An AMD Ryzen booted to a working compositor with no USB and no storage,
and the log said only "register refused". A tree-wide audit of every
compile-time ceiling followed: 235 of them, 139 on quantities the machine
or a file decides rather than us, 5 documented anywhere, 171 silent when
reached. docs/fixed-bounds-audit.md has the inventory.
Errno attribution. The errno space was split between the kernel and the
envelope, free to drift; it is now one list in system/abi.zig, restated on
both sides, with a comptime check in library/device/driver where the two
halves are visible. device_register's six refusals and device_claim's three
are distinct codes, so a bus driver can say which rule stopped it, and
BadParent splits into NoSuchParent and NotYourParent. pci-bus reconciles
found against registered instead of counting refused functions as found.
Idempotency ordering. The child cap was checked before the identity match,
so a restarted bus was refused its own devices — the supervision restart the
system leans on ratcheted toward a degraded machine. A re-registration
consumes no slot and is now admitted first.
IOMMU fail-closed. confineDevice returned success for a device id past the
confinement table, leaving the device outside every domain while the caller
believed it confined — unreachable only while ids stop at 64, which both the
inventory move and a hardware-reported domain count would change. It refuses
now, and the coupling to the broker's device cap is a comptime assert rather
than a sentence in a comment.
PCI apertures. The bridge's MMIO apertures are derived from the holes in the
firmware memory map, and the derivation copied sub-4 GiB entries into a
fixed [64] array and skipped the rest. A skipped region is not merely lost:
the gap finder concludes it is free, so a real machine's 60-200 entry map
yields an aperture over live RAM, and containment then admits a child BAR
covering kernel memory. Rewritten to walk the map in place, with the hole
finder extracted as a pure function and driven by a synthetic 100-entry map
in a new test case. Both new tests were verified to fail on the old code.
parameters.zig gains the rationale it was missing and loses a stale sentence
pointing at the wrong file; vdso.md documents the errno space, including
EPEER, which had no written meaning anywhere.
docs/os-development/bounds.md is how a ceiling is declared from here.
docs/bounds-track-plan.md is the plan to remove the ones we invented.
Suite 114 -> 115.
VT-d and AMD-Vi are x86 hardware, but lived in the architecture-neutral
kernel tree and leaked further: the core's public Kind enum named both
vendors, and the ACPI parser read the VT-d version/capability registers
(raw volatile MMIO inside table discovery). Now the vendor backends
live in architecture/x86_64/ behind architecture.iommu — the core hands
over the discovery facts plus an injected environment (frame allocation
+ the log sink, the same pattern enablePaging uses) and receives the
hardware vtable back, so the backends never import kernel internals and
an ARM port supplies its SMMU with no core change. Discovery keeps
table facts only; the live-unit register check moved into VT-d detect
(version reading zero now stays fail-open). The unused kindOf() is
gone. Log shapes the harness pins (iommu online, DANOS-IOMMU-FAULT)
are unchanged; all five IOMMU QEMU cases pass.
The second hardware backend. The IOMMU core, DMA-region capabilities, and
per-device enforcement are unchanged; this adds AMD-Vi (IVRS) as an
alternative to Intel VT-d (DMAR) under the same Backend vtable.
- parseIvrs records the IOMMU control-register base from the first IVHD;
the platform layer gains iommu_is_amd, and the core picks the backend by
vendor at init. VT-d and AMD-Vi are mutually exclusive on real hardware.
- iommu-amd.zig: a 2 MiB device table (every DTE zeroed = deny-all until a
device is claimed), AMD native-format page tables (4 KiB leaves), a
command buffer (INVALIDATE_DEVTAB_ENTRY / INVALIDATE_IOMMU_PAGES /
COMPLETION_WAIT) and an event log for faults. The DTE forwards
interrupts unmapped, so MSI passthrough works exactly as on VT-d.
- The boot log and the iommu self-test are now vendor-aware.
**UNTESTED on real AMD hardware** — danos is developed on Intel, so this
is validated only against QEMU's amd-iommu, and every log line and doc
says so. QEMU quirk handled: its amd-iommu does not observe the
COMPLETION_WAIT store form, but consumes the command ring synchronously on
the tail-register write, so invalidations are already applied by the time
we poll — the backend warns once and proceeds.
Cases: amd-iommu (detection + scratch-domain walker) and
amd-iommu-usb-storage (full storage stack through AMD device-table
translation with per-grant capabilities), both green. 106/106.
This completes the IOVA/IOMMU-enforcement track: per-device DMA domains on
both vendors, with buffers reachable only through delegated capabilities.
First enforcement step of the IOVA track. A vendor-neutral IOMMU core
(iommu.zig) drives an Intel VT-d backend (iommu-intel.zig) to give DMA a
real translation layer instead of the fail-open free-for-all M16 left.
- Boot posture is now stated explicitly: "iommu online (Intel VT-d)"
with version/agaw/rmrr, or "none present - DMA fail-open (unisolated)".
- DMAR parsing extended to select the INCLUDE_PCI_ALL unit (real Intel
PCs put an iGPU-scoped unit first) and record single-path-endpoint
RMRRs; multi-hop scopes and extra DRHDs are counted and warned, never
silently dropped.
- Translation is enabled at boot into a blanket identity domain (all RAM
+ RMRRs, 2 MiB leaves). PCI functions are enumerated post-boot by the
ring-3 pci-bus driver, so a device is attached to the domain when its
driver claims it (confineDevice, with claim rollback if confinement
fails) and detached on driver death, before broker release and DMA
frame teardown. Unclaimed devices are non-present: their DMA faults.
- Interrupt remapping stays off, so MSI writes to 0xFEE00000 bypass
translation and the interrupt-driven xHC keeps working.
- devices-broker gains pciAddressOf (derives BDF from the config-space
ECAM offset), unclaim, and forEachPciFunction.
Faults are drained and logged rate-limited as DANOS-IOMMU-FAULT.
Cases: iommu extended (translation on, scratch-domain map/resolve/unmap,
zero idle faults); new iommu-usb-storage and iommu-usb-hid run the full
storage + input stacks through translated DMA with MSI intact. 103/103.
Follow-up cleanup of the just-moved kernel device code:
- power.zig -> acpi.zig. Its reboot() is built entirely on the FADT reset
register (acpi.power_information) plus the legacy 0xCF9/8042 fallbacks — it is
ACPI reboot, so it becomes acpi.reboot (the "P" in ACPI). platform.reboot
still delegates; soft-off/S5 stays the ring-3 acpi service's job as before.
- device-tree.zig -> fdt.zig. It is a discovery *backend* (the ARM/FDT parser,
a sibling of acpi.zig), not part of the model — renaming it to its actual
subject kills the confusing device-tree / device-model DeviceTree name clash
and makes acpi.zig + fdt.zig read as the two parallel backends.
- Flatten: device-model.zig, acpi.zig, fdt.zig, platform.zig move out of the
system/kernel/devices/ subdir up into system/kernel/, joining devices-broker.zig
(already flat). The kernel dir is a flat pile by convention (only architecture/
is a subdir), so the subdir — and its poor "devices" name — is gone.
Pure restructure; "platform" module name unchanged, all cross-file deps are
relative siblings that moved together. zig build + test green; smoke, discovery,
acpi-parse, acpi-ps2, acpi-report, power-button, orderly-shutdown, reboot pass.
Daniel Samson