feat(signals): added signal frame delivery mechanism - #166
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Running a user handler needs the interrupted register and FP state saved onto the user stack and restored on rt_sigreturn. The per-arch frame builders, sanitizing restore path, and pending-handler selection provide that for the return-to-user hook. Co-authored-by: Cursor <cursoragent@cursor.com>
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FXRSTOR and SYSRET both fault with kernel privilege on user-controlled values, and the trap path panics for a supervisor fault instead of killing the task. Masking MXCSR and rejecting an out-of-range handler close both. Co-authored-by: Cursor <cursoragent@cursor.com>
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Summary
rt_sigreturn; this adds the per-arch frame builders, the restore path, and the selection of which pending handled signal to deliver.sysretwould fault on in Ring 0), aarch64 forces PSTATE back to EL0, and a corrupt FP record is rejected as SIGSEGV on both.Made with Cursor