_canary_stack_overflow.nx

Canary: deliberate infinite recursion to trigger SIGSEGV from stack overflow. With SA_ONSTACK + sigaltstack(2) wired into _narr_install_traps the produced ELF should NOT die silently with "qemu: uncaught target signal 11"; instead the substrate trap handler runs on the alt stack and emits a structured [✗CHK] event naming WHO/WHAT/WHY/HOW before exiting 128+11=139. USAGE: _offc/nxc.elf bench/_canary_stack_overflow.nx 1>elf 3>asm gcc-riscv64-linux-gnu (whatever) elf -> a.out qemu-riscv64-static a.out 2>fd2 4>fd4 grep "received fatal signal 11" fd2 # MUST be present PRE-FIX: handler tries to push signal frame onto exhausted stack -> recursive SIGSEGV -> SIGKILL -> empty fd2. POST-FIX: handler runs on alt stack -> emits [✗CHK] -> rc=139.