Implement waitpid syscall and complete signal handling #63
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This commit adds full waitpid support and fixes critical signal handling bugs: ## waitpid syscall (#61 Wait4) - Blocking wait for specific child or any child (pid=-1) - WNOHANG support for non-blocking poll - Proper wstatus encoding: (exit_code & 0xff) << 8 - ECHILD error when no children exist ## Signal inheritance - Fork copies signal handlers to child (signals.fork()) - Exec resets user handlers to SIG_DFL (signals.exec_reset()) - SIGCHLD delivered to parent when child exits ## Critical bug fix: sigreturn RAX corruption - sigreturn was correctly restoring RAX from signal frame - But syscall dispatcher then overwrote it with return value (0) - This caused fork_result=0 in parent after signal handler return - Fixed by returning early from sigreturn to skip set_return_value() ## New tests (all passing, 84/84 boot stages) - sigchld_test: SIGCHLD delivery on child exit - signal_fork_test: Handler inheritance across fork - signal_exec_test: Handler reset on exec - waitpid_test: Blocking wait and status verification - wnohang_timing_test: Non-blocking poll behavior ## libbreenix additions - waitpid() wrapper function - POSIX macros: wifexited, wexitstatus, wifsignaled, wtermsig 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
The exec syscall in fork_test was using the old string API signature. Updated to use the correct null-terminated byte string format that matches the current libbreenix exec() function signature. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
This PR completes POSIX signal handling and implements the waitpid syscall with comprehensive test coverage.
Key Changes
waitpid syscall (#61/Wait4)
(exit_code & 0xff) << 8Signal inheritance (fork/exec)
SIGCHLD delivery
Critical bug fix: sigreturn RAX corruption
New Tests
sigchld_test.rs- SIGCHLD delivery and handler executionsignal_fork_test.rs- Signal handler inheritance across forksignal_exec_test.rs- Signal reset on exec (with signal_exec_check helper)waitpid_test.rs- Blocking waitpid and WNOHANG behaviorwnohang_timing_test.rs- Non-blocking wait timing verificationlibbreenix Additions
waitpid()wrapper functionwifexited(),wexitstatus(),wifsignaled(),wtermsig()WNOHANGconstant (0x1)Test Results
All 84/84 boot stages pass, including the new signal and waitpid tests.
Test plan
🤖 Generated with Claude Code