Ring 3 still has no direct in/out (no TSS I/O bitmap, IOPL never raised — a #GP), but a
driver no longer needs it: io_read(device_id, resource_index, offset, width) and
io_write(..., value) grant port access the same way mmio_map grants memory. The claim
plus the device's discovered io_port resource are the capability — resolveIoPort checks
the device is claimed by the caller, the resource is io_port, and [offset, offset+width)
stays inside it, then issues the in/out via architecture.pioRead/pioWrite. So a PS/2 or
16550 driver is now writable; the low-rate legacy hardware that needs port I/O is fine
with a syscall per access. io_port resources were recorded by discovery and ignored —
now they're used. Runtime: device.ioRead/ioWrite.
New `ioport` test claims QEMU's PS/2 controller (io_port 0x64, discovered via ACPI) and
checks the gate admits an in-range access, refuses over-wide / out-of-range / unclaimed,
and that the kernel actually reads the status port (0x1c). Suite 41/41 plus host tests.
Docs refreshed for the whole M13-M16 + port-I/O reality: drivers.md "Limits" no longer
lists port I/O, DMA memory, or barriers as missing (they exist) and its "what's next"
reflects that; the FSH doc's character-device and block-device sections are corrected
("cannot host a block driver at all" is no longer true — writable now, not yet memory-
safe pending IOMMU enforcement); device-interrupts.md unblocks the keyboard and narrows
the interrupt gap to MSI-X.
Detect the IOMMU: discovery now parses the ACPI DMAR table, finds the first VT-d
DMA-remapping unit (DRHD), maps its register block, and records its version and
capabilities (iommu_present/base/version/capabilities in the platform info). On QEMU's
emulated intel-iommu this reads back a real unit (base 0xfed90000, version 1.0).
This is detection only, and deliberately so. A full VT-d bring-up — per-device
translation domains that confine a driver's DMA to the buffers it dma_alloc'd — is the
real device-side safety guarantee, but it cannot be verified without a DMA-capable
device driver (none exist yet) and QEMU's intel-iommu to fault against. Writing that
enforcement now would be a large body of unverifiable page-table code; it belongs with
the first DMA driver, which is both the natural order and the only way to test it. Until
then the caveat stands in full: device_claim on a DMA-capable device is still equivalent
to granting ring 0. The docs say so plainly.
New `iommu` test (harness boots it with -device intel-iommu via a new per-case qemu_extra
hook) confirms the DMAR is parsed and the unit's registers read. Suite 40/40 plus host
tests.
Two parts, both blockers for real PCI drivers.
ECAM config space per function: enumeratePci now gives every pci_device its own 4 KiB
configuration window as resource 0. A claimed PCI driver mmio_maps that to reach its
command register, BARs, and — the point — its capability list (MSI/MSI-X, PCIe extended
caps), with no new syscall. Verified in the discovery test (QEMU q35's functions each
carry it).
MSI: msi_bind(device_id, endpoint) -> address (rax), data (rdx) allocates a per-device
edge-triggered vector, binds it to the endpoint, and returns the (address, data) the
driver programs into its own MSI capability. Unlike irq_bind there's no GSI, no I/O APIC
entry, no sharing, and no ack cycle — dispatch recognises an MSI vector (vector_gsi ==
none, msi_bound set), EOIs, and notifies. Owner-keyed release drops the binding on exit.
Legacy INTx (_PRT parsing + shared lines) is deliberately skipped; MSI is the real
answer.
QEMU's HPET has no MSI, so the new `msi` test proves the vector-routing path with a
self-IPI (new apic.selfIpi) standing in for the device's MSI write: bind a vector,
fire it, the bound endpoint is notified. The msi_bind syscall wraps irq.msiBind with
the claim check and lands its first real use with the first PCI driver. Suite 39/39
plus host tests.
An HCD programs a bus-master engine: it needs a descriptor ring that is physically
contiguous, at a physical address it knows, uncacheable, and pinned. mmap gives none
of those. Add dma_alloc(len, flags) -> vaddr (rax), paddr (rdx) and dma_free(vaddr,
len): grant contiguous, zeroed, pinned, strong-uncacheable memory in a per-process DMA
arena (PML4[228]) and hand back both addresses.
Pieces: pmm.allocContiguous(count, max_phys) finds a run of contiguous free frames
below a cap (dma_below_4g for 32-bit engines); mapUserDmaInto maps them uncacheable
(PCD|PWT) but WITHOUT device_grant, so unlike an MMIO grant these frames are real RAM
and freeSubtree returns them on teardown — a driver that dies leaks nothing. dma_free
is bounded to the DMA arena so it can never unmap the caller's stack/heap/MMIO.
dma_write_combining is accepted but falls back to coherent (WC needs PAT programming).
Runtime: runtime.dma.alloc/free (a two-return-value stub, like replyWait). New `dma`
kernel test drives the mechanism directly — contiguity, the below-4G cap, coherent
mapping, and reclaim-on-teardown (no leak). The thin syscall wrappers follow the tested
mmap/mmio_map shape and land their first real use with the first DMA driver. Suite
38/38 plus host tests.
ipc_call and ipc_reply_wait grow a `send_cap` argument (r9) and a `received_cap`
return (r8): an endpoint travels alongside a message, installed into the receiver's
handle table. The transfer is a share, not a move — the endpoint's refcount is bumped
and the sender keeps its handle. If the receiver's table is full the call fails
-ENOSPC and the message is NOT delivered (a half-delivered capability is worse than a
failed send); a bad handle fails -EBADF. Both directions carry a cap: a client's call
hands one to the server (seen in the server's replyWait), and the server's reply hands
one back (seen in the client's call return).
This is the "open" primitive the driver model was blocked on: a bus driver mints a
per-device endpoint and hands it to a class driver, giving it a private channel to one
device without the 8-slot global name registry.
Kernel: shareCapability in ipc-synchronous.zig at both copy points; new
setSystemCallResult3 (r8, saved/restored by the syscall stub); Task gains
ipc_send_cap / ipc_received_cap. Runtime: callCap + Reply, replyWait gains send_cap
and Received.cap; plain call/replyWait delegate with no_cap. New abi.no_cap.
New ipc-cap test (two kernel tasks exercise both directions, each verifying the
endpoint it received is the same object shared, refcount bumped to 2). No class driver
consumes callCap yet — it lands with the first one. Suite 37/37 plus host tests.
The reorg moved user binaries under /system (init -> /system/services/init,
drivers -> /system/drivers/<name>, vfs-test -> /system/services/vfs/vfs-test), but
many comments and log strings still named the old /sbin/ home. Retarget them all:
kernel/loader/test comments and the two boot log lines, plus vision.md and the
driver-model.md proposed tree (also dropped the stale `d` suffixes and rt->runtime
there). The initial-ramdisk spawn log no longer fakes a /sbin/ prefix, since those
binaries live in different homes (services vs drivers).
Left the FSH design doc's /sbin and /lib rows alone — whether /sbin stays a
directory at all is a design call for its owner, not a stale-comment fix.
The device manager is the ring-3 process that turns the device tree into a running
system — the udev-analog. It is mechanism-vs-policy done right: the kernel
enumerates the hardware and enforces the claim capability; this decides which
driver serves which device, using no special privilege (the same device_enumerate
any process could call).
This first increment does the discovery + matching half: system/services/
device-manager enumerates /system/devices, matches each device to a driver by
class (a small static policy table), and logs the decision — finding the HPET
(a timer) and deciding `hpet` serves it. It does not spawn yet: spawning needs a
`system_spawn` system call (the kernel spawns every initial-ramdisk binary in a
loop today), which is the next increment. New `device-manager` test; suite 36/36
plus host tests.
`zig build` now installs into a FHS-shaped zig-out that *is* the danos filesystem
and the boot volume — no more zig-out/bin or a separate esp/:
zig-out/EFI/BOOT/BOOTX64.efi (firmware entry; UEFI fixes this path)
zig-out/boot/initial-ramdisk.img
zig-out/system/kernel (the kernel binary)
zig-out/system/services/init vfs
zig-out/system/drivers/hpet bus
Binaries land at their addressed, leaf-collapsed paths per the sub-project
resolution rule (system/services/init/init.zig -> system/services/init); vfs, hpet,
and bus are installed to their FHS homes too, so the image is complete even though
at boot they arrive inside the initial-ramdisk.
The bootloader (boot/efi.zig) now loads each artifact from its FHS path
(system\kernel, system\services\init, boot\initial-ramdisk.img); run-x86-64 mounts
zig-out directly; the QEMU test harness assembles its ESP from the FHS zig-out.
Also renames system/kernel/main.zig -> kernel.zig so the kernel follows the
name/name.zig convention (kernel/ = ring-0 code, services/ = ring-3 OS services).
Documents the resolution rule in the repository-layout section (README + coding
standard). Suite 35/35 plus host tests green.
Follow-up to the monorepo re-org. Suite 35/35 plus host tests green.
POSIX compatibility is now its own library, library/posix/ (unistd, stdio),
layered strictly over the runtime — it calls the runtime's IPC/heap, never
system calls directly. The runtime is now POSIX-free (the danos-native
application ABI). The VFS wire protocol is danos-native throughout
(Stat -> FileStatus, .stat -> .status, O_CREAT -> create); the POSIX layer
maps the POSIX spellings at the boundary. The coding standard's ABI-name
exception is scoped to one place: a file is allowed POSIX spellings only if it
lives under library/posix/ — everywhere else, danos naming with no exception.
Naming fixes, all mechanical:
- initrd -> initial-ramdisk: the source file, the module, the tool
(make-initial-ramdisk.py), the artifact (initial-ramdisk.img, including the
bootloader's load path), and the identifiers.
- system/kernel/device-service.zig -> devices-broker.zig: it is ring-0 kernel
code (the trusted device table + claim capability), not a ring-3 service. The
future user-space device *manager* (policy) will live in system/services/.
- Dropped the daemon `d` suffix: hpetd -> hpet, busd -> bus. A driver lives in
system/drivers/, so the folder already says what it is; encoding the role in
the name too is redundant. The coding standard drops that exception.
- system/devices/aml/interp.zig -> interpreter.zig (the type was already
Interpreter).
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.
A user-space process can now touch real hardware directly, capability-gated by
the device tree — the microkernel driver model.
- src/kernel/devsvc.zig: flattens the discovered device tree into an
id-indexed snapshot + a claim table at boot (devsvc.init from main.zig).
- Syscalls 11-13: dev_enumerate (snapshot the table), dev_claim (take
exclusive ownership), mmio_map (map a claimed device's MMIO window into the
caller's AS and return the register base). The claim is the capability:
mmio_map refuses any device the caller doesn't own.
- paging.mapUserDeviceInto: maps device MMIO strong-uncacheable (PCD|PWT) and
marks each leaf with a device_grant PTE bit; freeSubtree skips pmm.free on
those leaves, so tearing down a driver never returns MMIO frames to the RAM
pool (the teardown hazard). MMIO grants live in a distinct arena, PML4[226]
(Task.dev_map_next), so device pages widen no kernel mapping.
- lib/dev.zig: user enumerate/claim/mmioMap wrappers; shared DeviceDesc/ResDesc
in danos (root.zig). sbin/hpetd.zig: finds the HPET, claims it, maps its
registers, enables the counter (an MMIO write) and reads it (0xF0) — proving
read+write passthrough to real hardware.
- Tests: `hpet` (driver reads the counter advancing from ring 3) and `iopass`
(device-granted frame survives address-space teardown). Suite 33/33.
irq_bind/irq_ack (IRQ-as-message) are stubbed (-1) pending; notifyFromIsr (M7)
is the hook they'll use.
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.
Ship more than one user binary: the bootloader now ferries an initrd bundle
(the VFS server + future drivers) alongside sbin/init, and the kernel unpacks
and spawns each program.
- src/user/proto/initrd.zig: the container format (Header{magic,count} +
Entry{name[32],offset,len} + blobs) with a validating Reader, shared by the
kernel and the packer.
- tools/mkinitrd.py: host-side packer (Python — trivial format, and sidesteps
the reworked Zig 0.16 std fs/args API). build.zig runs it on the built user
binaries via addSystemCommand and installs initrd.img to zig-out/bin + the
ESP root.
- BootInfo gains initrd_base/initrd_len; efi.zig loadInit refactored into a
shared loadFile, and loadInitrd ferries \initrd.img into surviving
LoaderData like init.
- main.zig startInitrdBinaries(): parse the image, spawn every entry (kernel-
spawns-all for now; init takes over via sys_spawn later).
- sbin/vfs.zig: a heartbeat stub (the real VFS server is M9), packed into the
initrd to prove the pipeline.
- New `initrd` test: parse + spawn + confirm the vfs stub reaches ring 3 and
heartbeats. Harness ships initrd.img on the ESP. Suite 30/30.
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.
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).
The generic kernel imports cpu.zig as @import("arch") but still spoke
x86: readCr3/readCr2, pml4 and rip/rsp parameters, lapicHz/tscHz,
ioapicEntry*, IST stacks, APIC ids. Rename the public interface so the
same names work for x86_64, aarch64, and riscv64:
- readCr3 -> activePageTable; pml4 params -> root; vectorName ->
exceptionName; postCode -> checkpoint; lapicHz/tscHz ->
timerClockHz/clockHz; ioapicEntry* -> irqRoute*; ist_stack_size/
setApIstStack -> fault_stack_size/setFaultStack; startSecondary
takes a hw_id (APIC id here; MPIDR/hart id elsewhere)
- New trap-frame accessors (instructionPointer, stackPointer,
fromUser, faultAddress, syscallNumber/syscallArg/setSyscallResult)
so the generic syscall dispatcher and fault printer never name an
x86 register; readCr2 folds into faultAddress (null unless #PF)
- Generic-kernel identifiers follow: Task.pml4 -> aspace, rsp -> sp,
user_rip/user_rsp -> user_ip/user_sp, PerCpu.apic_id -> hw_id
PlatformConfig fields and the ACPI apic_id stay as-is: they describe
hardware actually discovered on this platform, and another arch would
define its own. The user-mode tests now assert fromUser instead of
the exact CS selector; the user-pf expectation follows the fault
printer's RIP -> IP label. All 28 QEMU tests pass.
Per-process address spaces (AddressSpace = a PML4 with an empty user
half and the shared kernel half copied in; create/destroy in paging.zig)
with CR3 switched on context switch and TSS.rsp0/kernel_rsp published per
switch. The GS base now points at an arch per-CPU block and every ring
transition observes the swapgs discipline, so a ring-3 `mov %ax,%gs` can
no longer poison per-CPU access. syscall/sysret is the primary user entry
(int 0x80 kept as a test path); one handler, installed once at boot,
serves both and dispatches on whether the caller is a scheduled process
or a borrowed test thread. spawnProcess loads an ELF into a fresh address
space and schedules it; exit frees the address space after switching to
the kernel tables. New `process` test: init runs twice as a real process
(create/exit/recreate) on its own page tables, coexisting with a kernel
task under preemption. Suite 28/28.
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>
fault-ap-df pins a #DF to an AP (its own IST must catch it); affinity checks a pinned task never migrates. onException now names the core, so an AP fault is attributed and shown contained. Both teeth-checked.
Add a discovery case (asserts stable ACPI/MADT/FADT/AML facts) and a wx case (audits R+X code vs NX data/rodata/heap/stack via arch.pageExecutable). Wire the existing poweroff/reboot cases into the harness. Suite: 18 -> 22.
Daniel Samson
Daniel Samson