Files
StarForth/src/starkernel
Robert Allan JamesandClaude Sonnet 5 9142dda2d6 Fix use-after-free in sk_repl_idle()'s idle-tick VM resolution (FABRIC-3.md §XIII)
Root-caused a heap-corruption bug that reliably failed WIREBIND identity
attach on the third attach/detach cycle in one boot. sk_console_readline()
and sk_console_getkey() captured `active_vm` once from their caller and
kept passing that same (possibly long-stale) pointer to sk_repl_idle() on
every idle tick serviced while blocked waiting for input. If the VM it
pointed at was killed (WIREBIND detach) mid-block, the existing bailout
only checked a generic "is anyone attached" boolean -- masked as soon as a
different identity attached next -- so blk_vm_flush_all() kept writing
into a freed VM struct sitting on kmalloc's own free list, corrupting the
free list's linked-list metadata itself.

Both idle branches now re-resolve the live active VM fresh from
g_repl_active_vm on every tick, matching the dispatch-side fix already
made for the sibling bug in §XII.3.

Verified: rebuilt amd64, reran the exact three-cycle repro that reliably
corrupted the heap before the fix -- free-list census stayed stable
through the same idle window that previously collapsed to zero. All three
architectures (amd64/aarch64/riscv64) boot clean to the zuse)ok> prompt.

kmalloc_debug_census()/kmalloc_debug_census_bytes() kept as permanent
diagnostic infrastructure; every other temporary probe added during the
investigation was reverted.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EXieurDfDSsDFdnSyusuWo
2026-09-10 20:30:41 -04:00
..
2026-09-01 12:07:32 -04:00

src/starkernel/

LithosAnanke — the bare-metal UEFI kernel that boots StarForth directly on hardware (amd64/aarch64/riscv64). Built only via Makefile.starkernel; the only valid acceptance test is the three-arch QEMU boot (see .claude/CLAUDE.md), never make test.

  • kernel_main.c — kernel entry point, driving the boot milestones (console init, PMM, VMM, interrupts, timers, kmalloc heap, VM bootstrap).
  • repl.c — kernel REPL.
  • doe_log.c — kernel-side DoE (Design of Experiments) metrics logging.

Subdirectories:

  • arch/{amd64,aarch64,riscv64}/ — per-architecture support (APIC/GIC/ PLIC interrupt controller, timers, boot/ISR assembly).
  • boot/ — UEFI loader, ELF loading, kernel command-line parsing.
  • capsule/ — capsule birth/run/load/validate pipeline.
  • hal/ — hardware-abstraction-layer implementation (console, framebuffer, VT100, memory, host services).
  • hash/ — XXHash64 content-addressing implementation.
  • math/ — kernel-build Q48.16 fixed-point arithmetic.
  • memory/ — physical/virtual memory managers and the kernel heap.
  • pci/ — PCI bus enumeration.
  • virtio/ — VirtIO block device driver.
  • vm/ — kernel VM subsystem (bootstrap, core interpreter, parity logging, capsule arena).

See include/starkernel/README.md for the corresponding headers.