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.
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.
Start the user-space driver track (VFS + IPC + heap). This lays the
process/syscall foundation the runtime heap will grow on.
- Rename usermode.zig -> process.zig; drop the retired hello/ping blob and
its `user` test (subsumed by the real /sbin/init exerciser). Keep the
isolation-proof pf blob and the user-pf test.
- Add danos.Syscall as the single source of truth for syscall numbers, shared
by the kernel dispatcher and (later) the user runtime lib. Dispatch on the
enum. New calls: 1=yield, 4=mmap, 5=munmap. Widen debug_write's bounds
check to the whole user low half so heap buffers are writable.
- mmap grants zeroed RW+NX pages from a per-process bump arena
(Task.heap_next, PML4[224] above image+stack); munmap frees the frames.
Add paging.translateIn / unmapInto (+ arch.translate / unmapUserPageInto)
as the primitives munmap and future cross-AS copies need.
- New `usermem` test: grant three pages into a fresh AS, translate them,
release via the munmap path, tear down, and assert no frames leak.
Suite 28/28 (user -> usermem).
init is now a real scheduled ring-3 process: it prints a heartbeat and
sleeps, forever. The kernel spawns it at boot via spawnProcess (its own
address space, preemption on) and the boot context drops to idle — the
system's steady state is "kernel idle, init alive in ring 3", beating
~1 Hz. Adds the sleep(ms) syscall. The init/process tests are reshaped
around the heartbeat (repeated syscalls, still-alive, two concurrent
processes on distinct address spaces). Pins init to LLD and folds the
.large code model's .ltext/.lrodata/.ldata into the linker script so its
code segment is R+X. Removes the now-dead borrowed-thread ELF loader
(runInitElf); spawnProcess is the one path. Docs updated. Suite 28/28.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Per-core MSR setup (EFER.SCE, STAR, LSTAR, SFMASK) enables syscall; the
GDT layout was already chosen so sysret lands on CS 0x23 / SS 0x1B. A new
syscall_entry stub swaps in the kernel GS, switches to the task's kernel
stack via the per-CPU block, builds a CpuState frame identical to the
interrupt path's, and reuses interruptDispatch (vector 128) — then
sysretq back. enter_user now also publishes kernel_rsp so the borrowed
path's syscalls land on a good stack. /sbin/init uses the `syscall`
instruction. int 0x80 stays for the test blobs. Suite 27/27.
(Noted in the stub: sysretq #GPs in ring 0 on a non-canonical return
RIP — a hardening item once untrusted user code exists.)
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Ring 3 works: user GDT descriptors (sysret-ready layout), TSS.rsp0,
U/S-bit user mappings (W^X preserved), an int 0x80 syscall gate with a
mutable trap frame, and a setjmp-style enter/exit path. /sbin/init is a
real freestanding Zig binary built from sbin/, shipped on the ESP,
loaded by the bootloader (BootInfo.init_base/len), validated and mapped
by an in-kernel user-ELF loader, and run at CPL 3 — syscalls: exit,
ping, write. Tests: user, user-pf (U/S isolation proof, error code
0x5), init. Suite 27/27.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Daniel Samson
