56da55aba9467a668846f85054e32bee16ff89f6
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Commits
| Author | SHA1 | Message | Date | |
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 Robert Allan JamesandClaude Opus 5.5
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56da55aba9 |
FABRIC-3.8.md Stage B: kernel-side idle loop in the switch trampoline
sk_vm_switch_entry() stops being the Stage-2 placeholder bounce and becomes every switch participant's own idle loop: it drains one of its own kernel-Hermes messages per pass, on its own native stack (driven by the drain's return value, so a non-consuming drain cannot spin), and when nothing is drained it marks the VM parked_idle and yields back. It is entirely OS-driven, with no VM-side yield word. sk_hermes_drain_checkpoint() gains a per-VM hermes_draining guard so a payload's own in-word checkpoint cannot drain a second message inside the first. Still inert in normal operation: nothing marks work until Stage C. Finding fixed here: amd64 sk_vm_switch_prime built the first-entry frame at top-56, entering with rsp 16-aligned instead of the SysV-required 8 mod 16, so the first aligned SSE spill in a callee took #GP (logs/20260923-142526, kept). It had been latent since SXXVIII Stage 2 because the placeholder never called anything. The frame is now at top-64 with a zeroed pad slot. aarch64 and riscv64 were already correct. Evidence: a temporary kernel_main probe (reverted, not in this commit) queued two messages to Hestia, the first calling a colon word, and switched into her. It passed on all three ISAs: 0 pending, parked_idle, depth 0, context saved on her own stack, SB-SEQ=12 (drained one at a time, not nested), ledger and stadium_conserved restored. Formal acceptance without the probe on all three ISAs: dict_hash identical and unchanged, zero UNKNOWN WORD or faults, and the live WIREBIND mint -> USE -> 1 2 + . -> 3 relay. FABRIC-3.8.md also records Captain Bob's rulings that no VM-side word ever gives up control and that multitasking is a compudynamic hybrid, and opens SS3.12 (VM frames for per-VM execution state). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> |
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Robert Allan JamesandClaude Sonnet 5
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66beae7fd4 |
Stage 3 follow-on: message-arrival eligibility hook + trampoline-blind switch-storm fix (FABRIC-3.md §XXVIII.2)
Implements the message-arrival eligibility signal FABRIC-3.md §XXVIII.1 left open (has_work per-slot flag, set via new SWITCH-MARK-WORK primitive from MSG-SEND) so an idle VM never becomes a switch target purely by waiting out the readiness threshold. Also root-causes and fixes a second, independent switch-storm: the tick's "who is current" check used vm_log_attributed_vm(), which can't see a VM parked in switch.c's own raw trampoline. Replaced with a dedicated g_switch_current_vm tracked by the switch mechanism itself, and moved target-slot eligibility reset to the switch decision point instead of relying on ISR polling to observe a window that can be only a few instructions wide. Verified live on all 3 architectures: clean boot to zuse@Hera] ok>, live cross-VM message dispatch, and (since a quiet log looks identical to a livelocked storm once the DoE probe is gone) confirmed genuine REPL liveness via QMP send-key + screendump on aarch64/riscv64, not log inspection alone. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01BWpNjdwPtFLuVLaAq44L9K |
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Robert Allan JamesandClaude Sonnet 5
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862d7d9c48 |
Stage 3 follow-on: fix stack-ownership corruption + DoE switch columns (FABRIC-3.md §XXVIII.1)
DoE CSV gained 6 switch-signal columns (switch_count_cumulative, switch_current_slot, switch_*_readiness, switch_ticks_since), and verifying them with a boot-time HB-ON probe surfaced a real livelock: the preemption checkpoint could fire inside a VM-EXEC-nested execute_colon_word() call and switch away from a stack it didn't own, parking a borrowed region of the caller's stack under the wrong VM's saved-context pointer. The trampoline bounce was the visible (safe) half of this; the corruption was the quiet half, live in every prior "clean" Stage 3 boot without ever showing up in the log. Fixed by gating the checkpoint on being at the outermost vm_interpret() call (g_vm_interpret_depth / sk_vm_at_outermost_interpret(), vm_core.c), per Bob's decision. Also fixed two related bugs found in the same pass: g_switch_back_to was a single global stale after first entry, now per-VM state (native_switch_back_to); note_switch_performed() fired on resume instead of switch-out, now called before the switch. Verified on all 3 architectures: steady log growth (no freeze), zero leaked QEMU processes, DoE columns internally consistent, Hermes/Artemis confirmed genuinely executing (not just trampoline-bouncing). Temporary HB-ON boot probe reverted after capture. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016UNhH1mhi52i6Qihh7ZV5S |
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Robert Allan JamesandClaude Sonnet 5
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f790d0995e |
Stage 2: cooperative VM context switch primitive, proven on all 3 arches (FABRIC-3.md §XXVIII)
Third stage of the preemptive context-switching plan. The real save/restore switch mechanism now exists -- the first time anything has ever executed on a VM's own native stack (Stage 1 allocated them, unused). New sk_vm_switch_to() (switch.S, one per arch) is an ordinary function call, not an interrupt -- so unlike Stage 0's trap frame, the ABI already covers every caller-saved register; only the callee-saved set needs explicit save/restore (amd64: rbx/rbp/r12-r15, no FP at all since SysV has no callee-saved XMM; aarch64: x19-x28/x29/x30 + d8-d15; riscv64: s0-s11/ra + fs0-fs11, FS-gated like Stage 0 but read once and reused for both halves within one call, since FS is genuine global CPU state, not part of what's switched). A sibling sk_vm_switch_prime() in the same file builds the synthetic first-entry frame, kept in assembly so the layout can never drift out of sync with sk_vm_switch_to() itself. New switch.c/switch.h: sk_vm_context_switch(from, to) handles first-entry priming vs. resuming a parked context, and updates registry state (new VM_STATE_SWITCHED_OUT, distinct from VM_STATE_STOPPED -- STOPPED means no live frame, this means the opposite). sk_vm_switch_entry() is the minimal permanent trampoline every freshly-entered VM lands in: no production behavior defined yet, so it just yields straight back to whoever switched to it, forever. Closes the confirmed unguarded-KILL UAF found during planning: capsule_vm_kill(), mama_word_kill(), and capsule_vm_kill_all_nonmama() all now refuse (or silently leak rather than free, on the cold-restart path where arch_cold_reset() wipes everything immediately after anyway) tearing down a switched-out VM. Side effect found, not built on purpose: the existing MSG-TICK idle-pump already filters on VM_STATE_LIVE, so it automatically stopped dispatching into a switched-out VM with zero changes needed there. Verified via a temporary SWITCH-TEST probe (boot-triggered, since nothing can type interactively into a foreground-only QEMU session) that round-tripped a sentinel through 5 real Hera<->Hermes switches on all 3 architectures: 5/5 rounds, 0 failures, clean continuation to ok>. Probe fully reverted after capture; kernel_main.c shows zero diff. Also: Makefile.starkernel's LOADER_EXTRA_SRCS/LOADER_ASM needed the new files added explicitly (this project's "loader" PE binary is the full running kernel, not a thin bootstrap stage), and aarch64's switch.S needed the same #ifndef _WIN32 guard around .hidden that isr.S already carries (aarch64's loader assembles via clang targeting a PE/COFF target with no .hidden equivalent) -- caught by a build failure, fixed. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_016UNhH1mhi52i6Qihh7ZV5S |