Implement domain and endpoint modules with capability management, message passing, and scheduling features

Cargo.lock

@@ -45,6 +45,9 @@ version = "0.1.0"
 [[package]]
 name = "domain"
 version = "0.1.0"
+dependencies = [
+ "types",
+]
 
 [[package]]
 name = "gatekeeper"
@@ -89,6 +92,10 @@ version = "0.1.0"
 [[package]]
 name = "platform"
 version = "0.1.0"
+dependencies = [
+ "domain",
+ "types",
+]
 
 [[package]]
 name = "power-server"

crates/domain/Cargo.toml

@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+types = { workspace = true }

crates/domain/src/capability/authority.rs

@@ -0,0 +1,33 @@
+use types::{
+    bounded::CapSlot,
+    id::ProcessId,
+    permission::{Permission, PermissionSet},
+};
+
+use crate::{capability::Capability, error::KernelError, resource::Resource};
+
+pub trait CapabilityAuthority {
+    fn grant(
+        &mut self,
+        to: ProcessId,
+        resource: Resource,
+        permissions: PermissionSet,
+    ) -> Result<CapSlot, KernelError>;
+
+    fn revoke(&mut self, owner: ProcessId, slot: CapSlot) -> Result<(), KernelError>;
+
+    fn delegate(
+        &mut self,
+        from: ProcessId,
+        slot: CapSlot,
+        to: ProcessId,
+        restrict: PermissionSet,
+    ) -> Result<CapSlot, KernelError>;
+
+    fn check(
+        &self,
+        caller: ProcessId,
+        slot: CapSlot,
+        needed: Permission,
+    ) -> Result<&Capability, KernelError>;
+}

crates/domain/src/capability/mod.rs

@@ -0,0 +1,82 @@
+use types::{bounded::CapSlot, generation::Generation, permission::PermissionSet};
+
+pub mod authority;
+
+use crate::{error::KernelError, resource::Resource};
+
+#[cfg(test)]
+#[path = "tests.rs"]
+mod tests;
+
+const MAX_CAPS_PER_PROCESS: usize = 16;
+
+pub struct Capability {
+    resource: Resource,
+    permissions: PermissionSet,
+    generation: Generation,
+}
+
+impl Capability {
+    pub(crate) fn new(
+        resource: Resource,
+        permissions: PermissionSet,
+        generation: Generation,
+    ) -> Self {
+        Self {
+            resource,
+            permissions,
+            generation,
+        }
+    }
+
+    pub fn resource(&self) -> &Resource {
+        &self.resource
+    }
+
+    pub fn permissions(&self) -> &PermissionSet {
+        &self.permissions
+    }
+
+    pub fn generation(&self) -> &Generation {
+        &self.generation
+    }
+}
+
+pub struct CapabilityTable {
+    slots: [Option<Capability>; MAX_CAPS_PER_PROCESS],
+}
+
+impl CapabilityTable {
+    pub fn new() -> Self {
+        Self {
+            slots: [const { None }; MAX_CAPS_PER_PROCESS],
+        }
+    }
+
+    pub fn get(&self, slot: CapSlot) -> Result<&Capability, KernelError> {
+        let idx = slot.value() as usize;
+        self.slots[idx]
+            .as_ref()
+            .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)?;
+
+        self.slots[idx] = Some(cap);
+        CapSlot::new(idx as u8).ok_or(KernelError::NoFreeSlot)
+    }
+
+    pub fn remove(&mut self, slot: CapSlot) -> Result<(), KernelError> {
+        let idx = slot.value() as usize;
+        if self.slots[idx].is_none() {
+            return Err(KernelError::InvalidSlot(slot));
+        }
+        self.slots[idx] = None;
+        Ok(())
+    }
+}

crates/domain/src/capability/tests.rs

@@ -0,0 +1,152 @@
+use super::*;
+use types::generation::Generation;
+use types::id::{EndpointId, RegionId};
+use types::permission::{Permission, PermissionSet};
+
+fn perms(permissions: &[Permission]) -> PermissionSet {
+    permissions
+        .iter()
+        .fold(PermissionSet::empty(), |set, &p| set.with(p))
+}
+
+fn endpoint_cap(id: u16, permissions: &[Permission]) -> Capability {
+    Capability::new(
+        Resource::Endpoint(EndpointId::from_raw(id)),
+        perms(permissions),
+        Generation::initial(),
+    )
+}
+
+fn memory_cap(id: u16, permissions: &[Permission]) -> Capability {
+    Capability::new(
+        Resource::Memory(RegionId::from_raw(id)),
+        perms(permissions),
+        Generation::initial(),
+    )
+}
+
+#[test]
+fn new_table_is_empty() {
+    let table = CapabilityTable::new();
+    let slot = CapSlot::new(0).unwrap();
+    assert!(table.get(slot).is_err());
+}
+
+#[test]
+fn insert_and_get() {
+    let mut table = CapabilityTable::new();
+    let slot = table.insert(endpoint_cap(1, &[Permission::Read])).unwrap();
+    let retrieved = table.get(slot).unwrap();
+
+    assert!(retrieved.permissions().allows(Permission::Read));
+    assert!(!retrieved.permissions().allows(Permission::Write));
+}
+
+#[test]
+fn remove_then_get_fails() {
+    let mut table = CapabilityTable::new();
+    let slot = table.insert(endpoint_cap(1, &[Permission::Read])).unwrap();
+    table.remove(slot).unwrap();
+    assert!(table.get(slot).is_err());
+}
+
+#[test]
+fn remove_invalid_slot_fails() {
+    let mut table = CapabilityTable::new();
+    let slot = CapSlot::new(5).unwrap();
+
+    assert!(table.remove(slot).is_err());
+}
+
+#[test]
+fn insert_reuses_removed_slot() {
+    let mut table = CapabilityTable::new();
+    let slot = table.insert(endpoint_cap(1, &[Permission::Read])).unwrap();
+    table.remove(slot).unwrap();
+    let new_slot = table.insert(endpoint_cap(2, &[Permission::Write])).unwrap();
+    assert_eq!(slot, new_slot);
+}
+
+#[test]
+fn full_table_returns_no_free_slot() {
+    let mut table = CapabilityTable::new();
+    for i in 0..MAX_CAPS_PER_PROCESS {
+        assert!(
+            table
+                .insert(endpoint_cap(i as u16, &[Permission::Read]))
+                .is_ok()
+        );
+    }
+    assert!(table.insert(endpoint_cap(999, &[])).is_err());
+}
+
+#[test]
+fn generation_mismatch_detected() {
+    let gen_v1 = Generation::initial();
+    let gen_v2 = gen_v1.next();
+
+    assert!(gen_v1.is_valid_against(&gen_v1));
+    assert!(!gen_v1.is_valid_against(&gen_v2));
+}
+
+#[test]
+fn restrict_to_never_escalates() {
+    let full = perms(&[Permission::Read, Permission::Write, Permission::Execute]);
+    let read_only = perms(&[Permission::Read]);
+
+    let restricted = full.restrict_to(&read_only);
+
+    assert!(restricted.allows(Permission::Read));
+    assert!(!restricted.allows(Permission::Write));
+    assert!(!restricted.allows(Permission::Execute));
+}
+
+#[test]
+fn restrict_to_cannot_add_permissions() {
+    let read_only = perms(&[Permission::Read]);
+    let wants_everything = perms(&[
+        Permission::Read,
+        Permission::Write,
+        Permission::Execute,
+        Permission::Delegate,
+        Permission::Revoke,
+    ]);
+
+    let result = read_only.restrict_to(&wants_everything);
+
+    assert!(result.allows(Permission::Read));
+    assert!(!result.allows(Permission::Write));
+    assert!(!result.allows(Permission::Execute));
+    assert!(!result.allows(Permission::Delegate));
+    assert!(!result.allows(Permission::Revoke));
+}
+
+#[test]
+fn is_subset_of() {
+    let rw = perms(&[Permission::Read, Permission::Write]);
+    let read_only = perms(&[Permission::Read]);
+
+    assert!(read_only.is_subset_of(&rw));
+    assert!(!rw.is_subset_of(&read_only));
+}
+
+#[test]
+fn empty_permission_set_allows_nothing() {
+    let empty = PermissionSet::empty();
+
+    assert!(!empty.allows(Permission::Read));
+    assert!(!empty.allows(Permission::Write));
+    assert!(!empty.allows(Permission::Execute));
+    assert!(!empty.allows(Permission::Delegate));
+    assert!(!empty.allows(Permission::Revoke));
+}
+
+#[test]
+fn capability_preserves_resource_and_permissions() {
+    let permissions = [Permission::Read, Permission::Write];
+    let expected_permissions = perms(&permissions);
+    let cap = memory_cap(42, &permissions);
+
+    assert_eq!(cap.permissions(), &expected_permissions);
+    assert_eq!(cap.generation(), &Generation::initial());
+}

crates/domain/src/endpoint/mod.rs

@@ -0,0 +1,78 @@
+use types::{
+    bounded::CapSlot,
+    generation::Generation,
+    id::{EndpointId, ProcessId, ThreadId},
+};
+
+use crate::{endpoint::wait_queue::WaitQueue, error::KernelError, message::Message};
+
+pub mod wait_queue;
+
+#[cfg(test)]
+#[path = "tests.rs"]
+mod tests;
+
+pub struct Endpoint {
+    id: EndpointId,
+    waiting_senders: WaitQueue,
+    waiting_receivers: WaitQueue,
+    generation: Generation,
+}
+
+impl Endpoint {
+    pub fn new(id: EndpointId) -> Self {
+        Self {
+            id,
+            waiting_senders: WaitQueue::new(),
+            waiting_receivers: WaitQueue::new(),
+            generation: Generation::initial(),
+        }
+    }
+
+    pub fn id(&self) -> &EndpointId {
+        &self.id
+    }
+
+    pub fn generation(&self) -> &Generation {
+        &self.generation
+    }
+
+    pub fn enqueue_sender(&mut self, thread: ThreadId) -> Option<()> {
+        self.waiting_senders.push(thread)
+    }
+
+    pub fn dequeue_sender(&mut self) -> Option<ThreadId> {
+        self.waiting_senders.pop()
+    }
+
+    pub fn enqueue_receiver(&mut self, thread: ThreadId) -> Option<()> {
+        self.waiting_receivers.push(thread)
+    }
+
+    pub fn dequeue_receiver(&mut self) -> Option<ThreadId> {
+        self.waiting_receivers.pop()
+    }
+
+    pub fn has_waiting_sender(&self) -> bool {
+        !self.waiting_senders.is_empty()
+    }
+
+    pub fn has_waiting_receiver(&self) -> bool {
+        !self.waiting_receivers.is_empty()
+    }
+
+    pub fn revoke(&mut self) {
+        self.generation = self.generation.next();
+    }
+}
+
+pub trait MessagePassing {
+    fn send(
+        &mut self,
+        sender: ProcessId,
+        endpoint: CapSlot,
+        message: Message,
+    ) -> Result<(), KernelError>;
+
+    fn receive(&mut self, receiver: ProcessId, endpoint: CapSlot) -> Result<Message, KernelError>;
+}

crates/domain/src/endpoint/tests.rs

@@ -0,0 +1,137 @@
+use crate::endpoint::wait_queue::MAX_WAITERS;
+
+use super::*;
+use types::id::{EndpointId, ThreadId};
+
+fn thread(id: u16) -> ThreadId {
+    ThreadId::from_raw(id)
+}
+
+fn test_endpoint() -> Endpoint {
+    Endpoint::new(EndpointId::from_raw(1))
+}
+
+// --- WaitQueue tests ---
+
+#[test]
+fn empty_queue_pop_returns_none() {
+    let mut queue = WaitQueue::new();
+    assert!(queue.pop().is_none());
+    assert!(queue.is_empty());
+}
+
+#[test]
+fn push_then_pop_returns_same_thread() {
+    let mut queue = 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();
+    queue.push(thread(1)).unwrap();
+    queue.push(thread(2)).unwrap();
+    queue.push(thread(3)).unwrap();
+
+    assert_eq!(queue.pop(), Some(thread(1)));
+    assert_eq!(queue.pop(), Some(thread(2)));
+    assert_eq!(queue.pop(), Some(thread(3)));
+    assert!(queue.pop().is_none());
+}
+
+#[test]
+fn full_queue_rejects_push() {
+    let mut queue = WaitQueue::new();
+    for i in 0..MAX_WAITERS {
+        assert!(queue.push(thread(i as u16)).is_some());
+    }
+    assert!(queue.push(thread(999)).is_none());
+}
+
+#[test]
+fn is_empty_after_drain() {
+    let mut queue = WaitQueue::new();
+    queue.push(thread(1)).unwrap();
+    queue.push(thread(2)).unwrap();
+    queue.pop();
+    queue.pop();
+    assert!(queue.is_empty());
+}
+
+// --- Endpoint tests ---
+
+#[test]
+fn new_endpoint_has_no_waiters() {
+    let ep = test_endpoint();
+    assert!(!ep.has_waiting_sender());
+    assert!(!ep.has_waiting_receiver());
+}
+
+#[test]
+fn sender_waits_then_dequeues() {
+    let mut ep = test_endpoint();
+    ep.enqueue_sender(thread(1)).unwrap();
+
+    assert!(ep.has_waiting_sender());
+    assert_eq!(ep.dequeue_sender(), Some(thread(1)));
+    assert!(!ep.has_waiting_sender());
+}
+
+#[test]
+fn receiver_waits_then_dequeues() {
+    let mut ep = test_endpoint();
+    ep.enqueue_receiver(thread(1)).unwrap();
+
+    assert!(ep.has_waiting_receiver());
+    assert_eq!(ep.dequeue_receiver(), Some(thread(1)));
+    assert!(!ep.has_waiting_receiver());
+}
+
+#[test]
+fn senders_and_receivers_are_independent() {
+    let mut ep = test_endpoint();
+    ep.enqueue_sender(thread(1)).unwrap();
+    ep.enqueue_receiver(thread(2)).unwrap();
+
+    assert_eq!(ep.dequeue_sender(), Some(thread(1)));
+    assert_eq!(ep.dequeue_receiver(), Some(thread(2)));
+}
+
+#[test]
+fn revoke_bumps_generation() {
+    let mut ep = test_endpoint();
+    let gen_before = *ep.generation();
+    ep.revoke();
+    let gen_after = *ep.generation();
+
+    assert!(!gen_before.is_valid_against(&gen_after));
+}
+
+#[test]
+fn rendezvous_sender_first() {
+    let mut ep = test_endpoint();
+
+    // sender arrives first, no receiver waiting
+    ep.enqueue_sender(thread(1)).unwrap();
+    assert!(!ep.has_waiting_receiver());
+
+    // receiver arrives, finds a sender
+    assert!(ep.has_waiting_sender());
+    let sender = ep.dequeue_sender().unwrap();
+    assert_eq!(sender, thread(1));
+}
+
+#[test]
+fn rendezvous_receiver_first() {
+    let mut ep = test_endpoint();
+
+    // receiver arrives first, no sender waiting
+    ep.enqueue_receiver(thread(1)).unwrap();
+    assert!(!ep.has_waiting_sender());
+
+    // sender arrives, finds a receiver
+    assert!(ep.has_waiting_receiver());
+    let receiver = ep.dequeue_receiver().unwrap();
+    assert_eq!(receiver, thread(1));
+}

crates/domain/src/endpoint/wait_queue.rs

@@ -0,0 +1,35 @@
+use types::id::ThreadId;
+
+pub const MAX_WAITERS: usize = 16;
+
+pub struct WaitQueue {
+    entries: [Option<ThreadId>; MAX_WAITERS],
+    count: u8,
+}
+
+impl WaitQueue {
+    pub fn new() -> Self {
+        Self {
+            entries: [None; MAX_WAITERS],
+            count: 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;
+        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
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.count == 0
+    }
+}

crates/domain/src/error.rs

@@ -0,0 +1,11 @@
+use types::{bounded::CapSlot, id::ProcessId, permission::Permission};
+
+#[derive(Debug)]
+pub enum KernelError {
+    InvalidSlot(CapSlot),
+    RevokedCapability(CapSlot),
+    PermissionDenied { slot: CapSlot, needed: Permission },
+    NoFreeSlot,
+    InvalidProcess(ProcessId),
+    WouldBlock,
+}

crates/domain/src/fault.rs

@@ -0,0 +1,10 @@
+use types::{address::VirtualAddress, bounded::CapSlot, permission::Permission};
+
+pub enum Fault {
+    CapabilityViolation { slot: CapSlot, needed: Permission },
+    InvalidCapability { slot: CapSlot },
+    RevokedCapability { slot: CapSlot },
+    InvalidSyscall,
+    MemoryFault { address: VirtualAddress },
+    IllegalInstruction,
+}

crates/domain/src/lib.rs

@@ -1,14 +1,12 @@
-pub fn add(left: u64, right: u64) -> u64 {
+#![no_std]
-    left + right
-}
 
-#[cfg(test)]
+pub mod capability;
-mod tests {
+pub mod endpoint;
-    use super::*;
+pub mod error;
-
+pub mod fault;
-    #[test]
+pub mod message;
-    fn it_works() {
+pub mod process;
-        let result = add(2, 2);
+pub mod resource;
-        assert_eq!(result, 4);
+pub mod scheduler;
-    }
+pub mod syscall;
-}
+pub mod thread;

crates/domain/src/message.rs

@@ -0,0 +1,9 @@
+use types::bounded::CapSlot;
+
+pub const MAX_MESSAGE_WORDS: usize = 4;
+pub const MAX_CAP_TRANSFERS: usize = 4;
+
+pub struct Message {
+    words: [usize; MAX_MESSAGE_WORDS],
+    caps: [Option<CapSlot>; MAX_CAP_TRANSFERS],
+}

crates/domain/src/process.rs

@@ -0,0 +1,15 @@
+use types::{
+    bounded::CapSlot,
+    id::{ProcessId, ThreadId},
+};
+
+use crate::capability::CapabilityTable;
+
+pub const MAX_THREADS_PER_PROCESS: usize = 4;
+
+pub struct Process {
+    id: ProcessId,
+    capabilities: CapabilityTable,
+    threads: [Option<ThreadId>; MAX_THREADS_PER_PROCESS],
+    fault_handler: Option<CapSlot>,
+}

crates/domain/src/resource.rs

@@ -0,0 +1,22 @@
+use types::{
+    address::VirtualAddress,
+    bounded::PageCount,
+    generation::Generation,
+    id::{EndpointId, IrqId, ProcessId, RegionId},
+};
+
+#[derive(Clone)]
+pub enum Resource {
+    Memory(RegionId),
+    Endpoint(EndpointId),
+    Process(ProcessId),
+    Interrupt(IrqId),
+    ProcessCreate,
+}
+
+pub struct MemoryRegion {
+    id: RegionId,
+    base: VirtualAddress,
+    size: PageCount,
+    generation: Generation,
+}

crates/domain/src/scheduler/mod.rs

@@ -0,0 +1,24 @@
+use types::{
+    bounded::Priority,
+    id::{CoreId, ThreadId},
+};
+
+pub mod per_core;
+pub mod priority_queue;
+
+#[cfg(test)]
+#[path = "tests.rs"]
+mod tests;
+
+pub enum SchedulerDecision {
+    Continue,
+    Preempt(ThreadId),
+}
+
+pub trait Scheduler {
+    fn add(&mut self, thread: ThreadId, priority: Priority, core: CoreId);
+    fn remove(&mut self, thread: ThreadId);
+    fn next(&mut self, core: CoreId) -> Option<ThreadId>;
+    fn tick(&mut self, core: CoreId, current: ThreadId) -> SchedulerDecision;
+    fn balance(&mut self);
+}

crates/domain/src/scheduler/per_core.rs

@@ -0,0 +1,52 @@
+use super::priority_queue::PriorityQueue;
+use types::bounded::Priority;
+use types::id::{CoreId, ThreadId};
+
+pub struct PerCoreScheduler {
+    core: CoreId,
+    queue: PriorityQueue,
+    current: Option<ThreadId>,
+}
+
+impl PerCoreScheduler {
+    pub fn new(core: CoreId) -> Self {
+        Self {
+            core,
+            queue: PriorityQueue::new(),
+            current: None,
+        }
+    }
+
+    pub fn core(&self) -> CoreId {
+        self.core
+    }
+
+    pub fn current(&self) -> Option<ThreadId> {
+        self.current
+    }
+
+    pub fn add(&mut self, thread: ThreadId, priority: Priority) {
+        self.queue.add(thread, priority);
+    }
+
+    pub fn remove(&mut self, thread: ThreadId, priority: Priority) {
+        self.queue.remove(thread, priority);
+    }
+
+    pub fn pick_next(&mut self) -> Option<ThreadId> {
+        let (thread, _priority) = self.queue.next()?;
+        self.current = Some(thread);
+        Some(thread)
+    }
+
+    pub fn clear_current(&mut self) {
+        self.current = None;
+    }
+
+    pub fn len(&self) -> usize {
+        // for load balancing — count of ready threads
+        // could track this incrementally instead of computing
+        // but for now, bitmap popcount works
+        self.queue.bitmap().count_ones() as usize
+    }
+}

crates/domain/src/scheduler/priority_queue.rs

@@ -0,0 +1,108 @@
+use types::bounded::Priority;
+use types::id::ThreadId;
+
+const NUM_PRIORITIES: usize = 32;
+const MAX_THREADS_PER_PRIORITY: usize = 16;
+
+struct RunList {
+    threads: [Option<ThreadId>; MAX_THREADS_PER_PRIORITY],
+    head: usize,
+    tail: usize,
+    count: 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
+    }
+}
+
+pub struct PriorityQueue {
+    queues: [RunList; NUM_PRIORITIES],
+    bitmap: u32,
+}
+
+impl PriorityQueue {
+    pub fn new() -> Self {
+        Self {
+            queues: core::array::from_fn(|_| RunList::new()),
+            bitmap: 0,
+        }
+    }
+
+    pub fn bitmap(&self) -> u32 {
+        self.bitmap
+    }
+
+    pub fn add(&mut self, thread: ThreadId, priority: Priority) {
+        let idx = priority.value() as usize;
+        self.queues[idx].push(thread);
+        self.bitmap |= 1 << idx;
+    }
+
+    pub fn remove(&mut self, thread: ThreadId, priority: Priority) {
+        let idx = priority.value() as usize;
+        self.queues[idx].remove(thread);
+        if self.queues[idx].is_empty() {
+            self.bitmap &= !(1 << idx);
+        }
+    }
+
+    pub fn next(&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).unwrap()))
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.bitmap == 0
+    }
+}

crates/domain/src/scheduler/tests.rs

@@ -0,0 +1,124 @@
+use super::per_core::PerCoreScheduler;
+use super::priority_queue::PriorityQueue;
+use types::bounded::Priority;
+use types::id::{CoreId, ThreadId};
+
+fn thread(id: u16) -> ThreadId {
+    ThreadId::from_raw(id)
+}
+
+fn prio(value: u8) -> Priority {
+    Priority::new(value).unwrap()
+}
+
+// --- PriorityQueue tests ---
+
+#[test]
+fn empty_queue_returns_none() {
+    let mut q = PriorityQueue::new();
+    assert!(q.next().is_none());
+    assert!(q.is_empty());
+}
+
+#[test]
+fn single_thread() {
+    let mut q = PriorityQueue::new();
+    q.add(thread(1), prio(10));
+
+    let (t, p) = q.next().unwrap();
+    assert_eq!(t, thread(1));
+    assert_eq!(p, prio(10));
+}
+
+#[test]
+fn highest_priority_runs_first() {
+    let mut q = PriorityQueue::new();
+    q.add(thread(1), prio(5));
+    q.add(thread(2), prio(20));
+    q.add(thread(3), prio(10));
+
+    let (t, _) = q.next().unwrap();
+    assert_eq!(t, thread(2));
+}
+
+#[test]
+fn same_priority_is_fifo() {
+    let mut q = PriorityQueue::new();
+    q.add(thread(1), prio(10));
+    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());
+}
+
+#[test]
+fn remove_thread() {
+    let mut q = PriorityQueue::new();
+    q.add(thread(1), prio(10));
+    q.add(thread(2), prio(10));
+
+    q.remove(thread(1), prio(10));
+
+    let (t, _) = q.next().unwrap();
+    assert_eq!(t, thread(2));
+    assert!(q.next().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));
+
+    assert!(q.is_empty());
+}
+
+#[test]
+fn drain_all_priorities() {
+    let mut q = PriorityQueue::new();
+    q.add(thread(1), prio(0));
+    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!(q.is_empty());
+}
+
+// --- PerCoreScheduler tests ---
+
+#[test]
+fn new_core_has_no_current() {
+    let core = PerCoreScheduler::new(CoreId::from_raw(0));
+    assert!(core.current().is_none());
+}
+
+#[test]
+fn pick_next_sets_current() {
+    let mut core = PerCoreScheduler::new(CoreId::from_raw(0));
+    core.add(thread(1), prio(10));
+
+    let picked = core.pick_next().unwrap();
+    assert_eq!(picked, thread(1));
+    assert_eq!(core.current(), Some(thread(1)));
+}
+
+#[test]
+fn pick_next_on_empty_returns_none() {
+    let mut core = PerCoreScheduler::new(CoreId::from_raw(0));
+    assert!(core.pick_next().is_none());
+}
+
+#[test]
+fn clear_current() {
+    let mut core = PerCoreScheduler::new(CoreId::from_raw(0));
+    core.add(thread(1), prio(10));
+    core.pick_next();
+
+    core.clear_current();
+    assert!(core.current().is_none());
+}

crates/domain/src/syscall.rs

@@ -0,0 +1,64 @@
+use types::{
+    address::{DataRef, EntryPoint, StackPointer, VirtualAddress},
+    bounded::{CapSlot, PageCount},
+    permission::PermissionSet,
+};
+
+use crate::message::Message;
+
+pub struct WaitSet {
+    endpoints: [Option<CapSlot>; 4],
+    interrupts: [Option<CapSlot>; 4],
+}
+
+pub enum WakeReason {
+    MessageReady(CapSlot),
+    InterruptFired(CapSlot),
+}
+
+pub enum Syscall {
+    Send {
+        endpoint: CapSlot,
+        message: Message,
+    },
+    Receive {
+        endpoint: CapSlot,
+    },
+    Delegate {
+        slot: CapSlot,
+        to_endpoint: CapSlot,
+        permissions: PermissionSet,
+    },
+    WaitForInterrupt {
+        irq: CapSlot,
+    },
+    AcknowledgeInterrupt {
+        irq: CapSlot,
+    },
+    WaitAny {
+        sources: WaitSet,
+    },
+    CreateProcess {
+        create_cap: CapSlot,
+        image: DataRef,
+    },
+    Kill {
+        process: CapSlot,
+    },
+    SpawnThread {
+        entry: EntryPoint,
+        stack: StackPointer,
+    },
+    ExitThread,
+    RequestPages {
+        count: PageCount,
+    },
+    ReleasePages {
+        addr: VirtualAddress,
+        count: PageCount,
+    },
+    GetTime,
+    GetProcessId,
+    Yield,
+    Exit,
+}

crates/domain/src/thread.rs

@@ -0,0 +1,33 @@
+use types::{
+    bounded::{CapSlot, Priority},
+    id::{CoreId, ProcessId, ThreadId},
+    time::TimeSlice,
+};
+
+pub struct Thread {
+    id: ThreadId,
+    process: ProcessId,
+    state: ThreadState,
+    saved_context: SavedContext,
+    priority: Priority,
+    time_slice: TimeSlice,
+    core_affinity: Option<CoreId>,
+}
+
+pub enum ThreadState {
+    Ready,
+    Running(CoreId),
+    Blocked(BlockReason),
+    Dead,
+}
+
+pub struct SavedContext {
+    registers: [usize; 32],
+}
+
+pub enum BlockReason {
+    Sending(CapSlot),
+    Receiving(CapSlot),
+    WaitingForInterrupt(CapSlot),
+    WaitingAny,
+}

crates/platform/Cargo.toml

@@ -4,3 +4,5 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+types = { workspace = true }
+domain = { workspace = true }

crates/platform/src/lib.rs

@@ -1,14 +1,23 @@
-pub fn add(left: u64, right: u64) -> u64 {
+#![no_std]
-    left + right
-}
 
-#[cfg(test)]
+use domain::{resource::MemoryRegion, thread::SavedContext};
-mod tests {
+use types::{
-    use super::*;
+    address::{EntryPoint, StackPointer},
+    id::{CoreId, IrqId, ProcessId},
+    time::{Ticks, TimerDuration},
+};
 
-    #[test]
+pub trait PlatformContext: Copy + Default {}
-    fn it_works() {
+
-        let result = add(2, 2);
+pub trait Platform {
-        assert_eq!(result, 4);
+    fn configure_protection(&mut self, process: ProcessId, regions: &[MemoryRegion]);
-    }
+    fn context_switch(&mut self, from: &mut SavedContext, to: &SavedContext);
+    fn enable_user_mode(&mut self, entry: EntryPoint, stack: StackPointer) -> !;
+    fn set_timer(&mut self, duration: TimerDuration);
+    fn current_ticks(&self) -> Ticks;
+    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;
+    fn num_cores(&self) -> u8;
 }

crates/types/src/address.rs

@@ -3,3 +3,12 @@ pub struct EntryPoint(usize);
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct StackPointer(usize);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct VirtualAddress(usize);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct DataRef {
+    addr: VirtualAddress,
+    len: usize,
+}

crates/types/src/bounded.rs

@@ -2,3 +2,4 @@ use crate::macros::bounded;
 
 bounded!(CapSlot, u8, 0, 63);
 bounded!(Priority, u8, 0, 31);
+bounded!(PageCount, u16, 1, 1024);

crates/types/src/time.rs

@@ -9,3 +9,27 @@ impl Ticks {
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct TimerDuration(u32);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct TimeSlice {
+    remaining: u32,
+    quantum: u32,
+}
+
+impl TimeSlice {
+    pub fn new(quantum: u32) -> Self {
+        Self {
+            remaining: quantum,
+            quantum,
+        }
+    }
+
+    pub fn tick(&mut self) -> bool {
+        self.remaining = self.remaining.saturating_sub(1);
+        self.remaining == 0
+    }
+
+    pub fn reset(&mut self) {
+        self.remaining = self.quantum;
+    }
+}