Probes and Evidence

Relevant source files

docs/probes/ is a dated evidence log. Project rules in TODO_NOW.md: never fudge exit codes, never report PASS without a real artifact; an amber “FAIL with diagnostic” is normal and publishable, and only a HARD FAIL blocks.

Timeline

Date	Probe	Branch	Outcome
2026-07-30	Phase 1 ARMv8-A risk gate	`main`	PASS: CPU viability
2026-07-30	Phase 2 `virt-pi5` boot	`main`	MMU resolved; userspace blocked by rootfs allocation panic
2026-09-28	Prebuilt-image adapter verification	`main`	Adapters verified; Pi 5 and x86_64 guests fail; AArch64/RISC-V not validated
2026-09-30	Identified AArch64 virt build	branch only	Blocked at guest link (`__kernel_end` undefined)
2026-09-30	Virt linker fix + three boots	branch only	All three timed out (124) with empty UART
2026-10-01	Renode model audit	branch only	No RP1/RP2040/BCM2712 models; warnings cannot prove strict coverage
2026-10-01	RP1 PWM / GPIO / RIO / pad models	branch only	Native unit suites pass; no guest qualification

Phase 1 risk gate (2026-07-30)

Goal: prove axiomOS reaches UART on a stock Renode ARMv8-A platform before any custom Pi modeling.

Renode 1.16.1.16973, stock platforms/cpus/cortex-a78.repl (UART 0x09000000, GIC 0x08000000, RAM 0x40000000), DTB renode/probes/minimal-virt-stub.dtb loaded at 0x44000000, ELF entry 0x40080000.
tools/probe-armv8a.sh runs 0.1 virtual seconds under a 90 s wall timeout and requires both exit 0 and the marker Logging initialized (Renode 1.16 can exit 0 after Monitor errors).
Result: marker at about 1.0 ms virtual time; continued through exception vectors, physical memory, page tables, and heap init. Not a userspace claim.
Observations: early writes target the Pi UART 0x10_7d00_1000 (absent on that platform); post-heap high-half accesses were unmapped there, motivating Phase 2 board work.

Decision: proceed to Phase 2; the “revisit backend choice” stop condition was not triggered.

Phase 2 `virt-pi5` boot (2026-07-30)

Gate: the unmodified embedded-rpi5 image must print === axiomos eBPF init === on virt-pi5.

The initial run entered at Renode’s default EL3. axiomOS treats non-EL2 entry as EL1, so it programmed EL1 MMU registers while still at EL3, and high-half accesses went untranslated to the bus.
Fix: cpu SetAvailableExceptionLevels false false and gic DisabledSecurity true, plus PL011 handoff state. High-half warnings vanished; real MMU translation is exercised, with no Renode fork or address alias.
Current result:


PI5_BENCH_FAIL stage=rp1_irq_route error=PcieLinkDown(0)
kernel panicked ... memory allocation of 20971520 bytes failed

The first line is expected until a PCIe/RP1 model exists. The second is the userspace blocker: the 20 MiB embedded rootfs allocation exceeds the guest heap’s usable contiguous capacity, an axiomOS issue.

Prebuilt-image adapter verification (2026-09-28)

Reference axiomOS main at b8953b59, inspected read-only; no builds.

Check	Result
Rust CLI tests	19 passed
Adapter regression tests (stand-ins)	12 passed
Renode peripheral/platform tests	5 passed
`doctor`, shell syntax, whitespace	Passed
Renode Pi 5 live boot	Fail: `V04_PANIC`, `memory allocation of 10485760 bytes failed`; exit 1
QEMU x86_64 live boot (QEMU 11.1.1)	Fail: `BOOT_FATAL code=root-filesystem-invalid`; exit 1
QEMU AArch64 live boot	Not validated: no identified compatible `virt` image
QEMU RISC-V live boot	Not validated: demo ELF absent

Before this change, QEMU test exited zero even with nonexistent inputs. The real Renode run also confirmed that the positional script path needs escaped spaces while in-script paths need quoting. Input hashes were unchanged after the x86_64 run, confirming snapshots.

Adapter tests use stand-in emulators. No mocked success is a guest boot PASS.

Later evidence (branch only)

These probes exist on fix/adapter-pid-readiness, not main:

Identified virt build (2026-09-30): a clean clone of axiomOS b8953b5 with nightly-2026-07-02 built the 20 MiB rootfs, but the virt,cloud-profile kernel failed to link because kernel/linker-virt.ld omits __kernel_end.
Linker fix (2026-09-30): axiomOS PR #196 (commit a6f48d1) fixed the symbol and a validated manifest bundle was produced. Three QEMU runs (virt-11.1,gic-version=2,virtualization=off,secure=off, Cortex-A57, 1 GiB, semihosting off) each timed out after 30 s with empty UART. GDB showed _start_asm at 0x40080000 with x0=0 storing to the Pi UART 0x107d001000, after which PC jumps to 0x200. The blocker is the Pi-specific early UART store on the virt entry path.
Renode model audit and RP1 models (2026-10-01): see RP1 Models.