate::smp::boot_hart() + 1
+}
+
+fn enable_base() -> usize {
+    PLIC + 0x2000 + context() * 0x80
+}
+
+fn threshold() -> usize {
+    PLIC + 0x20_0000 + context() * 0x1000
+}
+
+fn claim_reg() -> usize {
+    threshold() + 4
+}
 
 pub struct Plic;
 
 impl Plic {
     pub fn init() {
-        unsafe { core::ptr::write_volatile(PLIC_S_THRESHOLD as *mut u32, 0) };
+        unsafe { core::ptr::write_volatile(threshold() as *mut u32, 0) };
     }
 
     pub fn enable(irq: u32) {
         let word = (irq / 32) as usize;
         let bit = irq % 32;
-        let addr = PLIC_S_ENABLE + word * 4;
+        let addr = enable_base() + word * 4;
         unsafe {
             let current = core::ptr::read_volatile(addr as *const u32);
             core::ptr::write_volatile(addr as *mut u32, current | (1 << bit));
@@ -27,7 +43,7 @@ impl Plic {
     pub fn disable(irq: u32) {
         let word = (irq / 32) as usize;
         let bit = irq % 32;
-        let addr = PLIC_S_ENABLE + word * 4;
+        let addr = enable_base() + word * 4;
         unsafe {
             let current = core::ptr::read_volatile(addr as *const u32);
             core::ptr::write_volatile(addr as *mut u32, current & !(1 << bit));
@@ -35,10 +51,10 @@ impl Plic {
     }
 
     pub fn claim() -> u32 {
-        unsafe { core::ptr::read_volatile(PLIC_S_CLAIM as *const u32) }
+        unsafe { core::ptr::read_volatile(claim_reg() as *const u32) }
     }
 
     pub fn complete(irq: u32) {
-        unsafe { core::ptr::write_volatile(PLIC_S_CLAIM as *mut u32, irq) };
+        unsafe { core::ptr::write_volatile(claim_reg() as *mut u32, irq) };
     }
 }

crates/adapter-riscv/src/hw/timer.rs

@@ -7,10 +7,13 @@ pub fn read_time() -> u64 {
 }
 
 fn sbi_set_timer(stime: u64) {
+    // SBI returns an error code in a0 and a value in a1; both are
+    // clobbered even though we ignore them.
     unsafe {
         core::arch::asm!(
             "ecall",
-            in("a0") stime,
+            inlateout("a0") stime => _,
+            lateout("a1") _,
             in("a6") 0usize,
             in("a7") 0x54494D45usize,
         );

crates/adapter-riscv/src/hw/uart.rs

@@ -6,7 +6,9 @@ pub struct Uart {
 
 impl Uart {
     pub fn new() -> Self {
-        Self { base: board::UART_BASE }
+        Self {
+            base: crate::mmu::phys_to_virt(board::UART_BASE),
+        }
     }
 
     pub fn put_char(&self, byte: u8) {
@@ -30,7 +32,11 @@ impl Uart {
         let mut i = 0;
         while value > 0 {
             let digit = (value & 0xF) as u8;
-            buf[i] = if digit < 10 { b'0' + digit } else { b'a' + digit - 10 };
+            buf[i] = if digit < 10 {
+                b'0' + digit
+            } else {
+                b'a' + digit - 10
+            };
             value >>= 4;
             i += 1;
         }

crates/adapter-riscv/src/hw/virtio_blk.rs

@@ -1,6 +1,7 @@
-use hw_virtio::mmio::{self, DirectMmio};
-use hw_virtio::queue::{QueueAddrs, VirtioQueue, QUEUE_SIZE};
+use crate::mmu::{phys_to_virt, virt_to_phys};
 use hw_virtio::block::{self, DmaAddrs};
+use hw_virtio::mmio::{self, DirectMmio};
+use hw_virtio::queue::{QUEUE_SIZE, QueueAddrs, VirtioQueue};
 use types::address::{PhysicalAddress, VirtualAddress};
 
 const SECTOR_SIZE: usize = 512;
@@ -11,7 +12,11 @@ struct VirtqMem {
 }
 
 static mut VQUEUE: VirtqMem = VirtqMem { _data: [0; 8192] };
-static mut REQ_HEADER: block::BlockReqHeader = block::BlockReqHeader { req_type: 0, reserved: 0, sector: 0 };
+static mut REQ_HEADER: block::BlockReqHeader = block::BlockReqHeader {
+    req_type: 0,
+    reserved: 0,
+    sector: 0,
+};
 static mut REQ_STATUS: u8 = 0xFF;
 static mut SECTOR_BUF: [u8; SECTOR_SIZE] = [0; SECTOR_SIZE];
 
@@ -23,29 +28,38 @@ pub struct VirtioBlk {
 
 impl VirtioBlk {
     pub fn probe() -> Option<Self> {
-        let mmio = mmio::scan_for_device(mmio::DEVICE_ID_BLOCK)?;
+        let mmio = mmio::scan_for_device(phys_to_virt(mmio::MMIO_FIRST), mmio::DEVICE_ID_BLOCK)?;
 
-        let vq_phys = unsafe { core::ptr::addr_of!(VQUEUE) as usize };
-        mmio::init_legacy_device(&mmio, vq_phys, QUEUE_SIZE as u32);
+        // The device sees physical addresses; the CPU uses kernel ones.
+        let vq_va = core::ptr::addr_of!(VQUEUE) as usize;
+        mmio::init_legacy_device(&mmio, virt_to_phys(vq_va), QUEUE_SIZE as u32);
 
-        let queue = VirtioQueue::new(QueueAddrs::from_base(vq_phys));
+        let queue = VirtioQueue::new(QueueAddrs::from_base(vq_va));
 
-        let dma = unsafe {
-            DmaAddrs {
-                header_pa: PhysicalAddress::from_raw(core::ptr::addr_of!(REQ_HEADER) as usize),
-                header_va: VirtualAddress::from_raw(core::ptr::addr_of_mut!(REQ_HEADER) as usize),
-                status_pa: PhysicalAddress::from_raw(core::ptr::addr_of!(REQ_STATUS) as usize),
-                status_va: VirtualAddress::from_raw(core::ptr::addr_of_mut!(REQ_STATUS) as usize),
-                data_pa: PhysicalAddress::from_raw(core::ptr::addr_of!(SECTOR_BUF) as usize),
-                data_va: VirtualAddress::from_raw(core::ptr::addr_of_mut!(SECTOR_BUF) as usize),
-            }
+        let pair = |va: usize| {
+            (
+                PhysicalAddress::from_raw(virt_to_phys(va)),
+                VirtualAddress::from_raw(va),
+            )
+        };
+        let (header_pa, header_va) = pair(core::ptr::addr_of_mut!(REQ_HEADER) as usize);
+        let (status_pa, status_va) = pair(core::ptr::addr_of_mut!(REQ_STATUS) as usize);
+        let (data_pa, data_va) = pair(core::ptr::addr_of_mut!(SECTOR_BUF) as usize);
+        let dma = DmaAddrs {
+            header_pa,
+            header_va,
+            status_pa,
+            status_va,
+            data_pa,
+            data_va,
         };
 
         Some(Self { mmio, queue, dma })
     }
 
+    /// Physical address of the device's MMIO window.
     pub fn base(&self) -> usize {
-        self.mmio.base()
+        virt_to_phys(self.mmio.base())
     }
 
     pub fn read_sector(&mut self, sector: u32, buf: &mut [u8; SECTOR_SIZE]) -> bool {

crates/adapter-riscv/src/hw/virtio_gpu.rs

@@ -1,6 +1,7 @@
-use hw_virtio::mmio::{self, DirectMmio};
-use hw_virtio::queue::{QueueAddrs, VirtioQueue, QUEUE_SIZE};
+use crate::mmu::{phys_to_virt, virt_to_phys};
 use hw_virtio::gpu::{self, GpuDmaAddrs};
+use hw_virtio::mmio::{self, DirectMmio};
+use hw_virtio::queue::{QUEUE_SIZE, QueueAddrs, VirtioQueue};
 use types::address::{PhysicalAddress, VirtualAddress};
 use types::display::Dimension;
 
@@ -10,12 +11,13 @@ pub struct VirtioGpu {
 
 impl VirtioGpu {
     pub fn probe() -> Option<Self> {
-        let mmio = mmio::scan_for_device(mmio::DEVICE_ID_GPU)?;
+        let mmio = mmio::scan_for_device(phys_to_virt(mmio::MMIO_FIRST), mmio::DEVICE_ID_GPU)?;
         Some(Self { mmio })
     }
 
+    /// Physical address of the device's MMIO window.
     pub fn base(&self) -> usize {
-        self.mmio.base()
+        virt_to_phys(self.mmio.base())
     }
 
     pub fn mmio(&self) -> &DirectMmio {
@@ -26,15 +28,29 @@ impl VirtioGpu {
         mmio::init_legacy_device(&self.mmio, vqueue_phys, QUEUE_SIZE as u32);
     }
 
-    pub fn setup_framebuffer(&self, cmd_phys: usize, vq_phys: usize, fb_phys: usize, width: Dimension, height: Dimension) -> bool {
-        let queue = VirtioQueue::new(QueueAddrs::from_base(vq_phys));
+    pub fn setup_framebuffer(
+        &self,
+        cmd_phys: usize,
+        vq_phys: usize,
+        fb_phys: usize,
+        width: Dimension,
+        height: Dimension,
+    ) -> bool {
+        let queue = VirtioQueue::new(QueueAddrs::from_base(phys_to_virt(vq_phys)));
         let dma = GpuDmaAddrs {
             cmd_pa: PhysicalAddress::from_raw(cmd_phys),
-            cmd_va: VirtualAddress::from_raw(cmd_phys),
+            cmd_va: VirtualAddress::from_raw(phys_to_virt(cmd_phys)),
             resp_pa: PhysicalAddress::from_raw(cmd_phys + 512),
         };
         let ok1 = gpu::create_2d(&self.mmio, &queue, &dma, 1, width, height);
-        let ok2 = gpu::attach_backing(&self.mmio, &queue, &dma, 1, PhysicalAddress::from_raw(fb_phys), width.raw() as u32 * height.raw() as u32 * 4);
+        let ok2 = gpu::attach_backing(
+            &self.mmio,
+            &queue,
+            &dma,
+            1,
+            PhysicalAddress::from_raw(fb_phys),
+            width.raw() as u32 * height.raw() as u32 * 4,
+        );
         let ok3 = gpu::set_scanout(&self.mmio, &queue, &dma, 0, 1, width, height);
         ok1 && ok2 && ok3
     }

crates/adapter-riscv/src/kernel_cell.rs

@@ -18,8 +18,13 @@ impl<T> KernelCell<T> {
         }
     }
 
-    pub fn init(&self, value: T) {
-        unsafe { (*self.inner.get()).write(value) };
+    /// Initializes the cell by letting `build` write the value straight
+    /// into its storage, so a large `T` never lives on the stack.
+    ///
+    /// # Safety
+    /// `build` must fully initialize the `T` behind the pointer.
+    pub unsafe fn init_with(&self, build: impl FnOnce(*mut T)) {
+        build(unsafe { (*self.inner.get()).as_mut_ptr() });
         self.initialized.store(true, Ordering::Release);
     }
 

crates/adapter-riscv/src/main.rs

@@ -9,6 +9,7 @@ mod hw;
 mod kernel_cell;
 mod mmu;
 mod platform;
+mod smp;
 mod trap;
 
 use core::arch::global_asm;
@@ -17,55 +18,168 @@ use kernel_cell::KernelCell;
 
 static KERNEL: KernelCell<kernel::Kernel<platform::RiscVPlatform>> = KernelCell::uninit();
 
+fn kern_mut() -> &'static mut kernel::Kernel<platform::RiscVPlatform> {
+    // SAFETY: boot runs with the kernel lock held and before any other
+    // hart has started.
+    unsafe { &mut *kernel_ptr() }
+}
+
 pub fn kernel_ptr() -> *mut kernel::Kernel<platform::RiscVPlatform> {
     KERNEL.as_ptr()
 }
 
+// Firmware enters `_start` (and SBI starts other harts at
+// `_secondary_start`) at the physical load address with the MMU off and
+// the hart id in a0, but the kernel is linked in the upper half. Using
+// only PC-relative code, the stub turns on `boot_page_table`, which maps
+// RAM twice (at its physical address, just so the next instruction still
+// exists, and in the upper half) plus the MMIO window high, then jumps to
+// its own high address and takes the hart's kernel stack. The kernel then
+// switches every hart to the real table, which maps nothing low.
 global_asm!(
     r#"
 .section .text.entry
 .globl _start
 _start:
-    la sp, _stack_top
+    lla t2, start_high_address
+    j 1f
+.globl _secondary_start
+_secondary_start:
+    lla t2, secondary_high_address
+1:
+    li t0, 8                # smp::MAX_HARTS
+    bgeu a0, t0, spin
+    mv s0, a0
+    lla t0, boot_page_table
+    srli t0, t0, 12
+    li t1, 8 << 60
+    or t0, t0, t1
+    csrw satp, t0
+    sfence.vma
+    ld t0, 0(t2)
+    jr t0
+
+# sp = _stacks_start + (hart + 1) * smp::STACK_SLOT
+start_high:
+    call hart_stack
+    mv a0, s0
     call kmain
+    j spin
+secondary_high:
+    call hart_stack
+    mv a0, s0
+    call kmain_secondary
+    j spin
+hart_stack:
+    lla sp, _stacks_start
+    addi t0, s0, 1
+    li t1, 0x81000
+    mul t0, t0, t1
+    add sp, sp, t0
+    ret
 spin:
     wfi
     j spin
+
+.pushsection .rodata
+.balign 8
+start_high_address:
+    .quad start_high
+secondary_high_address:
+    .quad secondary_high
+.popsection
+
+# Sv39 root of 1 GiB leaves; an entry is (PA >> 12) << 10 | flags, with
+# flags V|R|W|A|D = 0xc7, plus X = 0xcf.
+.pushsection .data
+.balign 4096
+boot_page_table:
+    .quad 0
+    .quad 0
+    .quad 0x200000cf    # [2]   0x8000_0000 -> RAM, for the jump only
+    .fill 253, 8, 0
+    .quad 0x000000c7    # [256] PHYS_OFFSET + 0 -> MMIO
+    .quad 0
+    .quad 0x200000cf    # [258] PHYS_OFFSET + 0x8000_0000 -> RAM
+    .fill 253, 8, 0
+.popsection
 "#
 );
 
 const SHARED_BUF_VA: usize = 0x30000;
 
 #[unsafe(no_mangle)]
-extern "C" fn kmain() -> ! {
+extern "C" fn kmain(hart: usize) -> ! {
     let uart = Uart::new();
     uart.write_str("k-os: booted on RISC-V\n");
 
-    let kernel_pt = boot::hardware::init(&uart);
-    let mut blk = boot::hardware::probe_block_device(&uart)
-        .unwrap_or_else(|| halt(&uart, "no block device"));
+    boot::hardware::init(&uart, hart);
+    // Held until the boot hart first enters userspace; harts started
+    // below wait for it. Not before init: zeroing .bss resets the lock.
+    smp::lock();
+    let mut blk =
+        boot::hardware::probe_block_device(&uart).unwrap_or_else(|| halt(&uart, "no block device"));
 
-    let (init, _) = boot::loader::load_init(&uart, &mut blk, kernel_pt);
-    let storage = boot::loader::load_server(&uart, &mut blk, kernel_pt, b"storage.elf", "storage");
-    let display = boot::loader::load_server(&uart, &mut blk, kernel_pt, b"display.elf", "display");
-    let input = boot::loader::load_server(&uart, &mut blk, kernel_pt, b"input.elf", "input");
+    let (init, init_thread) = boot::loader::load_init(&uart, &mut blk);
+    if let Some(ctx) = kern_mut().thread_context_mut(init_thread) {
+        ctx.registers_mut()[10] = SHARED_BUF_VA;
+    }
+    let storage = boot::loader::load_server(&uart, &mut blk, b"storage.elf", "storage");
+    let display = boot::loader::load_server(&uart, &mut blk, b"display.elf", "display");
+    let input = boot::loader::load_server(&uart, &mut blk, b"input.elf", "input");
     let virtio_base = blk.base();
-    drop(blk);
 
+    let board = board::devices().unwrap_or_else(|| halt(&uart, "bad board table"));
+    kern_mut()
+        .register_board(init.pid, &board)
+        .unwrap_or_else(|_| halt(&uart, "board registration failed"));
     devices::storage_setup::configure(&uart, init.pid, storage.pid, virtio_base);
     devices::gpu_setup::configure(&uart, display.pid);
     devices::input_setup::configure(&uart, input.pid);
     boot::caps::grant_all(&uart, init.pid, storage.pid, display.pid, input.pid);
+    // After grant_all, so the slots init already relies on stay put.
+    kern_mut()
+        .grant_boot_authority(init.pid, &board)
+        .unwrap_or_else(|_| halt(&uart, "boot authority failed"));
 
+    start_other_harts(&uart, hart);
     uart.write_str("k-os: entering userspace\n");
-    boot::loader::enter_userspace(init.pid, init.entry, SHARED_BUF_VA);
+    trap::enter_first();
+}
+
+fn start_other_harts(uart: &Uart, boot: usize) {
+    unsafe extern "C" {
+        fn _secondary_start();
+    }
+    // Harts start with the MMU off, so at the entry's physical address.
+    let entry = mmu::virt_to_phys(_secondary_start as *const () as usize);
+    for hart in (0..smp::num_harts()).filter(|h| *h != boot) {
+        if !smp::sbi_hart_start(hart, entry) {
+            halt(uart, "could not start a hart");
+        }
+    }
+    uart.write_str("k-os: ");
+    uart.write_dec(smp::num_harts());
+    uart.write_str(" harts\n");
+}
+
+/// Where every hart but the boot hart starts, on its own stack.
+#[unsafe(no_mangle)]
+extern "C" fn kmain_secondary(_hart: usize) -> ! {
+    trap::init();
+    hw::timer::init();
+    mmu::activate(mmu::page_table::table_at(smp::kernel_root()));
+    smp::lock();
+    trap::enter_first();
 }
 
 pub fn halt(uart: &Uart, msg: &str) -> ! {
     uart.write_str("k-os: FATAL — ");
     uart.write_str(msg);
     uart.put_char(b'\n');
-    loop { unsafe { core::arch::asm!("wfi") }; }
+    loop {
+        unsafe { core::arch::asm!("wfi") };
+    }
 }
 
 #[panic_handler]
@@ -78,5 +192,7 @@ fn panic(info: &core::panic::PanicInfo) -> ! {
         uart.write_dec(location.line() as usize);
     }
     uart.put_char(b'\n');
-    loop { unsafe { core::arch::asm!("wfi") }; }
+    loop {
+        unsafe { core::arch::asm!("wfi") };
+    }
 }

crates/adapter-riscv/src/mmu/allocator.rs

@@ -1,16 +1,23 @@
-use super::page_table::{PageTable, PAGE_SIZE};
+use super::page_table::{PAGE_SIZE, PageTable};
+use crate::board;
 
-// Boot-time bump allocator for page tables.
-// Only used during init before the scheduler starts.
+// Boot-time bump allocator for kernel-only memory: the kernel page table
+// and boot scratch buffers. User memory and user page tables come from the
+// kernel's frame table instead. It must never reach the user pool.
 static mut NEXT_FREE: usize = 0;
 
 pub fn init_allocator(start: usize) {
-    unsafe { NEXT_FREE = start; }
+    unsafe {
+        NEXT_FREE = start;
+    }
 }
 
 pub fn alloc_zeroed_page() -> usize {
     unsafe {
         let addr = NEXT_FREE;
+        if addr + PAGE_SIZE > super::phys_to_virt(board::USER_POOL_BASE) {
+            crate::halt(&crate::hw::uart::Uart::new(), "boot allocator exhausted");
+        }
         NEXT_FREE += PAGE_SIZE;
         core::ptr::write_bytes(addr as *mut u8, 0, PAGE_SIZE);
         addr
@@ -18,9 +25,5 @@ pub fn alloc_zeroed_page() -> usize {
 }
 
 pub fn alloc_page_table() -> &'static mut PageTable {
-    unsafe {
-        let addr = alloc_zeroed_page();
-        let table = &mut *(addr as *mut PageTable);
-        table
-    }
+    unsafe { &mut *(alloc_zeroed_page() as *mut PageTable) }
 }

crates/adapter-riscv/src/mmu/mod.rs

@@ -2,4 +2,24 @@ pub mod allocator;
 pub mod page_table;
 
 pub use allocator::init_allocator;
-pub use page_table::{activate, init_kernel_page_table, create_user_page_table, map, translate, Sv39Flags, Mapping, PageTable, PAGE_SIZE};
+pub use page_table::{
+    PAGE_SIZE, PageTable, Sv39Flags, USER_VA_END, USER_VA_START, activate, active_root, check_wx,
+    create_user_root, init_kernel_page_table, map_user_page, unmap_user_page,
+};
+
+/// The kernel lives in the upper half of the address space: all of RAM and
+/// the MMIO windows appear at their physical address plus this offset (the
+/// start of Sv39's upper half), and the kernel image is linked there too,
+/// so one offset converts any kernel address. Must match linker.ld.
+pub const PHYS_OFFSET: usize = 0xFFFF_FFC0_0000_0000;
+
+/// Where the kernel sees physical address `pa`.
+pub const fn phys_to_virt(pa: usize) -> usize {
+    pa + PHYS_OFFSET
+}
+
+/// The physical address behind kernel address `va` (a static, the boot
+/// heap, a page table). Only valid for addresses in the direct map.
+pub const fn virt_to_phys(va: usize) -> usize {
+    va - PHYS_OFFSET
+}

crates/adapter-riscv/src/mmu/page_table.rs

@@ -1,6 +1,10 @@
-use crate::board;
 use super::allocator::alloc_page_table;
+use super::{phys_to_virt, virt_to_phys};
+use crate::board;
+use crate::smp;
+use platform::{FrameSource, MapError};
 use types::address::{PhysicalAddress, VirtualAddress};
+use types::mapping::PagePerms;
 
 pub use types::mapping::Mapping;
 pub const PAGE_SIZE: usize = 4096;
@@ -20,27 +24,30 @@ pub struct Sv39Flags {
 }
 
 impl Sv39Flags {
-    pub fn kernel_rwx() -> Self {
-        Self { bits: PTE_R | PTE_W | PTE_X | PTE_G }
+    pub fn kernel_rx() -> Self {
+        Self {
+            bits: PTE_R | PTE_X | PTE_G,
+        }
+    }
+
+    pub fn kernel_ro() -> Self {
+        Self {
+            bits: PTE_R | PTE_G,
+        }
     }
 
     pub fn kernel_rw() -> Self {
-        Self { bits: PTE_R | PTE_W | PTE_G }
+        Self {
+            bits: PTE_R | PTE_W | PTE_G,
+        }
     }
 
-    pub fn user_rx() -> Self {
-        Self { bits: PTE_R | PTE_X | PTE_U }
-    }
-
-    pub fn user_rw() -> Self {
-        Self { bits: PTE_R | PTE_W | PTE_U }
-    }
-
-    pub fn user(read: bool, write: bool, exec: bool) -> Self {
-        let mut bits = PTE_U;
-        if read { bits |= PTE_R; }
-        if write { bits |= PTE_W; }
-        if exec { bits |= PTE_X; }
+    pub fn user(perms: PagePerms) -> Self {
+        let bits = match perms {
+            PagePerms::ReadOnly => PTE_R | PTE_U,
+            PagePerms::ReadWrite => PTE_R | PTE_W | PTE_U,
+            PagePerms::ReadExecute => PTE_R | PTE_X | PTE_U,
+        };
         Self { bits }
     }
 
@@ -92,81 +99,223 @@ fn vpn(va: usize, level: usize) -> usize {
     (va >> (12 + 9 * level)) & 0x1FF
 }
 
-pub fn translate(root: &PageTable, va: usize) -> Option<usize> {
-    let vpn2 = vpn(va, 2);
-    if !root.entries[vpn2].is_valid() { return None; }
-    let l1 = unsafe { &*((root.entries[vpn2].ppn() << 12) as *const PageTable) };
-
-    let vpn1 = vpn(va, 1);
-    if !l1.entries[vpn1].is_valid() { return None; }
-    let l0 = unsafe { &*((l1.entries[vpn1].ppn() << 12) as *const PageTable) };
-
-    let vpn0 = vpn(va, 0);
-    if !l0.entries[vpn0].is_valid() { return None; }
-    let pa = (l0.entries[vpn0].ppn() << 12) as usize | (va & 0xFFF);
-    Some(pa)
-}
-
 fn map_page(root: &mut PageTable, va: usize, pa: usize, flags: Sv39Flags) {
     let vpn2 = vpn(va, 2);
     let vpn1 = vpn(va, 1);
     let vpn0 = vpn(va, 0);
 
     if !root.entries[vpn2].is_valid() {
-        let table = alloc_page_table();
-        let ppn = (table as *const PageTable as u64) >> 12;
-        root.entries[vpn2] = PageTableEntry::new_branch(ppn);
+        root.entries[vpn2] = PageTableEntry::new_branch(table_ppn(alloc_page_table()));
     }
-
-    let l1_addr = (root.entries[vpn2].ppn() << 12) as *mut PageTable;
-    let l1 = unsafe { &mut *l1_addr };
+    let l1 = table_at((root.entries[vpn2].ppn() << 12) as usize);
 
     if !l1.entries[vpn1].is_valid() {
-        let table = alloc_page_table();
-        let ppn = (table as *const PageTable as u64) >> 12;
-        l1.entries[vpn1] = PageTableEntry::new_branch(ppn);
+        l1.entries[vpn1] = PageTableEntry::new_branch(table_ppn(alloc_page_table()));
     }
-
-    let l0_addr = (l1.entries[vpn1].ppn() << 12) as *mut PageTable;
-    let l0 = unsafe { &mut *l0_addr };
+    let l0 = table_at((l1.entries[vpn1].ppn() << 12) as usize);
 
     let ppn = (pa as u64) >> 12;
     l0.entries[vpn0] = PageTableEntry::new_leaf(ppn, flags);
 }
 
+/// The physical page number of a page table the kernel holds a reference to.
+fn table_ppn(table: &PageTable) -> u64 {
+    (virt_to_phys(table as *const PageTable as usize) as u64) >> 12
+}
+
 pub fn map(root: &mut PageTable, mapping: Mapping<Sv39Flags>) {
     for i in 0..mapping.pages {
         let offset = i * PAGE_SIZE;
-        map_page(root, mapping.va.raw() + offset, mapping.pa.raw() + offset, mapping.flags);
+        map_page(
+            root,
+            mapping.va.raw() + offset,
+            mapping.pa.raw() + offset,
+            mapping.flags,
+        );
     }
 }
 
 pub fn init_kernel_page_table() -> &'static mut PageTable {
     let root = alloc_page_table();
 
-    let identity = |addr: usize| (VirtualAddress::from_raw(addr), PhysicalAddress::from_raw(addr));
+    // Physical `pa` at its place in the upper-half direct map.
+    let direct = |pa: usize| {
+        (
+            VirtualAddress::from_raw(phys_to_virt(pa)),
+            PhysicalAddress::from_raw(pa),
+        )
+    };
 
-    let (va, pa) = identity(board::RAM_BASE);
-    map(root, Mapping { va, pa, pages: board::RAM_SIZE / PAGE_SIZE, flags: Sv39Flags::kernel_rwx() });
+    // The kernel image, then the rest of RAM, each with only the access it
+    // needs: code is never writable, data never executable. RAM below the
+    // image belongs to the firmware and stays unmapped, as does the guard
+    // page under each hart's kernel stack. Nothing is mapped in the lower
+    // half, which is userspace's alone.
+    let layout = KernelLayout::from_linker();
+    let ram_end = phys_to_virt(board::RAM_BASE + board::RAM_SIZE);
+    let stacks = (0..smp::MAX_HARTS).map(|h| {
+        let slot = layout.stacks_start + h * smp::STACK_SLOT;
+        (
+            slot + PAGE_SIZE,
+            slot + smp::STACK_SLOT,
+            Sv39Flags::kernel_rw(),
+        )
+    });
+    for (start, end, flags) in [
+        (layout.text_start, layout.text_end, Sv39Flags::kernel_rx()),
+        (layout.text_end, layout.rodata_end, Sv39Flags::kernel_ro()),
+        (
+            layout.rodata_end,
+            layout.stacks_start,
+            Sv39Flags::kernel_rw(),
+        ),
+        (layout.stacks_end, ram_end, Sv39Flags::kernel_rw()),
+    ]
+    .into_iter()
+    .chain(stacks)
+    {
+        let (va, pa) = direct(virt_to_phys(start));
+        map(
+            root,
+            Mapping {
+                va,
+                pa,
+                pages: (end - start) / PAGE_SIZE,
+                flags,
+            },
+        );
+    }
 
-    let (va, pa) = identity(board::UART_BASE);
-    map(root, Mapping { va, pa, pages: 1, flags: Sv39Flags::kernel_rw() });
-
-    let (va, pa) = identity(board::PLIC_BASE);
-    map(root, Mapping { va, pa, pages: 0x400000 / PAGE_SIZE, flags: Sv39Flags::kernel_rw() });
-
-    let (va, pa) = identity(board::CLINT_BASE);
-    map(root, Mapping { va, pa, pages: 0x10000 / PAGE_SIZE, flags: Sv39Flags::kernel_rw() });
-
-    let (va, pa) = identity(board::VIRTIO_BASE);
-    map(root, Mapping { va, pa, pages: board::VIRTIO_SIZE / PAGE_SIZE, flags: Sv39Flags::kernel_rw() });
+    for (base, size) in [
+        (board::UART_BASE, PAGE_SIZE),
+        (board::PLIC_BASE, 0x40_0000),
+        (board::CLINT_BASE, 0x1_0000),
+        (board::VIRTIO_BASE, board::VIRTIO_SIZE),
+    ] {
+        let (va, pa) = direct(base);
+        map(
+            root,
+            Mapping {
+                va,
+                pa,
+                pages: size / PAGE_SIZE,
+                flags: Sv39Flags::kernel_rw(),
+            },
+        );
+    }
 
     root
 }
 
+/// Page-aligned boundaries of the kernel image, from linker.ld.
+pub struct KernelLayout {
+    pub text_start: usize,
+    pub text_end: usize,
+    pub rodata_end: usize,
+    pub stacks_start: usize,
+    pub stacks_end: usize,
+}
+
+impl KernelLayout {
+    pub fn from_linker() -> Self {
+        unsafe extern "C" {
+            static _text_start: u8;
+            static _text_end: u8;
+            static _rodata_end: u8;
+            static _stacks_start: u8;
+            static _stacks_end: u8;
+        }
+        // SAFETY: only the symbols' addresses are taken, never their values.
+        unsafe {
+            Self {
+                text_start: &_text_start as *const u8 as usize,
+                text_end: &_text_end as *const u8 as usize,
+                rodata_end: &_rodata_end as *const u8 as usize,
+                stacks_start: &_stacks_start as *const u8 as usize,
+                stacks_end: &_stacks_end as *const u8 as usize,
+            }
+        }
+    }
+}
+
+/// What `check_wx` found wrong with a kernel page table, if anything.
+pub enum WxViolation {
+    /// A page that is both writable and executable.
+    WritableCode(usize),
+    /// An executable page outside the kernel's text.
+    ExecutableData(usize),
+    /// A mapped page under the firmware, or the stack guard.
+    MappedHole(usize),
+    /// A kernel mapping in the lower half, which belongs to userspace.
+    LowerHalf(usize),
+}
+
+/// Walks every leaf of `root` and checks the kernel layout: nothing is
+/// both writable and executable, only kernel text is executable, the
+/// firmware and every stack guard are unmapped, and nothing at all is mapped
+/// in the lower half. Returns the number of executable pages.
+pub fn check_wx(root: &PageTable) -> Result<usize, WxViolation> {
+    let layout = KernelLayout::from_linker();
+    let text = layout.text_start..layout.text_end;
+    let is_guard = |va: usize| {
+        (layout.stacks_start..layout.stacks_end).contains(&va)
+            && (va - layout.stacks_start).is_multiple_of(smp::STACK_SLOT)
+    };
+    let firmware = phys_to_virt(board::RAM_BASE)..layout.text_start;
+    let mut executable = 0;
+    for (va, bits) in leaves(root) {
+        if va < phys_to_virt(0) {
+            return Err(WxViolation::LowerHalf(va));
+        }
+        if bits & PTE_W != 0 && bits & PTE_X != 0 {
+            return Err(WxViolation::WritableCode(va));
+        }
+        if bits & PTE_X != 0 {
+            if !text.contains(&va) {
+                return Err(WxViolation::ExecutableData(va));
+            }
+            executable += 1;
+        }
+        if is_guard(va) || firmware.contains(&va) {
+            return Err(WxViolation::MappedHole(va));
+        }
+    }
+    Ok(executable)
+}
+
+/// Every 4 KiB leaf in `root` as (virtual address, PTE flag bits).
+/// The kernel maps nothing larger.
+fn leaves(root: &PageTable) -> impl Iterator<Item = (usize, u64)> + '_ {
+    let next = |e: &PageTableEntry| table_at((e.ppn() << 12) as usize) as &PageTable;
+    root.entries
+        .iter()
+        .enumerate()
+        .filter(|(_, e)| e.is_valid())
+        .flat_map(move |(i2, e2)| {
+            next(e2)
+                .entries
+                .iter()
+                .enumerate()
+                .filter(|(_, e)| e.is_valid())
+                .flat_map(move |(i1, e1)| {
+                    next(e1)
+                        .entries
+                        .iter()
+                        .enumerate()
+                        .filter(|(_, e)| e.is_valid())
+                        .map(move |(i0, e0)| {
+                            let va = (i2 << 30) | (i1 << 21) | (i0 << 12);
+                            // Sv39 addresses are sign extended from bit 38.
+                            let va = if i2 >= 256 { va | !((1 << 39) - 1) } else { va };
+                            (va, e0.0 & 0x3ff)
+                        })
+                })
+        })
+}
+
 pub fn activate(root: &PageTable) {
-    let ppn = (root as *const PageTable as u64) >> 12;
-    let satp = (8u64 << 60) | ppn;
+    smp::note_active_root(virt_to_phys(root as *const PageTable as usize));
+    let satp = (8u64 << 60) | table_ppn(root);
     unsafe {
         core::arch::asm!(
             "csrw satp, {0}",
@@ -176,34 +325,105 @@ pub fn activate(root: &PageTable) {
     }
 }
 
-pub fn create_user_page_table(
+// ---- user address spaces ----
+//
+// User mappings live in [USER_VA_START, USER_VA_END), which is root slot 0,
+// the L1 slots below USER_VA_END. Every address space gets its own root and its
+// own L1 for slot 0, and the kernel maps nothing in the lower half, so all
+// page tables below the user window are private to one process. The
+// kernel's upper-half entries are shared by copying them.
+
+pub const USER_VA_START: usize = 0x1000;
+pub const USER_VA_END: usize = 0x0200_0000;
+
+/// The page table at physical address `pa`, through the direct map.
+pub fn table_at(pa: usize) -> &'static mut PageTable {
+    // SAFETY: every page table lives in RAM, which the kernel maps at
+    // `phys_to_virt`.
+    unsafe { &mut *(phys_to_virt(pa) as *mut PageTable) }
+}
+
+fn fresh_table(frames: &mut dyn FrameSource) -> Result<usize, MapError> {
+    let pa = frames
+        .alloc_table_frame()
+        .ok_or(MapError::OutOfFrames)?
+        .raw();
+    table_at(pa).zero();
+    Ok(pa)
+}
+
+fn in_user_window(va: usize) -> bool {
+    va.is_multiple_of(PAGE_SIZE) && (USER_VA_START..USER_VA_END).contains(&va)
+}
+
+/// Builds a root table sharing the kernel's mappings, with a private L1 for
+/// the user window. Returns the root's physical address.
+pub fn create_user_root(
     kernel_root: &PageTable,
-    _program_pa: PhysicalAddress,
-    _program_pages: usize,
-    _user_va: VirtualAddress,
-) -> &'static mut PageTable {
-    let root = alloc_page_table();
+    frames: &mut dyn FrameSource,
+) -> Result<usize, MapError> {
+    let root_pa = fresh_table(frames)?;
+    let l1_pa = fresh_table(frames)?;
+    let root = table_at(root_pa);
 
-    for i in 0..512 {
-        if !kernel_root.entries[i].is_valid() {
-            continue;
+    for (mine, kernels) in root.entries.iter_mut().zip(&kernel_root.entries).skip(256) {
+        *mine = *kernels;
     }
-        if i == 0 {
-            // User mappings land in VPN[2]=0 — each process needs its own L1
-            let kernel_l1_addr = (kernel_root.entries[i].ppn() << 12) as *const PageTable;
-            let kernel_l1 = unsafe { &*kernel_l1_addr };
-            let new_l1 = alloc_page_table();
-            for j in 0..512 {
-                if kernel_l1.entries[j].is_valid() {
-                    new_l1.entries[j] = kernel_l1.entries[j];
+    root.entries[0] = PageTableEntry::new_branch((l1_pa as u64) >> 12);
+    Ok(root_pa)
 }
+
+fn user_leaf_table(
+    root_pa: usize,
+    va: usize,
+    frames: Option<&mut dyn FrameSource>,
+) -> Result<&'static mut PageTable, MapError> {
+    let root = table_at(root_pa);
+    let l1 = table_at((root.entries[0].ppn() << 12) as usize);
+    let slot = &mut l1.entries[vpn(va, 1)];
+    if !slot.is_valid() {
+        let frames = frames.ok_or(MapError::NoAddressSpace)?;
+        let l0_pa = fresh_table(frames)?;
+        *slot = PageTableEntry::new_branch((l0_pa as u64) >> 12);
     }
-            let ppn = (new_l1 as *const PageTable as u64) >> 12;
-            root.entries[i] = PageTableEntry::new_branch(ppn);
-        } else {
-            root.entries[i] = kernel_root.entries[i];
+    Ok(table_at((slot.ppn() << 12) as usize))
+}
+
+pub fn map_user_page(
+    root_pa: usize,
+    va: usize,
+    pa: usize,
+    flags: Sv39Flags,
+    frames: &mut dyn FrameSource,
+) -> Result<(), MapError> {
+    if !in_user_window(va) || !pa.is_multiple_of(PAGE_SIZE) {
+        return Err(MapError::InvalidAddress);
+    }
+    let l0 = user_leaf_table(root_pa, va, Some(frames))?;
+    l0.entries[vpn(va, 0)] = PageTableEntry::new_leaf((pa as u64) >> 12, flags);
+    flush_tlb(va);
+    Ok(())
+}
+
+pub fn unmap_user_page(root_pa: usize, va: usize) {
+    if !in_user_window(va) {
+        return;
+    }
+    if let Ok(l0) = user_leaf_table(root_pa, va, None) {
+        l0.entries[vpn(va, 0)] = PageTableEntry::empty();
+        flush_tlb(va);
     }
 }
 
-    root
+fn flush_tlb(va: usize) {
+    // SAFETY: sfence.vma only invalidates translation caches.
+    unsafe { core::arch::asm!("sfence.vma {0}, zero", in(reg) va) };
+}
+
+/// Physical address of the root table the hart is translating with.
+pub fn active_root() -> usize {
+    let satp: usize;
+    // SAFETY: reading satp has no side effects.
+    unsafe { core::arch::asm!("csrr {0}, satp", out(reg) satp) };
+    (satp & ((1 << 44) - 1)) << 12
 }

crates/adapter-riscv/src/platform.rs

@@ -1,29 +1,29 @@
-use domain::memory::MemoryRegion;
 use domain::process::MAX_PROCESSES;
-use platform::Platform;
+use platform::{FrameSource, MapError, Platform};
 use types::{
     address::{EntryPoint, PhysicalAddress, StackPointer, VirtualAddress},
-    bounded::PageCount,
     id::{CoreId, IrqId, ProcessId},
-    permission::{Permission, PermissionSet},
+    mapping::PagePerms,
     time::{Ticks, TimerDuration},
 };
 
 use crate::board;
 use crate::hw::{plic::Plic, timer};
 use crate::mmu;
+use crate::smp;
 use crate::trap;
 
 pub struct RiscVPlatform {
     num_cores: u8,
     kernel_pt: usize,
+    /// Root table of each process's address space, 0 if it has none.
     page_tables: [usize; MAX_PROCESSES],
 }
 
 impl RiscVPlatform {
-    pub fn new(kernel_pt_addr: usize) -> Self {
+    pub fn new(kernel_pt_addr: usize, num_cores: u8) -> Self {
         Self {
-            num_cores: 1,
+            num_cores,
             kernel_pt: kernel_pt_addr,
             page_tables: [0usize; MAX_PROCESSES],
         }
@@ -33,37 +33,82 @@ impl RiscVPlatform {
         self.page_tables[pid.raw() as usize]
     }
 
-    pub fn set_page_table(&mut self, pid: ProcessId, addr: usize) {
-        self.page_tables[pid.raw() as usize] = addr;
+    fn root(&self, pid: ProcessId) -> Option<usize> {
+        match self.page_tables.get(pid.raw() as usize) {
+            Some(&0) | None => None,
+            Some(&root) => Some(root),
         }
-
-    fn ensure_page_table(&mut self, pid: ProcessId) -> &mut mmu::PageTable {
-        let idx = pid.raw() as usize;
-        if self.page_tables[idx] == 0 {
-            let kernel_pt = unsafe { &*(self.kernel_pt as *const mmu::PageTable) };
-            let user_pt = mmu::create_user_page_table(
-                kernel_pt,
-                PhysicalAddress::from_raw(0),
-                0,
-                VirtualAddress::from_raw(0x10000),
-            );
-            self.page_tables[idx] = user_pt as *const mmu::PageTable as usize;
-        }
-        unsafe { &mut *(self.page_tables[idx] as *mut mmu::PageTable) }
     }
 }
 
 impl Platform for RiscVPlatform {
-    fn configure_protection(&mut self, process: ProcessId, regions: &[MemoryRegion]) {
-        let pt = self.ensure_page_table(process);
-        for region in regions {
-            mmu::map(pt, mmu::Mapping {
-                va: VirtualAddress::from_raw(region.base().raw()),
-                pa: region.base(),
-                pages: region.size().value() as usize,
-                flags: mmu::Sv39Flags::user(true, true, true),
-            });
+    const USER_VA_START: usize = mmu::USER_VA_START;
+    const USER_VA_END: usize = mmu::USER_VA_END;
+
+    fn create_address_space(
+        &mut self,
+        process: ProcessId,
+        frames: &mut dyn FrameSource,
+    ) -> Result<(), MapError> {
+        let slot = self
+            .page_tables
+            .get_mut(process.raw() as usize)
+            .ok_or(MapError::NoAddressSpace)?;
+        // SAFETY: the kernel page table lives in the boot heap forever.
+        let kernel_root = unsafe { &*(self.kernel_pt as *const mmu::PageTable) };
+        *slot = mmu::create_user_root(kernel_root, frames)?;
+        Ok(())
     }
+
+    fn destroy_address_space(&mut self, process: ProcessId) {
+        let Some(root) = self.root(process) else {
+            return;
+        };
+        // No hart may still translate through it once the kernel frees its
+        // frames: other harts leave it (and wait for nothing but that), and
+        // the caller may be tearing down the space we are running on.
+        smp::shoot_down(root);
+        if mmu::active_root() == root {
+            // SAFETY: the kernel page table lives in the boot heap forever.
+            mmu::activate(unsafe { &*(self.kernel_pt as *const mmu::PageTable) });
+        }
+        self.page_tables[process.raw() as usize] = 0;
+        // SAFETY: flushing translations has no other effect.
+        unsafe { core::arch::asm!("sfence.vma zero, zero") };
+    }
+
+    fn map_page(
+        &mut self,
+        process: ProcessId,
+        va: VirtualAddress,
+        pa: PhysicalAddress,
+        perms: PagePerms,
+        frames: &mut dyn FrameSource,
+    ) -> Result<(), MapError> {
+        let root = self.root(process).ok_or(MapError::NoAddressSpace)?;
+        mmu::map_user_page(
+            root,
+            va.raw(),
+            pa.raw(),
+            mmu::Sv39Flags::user(perms),
+            frames,
+        )
+    }
+
+    fn unmap_page(&mut self, process: ProcessId, va: VirtualAddress) {
+        if let Some(root) = self.root(process) {
+            mmu::unmap_user_page(root, va.raw());
+            // Other harts running this process may still cache it.
+            smp::shoot_down(root);
+        }
+    }
+
+    fn zero_frame(&mut self, pa: PhysicalAddress) {
+        // SAFETY: pool frames are RAM, mapped at `phys_to_virt`, and the
+        // kernel only zeroes frames it has just allocated.
+        unsafe {
+            core::ptr::write_bytes(mmu::phys_to_virt(pa.raw()) as *mut u8, 0, mmu::PAGE_SIZE)
+        };
     }
 
     fn enable_user_mode(&mut self, entry: EntryPoint, stack: StackPointer) -> ! {
@@ -104,68 +149,34 @@ impl Platform for RiscVPlatform {
         Plic::enable(irq.raw() as u32);
     }
 
-    fn send_ipi(&mut self, _target: CoreId) {}
+    fn send_ipi(&mut self, target: CoreId) {
+        smp::kick(target.raw() as usize);
+    }
 
     fn core_id(&self) -> CoreId {
-        CoreId::from_raw(0)
+        CoreId::from_raw(smp::hart_id() as u8)
     }
 
     fn num_cores(&self) -> u8 {
         self.num_cores
     }
 
-    fn map_shared(
-        &mut self,
-        process: ProcessId,
-        base: PhysicalAddress,
-        size: PageCount,
-        permissions: PermissionSet,
-    ) {
-        let pt = self.ensure_page_table(process);
-        mmu::map(pt, mmu::Mapping {
-            va: VirtualAddress::from_raw(base.raw()),
-            pa: base,
-            pages: size.value() as usize,
-            flags: mmu::Sv39Flags::user(
-                permissions.allows(Permission::Read),
-                permissions.allows(Permission::Write),
-                permissions.allows(Permission::Execute),
-            ),
-        });
-    }
-
     fn debug_putchar(&self, byte: u8) {
         crate::hw::uart::Uart::new().put_char(byte);
     }
 
-    fn translate_va(&self, process: ProcessId, va: VirtualAddress) -> Option<PhysicalAddress> {
-        let pt_addr = self.page_tables[process.raw() as usize];
-        if pt_addr == 0 { return None; }
-        let pt = unsafe { &*(pt_addr as *const mmu::PageTable) };
-        mmu::translate(pt, va.raw()).map(PhysicalAddress::from_raw)
-    }
-
-    fn map_user_page(&mut self, process: ProcessId, va: VirtualAddress, pa: PhysicalAddress, writable: bool, executable: bool) {
-        let pt = self.ensure_page_table(process);
-        let flags = mmu::Sv39Flags::user(true, writable, executable);
-        mmu::map(pt, mmu::Mapping {
-            va,
-            pa,
-            pages: 1,
-            flags,
-        });
-    }
-
     fn halt(&self) -> ! {
         unsafe {
             core::arch::asm!(
                 "ecall",
-                in("a0") 0usize,
-                in("a1") 0usize,
+                inlateout("a0") 0usize => _,
+                inlateout("a1") 0usize => _,
                 in("a7") 0x53525354usize,
                 in("a6") 0usize,
             );
         }
-        loop { unsafe { core::arch::asm!("wfi") }; }
+        loop {
+            unsafe { core::arch::asm!("wfi") };
+        }
     }
 }

crates/adapter-riscv/src/smp.rs

@@ -0,0 +1,220 @@
+//! Harts. Each hart has its own kernel stack, and its hart id doubles as
+//! its kernel `CoreId`. The kernel is entered under one lock for now (stage
+//! 1 of multi-core; the kernel itself stays a sequential program), so
+//! userspace runs in parallel and the kernel does not.
+//!
+//! Harts talk through IPIs carrying two kinds of request:
+//! - reschedule: the kernel made work for this hart, or took its thread
+//!   away; handled under the lock on the way out of the kernel.
+//! - leave root R: a page table this hart may be using is changing or about
+//!   to be freed; the hart switches to the kernel's root and flushes its
+//!   TLB. This needs no lock, so it is serviced even while a hart spins
+//!   waiting for the lock or idles, and the sender (which holds the lock)
+//!   can wait for the acknowledgement without deadlocking.
+
+use core::sync::atomic::{AtomicBool, AtomicU32, AtomicUsize, Ordering};
+
+use crate::mmu;
+
+/// Must match linker.ld.
+pub const MAX_HARTS: usize = 8;
+/// A guard page and a 512 KiB stack (boot builds big tables on it). Must
+/// match linker.ld.
+pub const STACK_SLOT: usize = 4096 + 0x8_0000;
+
+const SIP_SSIP: usize = 1 << 1;
+
+/// The hart running this code, from which kernel stack it is on.
+pub fn hart_id() -> usize {
+    let sp: usize;
+    // SAFETY: reading sp has no side effects.
+    unsafe { core::arch::asm!("mv {0}, sp", out(reg) sp) };
+    (sp - stacks_start()) / STACK_SLOT
+}
+
+pub fn stacks_start() -> usize {
+    unsafe extern "C" {
+        static _stacks_start: u8;
+    }
+    // SAFETY: only the symbol's address is taken.
+    unsafe { &_stacks_start as *const u8 as usize }
+}
+
+static BOOT_HART: AtomicUsize = AtomicUsize::new(0);
+static NUM_HARTS: AtomicUsize = AtomicUsize::new(1);
+/// Physical address of the kernel's own root table.
+static KERNEL_ROOT: AtomicUsize = AtomicUsize::new(0);
+
+/// The root table each hart translates with.
+static ACTIVE_ROOT: [AtomicUsize; MAX_HARTS] = [const { AtomicUsize::new(0) }; MAX_HARTS];
+static RESCHEDULE: [AtomicBool; MAX_HARTS] = [const { AtomicBool::new(false) }; MAX_HARTS];
+static LEAVE_ROOT: [AtomicUsize; MAX_HARTS] = [const { AtomicUsize::new(0) }; MAX_HARTS];
+static LEFT: [AtomicUsize; MAX_HARTS] = [const { AtomicUsize::new(0) }; MAX_HARTS];
+
+pub fn boot_hart() -> usize {
+    BOOT_HART.load(Ordering::Relaxed)
+}
+
+pub fn num_harts() -> usize {
+    NUM_HARTS.load(Ordering::Relaxed)
+}
+
+pub fn kernel_root() -> usize {
+    KERNEL_ROOT.load(Ordering::Relaxed)
+}
+
+/// Records which hart booted and how many there are, and where the
+/// kernel's root table is.
+pub fn init(boot: usize, harts: usize, kernel_root: usize) {
+    BOOT_HART.store(boot, Ordering::Relaxed);
+    NUM_HARTS.store(harts, Ordering::Relaxed);
+    KERNEL_ROOT.store(kernel_root, Ordering::Relaxed);
+}
+
+/// Called by `mmu::activate`.
+pub fn note_active_root(root: usize) {
+    if let Some(r) = ACTIVE_ROOT.get(hart_id()) {
+        r.store(root, Ordering::SeqCst);
+    }
+}
+
+// ---- the kernel lock ----
+
+static NEXT_TICKET: AtomicU32 = AtomicU32::new(0);
+static SERVING: AtomicU32 = AtomicU32::new(0);
+
+/// Takes the kernel lock, first come first served. Leave-root requests
+/// are serviced while waiting.
+pub fn lock() {
+    let ticket = NEXT_TICKET.fetch_add(1, Ordering::Relaxed);
+    while SERVING.load(Ordering::Acquire) != ticket {
+        service_ipi();
+        core::hint::spin_loop();
+    }
+}
+
+pub fn unlock() {
+    SERVING.fetch_add(1, Ordering::Release);
+}
+
+// ---- IPIs ----
+
+/// The lock-free half of an IPI: acknowledges it and, if asked, leaves the
+/// root being changed. Safe to call at any time, any number of times.
+pub fn service_ipi() {
+    let sip: usize;
+    // SAFETY: reading sip has no side effects.
+    unsafe { core::arch::asm!("csrr {0}, sip", out(reg) sip) };
+    if sip & SIP_SSIP == 0 {
+        return;
+    }
+    // Clear first: a request posted after this raises SSIP again.
+    // SAFETY: clearing our own pending software interrupt.
+    unsafe { core::arch::asm!("csrc sip, {0}", in(reg) SIP_SSIP) };
+    let me = hart_id();
+    let (Some(leave), Some(left)) = (LEAVE_ROOT.get(me), LEFT.get(me)) else {
+        return;
+    };
+    let root = leave.swap(0, Ordering::SeqCst);
+    if root != 0 {
+        if ACTIVE_ROOT.get(me).map(|r| r.load(Ordering::SeqCst)) == Some(root) {
+            mmu::activate(mmu::page_table::table_at(kernel_root()));
+        }
+        // SAFETY: flushing translations has no other effect.
+        unsafe { core::arch::asm!("sfence.vma zero, zero") };
+        left.fetch_add(1, Ordering::SeqCst);
+    }
+}
+
+/// Asks `hart` to look at its run queue again, on its way out of the
+/// kernel.
+pub fn kick(hart: usize) {
+    if let Some(r) = RESCHEDULE.get(hart) {
+        r.store(true, Ordering::SeqCst);
+        sbi_send_ipi(hart);
+    }
+}
+
+/// Consumes this hart's reschedule request.
+pub fn take_reschedule() -> bool {
+    RESCHEDULE
+        .get(hart_id())
+        .is_some_and(|r| r.swap(false, Ordering::SeqCst))
+}
+
+/// Makes every other hart that translates through `root` leave it and
+/// flush, and waits until each has. Called with the kernel lock held, so
+/// no hart can start using `root` meanwhile.
+pub fn shoot_down(root: usize) {
+    let me = hart_id();
+    for hart in 0..num_harts() {
+        if hart == me || ACTIVE_ROOT[hart].load(Ordering::SeqCst) != root {
+            continue;
+        }
+        let seen = LEFT[hart].load(Ordering::SeqCst);
+        LEAVE_ROOT[hart].store(root, Ordering::SeqCst);
+        sbi_send_ipi(hart);
+        while LEFT[hart].load(Ordering::SeqCst) == seen {
+            core::hint::spin_loop();
+        }
+    }
+}
+
+// ---- SBI ----
+
+const SBI_EXT_IPI: usize = 0x735049;
+const SBI_EXT_HSM: usize = 0x48534D;
+
+fn sbi_send_ipi(hart: usize) {
+    // SAFETY: an SBI call; a0 and a1 come back clobbered.
+    unsafe {
+        core::arch::asm!(
+            "ecall",
+            inlateout("a0") 1usize => _,
+            inlateout("a1") hart => _,
+            in("a6") 0usize,
+            in("a7") SBI_EXT_IPI,
+        );
+    }
+}
+
+/// Whether `hart` exists, per SBI HSM `hart_get_status`.
+fn sbi_hart_exists(hart: usize) -> bool {
+    let error: isize;
+    // SAFETY: an SBI call; a0 and a1 come back clobbered.
+    unsafe {
+        core::arch::asm!(
+            "ecall",
+            inlateout("a0") hart => error,
+            lateout("a1") _,
+            in("a6") 2usize,
+            in("a7") SBI_EXT_HSM,
+        );
+    }
+    error == 0
+}
+
+/// The number of harts, counting up from hart 0 until one is missing.
+pub fn probe_harts() -> usize {
+    (0..MAX_HARTS)
+        .take_while(|h| sbi_hart_exists(*h))
+        .count()
+        .max(1)
+}
+
+/// Starts `hart` at the physical address `entry` with the MMU off.
+pub fn sbi_hart_start(hart: usize, entry: usize) -> bool {
+    let error: isize;
+    // SAFETY: an SBI call; a0 and a1 come back clobbered.
+    unsafe {
+        core::arch::asm!(
+            "ecall",
+            inlateout("a0") hart => error,
+            inlateout("a1") entry => _,
+            in("a2") 0usize,
+            in("a6") 0usize,
+            in("a7") SBI_EXT_HSM,
+        );
+    }
+    error == 0
+}

crates/adapter-riscv/src/trap/mod.rs

@@ -7,17 +7,9 @@ pub struct TrapFrame {
     pub sstatus: usize,
 }
 
-impl TrapFrame {
-    pub fn new() -> Self {
-        Self {
-            regs: [0; 32],
-            sepc: 0,
-            sstatus: 0,
-        }
-    }
-}
-
-global_asm!(r#"
+global_asm!(
+    r#"
+.section .text
 .align 4
 .globl trap_vector
 trap_vector:
@@ -68,7 +60,14 @@ _from_user:
 
     mv a0, sp
     call trap_handler_rust
+    j _restore_frame
 
+# trap_return(frame): resume whatever `frame` describes, as if returning
+# from a trap that saved it. Used to enter userspace for the first time.
+.globl trap_return
+trap_return:
+    mv sp, a0
+_restore_frame:
     ld t0, 256(sp)
     csrw sepc, t0
     ld t0, 264(sp)
@@ -84,7 +83,6 @@ _restore_smode:
     ld x1,   8(sp)
     ld x3,  24(sp)
     ld x4,  32(sp)
-    ld x5,  40(sp)
     ld x6,  48(sp)
     ld x7,  56(sp)
     ld x8,  64(sp)
@@ -112,27 +110,37 @@ _restore_smode:
     ld x30, 240(sp)
     ld x31, 248(sp)
 
-    addi sp, sp, 272
-
+    # Every GPR except t0 (x5) is restored. Decide where we return to while
+    # t0 is still free, and restore it last on each path; using t0 after
+    # its restore would corrupt the interrupted program's t0.
     csrr t0, sstatus
     andi t0, t0, 0x100
     bnez t0, _sret_smode
+    ld x5,  40(sp)
+    addi sp, sp, 272
     csrrw sp, sscratch, sp
-_sret_smode:
     sret
-"#);
+_sret_smode:
+    ld x5,  40(sp)
+    addi sp, sp, 272
+    sret
+"#
+);
 
 const CAUSE_INTERRUPT_BIT: usize = 1 << 63;
+const CAUSE_S_SOFTWARE: usize = 1;
 const CAUSE_S_TIMER: usize = 5;
 const CAUSE_S_EXTERNAL: usize = 9;
 const CAUSE_ECALL_U: usize = 8;
+/// Set in `sstatus` when the trap came from supervisor mode.
+const SSTATUS_SPP: usize = 1 << 8;
 
 pub fn init() {
     unsafe extern "C" {
         fn trap_vector();
     }
     unsafe {
-        let addr = trap_vector as usize;
+        let addr = trap_vector as *const () as usize;
         core::arch::asm!("csrw stvec, {0}", in(reg) addr);
         core::arch::asm!("csrw sscratch, zero");
         // SIE stays clear — interrupts are enabled only when entering userspace via sret
@@ -147,133 +155,18 @@ pub fn set_kernel_stack(kernel_sp: usize) {
     }
 }
 
-fn decode_syscall(frame: &TrapFrame) -> Option<domain::syscall::Syscall> {
-    use domain::message::Message;
-    use domain::syscall::{Syscall, WaitSet};
-    use types::syscall_abi::*;
-
-    let nr = frame.regs[17]; // a7
-    let a0 = frame.regs[10];
-    let a1 = frame.regs[11];
-    let a2 = frame.regs[12];
-    let a3 = frame.regs[13];
-    let a4 = frame.regs[14];
-
-    match nr {
-        SYS_EXIT => Some(Syscall::Exit),
-        SYS_HALT => Some(Syscall::Halt),
-        SYS_EXIT_THREAD => Some(Syscall::ExitThread),
-        SYS_YIELD => Some(Syscall::Yield),
-        SYS_GET_TIME => Some(Syscall::GetTime),
-        SYS_GET_PROCESS_ID => Some(Syscall::GetProcessId),
-        SYS_SEND => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            let msg = Message::from_words([a1, a2, a3, a4]);
-            Some(Syscall::Send { endpoint: slot, message: msg })
-        }
-        SYS_RECEIVE => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::Receive { endpoint: slot })
-        }
-        SYS_DELEGATE => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            let to = types::bounded::CapSlot::new(a1 as u8)?;
-            let perms = types::permission::PermissionSet::from_bits(a2 as u8);
-            Some(Syscall::Delegate { slot, to_endpoint: to, permissions: perms })
-        }
-        SYS_WAIT_FOR_INTERRUPT => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::WaitForInterrupt { irq: slot })
-        }
-        SYS_ACKNOWLEDGE_INTERRUPT => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::AcknowledgeInterrupt { irq: slot })
-        }
-        SYS_WAIT_ANY => {
-            let ep0 = if a0 != usize::MAX { types::bounded::CapSlot::new(a0 as u8) } else { None };
-            let ep1 = if a1 != usize::MAX { types::bounded::CapSlot::new(a1 as u8) } else { None };
-            let ep2 = if a2 != usize::MAX { types::bounded::CapSlot::new(a2 as u8) } else { None };
-            let ep3 = if a3 != usize::MAX { types::bounded::CapSlot::new(a3 as u8) } else { None };
-            let sources = WaitSet::new(
-                [ep0, ep1, ep2, ep3],
-                [None, None, None, None],
-            );
-            Some(Syscall::WaitAny { sources })
-        }
-        SYS_CREATE_PROCESS => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::CreateProcess {
-                create_cap: slot,
-                image: types::address::DataRef::empty(),
-            })
-        }
-        SYS_KILL => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::Kill { process: slot })
-        }
-        SYS_REVOKE => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::Revoke { slot })
-        }
-        SYS_SPAWN_THREAD => Some(Syscall::SpawnThread {
-            entry: types::address::EntryPoint::from_raw(a0),
-            stack: types::address::StackPointer::from_raw(a1),
-        }),
-        SYS_REQUEST_PAGES => {
-            let count = types::bounded::PageCount::new(a0 as u16)?;
-            Some(Syscall::RequestPages { count })
-        }
-        SYS_RELEASE_PAGES => {
-            let count = types::bounded::PageCount::new(a1 as u16)?;
-            Some(Syscall::ReleasePages {
-                addr: types::address::VirtualAddress::from_raw(a0),
-                count,
-            })
-        }
-        SYS_SPAWN_THREAD_IN => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::SpawnThreadIn {
-                process: slot,
-                entry: types::address::EntryPoint::from_raw(a1),
-                stack: types::address::StackPointer::from_raw(a2),
-            })
-        }
-        SYS_CREATE_ENDPOINT => Some(Syscall::CreateEndpoint),
-        SYS_DEBUG_PUTCHAR => Some(Syscall::DebugPutchar { byte: a0 as u8 }),
-        SYS_MAP_PAGE => {
-            let slot = types::bounded::CapSlot::new(a0 as u8)?;
-            Some(Syscall::MapPage {
-                process: slot,
-                src_va: types::address::VirtualAddress::from_raw(a1),
-                dst_va: types::address::VirtualAddress::from_raw(a2),
-                executable: a3 != 0,
-            })
-        }
-        _ => None,
-    }
+fn args(frame: &TrapFrame) -> [usize; 6] {
+    let mut a = [0usize; 6];
+    a.copy_from_slice(&frame.regs[10..16]);
+    a
 }
 
-fn write_result(frame: &mut TrapFrame, outcome: &kernel::SyscallOutcome) {
-    use kernel::{SyscallOutcome, SyscallResult};
+fn set_results(frame: &mut TrapFrame, regs: [usize; 8]) {
+    frame.regs[10..18].copy_from_slice(&regs);
+}
 
-    match outcome {
-        SyscallOutcome::Complete(result) => match result {
-            SyscallResult::Ok => frame.regs[10] = 0,
-            SyscallResult::Value(v) => frame.regs[10] = *v,
-            SyscallResult::Slot(s) => frame.regs[10] = s.value() as usize,
-            SyscallResult::Message(m) => {
-                frame.regs[10] = m.word(0);
-                frame.regs[11] = m.word(1);
-                frame.regs[12] = m.word(2);
-                frame.regs[13] = m.word(3);
-            }
-            SyscallResult::Error(_) => frame.regs[10] = usize::MAX,
-            SyscallResult::WakeReason(_) => frame.regs[10] = 0,
-        },
-        SyscallOutcome::BlockCaller(_) => {}
-        SyscallOutcome::SwitchTo(_) => frame.regs[10] = 0,
-        SyscallOutcome::TerminateCaller => {}
-    }
+fn write_result(frame: &mut TrapFrame, result: &kernel::SyscallResult) {
+    set_results(frame, kernel::abi::encode(result));
 }
 
 fn save_frame_to_context(frame: &TrapFrame, ctx: &mut domain::thread::SavedContext) {
@@ -292,88 +185,136 @@ fn load_context_to_frame(ctx: &domain::thread::SavedContext, frame: &mut TrapFra
 }
 
 fn apply_pending_result(frame: &mut TrapFrame, tid: types::id::ThreadId) {
-    let kern = unsafe { &mut *crate::kernel_ptr() };
-    if let Some(result) = kern.take_pending_result(tid) {
-        write_result_direct(frame, &result);
+    if let Some(result) = kern().take_pending_result(tid) {
+        write_result(frame, &result);
     }
 }
 
-fn write_result_direct(frame: &mut TrapFrame, result: &kernel::SyscallResult) {
-    use kernel::SyscallResult;
-    match result {
-        SyscallResult::Ok => frame.regs[10] = 0,
-        SyscallResult::Value(v) => frame.regs[10] = *v,
-        SyscallResult::Slot(s) => frame.regs[10] = s.value() as usize,
-        SyscallResult::Message(m) => {
-            frame.regs[10] = m.word(0);
-            frame.regs[11] = m.word(1);
-            frame.regs[12] = m.word(2);
-            frame.regs[13] = m.word(3);
-        }
-        SyscallResult::Error(_) => frame.regs[10] = usize::MAX,
-        SyscallResult::WakeReason(_) => frame.regs[10] = 0,
-    }
+unsafe extern "C" {
+    fn trap_return(frame: *mut TrapFrame) -> !;
 }
 
-fn switch_to_thread(frame: &mut TrapFrame, current_tid: types::id::ThreadId, next_tid: types::id::ThreadId) {
-    let kern = unsafe { &mut *crate::kernel_ptr() };
+fn kern() -> &'static mut kernel::Kernel<crate::platform::RiscVPlatform> {
+    // SAFETY: only called with the kernel lock held.
+    unsafe { &mut *crate::kernel_ptr() }
+}
 
-    if let Some(ctx) = kern.thread_context_mut(current_tid) {
+fn this_core() -> types::id::CoreId {
+    types::id::CoreId::from_raw(crate::smp::hart_id() as u8)
+}
+
+/// Saves `frame` into `from` (if it still exists) and loads `to`.
+fn switch_to_thread(
+    frame: &mut TrapFrame,
+    from: Option<types::id::ThreadId>,
+    to: types::id::ThreadId,
+) {
+    let kern = kern();
+    if let Some(ctx) = from.and_then(|t| kern.thread_context_mut(t)) {
         save_frame_to_context(frame, ctx);
     }
-
-    let next_pid = kern.thread_process(next_tid);
-    let current_pid = kern.thread_process(current_tid);
-
-    if let Some(ctx) = kern.thread_context(next_tid) {
+    if let Some(ctx) = kern.thread_context(to) {
         load_context_to_frame(ctx, frame);
     }
-
-    apply_pending_result(frame, next_tid);
-
-    if next_pid != current_pid {
-        if let Some(pid) = next_pid {
-            let pt_addr = kern.platform_mut().page_table_for(pid);
-            if pt_addr != 0 {
-                let pt = unsafe { &*(pt_addr as *const crate::mmu::PageTable) };
-                crate::mmu::activate(pt);
-            }
-        }
-    }
+    apply_pending_result(frame, to);
 }
 
-fn switch_to_next(frame: &mut TrapFrame, current_tid: types::id::ThreadId) {
-    let kern = unsafe { &mut *crate::kernel_ptr() };
-
-    if let Some(ctx) = kern.thread_context_mut(current_tid) {
+/// Saves `from` and runs the next ready thread, idling until there is one.
+fn switch_to_next(frame: &mut TrapFrame, from: Option<types::id::ThreadId>) {
+    if let Some(ctx) = from.and_then(|t| kern().thread_context_mut(t)) {
         save_frame_to_context(frame, ctx);
     }
-
-    if let Some(next_tid) = kern.pick_next_thread() {
-        let next_pid = kern.thread_process(next_tid);
-        let current_pid = kern.thread_process(current_tid);
-
-        let core = types::id::CoreId::from_raw(0);
-        let _ = kern.set_thread_running(next_tid, core);
-
-        if let Some(ctx) = kern.thread_context(next_tid) {
-            load_context_to_frame(ctx, frame);
+    let next = next_runnable();
+    let _ = kern().set_thread_running(next, this_core());
+    switch_to_thread(frame, None, next);
 }
 
-        apply_pending_result(frame, next_tid);
-
-        if next_pid != current_pid {
-            if let Some(pid) = next_pid {
-                let pt_addr = kern.platform_mut().page_table_for(pid);
-                if pt_addr != 0 {
-                    let pt = unsafe { &*(pt_addr as *const crate::mmu::PageTable) };
-                    crate::mmu::activate(pt);
+/// The next thread to run on this hart, idling until one is ready.
+///
+/// Idling gives up the kernel lock: an idle hart holds nothing, so other
+/// harts can make work for it (and kick it) meanwhile. It also leaves any
+/// user address space first, so nobody needs to shoot it down. SIE stays
+/// clear; `wfi` still wakes on a pending interrupt, serviced by polling.
+fn next_runnable() -> types::id::ThreadId {
+    loop {
+        if let Some(tid) = kern().pick_next_thread() {
+            return tid;
+        }
+        crate::mmu::activate(crate::mmu::page_table::table_at(crate::smp::kernel_root()));
+        crate::smp::unlock();
+        unsafe { core::arch::asm!("wfi") };
+        crate::smp::service_ipi();
+        crate::smp::lock();
+        let _ = crate::smp::take_reschedule();
+        let sip: usize;
+        unsafe { core::arch::asm!("csrr {0}, sip", out(reg) sip) };
+        if sip & (1 << CAUSE_S_TIMER) != 0 {
+            // No thread is running, so there is no time slice to charge.
+            crate::hw::timer::handle_interrupt();
+        }
+        if sip & (1 << CAUSE_S_EXTERNAL) != 0 {
+            dispatch_external();
         }
     }
 }
-    } else {
-        loop { unsafe { core::arch::asm!("wfi") }; }
+
+/// Claims every pending PLIC interrupt and hands each to the kernel. Only
+/// the boot hart receives external interrupts.
+fn dispatch_external() {
+    loop {
+        let irq_num = crate::hw::plic::Plic::claim();
+        if irq_num == 0 {
+            return;
         }
+        kern().handle_interrupt(types::id::IrqId::from_raw(irq_num as u16));
+        crate::hw::plic::Plic::complete(irq_num);
+    }
+}
+
+/// Last step before leaving the kernel to userspace: act on a reschedule
+/// request, make sure this hart has a thread (its own may have been taken
+/// away by another hart), and translate through that thread's address
+/// space.
+fn finish(frame: &mut TrapFrame) {
+    let kern = kern();
+    let current = kern.current_thread();
+    if crate::smp::take_reschedule()
+        && let Some(cur) = current
+        && let domain::scheduler::SchedulerDecision::Preempt(next) = kern.reschedule(this_core())
+    {
+        switch_to_thread(frame, Some(cur), next);
+    }
+    if kern.current_thread().is_none() {
+        switch_to_next(frame, None);
+    }
+    let root = kern
+        .current_thread()
+        .and_then(|t| kern.thread_process(t))
+        .map(|pid| kern.platform_mut().page_table_for(pid))
+        .unwrap_or(0);
+    if root != 0 && crate::mmu::active_root() != root {
+        crate::mmu::activate(crate::mmu::page_table::table_at(root));
+    }
+}
+
+/// Leaves the kernel for userspace for the first time on this hart, with
+/// the kernel lock held: runs the thread the kernel already made current
+/// here (init, on the boot hart) or the next one homed here.
+pub fn enter_first() -> ! {
+    let mut frame = TrapFrame {
+        regs: [0; 32],
+        sepc: 0,
+        sstatus: 0,
+    };
+    match kern().current_thread() {
+        Some(tid) => switch_to_thread(&mut frame, None, tid),
+        None => switch_to_next(&mut frame, None),
+    }
+    finish(&mut frame);
+    crate::smp::unlock();
+    // SAFETY: `frame` holds a user context; sscratch is set from it on
+    // the way out, so later traps land at the top of this frame.
+    unsafe { trap_return(&mut frame) }
 }
 
 #[unsafe(no_mangle)]
@@ -381,68 +322,83 @@ extern "C" fn trap_handler_rust(frame: &mut TrapFrame) {
     let scause: usize;
     unsafe { core::arch::asm!("csrr {0}, scause", out(reg) scause) };
 
+    if frame.sstatus & SSTATUS_SPP != 0 {
+        // Checked before taking the lock: this hart may already hold it.
+        kernel_fault(frame, scause);
+    }
+    crate::smp::service_ipi();
+    crate::smp::lock();
     if scause & CAUSE_INTERRUPT_BIT != 0 {
         handle_interrupt(frame, scause & !CAUSE_INTERRUPT_BIT);
     } else {
         handle_exception(frame, scause);
     }
+    finish(frame);
+    crate::smp::unlock();
 }
 
 fn handle_interrupt(frame: &mut TrapFrame, cause: usize) {
     match cause {
         CAUSE_S_TIMER => {
             crate::hw::timer::handle_interrupt();
-            let kern = unsafe { &mut *crate::kernel_ptr() };
-            let core = types::id::CoreId::from_raw(0);
+            let kern = kern();
             if let Some(current_tid) = kern.current_thread() {
-                let decision = kern.handle_tick(core);
+                let decision = kern.handle_tick(this_core());
                 if let domain::scheduler::SchedulerDecision::Preempt(next) = decision {
-                    switch_to_thread(frame, current_tid, next);
+                    switch_to_thread(frame, Some(current_tid), next);
                 }
             }
         }
-        CAUSE_S_EXTERNAL => {
-            let irq_num = crate::hw::plic::Plic::claim();
-            if irq_num != 0 {
-                let kern = unsafe { &mut *crate::kernel_ptr() };
-                let irq = types::id::IrqId::from_raw(irq_num as u16);
-                kern.handle_interrupt(irq);
-                crate::hw::plic::Plic::complete(irq_num);
-            }
-        }
+        CAUSE_S_EXTERNAL => dispatch_external(),
+        // Serviced on entry; any reschedule happens in `finish`.
+        CAUSE_S_SOFTWARE => {}
         _ => {}
     }
 }
 
+/// The kernel itself faulted (a W^X violation, a stack guard, a bad
+/// pointer). Its state can no longer be trusted, and no user thread is to
+/// blame.
+fn kernel_fault(frame: &TrapFrame, scause: usize) -> ! {
+    let uart = crate::hw::uart::Uart::new();
+    uart.write_str("KERNEL FAULT: scause=");
+    uart.write_hex(scause);
+    let stval: usize;
+    unsafe { core::arch::asm!("csrr {0}, stval", out(reg) stval) };
+    uart.write_str(" stval=");
+    uart.write_hex(stval);
+    uart.write_str(" sepc=");
+    uart.write_hex(frame.sepc);
+    uart.write_str(" hart=");
+    uart.write_dec(crate::smp::hart_id());
+    uart.put_char(b'\n');
+    crate::halt(&uart, "fault in kernel mode");
+}
+
 fn handle_exception(frame: &mut TrapFrame, scause: usize) {
     match scause {
         CAUSE_ECALL_U => {
             frame.sepc += 4;
 
-            if let Some(syscall) = decode_syscall(frame) {
-                let kern = unsafe { &mut *crate::kernel_ptr() };
+            let Some(syscall) = kernel::abi::decode(frame.regs[17], &args(frame)) else {
+                set_results(frame, kernel::abi::unknown_syscall());
+                return;
+            };
+            {
+                let kern = kern();
                 let current_tid = kern.current_thread();
                 let outcome = kern.handle_syscall(syscall);
-                write_result(frame, &outcome);
 
                 match outcome {
-                    kernel::SyscallOutcome::Complete(_) => {}
-                    kernel::SyscallOutcome::BlockCaller(_) => {
-                        if let Some(tid) = current_tid {
-                            switch_to_next(frame, tid);
-                        }
-                    }
+                    kernel::SyscallOutcome::Complete(result) => write_result(frame, &result),
+                    kernel::SyscallOutcome::BlockCaller(_) => switch_to_next(frame, current_tid),
                     kernel::SyscallOutcome::SwitchTo(next) => {
-                        if let Some(tid) = current_tid {
-                            switch_to_thread(frame, tid, next);
-                        }
+                        switch_to_thread(frame, current_tid, next)
                     }
                     kernel::SyscallOutcome::TerminateCaller => {
                         let uart = crate::hw::uart::Uart::new();
                         uart.write_str("k-os: process exited\n");
-                        if let Some(tid) = current_tid {
-                            switch_to_next(frame, tid);
-                        }
+                        switch_to_next(frame, current_tid);
                     }
                 }
             }
@@ -459,7 +415,7 @@ fn handle_exception(frame: &mut TrapFrame, scause: usize) {
             uart.write_hex(frame.sepc);
             uart.put_char(b'\n');
 
-            let kern = unsafe { &mut *crate::kernel_ptr() };
+            let kern = kern();
             if let Some(current_tid) = kern.current_thread() {
                 let fault = match scause {
                     2 => domain::fault::Fault::IllegalInstruction,
@@ -469,10 +425,10 @@ fn handle_exception(frame: &mut TrapFrame, scause: usize) {
                     _ => domain::fault::Fault::InvalidSyscall,
                 };
                 kern.handle_fault(current_tid, fault, frame.sepc);
-                switch_to_next(frame, current_tid);
-            } else {
-                loop { unsafe { core::arch::asm!("wfi") }; }
-            }
+                switch_to_next(frame, Some(current_tid));
+            }
+            // With no current thread (another hart just destroyed it),
+            // `finish` moves on to the next one.
         }
     }
 }

crates/apps/snake/src/renderer.rs

@@ -4,7 +4,7 @@ const CELL_SIZE: u16 = 24;
 const BG_COLOR: u32 = 0xFF202040;
 const SNAKE_COLOR: u32 = 0xFF00FF00;
 const HEAD_COLOR: u32 = 0xFF00CC00;
-const FOOD_COLOR: u32 = 0xFFFF0000;
+pub(crate) const FOOD_COLOR: u32 = 0xFFFF0000;
 const BORDER_COLOR: u32 = 0xFF505080;
 
 #[derive(Clone, Copy)]

crates/apps/snake/src/tests/renderer.rs

@@ -28,5 +28,5 @@ fn food_is_rendered() {
     let count = render(&snake, &mut commands);
     // Food is command index 2 (after bg and border)
     assert!(count > 2);
-    assert_eq!(commands[2].color, 0xFF0040);
+    assert_eq!(commands[2].color, crate::renderer::FOOD_COLOR);
 }

crates/domain/Cargo.toml

@@ -5,3 +5,6 @@ edition = "2024"
 
 [dependencies]
 types = { workspace = true }
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ["cfg(kani)"] }

crates/domain/src/capability/derivation.rs

@@ -0,0 +1,88 @@
+//! The capability derivation relation, reduced to its essence: every
+//! capability is a node with at most one parent. Kept free of kernel
+//! types so the revocation rule can be checked on its own.
+
+/// `result[i]` is true iff `root` is `i` or an ancestor of `i`.
+///
+/// `parents` must be acyclic, which holds because a capability's parent
+/// always exists before it does.
+pub fn descendants<const N: usize>(parents: &[Option<u16>; N], root: usize) -> [bool; N] {
+    let mut marked = [false; N];
+    let Some(r) = marked.get_mut(root) else {
+        return marked;
+    };
+    *r = true;
+    // Each pass extends the marked set by at least one generation of
+    // children; a chain in an N-node forest is at most N - 1 long.
+    for _ in 0..N {
+        let mut changed = false;
+        for i in 0..N {
+            let parent_marked = parents
+                .get(i)
+                .copied()
+                .flatten()
+                .and_then(|p| marked.get(usize::from(p)).copied())
+                .unwrap_or(false);
+            if let Some(m) = marked.get_mut(i)
+                && !*m
+                && parent_marked
+            {
+                *m = true;
+                changed = true;
+            }
+        }
+        if !changed {
+            break;
+        }
+    }
+    marked
+}
+
+#[cfg(kani)]
+mod proofs {
+    use super::descendants;
+
+    const N: usize = 4;
+
+    fn is_ancestor(parents: &[Option<u16>; N], root: usize, mut i: usize) -> bool {
+        for _ in 0..=N {
+            if i == root {
+                return true;
+            }
+            match parents[i].map(usize::from) {
+                Some(p) if p < N => i = p,
+                _ => return false,
+            }
+        }
+        false
+    }
+
+    /// On every acyclic forest of `N` capabilities, `descendants` marks
+    /// exactly the nodes `root` is an ancestor of: revocation removes the
+    /// whole subtree and nothing else.
+    #[kani::proof]
+    #[kani::unwind(6)]
+    fn marks_exactly_the_subtree() {
+        let mut parents = [None; N];
+        for slot in parents.iter_mut() {
+            if kani::any() {
+                *slot = Some(kani::any::<u16>() % N as u16);
+            }
+        }
+        // Only forests: following parents never revisits a node.
+        for start in 0..N {
+            let mut i = start;
+            let mut steps = 0;
+            while let Some(p) = parents[i] {
+                steps += 1;
+                kani::assume(steps <= N - 1);
+                i = p as usize;
+            }
+        }
+        let root = kani::any::<usize>() % N;
+        let marked = descendants(&parents, root);
+        for i in 0..N {
+            assert!(marked[i] == is_ancestor(&parents, root, i));
+        }
+    }
+}

crates/domain/src/capability/derivation_tests.rs

@@ -0,0 +1,40 @@
+use super::derivation::descendants;
+
+#[test]
+fn a_root_with_no_children_marks_only_itself() {
+    let parents = [None, None, None];
+    assert_eq!(descendants(&parents, 1), [false, true, false]);
+}
+
+#[test]
+fn marks_children_and_grandchildren() {
+    // 0 -> 1 -> 2, 0 -> 3, 4 unrelated
+    let parents = [None, Some(0), Some(1), Some(0), None];
+    assert_eq!(descendants(&parents, 0), [true, true, true, true, false]);
+}
+
+#[test]
+fn revoking_a_middle_node_spares_its_ancestors_and_siblings() {
+    // 0 -> 1 -> 2, 0 -> 3
+    let parents = [None, Some(0), Some(1), Some(0)];
+    assert_eq!(descendants(&parents, 1), [false, true, true, false]);
+}
+
+#[test]
+fn deep_chains_are_followed_to_the_end() {
+    let parents = [None, Some(0), Some(1), Some(2), Some(3), Some(4)];
+    assert_eq!(descendants(&parents, 0), [true; 6]);
+}
+
+#[test]
+fn chains_listed_out_of_order_are_still_found() {
+    // 3 -> 2 -> 1 -> 0 (children appear before their parents)
+    let parents = [Some(1), Some(2), Some(3), None];
+    assert_eq!(descendants(&parents, 3), [true, true, true, true]);
+}
+
+#[test]
+fn an_out_of_range_root_marks_nothing() {
+    let parents = [None, Some(0)];
+    assert_eq!(descendants(&parents, 7), [false, false]);
+}

crates/domain/src/capability/mod.rs

@@ -1,34 +1,80 @@
-use types::{bounded::CapSlot, generation::Generation, permission::PermissionSet};
+use types::{
+    badge::Badge, bounded::CapSlot, generation::Generation, id::ProcessId,
+    permission::PermissionSet,
+};
 
 pub mod authority;
+pub mod derivation;
 
-use crate::{error::KernelError, resource::Resource};
+#[cfg(test)]
+#[path = "derivation_tests.rs"]
+mod derivation_tests;
+
+use crate::{error::KernelError, generations::SlotGenerations, resource::Resource};
 
 #[cfg(test)]
 #[path = "tests.rs"]
 mod tests;
 
-const MAX_CAPS_PER_PROCESS: usize = 16;
+// Sized so that every representable `CapSlot` indexes a real slot.
+pub const MAX_CAPS_PER_PROCESS: usize = CapSlot::MAX as usize + 1;
 
+/// Names one capability slot at one point in time. Both generations must
+/// still match for the reference to resolve, so a reused pid or slot is
+/// never mistaken for the capability that used to live there.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct CapRef {
+    pub process: ProcessId,
+    pub process_generation: Generation,
+    pub slot: CapSlot,
+    pub slot_generation: Generation,
+}
+
+#[derive(Clone)]
 pub struct Capability {
     resource: Resource,
     permissions: PermissionSet,
     generation: Generation,
+    badge: Badge,
+    /// The capability this one was derived from (Mint, Delegate, IPC
+    /// transfer); `None` for capabilities the kernel created directly.
+    parent: Option<CapRef>,
 }
 
 impl Capability {
-    pub fn new(
-        resource: Resource,
-        permissions: PermissionSet,
-        generation: Generation,
-    ) -> Self {
+    pub fn new(resource: Resource, permissions: PermissionSet, generation: Generation) -> Self {
         Self {
             resource,
             permissions,
             generation,
+            badge: Badge::NONE,
+            parent: None,
         }
     }
 
+    pub fn with_parent(mut self, parent: Option<CapRef>) -> Self {
+        self.parent = parent;
+        self
+    }
+
+    pub fn parent(&self) -> Option<CapRef> {
+        self.parent
+    }
+
+    pub fn set_parent(&mut self, parent: Option<CapRef>) {
+        self.parent = parent;
+    }
+
+    /// The same capability with `badge` stamped on it.
+    pub fn with_badge(mut self, badge: Badge) -> Self {
+        self.badge = badge;
+        self
+    }
+
+    pub fn badge(&self) -> Badge {
+        self.badge
+    }
+
     pub fn resource(&self) -> &Resource {
         &self.resource
     }
@@ -44,39 +90,71 @@ impl Capability {
 
 pub struct CapabilityTable {
     slots: [Option<Capability>; MAX_CAPS_PER_PROCESS],
+    generations: SlotGenerations<MAX_CAPS_PER_PROCESS>,
 }
 
 impl CapabilityTable {
     pub fn new() -> Self {
         Self {
             slots: [const { None }; MAX_CAPS_PER_PROCESS],
+            generations: SlotGenerations::new(),
         }
     }
 
-    pub fn get(&self, slot: CapSlot) -> Result<&Capability, KernelError> {
-        let idx = slot.value() as usize;
-        self.slots[idx]
-            .as_ref()
+    fn slot(&self, slot: CapSlot) -> Option<&Capability> {
+        self.slots.get(slot.value() as usize)?.as_ref()
+    }
+
+    /// Generation of an occupied slot.
+    pub fn slot_generation(&self, slot: CapSlot) -> Option<Generation> {
+        self.slot(slot)?;
+        self.generations.current(slot.value() as usize)
+    }
+
+    pub fn get_mut(&mut self, slot: CapSlot) -> Result<&mut Capability, KernelError> {
+        self.slots
+            .get_mut(slot.value() as usize)
+            .and_then(Option::as_mut)
             .ok_or(KernelError::InvalidSlot(slot))
     }
 
-    pub fn insert(&mut self, cap: Capability) -> Result<CapSlot, KernelError> {
-        let idx = self
-            .slots
-            .iter()
-            .position(|s| s.is_none())
-            .ok_or(KernelError::NoFreeSlot)?;
+    pub fn iter(&self) -> impl Iterator<Item = (CapSlot, &Capability)> {
+        self.slots.iter().enumerate().filter_map(|(i, c)| {
+            let cap = c.as_ref()?;
+            Some((CapSlot::new(i as u8)?, cap))
+        })
+    }
 
-        self.slots[idx] = Some(cap);
-        CapSlot::new(idx as u8).ok_or(KernelError::NoFreeSlot)
+    pub fn get(&self, slot: CapSlot) -> Result<&Capability, KernelError> {
+        self.slot(slot).ok_or(KernelError::InvalidSlot(slot))
+    }
+
+    pub fn insert(&mut self, cap: Capability) -> Result<CapSlot, KernelError> {
+        let generations = &self.generations;
+        let (idx, free) = self
+            .slots
+            .iter_mut()
+            .enumerate()
+            .find(|(i, s)| s.is_none() && generations.is_usable(*i))
+            .ok_or(KernelError::NoFreeSlot)?;
+        let slot = CapSlot::new(idx as u8).ok_or(KernelError::NoFreeSlot)?;
+        *free = Some(cap);
+        Ok(slot)
     }
 
     pub fn remove(&mut self, slot: CapSlot) -> Result<(), KernelError> {
         let idx = slot.value() as usize;
-        if self.slots[idx].is_none() {
+        let taken = self.slots.get_mut(idx).and_then(Option::take);
+        if taken.is_none() {
             return Err(KernelError::InvalidSlot(slot));
         }
-        self.slots[idx] = None;
+        self.generations.advance(idx);
         Ok(())
     }
 }
+
+impl Default for CapabilityTable {
+    fn default() -> Self {
+        Self::new()
+    }
+}

crates/domain/src/capability/tests.rs

@@ -83,7 +83,7 @@ fn full_table_returns_no_free_slot() {
 #[test]
 fn generation_mismatch_detected() {
     let gen_v1 = Generation::initial();
-    let gen_v2 = gen_v1.next();
+    let gen_v2 = gen_v1.next().unwrap();
 
     assert!(gen_v1.is_valid_against(&gen_v1));
     assert!(!gen_v1.is_valid_against(&gen_v2));
@@ -109,7 +109,6 @@ fn restrict_to_cannot_add_permissions() {
         Permission::Write,
         Permission::Execute,
         Permission::Delegate,
-        Permission::Revoke,
     ]);
 
     let result = read_only.restrict_to(&wants_everything);
@@ -118,7 +117,6 @@ fn restrict_to_cannot_add_permissions() {
     assert!(!result.allows(Permission::Write));
     assert!(!result.allows(Permission::Execute));
     assert!(!result.allows(Permission::Delegate));
-    assert!(!result.allows(Permission::Revoke));
 }
 
 #[test]
@@ -138,7 +136,6 @@ fn empty_permission_set_allows_nothing() {
     assert!(!empty.allows(Permission::Write));
     assert!(!empty.allows(Permission::Execute));
     assert!(!empty.allows(Permission::Delegate));
-    assert!(!empty.allows(Permission::Revoke));
 }
 
 #[test]
@@ -150,3 +147,45 @@ fn capability_preserves_resource_and_permissions() {
     assert_eq!(cap.permissions(), &expected_permissions);
     assert_eq!(cap.generation(), &Generation::initial());
 }
+
+#[test]
+fn removing_a_cap_changes_its_slot_generation() {
+    let mut table = CapabilityTable::new();
+    let slot = table.insert(endpoint_cap(1, &[Permission::Read])).unwrap();
+    let before = table.slot_generation(slot).unwrap();
+    table.remove(slot).unwrap();
+    assert_eq!(
+        table.slot_generation(slot),
+        None,
+        "empty slots have no generation"
+    );
+    let again = table.insert(endpoint_cap(2, &[Permission::Read])).unwrap();
+    assert_eq!(again, slot);
+    assert!(!before.is_valid_against(&table.slot_generation(again).unwrap()));
+}
+
+#[test]
+fn iter_lists_occupied_slots() {
+    let mut table = CapabilityTable::new();
+    let a = table.insert(endpoint_cap(1, &[])).unwrap();
+    let b = table.insert(endpoint_cap(2, &[])).unwrap();
+    table.remove(a).unwrap();
+    let slots: [Option<types::bounded::CapSlot>; 2] = {
+        let mut it = table.iter().map(|(s, _)| s);
+        [it.next(), it.next()]
+    };
+    assert_eq!(slots, [Some(b), None]);
+}
+
+#[test]
+fn caps_record_their_parent() {
+    let parent = CapRef {
+        process: types::id::ProcessId::from_raw(3),
+        process_generation: Generation::initial(),
+        slot: types::bounded::CapSlot::new(4).unwrap(),
+        slot_generation: Generation::initial(),
+    };
+    let cap = endpoint_cap(1, &[]).with_parent(Some(parent));
+    assert_eq!(cap.parent(), Some(parent));
+    assert_eq!(endpoint_cap(1, &[]).parent(), None);
+}

crates/domain/src/endpoint/mod.rs

@@ -4,7 +4,10 @@ use types::{
     id::{EndpointId, ProcessId, ThreadId},
 };
 
-use crate::{endpoint::wait_queue::WaitQueue, error::KernelError, message::Message};
+use crate::{
+    endpoint::wait_queue::WaitQueue, error::KernelError, generations::SlotGenerations,
+    message::Message,
+};
 
 pub mod wait_queue;
 
@@ -14,18 +17,19 @@ mod tests;
 
 pub struct Endpoint {
     id: EndpointId,
+    /// The process that created it; the endpoint dies with its owner.
+    owner: ProcessId,
     waiting_senders: WaitQueue,
     waiting_receivers: WaitQueue,
-    generation: Generation,
 }
 
 impl Endpoint {
-    pub fn new(id: EndpointId) -> Self {
+    pub fn new(id: EndpointId, owner: ProcessId) -> Self {
         Self {
             id,
+            owner,
             waiting_senders: WaitQueue::new(),
             waiting_receivers: WaitQueue::new(),
-            generation: Generation::initial(),
         }
     }
 
@@ -33,8 +37,8 @@ impl Endpoint {
         &self.id
     }
 
-    pub fn generation(&self) -> &Generation {
-        &self.generation
+    pub fn owner(&self) -> ProcessId {
+        self.owner
     }
 
     pub fn enqueue_sender(&mut self, thread: ThreadId) -> Option<()> {
@@ -53,6 +57,22 @@ impl Endpoint {
         self.waiting_receivers.pop()
     }
 
+    pub fn senders(&self) -> impl Iterator<Item = ThreadId> + '_ {
+        self.waiting_senders.iter()
+    }
+
+    pub fn receivers(&self) -> impl Iterator<Item = ThreadId> + '_ {
+        self.waiting_receivers.iter()
+    }
+
+    pub fn is_sender(&self, thread: ThreadId) -> bool {
+        self.waiting_senders.contains(thread)
+    }
+
+    pub fn is_receiver(&self, thread: ThreadId) -> bool {
+        self.waiting_receivers.contains(thread)
+    }
+
     pub fn has_waiting_sender(&self) -> bool {
         !self.waiting_senders.is_empty()
     }
@@ -68,52 +88,85 @@ impl Endpoint {
     pub fn remove_receiver(&mut self, thread: ThreadId) -> bool {
         self.waiting_receivers.remove_thread(thread)
     }
-
-    pub fn revoke(&mut self) {
-        self.generation = self.generation.next();
-    }
 }
 
-const MAX_ENDPOINTS: usize = 256;
+pub const MAX_ENDPOINTS: usize = if cfg!(kani) { 2 } else { 256 };
 
 pub struct EndpointTable {
     endpoints: [Option<Endpoint>; MAX_ENDPOINTS],
+    generations: SlotGenerations<MAX_ENDPOINTS>,
 }
 
 impl EndpointTable {
     pub fn new() -> Self {
         Self {
             endpoints: [const { None }; MAX_ENDPOINTS],
+            generations: SlotGenerations::new(),
         }
     }
 
-    pub fn create(&mut self) -> Option<EndpointId> {
-        let idx = self.endpoints.iter().position(|s| s.is_none())?;
+    pub fn create(&mut self, owner: ProcessId) -> Option<EndpointId> {
+        let generations = &self.generations;
+        let (idx, slot) = self
+            .endpoints
+            .iter_mut()
+            .enumerate()
+            .find(|(i, s)| s.is_none() && generations.is_usable(*i))?;
         let id = EndpointId::from_raw(idx as u16);
-        self.endpoints[idx] = Some(Endpoint::new(id));
+        *slot = Some(Endpoint::new(id, owner));
         Some(id)
     }
 
+    /// Generation capabilities to a live endpoint must carry.
+    pub fn generation(&self, id: EndpointId) -> Option<Generation> {
+        self.get(id)?;
+        self.generations.current(id.raw() as usize)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = &Endpoint> {
+        self.endpoints.iter().flatten()
+    }
+
+    pub fn ids_owned_by(&self, owner: ProcessId) -> impl Iterator<Item = EndpointId> + '_ {
+        self.endpoints
+            .iter()
+            .flatten()
+            .filter(move |ep| ep.owner == owner)
+            .map(|ep| ep.id)
+    }
+
     pub fn get(&self, id: EndpointId) -> Option<&Endpoint> {
-        self.endpoints.get(id.raw() as usize).and_then(|s| s.as_ref())
+        self.endpoints
+            .get(id.raw() as usize)
+            .and_then(|s| s.as_ref())
     }
 
     pub fn get_mut(&mut self, id: EndpointId) -> Option<&mut Endpoint> {
-        self.endpoints.get_mut(id.raw() as usize).and_then(|s| s.as_mut())
+        self.endpoints
+            .get_mut(id.raw() as usize)
+            .and_then(|s| s.as_mut())
     }
 
+    /// Removes the endpoint; capabilities to it become invalid even if the
+    /// slot is later reused.
     pub fn destroy(&mut self, id: EndpointId) -> Option<Endpoint> {
-        self.endpoints.get_mut(id.raw() as usize).and_then(|s| s.take())
+        let ep = self.endpoints.get_mut(id.raw() as usize)?.take()?;
+        self.generations.advance(id.raw() as usize);
+        Some(ep)
     }
 
     pub fn remove_thread_from_all(&mut self, thread: ThreadId) {
-        for slot in &mut self.endpoints {
-            if let Some(ep) = slot {
+        for ep in self.endpoints.iter_mut().flatten() {
             ep.remove_sender(thread);
             ep.remove_receiver(thread);
         }
     }
 }
+
+impl Default for EndpointTable {
+    fn default() -> Self {
+        Self::new()
+    }
 }
 
 pub trait MessagePassing {

crates/domain/src/endpoint/tests.rs

@@ -1,35 +1,39 @@
 use crate::endpoint::wait_queue::MAX_WAITERS;
 
 use super::*;
-use types::id::{EndpointId, ThreadId};
+use types::id::{EndpointId, ProcessId, ThreadId};
 
 fn thread(id: u16) -> ThreadId {
     ThreadId::from_raw(id)
 }
 
+fn owner() -> ProcessId {
+    ProcessId::from_raw(0)
+}
+
 fn test_endpoint() -> Endpoint {
-    Endpoint::new(EndpointId::from_raw(1))
+    Endpoint::new(EndpointId::from_raw(1), owner())
 }
 
 // --- WaitQueue tests ---
 
 #[test]
 fn empty_queue_pop_returns_none() {
-    let mut queue = WaitQueue::new();
+    let mut queue: WaitQueue = WaitQueue::new();
     assert!(queue.pop().is_none());
     assert!(queue.is_empty());
 }
 
 #[test]
 fn push_then_pop_returns_same_thread() {
-    let mut queue = WaitQueue::new();
+    let mut queue: WaitQueue = WaitQueue::new();
     queue.push(thread(1)).unwrap();
     assert_eq!(queue.pop(), Some(thread(1)));
 }
 
 #[test]
 fn pop_order_is_fifo() {
-    let mut queue = WaitQueue::new();
+    let mut queue: WaitQueue = WaitQueue::new();
     queue.push(thread(1)).unwrap();
     queue.push(thread(2)).unwrap();
     queue.push(thread(3)).unwrap();
@@ -42,7 +46,7 @@ fn pop_order_is_fifo() {
 
 #[test]
 fn full_queue_rejects_push() {
-    let mut queue = WaitQueue::new();
+    let mut queue: WaitQueue = WaitQueue::new();
     for i in 0..MAX_WAITERS {
         assert!(queue.push(thread(i as u16)).is_some());
     }
@@ -51,7 +55,7 @@ fn full_queue_rejects_push() {
 
 #[test]
 fn is_empty_after_drain() {
-    let mut queue = WaitQueue::new();
+    let mut queue: WaitQueue = WaitQueue::new();
     queue.push(thread(1)).unwrap();
     queue.push(thread(2)).unwrap();
     queue.pop();
@@ -99,13 +103,34 @@ fn senders_and_receivers_are_independent() {
 }
 
 #[test]
-fn revoke_bumps_generation() {
-    let mut ep = test_endpoint();
-    let gen_before = *ep.generation();
-    ep.revoke();
-    let gen_after = *ep.generation();
+fn reused_slot_gets_a_new_generation() {
+    let mut table = EndpointTable::new();
+    let id = table.create(owner()).unwrap();
+    let old = table.generation(id).unwrap();
+    table.destroy(id);
+    assert_eq!(
+        table.generation(id),
+        None,
+        "dead endpoints have no generation"
+    );
+    let again = table.create(owner()).unwrap();
+    assert_eq!(again, id);
+    assert!(!old.is_valid_against(&table.generation(again).unwrap()));
+}
 
-    assert!(!gen_before.is_valid_against(&gen_after));
+#[test]
+fn ids_owned_by_lists_only_that_owners_endpoints() {
+    let mut table = EndpointTable::new();
+    let a = table.create(owner()).unwrap();
+    table.create(ProcessId::from_raw(1)).unwrap();
+    let c = table.create(owner()).unwrap();
+    let mut ids = [EndpointId::from_raw(u16::MAX); 4];
+    let mut n = 0;
+    for id in table.ids_owned_by(owner()) {
+        ids[n] = id;
+        n += 1;
+    }
+    assert_eq!(&ids[..n], &[a, c]);
 }
 
 #[test]
@@ -141,22 +166,22 @@ fn rendezvous_receiver_first() {
 #[test]
 fn table_create_and_lookup() {
     let mut table = EndpointTable::new();
-    let id = table.create().unwrap();
+    let id = table.create(owner()).unwrap();
     assert!(table.get(id).is_some());
 }
 
 #[test]
 fn table_create_returns_unique_ids() {
     let mut table = EndpointTable::new();
-    let a = table.create().unwrap();
-    let b = table.create().unwrap();
+    let a = table.create(owner()).unwrap();
+    let b = table.create(owner()).unwrap();
     assert_ne!(a, b);
 }
 
 #[test]
 fn table_destroy_then_get_fails() {
     let mut table = EndpointTable::new();
-    let id = table.create().unwrap();
+    let id = table.create(owner()).unwrap();
     let removed = table.destroy(id);
     assert!(removed.is_some());
     assert!(table.get(id).is_none());
@@ -165,16 +190,57 @@ fn table_destroy_then_get_fails() {
 #[test]
 fn table_get_mut_allows_enqueue() {
     let mut table = EndpointTable::new();
-    let id = table.create().unwrap();
-    table.get_mut(id).unwrap().enqueue_sender(thread(1)).unwrap();
+    let id = table.create(owner()).unwrap();
+    table
+        .get_mut(id)
+        .unwrap()
+        .enqueue_sender(thread(1))
+        .unwrap();
     assert!(table.get(id).unwrap().has_waiting_sender());
 }
 
 #[test]
 fn table_destroy_reuses_slot() {
     let mut table = EndpointTable::new();
-    let id = table.create().unwrap();
+    let id = table.create(owner()).unwrap();
     table.destroy(id);
-    let new_id = table.create().unwrap();
+    let new_id = table.create(owner()).unwrap();
     assert_eq!(id, new_id);
 }
+
+#[test]
+fn wait_queue_is_fifo_even_after_a_pop_leaves_a_hole() {
+    let mut q: WaitQueue = WaitQueue::new();
+    q.push(thread(1)).unwrap();
+    q.push(thread(2)).unwrap();
+    assert_eq!(q.pop(), Some(thread(1)));
+    q.push(thread(3)).unwrap();
+    assert_eq!(q.pop(), Some(thread(2)), "thread 3 jumped the queue");
+    assert_eq!(q.pop(), Some(thread(3)));
+}
+
+#[test]
+fn wait_queue_keeps_order_around_a_removed_thread() {
+    let mut q: WaitQueue = WaitQueue::new();
+    for n in 1..=3 {
+        q.push(thread(n)).unwrap();
+    }
+    assert!(q.remove_thread(thread(2)));
+    q.push(thread(4)).unwrap();
+    assert_eq!(q.pop(), Some(thread(1)));
+    assert_eq!(q.pop(), Some(thread(3)));
+    assert_eq!(q.pop(), Some(thread(4)));
+    assert_eq!(q.pop(), None);
+}
+
+#[test]
+fn wait_queue_kani_trace_push_push_remove() {
+    let mut q: WaitQueue<3> = WaitQueue::new();
+    q.push(thread(3)).unwrap();
+    q.push(thread(2)).unwrap();
+    assert!(q.remove_thread(thread(3)));
+    assert!(!q.remove_thread(thread(0)));
+    assert!(!q.remove_thread(thread(3)));
+    assert_eq!(q.pop(), Some(thread(2)));
+    assert_eq!(q.pop(), None);
+}

crates/domain/src/endpoint/wait_queue.rs

@@ -1,46 +1,141 @@
 use types::id::ThreadId;
 
-pub const MAX_WAITERS: usize = 16;
+pub const MAX_WAITERS: usize = if cfg!(kani) { 2 } else { 16 };
 
-pub struct WaitQueue {
-    entries: [Option<ThreadId>; MAX_WAITERS],
-    count: u8,
+/// Bounded FIFO of blocked threads. Order is preserved across pops and
+/// removals, so no waiter can be overtaken.
+pub struct WaitQueue<const N: usize = MAX_WAITERS> {
+    entries: [Option<ThreadId>; N],
+    len: usize,
 }
 
-impl WaitQueue {
+impl<const N: usize> WaitQueue<N> {
     pub fn new() -> Self {
         Self {
-            entries: [None; MAX_WAITERS],
-            count: 0,
+            entries: [None; N],
+            len: 0,
         }
     }
 
     pub fn push(&mut self, thread: ThreadId) -> Option<()> {
-        let slot = self.entries.iter_mut().find(|s| s.is_none())?;
-        *slot = Some(thread);
-        self.count += 1;
+        if self.len == N || self.contains(thread) {
+            return None;
+        }
+        *self.entries.get_mut(self.len)? = Some(thread);
+        self.len += 1;
         Some(())
     }
 
     pub fn pop(&mut self) -> Option<ThreadId> {
-        let slot = self.entries.iter_mut().find(|s| s.is_some())?;
-        let thread = slot.take();
-        self.count -= 1;
-        thread
+        let head = self.entries.first().copied().flatten()?;
+        self.close_gap(0);
+        Some(head)
     }
 
     pub fn remove_thread(&mut self, thread: ThreadId) -> bool {
-        for slot in &mut self.entries {
-            if *slot == Some(thread) {
-                *slot = None;
-                self.count -= 1;
-                return true;
+        match self.entries[..self.len]
+            .iter()
+            .position(|e| *e == Some(thread))
+        {
+            Some(i) => {
+                self.close_gap(i);
+                true
+            }
+            None => false,
         }
     }
-        false
+
+    pub fn iter(&self) -> impl Iterator<Item = ThreadId> + '_ {
+        self.entries.iter().take(self.len).flatten().copied()
+    }
+
+    pub fn contains(&self, thread: ThreadId) -> bool {
+        self.entries
+            .iter()
+            .take(self.len)
+            .any(|e| *e == Some(thread))
     }
 
     pub fn is_empty(&self) -> bool {
-        self.count == 0
+        self.len == 0
+    }
+
+    /// Removes entry `i`, shifting later entries forward to keep order.
+    fn close_gap(&mut self, i: usize) {
+        for j in i..self.len.saturating_sub(1) {
+            let next = self.entries.get(j + 1).copied().flatten();
+            if let Some(e) = self.entries.get_mut(j) {
+                *e = next;
+            }
+        }
+        self.len = self.len.saturating_sub(1);
+        if let Some(last) = self.entries.get_mut(self.len) {
+            *last = None;
+        }
+    }
+}
+
+impl<const N: usize> Default for WaitQueue<N> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(kani)]
+mod proofs {
+    use super::*;
+
+    /// Against a simple reference model (a plain array kept in arrival
+    /// order), any sequence of pushes, pops and removals behaves the same:
+    /// FIFO order, no duplicates, nothing lost.
+    #[kani::proof]
+    #[kani::unwind(7)]
+    fn behaves_like_a_fifo_without_duplicates() {
+        const CAP: usize = 3;
+        let mut q: WaitQueue<CAP> = WaitQueue::new();
+        let mut model = [0u16; CAP];
+        let mut len = 0usize;
+
+        for _ in 0..5 {
+            let t: u16 = kani::any::<u16>() % 4;
+            match kani::any::<u8>() % 3 {
+                0 => {
+                    let ok = q.push(ThreadId::from_raw(t)).is_some();
+                    let dup = model[..len].contains(&t);
+                    assert!(ok == (!dup && len < CAP));
+                    if ok {
+                        model[len] = t;
+                        len += 1;
+                    }
+                }
+                1 => {
+                    let got = q.pop();
+                    if len == 0 {
+                        assert!(got.is_none());
+                    } else {
+                        assert!(got == Some(ThreadId::from_raw(model[0])));
+                        for j in 0..len - 1 {
+                            model[j] = model[j + 1];
+                        }
+                        len -= 1;
+                    }
+                }
+                _ => {
+                    let removed = q.remove_thread(ThreadId::from_raw(t));
+                    match model[..len].iter().position(|&m| m == t) {
+                        Some(i) => {
+                            assert!(removed);
+                            for j in i..len - 1 {
+                                model[j] = model[j + 1];
+                            }
+                            len -= 1;
+                        }
+                        None => assert!(!removed),
+                    }
+                }
+            }
+            assert!(q.len == len);
+            assert!(q.is_empty() == (len == 0));
+        }
     }
 }

crates/domain/src/error.rs

@@ -8,7 +8,10 @@ use types::{
 pub enum KernelError {
     InvalidSlot(CapSlot),
     RevokedCapability(CapSlot),
-    PermissionDenied { slot: CapSlot, needed: Permission },
+    PermissionDenied {
+        slot: CapSlot,
+        needed: Permission,
+    },
     NoFreeSlot,
     InvalidProcess(ProcessId),
     WouldBlock,
@@ -23,4 +26,19 @@ pub enum KernelError {
     EndpointFull,
     ProcessCreateDenied,
     IrqAlreadyOwned(IrqId),
+    /// Address outside the user window, unaligned, or not owned by the caller.
+    InvalidAddress,
+    /// The target virtual range already holds a mapping.
+    AddressInUse,
+    InvalidRegion,
+    /// The region is mapped executable somewhere and the request would map
+    /// it writable, or the other way round (W^X across processes).
+    WritableAndExecutable,
+    /// The object a capability would refer to no longer exists.
+    NoSuchObject,
+    /// The capability names the wrong kind of object for this operation.
+    WrongObject,
+    /// `Reply` with an empty reply slot, or a call whose reply was dropped.
+    NoReply,
+    InvalidArgument,
 }

crates/domain/src/generations.rs

@@ -0,0 +1,86 @@
+//! Per-slot generation counters shared by the kernel's object tables.
+
+use types::generation::Generation;
+
+#[cfg(test)]
+#[path = "generations_tests.rs"]
+mod tests;
+
+/// A slot's generation changes every time the object in it is destroyed
+/// or revoked, so capabilities minted earlier stop matching. A slot whose
+/// counter runs out is retired for good rather than reused.
+pub struct SlotGenerations<const N: usize> {
+    gens: [Option<Generation>; N],
+}
+
+impl<const N: usize> SlotGenerations<N> {
+    pub fn new() -> Self {
+        Self {
+            gens: [Some(Generation::initial()); N],
+        }
+    }
+
+    /// Current generation of `idx`, `None` if retired or out of range.
+    pub fn current(&self, idx: usize) -> Option<Generation> {
+        *self.gens.get(idx)?
+    }
+
+    pub fn is_usable(&self, idx: usize) -> bool {
+        self.current(idx).is_some()
+    }
+
+    /// Invalidates every capability minted for the current generation.
+    pub fn advance(&mut self, idx: usize) {
+        if let Some(g) = self.gens.get_mut(idx) {
+            *g = g.and_then(|g| g.next());
+        }
+    }
+}
+
+impl<const N: usize> Default for SlotGenerations<N> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(kani)]
+mod proofs {
+    use super::SlotGenerations;
+    use types::generation::Generation;
+
+    /// However many times a slot is advanced, a generation observed earlier
+    /// never comes back, so a capability minted for it stays dead.
+    #[kani::proof]
+    #[kani::unwind(5)]
+    fn an_observed_generation_never_returns() {
+        let mut g: SlotGenerations<1> = SlotGenerations::new();
+        g.gens[0] = if kani::any() {
+            Some(Generation::from_raw(kani::any()))
+        } else {
+            None
+        };
+        let observed = g.current(0);
+        let steps: u8 = kani::any();
+        kani::assume(steps >= 1 && steps <= 4);
+        for _ in 0..steps {
+            g.advance(0);
+            if let (Some(old), Some(now)) = (observed, g.current(0)) {
+                assert!(!old.is_valid_against(&now));
+            }
+        }
+    }
+
+    /// A retired slot is never usable again.
+    #[kani::proof]
+    #[kani::unwind(5)]
+    fn retired_slots_stay_retired() {
+        let mut g: SlotGenerations<1> = SlotGenerations::new();
+        g.gens[0] = None;
+        let steps: u8 = kani::any();
+        kani::assume(steps <= 4);
+        for _ in 0..steps {
+            g.advance(0);
+        }
+        assert!(!g.is_usable(0));
+    }
+}

crates/domain/src/generations_tests.rs

@@ -0,0 +1,36 @@
+use super::SlotGenerations;
+use types::generation::Generation;
+
+#[test]
+fn slots_start_at_the_initial_generation() {
+    let g: SlotGenerations<2> = SlotGenerations::new();
+    assert_eq!(g.current(0), Some(Generation::initial()));
+    assert!(g.is_usable(1));
+}
+
+#[test]
+fn advance_changes_the_generation() {
+    let mut g: SlotGenerations<2> = SlotGenerations::new();
+    let before = g.current(0);
+    g.advance(0);
+    assert_ne!(g.current(0), before);
+    assert_eq!(g.current(1), before, "other slots untouched");
+}
+
+#[test]
+fn out_of_range_slots_are_never_usable() {
+    let mut g: SlotGenerations<2> = SlotGenerations::new();
+    assert_eq!(g.current(2), None);
+    g.advance(2); // no panic
+}
+
+#[test]
+fn exhausted_counter_retires_the_slot() {
+    let mut g: SlotGenerations<1> = SlotGenerations::new();
+    g.gens[0] = Some(Generation::from_raw(u32::MAX));
+    g.advance(0);
+    assert_eq!(g.current(0), None);
+    assert!(!g.is_usable(0));
+    g.advance(0);
+    assert_eq!(g.current(0), None, "retired slots stay retired");
+}

crates/domain/src/irq/mod.rs

@@ -1,38 +1,66 @@
-use types::id::{IrqId, ThreadId};
-
-use crate::error::KernelError;
+use types::{
+    badge::Badge,
+    generation::Generation,
+    id::{IrqId, NotificationId},
+};
 
 #[cfg(test)]
 #[path = "tests.rs"]
 mod tests;
 
-const MAX_IRQS: usize = 256;
+const MAX_IRQS: usize = if cfg!(kani) { 2 } else { 256 };
+
+/// Where an interrupt is delivered: a signal on a notification, through a
+/// capability snapshot (generation and badge) taken when the route was set.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct IrqRoute {
+    pub notification: NotificationId,
+    pub generation: Generation,
+    pub badge: Badge,
+}
 
 pub struct IrqRoutingTable {
-    owners: [Option<ThreadId>; MAX_IRQS],
+    routes: [Option<IrqRoute>; MAX_IRQS],
 }
 
 impl IrqRoutingTable {
     pub fn new() -> Self {
         Self {
-            owners: [None; MAX_IRQS],
+            routes: [None; MAX_IRQS],
         }
     }
 
-    pub fn register(&mut self, irq: IrqId, thread: ThreadId) -> Result<(), KernelError> {
-        let idx = irq.raw() as usize;
-        if self.owners[idx].is_some() {
-            return Err(KernelError::IrqAlreadyOwned(irq));
-        }
-        self.owners[idx] = Some(thread);
-        Ok(())
+    /// Whether `irq` is a line this table can route.
+    pub fn is_valid(&self, irq: IrqId) -> bool {
+        (irq.raw() as usize) < MAX_IRQS
     }
 
-    pub fn unregister(&mut self, irq: IrqId) {
-        self.owners[irq.raw() as usize] = None;
+    /// Routes `irq`, replacing any previous route. Fails for lines beyond
+    /// the table.
+    pub fn set(&mut self, irq: IrqId, route: IrqRoute) -> bool {
+        match self.routes.get_mut(irq.raw() as usize) {
+            Some(slot) => {
+                *slot = Some(route);
+                true
+            }
+            None => false,
+        }
     }
 
-    pub fn owner(&self, irq: IrqId) -> Option<ThreadId> {
-        self.owners[irq.raw() as usize]
+    pub fn clear(&mut self, irq: IrqId) {
+        if let Some(slot) = self.routes.get_mut(irq.raw() as usize) {
+            *slot = None;
+        }
+    }
+
+    /// The route for `irq`; `None` for unknown or unrouted lines.
+    pub fn route(&self, irq: IrqId) -> Option<IrqRoute> {
+        *self.routes.get(irq.raw() as usize)?
+    }
+}
+
+impl Default for IrqRoutingTable {
+    fn default() -> Self {
+        Self::new()
     }
 }

crates/domain/src/irq/tests.rs

@@ -1,50 +1,43 @@
 use super::*;
-use types::id::{IrqId, ThreadId};
+use types::badge::Badge;
+use types::generation::Generation;
+use types::id::{IrqId, NotificationId};
 
-fn irq(id: u16) -> IrqId {
-    IrqId::from_raw(id)
+fn route(n: u16) -> IrqRoute {
+    IrqRoute {
+        notification: NotificationId::from_raw(n),
+        generation: Generation::initial(),
+        badge: Badge::new(1 << n),
     }
-
-fn thread(id: u16) -> ThreadId {
-    ThreadId::from_raw(id)
 }
 
 #[test]
-fn new_table_has_no_owners() {
-    let table = IrqRoutingTable::new();
-    assert!(table.owner(irq(0)).is_none());
-    assert!(table.owner(irq(10)).is_none());
+fn new_table_routes_nothing() {
+    let t = IrqRoutingTable::new();
+    assert_eq!(t.route(IrqId::from_raw(10)), None);
 }
 
 #[test]
-fn register_and_lookup() {
-    let mut table = IrqRoutingTable::new();
-    table.register(irq(5), thread(1)).unwrap();
-    assert_eq!(table.owner(irq(5)), Some(thread(1)));
+fn set_then_route() {
+    let mut t = IrqRoutingTable::new();
+    assert!(t.set(IrqId::from_raw(10), route(3)));
+    assert_eq!(t.route(IrqId::from_raw(10)), Some(route(3)));
 }
 
 #[test]
-fn register_already_owned_fails() {
-    let mut table = IrqRoutingTable::new();
-    table.register(irq(5), thread(1)).unwrap();
-    assert!(table.register(irq(5), thread(2)).is_err());
+fn set_replaces_and_clear_removes() {
+    let mut t = IrqRoutingTable::new();
+    t.set(IrqId::from_raw(10), route(3));
+    t.set(IrqId::from_raw(10), route(4));
+    assert_eq!(t.route(IrqId::from_raw(10)), Some(route(4)));
+    t.clear(IrqId::from_raw(10));
+    assert_eq!(t.route(IrqId::from_raw(10)), None);
 }
 
 #[test]
-fn unregister_then_reregister() {
-    let mut table = IrqRoutingTable::new();
-    table.register(irq(5), thread(1)).unwrap();
-    table.unregister(irq(5));
-    assert!(table.owner(irq(5)).is_none());
-    table.register(irq(5), thread(2)).unwrap();
-    assert_eq!(table.owner(irq(5)), Some(thread(2)));
-}
-
-#[test]
-fn different_irqs_independent() {
-    let mut table = IrqRoutingTable::new();
-    table.register(irq(0), thread(10)).unwrap();
-    table.register(irq(1), thread(20)).unwrap();
-    assert_eq!(table.owner(irq(0)), Some(thread(10)));
-    assert_eq!(table.owner(irq(1)), Some(thread(20)));
+fn lines_beyond_the_table_are_rejected_without_panicking() {
+    let mut t = IrqRoutingTable::new();
+    assert!(!t.set(IrqId::from_raw(1000), route(1)));
+    assert_eq!(t.route(IrqId::from_raw(1000)), None);
+    t.clear(IrqId::from_raw(1000));
 }

crates/domain/src/lib.rs

@@ -1,4 +1,18 @@
 #![no_std]
+// A kernel panic takes the whole system down, so kernel code may not
+// contain any way to panic. Tests and proofs are exempt.
+#![cfg_attr(
+    not(any(test, kani)),
+    deny(
+        clippy::unwrap_used,
+        clippy::expect_used,
+        clippy::panic,
+        clippy::unreachable,
+        clippy::todo,
+        clippy::unimplemented,
+        clippy::indexing_slicing
+    )
+)]
 
 #[cfg(kani)]
 pub mod proofs;
@@ -7,9 +21,11 @@ pub mod capability;
 pub mod endpoint;
 pub mod error;
 pub mod fault;
+pub mod generations;
 pub mod irq;
 pub mod memory;
 pub mod message;
+pub mod notification;
 pub mod process;
 pub mod resource;
 pub mod scheduler;

crates/domain/src/memory/frame/mod.rs

@@ -0,0 +1,232 @@
+//! Physical frame ownership. The kernel's single source of truth for what
+//! every frame of the user pool is used for and who is charged for it.
+
+use types::{
+    address::{PhysicalAddress, VirtualAddress},
+    id::{ProcessId, RegionId},
+    mapping::PagePerms,
+};
+
+#[cfg(test)]
+#[path = "tests.rs"]
+mod tests;
+
+#[cfg(kani)]
+#[path = "proofs.rs"]
+mod proofs;
+
+pub const PAGE_SIZE: usize = 4096;
+
+/// Frames the kernel can track. The board's user pool must fit.
+pub const MAX_FRAMES: usize = if cfg!(kani) { 6 } else { 4096 };
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum FrameUse {
+    /// Mapped exactly once, at `page` in `owner`'s address space.
+    User {
+        owner: ProcessId,
+        page: u32,
+        perms: PagePerms,
+    },
+    /// Holds part of `owner`'s page tables.
+    PageTable { owner: ProcessId },
+    /// Backs a shared memory region.
+    Region { region: RegionId },
+}
+
+impl FrameUse {
+    /// A user mapping at `va`, which must be page aligned.
+    pub fn user(owner: ProcessId, va: VirtualAddress, perms: PagePerms) -> Option<Self> {
+        if !va.raw().is_multiple_of(PAGE_SIZE) {
+            return None;
+        }
+        let page = u32::try_from(va.raw() / PAGE_SIZE).ok()?;
+        Some(Self::User { owner, page, perms })
+    }
+}
+
+pub struct FrameTable<const N: usize = MAX_FRAMES> {
+    base: PhysicalAddress,
+    total: usize,
+    frames: [Option<FrameUse>; N],
+    free: usize,
+}
+
+impl<const N: usize> FrameTable<N> {
+    pub fn new(base: PhysicalAddress, total: usize) -> Self {
+        let total = total.min(N);
+        Self {
+            base,
+            total,
+            frames: [None; N],
+            free: total,
+        }
+    }
+
+    pub fn base(&self) -> PhysicalAddress {
+        self.base
+    }
+
+    pub fn capacity(&self) -> usize {
+        self.total
+    }
+
+    pub fn free_count(&self) -> usize {
+        self.free
+    }
+
+    fn index_of(&self, pa: PhysicalAddress) -> Option<usize> {
+        let offset = pa.raw().checked_sub(self.base.raw())?;
+        if !offset.is_multiple_of(PAGE_SIZE) {
+            return None;
+        }
+        let idx = offset / PAGE_SIZE;
+        (idx < self.total).then_some(idx)
+    }
+
+    fn address_of(&self, idx: usize) -> PhysicalAddress {
+        self.base.offset(idx)
+    }
+
+    /// The frames that exist (`total` is clamped to `N` at construction).
+    fn live(&self) -> &[Option<FrameUse>] {
+        self.frames.get(..self.total).unwrap_or(&[])
+    }
+
+    fn live_mut(&mut self) -> &mut [Option<FrameUse>] {
+        self.frames.get_mut(..self.total).unwrap_or(&mut [])
+    }
+
+    pub fn get(&self, pa: PhysicalAddress) -> Option<&FrameUse> {
+        self.frames.get(self.index_of(pa)?)?.as_ref()
+    }
+
+    pub fn alloc(&mut self, usage: FrameUse) -> Option<PhysicalAddress> {
+        let (idx, slot) = self
+            .live_mut()
+            .iter_mut()
+            .enumerate()
+            .find(|(_, f)| f.is_none())?;
+        *slot = Some(usage);
+        self.free -= 1;
+        Some(self.address_of(idx))
+    }
+
+    /// Allocates `count` physically adjacent frames; frame `i` gets `usage(i)`.
+    pub fn alloc_contiguous(
+        &mut self,
+        count: usize,
+        usage: impl Fn(usize) -> FrameUse,
+    ) -> Option<PhysicalAddress> {
+        if count == 0 {
+            return None;
+        }
+        let mut run = 0;
+        let mut start = None;
+        for (idx, f) in self.live().iter().enumerate() {
+            if f.is_some() {
+                run = 0;
+                continue;
+            }
+            run += 1;
+            if run == count {
+                start = Some(idx + 1 - count);
+                break;
+            }
+        }
+        let start = start?;
+        let run = self.live_mut().get_mut(start..start + count)?;
+        for (i, f) in run.iter_mut().enumerate() {
+            *f = Some(usage(i));
+        }
+        self.free -= count;
+        Some(self.address_of(start))
+    }
+
+    /// Frees an allocated frame and reports what it was used for.
+    pub fn free(&mut self, pa: PhysicalAddress) -> Option<FrameUse> {
+        let idx = self.index_of(pa)?;
+        let usage = self.frames.get_mut(idx)?.take()?;
+        self.free += 1;
+        Some(usage)
+    }
+
+    /// Changes the use of an allocated frame (e.g. moving it to another
+    /// process). Fails on free frames.
+    pub fn retag(&mut self, pa: PhysicalAddress, usage: FrameUse) -> bool {
+        match self
+            .index_of(pa)
+            .and_then(|i| self.frames.get_mut(i))
+            .and_then(Option::as_mut)
+        {
+            Some(slot) => {
+                *slot = usage;
+                true
+            }
+            None => false,
+        }
+    }
+
+    /// The frame mapped at `va` in `owner`, if `owner` holds it as a user page.
+    pub fn find_user(
+        &self,
+        owner: ProcessId,
+        va: VirtualAddress,
+    ) -> Option<(PhysicalAddress, PagePerms)> {
+        if !va.raw().is_multiple_of(PAGE_SIZE) {
+            return None;
+        }
+        let page = u32::try_from(va.raw() / PAGE_SIZE).ok()?;
+        self.live().iter().enumerate().find_map(|(idx, f)| match f {
+            Some(FrameUse::User {
+                owner: o,
+                page: p,
+                perms,
+            }) if *o == owner && *p == page => Some((self.address_of(idx), *perms)),
+            _ => None,
+        })
+    }
+
+    /// Every allocated frame and its use.
+    pub fn iter(&self) -> impl Iterator<Item = (PhysicalAddress, &FrameUse)> + '_ {
+        self.live()
+            .iter()
+            .enumerate()
+            .filter_map(|(idx, f)| f.as_ref().map(|u| (self.address_of(idx), u)))
+    }
+
+    /// User pages of `owner` as (frame, virtual address) pairs.
+    pub fn user_frames_of(
+        &self,
+        owner: ProcessId,
+    ) -> impl Iterator<Item = (PhysicalAddress, VirtualAddress)> + '_ {
+        self.live()
+            .iter()
+            .enumerate()
+            .filter_map(move |(idx, f)| match f {
+                Some(FrameUse::User { owner: o, page, .. }) if *o == owner => Some((
+                    self.address_of(idx),
+                    VirtualAddress::from_raw(*page as usize * PAGE_SIZE),
+                )),
+                _ => None,
+            })
+    }
+
+    /// Frees every user and page-table frame charged to `owner`; returns
+    /// how many were freed.
+    pub fn free_owned_by(&mut self, owner: ProcessId) -> usize {
+        let mut freed = 0;
+        for slot in self.live_mut().iter_mut() {
+            let owned = matches!(
+                slot,
+                Some(FrameUse::User { owner: o, .. } | FrameUse::PageTable { owner: o }) if *o == owner
+            );
+            if owned {
+                *slot = None;
+                freed += 1;
+            }
+        }
+        self.free += freed;
+        freed
+    }
+}

crates/domain/src/memory/frame/proofs.rs

@@ -0,0 +1,195 @@
+//! Bounded proofs over every reachable state of a small frame table.
+//! Each harness starts from an arbitrary *well-formed* table (free count
+//! matches the number of empty slots) and checks one operation.
+
+use super::*;
+use types::address::{PhysicalAddress, VirtualAddress};
+use types::id::{ProcessId, RegionId};
+use types::mapping::PagePerms;
+
+const N: usize = 4;
+const BASE: usize = 0x8400_0000;
+
+fn any_perms() -> PagePerms {
+    match kani::any::<u8>() % 3 {
+        0 => PagePerms::ReadOnly,
+        1 => PagePerms::ReadWrite,
+        _ => PagePerms::ReadExecute,
+    }
+}
+
+fn any_use() -> FrameUse {
+    // Small id ranges keep owner collisions likely, which is where the
+    // interesting cases are.
+    let owner = ProcessId::from_raw(kani::any::<u16>() % 3);
+    match kani::any::<u8>() % 3 {
+        0 => FrameUse::User {
+            owner,
+            page: kani::any::<u32>() % 4,
+            perms: any_perms(),
+        },
+        1 => FrameUse::PageTable { owner },
+        _ => FrameUse::Region {
+            region: RegionId::from_raw(kani::any::<u16>() % 2),
+        },
+    }
+}
+
+fn any_slot() -> Option<FrameUse> {
+    if kani::any() { Some(any_use()) } else { None }
+}
+
+fn any_table() -> FrameTable<N> {
+    let frames = [any_slot(), any_slot(), any_slot(), any_slot()];
+    let free = frames.iter().filter(|f| f.is_none()).count();
+    FrameTable {
+        base: PhysicalAddress::from_raw(BASE),
+        total: N,
+        frames,
+        free,
+    }
+}
+
+fn well_formed(t: &FrameTable<N>) -> bool {
+    t.free == t.frames[..t.total].iter().filter(|f| f.is_none()).count()
+}
+
+fn any_pa() -> PhysicalAddress {
+    // Anything from below the pool to past its end, aligned or not.
+    PhysicalAddress::from_raw(BASE - 4096 + kani::any::<usize>() % ((N + 2) * 4096))
+}
+
+#[kani::proof]
+#[kani::unwind(6)]
+fn alloc_only_hands_out_free_frames() {
+    let mut t = any_table();
+    let before = t.frames;
+    let usage = any_use();
+    match t.alloc(usage) {
+        Some(pa) => {
+            let idx = (pa.raw() - BASE) / PAGE_SIZE;
+            assert!(idx < N);
+            assert!(before[idx].is_none());
+            assert!(t.frames[idx] == Some(usage));
+            for i in 0..N {
+                if i != idx {
+                    assert!(t.frames[i] == before[i]);
+                }
+            }
+        }
+        None => {
+            assert!(before.iter().all(Option::is_some));
+            assert!(t.frames == before);
+        }
+    }
+    assert!(well_formed(&t));
+}
+
+#[kani::proof]
+#[kani::unwind(6)]
+fn free_releases_exactly_one_allocated_frame_or_nothing() {
+    let mut t = any_table();
+    let before = t.frames;
+    let pa = any_pa();
+    match t.free(pa) {
+        Some(usage) => {
+            let idx = (pa.raw() - BASE) / PAGE_SIZE;
+            assert!(pa.raw() % PAGE_SIZE == 0);
+            assert!(before[idx] == Some(usage));
+            assert!(t.frames[idx].is_none());
+            for i in 0..N {
+                if i != idx {
+                    assert!(t.frames[i] == before[i]);
+                }
+            }
+        }
+        None => assert!(t.frames == before),
+    }
+    assert!(well_formed(&t));
+}
+
+#[kani::proof]
+#[kani::unwind(6)]
+fn retag_never_allocates() {
+    let mut t = any_table();
+    let before = t.frames;
+    let pa = any_pa();
+    let usage = any_use();
+    let changed = t.retag(pa, usage);
+    for i in 0..N {
+        if before[i].is_none() {
+            assert!(t.frames[i].is_none());
+        }
+    }
+    if !changed {
+        assert!(t.frames == before);
+    }
+    assert!(well_formed(&t));
+}
+
+#[kani::proof]
+#[kani::unwind(6)]
+fn free_owned_by_spares_everyone_else() {
+    let mut t = any_table();
+    let before = t.frames;
+    let owner = ProcessId::from_raw(kani::any::<u16>() % 3);
+    t.free_owned_by(owner);
+    for i in 0..N {
+        let was_owned = matches!(
+            before[i],
+            Some(FrameUse::User { owner: o, .. } | FrameUse::PageTable { owner: o }) if o == owner
+        );
+        if was_owned {
+            assert!(t.frames[i].is_none());
+        } else {
+            assert!(t.frames[i] == before[i]);
+        }
+    }
+    assert!(well_formed(&t));
+}
+
+#[kani::proof]
+#[kani::unwind(6)]
+fn find_user_only_reports_the_owners_mapping() {
+    let t = any_table();
+    let owner = ProcessId::from_raw(kani::any::<u16>() % 3);
+    let va = VirtualAddress::from_raw(kani::any::<usize>() % (5 * 4096));
+    if let Some((pa, perms)) = t.find_user(owner, va) {
+        let idx = (pa.raw() - BASE) / PAGE_SIZE;
+        assert!(idx < N);
+        assert!(va.raw() % PAGE_SIZE == 0);
+        assert!(
+            t.frames[idx]
+                == Some(FrameUse::User {
+                    owner,
+                    page: (va.raw() / PAGE_SIZE) as u32,
+                    perms,
+                })
+        );
+    }
+}
+
+#[kani::proof]
+#[kani::unwind(6)]
+fn alloc_contiguous_only_claims_a_free_run() {
+    let mut t = any_table();
+    let before = t.frames;
+    let count = kani::any::<usize>() % (N + 2);
+    let region = RegionId::from_raw(1);
+    match t.alloc_contiguous(count, |_| FrameUse::Region { region }) {
+        Some(pa) => {
+            let start = (pa.raw() - BASE) / PAGE_SIZE;
+            assert!(count > 0 && start + count <= N);
+            for i in 0..N {
+                if i >= start && i < start + count {
+                    assert!(before[i].is_none());
+                    assert!(t.frames[i] == Some(FrameUse::Region { region }));
+                } else {
+                    assert!(t.frames[i] == before[i]);
+                }
+            }
+        }
+        None => assert!(t.frames == before),
+    }
+    assert!(well_formed(&t));
+}

crates/domain/src/memory/frame/tests.rs

@@ -0,0 +1,188 @@
+use super::*;
+use types::address::{PhysicalAddress, VirtualAddress};
+use types::id::{ProcessId, RegionId};
+use types::mapping::PagePerms;
+
+const BASE: usize = 0x8400_0000;
+
+fn table() -> FrameTable<8> {
+    FrameTable::new(PhysicalAddress::from_raw(BASE), 8)
+}
+
+fn pid(n: u16) -> ProcessId {
+    ProcessId::from_raw(n)
+}
+
+fn va(addr: usize) -> VirtualAddress {
+    VirtualAddress::from_raw(addr)
+}
+
+fn user(owner: u16, addr: usize) -> FrameUse {
+    FrameUse::user(pid(owner), va(addr), PagePerms::ReadWrite).unwrap()
+}
+
+#[test]
+fn new_table_has_every_frame_free() {
+    let t = table();
+    assert_eq!(t.free_count(), 8);
+    assert_eq!(t.capacity(), 8);
+}
+
+#[test]
+fn total_is_clamped_to_capacity() {
+    let t: FrameTable<4> = FrameTable::new(PhysicalAddress::from_raw(BASE), 100);
+    assert_eq!(t.free_count(), 4);
+}
+
+#[test]
+fn user_use_requires_page_aligned_va() {
+    assert!(FrameUse::user(pid(0), va(0x1234), PagePerms::ReadOnly).is_none());
+    assert!(FrameUse::user(pid(0), va(0x1000), PagePerms::ReadOnly).is_some());
+}
+
+#[test]
+fn alloc_hands_out_distinct_frames_inside_the_pool() {
+    let mut t = table();
+    let a = t.alloc(user(0, 0x1000)).unwrap();
+    let b = t.alloc(user(0, 0x2000)).unwrap();
+    assert_ne!(a, b);
+    for pa in [a, b] {
+        assert!(pa.raw() >= BASE && pa.raw() < BASE + 8 * 4096);
+        assert_eq!(pa.raw() % 4096, 0);
+    }
+    assert_eq!(t.free_count(), 6);
+}
+
+#[test]
+fn alloc_fails_when_exhausted() {
+    let mut t = table();
+    for i in 0..8 {
+        t.alloc(user(0, (i + 1) * 0x1000)).unwrap();
+    }
+    assert!(t.alloc(user(0, 0x9000)).is_none());
+}
+
+#[test]
+fn free_returns_the_frame_and_its_use() {
+    let mut t = table();
+    let pa = t.alloc(user(3, 0x5000)).unwrap();
+    assert_eq!(t.free(pa), Some(user(3, 0x5000)));
+    assert_eq!(t.free_count(), 8);
+}
+
+#[test]
+fn freeing_a_free_frame_is_rejected() {
+    let mut t = table();
+    let pa = t.alloc(user(0, 0x1000)).unwrap();
+    t.free(pa).unwrap();
+    assert_eq!(t.free(pa), None);
+    assert_eq!(t.free_count(), 8);
+}
+
+#[test]
+fn freeing_outside_the_pool_or_unaligned_is_rejected() {
+    let mut t = table();
+    t.alloc(user(0, 0x1000)).unwrap();
+    assert_eq!(t.free(PhysicalAddress::from_raw(BASE - 4096)), None);
+    assert_eq!(t.free(PhysicalAddress::from_raw(BASE + 8 * 4096)), None);
+    assert_eq!(t.free(PhysicalAddress::from_raw(BASE + 1)), None);
+    assert_eq!(t.free_count(), 7);
+}
+
+#[test]
+fn find_user_matches_owner_and_va() {
+    let mut t = table();
+    let pa = t.alloc(user(1, 0x3000)).unwrap();
+    assert_eq!(
+        t.find_user(pid(1), va(0x3000)),
+        Some((pa, PagePerms::ReadWrite))
+    );
+    assert_eq!(t.find_user(pid(2), va(0x3000)), None);
+    assert_eq!(t.find_user(pid(1), va(0x4000)), None);
+}
+
+#[test]
+fn retag_moves_a_frame_to_a_new_use() {
+    let mut t = table();
+    let pa = t.alloc(user(1, 0x3000)).unwrap();
+    assert!(t.retag(pa, user(2, 0x7000)));
+    assert_eq!(t.find_user(pid(1), va(0x3000)), None);
+    assert_eq!(t.find_user(pid(2), va(0x7000)).map(|(p, _)| p), Some(pa));
+}
+
+#[test]
+fn retag_of_a_free_frame_is_rejected() {
+    let mut t = table();
+    let pa = t.alloc(user(1, 0x3000)).unwrap();
+    t.free(pa);
+    assert!(!t.retag(pa, user(2, 0x7000)));
+    assert_eq!(t.free_count(), 8);
+}
+
+#[test]
+fn alloc_contiguous_returns_adjacent_frames() {
+    let mut t = table();
+    let base = t
+        .alloc_contiguous(3, |_| FrameUse::Region {
+            region: RegionId::from_raw(0),
+        })
+        .unwrap();
+    assert_eq!(t.free_count(), 5);
+    for i in 0..3 {
+        assert_eq!(
+            t.get(base.offset(i)),
+            Some(&FrameUse::Region {
+                region: RegionId::from_raw(0)
+            })
+        );
+    }
+}
+
+#[test]
+fn alloc_contiguous_fails_without_a_long_enough_run() {
+    let mut t: FrameTable<4> = FrameTable::new(PhysicalAddress::from_raw(BASE), 4);
+    let a = t.alloc(user(0, 0x1000)).unwrap();
+    let _b = t.alloc(user(0, 0x2000)).unwrap();
+    let _c = t.alloc(user(0, 0x3000)).unwrap();
+    t.free(a);
+    // free frames: 0 and 3 — no run of 2
+    assert!(
+        t.alloc_contiguous(2, |_| FrameUse::PageTable { owner: pid(0) })
+            .is_none()
+    );
+    assert_eq!(t.free_count(), 2);
+}
+
+#[test]
+fn free_owned_by_releases_only_that_processes_frames() {
+    let mut t = table();
+    t.alloc(user(1, 0x1000)).unwrap();
+    t.alloc(FrameUse::PageTable { owner: pid(1) }).unwrap();
+    let other = t.alloc(user(2, 0x1000)).unwrap();
+    let region = t
+        .alloc(FrameUse::Region {
+            region: RegionId::from_raw(1),
+        })
+        .unwrap();
+
+    assert_eq!(t.free_owned_by(pid(1)), 2);
+    assert_eq!(t.free_count(), 6);
+    assert!(t.get(other).is_some());
+    assert!(t.get(region).is_some());
+}
+
+#[test]
+fn user_frames_of_lists_mappings_of_one_process() {
+    let mut t = table();
+    t.alloc(user(1, 0x1000)).unwrap();
+    t.alloc(user(2, 0x2000)).unwrap();
+    t.alloc(user(1, 0x3000)).unwrap();
+    t.alloc(FrameUse::PageTable { owner: pid(1) }).unwrap();
+    let mut vas = [0usize; 4];
+    let mut n = 0;
+    for (_, v) in t.user_frames_of(pid(1)) {
+        vas[n] = v.raw();
+        n += 1;
+    }
+    assert_eq!(&vas[..n], &[0x1000, 0x3000]);
+}

crates/domain/src/memory/mod.rs

@@ -1,118 +1,210 @@
+use crate::{capability::CapRef, generations::SlotGenerations};
 use types::{
-    address::PhysicalAddress,
+    address::{PhysicalAddress, VirtualAddress},
     bounded::PageCount,
     generation::Generation,
     id::{ProcessId, RegionId},
+    mapping::PagePerms,
 };
 
-pub mod page_pool;
-pub mod process_memory;
+pub mod frame;
+pub mod quota;
+
+#[cfg(test)]
+#[path = "quota_tests.rs"]
+mod quota_tests;
 
 #[cfg(test)]
 #[path = "tests.rs"]
 mod tests;
 
-const MAX_REGIONS: usize = 256;
+pub const MAX_REGIONS: usize = if cfg!(kani) { 1 } else { 64 };
+pub const MAX_REGION_MAPPINGS: usize = if cfg!(kani) { 2 } else { 4 };
 
-pub struct MemoryRegion {
-    id: RegionId,
-    owner: ProcessId,
-    base: PhysicalAddress,
-    size: PageCount,
-    generation: Generation,
+/// Where a region's frames come from.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum RegionBacking {
+    /// Frames from the user pool, freed with the region.
+    Pool,
+    /// Device MMIO; never freed.
+    Device,
 }
 
-impl MemoryRegion {
-    pub fn new(
-        id: RegionId,
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct RegionMapping {
+    pub process: ProcessId,
+    pub va: VirtualAddress,
+    pub perms: PagePerms,
+    /// The capability the mapping was made through. Deleting that
+    /// capability removes the mapping; `None` for kernel-made mappings.
+    pub via: Option<CapRef>,
+}
+
+/// Physically contiguous memory that may be mapped into several address
+/// spaces. `owner` is charged for pool-backed frames.
+pub struct Region {
     owner: ProcessId,
+    backing: RegionBacking,
     base: PhysicalAddress,
-        size: PageCount,
-        generation: Generation,
+    pages: PageCount,
+    mappings: [Option<RegionMapping>; MAX_REGION_MAPPINGS],
+}
+
+impl Region {
+    pub fn new(
+        owner: ProcessId,
+        backing: RegionBacking,
+        base: PhysicalAddress,
+        pages: PageCount,
     ) -> Self {
         Self {
-            id,
             owner,
+            backing,
             base,
-            size,
-            generation,
+            pages,
+            mappings: [None; MAX_REGION_MAPPINGS],
         }
     }
 
-    pub fn id(&self) -> RegionId {
-        self.id
-    }
-
     pub fn owner(&self) -> ProcessId {
         self.owner
     }
 
+    pub fn backing(&self) -> RegionBacking {
+        self.backing
+    }
+
     pub fn base(&self) -> PhysicalAddress {
         self.base
     }
 
-    pub fn size(&self) -> PageCount {
-        self.size
+    pub fn pages(&self) -> PageCount {
+        self.pages
     }
 
-    pub fn generation(&self) -> &Generation {
-        &self.generation
+    pub fn mappings(&self) -> impl Iterator<Item = &RegionMapping> {
+        self.mappings.iter().flatten()
     }
 
-    pub fn revoke(&mut self) {
-        self.generation = self.generation.next();
+    /// Records that `mapping.process` maps this region. Each process maps a
+    /// region at most once.
+    pub fn add_mapping(&mut self, mapping: RegionMapping) -> bool {
+        if self.mappings().any(|m| m.process == mapping.process) {
+            return false;
+        }
+        match self.mappings.iter_mut().find(|m| m.is_none()) {
+            Some(slot) => {
+                *slot = Some(mapping);
+                true
+            }
+            None => false,
+        }
+    }
+
+    pub fn remove_mapping(&mut self, process: ProcessId) -> Option<RegionMapping> {
+        self.mappings
+            .iter_mut()
+            .find(|m| m.is_some_and(|m| m.process == process))?
+            .take()
+    }
+
+    /// Whether `va` falls inside this region's mapping in `process`.
+    pub fn covers(&self, process: ProcessId, va: VirtualAddress) -> bool {
+        let len = self.pages.value() as usize * frame::PAGE_SIZE;
+        self.mappings()
+            .any(|m| m.process == process && va.raw() >= m.va.raw() && va.raw() - m.va.raw() < len)
     }
 }
 
 pub struct RegionTable {
-    regions: [Option<MemoryRegion>; MAX_REGIONS],
+    regions: [Option<Region>; MAX_REGIONS],
+    generations: SlotGenerations<MAX_REGIONS>,
 }
 
 impl RegionTable {
     pub fn new() -> Self {
         Self {
             regions: [const { None }; MAX_REGIONS],
+            generations: SlotGenerations::new(),
         }
     }
 
-    pub fn insert(&mut self, region: MemoryRegion) -> Option<RegionId> {
-        let idx = self.regions.iter().position(|s| s.is_none())?;
-        let id = RegionId::from_raw(idx as u16);
-        self.regions[idx] = Some(region);
-        Some(id)
+    /// Generation capabilities to a live region must carry.
+    pub fn generation(&self, id: RegionId) -> Option<Generation> {
+        self.get(id)?;
+        self.generations.current(id.raw() as usize)
     }
 
-    pub fn get(&self, id: RegionId) -> Option<&MemoryRegion> {
-        self.regions.get(id.raw() as usize).and_then(|s| s.as_ref())
-    }
-
-    pub fn get_mut(&mut self, id: RegionId) -> Option<&mut MemoryRegion> {
-        self.regions.get_mut(id.raw() as usize).and_then(|s| s.as_mut())
-    }
-
-    pub fn remove(&mut self, id: RegionId) -> Option<MemoryRegion> {
-        self.regions.get_mut(id.raw() as usize).and_then(|s| s.take())
-    }
-
-    pub fn find_by_base(
-        &self,
-        owner: ProcessId,
-        base: PhysicalAddress,
-    ) -> Option<(RegionId, &MemoryRegion)> {
-        for (i, slot) in self.regions.iter().enumerate() {
-            if let Some(region) = slot {
-                if region.owner() == owner && region.base() == base {
-                    return Some((RegionId::from_raw(i as u16), region));
-                }
-            }
-        }
-        None
-    }
-
-    pub fn regions_for_process(&self, process: ProcessId) -> impl Iterator<Item = &MemoryRegion> {
+    fn free_slot(&self) -> Option<usize> {
         self.regions
             .iter()
-            .filter_map(|s| s.as_ref())
-            .filter(move |r| r.owner() == process)
+            .enumerate()
+            .position(|(i, r)| r.is_none() && self.generations.is_usable(i))
+    }
+
+    /// The id the next `insert` will return.
+    pub fn next_free_id(&self) -> Option<RegionId> {
+        let idx = self.free_slot()?;
+        Some(RegionId::from_raw(idx as u16))
+    }
+
+    pub fn insert(&mut self, region: Region) -> Option<RegionId> {
+        let idx = self.free_slot()?;
+        *self.regions.get_mut(idx)? = Some(region);
+        Some(RegionId::from_raw(idx as u16))
+    }
+
+    pub fn get(&self, id: RegionId) -> Option<&Region> {
+        self.regions.get(id.raw() as usize)?.as_ref()
+    }
+
+    pub fn get_mut(&mut self, id: RegionId) -> Option<&mut Region> {
+        self.regions.get_mut(id.raw() as usize)?.as_mut()
+    }
+
+    /// Removes the region; capabilities to it become invalid even if the
+    /// slot is later reused.
+    pub fn remove(&mut self, id: RegionId) -> Option<Region> {
+        let region = self.regions.get_mut(id.raw() as usize)?.take()?;
+        self.generations.advance(id.raw() as usize);
+        Some(region)
+    }
+
+    pub fn ids_owned_by(&self, owner: ProcessId) -> impl Iterator<Item = RegionId> + '_ {
+        self.regions.iter().enumerate().filter_map(move |(i, r)| {
+            r.as_ref()
+                .filter(|r| r.owner == owner)
+                .map(|_| RegionId::from_raw(i as u16))
+        })
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = (RegionId, &Region)> {
+        self.regions
+            .iter()
+            .enumerate()
+            .filter_map(|(i, r)| r.as_ref().map(|r| (RegionId::from_raw(i as u16), r)))
+    }
+
+    /// Every region, by id, so callers can drop a process's mappings.
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (RegionId, &mut Region)> {
+        self.regions
+            .iter_mut()
+            .enumerate()
+            .filter_map(|(i, r)| r.as_mut().map(|r| (RegionId::from_raw(i as u16), r)))
+    }
+
+    /// The region whose mapping in `process` covers `va`.
+    pub fn covering(&self, process: ProcessId, va: VirtualAddress) -> Option<RegionId> {
+        self.regions.iter().enumerate().find_map(|(i, r)| {
+            r.as_ref()
+                .filter(|r| r.covers(process, va))
+                .map(|_| RegionId::from_raw(i as u16))
+        })
+    }
+}
+
+impl Default for RegionTable {
+    fn default() -> Self {
+        Self::new()
     }
 }

crates/domain/src/memory/page_pool.rs

@@ -1,68 +0,0 @@
-use types::address::PhysicalAddress;
-
-const MAX_PAGES: usize = 16384;
-
-pub struct PagePool {
-    pages: [bool; MAX_PAGES],
-    base: PhysicalAddress,
-    total: usize,
-    free_count: usize,
-}
-
-impl PagePool {
-    pub fn new(base: PhysicalAddress, total_pages: usize) -> Self {
-        let mut pages = [false; MAX_PAGES];
-        for i in 0..total_pages {
-            pages[i] = true;
-        }
-        Self {
-            pages,
-            base,
-            total: total_pages,
-            free_count: total_pages,
-        }
-    }
-
-    pub fn allocate(&mut self, count: usize) -> Option<PhysicalAddress> {
-        let start = self.find_contiguous(count)?;
-        for i in start..start + count {
-            self.pages[i] = false;
-        }
-        self.free_count -= count;
-        Some(self.base.offset(start))
-    }
-
-    pub fn free(&mut self, addr: PhysicalAddress, count: usize) -> bool {
-        if addr.raw() < self.base.raw() {
-            return false;
-        }
-        let start = (addr.raw() - self.base.raw()) / 4096;
-        if start + count > self.total {
-            return false;
-        }
-        for i in start..start + count {
-            self.pages[i] = true;
-        }
-        self.free_count += count;
-        true
-    }
-
-    pub fn free_count(&self) -> usize {
-        self.free_count
-    }
-
-    fn find_contiguous(&self, count: usize) -> Option<usize> {
-        let mut run = 0;
-        for i in 0..self.total {
-            if self.pages[i] {
-                run += 1;
-                if run == count {
-                    return Some(i + 1 - count);
-                }
-            } else {
-                run = 0;
-            }
-        }
-        None
-    }
-}

crates/domain/src/memory/process_memory.rs

@@ -1,77 +0,0 @@
-use types::address::{PhysicalAddress, VirtualAddress};
-use types::id::ProcessId;
-
-use crate::error::KernelError;
-
-const USER_HEAP_START: usize = 0x40000;
-const PAGE_SIZE: usize = 4096;
-const MAX_ALLOCATIONS: usize = 16;
-
-pub struct ProcessMemory {
-    process: ProcessId,
-    page_count: usize,
-    limit: usize,
-    next_heap_va: usize,
-    allocations: [(PhysicalAddress, usize); MAX_ALLOCATIONS],
-    alloc_count: usize,
-}
-
-impl ProcessMemory {
-    pub const DEFAULT_PAGE_LIMIT: usize = 1024;
-
-    pub fn new(process: ProcessId, limit: usize) -> Self {
-        Self {
-            process,
-            page_count: 0,
-            limit,
-            next_heap_va: USER_HEAP_START,
-            allocations: [(PhysicalAddress::from_raw(0), 0); MAX_ALLOCATIONS],
-            alloc_count: 0,
-        }
-    }
-
-    pub fn alloc_user_va(&mut self, pages: usize) -> VirtualAddress {
-        let va = self.next_heap_va;
-        self.next_heap_va += pages * PAGE_SIZE;
-        VirtualAddress::from_raw(va)
-    }
-
-    pub fn record_allocation(&mut self, pa: PhysicalAddress, count: usize) {
-        if self.alloc_count < MAX_ALLOCATIONS {
-            self.allocations[self.alloc_count] = (pa, count);
-            self.alloc_count += 1;
-        }
-    }
-
-    pub fn allocations(&self) -> &[(PhysicalAddress, usize)] {
-        &self.allocations[..self.alloc_count]
-    }
-
-    pub fn process(&self) -> ProcessId {
-        self.process
-    }
-
-    pub fn page_count(&self) -> usize {
-        self.page_count
-    }
-
-    pub fn limit(&self) -> usize {
-        self.limit
-    }
-
-    pub fn grant(&mut self, count: usize) -> Result<(), KernelError> {
-        if self.page_count + count > self.limit {
-            return Err(KernelError::OutOfMemory);
-        }
-        self.page_count += count;
-        Ok(())
-    }
-
-    pub fn release(&mut self, count: usize) -> Result<(), KernelError> {
-        if count > self.page_count {
-            return Err(KernelError::OutOfMemory);
-        }
-        self.page_count -= count;
-        Ok(())
-    }
-}

crates/domain/src/memory/quota.rs

@@ -0,0 +1,57 @@
+/// Per-process page budget. Every frame charged to a process (user pages
+/// and its page tables) counts against it.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Quota {
+    used: usize,
+    limit: usize,
+}
+
+impl Quota {
+    pub const DEFAULT_LIMIT: usize = 1024;
+
+    pub const fn new(limit: usize) -> Self {
+        Self { used: 0, limit }
+    }
+
+    pub fn used(&self) -> usize {
+        self.used
+    }
+
+    pub fn limit(&self) -> usize {
+        self.limit
+    }
+
+    pub fn charge(&mut self, pages: usize) -> bool {
+        match self.used.checked_add(pages) {
+            Some(total) if total <= self.limit => {
+                self.used = total;
+                true
+            }
+            _ => false,
+        }
+    }
+
+    pub fn uncharge(&mut self, pages: usize) -> bool {
+        match self.used.checked_sub(pages) {
+            Some(rest) => {
+                self.used = rest;
+                true
+            }
+            None => false,
+        }
+    }
+
+    pub fn set_limit(&mut self, limit: usize) -> bool {
+        if limit < self.used {
+            return false;
+        }
+        self.limit = limit;
+        true
+    }
+}
+
+impl Default for Quota {
+    fn default() -> Self {
+        Self::new(Self::DEFAULT_LIMIT)
+    }
+}

crates/domain/src/memory/quota_tests.rs

@@ -0,0 +1,37 @@
+use super::quota::Quota;
+
+#[test]
+fn charge_within_limit_succeeds() {
+    let mut q = Quota::new(4);
+    assert!(q.charge(3));
+    assert_eq!(q.used(), 3);
+    assert!(q.charge(1));
+    assert_eq!(q.used(), 4);
+}
+
+#[test]
+fn charge_past_limit_fails_and_changes_nothing() {
+    let mut q = Quota::new(4);
+    q.charge(3);
+    assert!(!q.charge(2));
+    assert_eq!(q.used(), 3);
+}
+
+#[test]
+fn uncharge_cannot_underflow() {
+    let mut q = Quota::new(4);
+    q.charge(1);
+    assert!(!q.uncharge(2));
+    assert_eq!(q.used(), 1);
+    assert!(q.uncharge(1));
+    assert_eq!(q.used(), 0);
+}
+
+#[test]
+fn limit_can_be_raised_but_not_below_usage() {
+    let mut q = Quota::new(4);
+    q.charge(3);
+    assert!(!q.set_limit(2));
+    assert!(q.set_limit(10));
+    assert!(q.charge(7));
+}

crates/domain/src/memory/tests.rs

@@ -1,207 +1,118 @@
-use super::page_pool::PagePool;
-use super::process_memory::ProcessMemory;
 use super::*;
-use types::address::PhysicalAddress;
+use types::address::{PhysicalAddress, VirtualAddress};
 use types::bounded::PageCount;
-use types::generation::Generation;
 use types::id::{ProcessId, RegionId};
+use types::mapping::PagePerms;
 
-fn base() -> PhysicalAddress {
-    PhysicalAddress::from_raw(0x8000_0000)
+fn pid(n: u16) -> ProcessId {
+    ProcessId::from_raw(n)
 }
 
-fn process(id: u16) -> ProcessId {
-    ProcessId::from_raw(id)
+fn va(addr: usize) -> VirtualAddress {
+    VirtualAddress::from_raw(addr)
 }
 
-fn pages(n: u16) -> PageCount {
-    PageCount::new(n).unwrap()
+fn pool_region(owner: u16, pages: u16) -> Region {
+    Region::new(
+        pid(owner),
+        RegionBacking::Pool,
+        PhysicalAddress::from_raw(0x8400_0000),
+        PageCount::new(pages).unwrap(),
+    )
 }
 
-// --- PagePool tests ---
-
-#[test]
-fn new_pool_has_all_pages_free() {
-    let pool = PagePool::new(base(), 100);
-    assert_eq!(pool.free_count(), 100);
+fn mapping(process: u16, addr: usize) -> RegionMapping {
+    RegionMapping {
+        process: pid(process),
+        va: va(addr),
+        perms: PagePerms::ReadWrite,
+        via: None,
+    }
 }
 
 #[test]
-fn allocate_reduces_free_count() {
-    let mut pool = PagePool::new(base(), 100);
-    pool.allocate(10).unwrap();
-    assert_eq!(pool.free_count(), 90);
+fn new_region_has_no_mappings() {
+    let r = pool_region(0, 4);
+    assert_eq!(r.mappings().count(), 0);
+    assert_eq!(r.owner(), pid(0));
+    assert_eq!(r.backing(), RegionBacking::Pool);
 }
 
 #[test]
-fn allocate_returns_base_aligned_address() {
-    let mut pool = PagePool::new(base(), 100);
-    let addr = pool.allocate(1).unwrap();
-    assert_eq!(addr, base());
+fn a_process_maps_a_region_at_most_once() {
+    let mut r = pool_region(0, 4);
+    assert!(r.add_mapping(mapping(1, 0x30000)));
+    assert!(!r.add_mapping(mapping(1, 0x50000)));
+    assert!(r.add_mapping(mapping(2, 0x30000)));
+    assert_eq!(r.mappings().count(), 2);
 }
 
 #[test]
-fn allocate_sequential_returns_contiguous() {
-    let mut pool = PagePool::new(base(), 100);
-    let a = pool.allocate(4).unwrap();
-    let b = pool.allocate(4).unwrap();
-    assert_eq!(a, base());
-    assert_eq!(b, base().offset(4));
+fn mapping_slots_are_bounded() {
+    let mut r = pool_region(0, 1);
+    for p in 0..MAX_REGION_MAPPINGS as u16 {
+        assert!(r.add_mapping(mapping(p, 0x30000)));
+    }
+    assert!(!r.add_mapping(mapping(99, 0x30000)));
 }
 
 #[test]
-fn allocate_too_many_returns_none() {
-    let mut pool = PagePool::new(base(), 10);
-    assert!(pool.allocate(11).is_none());
+fn remove_mapping_returns_it() {
+    let mut r = pool_region(0, 4);
+    r.add_mapping(mapping(1, 0x30000));
+    assert_eq!(r.remove_mapping(pid(1)), Some(mapping(1, 0x30000)));
+    assert_eq!(r.remove_mapping(pid(1)), None);
 }
 
 #[test]
-fn free_then_reallocate() {
-    let mut pool = PagePool::new(base(), 10);
-    let addr = pool.allocate(5).unwrap();
-    assert_eq!(pool.free_count(), 5);
-    assert!(pool.free(addr, 5));
-    assert_eq!(pool.free_count(), 10);
-    let addr2 = pool.allocate(5).unwrap();
-    assert_eq!(addr2, base());
+fn covers_checks_every_page_of_a_mapping() {
+    let mut r = pool_region(0, 4);
+    r.add_mapping(mapping(1, 0x30000));
+    assert!(r.covers(pid(1), va(0x30000)));
+    assert!(r.covers(pid(1), va(0x33000)));
+    assert!(!r.covers(pid(1), va(0x34000)));
+    assert!(!r.covers(pid(1), va(0x2F000)));
+    assert!(!r.covers(pid(2), va(0x30000)));
 }
 
 #[test]
-fn free_out_of_range_returns_false() {
-    let mut pool = PagePool::new(base(), 10);
-    assert!(!pool.free(PhysicalAddress::from_raw(0), 1));
+fn region_table_insert_get_remove() {
+    let mut t = RegionTable::new();
+    let id = t.insert(pool_region(0, 2)).unwrap();
+    assert_eq!(t.get(id).map(|r| r.owner()), Some(pid(0)));
+    assert!(t.remove(id).is_some());
+    assert!(t.get(id).is_none());
 }
 
 #[test]
-fn allocate_fragmented_finds_gap() {
-    let mut pool = PagePool::new(base(), 10);
-    let a = pool.allocate(3).unwrap();
-    let _b = pool.allocate(3).unwrap();
-    let _c = pool.allocate(3).unwrap();
-    pool.free(a, 3);
-    // now pages 0-2 are free, 3-8 allocated, 9 free
-    // asking for 3 contiguous should find 0-2
-    let d = pool.allocate(3).unwrap();
-    assert_eq!(d, base());
+fn region_table_is_bounded() {
+    let mut t = RegionTable::new();
+    for _ in 0..MAX_REGIONS {
+        assert!(t.insert(pool_region(0, 1)).is_some());
+    }
+    assert!(t.insert(pool_region(0, 1)).is_none());
 }
 
 #[test]
-fn allocate_exact_remaining() {
-    let mut pool = PagePool::new(base(), 5);
-    let addr = pool.allocate(5).unwrap();
-    assert_eq!(addr, base());
-    assert_eq!(pool.free_count(), 0);
-    assert!(pool.allocate(1).is_none());
+fn region_table_finds_regions_owned_by_a_process() {
+    let mut t = RegionTable::new();
+    let a = t.insert(pool_region(1, 1)).unwrap();
+    t.insert(pool_region(2, 1)).unwrap();
+    let c = t.insert(pool_region(1, 1)).unwrap();
+    let mut ids = [RegionId::from_raw(u16::MAX); 4];
+    let mut n = 0;
+    for id in t.ids_owned_by(pid(1)) {
+        ids[n] = id;
+        n += 1;
     }
-
-// --- ProcessMemory tests ---
-
-#[test]
-fn new_process_memory_has_zero_pages() {
-    let pm = ProcessMemory::new(process(0), 100);
-    assert_eq!(pm.page_count(), 0);
-    assert_eq!(pm.limit(), 100);
+    assert_eq!(&ids[..n], &[a, c]);
 }
 
 #[test]
-fn grant_pages_within_limit() {
-    let mut pm = ProcessMemory::new(process(0), 100);
-    assert!(pm.grant(10).is_ok());
-    assert_eq!(pm.page_count(), 10);
-}
-
-#[test]
-fn grant_pages_exceeding_limit_fails() {
-    let mut pm = ProcessMemory::new(process(0), 10);
-    assert!(pm.grant(11).is_err());
-    assert_eq!(pm.page_count(), 0);
-}
-
-#[test]
-fn release_pages_reduces_count() {
-    let mut pm = ProcessMemory::new(process(0), 100);
-    pm.grant(20).unwrap();
-    assert!(pm.release(5).is_ok());
-    assert_eq!(pm.page_count(), 15);
-}
-
-#[test]
-fn release_more_than_owned_fails() {
-    let mut pm = ProcessMemory::new(process(0), 100);
-    pm.grant(5).unwrap();
-    assert!(pm.release(10).is_err());
-    assert_eq!(pm.page_count(), 5);
-}
-
-#[test]
-fn grant_up_to_exact_limit() {
-    let mut pm = ProcessMemory::new(process(0), 10);
-    pm.grant(10).unwrap();
-    assert!(pm.grant(1).is_err());
-}
-
-// --- MemoryRegion tests ---
-
-#[test]
-fn memory_region_construction_and_accessors() {
-    let region = MemoryRegion::new(
-        RegionId::from_raw(1),
-        process(0),
-        base(),
-        pages(4),
-        Generation::initial(),
-    );
-    assert_eq!(region.id(), RegionId::from_raw(1));
-    assert_eq!(region.owner(), process(0));
-    assert_eq!(region.base(), base());
-    assert_eq!(region.size(), pages(4));
-    assert_eq!(region.generation(), &Generation::initial());
-}
-
-// --- RegionTable tests ---
-
-#[test]
-fn region_table_insert_and_get() {
-    let mut table = RegionTable::new();
-    let id = table.insert(MemoryRegion::new(
-        RegionId::from_raw(0),
-        process(0),
-        base(),
-        pages(4),
-        Generation::initial(),
-    ));
-    assert!(id.is_some());
-    let rid = id.unwrap();
-    assert!(table.get(rid).is_some());
-}
-
-#[test]
-fn region_table_remove() {
-    let mut table = RegionTable::new();
-    let id = table.insert(MemoryRegion::new(
-        RegionId::from_raw(0),
-        process(0),
-        base(),
-        pages(4),
-        Generation::initial(),
-    )).unwrap();
-    let removed = table.remove(id);
-    assert!(removed.is_some());
-    assert!(table.get(id).is_none());
-}
-
-#[test]
-fn region_table_regions_for_process() {
-    let mut table = RegionTable::new();
-    table.insert(MemoryRegion::new(
-        RegionId::from_raw(0), process(0), base(), pages(4), Generation::initial(),
-    ));
-    table.insert(MemoryRegion::new(
-        RegionId::from_raw(1), process(1), base(), pages(4), Generation::initial(),
-    ));
-    table.insert(MemoryRegion::new(
-        RegionId::from_raw(2), process(0), base(), pages(2), Generation::initial(),
-    ));
-    assert_eq!(table.regions_for_process(process(0)).count(), 2);
-    assert_eq!(table.regions_for_process(process(1)).count(), 1);
+fn region_table_finds_mapping_covering_a_va() {
+    let mut t = RegionTable::new();
+    let id = t.insert(pool_region(1, 2)).unwrap();
+    t.get_mut(id).unwrap().add_mapping(mapping(3, 0x30000));
+    assert_eq!(t.covering(pid(3), va(0x31000)), Some(id));
+    assert_eq!(t.covering(pid(3), va(0x32000)), None);
 }

crates/domain/src/message/mod.rs

@@ -5,72 +5,38 @@ use types::bounded::CapSlot;
 mod tests;
 
 pub const MAX_MESSAGE_WORDS: usize = 4;
-pub const MAX_CAP_TRANSFERS: usize = 4;
 
+/// Four words and at most one capability (named by the sender's slot).
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct Message {
     words: [usize; MAX_MESSAGE_WORDS],
-    caps: [Option<CapSlot>; MAX_CAP_TRANSFERS],
+    cap: Option<CapSlot>,
 }
 
 impl Message {
     pub fn empty() -> Self {
-        Self {
-            words: [0; MAX_MESSAGE_WORDS],
-            caps: [None; MAX_CAP_TRANSFERS],
-        }
+        Self::from_words([0; MAX_MESSAGE_WORDS])
     }
 
     pub fn from_words(words: [usize; MAX_MESSAGE_WORDS]) -> Self {
-        Self {
-            words,
-            caps: [None; MAX_CAP_TRANSFERS],
+        Self { words, cap: None }
     }
+
+    pub fn with_cap(mut self, slot: CapSlot) -> Self {
+        self.cap = Some(slot);
+        self
     }
 
     pub fn words(&self) -> &[usize; MAX_MESSAGE_WORDS] {
         &self.words
     }
 
+    /// Word `index`, or 0 past the end.
     pub fn word(&self, index: usize) -> usize {
-        self.words[index]
+        self.words.get(index).copied().unwrap_or(0)
     }
 
-    pub fn caps(&self) -> &[Option<CapSlot>; MAX_CAP_TRANSFERS] {
-        &self.caps
-    }
-
-    pub fn cap(&self, index: usize) -> Option<CapSlot> {
-        self.caps[index]
-    }
-
-    pub fn builder() -> MessageBuilder {
-        MessageBuilder {
-            message: Message::empty(),
-        }
-    }
-}
-
-pub struct MessageBuilder {
-    message: Message,
-}
-
-impl MessageBuilder {
-    pub fn word(mut self, index: usize, value: usize) -> Self {
-        self.message.words[index] = value;
-        self
-    }
-
-    pub fn words(mut self, words: [usize; MAX_MESSAGE_WORDS]) -> Self {
-        self.message.words = words;
-        self
-    }
-
-    pub fn cap(mut self, index: usize, slot: CapSlot) -> Self {
-        self.message.caps[index] = Some(slot);
-        self
-    }
-
-    pub fn build(self) -> Message {
-        self.message
+    pub fn cap(&self) -> Option<CapSlot> {
+        self.cap
     }
 }

crates/domain/src/message/tests.rs

@@ -1,86 +1,23 @@
 use super::*;
 use types::bounded::CapSlot;
 
-fn slot(n: u8) -> CapSlot {
-    CapSlot::new(n).unwrap()
-}
-
-// --- Construction ---
-
 #[test]
-fn empty_message_has_zeroed_words_and_no_caps() {
+fn empty_message_has_zeroed_words_and_no_cap() {
     let msg = Message::empty();
     assert_eq!(msg.words(), &[0; MAX_MESSAGE_WORDS]);
-    for i in 0..MAX_CAP_TRANSFERS {
-        assert!(msg.cap(i).is_none());
-    }
+    assert!(msg.cap().is_none());
 }
 
 #[test]
-fn from_words_sets_words_and_no_caps() {
+fn from_words_keeps_every_word() {
     let msg = Message::from_words([10, 20, 30, 40]);
-    assert_eq!(msg.word(0), 10);
-    assert_eq!(msg.word(1), 20);
-    assert_eq!(msg.word(2), 30);
-    assert_eq!(msg.word(3), 40);
-    assert!(msg.cap(0).is_none());
-}
-
-// --- Accessors ---
-
-#[test]
-fn words_returns_full_array() {
-    let msg = Message::from_words([1, 2, 3, 4]);
-    assert_eq!(msg.words(), &[1, 2, 3, 4]);
+    assert_eq!(msg.words(), &[10, 20, 30, 40]);
+    assert!(msg.cap().is_none());
 }
 
 #[test]
-fn caps_returns_full_array() {
-    let msg = Message::empty();
-    assert_eq!(msg.caps(), &[None; MAX_CAP_TRANSFERS]);
-}
-
-// --- Builder ---
-
-#[test]
-fn builder_sets_individual_words() {
-    let msg = Message::builder()
-        .word(0, 42)
-        .word(2, 99)
-        .build();
-    assert_eq!(msg.word(0), 42);
-    assert_eq!(msg.word(1), 0);
-    assert_eq!(msg.word(2), 99);
-    assert_eq!(msg.word(3), 0);
-}
-
-#[test]
-fn builder_sets_caps() {
-    let msg = Message::builder()
-        .cap(0, slot(5))
-        .cap(1, slot(10))
-        .build();
-    assert_eq!(msg.cap(0), Some(slot(5)));
-    assert_eq!(msg.cap(1), Some(slot(10)));
-    assert!(msg.cap(2).is_none());
-}
-
-#[test]
-fn builder_sets_words_and_caps_together() {
-    let msg = Message::builder()
-        .word(0, 100)
-        .word(1, 200)
-        .cap(0, slot(3))
-        .build();
-    assert_eq!(msg.word(0), 100);
-    assert_eq!(msg.word(1), 200);
-    assert_eq!(msg.cap(0), Some(slot(3)));
-}
-
-#[test]
-fn builder_with_all_words() {
-    let msg = Message::builder()
-        .words([11, 22, 33, 44])
-        .build();
-    assert_eq!(msg.words(), &[11, 22, 33, 44]);
+fn with_cap_attaches_one_capability() {
+    let msg = Message::from_words([1, 2, 3, 4]).with_cap(CapSlot::new(5).unwrap());
+    assert_eq!(msg.cap(), CapSlot::new(5));
+    assert_eq!(msg.word(3), 4);
 }

crates/domain/src/notification/mod.rs

@@ -0,0 +1,192 @@
+//! Asynchronous signals: a word of bits, a FIFO of waiters and at most one
+//! bound thread. See docs/ipc.md.
+
+use types::{
+    badge::Badge,
+    generation::Generation,
+    id::{NotificationId, ProcessId, ThreadId},
+};
+
+use crate::{endpoint::wait_queue::WaitQueue, generations::SlotGenerations};
+
+#[cfg(test)]
+#[path = "tests.rs"]
+mod tests;
+
+#[cfg(kani)]
+#[path = "proofs.rs"]
+mod proofs;
+
+pub const MAX_NOTIFICATIONS: usize = if cfg!(kani) { 1 } else { 128 };
+
+/// What the kernel must do after a signal.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SignalEffect {
+    /// Wake this blocked `Wait`er with these bits.
+    WakeWaiter(ThreadId, usize),
+    /// Wake the bound thread out of its `Receive` with these bits.
+    WakeBound(ThreadId, usize),
+    /// Nobody to wake; the bits were stored.
+    Stored,
+}
+
+pub struct Notification {
+    id: NotificationId,
+    owner: ProcessId,
+    bits: usize,
+    waiters: WaitQueue,
+    bound: Option<ThreadId>,
+}
+
+impl Notification {
+    pub fn new(id: NotificationId, owner: ProcessId) -> Self {
+        Self {
+            id,
+            owner,
+            bits: 0,
+            waiters: WaitQueue::new(),
+            bound: None,
+        }
+    }
+
+    pub fn id(&self) -> NotificationId {
+        self.id
+    }
+
+    pub fn owner(&self) -> ProcessId {
+        self.owner
+    }
+
+    pub fn bound(&self) -> Option<ThreadId> {
+        self.bound
+    }
+
+    /// Delivers a signal. `bound_is_receiving` says whether the bound
+    /// thread is currently blocked in `Receive` and can be woken.
+    pub fn signal(&mut self, badge: Badge, bound_is_receiving: bool) -> SignalEffect {
+        let bits = if badge.is_none() { 1 } else { badge.raw() };
+        if let Some(waiter) = self.waiters.pop() {
+            return SignalEffect::WakeWaiter(waiter, bits);
+        }
+        if let (Some(bound), true) = (self.bound, bound_is_receiving) {
+            return SignalEffect::WakeBound(bound, bits);
+        }
+        self.bits |= bits;
+        SignalEffect::Stored
+    }
+
+    /// Returns and clears the pending bits.
+    pub fn take_bits(&mut self) -> usize {
+        core::mem::take(&mut self.bits)
+    }
+
+    pub fn has_bits(&self) -> bool {
+        self.bits != 0
+    }
+
+    pub fn waiters(&self) -> impl Iterator<Item = ThreadId> + '_ {
+        self.waiters.iter()
+    }
+
+    pub fn is_waiter(&self, thread: ThreadId) -> bool {
+        self.waiters.contains(thread)
+    }
+
+    pub fn add_waiter(&mut self, thread: ThreadId) -> bool {
+        self.waiters.push(thread).is_some()
+    }
+
+    pub fn bind(&mut self, thread: ThreadId) -> bool {
+        if self.bound.is_some() {
+            return false;
+        }
+        self.bound = Some(thread);
+        true
+    }
+
+    pub fn unbind(&mut self, thread: ThreadId) {
+        if self.bound == Some(thread) {
+            self.bound = None;
+        }
+    }
+
+    /// Forgets `thread` as waiter and as bound thread.
+    pub fn remove_thread(&mut self, thread: ThreadId) {
+        self.waiters.remove_thread(thread);
+        self.unbind(thread);
+    }
+
+    /// Drains every waiter, e.g. when the notification is destroyed.
+    pub fn pop_waiter(&mut self) -> Option<ThreadId> {
+        self.waiters.pop()
+    }
+}
+
+pub struct NotificationTable {
+    slots: [Option<Notification>; MAX_NOTIFICATIONS],
+    generations: SlotGenerations<MAX_NOTIFICATIONS>,
+}
+
+impl NotificationTable {
+    pub fn new() -> Self {
+        Self {
+            slots: [const { None }; MAX_NOTIFICATIONS],
+            generations: SlotGenerations::new(),
+        }
+    }
+
+    pub fn create(&mut self, owner: ProcessId) -> Option<NotificationId> {
+        let generations = &self.generations;
+        let (idx, slot) = self
+            .slots
+            .iter_mut()
+            .enumerate()
+            .find(|(i, s)| s.is_none() && generations.is_usable(*i))?;
+        let id = NotificationId::from_raw(idx as u16);
+        *slot = Some(Notification::new(id, owner));
+        Some(id)
+    }
+
+    pub fn get(&self, id: NotificationId) -> Option<&Notification> {
+        self.slots.get(id.raw() as usize)?.as_ref()
+    }
+
+    pub fn get_mut(&mut self, id: NotificationId) -> Option<&mut Notification> {
+        self.slots.get_mut(id.raw() as usize)?.as_mut()
+    }
+
+    pub fn generation(&self, id: NotificationId) -> Option<Generation> {
+        self.get(id)?;
+        self.generations.current(id.raw() as usize)
+    }
+
+    pub fn destroy(&mut self, id: NotificationId) -> Option<Notification> {
+        let n = self.slots.get_mut(id.raw() as usize)?.take()?;
+        self.generations.advance(id.raw() as usize);
+        Some(n)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = &Notification> {
+        self.slots.iter().flatten()
+    }
+
+    pub fn ids_owned_by(&self, owner: ProcessId) -> impl Iterator<Item = NotificationId> + '_ {
+        self.slots
+            .iter()
+            .flatten()
+            .filter(move |n| n.owner == owner)
+            .map(|n| n.id)
+    }
+
+    pub fn remove_thread_from_all(&mut self, thread: ThreadId) {
+        for n in self.slots.iter_mut().flatten() {
+            n.remove_thread(thread);
+        }
+    }
+}
+
+impl Default for NotificationTable {
+    fn default() -> Self {
+        Self::new()
+    }
+}

crates/domain/src/notification/proofs.rs

@@ -0,0 +1,43 @@
+//! Signals are never lost: every signal either wakes exactly one thread
+//! with its bits, or leaves those bits set for the next `Wait`.
+
+use super::*;
+use types::badge::Badge;
+use types::id::{NotificationId, ProcessId, ThreadId};
+
+#[kani::proof]
+#[kani::unwind(5)]
+fn a_signal_is_delivered_or_stored() {
+    let mut n = Notification::new(NotificationId::from_raw(0), ProcessId::from_raw(0));
+    n.bits = kani::any();
+    if kani::any() {
+        n.add_waiter(ThreadId::from_raw(kani::any::<u16>() % 4));
+    }
+    if kani::any() {
+        n.bind(ThreadId::from_raw(kani::any::<u16>() % 4));
+    }
+    let before = n.bits;
+    let badge = Badge::new(kani::any());
+    let expected = if badge.is_none() { 1 } else { badge.raw() };
+
+    match n.signal(badge, kani::any()) {
+        SignalEffect::WakeWaiter(_, bits) | SignalEffect::WakeBound(_, bits) => {
+            assert!(bits == expected);
+            assert!(n.bits == before, "woken signals are not also stored");
+        }
+        SignalEffect::Stored => {
+            assert!(n.bits == before | expected);
+            assert!(n.bits & expected == expected);
+        }
+    }
+}
+
+#[kani::proof]
+#[kani::unwind(5)]
+fn take_bits_returns_everything_and_clears() {
+    let mut n = Notification::new(NotificationId::from_raw(0), ProcessId::from_raw(0));
+    let bits: usize = kani::any();
+    n.bits = bits;
+    assert!(n.take_bits() == bits);
+    assert!(n.bits == 0);
+}

crates/domain/src/notification/tests.rs

@@ -0,0 +1,116 @@
+use super::*;
+use types::badge::Badge;
+use types::id::{NotificationId, ProcessId, ThreadId};
+
+fn ntfn() -> Notification {
+    Notification::new(NotificationId::from_raw(0), ProcessId::from_raw(0))
+}
+
+fn t(n: u16) -> ThreadId {
+    ThreadId::from_raw(n)
+}
+
+#[test]
+fn signal_with_nobody_waiting_stores_the_badge() {
+    let mut n = ntfn();
+    assert_eq!(n.signal(Badge::new(0b100), false), SignalEffect::Stored);
+    assert_eq!(n.signal(Badge::new(0b001), false), SignalEffect::Stored);
+    assert_eq!(n.take_bits(), 0b101);
+    assert_eq!(n.take_bits(), 0, "taking clears");
+}
+
+#[test]
+fn unbadged_signal_sets_bit_zero() {
+    let mut n = ntfn();
+    n.signal(Badge::NONE, false);
+    assert_eq!(n.take_bits(), 1);
+}
+
+#[test]
+fn signal_wakes_the_first_waiter_with_its_badge() {
+    let mut n = ntfn();
+    assert!(n.add_waiter(t(1)));
+    assert!(n.add_waiter(t(2)));
+    assert_eq!(
+        n.signal(Badge::new(8), false),
+        SignalEffect::WakeWaiter(t(1), 8)
+    );
+    assert_eq!(n.take_bits(), 0, "delivered bits are not also stored");
+    assert_eq!(
+        n.signal(Badge::new(4), false),
+        SignalEffect::WakeWaiter(t(2), 4)
+    );
+}
+
+#[test]
+fn signal_wakes_a_receiving_bound_thread_when_no_waiter() {
+    let mut n = ntfn();
+    assert!(n.bind(t(5)));
+    assert_eq!(
+        n.signal(Badge::new(2), true),
+        SignalEffect::WakeBound(t(5), 2)
+    );
+    assert_eq!(n.signal(Badge::new(2), false), SignalEffect::Stored);
+}
+
+#[test]
+fn waiters_take_priority_over_the_bound_thread() {
+    let mut n = ntfn();
+    n.bind(t(5));
+    n.add_waiter(t(1));
+    assert_eq!(
+        n.signal(Badge::new(2), true),
+        SignalEffect::WakeWaiter(t(1), 2)
+    );
+}
+
+#[test]
+fn only_one_thread_can_be_bound() {
+    let mut n = ntfn();
+    assert!(n.bind(t(1)));
+    assert!(!n.bind(t(2)));
+    n.unbind(t(1));
+    assert!(n.bind(t(2)));
+}
+
+#[test]
+fn removed_waiter_is_not_woken() {
+    let mut n = ntfn();
+    n.add_waiter(t(1));
+    n.remove_thread(t(1));
+    assert_eq!(n.signal(Badge::new(1), false), SignalEffect::Stored);
+}
+
+#[test]
+fn remove_thread_also_unbinds() {
+    let mut n = ntfn();
+    n.bind(t(1));
+    n.remove_thread(t(1));
+    assert_eq!(n.bound(), None);
+}
+
+#[test]
+fn table_generations_follow_slot_reuse() {
+    let mut table = NotificationTable::new();
+    let owner = ProcessId::from_raw(3);
+    let id = table.create(owner).unwrap();
+    let g = table.generation(id).unwrap();
+    assert!(table.destroy(id).is_some());
+    assert_eq!(table.generation(id), None);
+    let again = table.create(owner).unwrap();
+    assert_eq!(again, id);
+    assert!(!g.is_valid_against(&table.generation(again).unwrap()));
+}
+
+#[test]
+fn table_lists_notifications_by_owner() {
+    let mut table = NotificationTable::new();
+    let a = table.create(ProcessId::from_raw(1)).unwrap();
+    table.create(ProcessId::from_raw(2)).unwrap();
+    let mut n = 0;
+    for id in table.ids_owned_by(ProcessId::from_raw(1)) {
+        assert_eq!(id, a);
+        n += 1;
+    }
+    assert_eq!(n, 1);
+}

crates/domain/src/process/mod.rs

@@ -1,16 +1,17 @@
 use types::{
     bounded::CapSlot,
+    generation::Generation,
     id::{ProcessId, ThreadId},
 };
 
-use crate::{capability::CapabilityTable, error::KernelError};
+use crate::{capability::CapabilityTable, error::KernelError, generations::SlotGenerations};
 
 #[cfg(test)]
 #[path = "tests.rs"]
 mod tests;
 
-pub const MAX_THREADS_PER_PROCESS: usize = 4;
-pub const MAX_PROCESSES: usize = 64;
+pub const MAX_THREADS_PER_PROCESS: usize = if cfg!(kani) { 2 } else { 4 };
+pub const MAX_PROCESSES: usize = if cfg!(kani) { 3 } else { 64 };
 
 pub struct Process {
     id: ProcessId,
@@ -75,28 +76,38 @@ impl Process {
 
 pub struct ProcessTable {
     processes: [Option<Process>; MAX_PROCESSES],
+    generations: SlotGenerations<MAX_PROCESSES>,
 }
 
 impl ProcessTable {
     pub fn new() -> Self {
         Self {
             processes: [const { None }; MAX_PROCESSES],
+            generations: SlotGenerations::new(),
         }
     }
 
+    /// Generation capabilities to a live process must carry.
+    pub fn generation(&self, id: ProcessId) -> Option<Generation> {
+        self.get(id).ok()?;
+        self.generations.current(id.raw() as usize)
+    }
+
     pub fn create(
         &mut self,
         capabilities: CapabilityTable,
         fault_handler: Option<CapSlot>,
     ) -> Result<ProcessId, KernelError> {
-        let idx = self
+        let generations = &self.generations;
+        let (idx, slot) = self
             .processes
-            .iter()
-            .position(|s| s.is_none())
+            .iter_mut()
+            .enumerate()
+            .find(|(i, s)| s.is_none() && generations.is_usable(*i))
             .ok_or(KernelError::TooManyProcesses)?;
 
         let id = ProcessId::from_raw(idx as u16);
-        self.processes[idx] = Some(Process::new(id, capabilities, fault_handler));
+        *slot = Some(Process::new(id, capabilities, fault_handler));
         Ok(id)
     }
 
@@ -116,11 +127,22 @@ impl ProcessTable {
             .ok_or(KernelError::InvalidProcess(id))
     }
 
+    /// Removes the process; capabilities to it become invalid even if the
+    /// pid is later reused.
     pub fn destroy(&mut self, id: ProcessId) -> Result<Process, KernelError> {
         let idx = id.raw() as usize;
-        self.processes
+        let process = self
+            .processes
             .get_mut(idx)
             .and_then(|s| s.take())
-            .ok_or(KernelError::InvalidProcess(id))
+            .ok_or(KernelError::InvalidProcess(id))?;
+        self.generations.advance(idx);
+        Ok(process)
+    }
+}
+
+impl Default for ProcessTable {
+    fn default() -> Self {
+        Self::new()
     }
 }

crates/domain/src/proofs/capability.rs

@@ -1,6 +1,6 @@
+use super::{arbitrary_endpoint_cap, insert_cap};
 use crate::capability::CapabilityTable;
 use crate::resource::Resource;
-use super::{arbitrary_endpoint_cap, insert_cap};
 use types::permission::PermissionSet;
 
 #[kani::proof]

crates/domain/src/proofs/delegation.rs

@@ -1,6 +1,6 @@
+use super::{arbitrary_endpoint_cap, insert_cap};
 use crate::capability::{Capability, CapabilityTable};
 use crate::resource::Resource;
-use super::{arbitrary_endpoint_cap, insert_cap};
 use types::generation::Generation;
 use types::id::EndpointId;
 use types::permission::{Permission, PermissionSet};
@@ -16,7 +16,10 @@ fn delegation_via_cap_table_never_escalates() {
     kani::assume(source_perms.allows(Permission::Delegate));
 
     let mut source_table = CapabilityTable::new();
-    let slot = insert_cap(&mut source_table, arbitrary_endpoint_cap(source_bits, ep_id));
+    let slot = insert_cap(
+        &mut source_table,
+        arbitrary_endpoint_cap(source_bits, ep_id),
+    );
 
     let cap = source_table.get(slot).unwrap();
     let original_perms = *cap.permissions();
@@ -43,11 +46,18 @@ fn delegation_cannot_add_permissions_not_in_source() {
     let source = PermissionSet::from_bits(source_bits);
     let result = source.restrict_to(&PermissionSet::from_bits(restrict_bits));
 
-    if !source.allows(Permission::Read) { assert!(!result.allows(Permission::Read)); }
-    if !source.allows(Permission::Write) { assert!(!result.allows(Permission::Write)); }
-    if !source.allows(Permission::Execute) { assert!(!result.allows(Permission::Execute)); }
-    if !source.allows(Permission::Delegate) { assert!(!result.allows(Permission::Delegate)); }
-    if !source.allows(Permission::Revoke) { assert!(!result.allows(Permission::Revoke)); }
+    if !source.allows(Permission::Read) {
+        assert!(!result.allows(Permission::Read));
+    }
+    if !source.allows(Permission::Write) {
+        assert!(!result.allows(Permission::Write));
+    }
+    if !source.allows(Permission::Execute) {
+        assert!(!result.allows(Permission::Execute));
+    }
+    if !source.allows(Permission::Delegate) {
+        assert!(!result.allows(Permission::Delegate));
+    }
 }
 
 #[kani::proof]

crates/domain/src/proofs/thread.rs

@@ -22,7 +22,7 @@ fn dead_thread_rejects_all_transitions() {
 
     assert!(matches!(thread.state(), ThreadState::Dead));
     assert!(thread.set_running(CoreId::from_raw(0)).is_err());
-    assert!(thread.block(BlockReason::WaitingAny).is_err());
+    assert!(thread.block(BlockReason::AwaitingReply).is_err());
     assert!(thread.unblock().is_err());
     assert!(thread.preempt().is_err());
     assert!(thread.exit().is_err());
@@ -36,7 +36,7 @@ fn only_running_thread_can_block() {
     let mut thread = test_thread(Priority::new(prio_val).unwrap());
 
     assert!(matches!(thread.state(), ThreadState::Ready));
-    assert!(thread.block(BlockReason::WaitingAny).is_err());
+    assert!(thread.block(BlockReason::AwaitingReply).is_err());
 }
 
 #[kani::proof]
@@ -44,7 +44,7 @@ fn blocked_thread_cannot_run_directly() {
     let mut thread = test_thread(Priority::new(16).unwrap());
 
     thread.set_running(CoreId::from_raw(0)).unwrap();
-    thread.block(BlockReason::WaitingAny).unwrap();
+    thread.block(BlockReason::AwaitingReply).unwrap();
 
     assert!(thread.set_running(CoreId::from_raw(0)).is_err());
 }

crates/domain/src/resource.rs

@@ -1,10 +1,13 @@
-use types::id::{EndpointId, IrqId, ProcessId, RegionId};
+use types::id::{EndpointId, IrqId, NotificationId, ProcessId, RegionId};
 
-#[derive(Clone)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Resource {
     Memory(RegionId),
     Endpoint(EndpointId),
+    Notification(NotificationId),
     Process(ProcessId),
     Interrupt(IrqId),
     ProcessCreate,
+    /// Machine-wide controls such as halting; given only to init at boot.
+    SystemControl,
 }

crates/domain/src/scheduler/multi_core.rs

@@ -3,10 +3,10 @@ use types::{
     id::{CoreId, ThreadId},
 };
 
-use super::{per_core::PerCoreScheduler, Scheduler, SchedulerDecision};
+use super::{Scheduler, SchedulerDecision, per_core::PerCoreScheduler};
 
-const MAX_CORES: usize = 8;
-const MAX_SCHEDULED_THREADS: usize = 256;
+const MAX_CORES: usize = if cfg!(kani) { 1 } else { 8 };
+const MAX_SCHEDULED_THREADS: usize = crate::thread::MAX_THREADS;
 const BALANCE_THRESHOLD: usize = 2;
 
 struct ThreadPlacement {
@@ -25,17 +25,64 @@ impl MultiCoreScheduler {
         let cores = core::array::from_fn(|i| PerCoreScheduler::new(CoreId::from_raw(i as u8)));
         Self {
             cores,
-            num_cores,
+            num_cores: num_cores.min(MAX_CORES as u8),
             placements: [const { None }; MAX_SCHEDULED_THREADS],
         }
     }
 
+    fn core(&self, core: CoreId) -> Option<&PerCoreScheduler> {
+        self.active().get(core.raw() as usize)
+    }
+
+    fn core_mut(&mut self, core: CoreId) -> Option<&mut PerCoreScheduler> {
+        let n = self.num_cores as usize;
+        self.cores.get_mut(..n)?.get_mut(core.raw() as usize)
+    }
+
+    fn active(&self) -> &[PerCoreScheduler] {
+        self.cores.get(..self.num_cores as usize).unwrap_or(&[])
+    }
+
+    fn placement(&self, thread: ThreadId) -> Option<&ThreadPlacement> {
+        self.placements.get(thread.raw() as usize)?.as_ref()
+    }
+
+    pub fn num_cores(&self) -> u8 {
+        self.num_cores
+    }
+
+    /// The highest priority waiting in `core`'s run queue.
+    pub fn highest_waiting(&self, core: CoreId) -> Option<Priority> {
+        self.core(core)?.highest_waiting_priority()
+    }
+
+    /// The core whose run queue holds `thread`, if any.
+    pub fn queued_on(&self, thread: ThreadId) -> Option<CoreId> {
+        self.active()
+            .iter()
+            .find(|c| c.is_queued(thread))
+            .map(|c| c.core())
+    }
+
+    /// Whether `thread` waits in some core's run queue.
+    pub fn is_queued(&self, thread: ThreadId) -> bool {
+        self.active().iter().any(|c| c.is_queued(thread))
+    }
+
     pub fn current(&self, core: CoreId) -> Option<ThreadId> {
-        self.cores[core.raw() as usize].current()
+        self.core(core)?.current()
     }
 
     pub fn set_current(&mut self, core: CoreId, thread: ThreadId) {
-        self.cores[core.raw() as usize].set_current(thread);
+        if let Some(c) = self.core_mut(core) {
+            c.set_current(thread);
+        }
+    }
+
+    /// Runs `thread` next on `core` regardless of its place in the queue.
+    /// Fails if it is not queued there.
+    pub fn run_now(&mut self, core: CoreId, thread: ThreadId) -> bool {
+        self.core_mut(core).is_some_and(|c| c.run_now(thread))
     }
 
     fn thread_count_on(&self, core: CoreId) -> usize {
@@ -47,53 +94,63 @@ impl MultiCoreScheduler {
 
     fn least_loaded_core(&self) -> Option<CoreId> {
         (0..self.num_cores)
-            .map(|i| CoreId::from_raw(i))
+            .map(CoreId::from_raw)
             .min_by_key(|&c| self.thread_count_on(c))
     }
 
     fn most_loaded_core(&self) -> Option<CoreId> {
         (0..self.num_cores)
-            .map(|i| CoreId::from_raw(i))
+            .map(CoreId::from_raw)
             .max_by_key(|&c| self.thread_count_on(c))
     }
 }
 
 impl Scheduler for MultiCoreScheduler {
     fn add(&mut self, thread: ThreadId, priority: Priority, core: CoreId) {
-        let idx = thread.raw() as usize;
-        self.placements[idx] = Some(ThreadPlacement { core, priority });
-        self.cores[core.raw() as usize].add(thread, priority);
+        if self.core(core).is_none() {
+            return;
+        }
+        let Some(placement) = self.placements.get_mut(thread.raw() as usize) else {
+            return;
+        };
+        *placement = Some(ThreadPlacement { core, priority });
+        if let Some(c) = self.core_mut(core) {
+            c.add(thread, priority);
+        }
     }
 
     fn remove(&mut self, thread: ThreadId) {
-        let idx = thread.raw() as usize;
-        if let Some(placement) = self.placements[idx].take() {
-            let core_idx = placement.core.raw() as usize;
-            self.cores[core_idx].remove(thread, placement.priority);
-            if self.cores[core_idx].current() == Some(thread) {
-                self.cores[core_idx].clear_current();
+        let Some(placement) = self
+            .placements
+            .get_mut(thread.raw() as usize)
+            .and_then(Option::take)
+        else {
+            return;
+        };
+        if let Some(c) = self.core_mut(placement.core) {
+            c.remove(thread);
+            if c.current() == Some(thread) {
+                c.clear_current();
             }
         }
     }
 
     fn next(&mut self, core: CoreId) -> Option<ThreadId> {
-        self.cores[core.raw() as usize].pick_next()
+        self.core_mut(core)?.pick_next()
     }
 
     fn tick(&mut self, core: CoreId, current: ThreadId) -> SchedulerDecision {
-        let idx = current.raw() as usize;
-        if let Some(placement) = &self.placements[idx] {
-            let current_priority = placement.priority;
-            let core_idx = core.raw() as usize;
-            if let Some(highest) = self.cores[core_idx].highest_waiting_priority() {
-                if highest > current_priority {
-                    if let Some(next) = self.cores[core_idx].pick_next() {
-                        self.cores[core_idx].add(current, current_priority);
+        let Some(current_priority) = self.placement(current).map(|p| p.priority) else {
+            return SchedulerDecision::Continue;
+        };
+        if let Some(c) = self.core_mut(core)
+            && let Some(highest) = c.highest_waiting_priority()
+            && highest > current_priority
+            && let Some(next) = c.pick_next()
+        {
+            c.add(current, current_priority);
             return SchedulerDecision::Preempt(next);
         }
-                }
-            }
-        }
         SchedulerDecision::Continue
     }
 
@@ -103,13 +160,14 @@ impl Scheduler for MultiCoreScheduler {
             _ => return,
         };
 
-        if self.thread_count_on(busiest) > self.thread_count_on(lightest) + BALANCE_THRESHOLD {
-            let busiest_idx = busiest.raw() as usize;
-            if let Some((thread, priority)) = self.cores[busiest_idx].steal_lowest() {
-                let lightest_idx = lightest.raw() as usize;
-                self.cores[lightest_idx].add(thread, priority);
-                let tid = thread.raw() as usize;
-                self.placements[tid] = Some(ThreadPlacement {
+        if self.thread_count_on(busiest) > self.thread_count_on(lightest) + BALANCE_THRESHOLD
+            && let Some((thread, priority)) = self.core_mut(busiest).and_then(|c| c.steal_lowest())
+        {
+            if let Some(c) = self.core_mut(lightest) {
+                c.add(thread, priority);
+            }
+            if let Some(p) = self.placements.get_mut(thread.raw() as usize) {
+                *p = Some(ThreadPlacement {
                     core: lightest,
                     priority,
                 });

crates/domain/src/scheduler/per_core.rs

@@ -29,16 +29,29 @@ impl PerCoreScheduler {
         self.queue.add(thread, priority);
     }
 
-    pub fn remove(&mut self, thread: ThreadId, priority: Priority) {
-        self.queue.remove(thread, priority);
+    pub fn is_queued(&self, thread: ThreadId) -> bool {
+        self.queue.contains(thread)
+    }
+
+    pub fn remove(&mut self, thread: ThreadId) {
+        self.queue.remove(thread);
     }
 
     pub fn pick_next(&mut self) -> Option<ThreadId> {
-        let (thread, _priority) = self.queue.next()?;
+        let (thread, _priority) = self.queue.pop_highest()?;
         self.current = Some(thread);
         Some(thread)
     }
 
+    /// Takes `thread` out of the run queue and makes it current.
+    pub fn run_now(&mut self, thread: ThreadId) -> bool {
+        if !self.queue.remove(thread) {
+            return false;
+        }
+        self.current = Some(thread);
+        true
+    }
+
     pub fn clear_current(&mut self) {
         self.current = None;
     }
@@ -56,6 +69,10 @@ impl PerCoreScheduler {
     }
 
     pub fn len(&self) -> usize {
-        self.queue.bitmap().count_ones() as usize
+        self.queue.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.queue.is_empty()
     }
 }

crates/domain/src/scheduler/priority_queue.rs

@@ -2,71 +2,42 @@ use types::bounded::Priority;
 use types::id::ThreadId;
 
 const NUM_PRIORITIES: usize = 32;
-const MAX_THREADS_PER_PRIORITY: usize = 16;
+const MAX_THREADS: usize = crate::thread::MAX_THREADS;
 
-struct RunList {
-    threads: [Option<ThreadId>; MAX_THREADS_PER_PRIORITY],
-    head: usize,
-    tail: usize,
-    count: u8,
+#[derive(Clone, Copy)]
+struct Links {
+    prev: Option<ThreadId>,
+    next: Option<ThreadId>,
+    queued_at: Option<u8>,
 }
 
-impl RunList {
-    fn new() -> Self {
-        Self {
-            threads: [None; MAX_THREADS_PER_PRIORITY],
-            head: 0,
-            tail: 0,
-            count: 0,
-        }
-    }
-
-    fn push(&mut self, thread: ThreadId) -> bool {
-        match self.threads.iter_mut().find(|s| s.is_none()) {
-            Some(slot) => {
-                *slot = Some(thread);
-                self.count += 1;
-                true
-            }
-            None => false,
-        }
-    }
-
-    fn pop(&mut self) -> Option<ThreadId> {
-        if self.count == 0 {
-            return None;
-        }
-        let slot = self.threads.iter_mut().find(|s| s.is_some())?;
-        let thread = slot.take();
-        self.count -= 1;
-        thread
-    }
-
-    fn remove(&mut self, thread: ThreadId) -> bool {
-        for slot in &mut self.threads {
-            if *slot == Some(thread) {
-                *slot = None;
-                self.count -= 1;
-                return true;
-            }
-        }
-        false
-    }
-
-    fn is_empty(&self) -> bool {
-        self.count == 0
-    }
+#[derive(Clone, Copy)]
+struct ListEnds {
+    head: Option<ThreadId>,
+    tail: Option<ThreadId>,
 }
 
+/// Ready queue: one FIFO per priority level, threaded through an
+/// intrusive doubly linked list indexed by thread id. A thread is in at
+/// most one list, so capacity never runs out and every op is O(1).
 pub struct PriorityQueue {
-    queues: [RunList; NUM_PRIORITIES],
+    lists: [ListEnds; NUM_PRIORITIES],
+    links: [Links; MAX_THREADS],
     bitmap: u32,
 }
 
 impl PriorityQueue {
     pub fn new() -> Self {
         Self {
-            queues: core::array::from_fn(|_| RunList::new()),
+            lists: [ListEnds {
+                head: None,
+                tail: None,
+            }; NUM_PRIORITIES],
+            links: [Links {
+                prev: None,
+                next: None,
+                queued_at: None,
+            }; MAX_THREADS],
             bitmap: 0,
         }
     }
@@ -75,34 +46,107 @@ impl PriorityQueue {
         self.bitmap
     }
 
-    pub fn add(&mut self, thread: ThreadId, priority: Priority) {
-        let idx = priority.value() as usize;
-        let added = self.queues[idx].push(thread);
-        debug_assert!(added, "scheduler run list full for priority {}", idx);
-        if added {
-            self.bitmap |= 1 << idx;
-        }
+    pub fn len(&self) -> usize {
+        self.links.iter().filter(|l| l.queued_at.is_some()).count()
     }
 
-    pub fn remove(&mut self, thread: ThreadId, priority: Priority) {
+    pub fn contains(&self, thread: ThreadId) -> bool {
+        self.link(thread).is_some_and(|l| l.queued_at.is_some())
+    }
+
+    fn link(&self, thread: ThreadId) -> Option<&Links> {
+        self.links.get(thread.raw() as usize)
+    }
+
+    fn links_mut(&mut self, thread: ThreadId) -> Option<&mut Links> {
+        self.links.get_mut(thread.raw() as usize)
+    }
+
+    /// Appends `thread` at `priority`. A thread that is already queued is
+    /// left where it is; returns whether it was added.
+    pub fn add(&mut self, thread: ThreadId, priority: Priority) -> bool {
         let idx = priority.value() as usize;
-        self.queues[idx].remove(thread);
-        if self.queues[idx].is_empty() {
+        let queued = self.link(thread).is_none_or(|l| l.queued_at.is_some());
+        let Some(old_tail) = self.lists.get(idx).map(|l| l.tail) else {
+            return false;
+        };
+        if queued {
+            return false;
+        }
+        if let Some(l) = self.links_mut(thread) {
+            *l = Links {
+                prev: old_tail,
+                next: None,
+                queued_at: Some(idx as u8),
+            };
+        }
+        match old_tail.and_then(|t| self.links_mut(t)) {
+            Some(tail) => tail.next = Some(thread),
+            None => {
+                if let Some(list) = self.lists.get_mut(idx) {
+                    list.head = Some(thread);
+                }
+            }
+        }
+        if let Some(list) = self.lists.get_mut(idx) {
+            list.tail = Some(thread);
+        }
+        self.bitmap |= 1 << idx;
+        true
+    }
+
+    /// Unlinks `thread` from whichever level it is queued at.
+    pub fn remove(&mut self, thread: ThreadId) -> bool {
+        let Some(Links {
+            prev,
+            next,
+            queued_at: Some(level),
+        }) = self.link(thread).copied()
+        else {
+            return false;
+        };
+        let idx = level as usize;
+        match prev.and_then(|p| self.links_mut(p)) {
+            Some(p) => p.next = next,
+            None => {
+                if let Some(list) = self.lists.get_mut(idx) {
+                    list.head = next;
+                }
+            }
+        }
+        match next.and_then(|n| self.links_mut(n)) {
+            Some(n) => n.prev = prev,
+            None => {
+                if let Some(list) = self.lists.get_mut(idx) {
+                    list.tail = prev;
+                }
+            }
+        }
+        if let Some(l) = self.links_mut(thread) {
+            *l = Links {
+                prev: None,
+                next: None,
+                queued_at: None,
+            };
+        }
+        if self.lists.get(idx).is_none_or(|l| l.head.is_none()) {
             self.bitmap &= !(1 << idx);
         }
+        true
     }
 
-    pub fn next(&mut self) -> Option<(ThreadId, Priority)> {
+    fn pop_level(&mut self, idx: usize) -> Option<(ThreadId, Priority)> {
+        let thread = self.lists.get(idx)?.head?;
+        self.remove(thread);
+        Some((thread, Priority::new(idx as u8)?))
+    }
+
+    pub fn pop_highest(&mut self) -> Option<(ThreadId, Priority)> {
         if self.bitmap == 0 {
             return None;
         }
         // highest set bit = highest priority
-        let idx = 31 - self.bitmap.leading_zeros() as usize;
-        let thread = self.queues[idx].pop()?;
-        if self.queues[idx].is_empty() {
-            self.bitmap &= !(1 << idx);
-        }
-        Some((thread, Priority::new(idx as u8)?))
+        self.pop_level(31 - self.bitmap.leading_zeros() as usize)
     }
 
     pub fn highest_priority(&self) -> Option<Priority> {
@@ -117,15 +161,16 @@ impl PriorityQueue {
         if self.bitmap == 0 {
             return None;
         }
-        let idx = self.bitmap.trailing_zeros() as usize;
-        let thread = self.queues[idx].pop()?;
-        if self.queues[idx].is_empty() {
-            self.bitmap &= !(1 << idx);
-        }
-        Some((thread, Priority::new(idx as u8)?))
+        self.pop_level(self.bitmap.trailing_zeros() as usize)
     }
 
     pub fn is_empty(&self) -> bool {
         self.bitmap == 0
     }
 }
+
+impl Default for PriorityQueue {
+    fn default() -> Self {
+        Self::new()
+    }
+}

crates/domain/src/scheduler/tests.rs

@@ -22,7 +22,7 @@ fn prio(value: u8) -> Priority {
 #[test]
 fn empty_queue_returns_none() {
     let mut q = PriorityQueue::new();
-    assert!(q.next().is_none());
+    assert!(q.pop_highest().is_none());
     assert!(q.is_empty());
 }
 
@@ -31,7 +31,7 @@ fn single_thread() {
     let mut q = PriorityQueue::new();
     q.add(thread(1), prio(10));
 
-    let (t, p) = q.next().unwrap();
+    let (t, p) = q.pop_highest().unwrap();
     assert_eq!(t, thread(1));
     assert_eq!(p, prio(10));
 }
@@ -43,7 +43,7 @@ fn highest_priority_runs_first() {
     q.add(thread(2), prio(20));
     q.add(thread(3), prio(10));
 
-    let (t, _) = q.next().unwrap();
+    let (t, _) = q.pop_highest().unwrap();
     assert_eq!(t, thread(2));
 }
 
@@ -54,10 +54,10 @@ fn same_priority_is_fifo() {
     q.add(thread(2), prio(10));
     q.add(thread(3), prio(10));
 
-    assert_eq!(q.next().unwrap().0, thread(1));
-    assert_eq!(q.next().unwrap().0, thread(2));
-    assert_eq!(q.next().unwrap().0, thread(3));
-    assert!(q.next().is_none());
+    assert_eq!(q.pop_highest().unwrap().0, thread(1));
+    assert_eq!(q.pop_highest().unwrap().0, thread(2));
+    assert_eq!(q.pop_highest().unwrap().0, thread(3));
+    assert!(q.pop_highest().is_none());
 }
 
 #[test]
@@ -66,18 +66,18 @@ fn remove_thread() {
     q.add(thread(1), prio(10));
     q.add(thread(2), prio(10));
 
-    q.remove(thread(1), prio(10));
+    q.remove(thread(1));
 
-    let (t, _) = q.next().unwrap();
+    let (t, _) = q.pop_highest().unwrap();
     assert_eq!(t, thread(2));
-    assert!(q.next().is_none());
+    assert!(q.pop_highest().is_none());
 }
 
 #[test]
 fn remove_clears_bitmap_when_empty() {
     let mut q = PriorityQueue::new();
     q.add(thread(1), prio(10));
-    q.remove(thread(1), prio(10));
+    q.remove(thread(1));
 
     assert!(q.is_empty());
 }
@@ -89,9 +89,9 @@ fn drain_all_priorities() {
     q.add(thread(2), prio(15));
     q.add(thread(3), prio(31));
 
-    assert_eq!(q.next().unwrap().0, thread(3)); // highest first
-    assert_eq!(q.next().unwrap().0, thread(2));
-    assert_eq!(q.next().unwrap().0, thread(1)); // lowest last
+    assert_eq!(q.pop_highest().unwrap().0, thread(3)); // highest first
+    assert_eq!(q.pop_highest().unwrap().0, thread(2));
+    assert_eq!(q.pop_highest().unwrap().0, thread(1)); // lowest last
     assert!(q.is_empty());
 }
 
@@ -137,7 +137,7 @@ fn highest_priority_peeks_without_popping() {
     q.add(thread(1), prio(5));
     q.add(thread(2), prio(20));
     assert_eq!(q.highest_priority(), Some(prio(20)));
-    assert_eq!(q.next().unwrap().0, thread(2));
+    assert_eq!(q.pop_highest().unwrap().0, thread(2));
 }
 
 #[test]
@@ -154,7 +154,7 @@ fn steal_lowest_takes_lowest_priority_thread() {
     let (t, p) = q.steal_lowest().unwrap();
     assert_eq!(t, thread(1));
     assert_eq!(p, prio(5));
-    assert_eq!(q.next().unwrap().0, thread(2));
+    assert_eq!(q.pop_highest().unwrap().0, thread(2));
 }
 
 #[test]
@@ -240,3 +240,89 @@ fn multi_threads_on_different_cores() {
     assert_eq!(s.next(core(0)), Some(thread(1)));
     assert_eq!(s.next(core(1)), Some(thread(2)));
 }
+
+#[test]
+fn requeued_thread_goes_behind_same_priority_peers() {
+    let mut q = PriorityQueue::new();
+    let p = Priority::new(5).unwrap();
+    q.add(thread(1), p);
+    q.add(thread(2), p);
+
+    assert_eq!(q.pop_highest().unwrap().0, thread(1));
+    q.add(thread(1), p); // preempted, back in the run list
+
+    assert_eq!(q.pop_highest().unwrap().0, thread(2));
+    assert_eq!(q.pop_highest().unwrap().0, thread(1));
+}
+
+#[test]
+fn round_robin_survives_wraparound() {
+    let mut q = PriorityQueue::new();
+    let p = Priority::new(5).unwrap();
+    q.add(thread(1), p);
+    q.add(thread(2), p);
+    q.add(thread(3), p);
+    for _ in 0..40 {
+        let (a, _) = q.pop_highest().unwrap();
+        q.add(a, p);
+    }
+    // 40 rotations of 3 threads: 40 % 3 == 1, so thread 2 is at the head
+    assert_eq!(q.pop_highest().unwrap().0, thread(2));
+    assert_eq!(q.pop_highest().unwrap().0, thread(3));
+    assert_eq!(q.pop_highest().unwrap().0, thread(1));
+}
+
+#[test]
+fn removed_thread_is_skipped_and_order_kept() {
+    let mut q = PriorityQueue::new();
+    let p = Priority::new(5).unwrap();
+    q.add(thread(1), p);
+    q.add(thread(2), p);
+    q.add(thread(3), p);
+    q.remove(thread(2));
+    assert_eq!(q.pop_highest().unwrap().0, thread(1));
+    assert_eq!(q.pop_highest().unwrap().0, thread(3));
+    assert!(q.pop_highest().is_none());
+}
+
+#[test]
+fn run_now_picks_the_named_thread_not_the_queue_head() {
+    let mut s = MultiCoreScheduler::new(1);
+    s.add(thread(1), prio(10), core(0));
+    s.add(thread(2), prio(10), core(0));
+    s.add(thread(3), prio(10), core(0));
+
+    assert!(s.run_now(core(0), thread(2)));
+    assert_eq!(s.current(core(0)), Some(thread(2)));
+    // The others keep their order; thread 2 is no longer queued.
+    assert_eq!(s.next(core(0)), Some(thread(1)));
+    assert_eq!(s.next(core(0)), Some(thread(3)));
+    assert_eq!(s.next(core(0)), None);
+}
+
+#[test]
+fn run_now_rejects_a_thread_that_is_not_queued() {
+    let mut s = MultiCoreScheduler::new(1);
+    s.add(thread(1), prio(10), core(0));
+    assert!(!s.run_now(core(0), thread(9)));
+    assert_eq!(s.current(core(0)), None);
+}
+
+#[test]
+fn an_unknown_core_is_ignored_not_a_panic() {
+    let mut s = MultiCoreScheduler::new(1);
+    s.add(thread(1), prio(10), core(200));
+    assert_eq!(s.next(core(200)), None);
+    assert_eq!(s.current(core(200)), None);
+    s.set_current(core(200), thread(1));
+    assert!(!s.run_now(core(200), thread(1)));
+}
+
+#[test]
+fn an_out_of_range_thread_id_is_ignored_not_a_panic() {
+    let mut s = MultiCoreScheduler::new(1);
+    s.add(thread(60000), prio(10), core(0));
+    s.remove(thread(60000));
+    assert!(!s.is_queued(thread(60000)));
+    let _ = s.tick(core(0), thread(60000));
+}

crates/domain/src/syscall.rs

@@ -1,43 +1,13 @@
 use types::{
     address::{DataRef, EntryPoint, StackPointer, VirtualAddress},
+    badge::Badge,
     bounded::{CapSlot, PageCount},
+    mapping::PagePerms,
     permission::PermissionSet,
 };
 
 use crate::message::Message;
 
-pub struct WaitSet {
-    endpoints: [Option<CapSlot>; 4],
-    interrupts: [Option<CapSlot>; 4],
-}
-
-impl WaitSet {
-    pub fn new(
-        endpoints: [Option<CapSlot>; 4],
-        interrupts: [Option<CapSlot>; 4],
-    ) -> Self {
-        Self { endpoints, interrupts }
-    }
-
-    pub fn endpoints(&self) -> &[Option<CapSlot>; 4] {
-        &self.endpoints
-    }
-
-    pub fn interrupts(&self) -> &[Option<CapSlot>; 4] {
-        &self.interrupts
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.endpoints.iter().all(|s| s.is_none())
-            && self.interrupts.iter().all(|s| s.is_none())
-    }
-}
-
-pub enum WakeReason {
-    MessageReady(CapSlot),
-    InterruptFired(CapSlot),
-}
-
 pub enum Syscall {
     Send {
         endpoint: CapSlot,
@@ -51,15 +21,47 @@ pub enum Syscall {
         to_endpoint: CapSlot,
         permissions: PermissionSet,
     },
-    WaitForInterrupt {
+    /// Send, then block for the reply (docs/ipc.md).
+    Call {
+        endpoint: CapSlot,
+        message: Message,
+    },
+    /// Answer the thread in the caller's reply slot.
+    Reply {
+        message: Message,
+    },
+    /// Reply (if a reply is pending), then receive.
+    ReplyRecv {
+        endpoint: CapSlot,
+        message: Message,
+    },
+    /// Copy an unbadged endpoint/notification cap with a badge and
+    /// narrower permissions into the caller's own table.
+    Mint {
+        slot: CapSlot,
+        badge: Badge,
+        permissions: PermissionSet,
+    },
+    CreateNotification,
+    Signal {
+        notification: CapSlot,
+    },
+    Wait {
+        notification: CapSlot,
+    },
+    Poll {
+        notification: CapSlot,
+    },
+    BindNotification {
+        notification: CapSlot,
+    },
+    SetIrqNotification {
         irq: CapSlot,
+        notification: CapSlot,
     },
     AcknowledgeInterrupt {
         irq: CapSlot,
     },
-    WaitAny {
-        sources: WaitSet,
-    },
     CreateProcess {
         create_cap: CapSlot,
         image: DataRef,
@@ -67,9 +69,30 @@ pub enum Syscall {
     Kill {
         process: CapSlot,
     },
+    /// Deletes every capability derived from `slot`, keeping `slot`.
     Revoke {
         slot: CapSlot,
     },
+    /// Allocates a shared-memory region charged to the caller and returns
+    /// a capability to it.
+    CreateRegion {
+        pages: PageCount,
+    },
+    /// Maps the whole region named by `region` at `va` in the caller.
+    MapRegion {
+        region: CapSlot,
+        va: VirtualAddress,
+        perms: PagePerms,
+    },
+    /// The physical base of the region named by `region`, so a driver can
+    /// point a device's DMA at memory it has mapped.
+    RegionAddress {
+        region: CapSlot,
+    },
+    /// Removes a capability from the caller's own table.
+    DropCap {
+        slot: CapSlot,
+    },
     SpawnThread {
         entry: EntryPoint,
         stack: StackPointer,
@@ -86,9 +109,14 @@ pub enum Syscall {
     GetProcessId,
     Yield,
     Exit,
-    Halt,
+    /// Stops the machine; needs a SystemControl capability.
+    Halt {
+        control: CapSlot,
+    },
     CreateEndpoint,
-    DebugPutchar { byte: u8 },
+    DebugPutchar {
+        byte: u8,
+    },
     MapPage {
         process: CapSlot,
         src_va: VirtualAddress,

crates/domain/src/thread/mod.rs

@@ -1,10 +1,11 @@
 use types::{
-    bounded::{CapSlot, Priority},
-    id::{CoreId, ProcessId, ThreadId},
+    bounded::Priority,
+    generation::Generation,
+    id::{CoreId, EndpointId, NotificationId, ProcessId, ThreadId},
     time::TimeSlice,
 };
 
-use crate::error::KernelError;
+use crate::{error::KernelError, generations::SlotGenerations};
 
 #[cfg(test)]
 #[path = "tests.rs"]
@@ -20,6 +21,7 @@ pub struct Thread {
     core_affinity: Option<CoreId>,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum ThreadState {
     Ready,
     Running(CoreId),
@@ -77,11 +79,18 @@ impl SavedContext {
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum BlockReason {
-    Sending(CapSlot),
-    Receiving(CapSlot),
-    WaitingForInterrupt(CapSlot),
-    WaitingAny,
+    /// Queued as a sender on the endpoint.
+    Sending(EndpointId),
+    /// Queued as a `Call`er on the endpoint; will then await the reply.
+    Calling(EndpointId),
+    /// Queued as a receiver on the endpoint.
+    Receiving(EndpointId),
+    /// Delivered a `Call`; waiting for the server's reply.
+    AwaitingReply,
+    /// Blocked in `Wait` on the notification.
+    WaitingNotification(NotificationId),
 }
 
 impl Thread {
@@ -178,6 +187,17 @@ impl Thread {
         }
     }
 
+    /// Keeps a blocked thread blocked, waiting for something else.
+    pub fn rewait(&mut self, reason: BlockReason) -> Result<(), KernelError> {
+        match self.state {
+            ThreadState::Blocked(_) => {
+                self.state = ThreadState::Blocked(reason);
+                Ok(())
+            }
+            _ => Err(KernelError::InvalidStateTransition(self.id)),
+        }
+    }
+
     pub fn unblock(&mut self) -> Result<(), KernelError> {
         match self.state {
             ThreadState::Blocked(_) => {
@@ -209,19 +229,35 @@ impl Thread {
     }
 }
 
-pub const MAX_THREADS: usize = 256;
+pub const MAX_THREADS: usize = if cfg!(kani) { 3 } else { 256 };
 
 pub struct ThreadTable {
     threads: [Option<Thread>; MAX_THREADS],
+    generations: SlotGenerations<MAX_THREADS>,
 }
 
 impl ThreadTable {
     pub fn new() -> Self {
         Self {
             threads: [const { None }; MAX_THREADS],
+            generations: SlotGenerations::new(),
         }
     }
 
+    /// Current generation of a live thread, so references to it (reply
+    /// slots) can detect that the id was reused.
+    pub fn generation(&self, id: ThreadId) -> Option<Generation> {
+        self.get(id).ok()?;
+        self.generations.current(id.raw() as usize)
+    }
+
+    fn free_slot(&self) -> Option<usize> {
+        self.threads
+            .iter()
+            .enumerate()
+            .position(|(i, t)| t.is_none() && self.generations.is_usable(i))
+    }
+
     pub fn spawn(
         &mut self,
         process: ProcessId,
@@ -229,14 +265,19 @@ impl ThreadTable {
         time_slice: TimeSlice,
         core_affinity: Option<CoreId>,
     ) -> Result<ThreadId, KernelError> {
-        let idx = self
-            .threads
-            .iter()
-            .position(|s| s.is_none())
-            .ok_or(KernelError::TooManyThreads)?;
+        let idx = self.free_slot().ok_or(KernelError::TooManyThreads)?;
 
         let id = ThreadId::from_raw(idx as u16);
-        self.threads[idx] = Some(Thread::new(id, process, priority, time_slice, core_affinity));
+        *self
+            .threads
+            .get_mut(idx)
+            .ok_or(KernelError::TooManyThreads)? = Some(Thread::new(
+            id,
+            process,
+            priority,
+            time_slice,
+            core_affinity,
+        ));
         Ok(id)
     }
 
@@ -248,17 +289,31 @@ impl ThreadTable {
         core_affinity: Option<CoreId>,
         context: SavedContext,
     ) -> Result<ThreadId, KernelError> {
-        let idx = self
-            .threads
-            .iter()
-            .position(|s| s.is_none())
-            .ok_or(KernelError::TooManyThreads)?;
+        let idx = self.free_slot().ok_or(KernelError::TooManyThreads)?;
 
         let id = ThreadId::from_raw(idx as u16);
-        self.threads[idx] = Some(Thread::with_context(id, process, priority, time_slice, core_affinity, context));
+        *self
+            .threads
+            .get_mut(idx)
+            .ok_or(KernelError::TooManyThreads)? = Some(Thread::with_context(
+            id,
+            process,
+            priority,
+            time_slice,
+            core_affinity,
+            context,
+        ));
         Ok(id)
     }
 
+    /// Every live thread with its id.
+    pub fn iter(&self) -> impl Iterator<Item = (ThreadId, &Thread)> {
+        self.threads
+            .iter()
+            .enumerate()
+            .filter_map(|(i, t)| Some((ThreadId::from_raw(i as u16), t.as_ref()?)))
+    }
+
     pub fn get(&self, id: ThreadId) -> Result<&Thread, KernelError> {
         let idx = id.raw() as usize;
         self.threads
@@ -277,10 +332,13 @@ impl ThreadTable {
 
     pub fn destroy(&mut self, id: ThreadId) -> Result<Thread, KernelError> {
         let idx = id.raw() as usize;
-        self.threads
+        let thread = self
+            .threads
             .get_mut(idx)
             .and_then(|s| s.take())
-            .ok_or(KernelError::InvalidThread(id))
+            .ok_or(KernelError::InvalidThread(id))?;
+        self.generations.advance(idx);
+        Ok(thread)
     }
 
     pub fn threads_for_process(&self, process: ProcessId) -> impl Iterator<Item = &Thread> {
@@ -290,3 +348,9 @@ impl ThreadTable {
             .filter(move |t| t.process() == process)
     }
 }
+
+impl Default for ThreadTable {
+    fn default() -> Self {
+        Self::new()
+    }
+}

crates/domain/src/thread/tests.rs

@@ -1,6 +1,6 @@
 use super::*;
 use types::bounded::Priority;
-use types::id::{CoreId, ProcessId, ThreadId};
+use types::id::{CoreId, EndpointId, ProcessId, ThreadId};
 use types::time::TimeSlice;
 
 fn thread(id: u16) -> ThreadId {
@@ -65,15 +65,18 @@ fn ready_to_running() {
 fn running_to_blocked() {
     let mut t = test_thread(0, 0);
     t.set_running(core(0)).unwrap();
-    t.block(BlockReason::WaitingAny).unwrap();
-    assert!(matches!(t.state(), ThreadState::Blocked(BlockReason::WaitingAny)));
+    t.block(BlockReason::AwaitingReply).unwrap();
+    assert!(matches!(
+        t.state(),
+        ThreadState::Blocked(BlockReason::AwaitingReply)
+    ));
 }
 
 #[test]
 fn blocked_to_ready() {
     let mut t = test_thread(0, 0);
     t.set_running(core(0)).unwrap();
-    t.block(BlockReason::WaitingAny).unwrap();
+    t.block(BlockReason::AwaitingReply).unwrap();
     t.unblock().unwrap();
     assert!(matches!(t.state(), ThreadState::Ready));
 }
@@ -102,7 +105,7 @@ fn dead_cannot_transition() {
     t.set_running(core(0)).unwrap();
     t.exit().unwrap();
     assert!(t.set_running(core(0)).is_err());
-    assert!(t.block(BlockReason::WaitingAny).is_err());
+    assert!(t.block(BlockReason::AwaitingReply).is_err());
     assert!(t.unblock().is_err());
     assert!(t.preempt().is_err());
     assert!(t.exit().is_err());
@@ -111,14 +114,14 @@ fn dead_cannot_transition() {
 #[test]
 fn ready_cannot_block() {
     let mut t = test_thread(0, 0);
-    assert!(t.block(BlockReason::WaitingAny).is_err());
+    assert!(t.block(BlockReason::AwaitingReply).is_err());
 }
 
 #[test]
 fn blocked_cannot_run_directly() {
     let mut t = test_thread(0, 0);
     t.set_running(core(0)).unwrap();
-    t.block(BlockReason::WaitingAny).unwrap();
+    t.block(BlockReason::AwaitingReply).unwrap();
     assert!(t.set_running(core(0)).is_err());
 }
 
@@ -138,7 +141,7 @@ fn ready_cannot_exit() {
 fn blocked_cannot_preempt() {
     let mut t = test_thread(0, 0);
     t.set_running(core(0)).unwrap();
-    t.block(BlockReason::WaitingAny).unwrap();
+    t.block(BlockReason::AwaitingReply).unwrap();
     assert!(t.preempt().is_err());
 }
 
@@ -162,7 +165,9 @@ fn time_slice_mut_ticks() {
 #[test]
 fn table_spawn_and_lookup() {
     let mut table = ThreadTable::new();
-    let id = table.spawn(process(0), prio(10), time_slice(), None).unwrap();
+    let id = table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
     let t = table.get(id).unwrap();
     assert_eq!(t.id(), id);
     assert_eq!(t.process(), process(0));
@@ -171,15 +176,21 @@ fn table_spawn_and_lookup() {
 #[test]
 fn table_spawn_returns_unique_ids() {
     let mut table = ThreadTable::new();
-    let a = table.spawn(process(0), prio(10), time_slice(), None).unwrap();
-    let b = table.spawn(process(0), prio(10), time_slice(), None).unwrap();
+    let a = table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
+    let b = table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
     assert_ne!(a, b);
 }
 
 #[test]
 fn table_destroy_then_get_fails() {
     let mut table = ThreadTable::new();
-    let id = table.spawn(process(0), prio(10), time_slice(), None).unwrap();
+    let id = table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
     table.destroy(id).unwrap();
     assert!(table.get(id).is_err());
 }
@@ -187,9 +198,15 @@ fn table_destroy_then_get_fails() {
 #[test]
 fn table_threads_for_process_filters() {
     let mut table = ThreadTable::new();
-    table.spawn(process(0), prio(10), time_slice(), None).unwrap();
-    table.spawn(process(1), prio(10), time_slice(), None).unwrap();
-    table.spawn(process(0), prio(5), time_slice(), None).unwrap();
+    table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
+    table
+        .spawn(process(1), prio(10), time_slice(), None)
+        .unwrap();
+    table
+        .spawn(process(0), prio(5), time_slice(), None)
+        .unwrap();
 
     let count = table.threads_for_process(process(0)).count();
     assert_eq!(count, 2);
@@ -198,16 +215,54 @@ fn table_threads_for_process_filters() {
 #[test]
 fn table_get_mut_allows_state_transition() {
     let mut table = ThreadTable::new();
-    let id = table.spawn(process(0), prio(10), time_slice(), None).unwrap();
+    let id = table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
     table.get_mut(id).unwrap().set_running(core(0)).unwrap();
-    assert!(matches!(table.get(id).unwrap().state(), ThreadState::Running(_)));
+    assert!(matches!(
+        table.get(id).unwrap().state(),
+        ThreadState::Running(_)
+    ));
 }
 
 #[test]
 fn table_destroy_reuses_slot() {
     let mut table = ThreadTable::new();
-    let id = table.spawn(process(0), prio(10), time_slice(), None).unwrap();
+    let id = table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
     table.destroy(id).unwrap();
-    let new_id = table.spawn(process(0), prio(10), time_slice(), None).unwrap();
+    let new_id = table
+        .spawn(process(0), prio(10), time_slice(), None)
+        .unwrap();
     assert_eq!(id, new_id);
 }
+
+#[test]
+fn a_blocked_thread_can_change_what_it_waits_for() {
+    let mut t = Thread::new(
+        ThreadId::from_raw(1),
+        ProcessId::from_raw(0),
+        Priority::DEFAULT,
+        TimeSlice::DEFAULT,
+        None,
+    );
+    t.set_running(CoreId::from_raw(0)).unwrap();
+    t.block(BlockReason::Calling(EndpointId::from_raw(0)))
+        .unwrap();
+    t.rewait(BlockReason::AwaitingReply).unwrap();
+    assert_eq!(*t.state(), ThreadState::Blocked(BlockReason::AwaitingReply));
+}
+
+#[test]
+fn only_blocked_threads_can_rewait() {
+    let mut t = Thread::new(
+        ThreadId::from_raw(1),
+        ProcessId::from_raw(0),
+        Priority::DEFAULT,
+        TimeSlice::DEFAULT,
+        None,
+    );
+    assert!(t.rewait(BlockReason::AwaitingReply).is_err());
+    assert_eq!(*t.state(), ThreadState::Ready);
+}

crates/elf/src/lib.rs

@@ -134,7 +134,7 @@ impl ElfInfo {
     pub fn total_pages(&self) -> usize {
         let mut total = 0;
         for seg in self.segments() {
-            total += (seg.mem_size + 4095) / 4096;
+            total += seg.mem_size.div_ceil(4096);
         }
         total
     }

crates/hw-virtio/src/mmio.rs

@@ -87,9 +87,11 @@ pub const MMIO_FIRST: usize = 0x10001000;
 pub const MMIO_STRIDE: usize = 0x1000;
 pub const MMIO_SLOTS: usize = 8;
 
-pub fn scan_for_device(device_id: u32) -> Option<DirectMmio> {
+/// Probes the MMIO slots starting at `first`, the address the caller sees
+/// slot 0 at (`MMIO_FIRST` itself, or wherever it is mapped).
+pub fn scan_for_device(first: usize, device_id: u32) -> Option<DirectMmio> {
     for slot in 0..MMIO_SLOTS {
-        if let Some(mmio) = probe_slot(MMIO_FIRST + slot * MMIO_STRIDE, device_id) {
+        if let Some(mmio) = probe_slot(first + slot * MMIO_STRIDE, device_id) {
             return Some(mmio);
         }
     }

crates/kernel/Cargo.toml

@@ -7,3 +7,6 @@ edition = "2024"
 types = { workspace = true }
 domain = { workspace = true }
 platform = { workspace = true }
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ["cfg(kani)"] }

crates/kernel/src/abi.rs

@@ -0,0 +1,162 @@
+//! The syscall register ABI (docs/ipc.md), as pure functions so it can be
+//! tested and proved: registers in, `Syscall` out; result out, registers
+//! in. Architecture adapters only move registers in and out of a frame.
+
+use domain::{message::Message, syscall::Syscall};
+use types::{
+    address::{DataRef, EntryPoint, StackPointer, VirtualAddress},
+    badge::Badge,
+    bounded::{CapSlot, PageCount},
+    permission::PermissionSet,
+    syscall_abi::*,
+};
+
+use crate::syscall::{SyscallResult, error_code};
+
+fn slot(r: usize) -> Option<CapSlot> {
+    reg_slot(r)?
+}
+
+fn pages(r: usize) -> Option<PageCount> {
+    PageCount::new(u16::try_from(r).ok()?)
+}
+
+fn permissions(r: usize) -> Option<PermissionSet> {
+    Some(PermissionSet::from_bits(u8::try_from(r).ok()?))
+}
+
+/// The message in `a1..a5`.
+fn message(a: &[usize; 6]) -> Option<Message> {
+    let msg = Message::from_words([a[1], a[2], a[3], a[4]]);
+    Some(match reg_slot(a[5])? {
+        None => msg,
+        Some(cap) => msg.with_cap(cap),
+    })
+}
+
+/// Decodes syscall `nr` with arguments `a0..a5`. `None` for an unknown
+/// number or an argument with no meaning (e.g. a slot out of range); the
+/// caller then gets `UnknownSyscall` and nothing else happens.
+pub fn decode(nr: usize, a: &[usize; 6]) -> Option<Syscall> {
+    Some(match nr {
+        SYS_EXIT => Syscall::Exit,
+        SYS_HALT => Syscall::Halt {
+            control: slot(a[0])?,
+        },
+        SYS_EXIT_THREAD => Syscall::ExitThread,
+        SYS_YIELD => Syscall::Yield,
+        SYS_GET_TIME => Syscall::GetTime,
+        SYS_GET_PROCESS_ID => Syscall::GetProcessId,
+        SYS_SEND => Syscall::Send {
+            endpoint: slot(a[0])?,
+            message: message(a)?,
+        },
+        SYS_CALL => Syscall::Call {
+            endpoint: slot(a[0])?,
+            message: message(a)?,
+        },
+        SYS_RECEIVE => Syscall::Receive {
+            endpoint: slot(a[0])?,
+        },
+        SYS_REPLY => Syscall::Reply {
+            message: message(a)?,
+        },
+        SYS_REPLY_RECV => Syscall::ReplyRecv {
+            endpoint: slot(a[0])?,
+            message: message(a)?,
+        },
+        SYS_DELEGATE => Syscall::Delegate {
+            slot: slot(a[0])?,
+            to_endpoint: slot(a[1])?,
+            permissions: permissions(a[2])?,
+        },
+        SYS_MINT => Syscall::Mint {
+            slot: slot(a[0])?,
+            badge: Badge::new(a[1]),
+            permissions: permissions(a[2])?,
+        },
+        SYS_CREATE_NOTIFICATION => Syscall::CreateNotification,
+        SYS_SIGNAL => Syscall::Signal {
+            notification: slot(a[0])?,
+        },
+        SYS_WAIT => Syscall::Wait {
+            notification: slot(a[0])?,
+        },
+        SYS_POLL => Syscall::Poll {
+            notification: slot(a[0])?,
+        },
+        SYS_BIND_NOTIFICATION => Syscall::BindNotification {
+            notification: slot(a[0])?,
+        },
+        SYS_SET_IRQ_NOTIFICATION => Syscall::SetIrqNotification {
+            irq: slot(a[0])?,
+            notification: slot(a[1])?,
+        },
+        SYS_ACKNOWLEDGE_INTERRUPT => Syscall::AcknowledgeInterrupt { irq: slot(a[0])? },
+        SYS_CREATE_PROCESS => Syscall::CreateProcess {
+            create_cap: slot(a[0])?,
+            image: DataRef::empty(),
+        },
+        SYS_KILL => Syscall::Kill {
+            process: slot(a[0])?,
+        },
+        SYS_REVOKE => Syscall::Revoke { slot: slot(a[0])? },
+        SYS_DROP_CAP => Syscall::DropCap { slot: slot(a[0])? },
+        SYS_SPAWN_THREAD => Syscall::SpawnThread {
+            entry: EntryPoint::from_raw(a[0]),
+            stack: StackPointer::from_raw(a[1]),
+        },
+        SYS_REQUEST_PAGES => Syscall::RequestPages {
+            count: pages(a[0])?,
+        },
+        SYS_RELEASE_PAGES => Syscall::ReleasePages {
+            addr: VirtualAddress::from_raw(a[0]),
+            count: pages(a[1])?,
+        },
+        SYS_SPAWN_THREAD_IN => Syscall::SpawnThreadIn {
+            process: slot(a[0])?,
+            entry: EntryPoint::from_raw(a[1]),
+            stack: StackPointer::from_raw(a[2]),
+        },
+        SYS_CREATE_ENDPOINT => Syscall::CreateEndpoint,
+        SYS_CREATE_REGION => Syscall::CreateRegion {
+            pages: pages(a[0])?,
+        },
+        SYS_MAP_REGION => Syscall::MapRegion {
+            region: slot(a[0])?,
+            va: VirtualAddress::from_raw(a[1]),
+            perms: reg_perms(a[2])?,
+        },
+        SYS_REGION_ADDRESS => Syscall::RegionAddress {
+            region: slot(a[0])?,
+        },
+        SYS_DEBUG_PUTCHAR => Syscall::DebugPutchar { byte: a[0] as u8 },
+        SYS_MAP_PAGE => Syscall::MapPage {
+            process: slot(a[0])?,
+            src_va: VirtualAddress::from_raw(a[1]),
+            dst_va: VirtualAddress::from_raw(a[2]),
+            executable: a[3] != 0,
+        },
+        _ => return None,
+    })
+}
+
+/// Result registers `a0..a7` for a completed syscall.
+pub fn encode(result: &SyscallResult) -> [usize; 8] {
+    let mut r = [0usize; 8];
+    match result {
+        SyscallResult::Ok => {}
+        SyscallResult::Value(v) => r[1] = *v,
+        SyscallResult::Slot(s) => r[1] = s.value() as usize,
+        SyscallResult::Received(d) => r = delivery_regs(d),
+        SyscallResult::Error(e) => r[0] = error_code(e) as usize,
+    }
+    r
+}
+
+/// Registers for a syscall number that does not decode.
+pub fn unknown_syscall() -> [usize; 8] {
+    let mut r = [0usize; 8];
+    r[0] = ErrorCode::UnknownSyscall as usize;
+    r
+}

crates/kernel/src/board.rs

@@ -0,0 +1,79 @@
+//! The authority init starts with. The board describes its devices; the
+//! kernel turns each into capabilities (an MMIO region and an IRQ line)
+//! and adds one SystemControl capability. Init then decides who gets what;
+//! nothing else is privileged by its process id.
+
+use domain::{error::KernelError, resource::Resource};
+use platform::Platform;
+use types::{
+    address::PhysicalAddress,
+    bounded::PageCount,
+    id::{IrqId, ProcessId, RegionId},
+    permission::{Permission, PermissionSet},
+};
+
+use crate::Kernel;
+
+/// A device the board exposes to userspace: its MMIO window and, if it
+/// raises interrupts, its IRQ line.
+#[derive(Debug, Clone, Copy)]
+pub struct BoardDevice {
+    pub base: PhysicalAddress,
+    pub pages: PageCount,
+    pub irq: Option<IrqId>,
+}
+
+impl<P: Platform> Kernel<P> {
+    /// Creates one device region per board device, owned by `init`. Fails
+    /// on the first device that is misaligned, overlaps the frame pool or
+    /// another device, or names an IRQ the kernel cannot route.
+    pub fn register_board(
+        &mut self,
+        init: ProcessId,
+        devices: &[BoardDevice],
+    ) -> Result<(), KernelError> {
+        for device in devices {
+            if let Some(irq) = device.irq
+                && !self.irqs.is_valid(irq)
+            {
+                return Err(KernelError::InvalidIrq(irq));
+            }
+            self.create_device_region(init, device.base, device.pages)?;
+        }
+        Ok(())
+    }
+
+    /// Gives `init` a capability to every registered device's region and
+    /// IRQ line, then one SystemControl capability. All carry Delegate so
+    /// init can hand them on. Done separately from `register_board` so
+    /// boot code can wire drivers to the regions first.
+    pub fn grant_boot_authority(
+        &mut self,
+        init: ProcessId,
+        devices: &[BoardDevice],
+    ) -> Result<(), KernelError> {
+        let delegate = PermissionSet::empty().with(Permission::Delegate);
+        let control = delegate.with(Permission::Execute);
+        let mmio = delegate.with(Permission::Read).with(Permission::Write);
+        for device in devices {
+            let region = self
+                .device_region_at(device.base)
+                .filter(|id| self.regions.get(*id).is_some_and(|r| r.owner() == init))
+                .ok_or(KernelError::NoSuchObject)?;
+            self.grant_cap(init, Resource::Memory(region), mmio)?;
+            if let Some(irq) = device.irq {
+                self.grant_cap(init, Resource::Interrupt(irq), control)?;
+            }
+        }
+        self.grant_cap(init, Resource::SystemControl, control)?;
+        Ok(())
+    }
+
+    /// The device region that starts at `base`.
+    pub fn device_region_at(&self, base: PhysicalAddress) -> Option<RegionId> {
+        self.regions
+            .iter()
+            .find(|(_, r)| r.backing() == domain::memory::RegionBacking::Device && r.base() == base)
+            .map(|(id, _)| id)
+    }
+}

crates/kernel/src/captree.rs

@@ -0,0 +1,172 @@
+//! The capability derivation tree. Every derived capability (Mint,
+//! Delegate, IPC transfer) records its parent; `Revoke` deletes a subtree
+//! and deleting a capability re-parents its children, so the tree can only
+//! shrink by explicit deletion, never by a middleman stepping out.
+
+use domain::{
+    capability::{CapRef, Capability, MAX_CAPS_PER_PROCESS, derivation::descendants},
+    error::KernelError,
+    process::MAX_PROCESSES,
+};
+use platform::Platform;
+use types::{
+    bounded::CapSlot,
+    id::{ProcessId, RegionId},
+};
+
+use crate::Kernel;
+
+/// Every capability slot in the system, flattened.
+const ALL_CAPS: usize = MAX_PROCESSES * MAX_CAPS_PER_PROCESS;
+
+fn flat(pid: ProcessId, slot: CapSlot) -> usize {
+    pid.raw() as usize * MAX_CAPS_PER_PROCESS + slot.value() as usize
+}
+
+fn unflat(i: usize) -> Option<(ProcessId, CapSlot)> {
+    let pid = ProcessId::from_raw((i / MAX_CAPS_PER_PROCESS) as u16);
+    let slot = CapSlot::new((i % MAX_CAPS_PER_PROCESS) as u8)?;
+    Some((pid, slot))
+}
+
+impl<P: Platform> Kernel<P> {
+    /// A reference to the capability currently in `slot` of `pid`.
+    pub(crate) fn cap_ref(&self, pid: ProcessId, slot: CapSlot) -> Option<CapRef> {
+        let process = self.processes.get(pid).ok()?;
+        Some(CapRef {
+            process: pid,
+            process_generation: self.processes.generation(pid)?,
+            slot,
+            slot_generation: process.capabilities().slot_generation(slot)?,
+        })
+    }
+
+    /// Whether `r` still names a live capability.
+    pub(crate) fn resolves(&self, r: CapRef) -> bool {
+        self.cap_ref(r.process, r.slot) == Some(r)
+    }
+
+    /// Stores `cap` in `to`'s table as a child of `parent`.
+    pub(crate) fn insert_derived(
+        &mut self,
+        to: ProcessId,
+        cap: Capability,
+        parent: Option<CapRef>,
+    ) -> Result<CapSlot, KernelError> {
+        self.processes
+            .get_mut(to)?
+            .capabilities_mut()
+            .insert(cap.with_parent(parent))
+    }
+
+    /// Calls `f` with every live capability's flat index and reference.
+    fn for_each_cap(&self, mut f: impl FnMut(usize, CapRef, &Capability)) {
+        for p in 0..MAX_PROCESSES {
+            let pid = ProcessId::from_raw(p as u16);
+            let Ok(process) = self.processes.get(pid) else {
+                continue;
+            };
+            for (slot, cap) in process.capabilities().iter() {
+                if let Some(r) = self.cap_ref(pid, slot) {
+                    f(flat(pid, slot), r, cap);
+                }
+            }
+        }
+    }
+
+    /// Removes every region mapping made through `via`.
+    fn unmap_mappings_via(&mut self, via: CapRef) {
+        let mut doomed: [Option<RegionId>; domain::memory::MAX_REGIONS] =
+            [None; domain::memory::MAX_REGIONS];
+        for (slot, (id, _)) in doomed.iter_mut().zip(
+            self.regions
+                .iter()
+                .filter(|(_, r)| r.mappings().any(|m| m.via == Some(via))),
+        ) {
+            *slot = Some(id);
+        }
+        for id in doomed.into_iter().flatten() {
+            self.unmap_region_from(id, via.process);
+        }
+    }
+
+    /// Removes one capability: its mappings go, its children are adopted
+    /// by its parent.
+    pub(crate) fn delete_cap(&mut self, pid: ProcessId, slot: CapSlot) -> Result<(), KernelError> {
+        let me = self
+            .cap_ref(pid, slot)
+            .ok_or(KernelError::InvalidSlot(slot))?;
+        let grandparent = self.processes.get(pid)?.capabilities().get(slot)?.parent();
+        self.unmap_mappings_via(me);
+
+        let mut children = [false; ALL_CAPS];
+        self.for_each_cap(|i, _, cap| {
+            if cap.parent() == Some(me)
+                && let Some(c) = children.get_mut(i)
+            {
+                *c = true;
+            }
+        });
+        for (i, _) in children.iter().enumerate().filter(|(_, c)| **c) {
+            if let Some((cpid, cslot)) = unflat(i)
+                && let Ok(p) = self.processes.get_mut(cpid)
+                && let Ok(child) = p.capabilities_mut().get_mut(cslot)
+            {
+                child.set_parent(grandparent);
+            }
+        }
+        self.processes.get_mut(pid)?.capabilities_mut().remove(slot)
+    }
+
+    /// Deletes every capability derived from `slot` of `pid`, transitively,
+    /// and keeps `slot` itself.
+    pub(crate) fn revoke_subtree(
+        &mut self,
+        pid: ProcessId,
+        slot: CapSlot,
+    ) -> Result<(), KernelError> {
+        if self.cap_ref(pid, slot).is_none() {
+            return Err(KernelError::InvalidSlot(slot));
+        }
+        // Snapshot the tree as parent indices. A parent that no longer
+        // resolves cannot exist (deletion re-parents), but is treated as
+        // a root rather than trusted.
+        let mut parents: [Option<u16>; ALL_CAPS] = [None; ALL_CAPS];
+        self.for_each_cap(|i, _, cap| {
+            if let Some(p) = parents.get_mut(i) {
+                *p = cap
+                    .parent()
+                    .filter(|r| self.resolves(*r))
+                    .map(|r| flat(r.process, r.slot) as u16);
+            }
+        });
+        let root = flat(pid, slot);
+        let marked = descendants(&parents, root);
+        for (i, _) in marked.iter().enumerate().filter(|(i, m)| **m && *i != root) {
+            if let Some((dpid, dslot)) = unflat(i)
+                && let Some(r) = self.cap_ref(dpid, dslot)
+            {
+                self.unmap_mappings_via(r);
+                let _ = self
+                    .processes
+                    .get_mut(dpid)
+                    .map(|p| p.capabilities_mut().remove(dslot));
+            }
+        }
+        Ok(())
+    }
+
+    /// Deletes all of a dying process's capabilities, re-parenting their
+    /// children so revocation still reaches them.
+    pub(crate) fn delete_all_caps(&mut self, pid: ProcessId) {
+        let mut slots = [None; MAX_CAPS_PER_PROCESS];
+        if let Ok(p) = self.processes.get(pid) {
+            for (out, (slot, _)) in slots.iter_mut().zip(p.capabilities().iter()) {
+                *out = Some(slot);
+            }
+        }
+        for slot in slots.into_iter().flatten() {
+            let _ = self.delete_cap(pid, slot);
+        }
+    }
+}

crates/kernel/src/interrupt.rs

@@ -1,6 +1,6 @@
 use domain::scheduler::{Scheduler, SchedulerDecision};
 use platform::Platform;
-use types::id::{CoreId, IrqId, ThreadId};
+use types::id::CoreId;
 
 use crate::Kernel;
 
@@ -26,15 +26,26 @@ impl<P: Platform> Kernel<P> {
             self.scheduler.add(current_tid, priority, core);
             match self.scheduler.next(core) {
                 Some(next) => {
-                    if self.threads.get_mut(next).and_then(|t| t.set_running(core)).is_ok() {
+                    if self
+                        .threads
+                        .get_mut(next)
+                        .and_then(|t| t.set_running(core))
+                        .is_ok()
+                    {
                         SchedulerDecision::Preempt(next)
                     } else {
-                        let _ = self.threads.get_mut(current_tid).map(|t| t.set_running(core));
+                        let _ = self
+                            .threads
+                            .get_mut(current_tid)
+                            .map(|t| t.set_running(core));
                         SchedulerDecision::Continue
                     }
                 }
                 None => {
-                    let _ = self.threads.get_mut(current_tid).map(|t| t.set_running(core));
+                    let _ = self
+                        .threads
+                        .get_mut(current_tid)
+                        .map(|t| t.set_running(core));
                     SchedulerDecision::Continue
                 }
             }
@@ -42,22 +53,4 @@ impl<P: Platform> Kernel<P> {
             self.scheduler.tick(core, current_tid)
         }
     }
-
-    pub fn handle_interrupt(&mut self, irq: IrqId) -> Option<ThreadId> {
-        self.platform.mask_irq(irq);
-
-        let tid = self.irqs.owner(irq)?;
-        let thread = self.threads.get_mut(tid).ok()?;
-
-        if !matches!(thread.state(), domain::thread::ThreadState::Blocked(_)) {
-            return None;
-        }
-
-        let priority = thread.priority();
-        let core = self.platform.core_id();
-        let _ = thread.unblock();
-        self.scheduler.add(tid, priority, core);
-
-        Some(tid)
-    }
 }

crates/kernel/src/lib.rs

@@ -1,10 +1,30 @@
 #![no_std]
+// A kernel panic takes the whole system down, so kernel code may not
+// contain any way to panic. Tests and proofs are exempt.
+#![cfg_attr(
+    not(any(test, kani)),
+    deny(
+        clippy::unwrap_used,
+        clippy::expect_used,
+        clippy::panic,
+        clippy::unreachable,
+        clippy::todo,
+        clippy::unimplemented,
+        clippy::indexing_slicing
+    )
+)]
 
+pub mod abi;
+mod board;
+mod captree;
 pub mod interrupt;
+mod memory;
 #[cfg(kani)]
 pub mod proofs;
+mod smp;
 pub mod syscall;
 
+pub use board::BoardDevice;
 pub use syscall::{SyscallOutcome, SyscallResult};
 
 #[cfg(test)]
@@ -16,20 +36,16 @@ use domain::{
     endpoint::EndpointTable,
     error::KernelError,
     irq::IrqRoutingTable,
-    memory::{
-        page_pool::PagePool,
-        process_memory::ProcessMemory,
-        RegionTable,
-    },
-    message::Message,
-    process::{ProcessTable, MAX_PROCESSES},
+    memory::{RegionTable, frame::FrameTable, quota::Quota},
+    notification::{MAX_NOTIFICATIONS, NotificationTable},
+    process::{MAX_PROCESSES, ProcessTable},
     resource::Resource,
-    scheduler::{multi_core::MultiCoreScheduler, Scheduler},
-    syscall::WaitSet,
-    thread::{ThreadTable, ThreadState, MAX_THREADS},
+    scheduler::{Scheduler, multi_core::MultiCoreScheduler},
+    thread::{MAX_THREADS, ThreadState, ThreadTable},
 };
 use platform::Platform;
 use types::{
+    address::PhysicalAddress,
     bounded::{CapSlot, Priority},
     generation::Generation,
     id::{ProcessId, ThreadId},
@@ -43,17 +59,19 @@ pub struct Kernel<P: Platform> {
     threads: ThreadTable,
     endpoints: EndpointTable,
     scheduler: MultiCoreScheduler,
-    page_pool: PagePool,
-    process_memory: [Option<ProcessMemory>; MAX_PROCESSES],
+    frames: FrameTable,
+    quotas: [Quota; MAX_PROCESSES],
     regions: RegionTable,
     irqs: IrqRoutingTable,
-    pending_messages: [Option<Message>; MAX_THREADS],
+    notifications: NotificationTable,
+    ipc: [syscall::IpcState; MAX_THREADS],
     pending_results: [Option<SyscallResult>; MAX_THREADS],
-    wait_sets: [Option<WaitSet>; MAX_THREADS],
+    /// The core each thread runs on (see smp.rs).
+    homes: [types::id::CoreId; MAX_THREADS],
 }
 
 impl<P: Platform> Kernel<P> {
-    pub fn new(platform: P, page_pool: PagePool) -> Self {
+    pub fn new(platform: P, pool_base: PhysicalAddress, pool_pages: usize) -> Self {
         let num_cores = platform.num_cores();
         Self {
             platform,
@@ -61,13 +79,47 @@ impl<P: Platform> Kernel<P> {
             threads: ThreadTable::new(),
             endpoints: EndpointTable::new(),
             scheduler: MultiCoreScheduler::new(num_cores),
-            page_pool,
-            process_memory: [const { None }; MAX_PROCESSES],
+            frames: FrameTable::new(pool_base, pool_pages),
+            quotas: [Quota::default(); MAX_PROCESSES],
             regions: RegionTable::new(),
             irqs: IrqRoutingTable::new(),
-            pending_messages: [const { None }; MAX_THREADS],
+            notifications: NotificationTable::new(),
+            ipc: [syscall::IpcState::default(); MAX_THREADS],
             pending_results: [const { None }; MAX_THREADS],
-            wait_sets: [const { None }; MAX_THREADS],
+            homes: [types::id::CoreId::from_raw(0); MAX_THREADS],
+        }
+    }
+
+    /// Builds the kernel directly in `slot`, one table at a time, so the
+    /// whole structure never has to fit on the (small) boot stack.
+    ///
+    /// # Safety
+    /// `slot` must be valid for writes and properly aligned. Any previous
+    /// value is overwritten without being dropped.
+    pub unsafe fn init_in_place(
+        slot: *mut Self,
+        platform: P,
+        pool_base: PhysicalAddress,
+        pool_pages: usize,
+    ) {
+        use core::ptr::addr_of_mut;
+        let num_cores = platform.num_cores();
+        // SAFETY: the caller guarantees `slot` is valid and aligned; each
+        // field is written exactly once.
+        unsafe {
+            addr_of_mut!((*slot).platform).write(platform);
+            addr_of_mut!((*slot).processes).write(ProcessTable::new());
+            addr_of_mut!((*slot).threads).write(ThreadTable::new());
+            addr_of_mut!((*slot).endpoints).write(EndpointTable::new());
+            addr_of_mut!((*slot).scheduler).write(MultiCoreScheduler::new(num_cores));
+            addr_of_mut!((*slot).frames).write(FrameTable::new(pool_base, pool_pages));
+            addr_of_mut!((*slot).quotas).write([Quota::default(); MAX_PROCESSES]);
+            addr_of_mut!((*slot).regions).write(RegionTable::new());
+            addr_of_mut!((*slot).irqs).write(IrqRoutingTable::new());
+            addr_of_mut!((*slot).notifications).write(NotificationTable::new());
+            addr_of_mut!((*slot).ipc).write([syscall::IpcState::default(); MAX_THREADS]);
+            addr_of_mut!((*slot).pending_results).write([const { None }; MAX_THREADS]);
+            addr_of_mut!((*slot).homes).write([types::id::CoreId::from_raw(0); MAX_THREADS]);
         }
     }
 
@@ -77,20 +129,25 @@ impl<P: Platform> Kernel<P> {
         time_slice: TimeSlice,
     ) -> Result<(ProcessId, ThreadId), KernelError> {
         let pid = self.processes.create(CapabilityTable::new(), None)?;
+        if let Err(e) = self.create_address_space(pid) {
+            let _ = self.processes.destroy(pid);
+            return Err(e);
+        }
         let tid = self.threads.spawn(pid, priority, time_slice, None)?;
         self.processes.get_mut(pid)?.add_thread(tid)?;
 
-        self.process_memory[pid.raw() as usize] =
-            Some(ProcessMemory::new(pid, ProcessMemory::DEFAULT_PAGE_LIMIT));
-
         let cap = Capability::new(
             Resource::ProcessCreate,
             PermissionSet::empty().with(Permission::Execute),
             Generation::initial(),
         );
-        self.processes.get_mut(pid)?.capabilities_mut().insert(cap)?;
+        self.processes
+            .get_mut(pid)?
+            .capabilities_mut()
+            .insert(cap)?;
 
         let core = self.platform.core_id();
+        self.set_home(tid, core);
         self.scheduler.add(tid, priority, core);
         self.scheduler.next(core);
         self.threads.get_mut(tid)?.set_running(core)?;
@@ -102,21 +159,21 @@ impl<P: Platform> Kernel<P> {
     }
 
     pub fn pending_result(&self, thread: ThreadId) -> Option<&SyscallResult> {
-        self.pending_results[thread.raw() as usize].as_ref()
+        self.pending_results.get(thread.raw() as usize)?.as_ref()
     }
 
     pub fn take_pending_result(&mut self, thread: ThreadId) -> Option<SyscallResult> {
-        self.pending_results[thread.raw() as usize].take()
+        self.pending_results.get_mut(thread.raw() as usize)?.take()
     }
 
-    pub fn set_thread_running(&mut self, tid: ThreadId, core: types::id::CoreId) -> Result<(), domain::error::KernelError> {
+    pub fn set_thread_running(
+        &mut self,
+        tid: ThreadId,
+        core: types::id::CoreId,
+    ) -> Result<(), domain::error::KernelError> {
         self.threads.get_mut(tid)?.set_running(core)
     }
 
-    pub fn free_page_count(&self) -> usize {
-        self.page_pool.free_count()
-    }
-
     pub fn process_exists(&self, pid: ProcessId) -> bool {
         self.processes.get(pid).is_ok()
     }
@@ -125,8 +182,14 @@ impl<P: Platform> Kernel<P> {
         self.threads.get(tid).ok().map(|t| t.saved_context())
     }
 
-    pub fn thread_context_mut(&mut self, tid: ThreadId) -> Option<&mut domain::thread::SavedContext> {
-        self.threads.get_mut(tid).ok().map(|t| t.saved_context_mut())
+    pub fn thread_context_mut(
+        &mut self,
+        tid: ThreadId,
+    ) -> Option<&mut domain::thread::SavedContext> {
+        self.threads
+            .get_mut(tid)
+            .ok()
+            .map(|t| t.saved_context_mut())
     }
 
     pub fn thread_process(&self, tid: ThreadId) -> Option<ProcessId> {
@@ -146,30 +209,31 @@ impl<P: Platform> Kernel<P> {
 
     pub fn create_process_internal(&mut self) -> Option<ProcessId> {
         let pid = self.processes.create(CapabilityTable::new(), None).ok()?;
-        self.process_memory[pid.raw() as usize] =
-            Some(domain::memory::process_memory::ProcessMemory::new(pid, ProcessMemory::DEFAULT_PAGE_LIMIT));
+        if self.create_address_space(pid).is_err() {
+            let _ = self.processes.destroy(pid);
+            return None;
+        }
         Some(pid)
     }
 
-    pub fn spawn_thread_internal(
-        &mut self,
-        pid: ProcessId,
-    ) -> Option<ThreadId> {
-        use domain::scheduler::Scheduler;
-        let tid = self.threads.spawn(
-            pid,
-            Priority::DEFAULT,
-            TimeSlice::DEFAULT,
-            None,
-        ).ok()?;
+    pub fn spawn_thread_internal(&mut self, pid: ProcessId) -> Option<ThreadId> {
+        let tid = self
+            .threads
+            .spawn(pid, Priority::DEFAULT, TimeSlice::DEFAULT, None)
+            .ok()?;
         let _ = self.processes.get_mut(pid).map(|p| p.add_thread(tid));
-        let core = self.platform.core_id();
-        self.scheduler.add(tid, Priority::DEFAULT, core);
+        self.place(tid);
+        self.make_ready(tid, Priority::DEFAULT);
         Some(tid)
     }
 
-    pub fn create_endpoint(&mut self) -> Result<types::id::EndpointId, KernelError> {
-        self.endpoints.create().ok_or(KernelError::NoFreeSlot)
+    /// Creates an endpoint owned by `owner`; it is destroyed with `owner`.
+    pub fn create_endpoint(
+        &mut self,
+        owner: ProcessId,
+    ) -> Result<types::id::EndpointId, KernelError> {
+        self.processes.get(owner)?;
+        self.endpoints.create(owner).ok_or(KernelError::NoFreeSlot)
     }
 
     pub fn grant_capability(
@@ -181,34 +245,11 @@ impl<P: Platform> Kernel<P> {
         self.grant_cap(to, resource, permissions)
     }
 
-    pub fn switch_to_thread(&mut self, tid: ThreadId) {
-        use domain::scheduler::Scheduler;
-        let core = self.platform.core_id();
-
-        if let Some(current) = self.scheduler.current(core) {
-            if current == tid {
-                return;
-            }
-            if let Ok(t) = self.threads.get_mut(current) {
-                if matches!(t.state(), ThreadState::Running(_)) {
-                    let priority = t.priority();
-                    let _ = t.preempt();
-                    self.scheduler.add(current, priority, core);
-                }
-            }
-        }
-
-        if let Ok(t) = self.threads.get(tid) {
-            if matches!(t.state(), ThreadState::Ready) {
-                self.scheduler.next(core);
-                let _ = self.threads.get_mut(tid).map(|t| t.set_running(core));
-            }
-        }
-    }
-
     fn caller(&self) -> Result<(ThreadId, ProcessId), KernelError> {
         let core = self.platform.core_id();
-        let tid = self.scheduler.current(core)
+        let tid = self
+            .scheduler
+            .current(core)
             .ok_or(KernelError::WouldBlock)?;
         let thread = self.threads.get(tid)?;
         match thread.state() {
@@ -220,11 +261,12 @@ impl<P: Platform> Kernel<P> {
     pub(crate) fn destroy_process(&mut self, pid: ProcessId) {
         use domain::process::MAX_THREADS_PER_PROCESS;
 
-        let thread_ids: [Option<ThreadId>; MAX_THREADS_PER_PROCESS] = match self.processes.get(pid) {
+        let thread_ids: [Option<ThreadId>; MAX_THREADS_PER_PROCESS] = match self.processes.get(pid)
+        {
             Ok(p) => {
                 let mut ids = [None; MAX_THREADS_PER_PROCESS];
-                for (i, tid) in p.thread_ids().enumerate() {
-                    if i < MAX_THREADS_PER_PROCESS { ids[i] = Some(tid); }
+                for (slot, tid) in ids.iter_mut().zip(p.thread_ids()) {
+                    *slot = Some(tid);
                 }
                 ids
             }
@@ -232,48 +274,76 @@ impl<P: Platform> Kernel<P> {
         };
 
         self.cleanup_threads(&thread_ids);
-
-        // Free allocated pages back to pool
-        if let Some(pm) = &self.process_memory[pid.raw() as usize] {
-            for &(pa, count) in pm.allocations() {
-                self.page_pool.free(pa, count);
-            }
-        }
-
-        // Unblock threads in other processes that were blocked waiting
-        // on endpoints where this process's threads were the other side.
-        // The cleanup_threads call above already removed this process's
-        // threads from all endpoint wait queues. Threads blocked waiting
-        // for this process will eventually time out or be rescheduled
-        // when the endpoint is revoked.
+        self.delete_all_caps(pid);
+        self.destroy_endpoints_owned_by(pid);
+        self.destroy_notifications_owned_by(pid);
+        self.teardown_memory(pid);
 
         let _ = self.processes.destroy(pid);
-        self.process_memory[pid.raw() as usize] = None;
     }
 
     pub(crate) fn cleanup_threads(&mut self, thread_ids: &[Option<ThreadId>]) {
         use domain::scheduler::Scheduler;
-        for slot in thread_ids {
-            if let Some(tid) = slot {
+        for tid in thread_ids.iter().flatten() {
             self.endpoints.remove_thread_from_all(*tid);
-                self.cleanup_wait_any(*tid);
+            self.notifications.remove_thread_from_all(*tid);
+            let ipc = self.ipc_mut(*tid).map(core::mem::take).unwrap_or_default();
+            if let Some(caller) = ipc.reply_to {
+                self.release_caller(caller);
+            }
+            self.evict(*tid);
             self.scheduler.remove(*tid);
-                self.pending_messages[tid.raw() as usize] = None;
-                self.pending_results[tid.raw() as usize] = None;
+            self.set_pending_result(*tid, None);
             let _ = self.threads.destroy(*tid);
         }
     }
+
+    /// Destroys every endpoint `owner` created, waking anyone blocked on
+    /// them with an error instead of leaving them blocked forever.
+    pub(crate) fn destroy_endpoints_owned_by(&mut self, owner: ProcessId) {
+        let mut owned = [None; domain::endpoint::MAX_ENDPOINTS];
+        for (slot, id) in owned.iter_mut().zip(self.endpoints.ids_owned_by(owner)) {
+            *slot = Some(id);
+        }
+        for id in owned.into_iter().flatten() {
+            let Some(mut ep) = self.endpoints.destroy(id) else {
+                continue;
+            };
+            while let Some(tid) = ep.dequeue_sender().or_else(|| ep.dequeue_receiver()) {
+                self.wake_with_error(tid, KernelError::InvalidEndpoint(id));
+            }
+        }
     }
 
-    pub(crate) fn cleanup_wait_any(&mut self, tid: ThreadId) {
-        if let Some(wait_set) = self.wait_sets[tid.raw() as usize].take() {
-            for ep_slot in wait_set.endpoints() {
-                if let Some(_slot) = ep_slot {
-                    self.endpoints.remove_thread_from_all(tid);
-                    break;
+    /// Destroys every notification `owner` created, waking its waiters
+    /// with an error and unbinding its bound thread.
+    pub(crate) fn destroy_notifications_owned_by(&mut self, owner: ProcessId) {
+        let mut owned = [None; MAX_NOTIFICATIONS];
+        for (slot, id) in owned.iter_mut().zip(self.notifications.ids_owned_by(owner)) {
+            *slot = Some(id);
+        }
+        for id in owned.into_iter().flatten() {
+            let Some(mut n) = self.notifications.destroy(id) else {
+                continue;
+            };
+            if let Some(bound) = n.bound()
+                && let Some(s) = self.ipc_mut(bound)
+            {
+                s.bound = None;
+            }
+            while let Some(tid) = n.pop_waiter() {
+                self.wake_with_error(tid, KernelError::NoSuchObject);
             }
         }
     }
+
+    /// Makes a blocked thread runnable with `error` as its syscall result,
+    /// dropping whatever it was about to send.
+    fn wake_with_error(&mut self, tid: ThreadId, error: KernelError) {
+        if let Some(s) = self.ipc_mut(tid) {
+            s.outgoing = None;
+        }
+        self.wake(tid, SyscallResult::Error(error));
     }
 
     fn check_cap(
@@ -287,43 +357,24 @@ impl<P: Platform> Kernel<P> {
         if !cap.permissions().allows(needed) {
             return Err(KernelError::PermissionDenied { slot, needed });
         }
-        let current_gen = self.resource_generation(cap.resource());
-        if !cap.generation().is_valid_against(&current_gen) {
-            return Err(KernelError::RevokedCapability(slot));
-        }
-        Ok(cap)
-    }
-
-    fn resource_generation(&self, resource: &Resource) -> Generation {
-        match resource {
-            Resource::Endpoint(id) => self
-                .endpoints
-                .get(*id)
-                .map(|ep| *ep.generation())
-                .unwrap_or_else(|| Generation::initial()),
-            Resource::Memory(id) => self
-                .regions
-                .get(*id)
-                .map(|r| *r.generation())
-                .unwrap_or_else(|| Generation::initial()),
-            _ => Generation::initial(),
+        match self.resource_generation(cap.resource()) {
+            Some(current) if cap.generation().is_valid_against(&current) => Ok(cap),
+            _ => Err(KernelError::RevokedCapability(slot)),
         }
     }
 
-    pub fn revoke_resource(&mut self, resource: &Resource) {
+    /// The generation a capability to `resource` must carry, or `None` if
+    /// the object no longer exists.
+    fn resource_generation(&self, resource: &Resource) -> Option<Generation> {
         match resource {
-            Resource::Endpoint(id) => {
-                if let Some(ep) = self.endpoints.get_mut(*id) {
-                    ep.revoke();
+            Resource::Endpoint(id) => self.endpoints.generation(*id),
+            Resource::Memory(id) => self.regions.generation(*id),
+            Resource::Notification(id) => self.notifications.generation(*id),
+            Resource::Process(pid) => self.processes.generation(*pid),
+            Resource::Interrupt(_) | Resource::ProcessCreate | Resource::SystemControl => {
+                Some(Generation::initial())
             }
         }
-            Resource::Memory(id) => {
-                if let Some(r) = self.regions.get_mut(*id) {
-                    r.revoke();
-                }
-            }
-            _ => {}
-        }
     }
 
     fn grant_cap(
@@ -332,7 +383,9 @@ impl<P: Platform> Kernel<P> {
         resource: Resource,
         permissions: PermissionSet,
     ) -> Result<CapSlot, KernelError> {
-        let generation = self.resource_generation(&resource);
+        let generation = self
+            .resource_generation(&resource)
+            .ok_or(KernelError::NoSuchObject)?;
         let cap = Capability::new(resource, permissions, generation);
         self.processes.get_mut(to)?.capabilities_mut().insert(cap)
     }

crates/kernel/src/memory.rs

@@ -0,0 +1,486 @@
+//! Address-space bookkeeping. The kernel decides every user mapping from
+//! its own records (`FrameTable`, `RegionTable`, quotas) and only then tells
+//! the platform to apply it; it never asks the hardware what is mapped.
+
+use domain::{
+    error::KernelError,
+    memory::{
+        Region, RegionBacking, RegionMapping,
+        frame::{FrameTable, FrameUse, PAGE_SIZE},
+        quota::Quota,
+    },
+};
+use platform::{FrameSource, MapError, Platform};
+use types::{
+    address::{PhysicalAddress, VirtualAddress},
+    bounded::PageCount,
+    id::{ProcessId, RegionId},
+    mapping::PagePerms,
+};
+
+use crate::Kernel;
+
+/// First VA the kernel considers when picking a spot for `RequestPages`.
+/// Below it sit the program image and boot-time device windows.
+pub(crate) const USER_HEAP_START: usize = 0x40000;
+
+/// Page-table frames for one address space, charged to its owner.
+struct ChargedFrames<'a> {
+    frames: &'a mut FrameTable,
+    quota: &'a mut Quota,
+    owner: ProcessId,
+}
+
+impl FrameSource for ChargedFrames<'_> {
+    fn alloc_table_frame(&mut self) -> Option<PhysicalAddress> {
+        if !self.quota.charge(1) {
+            return None;
+        }
+        match self.frames.alloc(FrameUse::PageTable { owner: self.owner }) {
+            Some(pa) => Some(pa),
+            None => {
+                self.quota.uncharge(1);
+                None
+            }
+        }
+    }
+}
+
+fn map_error(e: MapError) -> KernelError {
+    match e {
+        MapError::OutOfFrames => KernelError::OutOfMemory,
+        MapError::InvalidAddress => KernelError::InvalidAddress,
+        MapError::NoAddressSpace => KernelError::OutOfMemory,
+    }
+}
+
+impl<P: Platform> Kernel<P> {
+    /// Whether `[va, va + pages)` is page aligned and inside the user window.
+    pub(crate) fn in_user_window(va: VirtualAddress, pages: usize) -> bool {
+        let start = va.raw();
+        let Some(len) = pages.checked_mul(PAGE_SIZE) else {
+            return false;
+        };
+        let Some(end) = start.checked_add(len) else {
+            return false;
+        };
+        pages > 0
+            && start.is_multiple_of(PAGE_SIZE)
+            && start >= P::USER_VA_START
+            && end <= P::USER_VA_END
+    }
+
+    fn is_mapped(&self, pid: ProcessId, va: VirtualAddress) -> bool {
+        self.frames.find_user(pid, va).is_some() || self.regions.covering(pid, va).is_some()
+    }
+
+    fn range_is_free(&self, pid: ProcessId, va: VirtualAddress, pages: usize) -> bool {
+        (0..pages).all(|i| !self.is_mapped(pid, page_at(va, i)))
+    }
+
+    fn quota_mut(&mut self, pid: ProcessId) -> Result<&mut Quota, KernelError> {
+        self.quotas
+            .get_mut(pid.raw() as usize)
+            .ok_or(KernelError::InvalidProcess(pid))
+    }
+
+    pub fn page_usage(&self, pid: ProcessId) -> usize {
+        self.quotas.get(pid.raw() as usize).map_or(0, Quota::used)
+    }
+
+    pub fn set_page_limit(&mut self, pid: ProcessId, limit: usize) -> Result<(), KernelError> {
+        self.processes.get(pid)?;
+        if self.quota_mut(pid)?.set_limit(limit) {
+            Ok(())
+        } else {
+            Err(KernelError::OutOfMemory)
+        }
+    }
+
+    pub fn free_page_count(&self) -> usize {
+        self.frames.free_count()
+    }
+
+    /// Maps `pa` at `va` in `pid`, building page tables on `pid`'s quota.
+    fn platform_map(
+        &mut self,
+        pid: ProcessId,
+        va: VirtualAddress,
+        pa: PhysicalAddress,
+        perms: PagePerms,
+    ) -> Result<(), KernelError> {
+        let quota = self
+            .quotas
+            .get_mut(pid.raw() as usize)
+            .ok_or(KernelError::InvalidProcess(pid))?;
+        let mut source = ChargedFrames {
+            frames: &mut self.frames,
+            quota,
+            owner: pid,
+        };
+        self.platform
+            .map_page(pid, va, pa, perms, &mut source)
+            .map_err(map_error)
+    }
+
+    pub(crate) fn create_address_space(&mut self, pid: ProcessId) -> Result<(), KernelError> {
+        let quota = self
+            .quotas
+            .get_mut(pid.raw() as usize)
+            .ok_or(KernelError::InvalidProcess(pid))?;
+        *quota = Quota::default();
+        let mut source = ChargedFrames {
+            frames: &mut self.frames,
+            quota,
+            owner: pid,
+        };
+        let created = self
+            .platform
+            .create_address_space(pid, &mut source)
+            .map_err(map_error);
+        if created.is_err() {
+            self.frames.free_owned_by(pid);
+            if let Some(q) = self.quotas.get_mut(pid.raw() as usize) {
+                *q = Quota::default();
+            }
+        }
+        created
+    }
+
+    /// Allocates, zeroes and maps one fresh page for `pid` at `va`.
+    fn map_fresh_page(
+        &mut self,
+        pid: ProcessId,
+        va: VirtualAddress,
+        perms: PagePerms,
+    ) -> Result<PhysicalAddress, KernelError> {
+        let usage = FrameUse::user(pid, va, perms).ok_or(KernelError::InvalidAddress)?;
+        if !self.quota_mut(pid)?.charge(1) {
+            return Err(KernelError::OutOfMemory);
+        }
+        let Some(pa) = self.frames.alloc(usage) else {
+            self.quota_mut(pid)?.uncharge(1);
+            return Err(KernelError::OutOfMemory);
+        };
+        self.platform.zero_frame(pa);
+        if let Err(e) = self.platform_map(pid, va, pa, perms) {
+            self.frames.free(pa);
+            self.quota_mut(pid)?.uncharge(1);
+            return Err(e);
+        }
+        Ok(pa)
+    }
+
+    /// Removes one user page of `pid` and returns its frame to the pool.
+    fn unmap_and_free(&mut self, pid: ProcessId, va: VirtualAddress) {
+        if let Some((pa, _)) = self.frames.find_user(pid, va) {
+            self.platform.unmap_page(pid, va);
+            self.frames.free(pa);
+            if let Some(q) = self.quotas.get_mut(pid.raw() as usize) {
+                q.uncharge(1);
+            }
+        }
+    }
+
+    /// Frame backing the user page at `va` in `pid`. Lets boot code fill
+    /// pages it has just mapped for a process.
+    pub fn user_page_frame(&self, pid: ProcessId, va: VirtualAddress) -> Option<PhysicalAddress> {
+        self.frames.find_user(pid, va).map(|(pa, _)| pa)
+    }
+
+    /// Maps `pages` fresh zeroed pages at `va`, all or nothing.
+    pub fn map_fresh_range(
+        &mut self,
+        pid: ProcessId,
+        va: VirtualAddress,
+        pages: usize,
+        perms: PagePerms,
+    ) -> Result<(), KernelError> {
+        if !Self::in_user_window(va, pages) {
+            return Err(KernelError::InvalidAddress);
+        }
+        if !self.range_is_free(pid, va, pages) {
+            return Err(KernelError::AddressInUse);
+        }
+        for i in 0..pages {
+            if let Err(e) = self.map_fresh_page(pid, page_at(va, i), perms) {
+                for j in 0..i {
+                    self.unmap_and_free(pid, page_at(va, j));
+                }
+                return Err(e);
+            }
+        }
+        Ok(())
+    }
+
+    /// First-fit search for `pages` free pages in the heap part of the window.
+    pub(crate) fn find_free_heap_range(
+        &self,
+        pid: ProcessId,
+        pages: usize,
+    ) -> Option<VirtualAddress> {
+        let mut candidate = USER_HEAP_START.max(P::USER_VA_START);
+        while Self::in_user_window(VirtualAddress::from_raw(candidate), pages) {
+            let va = VirtualAddress::from_raw(candidate);
+            match (0..pages).find(|&i| self.is_mapped(pid, page_at(va, i))) {
+                None => return Some(va),
+                Some(busy) => candidate += (busy + 1) * PAGE_SIZE,
+            }
+        }
+        None
+    }
+
+    /// Validates that every page of the range is a user page `pid` owns,
+    /// then releases them all.
+    pub(crate) fn release_range(
+        &mut self,
+        pid: ProcessId,
+        va: VirtualAddress,
+        pages: usize,
+    ) -> Result<(), KernelError> {
+        if !Self::in_user_window(va, pages) {
+            return Err(KernelError::InvalidAddress);
+        }
+        if !(0..pages).all(|i| self.frames.find_user(pid, page_at(va, i)).is_some()) {
+            return Err(KernelError::InvalidAddress);
+        }
+        for i in 0..pages {
+            self.unmap_and_free(pid, page_at(va, i));
+        }
+        Ok(())
+    }
+
+    /// Moves the page at `src` in `from` to `dst` in `to`. The frame and its
+    /// quota charge change hands; `from` loses access.
+    pub(crate) fn move_page(
+        &mut self,
+        from: ProcessId,
+        src: VirtualAddress,
+        to: ProcessId,
+        dst: VirtualAddress,
+        perms: PagePerms,
+    ) -> Result<(), KernelError> {
+        if !Self::in_user_window(src, 1) || !Self::in_user_window(dst, 1) {
+            return Err(KernelError::InvalidAddress);
+        }
+        let (pa, _) = self
+            .frames
+            .find_user(from, src)
+            .ok_or(KernelError::InvalidAddress)?;
+        self.processes.get(to)?;
+        if !self.range_is_free(to, dst, 1) {
+            return Err(KernelError::AddressInUse);
+        }
+        let usage = FrameUse::user(to, dst, perms).ok_or(KernelError::InvalidAddress)?;
+        if !self.quota_mut(to)?.charge(1) {
+            return Err(KernelError::OutOfMemory);
+        }
+        if let Err(e) = self.platform_map(to, dst, pa, perms) {
+            self.quota_mut(to)?.uncharge(1);
+            return Err(e);
+        }
+        self.platform.unmap_page(from, src);
+        self.frames.retag(pa, usage);
+        self.quota_mut(from)?.uncharge(1);
+        Ok(())
+    }
+
+    /// Allocates a physically contiguous, zeroed region charged to `owner`.
+    pub fn create_pool_region(
+        &mut self,
+        owner: ProcessId,
+        pages: PageCount,
+    ) -> Result<RegionId, KernelError> {
+        self.processes.get(owner)?;
+        let id = self.regions.next_free_id().ok_or(KernelError::NoFreeSlot)?;
+        let count = pages.value() as usize;
+        if !self.quota_mut(owner)?.charge(count) {
+            return Err(KernelError::OutOfMemory);
+        }
+        let Some(base) = self
+            .frames
+            .alloc_contiguous(count, |_| FrameUse::Region { region: id })
+        else {
+            self.quota_mut(owner)?.uncharge(count);
+            return Err(KernelError::OutOfMemory);
+        };
+        for i in 0..count {
+            self.platform.zero_frame(base.offset(i));
+        }
+        self.regions
+            .insert(Region::new(owner, RegionBacking::Pool, base, pages))
+            .ok_or(KernelError::NoFreeSlot)
+    }
+
+    /// Describes device memory at `base` so it can be mapped like a region.
+    pub fn create_device_region(
+        &mut self,
+        owner: ProcessId,
+        base: PhysicalAddress,
+        pages: PageCount,
+    ) -> Result<RegionId, KernelError> {
+        self.processes.get(owner)?;
+        if !base.raw().is_multiple_of(PAGE_SIZE) {
+            return Err(KernelError::InvalidAddress);
+        }
+        // Device memory must never alias frames the kernel hands out.
+        let len = pages.value() as usize * PAGE_SIZE;
+        let start = base.raw();
+        let end = start.checked_add(len).ok_or(KernelError::InvalidAddress)?;
+        let pool_start = self.frames.base().raw();
+        let pool_end = pool_start + self.frames.capacity() * PAGE_SIZE;
+        if start < pool_end && end > pool_start {
+            return Err(KernelError::InvalidAddress);
+        }
+        // Nor another device's window: each device has one region, so
+        // revoking or delegating it means the same thing everywhere.
+        let overlaps = self.regions.iter().any(|(_, r)| {
+            let r_start = r.base().raw();
+            let r_end = r_start.saturating_add(r.pages().value() as usize * PAGE_SIZE);
+            r.backing() == RegionBacking::Device && start < r_end && end > r_start
+        });
+        if overlaps {
+            return Err(KernelError::AddressInUse);
+        }
+        self.regions
+            .insert(Region::new(owner, RegionBacking::Device, base, pages))
+            .ok_or(KernelError::NoFreeSlot)
+    }
+
+    pub fn region_base(&self, id: RegionId) -> Option<PhysicalAddress> {
+        self.regions.get(id).map(Region::base)
+    }
+
+    pub fn region_pages(&self, id: RegionId) -> Option<PageCount> {
+        self.regions.get(id).map(Region::pages)
+    }
+
+    /// Maps all of region `id` at `va` in `pid`, all or nothing.
+    /// Maps region `id` for boot code; the mapping is not tied to any
+    /// capability and lasts until the region or the process dies.
+    pub fn map_region(
+        &mut self,
+        id: RegionId,
+        pid: ProcessId,
+        va: VirtualAddress,
+        perms: PagePerms,
+    ) -> Result<(), KernelError> {
+        self.map_region_via(id, pid, va, perms, None)
+    }
+
+    /// Maps all of region `id` at `va` in `pid`, all or nothing. A mapping
+    /// made through a capability (`via`) is removed when that capability
+    /// is deleted.
+    pub(crate) fn map_region_via(
+        &mut self,
+        id: RegionId,
+        pid: ProcessId,
+        va: VirtualAddress,
+        perms: PagePerms,
+        via: Option<domain::capability::CapRef>,
+    ) -> Result<(), KernelError> {
+        self.processes.get(pid)?;
+        let region = self.regions.get(id).ok_or(KernelError::InvalidRegion)?;
+        let (base, pages) = (region.base(), region.pages().value() as usize);
+        if region.mappings().any(|m| m.process == pid) {
+            return Err(KernelError::AddressInUse);
+        }
+        // W^X holds across processes too: nobody may write what someone
+        // else can execute.
+        let clashes = |other: PagePerms| {
+            matches!(
+                (perms, other),
+                (PagePerms::ReadWrite, PagePerms::ReadExecute)
+                    | (PagePerms::ReadExecute, PagePerms::ReadWrite)
+            )
+        };
+        if region.mappings().any(|m| clashes(m.perms)) {
+            return Err(KernelError::WritableAndExecutable);
+        }
+        if !Self::in_user_window(va, pages) {
+            return Err(KernelError::InvalidAddress);
+        }
+        if !self.range_is_free(pid, va, pages) {
+            return Err(KernelError::AddressInUse);
+        }
+        for i in 0..pages {
+            if let Err(e) = self.platform_map(pid, page_at(va, i), base.offset(i), perms) {
+                for j in 0..i {
+                    self.platform.unmap_page(pid, page_at(va, j));
+                }
+                return Err(e);
+            }
+        }
+        let recorded = self.regions.get_mut(id).is_some_and(|r| {
+            r.add_mapping(RegionMapping {
+                process: pid,
+                va,
+                perms,
+                via,
+            })
+        });
+        if !recorded {
+            for i in 0..pages {
+                self.platform.unmap_page(pid, page_at(va, i));
+            }
+            return Err(KernelError::NoFreeSlot);
+        }
+        Ok(())
+    }
+
+    /// Removes `pid`'s mapping of region `id`, if it has one.
+    pub(crate) fn unmap_region_from(&mut self, id: RegionId, pid: ProcessId) {
+        let Some(region) = self.regions.get_mut(id) else {
+            return;
+        };
+        let pages = region.pages().value() as usize;
+        if let Some(m) = region.remove_mapping(pid) {
+            for i in 0..pages {
+                self.platform.unmap_page(pid, page_at(m.va, i));
+            }
+        }
+    }
+
+    /// Frees regions owned by `pid` (unmapping them from every other
+    /// process) and forgets `pid`'s mappings of other regions.
+    fn teardown_regions(&mut self, pid: ProcessId) {
+        let mut owned = [None; domain::memory::MAX_REGIONS];
+        for (slot, id) in owned.iter_mut().zip(self.regions.ids_owned_by(pid)) {
+            *slot = Some(id);
+        }
+        for id in owned.into_iter().flatten() {
+            let Some(region) = self.regions.remove(id) else {
+                continue;
+            };
+            let pages = region.pages().value() as usize;
+            for m in region.mappings().filter(|m| m.process != pid) {
+                for i in 0..pages {
+                    self.platform.unmap_page(m.process, page_at(m.va, i));
+                }
+            }
+            if region.backing() == RegionBacking::Pool {
+                for i in 0..pages {
+                    self.frames.free(region.base().offset(i));
+                }
+            }
+        }
+        for (_, region) in self.regions.iter_mut() {
+            region.remove_mapping(pid);
+        }
+    }
+
+    /// Releases everything `pid` holds in memory: its address space, page
+    /// tables, user pages and owned regions.
+    pub(crate) fn teardown_memory(&mut self, pid: ProcessId) {
+        self.teardown_regions(pid);
+        self.platform.destroy_address_space(pid);
+        self.frames.free_owned_by(pid);
+        if let Some(q) = self.quotas.get_mut(pid.raw() as usize) {
+            *q = Quota::default();
+        }
+    }
+}
+
+fn page_at(base: VirtualAddress, i: usize) -> VirtualAddress {
+    VirtualAddress::from_raw(base.raw() + i * PAGE_SIZE)
+}

crates/kernel/src/proofs/abi.rs

@@ -0,0 +1,75 @@
+use crate::abi::{decode, encode};
+use crate::syscall::SyscallResult;
+use domain::error::KernelError;
+use domain::syscall::Syscall;
+use types::bounded::CapSlot;
+use types::syscall_abi::*;
+
+/// No register contents can make decoding panic or overflow.
+#[kani::proof]
+fn decode_is_total() {
+    let nr: usize = kani::any();
+    let args: [usize; 6] = kani::any();
+    let _ = decode(nr, &args);
+}
+
+/// A decoded slot argument is exactly the register it came from.
+#[kani::proof]
+fn decoded_slots_match_their_registers() {
+    let args: [usize; 6] = kani::any();
+    if let Some(Syscall::Receive { endpoint }) = decode(SYS_RECEIVE, &args) {
+        assert!(endpoint.value() as usize == args[0]);
+    }
+    if let Some(Syscall::Delegate {
+        slot, to_endpoint, ..
+    }) = decode(SYS_DELEGATE, &args)
+    {
+        assert!(slot.value() as usize == args[0]);
+        assert!(to_endpoint.value() as usize == args[1]);
+    }
+}
+
+/// What libkos encodes for a Send is decoded back to the same message.
+#[kani::proof]
+fn send_roundtrips() {
+    let ep = CapSlot::new(kani::any::<u8>() % (CapSlot::MAX + 1)).unwrap();
+    let words: [usize; 4] = kani::any();
+    let cap = if kani::any() {
+        CapSlot::new(kani::any::<u8>() % (CapSlot::MAX + 1))
+    } else {
+        None
+    };
+    let regs = message_regs(ep.value() as usize, words, cap);
+    match decode(SYS_SEND, &regs) {
+        Some(Syscall::Send { endpoint, message }) => {
+            assert!(endpoint == ep);
+            assert!(*message.words() == words);
+            assert!(message.cap() == cap);
+        }
+        _ => panic!("valid send did not decode"),
+    }
+}
+
+/// A failed syscall always reports a real, non-zero error code.
+#[kani::proof]
+fn errors_encode_to_valid_codes() {
+    let e = match kani::any::<u8>() % 6 {
+        0 => KernelError::NoReply,
+        1 => KernelError::OutOfMemory,
+        2 => KernelError::InvalidAddress,
+        3 => KernelError::WrongObject,
+        4 => KernelError::NoSuchObject,
+        _ => KernelError::InvalidSlot(CapSlot::new(0).unwrap()),
+    };
+    let regs = encode(&SyscallResult::Error(e));
+    assert!(regs[0] != 0);
+    assert!(ErrorCode::from_raw(regs[0]).is_some());
+}
+
+#[kani::proof]
+fn successes_report_status_zero() {
+    let v: usize = kani::any();
+    assert!(encode(&SyscallResult::Ok)[0] == 0);
+    let regs = encode(&SyscallResult::Value(v));
+    assert!(regs[0] == 0 && regs[1] == v);
+}

crates/kernel/src/proofs/authority.rs

@@ -0,0 +1,118 @@
+//! Mint creates no authority. The real kernel, with tables shrunk under
+//! `cfg(kani)`, runs `mint` with arbitrary arguments in a small state
+//! whose capabilities carry arbitrary rights. Afterwards every capability
+//! to an object that already existed carries no more rights than some
+//! capability to that object carried before.
+//!
+//! Only this harness is kept. The same check over delegate, delete,
+//! revoke, create and kill either exceeded 12 GB in CBMC or tripped
+//! modelling artifacts ("unreachable code" on safe `Option` matches that
+//! an exhaustive host replay never reaches). Those operations are covered
+//! by the syscall storm's global invariants (tests/storm.rs) and the
+//! capability-tree model test (tests/captree_model.rs) instead.
+
+use super::platform::KaniPlatform;
+use crate::Kernel;
+use domain::{capability::MAX_CAPS_PER_PROCESS, process::MAX_PROCESSES, resource::Resource};
+use types::{
+    address::PhysicalAddress,
+    badge::Badge,
+    bounded::{CapSlot, Priority},
+    id::ProcessId,
+    permission::PermissionSet,
+    time::TimeSlice,
+};
+
+#[derive(Clone, Copy, PartialEq)]
+struct Held {
+    resource: Resource,
+    perms: PermissionSet,
+    badge: Badge,
+}
+
+type Snapshot = [[Option<Held>; MAX_CAPS_PER_PROCESS]; MAX_PROCESSES];
+
+fn snapshot(k: &Kernel<KaniPlatform>) -> Snapshot {
+    let mut s = [[None; MAX_CAPS_PER_PROCESS]; MAX_PROCESSES];
+    for (p, row) in s.iter_mut().enumerate() {
+        if let Ok(process) = k.processes.get(ProcessId::from_raw(p as u16)) {
+            for (slot, cap) in process.capabilities().iter() {
+                row[slot.value() as usize] = Some(Held {
+                    resource: *cap.resource(),
+                    perms: *cap.permissions(),
+                    badge: cap.badge(),
+                });
+            }
+        }
+    }
+    s
+}
+
+/// Whether `resource` named a live object before the operation.
+fn existed(before: &Snapshot, resource: &Resource) -> bool {
+    before
+        .iter()
+        .flatten()
+        .flatten()
+        .any(|h| h.resource == *resource)
+}
+
+/// Some capability before the operation already granted at least `h`.
+fn justified(before: &Snapshot, h: &Held) -> bool {
+    before.iter().flatten().flatten().any(|b| {
+        b.resource == h.resource
+            && h.perms.is_subset_of(&b.perms)
+            && (b.badge == h.badge || b.badge.is_none())
+    })
+}
+
+fn any_perms() -> PermissionSet {
+    PermissionSet::from_bits(kani::any::<u8>() & 0b1111)
+}
+
+fn any_slot() -> CapSlot {
+    CapSlot::new(kani::any::<u8>() % (CapSlot::MAX + 1)).unwrap()
+}
+
+/// Init and one more process, an endpoint, a notification, and caps with
+/// arbitrary rights spread over both, including a cap to the other process.
+fn small_world() -> Kernel<KaniPlatform> {
+    let mut k = Kernel::new(KaniPlatform, PhysicalAddress::from_raw(0x8400_0000), 6);
+    let (init, _) = k.boot(Priority::DEFAULT, TimeSlice::DEFAULT).unwrap();
+    let b = k.create_process_internal().unwrap();
+    k.spawn_thread_internal(b).unwrap();
+    let ep = k.create_endpoint(init).unwrap();
+    let n = k.create_notification(b).unwrap();
+    k.grant_capability(init, Resource::Endpoint(ep), any_perms())
+        .unwrap();
+    k.grant_capability(init, Resource::Process(b), any_perms())
+        .unwrap();
+    k.grant_capability(b, Resource::Endpoint(ep), any_perms())
+        .unwrap();
+    k.grant_capability(b, Resource::Notification(n), any_perms())
+        .unwrap();
+    k
+}
+
+/// The caller is concrete: a symbolic pid turns every table lookup into a
+/// symbolic index and blows CBMC's formula up past 30 GB.
+#[kani::proof]
+#[kani::unwind(8)]
+fn mint_creates_no_authority() {
+    let mut k = small_world();
+    let (slot, badge, perms) = (any_slot(), Badge::new(kani::any()), any_perms());
+    let before = snapshot(&k);
+    let _ = k.mint(ProcessId::from_raw(0), slot, badge, perms);
+    let after = snapshot(&k);
+    for (p, row) in after.iter().enumerate() {
+        for (s, held) in row.iter().enumerate() {
+            let Some(h) = held else { continue };
+            if before[p][s] == Some(*h) {
+                continue; // untouched
+            }
+            if existed(&before, &h.resource) {
+                assert!(justified(&before, h), "authority appeared from nowhere");
+            }
+        }
+    }
+}

crates/kernel/src/proofs/delegation.rs

@@ -1,6 +1,6 @@
+use super::{arbitrary_endpoint_cap, insert_cap};
 use domain::capability::{Capability, CapabilityTable};
 use domain::resource::Resource;
-use super::{arbitrary_endpoint_cap, insert_cap};
 use types::generation::Generation;
 use types::id::EndpointId;
 use types::permission::{Permission, PermissionSet};
@@ -16,17 +16,16 @@ fn kernel_delegate_path_never_escalates() {
     kani::assume(source_perms.allows(Permission::Delegate));
 
     let mut source_table = CapabilityTable::new();
-    let slot = insert_cap(&mut source_table, arbitrary_endpoint_cap(source_bits, ep_id));
+    let slot = insert_cap(
+        &mut source_table,
+        arbitrary_endpoint_cap(source_bits, ep_id),
+    );
 
     let cap = source_table.get(slot).unwrap();
     let original_perms = *cap.permissions();
     let restricted = original_perms.restrict_to(&PermissionSet::from_bits(restrict_bits));
 
-    let delegated = Capability::new(
-        cap.resource().clone(),
-        restricted,
-        Generation::initial(),
-    );
+    let delegated = Capability::new(*cap.resource(), restricted, Generation::initial());
 
     let mut target_table = CapabilityTable::new();
     let target_slot = insert_cap(&mut target_table, delegated);
@@ -34,11 +33,18 @@ fn kernel_delegate_path_never_escalates() {
     let result = target_table.get(target_slot).unwrap();
     assert!(result.permissions().is_subset_of(&original_perms));
 
-    if !original_perms.allows(Permission::Read) { assert!(!result.permissions().allows(Permission::Read)); }
-    if !original_perms.allows(Permission::Write) { assert!(!result.permissions().allows(Permission::Write)); }
-    if !original_perms.allows(Permission::Execute) { assert!(!result.permissions().allows(Permission::Execute)); }
-    if !original_perms.allows(Permission::Delegate) { assert!(!result.permissions().allows(Permission::Delegate)); }
-    if !original_perms.allows(Permission::Revoke) { assert!(!result.permissions().allows(Permission::Revoke)); }
+    if !original_perms.allows(Permission::Read) {
+        assert!(!result.permissions().allows(Permission::Read));
+    }
+    if !original_perms.allows(Permission::Write) {
+        assert!(!result.permissions().allows(Permission::Write));
+    }
+    if !original_perms.allows(Permission::Execute) {
+        assert!(!result.permissions().allows(Permission::Execute));
+    }
+    if !original_perms.allows(Permission::Delegate) {
+        assert!(!result.permissions().allows(Permission::Delegate));
+    }
 }
 
 #[kani::proof]
@@ -58,15 +64,19 @@ fn kernel_chained_delegate_never_escalates() {
     let slot_a = insert_cap(&mut table_a, arbitrary_endpoint_cap(original_bits, ep_id));
 
     let cap = table_a.get(slot_a).unwrap();
-    let perms_for_b = cap.permissions().restrict_to(&PermissionSet::from_bits(restrict1_bits));
+    let perms_for_b = cap
+        .permissions()
+        .restrict_to(&PermissionSet::from_bits(restrict1_bits));
 
     let mut table_b = CapabilityTable::new();
-    let cap_b = Capability::new(resource.clone(), perms_for_b, Generation::initial());
+    let cap_b = Capability::new(resource, perms_for_b, Generation::initial());
     let slot_b = insert_cap(&mut table_b, cap_b);
 
     let cap_in_b = table_b.get(slot_b).unwrap();
     if cap_in_b.permissions().allows(Permission::Delegate) {
-        let perms_for_c = cap_in_b.permissions().restrict_to(&PermissionSet::from_bits(restrict2_bits));
+        let perms_for_c = cap_in_b
+            .permissions()
+            .restrict_to(&PermissionSet::from_bits(restrict2_bits));
 
         let mut table_c = CapabilityTable::new();
         let cap_c = Capability::new(resource, perms_for_c, Generation::initial());

crates/kernel/src/proofs/mediation.rs

@@ -1,5 +1,5 @@
-use domain::capability::CapabilityTable;
 use super::{arbitrary_endpoint_cap, insert_cap};
+use domain::capability::CapabilityTable;
 use types::bounded::CapSlot;
 use types::permission::{Permission, PermissionSet};
 
@@ -38,7 +38,7 @@ fn handle_receive_rejects_without_read_permission() {
 #[kani::proof]
 fn missing_cap_always_rejected() {
     let slot_val: u8 = kani::any();
-    kani::assume(slot_val <= 63);
+    kani::assume(slot_val <= CapSlot::MAX);
     let slot = CapSlot::new(slot_val).unwrap();
 
     let table = CapabilityTable::new();
@@ -60,7 +60,10 @@ fn check_cap_faithfully_reflects_stored_permissions() {
 
     assert!(retrieved.permissions().allows(Permission::Read) == perms.allows(Permission::Read));
     assert!(retrieved.permissions().allows(Permission::Write) == perms.allows(Permission::Write));
-    assert!(retrieved.permissions().allows(Permission::Execute) == perms.allows(Permission::Execute));
-    assert!(retrieved.permissions().allows(Permission::Delegate) == perms.allows(Permission::Delegate));
-    assert!(retrieved.permissions().allows(Permission::Revoke) == perms.allows(Permission::Revoke));
+    assert!(
+        retrieved.permissions().allows(Permission::Execute) == perms.allows(Permission::Execute)
+    );
+    assert!(
+        retrieved.permissions().allows(Permission::Delegate) == perms.allows(Permission::Delegate)
+    );
 }

crates/kernel/src/proofs/mod.rs

@@ -1,6 +1,9 @@
+mod abi;
+mod authority;
 mod delegation;
 mod mediation;
 mod message;
+mod platform;
 mod revocation;
 
 use domain::capability::{Capability, CapabilityTable};

crates/kernel/src/proofs/platform.rs

@@ -0,0 +1,62 @@
+//! A platform with no hardware behind it, for running the real kernel
+//! under Kani. Page tables cost one frame per address space.
+
+use platform::{FrameSource, MapError, Platform};
+use types::{
+    address::{EntryPoint, PhysicalAddress, StackPointer, VirtualAddress},
+    id::{CoreId, IrqId, ProcessId},
+    mapping::PagePerms,
+    time::{Ticks, TimerDuration},
+};
+
+pub struct KaniPlatform;
+
+impl Platform for KaniPlatform {
+    const USER_VA_START: usize = 0x1000;
+    const USER_VA_END: usize = 0x0200_0000;
+
+    fn create_address_space(
+        &mut self,
+        _process: ProcessId,
+        frames: &mut dyn FrameSource,
+    ) -> Result<(), MapError> {
+        frames.alloc_table_frame().ok_or(MapError::OutOfFrames)?;
+        Ok(())
+    }
+    fn destroy_address_space(&mut self, _process: ProcessId) {}
+    fn map_page(
+        &mut self,
+        _process: ProcessId,
+        _va: VirtualAddress,
+        _pa: PhysicalAddress,
+        _perms: PagePerms,
+        _frames: &mut dyn FrameSource,
+    ) -> Result<(), MapError> {
+        Ok(())
+    }
+    fn unmap_page(&mut self, _process: ProcessId, _va: VirtualAddress) {}
+    fn zero_frame(&mut self, _pa: PhysicalAddress) {}
+    fn enable_user_mode(&mut self, _entry: EntryPoint, _stack: StackPointer) -> ! {
+        kani::assume(false);
+        loop {}
+    }
+    fn set_timer(&mut self, _duration: TimerDuration) {}
+    fn current_ticks(&self) -> Ticks {
+        Ticks::from_raw(0)
+    }
+    fn mask_irq(&mut self, _irq: IrqId) {}
+    fn unmask_irq(&mut self, _irq: IrqId) {}
+    fn send_ipi(&mut self, _target: CoreId) {}
+    fn core_id(&self) -> CoreId {
+        CoreId::from_raw(0)
+    }
+    fn num_cores(&self) -> u8 {
+        1
+    }
+    fn halt(&self) -> ! {
+        // Halting ends the run; there is no state after it to check.
+        kani::assume(false);
+        loop {}
+    }
+    fn debug_putchar(&self, _byte: u8) {}
+}

crates/kernel/src/proofs/revocation.rs

@@ -1,7 +1,6 @@
-use domain::capability::{Capability, CapabilityTable};
-use domain::endpoint::Endpoint;
-use domain::resource::Resource;
 use super::{arbitrary_endpoint_cap, insert_cap};
+use domain::capability::{Capability, CapabilityTable};
+use domain::resource::Resource;
 use types::generation::Generation;
 use types::id::EndpointId;
 use types::permission::{Permission, PermissionSet};
@@ -62,77 +61,3 @@ fn grant_cap_preserves_resource_identity() {
         _ => panic!("resource type changed"),
     }
 }
-
-#[kani::proof]
-fn generation_revocation_invalidates_all_caps() {
-    let bits: u8 = kani::any();
-    let ep_id: u16 = kani::any();
-    kani::assume(ep_id < 256);
-
-    let mut endpoint = Endpoint::new(EndpointId::from_raw(ep_id));
-    let original_gen = *endpoint.generation();
-
-    let cap = Capability::new(
-        Resource::Endpoint(EndpointId::from_raw(ep_id)),
-        PermissionSet::from_bits(bits),
-        original_gen,
-    );
-
-    let mut table = CapabilityTable::new();
-    let slot = insert_cap(&mut table, cap);
-
-    assert!(table.get(slot).unwrap().generation().is_valid_against(&original_gen));
-
-    endpoint.revoke();
-    let new_gen = *endpoint.generation();
-
-    assert!(!table.get(slot).unwrap().generation().is_valid_against(&new_gen));
-}
-
-#[kani::proof]
-fn cap_created_after_revoke_is_valid() {
-    let ep_id: u16 = kani::any();
-    kani::assume(ep_id < 256);
-    let bits: u8 = kani::any();
-
-    let mut endpoint = Endpoint::new(EndpointId::from_raw(ep_id));
-    endpoint.revoke();
-    let current_gen = *endpoint.generation();
-
-    let cap = Capability::new(
-        Resource::Endpoint(EndpointId::from_raw(ep_id)),
-        PermissionSet::from_bits(bits),
-        current_gen,
-    );
-
-    assert!(cap.generation().is_valid_against(&current_gen));
-}
-
-#[kani::proof]
-fn multiple_revocations_invalidate_all_prior_caps() {
-    let ep_id: u16 = kani::any();
-    kani::assume(ep_id < 256);
-
-    let mut endpoint = Endpoint::new(EndpointId::from_raw(ep_id));
-
-    let gen0 = *endpoint.generation();
-    let cap0 = Capability::new(
-        Resource::Endpoint(EndpointId::from_raw(ep_id)),
-        PermissionSet::empty().with(Permission::Read),
-        gen0,
-    );
-
-    endpoint.revoke();
-    let gen1 = *endpoint.generation();
-    let cap1 = Capability::new(
-        Resource::Endpoint(EndpointId::from_raw(ep_id)),
-        PermissionSet::empty().with(Permission::Read),
-        gen1,
-    );
-
-    endpoint.revoke();
-    let gen2 = *endpoint.generation();
-
-    assert!(!cap0.generation().is_valid_against(&gen2));
-    assert!(!cap1.generation().is_valid_against(&gen2));
-}

crates/kernel/src/smp.rs

@@ -0,0 +1,119 @@
+//! Cores. Every thread has a home core, chosen when it is created, and
+//! only ever runs there: it waits in that core's run queue and is never
+//! migrated. Making a thread ready from another core sends that core an
+//! IPI when it has to look at its queue again (it is idle, or the thread
+//! outranks what it is running), and so does taking away the thread a
+//! core is running.
+
+use domain::{
+    scheduler::{Scheduler, SchedulerDecision},
+    thread::ThreadState,
+};
+use platform::Platform;
+use types::{
+    bounded::Priority,
+    id::{CoreId, ThreadId},
+};
+
+use crate::Kernel;
+
+impl<P: Platform> Kernel<P> {
+    /// The core `tid` runs on.
+    pub fn home(&self, tid: ThreadId) -> CoreId {
+        self.homes
+            .get(tid.raw() as usize)
+            .copied()
+            .unwrap_or(CoreId::from_raw(0))
+    }
+
+    /// Homes a new thread on `core`.
+    pub(crate) fn set_home(&mut self, tid: ThreadId, core: CoreId) {
+        if let Some(h) = self.homes.get_mut(tid.raw() as usize) {
+            *h = core;
+        }
+    }
+
+    /// Homes a new thread on the core with the fewest live threads.
+    pub(crate) fn place(&mut self, tid: ThreadId) {
+        let cores = self.scheduler.num_cores().max(1);
+        let load = |core: CoreId| {
+            self.threads
+                .iter()
+                .filter(|(t, _)| *t != tid && self.home(*t) == core)
+                .count()
+        };
+        let best = (0..cores)
+            .map(CoreId::from_raw)
+            .min_by_key(|c| load(*c))
+            .unwrap_or(CoreId::from_raw(0));
+        self.set_home(tid, best);
+    }
+
+    /// Queues a ready thread on its home core, and kicks that core if it
+    /// is another one that should look at its queue now.
+    pub(crate) fn make_ready(&mut self, tid: ThreadId, priority: Priority) {
+        let home = self.home(tid);
+        self.scheduler.add(tid, priority, home);
+        if home == self.platform.core_id() {
+            return;
+        }
+        let outranks = match self.scheduler.current(home) {
+            None => true,
+            Some(running) => self
+                .threads
+                .get(running)
+                .is_ok_and(|t| priority > t.priority()),
+        };
+        if outranks {
+            self.platform.send_ipi(home);
+        }
+    }
+
+    /// Before `tid` is destroyed: if another core is running it, that core
+    /// must stop and pick something else.
+    pub(crate) fn evict(&mut self, tid: ThreadId) {
+        if let Ok(ThreadState::Running(core)) = self.threads.get(tid).map(|t| *t.state())
+            && core != self.platform.core_id()
+        {
+            self.platform.send_ipi(core);
+        }
+    }
+
+    /// What `core` should do after an IPI: keep running its thread, or
+    /// switch to a higher-priority one now waiting. When it has no thread
+    /// (it was idle, or its thread was destroyed) the caller picks the
+    /// next one itself.
+    pub fn reschedule(&mut self, core: CoreId) -> SchedulerDecision {
+        let Some(current) = self.scheduler.current(core) else {
+            return SchedulerDecision::Continue;
+        };
+        let Ok(thread) = self.threads.get(current) else {
+            return SchedulerDecision::Continue;
+        };
+        let priority = thread.priority();
+        if self
+            .scheduler
+            .highest_waiting(core)
+            .is_none_or(|p| p <= priority)
+        {
+            return SchedulerDecision::Continue;
+        }
+        let Some(next) = self.scheduler.next(core) else {
+            return SchedulerDecision::Continue;
+        };
+        if self
+            .threads
+            .get_mut(next)
+            .and_then(|t| t.set_running(core))
+            .is_err()
+        {
+            return SchedulerDecision::Continue;
+        }
+        if let Ok(t) = self.threads.get_mut(current)
+            && t.preempt().is_ok()
+        {
+            self.scheduler.add(current, priority, core);
+        }
+        SchedulerDecision::Preempt(next)
+    }
+}

crates/kernel/src/syscall/capability.rs

@@ -11,17 +11,18 @@ impl<P: Platform> Kernel<P> {
         to_endpoint: types::bounded::CapSlot,
         restrict: types::permission::PermissionSet,
     ) -> SyscallOutcome {
-        let (resource, permissions) = match self.check_cap(
-            caller_pid,
-            slot,
-            types::permission::Permission::Delegate,
-        ) {
-            Ok(cap) => (cap.resource().clone(), *cap.permissions()),
+        // A copy of the capability itself, so its badge and generation
+        // travel with it; only the permissions narrow.
+        let copy = match self.check_cap(caller_pid, slot, types::permission::Permission::Delegate) {
+            Ok(cap) => domain::capability::Capability::new(
+                *cap.resource(),
+                cap.permissions().restrict_to(&restrict),
+                *cap.generation(),
+            )
+            .with_badge(cap.badge()),
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
 
-        let restricted = permissions.restrict_to(&restrict);
-
         let target_pid = match self.check_cap(
             caller_pid,
             to_endpoint,
@@ -29,31 +30,24 @@ impl<P: Platform> Kernel<P> {
         ) {
             Ok(cap) => match cap.resource() {
                 domain::resource::Resource::Process(pid) => *pid,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
+                _ => {
+                    return SyscallOutcome::Complete(SyscallResult::Error(
                         domain::error::KernelError::PermissionDenied {
                             slot: to_endpoint,
                             needed: types::permission::Permission::Execute,
                         },
-                )),
+                    ));
+                }
             },
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
 
-        if let Err(e) = self.grant_cap(target_pid, resource.clone(), restricted) {
+        let parent = self.cap_ref(caller_pid, slot);
+        let inserted = self.insert_derived(target_pid, copy, parent);
+        if let Err(e) = inserted {
             return SyscallOutcome::Complete(SyscallResult::Error(e));
         }
 
-        if let domain::resource::Resource::Memory(region_id) = &resource {
-            if let Some(region) = self.regions.get(*region_id) {
-                self.platform.map_shared(
-                    target_pid,
-                    region.base(),
-                    region.size(),
-                    restricted,
-                );
-            }
-        }
-
         SyscallOutcome::Complete(SyscallResult::Ok)
     }
 
@@ -62,16 +56,20 @@ impl<P: Platform> Kernel<P> {
         caller_pid: types::id::ProcessId,
         slot: types::bounded::CapSlot,
     ) -> SyscallOutcome {
-        let resource = match self.check_cap(
-            caller_pid,
-            slot,
-            types::permission::Permission::Revoke,
-        ) {
-            Ok(cap) => cap.resource().clone(),
-            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-        };
+        SyscallOutcome::Complete(match self.revoke_subtree(caller_pid, slot) {
+            Ok(()) => SyscallResult::Ok,
+            Err(e) => SyscallResult::Error(e),
+        })
+    }
 
-        self.revoke_resource(&resource);
-        SyscallOutcome::Complete(SyscallResult::Ok)
+    pub(crate) fn handle_drop_cap(
+        &mut self,
+        caller_pid: types::id::ProcessId,
+        slot: types::bounded::CapSlot,
+    ) -> SyscallOutcome {
+        SyscallOutcome::Complete(match self.delete_cap(caller_pid, slot) {
+            Ok(()) => SyscallResult::Ok,
+            Err(e) => SyscallResult::Error(e),
+        })
     }
 }

crates/kernel/src/syscall/fault.rs

@@ -1,50 +1,42 @@
+use domain::{fault::Fault, message::Message};
 use platform::Platform;
+use types::{id::ThreadId, permission::Permission};
 
+use super::{Delivery, DeliveryKind, SyscallResult};
 use crate::Kernel;
 
 impl<P: Platform> Kernel<P> {
-    pub fn handle_fault(
-        &mut self,
-        tid: types::id::ThreadId,
-        fault: domain::fault::Fault,
-        fault_pc: usize,
-    ) {
-        let pid = match self.threads.get(tid) {
-            Ok(t) => t.process(),
-            Err(_) => return,
+    /// A thread faulted. Report it to the process's fault endpoint (if one
+    /// is set, valid and has a receiver waiting), then destroy the process.
+    pub fn handle_fault(&mut self, tid: ThreadId, fault: Fault, fault_pc: usize) {
+        let Some(pid) = self.thread_process(tid) else {
+            return;
         };
-
-        // Try to deliver fault to a fault handler endpoint (if configured)
-        if let Ok(process) = self.processes.get(pid) {
-            if let Some(handler_slot) = process.fault_handler() {
-                if let Ok(cap) = process.capabilities().get(handler_slot) {
-                    if let domain::resource::Resource::Endpoint(ep_id) = cap.resource() {
-                        let msg = domain::message::Message::from_words([
-                            pid.raw() as usize,
-                            fault.code(),
-                            fault.address(),
-                            fault_pc,
-                        ]);
-
-                        if let Some(ep) = self.endpoints.get_mut(*ep_id) {
-                            if ep.has_waiting_receiver() {
-                                if let Some(receiver_tid) = ep.dequeue_receiver() {
-                                    self.pending_results[receiver_tid.raw() as usize] =
-                                        Some(crate::SyscallResult::Message(msg));
-
-                                    if let Ok(receiver) = self.threads.get_mut(receiver_tid) {
-                                        let priority = receiver.priority();
-                                        let _ = receiver.unblock();
-                                        let core = self.platform.core_id();
-                                        use domain::scheduler::Scheduler;
-                                        self.scheduler.add(receiver_tid, priority, core);
-                                    }
-                                }
-                            }
-                        }
-                    }
-                }
-            }
+        let handler = self
+            .processes
+            .get(pid)
+            .ok()
+            .and_then(|p| p.fault_handler())
+            .and_then(|slot| self.check_cap(pid, slot, Permission::Execute).ok())
+            .and_then(|cap| match cap.resource() {
+                domain::resource::Resource::Endpoint(ep) => Some((*ep, cap.badge())),
+                _ => None,
+            });
+        if let Some((ep, badge)) = handler
+            && let Some(receiver) = self
+                .endpoints
+                .get_mut(ep)
+                .and_then(|e| e.dequeue_receiver())
+        {
+            let report =
+                Message::from_words([pid.raw() as usize, fault.code(), fault.address(), fault_pc]);
+            let delivery = Delivery {
+                kind: DeliveryKind::Message,
+                badge: badge.raw(),
+                words: *report.words(),
+                cap: None,
+            };
+            self.wake(receiver, SyscallResult::Received(delivery));
         }
 
         self.destroy_process(pid);

crates/kernel/src/syscall/ipc.rs

@@ -1,336 +1,569 @@
-use platform::Platform;
+//! Endpoint IPC, notifications and interrupt delivery. docs/ipc.md is the
+//! specification; the comments below only point at the non-obvious rules.
 
-use super::{SyscallOutcome, SyscallResult};
+use domain::{
+    capability::Capability,
+    error::KernelError,
+    message::Message,
+    notification::SignalEffect,
+    resource::Resource,
+    scheduler::Scheduler,
+    thread::{BlockReason, ThreadState},
+};
+use platform::Platform;
+use types::{
+    badge::Badge,
+    bounded::CapSlot,
+    generation::Generation,
+    id::{EndpointId, IrqId, NotificationId, ProcessId, ThreadId},
+    permission::{Permission, PermissionSet},
+};
+
+use super::{Delivery, DeliveryKind, SyscallOutcome, SyscallResult};
 use crate::Kernel;
 
+/// A thread named by id and generation, so a stale reference can be told
+/// apart from a new thread that reused the id.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ThreadRef {
+    pub tid: ThreadId,
+    pub generation: Generation,
+}
+
+/// A message a blocked sender is waiting to hand over.
+#[derive(Debug, Clone, Copy)]
+pub(crate) struct Outgoing {
+    message: Message,
+    badge: Badge,
+    /// The sender's endpoint cap had `Delegate`, so a capability may travel.
+    grant: bool,
+}
+
+/// Per-thread IPC bookkeeping.
+#[derive(Debug, Clone, Copy, Default)]
+pub struct IpcState {
+    pub(crate) outgoing: Option<Outgoing>,
+    /// The caller this thread owes a reply to.
+    pub(crate) reply_to: Option<ThreadRef>,
+    pub(crate) bound: Option<NotificationId>,
+}
+
+fn rw_delegate() -> PermissionSet {
+    PermissionSet::empty()
+        .with(Permission::Read)
+        .with(Permission::Write)
+        .with(Permission::Delegate)
+}
+
 impl<P: Platform> Kernel<P> {
-    pub(crate) fn handle_create_endpoint(
+    pub(crate) fn ipc(&self, tid: ThreadId) -> Option<&IpcState> {
+        self.ipc.get(tid.raw() as usize)
+    }
+
+    pub(crate) fn ipc_mut(&mut self, tid: ThreadId) -> Option<&mut IpcState> {
+        self.ipc.get_mut(tid.raw() as usize)
+    }
+
+    pub(crate) fn set_pending_result(&mut self, tid: ThreadId, result: Option<SyscallResult>) {
+        if let Some(r) = self.pending_results.get_mut(tid.raw() as usize) {
+            *r = result;
+        }
+    }
+
+    fn thread_ref(&self, tid: ThreadId) -> Option<ThreadRef> {
+        Some(ThreadRef {
+            tid,
+            generation: self.threads.generation(tid)?,
+        })
+    }
+
+    fn is_live(&self, r: ThreadRef) -> bool {
+        self.threads.generation(r.tid) == Some(r.generation)
+    }
+
+    fn is_blocked_as(&self, tid: ThreadId, f: impl Fn(&BlockReason) -> bool) -> bool {
+        matches!(self.threads.get(tid).map(|t| *t.state()), Ok(ThreadState::Blocked(r)) if f(&r))
+    }
+
+    /// Blocks the running caller.
+    pub(crate) fn block_caller(&mut self, tid: ThreadId, reason: BlockReason) -> SyscallOutcome {
+        if let Ok(t) = self.threads.get_mut(tid) {
+            let _ = t.block(reason);
+        }
+        self.scheduler.remove(tid);
+        SyscallOutcome::BlockCaller(reason)
+    }
+
+    /// Makes a blocked thread runnable with `result` as its syscall result.
+    pub(crate) fn wake(&mut self, tid: ThreadId, result: SyscallResult) {
+        let Ok(thread) = self.threads.get_mut(tid) else {
+            return;
+        };
+        let priority = thread.priority();
+        if thread.unblock().is_ok() {
+            self.set_pending_result(tid, Some(result));
+            self.make_ready(tid, priority);
+        }
+    }
+
+    /// Releases a caller waiting on `reply` with `NoReply`, if it is still
+    /// that caller and still waiting.
+    pub(crate) fn release_caller(&mut self, reply: ThreadRef) {
+        if self.is_live(reply)
+            && self.is_blocked_as(reply.tid, |r| *r == BlockReason::AwaitingReply)
+        {
+            self.wake(reply.tid, SyscallResult::Error(KernelError::NoReply));
+        }
+    }
+
+    fn endpoint_cap(
+        &self,
+        pid: ProcessId,
+        slot: CapSlot,
+        needed: Permission,
+    ) -> Result<(EndpointId, Badge, bool), KernelError> {
+        let cap = self.check_cap(pid, slot, needed)?;
+        match cap.resource() {
+            Resource::Endpoint(id) => Ok((
+                *id,
+                cap.badge(),
+                cap.permissions().allows(Permission::Delegate),
+            )),
+            _ => Err(KernelError::WrongObject),
+        }
+    }
+
+    fn notification_cap(
+        &self,
+        pid: ProcessId,
+        slot: CapSlot,
+        needed: Permission,
+    ) -> Result<(NotificationId, Badge, Generation), KernelError> {
+        let cap = self.check_cap(pid, slot, needed)?;
+        match cap.resource() {
+            Resource::Notification(id) => Ok((*id, cap.badge(), *cap.generation())),
+            _ => Err(KernelError::WrongObject),
+        }
+    }
+
+    /// Copies the capability in `slot` of `from` into `to`'s table, if the
+    /// transfer is allowed and still valid. Returns where it landed.
+    fn transfer_cap(
         &mut self,
-        caller_pid: types::id::ProcessId,
+        from: ProcessId,
+        slot: Option<CapSlot>,
+        grant: bool,
+        to: ProcessId,
+    ) -> Option<CapSlot> {
+        let slot = slot?;
+        if !grant {
+            return None;
+        }
+        let copy: Capability = self
+            .check_cap(from, slot, Permission::Delegate)
+            .ok()?
+            .clone();
+        let parent = self.cap_ref(from, slot);
+        self.insert_derived(to, copy, parent).ok()
+    }
+
+    /// Hands `out` from `sender` to `receiver`. For a call, the receiver's
+    /// reply slot now names the sender.
+    fn deliver(
+        &mut self,
+        sender: ThreadId,
+        out: Outgoing,
+        receiver: ThreadId,
+        kind: DeliveryKind,
+    ) -> Delivery {
+        let from = self.thread_process(sender);
+        let to = self.thread_process(receiver);
+        let cap = match (from, to) {
+            (Some(from), Some(to)) => self.transfer_cap(from, out.message.cap(), out.grant, to),
+            _ => None,
+        };
+        if kind == DeliveryKind::Call {
+            let caller = self.thread_ref(sender);
+            if let Some(s) = self.ipc_mut(receiver) {
+                s.reply_to = caller;
+            }
+        }
+        Delivery {
+            kind,
+            badge: out.badge.raw(),
+            words: *out.message.words(),
+            cap,
+        }
+    }
+
+    // ---- endpoints ----
+
+    pub(crate) fn send(
+        &mut self,
+        tid: ThreadId,
+        pid: ProcessId,
+        slot: CapSlot,
+        message: Message,
+        is_call: bool,
     ) -> SyscallOutcome {
-        let ep_id = match self.create_endpoint() {
+        let (ep, badge, grant) = match self.endpoint_cap(pid, slot, Permission::Execute) {
+            Ok(v) => v,
+            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
+        };
+        let out = Outgoing {
+            message,
+            badge,
+            grant,
+        };
+        let kind = if is_call {
+            DeliveryKind::Call
+        } else {
+            DeliveryKind::Message
+        };
+
+        let receiver = self
+            .endpoints
+            .get_mut(ep)
+            .and_then(|e| e.dequeue_receiver());
+        if let Some(receiver) = receiver {
+            let delivery = self.deliver(tid, out, receiver, kind);
+            self.wake(receiver, SyscallResult::Received(delivery));
+            if !is_call {
+                return SyscallOutcome::Complete(SyscallResult::Ok);
+            }
+            self.block_caller(tid, BlockReason::AwaitingReply);
+            // Run the server straight away instead of waiting for its turn.
+            // Only works if it lives on this core (run_now finds it in this
+            // core's queue only); otherwise make_ready kicked its core.
+            let core = self.platform.core_id();
+            if self.scheduler.run_now(core, receiver)
+                && self
+                    .threads
+                    .get_mut(receiver)
+                    .and_then(|t| t.set_running(core))
+                    .is_ok()
+            {
+                return SyscallOutcome::SwitchTo(receiver);
+            }
+            return SyscallOutcome::BlockCaller(BlockReason::AwaitingReply);
+        }
+
+        let queued = self
+            .endpoints
+            .get_mut(ep)
+            .is_some_and(|e| e.enqueue_sender(tid).is_some());
+        if !queued {
+            return SyscallOutcome::Complete(SyscallResult::Error(KernelError::EndpointFull));
+        }
+        if let Some(s) = self.ipc_mut(tid) {
+            s.outgoing = Some(out);
+        }
+        let reason = if is_call {
+            BlockReason::Calling(ep)
+        } else {
+            BlockReason::Sending(ep)
+        };
+        self.block_caller(tid, reason)
+    }
+
+    /// `drop_reply`: a plain `Receive` abandons any pending reply.
+    pub(crate) fn receive(
+        &mut self,
+        tid: ThreadId,
+        pid: ProcessId,
+        slot: CapSlot,
+        drop_reply: bool,
+    ) -> SyscallOutcome {
+        let (ep, _, _) = match self.endpoint_cap(pid, slot, Permission::Read) {
+            Ok(v) => v,
+            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
+        };
+        if drop_reply && let Some(pending) = self.ipc_mut(tid).and_then(|s| s.reply_to.take()) {
+            self.release_caller(pending);
+        }
+
+        if let Some(n) = self.ipc(tid).and_then(|s| s.bound)
+            && let Some(ntfn) = self.notifications.get_mut(n)
+            && ntfn.has_bits()
+        {
+            let bits = ntfn.take_bits();
+            return SyscallOutcome::Complete(SyscallResult::Received(Delivery::signal(bits)));
+        }
+
+        let sender = self.endpoints.get_mut(ep).and_then(|e| e.dequeue_sender());
+        if let Some(sender) = sender {
+            let is_call = self.is_blocked_as(sender, |r| matches!(r, BlockReason::Calling(_)));
+            let Some(out) = self.ipc_mut(sender).and_then(|s| s.outgoing.take()) else {
+                // A queued sender always has a message; treat a missing one
+                // as a sender that vanished.
+                return SyscallOutcome::Complete(SyscallResult::Error(KernelError::WouldBlock));
+            };
+            let kind = if is_call {
+                DeliveryKind::Call
+            } else {
+                DeliveryKind::Message
+            };
+            let delivery = self.deliver(sender, out, tid, kind);
+            if is_call {
+                if let Ok(t) = self.threads.get_mut(sender) {
+                    let _ = t.rewait(BlockReason::AwaitingReply);
+                }
+            } else {
+                self.wake(sender, SyscallResult::Ok);
+            }
+            return SyscallOutcome::Complete(SyscallResult::Received(delivery));
+        }
+
+        let queued = self
+            .endpoints
+            .get_mut(ep)
+            .is_some_and(|e| e.enqueue_receiver(tid).is_some());
+        if !queued {
+            return SyscallOutcome::Complete(SyscallResult::Error(KernelError::EndpointFull));
+        }
+        self.block_caller(tid, BlockReason::Receiving(ep))
+    }
+
+    pub(crate) fn reply(
+        &mut self,
+        tid: ThreadId,
+        pid: ProcessId,
+        message: Message,
+    ) -> Result<(), KernelError> {
+        let caller = self
+            .ipc_mut(tid)
+            .and_then(|s| s.reply_to.take())
+            .ok_or(KernelError::NoReply)?;
+        let waiting = self.is_live(caller)
+            && self.is_blocked_as(caller.tid, |r| *r == BlockReason::AwaitingReply);
+        if !waiting {
+            // The caller died; the reply has nowhere to go.
+            return Ok(());
+        }
+        let to = self.thread_process(caller.tid);
+        // A reply may always carry a capability the server can delegate.
+        let cap = to.and_then(|to| self.transfer_cap(pid, message.cap(), true, to));
+        let delivery = Delivery {
+            kind: DeliveryKind::Message,
+            badge: 0,
+            words: *message.words(),
+            cap,
+        };
+        self.wake(caller.tid, SyscallResult::Received(delivery));
+        Ok(())
+    }
+
+    pub(crate) fn reply_recv(
+        &mut self,
+        tid: ThreadId,
+        pid: ProcessId,
+        slot: CapSlot,
+        message: Message,
+    ) -> SyscallOutcome {
+        if let Err(e) = self.endpoint_cap(pid, slot, Permission::Read) {
+            return SyscallOutcome::Complete(SyscallResult::Error(e));
+        }
+        if self.ipc(tid).is_some_and(|s| s.reply_to.is_some()) {
+            let _ = self.reply(tid, pid, message);
+        }
+        self.receive(tid, pid, slot, false)
+    }
+
+    pub(crate) fn mint(
+        &mut self,
+        pid: ProcessId,
+        slot: CapSlot,
+        badge: Badge,
+        permissions: PermissionSet,
+    ) -> Result<CapSlot, KernelError> {
+        let source = self.check_cap(pid, slot, Permission::Delegate)?;
+        let badgeable = matches!(
+            source.resource(),
+            Resource::Endpoint(_) | Resource::Notification(_)
+        );
+        // Any capability can be copied with narrower rights; only those a
+        // receiver can observe the badge of take one, and only once.
+        if (!badgeable && !badge.is_none()) || !source.badge().is_none() {
+            return Err(KernelError::InvalidArgument);
+        }
+        let minted = Capability::new(
+            *source.resource(),
+            source.permissions().restrict_to(&permissions),
+            *source.generation(),
+        )
+        .with_badge(badge);
+        let parent = self.cap_ref(pid, slot);
+        self.insert_derived(pid, minted, parent)
+    }
+
+    pub(crate) fn handle_create_endpoint(&mut self, pid: ProcessId) -> SyscallOutcome {
+        let id = match self.create_endpoint(pid) {
             Ok(id) => id,
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
-
-        let all_perms = types::permission::PermissionSet::empty()
-            .with(types::permission::Permission::Read)
-            .with(types::permission::Permission::Write)
-            .with(types::permission::Permission::Execute)
-            .with(types::permission::Permission::Delegate);
-
-        match self.grant_cap(
-            caller_pid,
-            domain::resource::Resource::Endpoint(ep_id),
-            all_perms,
-        ) {
+        let perms = PermissionSet::empty()
+            .with(Permission::Read)
+            .with(Permission::Execute)
+            .with(Permission::Delegate);
+        match self.grant_cap(pid, Resource::Endpoint(id), perms) {
             Ok(slot) => SyscallOutcome::Complete(SyscallResult::Slot(slot)),
             Err(e) => {
-                let _ = self.endpoints.destroy(ep_id);
+                self.endpoints.destroy(id);
                 SyscallOutcome::Complete(SyscallResult::Error(e))
             }
         }
     }
 
-    pub(crate) fn handle_send(
+    // ---- notifications ----
+
+    pub fn create_notification(&mut self, owner: ProcessId) -> Result<NotificationId, KernelError> {
+        self.processes.get(owner)?;
+        self.notifications
+            .create(owner)
+            .ok_or(KernelError::NoFreeSlot)
+    }
+
+    pub(crate) fn create_notification_cap(
         &mut self,
-        caller_tid: types::id::ThreadId,
-        caller_pid: types::id::ProcessId,
-        endpoint_slot: types::bounded::CapSlot,
-        message: domain::message::Message,
-    ) -> SyscallOutcome {
-        use domain::scheduler::Scheduler;
+        pid: ProcessId,
+    ) -> Result<CapSlot, KernelError> {
+        let id = self.create_notification(pid)?;
+        self.grant_cap(pid, Resource::Notification(id), rw_delegate())
+            .inspect_err(|_| {
+                self.notifications.destroy(id);
+            })
+    }
 
-        let ep_id = match self.check_cap(
-            caller_pid,
-            endpoint_slot,
-            types::permission::Permission::Execute,
-        ) {
-            Ok(cap) => match cap.resource() {
-                domain::resource::Resource::Endpoint(id) => *id,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::InvalidEndpoint(types::id::EndpointId::from_raw(0)),
-                )),
-            },
+    /// Signals `id` with `badge`; shared by `Signal` and interrupts.
+    fn signal_notification(&mut self, id: NotificationId, badge: Badge) {
+        let bound_receiving = self
+            .notifications
+            .get(id)
+            .and_then(|n| n.bound())
+            .is_some_and(|t| self.is_blocked_as(t, |r| matches!(r, BlockReason::Receiving(_))));
+        let Some(ntfn) = self.notifications.get_mut(id) else {
+            return;
+        };
+        match ntfn.signal(badge, bound_receiving) {
+            SignalEffect::WakeWaiter(t, bits) => {
+                self.wake(t, SyscallResult::Received(Delivery::signal(bits)));
+            }
+            SignalEffect::WakeBound(t, bits) => {
+                self.endpoints.remove_thread_from_all(t);
+                self.wake(t, SyscallResult::Received(Delivery::signal(bits)));
+            }
+            SignalEffect::Stored => {}
+        }
+    }
+
+    pub(crate) fn signal(&mut self, pid: ProcessId, slot: CapSlot) -> Result<(), KernelError> {
+        let (id, badge, _) = self.notification_cap(pid, slot, Permission::Write)?;
+        self.signal_notification(id, badge);
+        Ok(())
+    }
+
+    pub(crate) fn wait(&mut self, tid: ThreadId, pid: ProcessId, slot: CapSlot) -> SyscallOutcome {
+        let id = match self.notification_cap(pid, slot, Permission::Read) {
+            Ok((id, _, _)) => id,
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
-
-        let endpoint = match self.endpoints.get_mut(ep_id) {
-            Some(ep) => ep,
-            None => return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::InvalidEndpoint(ep_id),
-            )),
+        let Some(ntfn) = self.notifications.get_mut(id) else {
+            return SyscallOutcome::Complete(SyscallResult::Error(KernelError::NoSuchObject));
         };
+        if ntfn.has_bits() {
+            let bits = ntfn.take_bits();
+            return SyscallOutcome::Complete(SyscallResult::Received(Delivery::signal(bits)));
+        }
+        if !ntfn.add_waiter(tid) {
+            return SyscallOutcome::Complete(SyscallResult::Error(KernelError::EndpointFull));
+        }
+        self.block_caller(tid, BlockReason::WaitingNotification(id))
+    }
 
-        if endpoint.has_waiting_receiver() {
-            let receiver_tid = match endpoint.dequeue_receiver() {
-                Some(t) => t,
-                None => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::WouldBlock,
-                )),
+    pub(crate) fn poll(&mut self, pid: ProcessId, slot: CapSlot) -> Result<usize, KernelError> {
+        let (id, _, _) = self.notification_cap(pid, slot, Permission::Read)?;
+        self.notifications
+            .get_mut(id)
+            .map(|n| n.take_bits())
+            .ok_or(KernelError::NoSuchObject)
+    }
+
+    pub(crate) fn bind_notification(
+        &mut self,
+        tid: ThreadId,
+        pid: ProcessId,
+        slot: CapSlot,
+    ) -> Result<(), KernelError> {
+        let (id, _, _) = self.notification_cap(pid, slot, Permission::Read)?;
+        if self.ipc(tid).is_none_or(|s| s.bound.is_some()) {
+            return Err(KernelError::InvalidArgument);
+        }
+        let ntfn = self
+            .notifications
+            .get_mut(id)
+            .ok_or(KernelError::NoSuchObject)?;
+        if !ntfn.bind(tid) {
+            return Err(KernelError::InvalidArgument);
+        }
+        if let Some(s) = self.ipc_mut(tid) {
+            s.bound = Some(id);
+        }
+        Ok(())
+    }
+
+    // ---- interrupts ----
+
+    fn interrupt_cap(&self, pid: ProcessId, slot: CapSlot) -> Result<IrqId, KernelError> {
+        match self.check_cap(pid, slot, Permission::Execute)?.resource() {
+            Resource::Interrupt(irq) => Ok(*irq),
+            _ => Err(KernelError::WrongObject),
+        }
+    }
+
+    pub(crate) fn set_irq_notification(
+        &mut self,
+        pid: ProcessId,
+        irq_slot: CapSlot,
+        ntfn_slot: CapSlot,
+    ) -> Result<(), KernelError> {
+        let irq = self.interrupt_cap(pid, irq_slot)?;
+        let (notification, badge, generation) =
+            self.notification_cap(pid, ntfn_slot, Permission::Write)?;
+        let route = domain::irq::IrqRoute {
+            notification,
+            generation,
+            badge,
         };
-
-            self.pending_results[receiver_tid.raw() as usize] =
-                Some(SyscallResult::Message(message));
-
-            let core = self.platform.core_id();
-
-            let receiver = match self.threads.get_mut(receiver_tid) {
-                Ok(t) => t,
-                Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-            };
-            let _ = receiver.unblock();
-            let _ = receiver.set_running(core);
-
-            let caller = match self.threads.get_mut(caller_tid) {
-                Ok(t) => t,
-                Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-            };
-            let caller_priority = caller.priority();
-            let _ = caller.preempt();
-            self.scheduler.add(caller_tid, caller_priority, core);
-
-            self.scheduler.set_current(core, receiver_tid);
-
-            SyscallOutcome::SwitchTo(receiver_tid)
+        if self.irqs.set(irq, route) {
+            Ok(())
         } else {
-            self.pending_messages[caller_tid.raw() as usize] = Some(message);
-
-            let endpoint = match self.endpoints.get_mut(ep_id) {
-                Some(ep) => ep,
-                None => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::InvalidEndpoint(ep_id),
-                )),
-            };
-            if endpoint.enqueue_sender(caller_tid).is_none() {
-                self.pending_messages[caller_tid.raw() as usize] = None;
-                return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::WouldBlock,
-                ));
-            }
-
-            let caller = match self.threads.get_mut(caller_tid) {
-                Ok(t) => t,
-                Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-            };
-            let _ = caller.block(domain::thread::BlockReason::Sending(endpoint_slot));
-            self.scheduler.remove(caller_tid);
-
-            SyscallOutcome::BlockCaller(domain::thread::BlockReason::Sending(endpoint_slot))
+            Err(KernelError::InvalidIrq(irq))
         }
     }
 
-    pub(crate) fn handle_receive(
+    pub(crate) fn ack_interrupt(
         &mut self,
-        caller_tid: types::id::ThreadId,
-        caller_pid: types::id::ProcessId,
-        endpoint_slot: types::bounded::CapSlot,
-    ) -> SyscallOutcome {
-        use domain::scheduler::Scheduler;
+        pid: ProcessId,
+        slot: CapSlot,
+    ) -> Result<(), KernelError> {
+        let irq = self.interrupt_cap(pid, slot)?;
+        self.platform.unmask_irq(irq);
+        Ok(())
+    }
 
-        let ep_id = match self.check_cap(
-            caller_pid,
-            endpoint_slot,
-            types::permission::Permission::Read,
-        ) {
-            Ok(cap) => match cap.resource() {
-                domain::resource::Resource::Endpoint(id) => *id,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::InvalidEndpoint(types::id::EndpointId::from_raw(0)),
-                )),
-            },
-            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
+    /// An interrupt fired: mask the line and signal its notification. The
+    /// line stays masked until the handler acknowledges it.
+    pub fn handle_interrupt(&mut self, irq: IrqId) {
+        self.platform.mask_irq(irq);
+        let Some(route) = self.irqs.route(irq) else {
+            return;
         };
-
-        let endpoint = match self.endpoints.get_mut(ep_id) {
-            Some(ep) => ep,
-            None => return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::InvalidEndpoint(ep_id),
-            )),
-        };
-
-        if endpoint.has_waiting_sender() {
-            let sender_tid = match endpoint.dequeue_sender() {
-                Some(t) => t,
-                None => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::WouldBlock,
-                )),
-            };
-
-            let message = self.pending_messages[sender_tid.raw() as usize].take();
-            debug_assert!(message.is_some(), "sender in wait queue had no pending message");
-            let message = message.unwrap_or_else(|| domain::message::Message::empty());
-
-            self.pending_results[sender_tid.raw() as usize] = Some(SyscallResult::Ok);
-
-            let sender = match self.threads.get_mut(sender_tid) {
-                Ok(t) => t,
-                Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-            };
-            let priority = sender.priority();
-            let _ = sender.unblock();
-            let core = self.platform.core_id();
-            self.scheduler.add(sender_tid, priority, core);
-
-            SyscallOutcome::Complete(SyscallResult::Message(message))
-        } else {
-            let endpoint = match self.endpoints.get_mut(ep_id) {
-                Some(ep) => ep,
-                None => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::InvalidEndpoint(ep_id),
-                )),
-            };
-            if endpoint.enqueue_receiver(caller_tid).is_none() {
-                return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::WouldBlock,
-                ));
+        // A route set through a capability that has since been revoked, or
+        // to a notification whose slot was reused, is dead.
+        if self.notifications.generation(route.notification) != Some(route.generation) {
+            self.irqs.clear(irq);
+            return;
         }
-
-            let caller = match self.threads.get_mut(caller_tid) {
-                Ok(t) => t,
-                Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-            };
-            let _ = caller.block(domain::thread::BlockReason::Receiving(endpoint_slot));
-            self.scheduler.remove(caller_tid);
-
-            SyscallOutcome::BlockCaller(domain::thread::BlockReason::Receiving(endpoint_slot))
-        }
-    }
-
-    pub(crate) fn handle_wait_for_interrupt(
-        &mut self,
-        caller_tid: types::id::ThreadId,
-        caller_pid: types::id::ProcessId,
-        irq_slot: types::bounded::CapSlot,
-    ) -> SyscallOutcome {
-        use domain::scheduler::Scheduler;
-
-        let irq_id = match self.check_cap(
-            caller_pid,
-            irq_slot,
-            types::permission::Permission::Read,
-        ) {
-            Ok(cap) => match cap.resource() {
-                domain::resource::Resource::Interrupt(id) => *id,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::InvalidIrq(types::id::IrqId::from_raw(0)),
-                )),
-            },
-            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-        };
-
-        let _ = self.irqs.register(irq_id, caller_tid);
-
-        let caller = match self.threads.get_mut(caller_tid) {
-            Ok(t) => t,
-            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-        };
-        let _ = caller.block(domain::thread::BlockReason::WaitingForInterrupt(irq_slot));
-        self.scheduler.remove(caller_tid);
-
-        SyscallOutcome::BlockCaller(domain::thread::BlockReason::WaitingForInterrupt(irq_slot))
-    }
-
-    pub(crate) fn handle_ack_interrupt(
-        &mut self,
-        caller_pid: types::id::ProcessId,
-        irq_slot: types::bounded::CapSlot,
-    ) -> SyscallOutcome {
-        let irq_id = match self.check_cap(
-            caller_pid,
-            irq_slot,
-            types::permission::Permission::Write,
-        ) {
-            Ok(cap) => match cap.resource() {
-                domain::resource::Resource::Interrupt(id) => *id,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::InvalidIrq(types::id::IrqId::from_raw(0)),
-                )),
-            },
-            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-        };
-
-        self.platform.unmask_irq(irq_id);
-        SyscallOutcome::Complete(SyscallResult::Ok)
-    }
-
-    pub(crate) fn handle_wait_any(
-        &mut self,
-        caller_tid: types::id::ThreadId,
-        caller_pid: types::id::ProcessId,
-        sources: domain::syscall::WaitSet,
-    ) -> SyscallOutcome {
-        use domain::scheduler::Scheduler;
-
-        if sources.is_empty() {
-            return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::WouldBlock,
-            ));
-        }
-
-        for ep_slot in sources.endpoints() {
-            if let Some(slot) = ep_slot {
-                let ep_id = match self.check_cap(
-                    caller_pid,
-                    *slot,
-                    types::permission::Permission::Read,
-                ) {
-                    Ok(cap) => match cap.resource() {
-                        domain::resource::Resource::Endpoint(id) => *id,
-                        _ => continue,
-                    },
-                    Err(_) => continue,
-                };
-
-                if let Some(ep) = self.endpoints.get_mut(ep_id) {
-                    if ep.has_waiting_sender() {
-                        return SyscallOutcome::Complete(SyscallResult::WakeReason(
-                            domain::syscall::WakeReason::MessageReady(*slot),
-                        ));
-                    }
-                }
-            }
-        }
-
-        for irq_slot in sources.interrupts() {
-            if let Some(slot) = irq_slot {
-                if let Ok(cap) = self.check_cap(
-                    caller_pid,
-                    *slot,
-                    types::permission::Permission::Read,
-                ) {
-                    if let domain::resource::Resource::Interrupt(irq_id) = cap.resource() {
-                        if self.irqs.owner(*irq_id).is_some() {
-                            return SyscallOutcome::Complete(SyscallResult::WakeReason(
-                                domain::syscall::WakeReason::InterruptFired(*slot),
-                            ));
-                        }
-                    }
-                }
-            }
-        }
-
-        for ep_slot in sources.endpoints() {
-            if let Some(slot) = ep_slot {
-                if let Ok(cap) = self.check_cap(caller_pid, *slot, types::permission::Permission::Read) {
-                    if let domain::resource::Resource::Endpoint(id) = cap.resource() {
-                        if let Some(ep) = self.endpoints.get_mut(*id) {
-                            let _ = ep.enqueue_receiver(caller_tid);
-                        }
-                    }
-                }
-            }
-        }
-
-        self.wait_sets[caller_tid.raw() as usize] = Some(sources);
-
-        let caller = match self.threads.get_mut(caller_tid) {
-            Ok(t) => t,
-            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-        };
-        let _ = caller.block(domain::thread::BlockReason::WaitingAny);
-        self.scheduler.remove(caller_tid);
-
-        SyscallOutcome::BlockCaller(domain::thread::BlockReason::WaitingAny)
+        self.signal_notification(route.notification, route.badge);
     }
 }

crates/kernel/src/syscall/lifecycle.rs

@@ -1,4 +1,3 @@
-use domain::process::MAX_THREADS_PER_PROCESS;
 use platform::Platform;
 
 use super::{SyscallOutcome, SyscallResult};
@@ -11,14 +10,16 @@ impl<P: Platform> Kernel<P> {
         entry: types::address::EntryPoint,
         stack: types::address::StackPointer,
     ) -> SyscallOutcome {
-        use domain::scheduler::Scheduler;
         use domain::thread::SavedContext;
 
         let priority = types::bounded::Priority::DEFAULT;
         let time_slice = types::time::TimeSlice::DEFAULT;
         let context = SavedContext::with_entry_and_stack(entry, stack);
 
-        let tid = match self.threads.spawn_with_context(pid, priority, time_slice, None, context) {
+        let tid = match self
+            .threads
+            .spawn_with_context(pid, priority, time_slice, None, context)
+        {
             Ok(t) => t,
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
@@ -28,8 +29,8 @@ impl<P: Platform> Kernel<P> {
             return SyscallOutcome::Complete(SyscallResult::Error(e));
         }
 
-        let core = self.platform.core_id();
-        self.scheduler.add(tid, priority, core);
+        self.place(tid);
+        self.make_ready(tid, priority);
         SyscallOutcome::Complete(SyscallResult::Value(tid.raw() as usize))
     }
 
@@ -39,33 +40,42 @@ impl<P: Platform> Kernel<P> {
         create_cap: types::bounded::CapSlot,
         _image: types::address::DataRef,
     ) -> SyscallOutcome {
-        if let Err(e) = self.check_cap(caller_pid, create_cap, types::permission::Permission::Execute) {
+        if let Err(e) = self.check_cap(
+            caller_pid,
+            create_cap,
+            types::permission::Permission::Execute,
+        ) {
             return SyscallOutcome::Complete(SyscallResult::Error(e));
         }
 
-        let new_pid = match self.processes.create(
-            domain::capability::CapabilityTable::new(),
-            None,
-        ) {
+        let new_pid = match self
+            .processes
+            .create(domain::capability::CapabilityTable::new(), None)
+        {
             Ok(p) => p,
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
 
-        self.process_memory[new_pid.raw() as usize] =
-            Some(domain::memory::process_memory::ProcessMemory::new(new_pid, domain::memory::process_memory::ProcessMemory::DEFAULT_PAGE_LIMIT));
+        if let Err(e) = self.create_address_space(new_pid) {
+            let _ = self.processes.destroy(new_pid);
+            return SyscallOutcome::Complete(SyscallResult::Error(e));
+        }
 
         match self.grant_cap(
             caller_pid,
             domain::resource::Resource::Process(new_pid),
+            // The creator has full authority over what it creates,
+            // including handing that authority on.
             types::permission::PermissionSet::empty()
                 .with(types::permission::Permission::Execute)
-                .with(types::permission::Permission::Read),
+                .with(types::permission::Permission::Read)
+                .with(types::permission::Permission::Delegate),
         ) {
             Ok(slot) => SyscallOutcome::Complete(SyscallResult::Slot(slot)),
             Err(e) => {
                 // Rollback: destroy orphaned process
+                self.teardown_memory(new_pid);
                 let _ = self.processes.destroy(new_pid);
-                self.process_memory[new_pid.raw() as usize] = None;
                 SyscallOutcome::Complete(SyscallResult::Error(e))
             }
         }
@@ -78,7 +88,6 @@ impl<P: Platform> Kernel<P> {
         entry: types::address::EntryPoint,
         stack: types::address::StackPointer,
     ) -> SyscallOutcome {
-        use domain::scheduler::Scheduler;
         use domain::thread::SavedContext;
 
         let target_pid = match self.check_cap(
@@ -88,12 +97,14 @@ impl<P: Platform> Kernel<P> {
         ) {
             Ok(cap) => match cap.resource() {
                 domain::resource::Resource::Process(pid) => *pid,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
+                _ => {
+                    return SyscallOutcome::Complete(SyscallResult::Error(
                         domain::error::KernelError::PermissionDenied {
                             slot: process_cap,
                             needed: types::permission::Permission::Execute,
                         },
-                )),
+                    ));
+                }
             },
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
@@ -102,18 +113,25 @@ impl<P: Platform> Kernel<P> {
         let time_slice = types::time::TimeSlice::DEFAULT;
         let context = SavedContext::with_entry_and_stack(entry, stack);
 
-        let tid = match self.threads.spawn_with_context(target_pid, priority, time_slice, None, context) {
+        let tid = match self
+            .threads
+            .spawn_with_context(target_pid, priority, time_slice, None, context)
+        {
             Ok(t) => t,
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
 
-        if let Err(e) = self.processes.get_mut(target_pid).and_then(|p| p.add_thread(tid)) {
+        if let Err(e) = self
+            .processes
+            .get_mut(target_pid)
+            .and_then(|p| p.add_thread(tid))
+        {
             let _ = self.threads.destroy(tid);
             return SyscallOutcome::Complete(SyscallResult::Error(e));
         }
 
-        let core = self.platform.core_id();
-        self.scheduler.add(tid, priority, core);
+        self.place(tid);
+        self.make_ready(tid, priority);
         SyscallOutcome::Complete(SyscallResult::Value(tid.raw() as usize))
     }
 
@@ -122,20 +140,30 @@ impl<P: Platform> Kernel<P> {
         caller_pid: types::id::ProcessId,
         process_cap: types::bounded::CapSlot,
     ) -> SyscallOutcome {
-        let target_pid = match self.check_cap(caller_pid, process_cap, types::permission::Permission::Execute) {
+        let target_pid = match self.check_cap(
+            caller_pid,
+            process_cap,
+            types::permission::Permission::Execute,
+        ) {
             Ok(cap) => match cap.resource() {
                 domain::resource::Resource::Process(pid) => *pid,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
+                _ => {
+                    return SyscallOutcome::Complete(SyscallResult::Error(
                         domain::error::KernelError::PermissionDenied {
                             slot: process_cap,
                             needed: types::permission::Permission::Execute,
                         },
-                )),
+                    ));
+                }
             },
             Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
         };
 
         self.destroy_process(target_pid);
+        if target_pid == caller_pid {
+            // The caller no longer exists; nothing to return to.
+            return SyscallOutcome::TerminateCaller;
+        }
         SyscallOutcome::Complete(SyscallResult::Ok)
     }
 }

crates/kernel/src/syscall/memory.rs

@@ -1,156 +1,135 @@
 use platform::Platform;
-use types::address::{PhysicalAddress, VirtualAddress};
+use types::{
+    address::{PhysicalAddress, VirtualAddress},
+    bounded::CapSlot,
+    bounded::PageCount,
+    id::ProcessId,
+    mapping::PagePerms,
+};
 
 use super::{SyscallOutcome, SyscallResult};
 use crate::Kernel;
+use domain::{error::KernelError, resource::Resource};
+use types::permission::Permission;
 
-const USER_VA_LIMIT: usize = 0x80000000;
+fn complete(result: Result<SyscallResult, KernelError>) -> SyscallOutcome {
+    SyscallOutcome::Complete(result.unwrap_or_else(SyscallResult::Error))
+}
 
 impl<P: Platform> Kernel<P> {
     pub(crate) fn handle_request_pages(
         &mut self,
-        pid: types::id::ProcessId,
-        count: types::bounded::PageCount,
+        pid: ProcessId,
+        count: PageCount,
     ) -> SyscallOutcome {
         let pages = count.value() as usize;
-
-        match &mut self.process_memory[pid.raw() as usize] {
-            Some(pm) => {
-                if pm.grant(pages).is_err() {
-                    return SyscallOutcome::Complete(SyscallResult::Error(
-                        domain::error::KernelError::OutOfMemory,
-                    ));
-                }
-            }
-            None => return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::InvalidProcess(pid),
-            )),
-        }
-
-        let phys_addr = match self.page_pool.allocate(pages) {
-            Some(a) => a,
-            None => {
-                if let Some(pm) = &mut self.process_memory[pid.raw() as usize] {
-                    let _ = pm.release(pages);
-                }
-                return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::OutOfMemory,
-                ));
-            }
-        };
-
-        let user_va = match &mut self.process_memory[pid.raw() as usize] {
-            Some(pm) => {
-                let va = pm.alloc_user_va(pages);
-                pm.record_allocation(phys_addr, pages);
-                va
-            }
-            None => {
-                self.page_pool.free(phys_addr, pages);
-                return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::InvalidProcess(pid),
-                ));
-            }
-        };
-
-        for i in 0..pages {
-            let page_va = VirtualAddress::from_raw(user_va.raw() + i * 4096);
-            let page_pa = PhysicalAddress::from_raw(phys_addr.raw() + i * 4096);
-            self.platform.map_user_page(pid, page_va, page_pa, true, false);
-        }
-
-        let region = domain::memory::MemoryRegion::new(
-            types::id::RegionId::from_raw(0),
-            pid,
-            phys_addr,
-            count,
-            types::generation::Generation::initial(),
-        );
-        let _ = self.regions.insert(region);
-
-        SyscallOutcome::Complete(SyscallResult::Value(user_va.raw()))
-    }
-
-    pub(crate) fn handle_map_page(
-        &mut self,
-        caller_pid: types::id::ProcessId,
-        process_cap: types::bounded::CapSlot,
-        src_va: VirtualAddress,
-        dst_va: VirtualAddress,
-        executable: bool,
-    ) -> SyscallOutcome {
-        // Prevent mapping kernel memory into userspace
-        if src_va.raw() >= USER_VA_LIMIT {
-            return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::PermissionDenied {
-                    slot: process_cap,
-                    needed: types::permission::Permission::Read,
-                },
-            ));
-        }
-
-        let target_pid = match self.check_cap(
-            caller_pid,
-            process_cap,
-            types::permission::Permission::Execute,
-        ) {
-            Ok(cap) => match cap.resource() {
-                domain::resource::Resource::Process(pid) => *pid,
-                _ => return SyscallOutcome::Complete(SyscallResult::Error(
-                    domain::error::KernelError::PermissionDenied {
-                        slot: process_cap,
-                        needed: types::permission::Permission::Execute,
-                    },
-                )),
-            },
-            Err(e) => return SyscallOutcome::Complete(SyscallResult::Error(e)),
-        };
-
-        let pa = match self.platform.translate_va(caller_pid, src_va) {
-            Some(pa) => pa,
-            None => return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::OutOfMemory,
-            )),
-        };
-
-        self.platform.map_user_page(target_pid, dst_va, pa, !executable, executable);
-
-        SyscallOutcome::Complete(SyscallResult::Ok)
+        complete(
+            self.find_free_heap_range(pid, pages)
+                .ok_or(KernelError::OutOfMemory)
+                .and_then(|va| {
+                    self.map_fresh_range(pid, va, pages, PagePerms::ReadWrite)
+                        .map(|()| SyscallResult::Value(va.raw()))
+                }),
+        )
     }
 
     pub(crate) fn handle_release_pages(
         &mut self,
-        pid: types::id::ProcessId,
+        pid: ProcessId,
         addr: VirtualAddress,
-        count: types::bounded::PageCount,
+        count: PageCount,
     ) -> SyscallOutcome {
-        let pages = count.value() as usize;
-        let phys = match self.platform.translate_va(pid, addr) {
-            Some(pa) => pa,
-            None => return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::OutOfMemory,
-            )),
+        complete(
+            self.release_range(pid, addr, count.value() as usize)
+                .map(|()| SyscallResult::Ok),
+        )
+    }
+
+    /// Moves one of the caller's pages into the process named by
+    /// `process_cap`. Executable pages are mapped read-execute, others
+    /// read-write.
+    pub(crate) fn handle_map_page(
+        &mut self,
+        caller_pid: ProcessId,
+        process_cap: CapSlot,
+        src_va: VirtualAddress,
+        dst_va: VirtualAddress,
+        executable: bool,
+    ) -> SyscallOutcome {
+        let target = match self.check_cap(caller_pid, process_cap, Permission::Execute) {
+            Ok(cap) => match cap.resource() {
+                Resource::Process(pid) => *pid,
+                _ => {
+                    return complete(Err(KernelError::PermissionDenied {
+                        slot: process_cap,
+                        needed: Permission::Execute,
+                    }));
+                }
+            },
+            Err(e) => return complete(Err(e)),
         };
-
-        let region_id = match self.regions.find_by_base(pid, phys) {
-            Some((rid, _)) => rid,
-            None => return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::OutOfMemory,
-            )),
+        let perms = if executable {
+            PagePerms::ReadExecute
+        } else {
+            PagePerms::ReadWrite
         };
-
-        if !self.page_pool.free(phys, pages) {
-            return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::OutOfMemory,
-            ));
+        complete(
+            self.move_page(caller_pid, src_va, target, dst_va, perms)
+                .map(|()| SyscallResult::Ok),
+        )
     }
 
-        let _ = self.regions.remove(region_id);
-
-        if let Some(pm) = &mut self.process_memory[pid.raw() as usize] {
-            let _ = pm.release(pages);
+    pub(crate) fn create_region_cap(
+        &mut self,
+        pid: ProcessId,
+        pages: PageCount,
+    ) -> Result<CapSlot, KernelError> {
+        let id = self.create_pool_region(pid, pages)?;
+        let all = types::permission::PermissionSet::empty()
+            .with(Permission::Read)
+            .with(Permission::Write)
+            .with(Permission::Execute)
+            .with(Permission::Delegate);
+        self.grant_cap(pid, Resource::Memory(id), all)
     }
 
-        SyscallOutcome::Complete(SyscallResult::Ok)
+    /// Maps the region behind `slot` into the caller. The capability must
+    /// allow every access `perms` grants; the mapping lasts as long as
+    /// the capability.
+    pub(crate) fn map_region_cap(
+        &mut self,
+        pid: ProcessId,
+        slot: CapSlot,
+        va: VirtualAddress,
+        perms: PagePerms,
+    ) -> Result<(), KernelError> {
+        let cap = self.check_cap(pid, slot, Permission::Read)?;
+        let needed = match perms {
+            PagePerms::ReadOnly => Permission::Read,
+            PagePerms::ReadWrite => Permission::Write,
+            PagePerms::ReadExecute => Permission::Execute,
+        };
+        if !cap.permissions().allows(needed) {
+            return Err(KernelError::PermissionDenied { slot, needed });
+        }
+        let Resource::Memory(id) = *cap.resource() else {
+            return Err(KernelError::WrongObject);
+        };
+        let via = self.cap_ref(pid, slot);
+        self.map_region_via(id, pid, va, perms, via)
+    }
+
+    /// The physical base of the region behind `slot`. Needs Read on the
+    /// capability; pool regions are physically contiguous, so the base is
+    /// enough to program a device.
+    pub(crate) fn region_address_cap(
+        &self,
+        pid: ProcessId,
+        slot: CapSlot,
+    ) -> Result<PhysicalAddress, KernelError> {
+        let Resource::Memory(id) = *self.check_cap(pid, slot, Permission::Read)?.resource() else {
+            return Err(KernelError::WrongObject);
+        };
+        self.region_base(id).ok_or(KernelError::InvalidRegion)
     }
 }

crates/kernel/src/syscall/mod.rs

@@ -5,28 +5,66 @@ mod lifecycle;
 mod memory;
 mod simple;
 
-use domain::{error::KernelError, message::Message, syscall::Syscall};
+use domain::{error::KernelError, syscall::Syscall};
 use platform::Platform;
-use types::{bounded::CapSlot, id::ThreadId};
+use types::{bounded::CapSlot, id::ThreadId, syscall_abi::ErrorCode};
 
 use crate::Kernel;
 
+pub use ipc::{IpcState, ThreadRef};
+pub use types::syscall_abi::{Delivery, DeliveryKind};
+
 pub enum SyscallOutcome {
     Complete(SyscallResult),
     BlockCaller(domain::thread::BlockReason),
+    /// The caller blocked and `ThreadId` should run next.
     SwitchTo(ThreadId),
     TerminateCaller,
 }
 
+#[derive(Debug)]
 pub enum SyscallResult {
     Ok,
     Value(usize),
     Slot(CapSlot),
-    Message(Message),
-    WakeReason(domain::syscall::WakeReason),
+    Received(Delivery),
     Error(KernelError),
 }
 
+/// The status code userspace sees for a kernel error.
+pub fn error_code(error: &KernelError) -> ErrorCode {
+    use KernelError::*;
+    match error {
+        InvalidSlot(_) | RevokedCapability(_) | NoSuchObject | InvalidEndpoint(_) => {
+            ErrorCode::InvalidCap
+        }
+        PermissionDenied { .. } | ProcessCreateDenied | WritableAndExecutable => {
+            ErrorCode::PermissionDenied
+        }
+        WrongObject => ErrorCode::WrongObject,
+        NoFreeSlot => ErrorCode::NoFreeSlot,
+        OutOfMemory => ErrorCode::OutOfMemory,
+        InvalidAddress => ErrorCode::InvalidAddress,
+        AddressInUse => ErrorCode::AddressInUse,
+        NoReply => ErrorCode::NoReply,
+        TooManyThreadsInProcess | TooManyProcesses | TooManyThreads | EndpointFull => {
+            ErrorCode::LimitReached
+        }
+        InvalidProcess(_)
+        | InvalidThread(_)
+        | InvalidStateTransition(_)
+        | InvalidIrq(_)
+        | InvalidRegion
+        | IrqAlreadyOwned(_)
+        | WouldBlock
+        | InvalidArgument => ErrorCode::InvalidArgument,
+    }
+}
+
+fn complete(result: Result<SyscallResult, KernelError>) -> SyscallOutcome {
+    SyscallOutcome::Complete(result.unwrap_or_else(SyscallResult::Error))
+}
+
 impl<P: Platform> Kernel<P> {
     pub fn handle_syscall(&mut self, syscall: Syscall) -> SyscallOutcome {
         let (tid, pid) = match self.caller() {
@@ -43,26 +81,81 @@ impl<P: Platform> Kernel<P> {
             Syscall::RequestPages { count } => self.handle_request_pages(pid, count),
             Syscall::ReleasePages { addr, count } => self.handle_release_pages(pid, addr, count),
             Syscall::SpawnThread { entry, stack } => self.handle_spawn_thread(pid, entry, stack),
-            Syscall::CreateProcess { create_cap, image } => self.handle_create_process(pid, create_cap, image),
+            Syscall::CreateProcess { create_cap, image } => {
+                self.handle_create_process(pid, create_cap, image)
+            }
             Syscall::Kill { process } => self.handle_kill(pid, process),
             Syscall::Revoke { slot } => self.handle_revoke(pid, slot),
-            Syscall::Delegate { slot, to_endpoint, permissions } => {
-                self.handle_delegate(pid, slot, to_endpoint, permissions)
+            Syscall::DropCap { slot } => self.handle_drop_cap(pid, slot),
+            Syscall::CreateRegion { pages } => {
+                complete(self.create_region_cap(pid, pages).map(SyscallResult::Slot))
             }
-            Syscall::Send { endpoint, message } => self.handle_send(tid, pid, endpoint, message),
-            Syscall::Receive { endpoint } => self.handle_receive(tid, pid, endpoint),
-            Syscall::WaitForInterrupt { irq } => self.handle_wait_for_interrupt(tid, pid, irq),
-            Syscall::AcknowledgeInterrupt { irq } => self.handle_ack_interrupt(pid, irq),
-            Syscall::WaitAny { sources } => self.handle_wait_any(tid, pid, sources),
-            Syscall::Halt => self.handle_halt(pid),
+            Syscall::MapRegion { region, va, perms } => complete(
+                self.map_region_cap(pid, region, va, perms)
+                    .map(|()| SyscallResult::Ok),
+            ),
+            Syscall::RegionAddress { region } => complete(
+                self.region_address_cap(pid, region)
+                    .map(|pa| SyscallResult::Value(pa.raw())),
+            ),
+            Syscall::Delegate {
+                slot,
+                to_endpoint,
+                permissions,
+            } => self.handle_delegate(pid, slot, to_endpoint, permissions),
+            Syscall::Mint {
+                slot,
+                badge,
+                permissions,
+            } => complete(
+                self.mint(pid, slot, badge, permissions)
+                    .map(SyscallResult::Slot),
+            ),
+            Syscall::Send { endpoint, message } => self.send(tid, pid, endpoint, message, false),
+            Syscall::Call { endpoint, message } => self.send(tid, pid, endpoint, message, true),
+            Syscall::Receive { endpoint } => self.receive(tid, pid, endpoint, true),
+            Syscall::Reply { message } => {
+                complete(self.reply(tid, pid, message).map(|()| SyscallResult::Ok))
+            }
+            Syscall::ReplyRecv { endpoint, message } => {
+                self.reply_recv(tid, pid, endpoint, message)
+            }
+            Syscall::CreateNotification => {
+                complete(self.create_notification_cap(pid).map(SyscallResult::Slot))
+            }
+            Syscall::Signal { notification } => {
+                complete(self.signal(pid, notification).map(|()| SyscallResult::Ok))
+            }
+            Syscall::Wait { notification } => self.wait(tid, pid, notification),
+            Syscall::Poll { notification } => complete(
+                self.poll(pid, notification)
+                    .map(|bits| SyscallResult::Received(Delivery::signal(bits))),
+            ),
+            Syscall::BindNotification { notification } => complete(
+                self.bind_notification(tid, pid, notification)
+                    .map(|()| SyscallResult::Ok),
+            ),
+            Syscall::SetIrqNotification { irq, notification } => complete(
+                self.set_irq_notification(pid, irq, notification)
+                    .map(|()| SyscallResult::Ok),
+            ),
+            Syscall::AcknowledgeInterrupt { irq } => {
+                complete(self.ack_interrupt(pid, irq).map(|()| SyscallResult::Ok))
+            }
+            Syscall::Halt { control } => self.handle_halt(pid, control),
             Syscall::CreateEndpoint => self.handle_create_endpoint(pid),
             Syscall::DebugPutchar { byte } => self.handle_debug_putchar(byte),
-            Syscall::MapPage { process, src_va, dst_va, executable } => {
-                self.handle_map_page(pid, process, src_va, dst_va, executable)
-            }
-            Syscall::SpawnThreadIn { process, entry, stack } => {
-                self.handle_spawn_thread_in(pid, process, entry, stack)
-            }
+            Syscall::MapPage {
+                process,
+                src_va,
+                dst_va,
+                executable,
+            } => self.handle_map_page(pid, process, src_va, dst_va, executable),
+            Syscall::SpawnThreadIn {
+                process,
+                entry,
+                stack,
+            } => self.handle_spawn_thread_in(pid, process, entry, stack),
         }
     }
 }

crates/kernel/src/syscall/simple.rs

@@ -1,4 +1,6 @@
+use domain::{error::KernelError, resource::Resource};
 use platform::Platform;
+use types::{bounded::CapSlot, id::ProcessId, permission::Permission};
 
 use super::{SyscallOutcome, SyscallResult};
 use crate::Kernel;
@@ -31,15 +33,26 @@ impl<P: Platform> Kernel<P> {
 
         match self.scheduler.next(core) {
             Some(next) if next != caller_tid => {
-                if self.threads.get_mut(next).and_then(|t| t.set_running(core)).is_ok() {
+                if self
+                    .threads
+                    .get_mut(next)
+                    .and_then(|t| t.set_running(core))
+                    .is_ok()
+                {
                     SyscallOutcome::SwitchTo(next)
                 } else {
-                    let _ = self.threads.get_mut(caller_tid).map(|t| t.set_running(core));
+                    let _ = self
+                        .threads
+                        .get_mut(caller_tid)
+                        .map(|t| t.set_running(core));
                     SyscallOutcome::Complete(SyscallResult::Ok)
                 }
             }
             _ => {
-                let _ = self.threads.get_mut(caller_tid).map(|t| t.set_running(core));
+                let _ = self
+                    .threads
+                    .get_mut(caller_tid)
+                    .map(|t| t.set_running(core));
                 SyscallOutcome::Complete(SyscallResult::Ok)
             }
         }
@@ -59,10 +72,7 @@ impl<P: Platform> Kernel<P> {
         caller_tid: types::id::ThreadId,
         pid: types::id::ProcessId,
     ) -> SyscallOutcome {
-        use domain::scheduler::Scheduler;
-
-        self.scheduler.remove(caller_tid);
-        let _ = self.threads.destroy(caller_tid);
+        self.cleanup_threads(&[Some(caller_tid)]);
 
         if let Ok(process) = self.processes.get_mut(pid) {
             process.remove_thread(caller_tid);
@@ -79,15 +89,13 @@ impl<P: Platform> Kernel<P> {
         SyscallOutcome::Complete(SyscallResult::Ok)
     }
 
-    pub(crate) fn handle_halt(
-        &mut self,
-        pid: types::id::ProcessId,
-    ) -> SyscallOutcome {
-        if pid.raw() != 0 {
-            return SyscallOutcome::Complete(SyscallResult::Error(
-                domain::error::KernelError::ProcessCreateDenied,
-            ));
-        }
-        self.platform.halt();
+    /// Halts the machine for a holder of a SystemControl capability with
+    /// Execute; anyone else gets an error and nothing happens.
+    pub(crate) fn handle_halt(&mut self, pid: ProcessId, control: CapSlot) -> SyscallOutcome {
+        match self.check_cap(pid, control, Permission::Execute) {
+            Ok(cap) if *cap.resource() == Resource::SystemControl => self.platform.halt(),
+            Ok(_) => SyscallOutcome::Complete(SyscallResult::Error(KernelError::WrongObject)),
+            Err(e) => SyscallOutcome::Complete(SyscallResult::Error(e)),
+        }
     }
 }

crates/kernel/src/tests/abi.rs

@@ -0,0 +1,100 @@
+use crate::abi::{decode, encode, unknown_syscall};
+use crate::syscall::SyscallResult;
+use domain::syscall::Syscall;
+use types::syscall_abi::*;
+
+/// Every syscall number the ABI defines decodes with ordinary arguments,
+/// so the decoder cannot silently drop one.
+#[test]
+fn every_defined_syscall_decodes() {
+    let numbers = [
+        SYS_SEND,
+        SYS_RECEIVE,
+        SYS_DELEGATE,
+        SYS_ACKNOWLEDGE_INTERRUPT,
+        SYS_CREATE_PROCESS,
+        SYS_KILL,
+        SYS_REVOKE,
+        SYS_SPAWN_THREAD,
+        SYS_EXIT_THREAD,
+        SYS_REQUEST_PAGES,
+        SYS_RELEASE_PAGES,
+        SYS_GET_TIME,
+        SYS_GET_PROCESS_ID,
+        SYS_YIELD,
+        SYS_EXIT,
+        SYS_HALT,
+        SYS_CREATE_ENDPOINT,
+        SYS_DEBUG_PUTCHAR,
+        SYS_MAP_PAGE,
+        SYS_SPAWN_THREAD_IN,
+        SYS_DROP_CAP,
+        SYS_CALL,
+        SYS_REPLY,
+        SYS_REPLY_RECV,
+        SYS_MINT,
+        SYS_CREATE_NOTIFICATION,
+        SYS_SIGNAL,
+        SYS_WAIT,
+        SYS_POLL,
+        SYS_BIND_NOTIFICATION,
+        SYS_SET_IRQ_NOTIFICATION,
+        SYS_CREATE_REGION,
+        SYS_MAP_REGION,
+        SYS_REGION_ADDRESS,
+    ];
+    // slot 1, slot 2, small values, no cap
+    let args = [1, 2, 1, 0, 0, NONE];
+    for nr in numbers {
+        assert!(decode(nr, &args).is_some(), "syscall {nr} does not decode");
+    }
+}
+
+#[test]
+fn retired_and_unknown_numbers_do_not_decode() {
+    for nr in [3, 5, 36, 1000, usize::MAX] {
+        assert!(decode(nr, &[0; 6]).is_none(), "{nr} decoded");
+    }
+}
+
+#[test]
+fn out_of_range_arguments_do_not_decode() {
+    assert!(decode(SYS_RECEIVE, &[64, 0, 0, 0, 0, 0]).is_none());
+    assert!(
+        decode(SYS_SEND, &[1, 0, 0, 0, 0, 64]).is_none(),
+        "bad cap slot"
+    );
+    assert!(
+        decode(SYS_REQUEST_PAGES, &[0, 0, 0, 0, 0, 0]).is_none(),
+        "zero pages"
+    );
+    assert!(decode(SYS_REQUEST_PAGES, &[1025, 0, 0, 0, 0, 0]).is_none());
+    assert!(
+        decode(SYS_MAP_REGION, &[1, 0x30000, 3, 0, 0, 0]).is_none(),
+        "bad perms"
+    );
+    assert!(
+        decode(SYS_DELEGATE, &[1, 2, 256, 0, 0, 0]).is_none(),
+        "perm bits overflow u8"
+    );
+}
+
+#[test]
+fn none_means_no_capability() {
+    match decode(SYS_SEND, &[1, 9, 8, 7, 6, NONE]) {
+        Some(Syscall::Send { message, .. }) => {
+            assert_eq!(message.cap(), None);
+            assert_eq!(message.words(), &[9, 8, 7, 6]);
+        }
+        _ => panic!("send did not decode"),
+    }
+}
+
+#[test]
+fn results_follow_the_status_convention() {
+    assert_eq!(encode(&SyscallResult::Ok), [0; 8]);
+    assert_eq!(encode(&SyscallResult::Value(7))[..2], [0, 7]);
+    let err = encode(&SyscallResult::Error(domain::error::KernelError::NoReply));
+    assert_eq!(err[0], ErrorCode::NoReply as usize);
+    assert_eq!(unknown_syscall()[0], ErrorCode::UnknownSyscall as usize);
+}

crates/kernel/src/tests/board.rs

@@ -0,0 +1,323 @@
+use super::*;
+use crate::{BoardDevice, SyscallOutcome, SyscallResult};
+use domain::{error::KernelError, resource::Resource, syscall::Syscall};
+use types::{
+    address::{PhysicalAddress, VirtualAddress},
+    badge::Badge,
+    bounded::{CapSlot, PageCount, Priority},
+    id::IrqId,
+    mapping::PagePerms,
+    permission::{Permission, PermissionSet},
+    time::TimeSlice,
+};
+
+const UART: usize = 0x1000_0000;
+const VIRTIO: usize = 0x1000_1000;
+
+fn device(base: usize, pages: u16, irq: Option<u16>) -> BoardDevice {
+    BoardDevice {
+        base: PhysicalAddress::from_raw(base),
+        pages: PageCount::new(pages).unwrap(),
+        irq: irq.map(IrqId::from_raw),
+    }
+}
+
+fn board() -> [BoardDevice; 2] {
+    [device(UART, 1, Some(10)), device(VIRTIO, 1, Some(1))]
+}
+
+/// Init after boot with the board registered and its authority granted.
+fn booted() -> (Kernel<MockPlatform>, ProcessId) {
+    let (mut k, init) = kernel_with_process();
+    k.register_board(init, &board()).unwrap();
+    k.grant_boot_authority(init, &board()).unwrap();
+    (k, init)
+}
+
+fn slot_holding(k: &Kernel<MockPlatform>, pid: ProcessId, resource: Resource) -> CapSlot {
+    k.processes
+        .get(pid)
+        .unwrap()
+        .capabilities()
+        .iter()
+        .find(|(_, c)| *c.resource() == resource)
+        .map(|(s, _)| s)
+        .expect("capability present")
+}
+
+fn perms_of(k: &Kernel<MockPlatform>, pid: ProcessId, slot: CapSlot) -> PermissionSet {
+    *k.processes
+        .get(pid)
+        .unwrap()
+        .capabilities()
+        .get(slot)
+        .unwrap()
+        .permissions()
+}
+
+fn error_of(outcome: SyscallOutcome) -> KernelError {
+    match outcome {
+        SyscallOutcome::Complete(SyscallResult::Error(e)) => e,
+        _ => panic!("expected an error"),
+    }
+}
+
+// ---- halt ----
+
+#[test]
+fn init_cannot_halt_without_a_system_control_cap() {
+    let (mut k, _) = kernel_with_process();
+    let e = error_of(k.handle_syscall(Syscall::Halt {
+        control: CapSlot::new(0).unwrap(),
+    }));
+    assert!(
+        matches!(e, KernelError::WrongObject),
+        "slot 0 is ProcessCreate"
+    );
+    let e = error_of(k.handle_syscall(Syscall::Halt {
+        control: CapSlot::new(9).unwrap(),
+    }));
+    assert!(matches!(e, KernelError::InvalidSlot(_)));
+}
+
+#[test]
+#[should_panic(expected = "halt")]
+fn system_control_cap_halts() {
+    let (mut k, init) = booted();
+    let control = slot_holding(&k, init, Resource::SystemControl);
+    k.handle_syscall(Syscall::Halt { control });
+}
+
+#[test]
+fn halt_needs_execute_on_the_cap() {
+    let (mut k, init) = booted();
+    let control = slot_holding(&k, init, Resource::SystemControl);
+    let weak = k
+        .mint(
+            init,
+            control,
+            Badge::new(0),
+            PermissionSet::empty().with(Permission::Delegate),
+        )
+        .unwrap();
+    let e = error_of(k.handle_syscall(Syscall::Halt { control: weak }));
+    assert!(matches!(e, KernelError::PermissionDenied { .. }));
+}
+
+#[test]
+#[should_panic(expected = "halt")]
+fn any_holder_of_the_cap_may_halt_not_just_init() {
+    let (mut k, init) = booted();
+    let other = k.create_process_internal().unwrap();
+    let tid = k.spawn_thread_for_test(other, Priority::DEFAULT, TimeSlice::DEFAULT);
+    k.grant_cap_for_test(
+        other,
+        Resource::SystemControl,
+        PermissionSet::empty().with(Permission::Execute),
+    );
+    let _ = init;
+    k.switch_to_thread_for_test(tid);
+    let control = slot_holding(&k, other, Resource::SystemControl);
+    k.handle_syscall(Syscall::Halt { control });
+}
+
+// ---- boot authority ----
+
+#[test]
+fn init_gets_mmio_irq_and_control_caps_it_can_delegate() {
+    let (k, init) = booted();
+    let delegate = Permission::Delegate;
+    for d in board() {
+        let region = k.device_region_at(d.base).unwrap();
+        let mem = slot_holding(&k, init, Resource::Memory(region));
+        let p = perms_of(&k, init, mem);
+        assert!(p.allows(Permission::Read) && p.allows(Permission::Write) && p.allows(delegate));
+        assert!(!p.allows(Permission::Execute), "MMIO is never executable");
+        let irq = slot_holding(&k, init, Resource::Interrupt(d.irq.unwrap()));
+        let p = perms_of(&k, init, irq);
+        assert!(p.allows(Permission::Execute) && p.allows(delegate));
+    }
+    let control = slot_holding(&k, init, Resource::SystemControl);
+    let p = perms_of(&k, init, control);
+    assert!(p.allows(Permission::Execute) && p.allows(delegate));
+}
+
+#[test]
+fn boot_authority_keeps_existing_slots() {
+    let (mut k, init) = kernel_with_process();
+    let before = k.cap_slots_for_test(init);
+    k.register_board(init, &board()).unwrap();
+    k.grant_boot_authority(init, &board()).unwrap();
+    let after = k.cap_slots_for_test(init);
+    for (b, a) in before.iter().zip(after.iter()) {
+        assert!(!b || *a, "an existing slot was disturbed");
+    }
+    assert_eq!(after.iter().filter(|s| **s).count(), 1 + 2 + 2 + 1);
+}
+
+#[test]
+fn init_can_map_a_device_through_its_cap() {
+    let (mut k, init) = booted();
+    let region = slot_holding(
+        &k,
+        init,
+        Resource::Memory(k.device_region_at(PhysicalAddress::from_raw(UART)).unwrap()),
+    );
+    let outcome = k.handle_syscall(Syscall::MapRegion {
+        region,
+        va: VirtualAddress::from_raw(0x10_0000),
+        perms: PagePerms::ReadWrite,
+    });
+    assert!(matches!(
+        outcome,
+        SyscallOutcome::Complete(SyscallResult::Ok)
+    ));
+    let e = error_of(k.handle_syscall(Syscall::MapRegion {
+        region,
+        va: VirtualAddress::from_raw(0x20_0000),
+        perms: PagePerms::ReadExecute,
+    }));
+    assert!(matches!(e, KernelError::PermissionDenied { .. }));
+}
+
+#[test]
+fn init_can_route_a_board_irq() {
+    let (mut k, init) = booted();
+    let irq = slot_holding(&k, init, Resource::Interrupt(IrqId::from_raw(1)));
+    let notification = k.create_notification_cap(init).unwrap();
+    let outcome = k.handle_syscall(Syscall::SetIrqNotification { irq, notification });
+    assert!(matches!(
+        outcome,
+        SyscallOutcome::Complete(SyscallResult::Ok)
+    ));
+}
+
+#[test]
+fn granting_needs_a_registered_board() {
+    let (mut k, init) = kernel_with_process();
+    assert!(matches!(
+        k.grant_boot_authority(init, &board()),
+        Err(KernelError::NoSuchObject)
+    ));
+}
+
+#[test]
+fn granting_needs_the_regions_to_be_inits() {
+    let (mut k, init) = kernel_with_process();
+    let other = k.create_process_internal().unwrap();
+    k.register_board(other, &board()).unwrap();
+    assert!(matches!(
+        k.grant_boot_authority(init, &board()),
+        Err(KernelError::NoSuchObject)
+    ));
+}
+
+#[test]
+fn board_devices_may_not_overlap() {
+    let (mut k, init) = kernel_with_process();
+    let overlapping = [device(UART, 2, None), device(UART + 0x1000, 1, None)];
+    assert!(matches!(
+        k.register_board(init, &overlapping),
+        Err(KernelError::AddressInUse)
+    ));
+}
+
+#[test]
+fn board_devices_may_not_alias_the_frame_pool() {
+    let (mut k, init) = kernel_with_process();
+    assert!(matches!(
+        k.register_board(init, &[device(0x8400_0000, 1, None)]),
+        Err(KernelError::InvalidAddress)
+    ));
+}
+
+#[test]
+fn board_devices_must_be_page_aligned_and_in_range() {
+    let (mut k, init) = kernel_with_process();
+    assert!(matches!(
+        k.register_board(init, &[device(UART + 8, 1, None)]),
+        Err(KernelError::InvalidAddress)
+    ));
+    assert!(matches!(
+        k.register_board(init, &[device(usize::MAX & !0xfff, 2, None)]),
+        Err(KernelError::InvalidAddress)
+    ));
+}
+
+#[test]
+fn board_irqs_must_be_routable() {
+    let (mut k, init) = kernel_with_process();
+    let bad = IrqId::from_raw(u16::MAX);
+    assert!(matches!(
+        k.register_board(init, &[device(UART, 1, Some(u16::MAX))]),
+        Err(KernelError::InvalidIrq(i)) if i == bad
+    ));
+}
+
+// ---- region address ----
+
+#[test]
+fn region_address_reports_the_physical_base() {
+    let (mut k, init) = booted();
+    let pool = k
+        .create_region_cap(init, PageCount::new(2).unwrap())
+        .unwrap();
+    let outcome = k.handle_syscall(Syscall::RegionAddress { region: pool });
+    let SyscallOutcome::Complete(SyscallResult::Value(pa)) = outcome else {
+        panic!("expected an address");
+    };
+    let Resource::Memory(id) = *k
+        .processes
+        .get(init)
+        .unwrap()
+        .capabilities()
+        .get(pool)
+        .unwrap()
+        .resource()
+    else {
+        panic!("not a region cap");
+    };
+    assert_eq!(Some(pa), k.region_base(id).map(|b| b.raw()));
+
+    let uart = slot_holding(
+        &k,
+        init,
+        Resource::Memory(k.device_region_at(PhysicalAddress::from_raw(UART)).unwrap()),
+    );
+    let outcome = k.handle_syscall(Syscall::RegionAddress { region: uart });
+    assert!(matches!(
+        outcome,
+        SyscallOutcome::Complete(SyscallResult::Value(UART))
+    ));
+}
+
+#[test]
+fn region_address_needs_read() {
+    let (mut k, init) = booted();
+    let pool = k
+        .create_region_cap(init, PageCount::new(1).unwrap())
+        .unwrap();
+    let blind = k
+        .mint(
+            init,
+            pool,
+            Badge::new(0),
+            PermissionSet::empty().with(Permission::Write),
+        )
+        .unwrap();
+    let e = error_of(k.handle_syscall(Syscall::RegionAddress { region: blind }));
+    assert!(matches!(e, KernelError::PermissionDenied { .. }));
+}
+
+#[test]
+fn region_address_rejects_other_objects() {
+    let (mut k, _) = booted();
+    // An endpoint cap carries Read, so this fails on the object type.
+    let SyscallOutcome::Complete(SyscallResult::Slot(endpoint)) =
+        k.handle_syscall(Syscall::CreateEndpoint)
+    else {
+        panic!("expected an endpoint");
+    };
+    let e = error_of(k.handle_syscall(Syscall::RegionAddress { region: endpoint }));
+    assert!(matches!(e, KernelError::WrongObject));
+}

crates/kernel/src/tests/capability.rs

@@ -1,10 +1,9 @@
 use super::*;
 use crate::{SyscallOutcome, SyscallResult};
-use domain::resource::Resource;
 use domain::syscall::Syscall;
-use types::bounded::CapSlot;
-use types::permission::{Permission, PermissionSet};
 use types::address::DataRef;
+use types::bounded::CapSlot;
+use types::permission::PermissionSet;
 
 #[test]
 fn delegate_without_delegate_permission_fails() {
@@ -58,131 +57,16 @@ fn delegate_with_valid_cap_succeeds() {
 // --- Generation-based revocation ---
 
 #[test]
-fn revoke_resource_invalidates_all_caps() {
-    let (mut k, pid) = kernel_with_process();
-    let ep_id = k.create_endpoint_for_test();
-
-    let cap_slot = k.grant_cap_for_test(
-        pid,
-        Resource::Endpoint(ep_id),
-        PermissionSet::empty().with(Permission::Read),
+fn every_representable_slot_is_rejected_not_panicking() {
+    let (mut k, _) = kernel_with_process();
+    for raw in 1..=CapSlot::MAX {
+        let outcome = k.handle_syscall(Syscall::Send {
+            endpoint: CapSlot::new(raw).unwrap(),
+            message: domain::message::Message::empty(),
+        });
+        assert!(
+            matches!(outcome, SyscallOutcome::Complete(SyscallResult::Error(_))),
+            "slot {raw} should be an error"
         );
-
-    // Revoke the endpoint
-    k.revoke_resource(&Resource::Endpoint(ep_id));
-
-    // Cap is now invalid — check_cap should reject with RevokedCapability
-    let outcome = k.handle_syscall(Syscall::Receive { endpoint: cap_slot });
-    assert!(matches!(
-        outcome,
-        SyscallOutcome::Complete(SyscallResult::Error(domain::error::KernelError::RevokedCapability(_)))
-    ));
     }
-
-#[test]
-fn new_cap_after_revoke_uses_current_generation() {
-    let (mut k, pid) = kernel_with_process();
-    let ep_id = k.create_endpoint_for_test();
-
-    // Grant, revoke, grant again
-    let old_slot = k.grant_cap_for_test(
-        pid,
-        Resource::Endpoint(ep_id),
-        PermissionSet::empty().with(Permission::Read),
-    );
-
-    k.revoke_resource(&Resource::Endpoint(ep_id));
-
-    // Old cap is dead
-    let outcome = k.handle_syscall(Syscall::Receive { endpoint: old_slot });
-    assert!(matches!(
-        outcome,
-        SyscallOutcome::Complete(SyscallResult::Error(domain::error::KernelError::RevokedCapability(_)))
-    ));
-
-    // New cap with current generation works
-    let new_slot = k.grant_cap_for_test(
-        pid,
-        Resource::Endpoint(ep_id),
-        PermissionSet::empty().with(Permission::Read),
-    );
-
-    let outcome = k.handle_syscall(Syscall::Receive { endpoint: new_slot });
-    // Should block (no sender), not error — proving the cap is valid
-    assert!(matches!(outcome, SyscallOutcome::BlockCaller(_)));
-}
-
-#[test]
-fn revoke_does_not_affect_other_resources() {
-    let (mut k, pid) = kernel_with_process();
-    let ep1 = k.create_endpoint_for_test();
-    let ep2 = k.create_endpoint_for_test();
-
-    let slot1 = k.grant_cap_for_test(
-        pid,
-        Resource::Endpoint(ep1),
-        PermissionSet::empty().with(Permission::Read),
-    );
-    let slot2 = k.grant_cap_for_test(
-        pid,
-        Resource::Endpoint(ep2),
-        PermissionSet::empty().with(Permission::Read),
-    );
-
-    // Revoke only ep1
-    k.revoke_resource(&Resource::Endpoint(ep1));
-
-    // ep1 cap is revoked
-    let outcome = k.handle_syscall(Syscall::Receive { endpoint: slot1 });
-    assert!(matches!(
-        outcome,
-        SyscallOutcome::Complete(SyscallResult::Error(domain::error::KernelError::RevokedCapability(_)))
-    ));
-
-    // ep2 cap still works
-    let outcome = k.handle_syscall(Syscall::Receive { endpoint: slot2 });
-    assert!(matches!(outcome, SyscallOutcome::BlockCaller(_)));
-}
-
-#[test]
-fn revoke_syscall_invalidates_via_generation() {
-    let (mut k, pid) = kernel_with_process();
-    let ep_id = k.create_endpoint_for_test();
-
-    let cap_slot = k.grant_cap_for_test(
-        pid,
-        Resource::Endpoint(ep_id),
-        PermissionSet::empty()
-            .with(Permission::Read)
-            .with(Permission::Revoke),
-    );
-
-    // Revoke via syscall
-    let outcome = k.handle_syscall(Syscall::Revoke { slot: cap_slot });
-    assert!(matches!(outcome, SyscallOutcome::Complete(SyscallResult::Ok)));
-
-    // The cap itself is now revoked (generation mismatch)
-    let outcome = k.handle_syscall(Syscall::Receive { endpoint: cap_slot });
-    assert!(matches!(
-        outcome,
-        SyscallOutcome::Complete(SyscallResult::Error(domain::error::KernelError::RevokedCapability(_)))
-    ));
-}
-
-#[test]
-fn revoke_syscall_without_revoke_permission_fails() {
-    let (mut k, pid) = kernel_with_process();
-    let ep_id = k.create_endpoint_for_test();
-
-    let cap_slot = k.grant_cap_for_test(
-        pid,
-        Resource::Endpoint(ep_id),
-        PermissionSet::empty().with(Permission::Read),
-    );
-
-    let outcome = k.handle_syscall(Syscall::Revoke { slot: cap_slot });
-    assert!(matches!(
-        outcome,
-        SyscallOutcome::Complete(SyscallResult::Error(_))
-    ));
 }

crates/kernel/src/tests/captree_model.rs

@@ -0,0 +1,326 @@
+//! Randomized check of the derivation tree against an independent model.
+//! The model applies the rules of docs/ipc.md (derive records a parent,
+//! delete re-parents, revoke removes the subtree, death deletes everything
+//! a process holds) to its own data; after every step the kernel must hold
+//! exactly the capabilities the model says are alive.
+
+extern crate std;
+
+use std::collections::HashMap;
+use std::vec::Vec;
+
+use super::*;
+use crate::{SyscallOutcome, SyscallResult};
+use domain::syscall::Syscall;
+use types::address::{DataRef, VirtualAddress};
+use types::badge::Badge;
+use types::bounded::{CapSlot, PageCount};
+use types::id::ThreadId;
+use types::mapping::PagePerms;
+use types::permission::{Permission, PermissionSet};
+
+const STEPS: usize = 1500;
+
+struct Rng(u64);
+
+impl Rng {
+    fn next(&mut self) -> u64 {
+        self.0 ^= self.0 << 13;
+        self.0 ^= self.0 >> 7;
+        self.0 ^= self.0 << 17;
+        self.0
+    }
+
+    fn below(&mut self, n: usize) -> usize {
+        (self.next() % n as u64) as usize
+    }
+
+    fn pick<T: Copy>(&mut self, xs: &[T]) -> Option<T> {
+        (!xs.is_empty()).then(|| xs[self.below(xs.len())])
+    }
+}
+
+#[derive(Clone, Copy)]
+struct Node {
+    parent: Option<usize>,
+    is_region: bool,
+}
+
+/// The reference model: logical capabilities and where each one lives.
+#[derive(Default)]
+struct Model {
+    nodes: Vec<Node>,
+    alive: HashMap<usize, (ProcessId, CapSlot)>,
+}
+
+impl Model {
+    fn add(&mut self, at: (ProcessId, CapSlot), parent: Option<usize>, is_region: bool) -> usize {
+        self.nodes.push(Node { parent, is_region });
+        let id = self.nodes.len() - 1;
+        self.alive.insert(id, at);
+        id
+    }
+
+    fn delete(&mut self, id: usize) {
+        let grandparent = self.nodes[id].parent;
+        for n in 0..self.nodes.len() {
+            if self.alive.contains_key(&n) && self.nodes[n].parent == Some(id) {
+                self.nodes[n].parent = grandparent;
+            }
+        }
+        self.alive.remove(&id);
+    }
+
+    fn is_descendant(&self, mut n: usize, root: usize) -> bool {
+        while let Some(p) = self.nodes[n].parent {
+            if p == root {
+                return true;
+            }
+            n = p;
+        }
+        false
+    }
+
+    fn revoke(&mut self, root: usize) {
+        let doomed: Vec<usize> = self
+            .alive
+            .keys()
+            .copied()
+            .filter(|&n| self.is_descendant(n, root))
+            .collect();
+        for n in doomed {
+            self.alive.remove(&n);
+        }
+    }
+
+    fn held_by(&self, pid: ProcessId) -> Vec<(usize, CapSlot)> {
+        self.alive
+            .iter()
+            .filter(|(_, (p, _))| *p == pid)
+            .map(|(id, (_, s))| (*id, *s))
+            .collect()
+    }
+}
+
+fn all() -> PermissionSet {
+    PermissionSet::empty()
+        .with(Permission::Read)
+        .with(Permission::Write)
+        .with(Permission::Execute)
+        .with(Permission::Delegate)
+}
+
+struct World {
+    k: Kernel<MockPlatform>,
+    m: Model,
+    pids: [ProcessId; 3],
+    tids: [ThreadId; 3],
+}
+
+impl World {
+    fn new() -> Self {
+        let (k, a) = kernel_with_process();
+        let ta = k.current_thread().unwrap();
+        let mut w = Self {
+            k,
+            m: Model::default(),
+            pids: [a; 3],
+            tids: [ta; 3],
+        };
+        // init's own boot capability (ProcessCreate) is a kernel root.
+        let create = CapSlot::new(0).unwrap();
+        w.m.add((a, create), None, false);
+        for i in 1..3 {
+            w.spawn(i);
+        }
+        for call in [Syscall::CreateEndpoint, Syscall::CreateNotification] {
+            let s = w.slot(0, call);
+            w.m.add((a, s), None, false);
+        }
+        let r = w.slot(
+            0,
+            Syscall::CreateRegion {
+                pages: PageCount::new(1).unwrap(),
+            },
+        );
+        w.m.add((a, r), None, true);
+        w
+    }
+
+    fn slot(&mut self, who: usize, call: Syscall) -> CapSlot {
+        self.k.switch_to_thread_for_test(self.tids[who]);
+        match self.k.handle_syscall(call) {
+            SyscallOutcome::Complete(SyscallResult::Slot(s)) => s,
+            _ => panic!("expected a slot"),
+        }
+    }
+
+    /// (Re)creates process `i` from init; init gets a root process cap.
+    fn spawn(&mut self, i: usize) {
+        let cap = self.slot(
+            0,
+            Syscall::CreateProcess {
+                create_cap: CapSlot::new(0).unwrap(),
+                image: DataRef::empty(),
+            },
+        );
+        self.pids[i] = self.k.process_of_cap_for_test(cap);
+        self.tids[i] =
+            self.k
+                .spawn_thread_for_test(self.pids[i], Priority::DEFAULT, TimeSlice::DEFAULT);
+        self.m.add((self.pids[0], cap), None, false);
+    }
+
+    fn run(&mut self, who: usize, call: Syscall) -> bool {
+        self.k.switch_to_thread_for_test(self.tids[who]);
+        !matches!(
+            self.k.handle_syscall(call),
+            SyscallOutcome::Complete(SyscallResult::Error(_))
+        )
+    }
+
+    fn step(&mut self, rng: &mut Rng) {
+        let who = rng.below(3);
+        let pid = self.pids[who];
+        let held = self.m.held_by(pid);
+        let Some((id, slot)) = rng.pick(&held) else {
+            return;
+        };
+
+        match rng.below(10) {
+            0..=2 => {
+                // Badges only go on endpoints and notifications; the kernel
+                // must refuse the rest, so try both.
+                let badge = Badge::new(rng.below(2));
+                let before = self.k.cap_slots_for_test(pid);
+                let ok = self.run(
+                    who,
+                    Syscall::Mint {
+                        slot,
+                        badge,
+                        permissions: all(),
+                    },
+                );
+                if ok {
+                    let new = newly_used(before, self.k.cap_slots_for_test(pid));
+                    let is_region = self.m.nodes[id].is_region;
+                    self.m.add((pid, new), Some(id), is_region);
+                }
+            }
+            3..=4 => {
+                // Delegate through any process cap the caller holds.
+                let proc_caps: Vec<(CapSlot, ProcessId)> = held
+                    .iter()
+                    .filter_map(|(_, s)| {
+                        self.k.process_cap_target_for_test(pid, *s).map(|t| (*s, t))
+                    })
+                    .collect();
+                if let Some((to, target)) = rng.pick(&proc_caps) {
+                    let before = self.k.cap_slots_for_test(target);
+                    let ok = self.run(
+                        who,
+                        Syscall::Delegate {
+                            slot,
+                            to_endpoint: to,
+                            permissions: all(),
+                        },
+                    );
+                    if ok {
+                        let new = newly_used(before, self.k.cap_slots_for_test(target));
+                        let is_region = self.m.nodes[id].is_region;
+                        self.m.add((target, new), Some(id), is_region);
+                    }
+                }
+            }
+            // init keeps its ProcessCreate cap so processes can be re-made.
+            5 if !(who == 0 && slot == CapSlot::new(0).unwrap()) => {
+                if self.run(who, Syscall::DropCap { slot }) {
+                    self.m.delete(id);
+                }
+            }
+            6..=7 => {
+                assert!(
+                    self.run(who, Syscall::Revoke { slot }),
+                    "revoking a held cap failed"
+                );
+                self.m.revoke(id);
+            }
+            8 => {
+                let va = VirtualAddress::from_raw(0x30000 + rng.below(16) * 0x1000);
+                let _ = self.run(
+                    who,
+                    Syscall::MapRegion {
+                        region: slot,
+                        va,
+                        perms: PagePerms::ReadWrite,
+                    },
+                );
+            }
+            _ if who == 0 && rng.below(4) == 0 => {
+                let victim = 1 + rng.below(2);
+                let vp = self.pids[victim];
+                // init's cap to the victim may already be revoked; kill it
+                // directly, as a supervisor holding a cap would.
+                for (n, _) in self.m.held_by(vp) {
+                    self.m.delete(n);
+                }
+                self.k.destroy_process(vp);
+                self.spawn(victim);
+            }
+            _ => {}
+        }
+    }
+
+    fn check(&self) {
+        for &pid in &self.pids {
+            let used = self.k.cap_slots_for_test(pid);
+            let mut expected = [false; 64];
+            for (_, s) in self.m.held_by(pid) {
+                expected[s.value() as usize] = true;
+            }
+            assert_eq!(used, expected, "{pid:?} holds the wrong capabilities");
+        }
+        // Every capability-backed mapping is backed by a live capability
+        // of the mapping process.
+        for (_, region) in self.k.regions.iter() {
+            for m in region.mappings() {
+                if let Some(via) = m.via {
+                    assert!(self.k.resolves(via), "mapping outlived its capability");
+                    assert_eq!(via.process, m.process);
+                }
+            }
+        }
+    }
+}
+
+fn newly_used(before: [bool; 64], after: [bool; 64]) -> CapSlot {
+    (0..64)
+        .find(|&i| after[i] && !before[i])
+        .and_then(|i| CapSlot::new(i as u8))
+        .expect("a new slot")
+}
+
+#[test]
+fn derivation_tree_matches_the_model() {
+    for seed in [5u64, 0xBADC0DE, 31337, 0x5EED, 2024] {
+        let mut world = World::new();
+        let mut rng = Rng(seed);
+        let mut revokes = 0;
+        for _ in 0..STEPS {
+            let before = world.m.alive.len();
+            world.step(&mut rng);
+            if world.m.alive.len() < before {
+                revokes += 1;
+            }
+            world.check();
+        }
+        assert!(
+            revokes > 20,
+            "seed {seed:#x}: too little deletion exercised"
+        );
+        assert!(
+            world.m.nodes.len() > 100,
+            "seed {seed:#x}: too little derivation"
+        );
+    }
+}

crates/kernel/src/tests/exit.rs

@@ -1,5 +1,5 @@
 use super::*;
-use crate::{SyscallOutcome, SyscallResult};
+use crate::SyscallOutcome;
 use domain::syscall::Syscall;
 
 #[test]
@@ -21,5 +21,5 @@ fn exit_thread_last_thread_destroys_process() {
     let (mut k, pid) = kernel_with_process();
     k.handle_syscall(Syscall::ExitThread);
     // Process should be gone since it had only one thread
-    assert!(k.process_exists(pid) == false);
+    assert!(!k.process_exists(pid));
 }

crates/kernel/src/tests/helpers.rs

@@ -1,4 +1,3 @@
-use domain::memory::page_pool::PagePool;
 use domain::resource::Resource;
 use domain::scheduler::Scheduler;
 use domain::thread::ThreadState;
@@ -6,25 +5,22 @@ use platform::Platform;
 use types::{
     address::PhysicalAddress,
     bounded::{CapSlot, Priority},
-    id::{EndpointId, IrqId, ProcessId, ThreadId},
+    id::{EndpointId, ProcessId, ThreadId},
     permission::PermissionSet,
     time::TimeSlice,
 };
 
-use crate::Kernel;
 use super::mock_platform::MockPlatform;
+use crate::Kernel;
 
 pub fn test_kernel() -> Kernel<MockPlatform> {
     let mock = MockPlatform::new(1);
-    let pool = PagePool::new(PhysicalAddress::from_raw(0x8000_0000), 1024);
-    Kernel::new(mock, pool)
+    Kernel::new(mock, PhysicalAddress::from_raw(0x8400_0000), 1024)
 }
 
 pub fn kernel_with_process() -> (Kernel<MockPlatform>, ProcessId) {
     let mut kernel = test_kernel();
-    let (pid, _tid) = kernel
-        .boot(Priority::DEFAULT, TimeSlice::DEFAULT)
-        .unwrap();
+    let (pid, _tid) = kernel.boot(Priority::DEFAULT, TimeSlice::DEFAULT).unwrap();
     (kernel, pid)
 }
 
@@ -35,22 +31,18 @@ impl Kernel<MockPlatform> {
         priority: Priority,
         time_slice: TimeSlice,
     ) -> ThreadId {
-        let tid = self.threads.spawn(pid, priority, time_slice, None).expect("spawn");
+        let tid = self
+            .threads
+            .spawn(pid, priority, time_slice, None)
+            .expect("spawn");
         let _ = self.processes.get_mut(pid).map(|p| p.add_thread(tid));
         let core = self.platform.core_id();
+        self.set_home(tid, core);
         self.scheduler.add(tid, priority, core);
         tid
     }
 
-    pub fn register_irq_for_test(&mut self, irq: IrqId, thread: ThreadId) {
-        let _ = self.irqs.register(irq, thread);
-    }
-
-    pub fn block_thread_for_test(
-        &mut self,
-        tid: ThreadId,
-        reason: domain::thread::BlockReason,
-    ) {
+    pub fn block_thread_for_test(&mut self, tid: ThreadId, reason: domain::thread::BlockReason) {
         let core = self.platform.core_id();
         if let Ok(t) = self.threads.get_mut(tid) {
             if matches!(t.state(), ThreadState::Ready) {
@@ -63,30 +55,44 @@ impl Kernel<MockPlatform> {
 
     pub fn switch_to_thread_for_test(&mut self, tid: ThreadId) {
         let core = self.platform.core_id();
+        assert_eq!(
+            self.home(tid),
+            core,
+            "a thread only ever runs on its home core"
+        );
 
+        // Only a thread ready in this core's queue can be switched to;
+        // otherwise leave the core as it is.
+        let switchable = self.scheduler.queued_on(tid) == Some(core)
+            && self
+                .threads
+                .get(tid)
+                .is_ok_and(|t| matches!(t.state(), ThreadState::Ready));
         if let Some(current) = self.scheduler.current(core) {
-            if current == tid {
+            if current == tid || !switchable {
                 return;
             }
-            if let Ok(t) = self.threads.get_mut(current) {
-                if matches!(t.state(), ThreadState::Running(_)) {
+            if let Ok(t) = self.threads.get_mut(current)
+                && matches!(t.state(), ThreadState::Running(_))
+            {
                 let priority = t.priority();
                 let _ = t.preempt();
                 self.scheduler.add(current, priority, core);
             }
         }
-        }
 
-        if let Ok(t) = self.threads.get(tid) {
-            if matches!(t.state(), ThreadState::Ready) {
-                self.scheduler.next(core);
+        if let Ok(t) = self.threads.get(tid)
+            && matches!(t.state(), ThreadState::Ready)
+            && self.scheduler.run_now(core, tid)
+        {
             let _ = self.threads.get_mut(tid).map(|t| t.set_running(core));
         }
     }
-    }
 
     pub fn create_endpoint_for_test(&mut self) -> EndpointId {
-        self.endpoints.create().expect("create endpoint")
+        self.endpoints
+            .create(ProcessId::from_raw(0))
+            .expect("create endpoint")
     }
 
     pub fn grant_cap_for_test(
@@ -95,6 +101,95 @@ impl Kernel<MockPlatform> {
         resource: Resource,
         permissions: PermissionSet,
     ) -> CapSlot {
-        self.grant_cap(pid, resource, permissions).expect("grant cap")
+        self.grant_cap(pid, resource, permissions)
+            .expect("grant cap")
+    }
+
+    pub fn endpoint_of_cap_for_test(&self, pid: ProcessId, slot: CapSlot) -> EndpointId {
+        match self
+            .processes
+            .get(pid)
+            .unwrap()
+            .capabilities()
+            .get(slot)
+            .unwrap()
+            .resource()
+        {
+            Resource::Endpoint(id) => *id,
+            _ => panic!("not an endpoint cap"),
+        }
+    }
+
+    /// The process a Process cap in init's table points at.
+    pub fn process_of_cap_for_test(&self, slot: CapSlot) -> ProcessId {
+        let init = ProcessId::from_raw(0);
+        match self
+            .processes
+            .get(init)
+            .unwrap()
+            .capabilities()
+            .get(slot)
+            .unwrap()
+            .resource()
+        {
+            Resource::Process(pid) => *pid,
+            _ => panic!("not a process cap"),
+        }
+    }
+
+    pub fn destroy_process_notifications_for_test(&mut self, owner: ProcessId) {
+        self.destroy_notifications_owned_by(owner);
+    }
+
+    /// The process a Process cap in `pid`'s table names, if it is one.
+    pub fn process_cap_target_for_test(&self, pid: ProcessId, slot: CapSlot) -> Option<ProcessId> {
+        match self
+            .processes
+            .get(pid)
+            .ok()?
+            .capabilities()
+            .get(slot)
+            .ok()?
+            .resource()
+        {
+            Resource::Process(target) if self.process_exists(*target) => Some(*target),
+            _ => None,
+        }
+    }
+
+    /// Whether `slot` of `pid` holds a capability whose object is gone.
+    pub fn is_dead_cap_for_test(&self, pid: ProcessId, slot: CapSlot) -> bool {
+        let Ok(p) = self.processes.get(pid) else {
+            return false;
+        };
+        p.capabilities()
+            .get(slot)
+            .is_ok_and(|c| self.resource_generation(c.resource()) != Some(*c.generation()))
+    }
+
+    /// Whether `slot` of `pid` holds a capability to a process that is gone.
+    pub fn is_dead_process_cap_for_test(&self, pid: ProcessId, slot: CapSlot) -> bool {
+        let Ok(p) = self.processes.get(pid) else {
+            return false;
+        };
+        match p.capabilities().get(slot).map(|c| *c.resource()) {
+            Ok(Resource::Process(target)) => !self.process_exists(target),
+            _ => false,
+        }
+    }
+
+    /// Which slots of `pid`'s capability table are occupied.
+    pub fn cap_slots_for_test(&self, pid: ProcessId) -> [bool; 64] {
+        let mut used = [false; 64];
+        if let Ok(p) = self.processes.get(pid) {
+            for (slot, _) in p.capabilities().iter() {
+                used[slot.value() as usize] = true;
+            }
+        }
+        used
+    }
+
+    pub fn thread_state_for_test(&self, tid: ThreadId) -> Option<ThreadState> {
+        self.threads.get(tid).ok().map(|t| *t.state())
     }
 }

crates/kernel/src/tests/invariants.rs

@@ -0,0 +1,299 @@
+//! Randomized whole-kernel check of the memory model. Three processes issue
+//! thousands of random (often hostile) memory operations; after every step
+//! the kernel's records, the quotas and the mock "hardware" must agree.
+
+use super::*;
+use crate::{SyscallOutcome, SyscallResult};
+use domain::memory::{RegionBacking, frame::FrameUse};
+use domain::syscall::Syscall;
+use platform::Platform;
+use types::address::{DataRef, VirtualAddress};
+use types::bounded::{CapSlot, PageCount};
+use types::id::ThreadId;
+use types::mapping::PagePerms;
+
+const PAGE: usize = 4096;
+const PROCS: usize = 3;
+const STEPS: usize = 4000;
+
+struct Rng(u64);
+
+impl Rng {
+    fn next(&mut self) -> u64 {
+        // xorshift64
+        self.0 ^= self.0 << 13;
+        self.0 ^= self.0 >> 7;
+        self.0 ^= self.0 << 17;
+        self.0
+    }
+
+    fn below(&mut self, n: usize) -> usize {
+        (self.next() % n as u64) as usize
+    }
+
+    /// A VA that is usually plausible and sometimes plain hostile.
+    fn va(&mut self, known: &[usize]) -> usize {
+        match self.below(6) {
+            0 | 1 if !known.is_empty() => known[self.below(known.len())],
+            2 => self.below(0x0300_0000) & !(PAGE - 1),
+            3 => self.next() as usize,
+            4 => 0x8020_0000 + self.below(64) * PAGE,
+            _ => 0x10000 + self.below(64) * PAGE,
+        }
+    }
+}
+
+struct World {
+    k: Kernel<MockPlatform>,
+    pids: [ProcessId; PROCS],
+    tids: [ThreadId; PROCS],
+    alive: [bool; PROCS],
+    /// A's process caps for B and C.
+    caps: [CapSlot; PROCS],
+    known: [[usize; 64]; PROCS],
+    known_len: [usize; PROCS],
+    rebirths: usize,
+}
+
+impl World {
+    fn new() -> Self {
+        let (mut k, pid_a) = kernel_with_process();
+        let tid_a = k.current_thread().unwrap();
+        let mut pids = [pid_a; PROCS];
+        let mut tids = [tid_a; PROCS];
+        let mut caps = [CapSlot::new(0).unwrap(); PROCS];
+        for i in 1..PROCS {
+            caps[i] = match k.handle_syscall(Syscall::CreateProcess {
+                create_cap: CapSlot::new(0).unwrap(),
+                image: DataRef::empty(),
+            }) {
+                SyscallOutcome::Complete(SyscallResult::Slot(s)) => s,
+                _ => panic!("create process"),
+            };
+            pids[i] = ProcessId::from_raw(i as u16);
+            tids[i] = k.spawn_thread_for_test(pids[i], Priority::DEFAULT, TimeSlice::DEFAULT);
+        }
+        Self {
+            k,
+            pids,
+            tids,
+            alive: [true; PROCS],
+            caps,
+            known: [[0; 64]; PROCS],
+            known_len: [0; PROCS],
+            rebirths: 0,
+        }
+    }
+
+    fn remember(&mut self, who: usize, va: usize) {
+        let n = self.known_len[who];
+        self.known[who][n % 64] = va;
+        self.known_len[who] = (n + 1).min(64);
+    }
+
+    fn known(&self, who: usize) -> &[usize] {
+        &self.known[who][..self.known_len[who]]
+    }
+
+    fn step(&mut self, rng: &mut Rng) {
+        let who = rng.below(PROCS);
+        if !self.alive[who] {
+            return;
+        }
+        self.k.switch_to_thread_for_test(self.tids[who]);
+        let pid = self.pids[who];
+        let known: [usize; 64] = self.known[who];
+        let known = &known[..self.known_len[who]];
+
+        match rng.below(10) {
+            0..=2 => {
+                let n = 1 + rng.below(4) as u16;
+                if let SyscallOutcome::Complete(SyscallResult::Value(va)) =
+                    self.k.handle_syscall(Syscall::RequestPages {
+                        count: PageCount::new(n).unwrap(),
+                    })
+                {
+                    for i in 0..n as usize {
+                        self.remember(who, va + i * PAGE);
+                    }
+                }
+            }
+            3..=4 => {
+                let addr = rng.va(known);
+                let count = PageCount::new(1 + rng.below(5) as u16).unwrap();
+                self.k.handle_syscall(Syscall::ReleasePages {
+                    addr: VirtualAddress::from_raw(addr),
+                    count,
+                });
+            }
+            5..=6 if who == 0 => {
+                let target = 1 + rng.below(PROCS - 1);
+                let src = rng.va(known);
+                let dst = rng.va(self.known(target));
+                let outcome = self.k.handle_syscall(Syscall::MapPage {
+                    process: self.caps[target],
+                    src_va: VirtualAddress::from_raw(src),
+                    dst_va: VirtualAddress::from_raw(dst),
+                    executable: rng.below(2) == 0,
+                });
+                if matches!(outcome, SyscallOutcome::Complete(SyscallResult::Ok)) {
+                    self.remember(target, dst);
+                }
+            }
+            7 => {
+                let pages = PageCount::new(1 + rng.below(3) as u16).unwrap();
+                if let Ok(id) = self.k.create_pool_region(pid, pages) {
+                    let other = rng.below(PROCS);
+                    for p in [who, other] {
+                        if self.alive[p] {
+                            let va = VirtualAddress::from_raw(rng.va(self.known(p)));
+                            let _ = self
+                                .k
+                                .map_region(id, self.pids[p], va, PagePerms::ReadWrite);
+                        }
+                    }
+                }
+            }
+            8 if who == 0 && rng.below(8) == 0 => {
+                let victim = 1 + rng.below(PROCS - 1);
+                let stale = self.caps[victim];
+                self.k.handle_syscall(Syscall::Kill { process: stale });
+                self.rebirths += 1;
+
+                // Re-create it; the pid slot is reused.
+                let fresh = match self.k.handle_syscall(Syscall::CreateProcess {
+                    create_cap: CapSlot::new(0).unwrap(),
+                    image: DataRef::empty(),
+                }) {
+                    SyscallOutcome::Complete(SyscallResult::Slot(s)) => s,
+                    _ => panic!("re-create process"),
+                };
+                assert_eq!(self.k.process_of_cap_for_test(fresh), self.pids[victim]);
+                self.tids[victim] = self.k.spawn_thread_for_test(
+                    self.pids[victim],
+                    Priority::DEFAULT,
+                    TimeSlice::DEFAULT,
+                );
+                self.known_len[victim] = 0;
+
+                // The old cap names the same pid but must reach nothing.
+                let src = rng.va(known);
+                let outcome = self.k.handle_syscall(Syscall::MapPage {
+                    process: stale,
+                    src_va: VirtualAddress::from_raw(src),
+                    dst_va: VirtualAddress::from_raw(0x10000),
+                    executable: false,
+                });
+                assert!(
+                    matches!(outcome, SyscallOutcome::Complete(SyscallResult::Error(_))),
+                    "stale process cap still works"
+                );
+                assert!(matches!(
+                    self.k.handle_syscall(Syscall::Kill { process: stale }),
+                    SyscallOutcome::Complete(SyscallResult::Error(_))
+                ));
+                self.k.handle_syscall(Syscall::DropCap { slot: stale });
+                self.caps[victim] = fresh;
+            }
+            _ => {}
+        }
+    }
+
+    fn check(&self) {
+        let k = &self.k;
+        let window = MockPlatform::USER_VA_START..MockPlatform::USER_VA_END;
+
+        // Every frame is either free or charged to exactly one quota.
+        let charged: usize = self.pids.iter().map(|&p| k.page_usage(p)).sum();
+        assert_eq!(
+            charged + k.free_page_count(),
+            k.frames.capacity(),
+            "frames leaked or double counted"
+        );
+
+        for (i, &pid) in self.pids.iter().enumerate() {
+            let frames_owned = k
+                .frames
+                .iter()
+                .filter(|(_, u)| {
+                    matches!(u, FrameUse::User { owner, .. } | FrameUse::PageTable { owner } if *owner == pid)
+                })
+                .count();
+            let region_pages: usize = k
+                .regions
+                .iter()
+                .filter(|(_, r)| r.owner() == pid && r.backing() == RegionBacking::Pool)
+                .map(|(_, r)| r.pages().value() as usize)
+                .sum();
+            assert_eq!(
+                k.page_usage(pid),
+                frames_owned + region_pages,
+                "quota of {pid:?} drifted"
+            );
+            if !self.alive[i] && i != 0 {
+                assert_eq!(k.page_usage(pid), 0);
+                assert_eq!(
+                    k.platform.mapping_count(pid),
+                    0,
+                    "dead {pid:?} still mapped"
+                );
+            }
+        }
+
+        // Hardware -> kernel: every live mapping is one the kernel recorded.
+        for (pid, va, pa) in k.platform.mappings() {
+            assert!(
+                window.contains(&va),
+                "{pid:?} mapped outside window at {va:#x}"
+            );
+            let v = VirtualAddress::from_raw(va);
+            let as_user = k.frames.find_user(pid, v).map(|(p, _)| p.raw());
+            let as_region = k.regions.covering(pid, v).and_then(|id| {
+                let r = k.regions.get(id)?;
+                let m = r.mappings().find(|m| m.process == pid)?;
+                Some(r.base().raw() + (va - m.va.raw()))
+            });
+            assert!(
+                as_user == Some(pa) || as_region == Some(pa),
+                "{pid:?} has unrecorded mapping {va:#x} -> {pa:#x}"
+            );
+        }
+
+        // Kernel -> hardware: every recorded user page is really mapped.
+        for (pa, usage) in k.frames.iter() {
+            if let FrameUse::User { owner, page, .. } = usage {
+                assert_eq!(
+                    k.platform.mapping(*owner, *page as usize * PAGE),
+                    Some(pa.raw()),
+                    "recorded page not mapped"
+                );
+            }
+        }
+        for (_, r) in k.regions.iter() {
+            for m in r.mappings() {
+                for i in 0..r.pages().value() as usize {
+                    assert_eq!(
+                        k.platform.mapping(m.process, m.va.raw() + i * PAGE),
+                        Some(r.base().raw() + i * PAGE)
+                    );
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn memory_model_holds_under_random_hostile_operations() {
+    for seed in [1u64, 0xDEAD_BEEF, 0x1234_5678_9ABC, 42, 7777] {
+        let mut world = World::new();
+        let mut rng = Rng(seed);
+        for _ in 0..STEPS {
+            world.step(&mut rng);
+            world.check();
+        }
+        assert!(
+            world.rebirths >= 5,
+            "seed {seed:#x} barely exercised kill/re-create"
+        );
+    }
+}