Bring the docs up to the M17-M18 reality; pre-settle M19-M20 ambiguities

resilience.md: steps 1-4 of the ladder are built — supervision, exit
reasons, restart with backoff, crash-loop caps, all proven by scenario;
what remains is scope, not mechanism. README statuses follow. drivers.md
gains the driver-contract section (harness, hello, crash-freely). The
M19-M20 plan pre-settles three things the loop would otherwise have had
to decide alone: the memory-map pass-through for apertures, the manager
spawning 'discovery' from M20.1, and hid[8] riding ChildAdded for ACPI
string identity until the FDT widening.
This commit is contained in:
Daniel Samson
2026-07-13 01:49:52 +01:00
parent a53c2b0193
commit 75d62660b0
4 changed files with 50 additions and 12 deletions
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@@ -45,20 +45,22 @@ rather than restate it. Roughly in the order things happen at runtime:
until its hardware interrupts it**. The claim is the capability; `irq_ack` is the until its hardware interrupts it**. The claim is the capability; `irq_ack` is the
unmask. unmask.
14. **[driver-model.md](driver-model.md) — buses, classes and host controllers.** How 14. **[driver-model.md](driver-model.md) — buses, classes and host controllers.** How
real driver stacks factor into three shapes, how families share code, and the real driver stacks factor into three shapes and how families share code. The
proposed ABI for the three primitives still missing (capability passing, DMA + three primitives it proposed are long since built (M13 capability passing,
memory barriers, MSI). M14 DMA + barriers, M15 MSI), and the driver *contract* on top of them —
hello, supervision, restart — is built too (device-manager.md, M18).
15. **[process-management.md](process-management.md) — process management.** The 15. **[process-management.md](process-management.md) — process management.** The
microkernel's `ps`/`kill`/SIGCHLD: enumerate as a table snapshot, the microkernel's `ps`/`kill`/SIGCHLD: enumerate as a table snapshot, the
supervision link as the kill authority, and child-exit notifications over the supervision link as the kill authority, and child-exit notifications over the
same endpoints IRQs arrive on. same endpoints IRQs arrive on.
16. **[process-lifecycle.md](process-lifecycle.md) — the process lifecycle.** Design: 16. **[process-lifecycle.md](process-lifecycle.md) — the process lifecycle.** Built
signals over IPC as the one lifecycle vocabulary every process speaks — the (M17): signals over IPC as the one lifecycle vocabulary every process speaks — the
POSIX.1-1990 words with message delivery instead of stack hijack, the stable POSIX.1-1990 words with message delivery instead of stack hijack, the stable
`runtime.process` interface, exit reasons, published exit events any stateful `runtime.process` interface, exit reasons, published exit events any stateful
service can subscribe to (the VFS releasing dead clients' handles), and the two service can subscribe to (the VFS releasing dead clients' handles), and the two
iron rules (cleanup is the kernel's job; kill is not a signal). iron rules (cleanup is the kernel's job; kill is not a signal).
17. **[device-manager.md](device-manager.md) — the device manager.** Design: the 17. **[device-manager.md](device-manager.md) — the device manager.** Built (M18,
through the app surface): the
tree, the matcher, and the supervisor. Tree structure lives in the manager, tree, the matcher, and the supervisor. Tree structure lives in the manager,
authority stays in the kernel; bus drivers report what they see; drivers are authority stays in the kernel; bus drivers report what they see; drivers are
restarted through the lifecycle vocabulary — the plan that turns restarted through the lifecycle vocabulary — the plan that turns
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@@ -362,3 +362,23 @@ the first DMA driver to protect and test against) and these smaller items:
- **Interrupt priority / threaded IRQ latency.** `notifyFromIsr` enqueues the woken - **Interrupt priority / threaded IRQ latency.** `notifyFromIsr` enqueues the woken
driver but doesn't preempt (`wakeLocked` deliberately leaves that to the caller), so driver but doesn't preempt (`wakeLocked` deliberately leaves that to the caller), so
a woken driver waits for the next scheduling point. a woken driver waits for the next scheduling point.
## The driver contract (M17–M18)
Claiming and mapping is half of being a danos driver; the other half is the
**lifecycle and protocol contract**, and the runtime makes it nearly free:
- Build on `runtime.service.run` — one replyWait loop folding protocol
requests, signals, and notifications into callbacks. The harness answers the
universal zero-length ping and turns `terminate` into a clean exit for you
([process-lifecycle.md](process-lifecycle.md)).
- A driver spawned with an assignment (its device id as argv[1]) sends the
versioned `hello` to the device manager inside the deadline, and a **bus**
driver reports what it discovers with `child_added`
([device-manager.md](device-manager.md); usb-xhci-bus is the reference
implementation).
- Crash freely — that is the design. The kernel releases your claims, IRQ
bindings, and MSI vectors at death; the manager reads your exit reason,
prunes what you reported, restarts you with backoff, and your fresh instance
re-claims and re-reports. Never depend on your own cleanup running
(iron rule 1).
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@@ -122,7 +122,9 @@ branch is green; keep branches; push everything.
## Phase notes ## Phase notes
**M19.0 apertures:** the boot memory map already crosses the handoff **M19.0 apertures:** the boot memory map already crosses the handoff
([boot-handoff]); the holes computation belongs where the bridge node is built ([boot-handoff]), but discovery never sees it today — expect a small
pass-through (kernel init hands the map to the platform layer) before the
holes computation, which belongs where the bridge node is built
(`parseMcfg`). Sanity-check on QEMU q35: the xHCI BAR (`0xc0000000`-region (`parseMcfg`). Sanity-check on QEMU q35: the xHCI BAR (`0xc0000000`-region
values seen in the M18 logs) must land inside a derived aperture, asserted in values seen in the M18 logs) must land inside a derived aperture, asserted in
the kernel unit test. the kernel unit test.
@@ -142,6 +144,13 @@ scenario can assert it.
kernel still enumerates (timers, ACPI nodes until M20.3). The PCI arm of kernel still enumerates (timers, ACPI nodes until M20.3). The PCI arm of
`pciDriverFor` switches source; `driverFor` doesn't move until M20.3. `pciDriverFor` switches source; `driverFor` doesn't move until M20.3.
**M20.1 spawn and identity (pre-settled 2026-07-13):** the manager spawns
`discovery` by its neutral ramdisk name at startup, as an ordinary protocol
driver (hello, supervision) — from M20.1 on, on every boot. For reporting ACPI
devices, `ChildAdded` gains `hid: [8]u8` (EISA ids fit; zero = none):
firmware *string* identity travels beside the numeric `identity` field until
the FDT-driven widening replaces both (decision 7).
**M20.1 Hal in ring 3:** `mapMmio` → `device.mmioMap` over the claimed **M20.1 Hal in ring 3:** `mapMmio` → `device.mmioMap` over the claimed
acpi-tables node (plus a table-offset map for blobs); `pioRead`/`pioWrite` → acpi-tables node (plus a table-offset map for blobs); `pioRead`/`pioWrite` →
`device.ioRead`/`ioWrite` against its io_port resource. The interpreter cannot `device.ioRead`/`ioWrite` against its io_port resource. The interpreter cannot
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@@ -1,10 +1,17 @@
# Resilience: fault isolation and live restart # Resilience: fault isolation and live restart
Steps 1–2 of the ordering below are **built**: user-mode isolation, and fault → Steps 1–4 of the ordering below are **built** (M17–M18, 2026-07-13): user-mode
kill the process → keep the core (`onException` in `system/kernel/kernel.zig`; the isolation; fault → kill the process → keep the core (`onException`; the
`fault-recovery` test proves a crashing ring-3 process dies alone while the system `fault-recovery` test); the supervisor notification **with exit reasons**
keeps running). The supervisor notification and restart policy (steps 3+) are ([process-lifecycle.md](process-lifecycle.md) — clean exit, fault class, or
still design. This is the property danos is really chasing: killed, recorded before the notice posts); and the **restart policy itself**
([device-manager.md](device-manager.md)): the device manager supervises every
driver, restarts crashes with backoff, caps crash loops, and re-claims work
because the kernel releases a dead process's claims. The `driver-restart` and
`usb-report` scenarios prove kill → release → respawn → re-claim → re-report
end to end. What remains of this document's ladder is scope, not mechanism:
more of the system moved into restartable processes (the discovery migration,
[m19-m20-plan.md](m19-m20-plan.md), is the next rung). This is the property danos is really chasing:
**if a part of the OS breaks, isolate it, and re-initialise it — without rebooting.** **if a part of the OS breaks, isolate it, and re-initialise it — without rebooting.**
A crashed driver gets restarted; a wedged service gets killed and brought back. It's A crashed driver gets restarted; a wedged service gets killed and brought back. It's
the reason the [microkernel](vision.md) shape was chosen, and it's a *separate* goal the reason the [microkernel](vision.md) shape was chosen, and it's a *separate* goal