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Adds SYS_SYS_SIGNAL (0xF5) accepting SIG_DFL or SIG_IGN; user-virt handlers are rejected with EINVAL until the follow-up PR. Adds a libc signal() wrapper. Shell installs SIG_IGN at startup so its own Ctrl+C is benign; children inherit SIG_DFL from program_enter. ERROR_INVALID gets the next free numeric slot (09h, appended after PR 1's renumber) rather than being inserted alphabetically — that would have shifted the already-merged ERROR_NOT_EMPTY / NOT_EXECUTE / NOT_FOUND / PROTECTED values which are now ABI-stable. Source order keeps the new code at the bottom of the block; future additions follow the same append-at-next-free convention. Builds on PR 1 (SIGINT default-kill) and PR 336 (CR3 swap fix). PR 3 (next) adds full user-handler delivery via sigcontext + sigreturn. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Stacks on #332 (SIGINT default-kill). Adds the next layer of the SIGINT design:
SYS_SYS_SIGNAL(0xF5) — userland can register a SIGINT disposition. Currently accepts onlySIG_DFL(0) andSIG_IGN(1); user-virt handler addresses are rejected withERROR_INVALID(maps toEINVAL) until PR 3.signal()libc wrapper intools/libc/signal.c+tools/libc/include/signal.h— POSIX-shape API that returns the previous handler orSIG_ERRon failure.SIG_IGNat startup so a user typing Ctrl+C at the prompt no longer kills + reloads the shell. The cooked0x03byte still lands in the line editor, which already cancels the current input line.SIG_DFL—program_enterzeroessigint_handleron every load, so each new program starts killable. The opt-out is per-program and ephemeral.The
SIGINT_TAIL_CHECKmacro inirq_tail.incnow readssigint_handlerand routes tosignal_dispatch_killforSIG_DFL, falls through (after clearingpending_sigint) forSIG_IGN, and treats the not-yet-implemented user-virt case asSIG_DFL.What's deferred to PR 3
signal(SIGINT, fn)for arbitraryfn). Needs the sigcontext frame on the user stack, a vDSO__kernel_sigreturntrampoline,SYS_SYS_SIGRETURN(0xF6), and the IRQ-handler restructure that keeps pushad on the stack at dispatch.Test plan
./make_os.shclean build./tests/test_programs.py— 29/29 pass (existing programs unaffected; shell still loads + runs)./tests/test_asm.py— 20/20 pass (self-hosting NASM byte-equality)./tests/test_bboefs.py— 6/6 passManual verification of the opt-out behaviour comes in PR 3 alongside the user-handler smoke test (
tests/programs/sigint_test.c).🤖 Generated with Claude Code