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Split the system contract into boot-handoff / abi / device-abi

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The `system` module (formerly `danos`) had become a grab-bag: it held the
loader<->kernel handoff *and* the kernel<->user ABI *and* the device wire types, in
one module three different audiences imported. Usage proved the seam — the
bootloader never touched the syscall/device ABI, and user space never touched the
boot handoff — so split it by audience, one module per contract:

  system/boot-handoff.zig       loader <-> kernel: BootInformation, Framebuffer,
                                MemoryMap, the VM layout + physicalToVirtual, kernel_abi
  system/abi.zig                kernel <-> user, core: SystemCall, mmap prot flags,
                                page_size, notify_badge_bit, ServiceId
  system/devices/device-abi.zig kernel <-> user, devices: DeviceDescriptor,
                                DeviceClass, ResourceDescriptor, ResourceKind, ...

device-abi is the devices sub-project's public interface, exposed as its own module
the way vfs exposes vfs-protocol — importable by user space, unlike the
kernel-internal device model it also feeds. That collapses a real duplication:
DeviceClass and ResourceKind were defined twice (device-model.zig and the contract,
kept "in sync by hand"); device-model now re-exports them from device-abi, so the
enum a driver matches on and the one the kernel classifies with are one type.

Each import now declares which contract it speaks: the bootloader imports only
boot-handoff; a driver only abi + device-abi (via the runtime); the kernel all
three. This also retires the `system` / `runtime.system` name overlap. page_size
lands in abi (it's part of the mmap contract user space aligns to); the bootloader
keeps its own local 4 KiB constant so it depends on nothing but the handoff.

All 21 importers rewired, docs updated to keep /system mapping to source. Build,
host tests, and the QEMU suite (36/36) all green.
This commit is contained in:
Daniel Samson
2026-07-10 18:08:51 +01:00
parent 47610e8ee2
commit be81394be3
37 changed files with 395 additions and 337 deletions
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docs/README.md
+6 -2
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@@ -146,11 +146,13 @@ A sub-project's extra files are reached through the module, never as separate pa
```
system/ → /system danos's own internals (the self-representation)
system.zig the kernel↔user ABI contract (the `system` module)
boot-handoff.zig the loader↔kernel contract (the `boot-handoff` module)
abi.zig the core kernel↔user ABI (the `abi` module)
parameters.zig initial-ramdisk.zig shared contracts
kernel/ IPC, memory, scheduling, the private syscall dispatch
architecture/x86_64/ the `architecture` module (never named by generic code)
devices/ the device model /system/devices reflects (+ aml/)
device-abi.zig the device wire types (the `device-abi` module)
drivers/ hpet/ bus/ one sub-project per driver → /system/drivers
services/ init/ vfs/ device-manager/ system servers → /system/services (vfs/ holds
vfs.zig, vfs-test.zig, protocol.zig)
@@ -177,7 +179,9 @@ appears in the private-ABI path.
|------|------|
| Boot methods (one per way of booting the kernel) | `boot/` — `efi.zig` (UEFI) → `BOOTX64.efi` |
| Kernel entry, panic, bring-up | `system/kernel/kernel.zig` |
| Shared loader↔kernel contract (`BootInfo`, `Framebuffer`, `MemoryMap`, `Syscall`, ABI) | `system/system.zig` |
| Loader↔kernel handoff (`BootInfo`, `Framebuffer`, `MemoryMap`, VM layout) | `system/boot-handoff.zig` |
| Core kernel↔user ABI (`SystemCall`, mmap prot flags, `page_size`) | `system/abi.zig` |
| Device wire types (`DeviceDescriptor`, `DeviceClass`, …) | `system/devices/device-abi.zig` |
| Physical frame allocator | `system/kernel/pmm.zig` |
| Kernel heap (`std.mem.Allocator`) | `system/kernel/heap.zig` |
| Scheduler (fixed-priority preemptive; blocking, wait queues) | `system/kernel/scheduler.zig` |