feat(kernel): SystemControl cap for halt, board device table + boot caps to init, RegionAddress syscall, idle loop services irqs

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)
+    }
+}