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Re-organize the source tree as a monorepo mirroring the FHS

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The source layout now mirrors the runtime filesystem hierarchy
(docs/danos-file-system-hierarchy-FSH.md): what lives under system/ in the
source is what a running danos represents under /system. Each service and
driver is a sub-project directory that is its own Zig module — cross-project
references go by module name, never by a path into another project's files.

Moves (all git mv, history preserved):
- src/            -> system/            (danos internals; the self-representation)
    root.zig      -> danos.zig          (the kernel<->user contract module)
    kernel/arch/  -> kernel/architecture/   (arch -> architecture)
    device/       -> devices/           (what /system/devices reflects)
    boot/         -> /boot              (the loaders, top level)
- sbin/           -> split by role:
    init, vfs     -> system/services/<name>/<name>.zig
    hpetd, busd   -> system/drivers/<name>/<name>.zig
    vfs-test      -> system/services/vfs/vfs-test.zig  (inside the vfs project)
- lib/            -> library/runtime/   (room for other libraries beside runtime)

The VFS wire protocol becomes its own module, system/services/vfs/protocol.zig
("vfs-protocol"): the vfs sub-project exposes its interface, and the runtime's
file layer imports it by name. First instance of the "protocol module" pattern
(docs/driver-model.md); usb/block will expose theirs the same way.

Also: fix a naming-standard violation in the protocol — Op -> Operation (and
req -> request, _pad -> _padding). Docs updated: /system/services added to the
FHS doc, a repository-layout section added to the docs index, and stale source
paths swept across comments and docs.

Runtime boot paths are unchanged (the bootloader still loads /sbin/init);
aligning the runtime filesystem to the FHS is a separate follow-up. Suite 35/35
plus host tests green.
This commit is contained in:
Daniel Samson
2026-07-10 12:55:56 +01:00
parent 15b70856c9
commit 8754d4e46a
83 changed files with 334 additions and 177 deletions
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docs/README.md
+48 -18
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@@ -116,27 +116,57 @@ other over IPC **endpoints** ([ipc.md](ipc.md)), and a **[driver](drivers.md)**
a device, maps its registers, and sleeps until the hardware interrupts it — which is
the whole reason for the arrangement ([vision.md](vision.md)).
## Repository layout
danos is a **monorepo of sub-projects**. Each service or driver is a directory that is
its own Zig module — it can hold as many files as it needs, and other sub-projects
reach it *by module name*, never by a path into its files. The source tree deliberately
**mirrors the runtime FHS** ([danos-file-system-hierarchy-FSH.md](danos-file-system-hierarchy-FSH.md)):
what you see under `system/` in the source is what a running danos represents under
`/system`.
```
system/ → /system danos's own internals (the self-representation)
danos.zig the kernel↔user ABI contract (the `danos` module)
parameters.zig initrd.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/)
drivers/ hpetd/ busd/ one sub-project per driver → /system/drivers
services/ init/ vfs/ system servers → /system/services (vfs/ holds
vfs.zig, vfs-test.zig, protocol.zig)
library/ → /lib the runtime library (the stable application ABI)
boot/ → /boot the loaders
tools/ test/ host-side build + QEMU test harness
```
A sub-project exposes its **public interface as a module**: `system/services/vfs/` owns
the VFS wire protocol (`protocol.zig`, the `vfs-protocol` module), which the runtime's
file layer imports by name. `usb`/`block` drivers will expose their protocols the same
way.
## Source map
| Area | Code |
|------|------|
| Boot methods (one per way of booting the kernel) | `src/boot/` — `efi.zig` (UEFI) → `BOOTX64.efi` |
| Kernel entry, panic, bring-up | `src/kernel/main.zig` |
| Shared loader↔kernel contract (`BootInfo`, `Framebuffer`, `MemoryMap`, `Syscall`, ABI) | `src/root.zig` |
| Physical frame allocator | `src/kernel/pmm.zig` |
| Kernel heap (`std.mem.Allocator`) | `src/kernel/heap.zig` |
| Scheduler (fixed-priority preemptive; blocking, wait queues) | `src/kernel/scheduler.zig` |
| Big kernel lock + interrupt-safe critical sections | `src/kernel/sync.zig` |
| IPC channels between kernel threads (message passing) | `src/kernel/ipc.zig` |
| IPC endpoints: cross-address-space call/reply, handles, notifications | `src/kernel/ipc-synchronous.zig` |
| User processes: ELF loading, address spaces, the syscall table | `src/kernel/process.zig` |
| Device tree + claim capability + `device_register` containment | `src/kernel/device-service.zig` |
| IRQ-as-IPC: routing a device interrupt to a driver's endpoint | `src/kernel/irq.zig` |
| Hardware discovery (ACPI/device tree) behind one neutral device model | `src/device/` |
| Framebuffer text console (mirrors to serial) | `src/kernel/console.zig` |
| In-kernel test cases | `src/kernel/tests.zig` |
| Arch-specific kernel code (`halt`, GDT/IDT/TSS, exception + interrupt stubs, page tables, APIC/IO-APIC/timer, serial, linker script) | `src/kernel/arch/x86_64/` |
| User runtime library (`rt`): syscalls, heap, stdio, IPC, device access | `lib/` |
| User-space programs shipped in the initrd (`init`, `vfs`, `hpetd` leaf driver, `busd` bus driver) | `sbin/` |
| Boot methods (one per way of booting the kernel) | `boot/` — `efi.zig` (UEFI) → `BOOTX64.efi` |
| Kernel entry, panic, bring-up | `system/kernel/main.zig` |
| Shared loader↔kernel contract (`BootInfo`, `Framebuffer`, `MemoryMap`, `Syscall`, ABI) | `system/danos.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` |
| Big kernel lock + interrupt-safe critical sections | `system/kernel/sync.zig` |
| IPC channels between kernel threads (message passing) | `system/kernel/ipc.zig` |
| IPC endpoints: cross-address-space call/reply, handles, notifications | `system/kernel/ipc-synchronous.zig` |
| User processes: ELF loading, address spaces, the syscall table | `system/kernel/process.zig` |
| Device tree + claim capability + `device_register` containment | `system/kernel/device-service.zig` |
| IRQ-as-IPC: routing a device interrupt to a driver's endpoint | `system/kernel/irq.zig` |
| Hardware discovery (ACPI/device tree) behind one neutral device model | `system/devices/` |
| Framebuffer text console (mirrors to serial) | `system/kernel/console.zig` |
| In-kernel test cases | `system/kernel/tests.zig` |
| Arch-specific kernel code (`halt`, GDT/IDT/TSS, exception + interrupt stubs, page tables, APIC/IO-APIC/timer, serial, linker script) | `system/kernel/architecture/x86_64/` |
| Runtime library (`runtime`): syscall wrappers, heap, stdio, IPC, device access — the stable application ABI | `library/runtime/` |
| System services (init, the VFS server + its `protocol` module) | `system/services/` |
| Device drivers, one sub-project each (`hpetd` leaf driver, `busd` bus driver) | `system/drivers/` |
| Build + `run-x86-64` (QEMU/OVMF) | `build.zig` |
| QEMU integration test harness | `test/qemu_test.py` |