Files
LithosAnanake/experiments
Robert Allan JamesandClaude Sonnet 5 f43f3f4482 aarch64: detect exception level at runtime, cached accessor
Punch list §25 item 0.4 complete.

Adds aarch64_current_el() in arch.c: reads CurrentEL[3:2] on first call,
caches the result (CurrentEL cannot change post-ExitBootServices, so every
consumer gets the same answer without repeating the MRS). Called from
arch_interrupts_init() in interrupts.c -- the earliest point with both a
working console (up since M1) and a genuine first consumer (vector
installation is the first EL-dependent operation) -- and the detected level
is printed to the boot log there.

Declared via extern-in-place in interrupts.c rather than added to the shared
arch.h: "exception level" has no amd64/riscv64 equivalent, matching the
convention already used for riscv64_timer_rearm() in item 0.3.

Verified on real QEMU output: "AArch64: running at EL1", correctly positioned
immediately before "IDT installed." in the serial log. Boots clean, dict_hash
0x3d4e1daf289da94f unchanged from the item 0.1-0.3 baseline.

Scope: this item establishes the detection and exposes it; it does not yet
change VBAR/ELR/SPSR or timer-register selection to use it. arch_interrupts_init()
still writes VBAR_EL1 unconditionally, and now says so explicitly in its own
doc comment -- if aarch64_current_el() ever reports 2 on real hardware,
exceptions taken at EL2 vector through VBAR_EL2, which nothing programs yet.
That gap is items 0.5 (vectors/saved-state) and 0.7 (CNTP vs CNTHP) to close,
per FABRIC.md's GAP-B3 finding. The boot-log EL2 case prints a note pointing
at both.

Only aarch64-scoped files touched (arch.c, interrupts.c) -- no shared loader
or header changed, so amd64 and riscv64 are provably unaffected; not rebuilt
for this item.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-08-03 18:30:25 -04:00
..

experiments/

Design of Experiments (DoE) campaign data and analysis for the LithosAnanke kernel.

  • bare_metal/ — the bare-metal DoE experiment: blind full-factorial 2⁴ runs measuring the L8 Jacquard mode selector's effect on the Steady-State Machine across amd64/aarch64/riscv64. See experiments/bare_metal/README.md for the full directory layout (runs/, latest/, analysis/{charts,tables,report}).

Hosted-VM DoE campaigns (factorial/heartbeat/ablation studies) live under docs/working/experiments/ instead — this top-level directory is specifically the kernel/bare-metal side.