Two driver-model milestones plus a tree-wide naming pass. Suite 35/35
(QEMU) + host tests green.
M11 — IRQ-as-IPC. A ring-3 driver now sleeps until its device interrupts
it. New src/kernel/irq.zig: per-GSI endpoint bindings, comptime per-vector
trampolines, dispatch = mask GSI -> LAPIC EOI -> notifyLocked, all under one
lock region. irq_bind/irq_ack syscalls, gated by the device claim like
mmio_map. interruptDispatch no longer EOIs — each handler owns its EOI,
because a level line must be masked before it is acknowledged (irq_ack is
the unmask). Bindings are keyed on the owning task and released on exit
(a shared endpoint's siblings survive). hpetd rewritten interrupt-driven.
Tests: hpet (rewritten, reads back the I/O APIC routing) and irqfree.
M12 — bus drivers. DeviceDesc gains a parent, making the device table a
tree. dev_register (device_register) lets a process publish children below
a device it claimed; the kernel enforces resource containment (a child's
resources must nest in its parent's), so a descriptor can't fabricate a
window over kernel RAM. Descriptor copied in via copyFromUser (physmap
walk — an unmapped user pointer fails the call instead of faulting the
kernel). Per-parent child cap bounds table exhaustion. sbin/busd.zig is a
worked bus driver. Test: bus.
Naming — per docs/coding-standards.md: non-acronym abbreviations spelled
out (message, descriptor, device_service, scheduler, runtime, physical,
interpreter, ...); acronyms kept (IPC, MMIO, DMA, HCD, ...); files are
kebab-case (ipc-synchronous.zig, device-service.zig, vfs-protocol.zig, ...).
Exceptions: POSIX/C ABI names and Zig idioms (init/len/ptr) kept. Module
collisions resolved by specific naming (config -> parameters, device.zig
alias -> device_model). AML op/Op disambiguated: op = opcode, Op =
operation; per-opcode parse handlers renamed opX -> parseX.
New driver docs: drivers.md, driver-model.md (bus/class/HCD shapes + the
proposed M13–M16 ABI), coding-standards.md.
The payoff milestone: files are served by a user-space process, reached over
IPC — the kernel never sees a path or an fd.
- lib/vfs_proto.zig: the VFS wire protocol (Op, Request/Reply fixed header +
inline payload, Stat), shared by client and server; one message <= MSG_MAX.
- lib/ipc.zig: replyWait() — the server-side dual-return stub (length in rax,
badge in rdx via a "+{rdx}" read-write operand), deferred from M7.
- sbin/vfs.zig: the real VFS server — an in-heap ramfs (open creates a node)
with an IPC_ReplyWait dispatch loop serving open/read/write/stat/close.
Registers its endpoint under the well-known vfs id at startup.
- lib/unistd.zig: POSIX-style client API in rt — a per-process fd table +
open/close/read/write/lseek/stat, each an IPC_Call to the VFS. The kernel
knows nothing of fds; the table lives here.
- lib/stdio.zig: C stdio over unistd — FILE + fopen/fclose/fread/fwrite/
fseek/ftell/rewind/feof/ferror/fputs/fputc/fgetc (unbuffered for now).
- sbin/vfstest.zig: a client that opens/writes/seeks/reads a file and only
heartbeats "vfstest: ok" if the round trip matched. Packed in the initrd.
- New `vfs` test drives it end to end. initrd test relaxed to generic
liveness. Suite 31/31.
The microkernel message backbone the VFS server and drivers will ride on.
- src/kernel/ipc_sync.zig: Endpoint (sender FIFO threaded via Task.next +
a recv WaitQueue for servers + a small notification ring). call() (client
sends, wakes a server, blocks) and replyWait() (server replies to the held
caller, then receives the next). Reply routing keys on Task.ipc_client —
synchronous IPC owes one reply at a time. Payloads copy frame-to-frame
through the physmap (copyAcross on arch.translate, added in M5); an unmapped
page fails the copy instead of #PF-ing. MSG_MAX 256.
- Bootstrap naming: an integer name registry (danos.ServiceId, vfs=1) with
create_endpoint / ipc_register / ipc_lookup — any process finds a server
without threading a handle through spawn.
- notifyFromIsr(): ISR-safe async wake (badge with the high bit set), the
hook M10's IRQ-as-message needs. Unused/untested until then.
- Task gains handles[16] (opaque *Endpoint, to avoid a sched<->ipc import
cycle) + ipc_client/send/reply/status fields; sched gains
blockCurrentLocked/readyLocked; arch gains setSyscallResult2 (rdx badge).
- Syscalls 6..10 wired in process.zig; exit() now drops the caller's endpoint
refs. lib/ipc.zig: user-side createEndpoint/register/lookup/call
(server-side replyWait lands with the first server in M9).
- New `ipc-call` test: two kernel tasks ping-pong 100 calls, every reply
request+1. Suite 29/29.
Add lib/ — the shared user-space runtime every user binary links against
(init now, servers/drivers later): syscall wrappers, the heap, IPC stub,
and the process start shim.
- lib/heap.zig: the kernel first-fit free-list ported to user space, grown
via the mmap syscall instead of pmm+mapPage. Dual API over one global free
list: extern "C" malloc/free/calloc/realloc (C ABI for future C code) and a
std.mem.Allocator adapter (with in-place resize) for Zig std containers.
- lib/syscall.zig + sys.zig: raw syscall0..5 (arg3 in r10) and typed
yield/write/sleep/exit/mmap/munmap over danos.Syscall.
- lib/start.zig: naked _start -> rt_start -> root.main() (SysV realign via
call), panic -> exit(127).
- lib/user.ld: the user link script, moved from sbin/linker.ld (shared by all
user binaries).
- build.zig: register the `rt` module; add an addUserBinary() helper that is
the one recipe for every user binary (freestanding, .large, use_lld,
user.ld, image_base), replacing the bespoke init block.
- sbin/init.zig: migrated onto rt; drops its hand-rolled syscall2/shims. Now
proves the heap (alloc -> write from a heap pointer -> free) before the
heartbeat loop. Serial shows "init: heap ok". Suite 28/28.
Daniel Samson