fix: ARM64 TPIDR_EL0, signal trampoline, and /dev/tty controlling terminal#235
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fix: ARM64 TPIDR_EL0, signal trampoline, and /dev/tty controlling terminal#235
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…e syscall number Two ARM64 fixes that resolve DATA_ABORT crashes at FAR=0xffffffffffffff5c when running BusyBox ash shell and musl-linked programs: 1. TPIDR_EL0 (Thread Local Storage pointer) was never saved or restored during context switches. When multiple userspace processes share a CPU, they clobber each other's TLS pointer. musl libc stores errno and pthread structures via TPIDR_EL0, so a zeroed/wrong value causes accesses to addresses like 0 - 164 = 0xffffffffffffff5c. Added tpidr_el0 field to CpuContext and mrs/msr instructions in all 5 context switch paths: save_userspace, save_kernel, restore_kernel, restore_userspace, and setup_first_entry. Also preserved in from_aarch64_frame for fork inheritance. 2. Signal trampoline used x86_64 syscall number 15 for rt_sigreturn instead of the correct ARM64 number 139. This caused "Unknown syscall" errors when signal handlers returned via the trampoline. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
…b control setup Three fixes for BusyBox ash "can't access tty; job control turned off": 1. /dev/tty open now matches by session ID instead of PID. The controlling terminal belongs to the entire session, not just the session leader. When ash (child of bsh) opens /dev/tty, it needs to find the PTY that bsh (the session leader) set up via TIOCSCTTY. Previously matched by PID which failed for any non-session-leader process. 2. TIOCSCTTY now also sets foreground_pgid so tcgetpgrp() returns a valid value instead of 0. 3. bwm's spawn_child calls TIOCSCTTY after opening PTY slave, and libbreenix gains set_controlling_terminal() wrapper. Root cause confirmed by independent Codex + Opus investigation (panel of experts pattern). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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