xtensa's tkill syscall number is unlocated

What IS settled, so nobody re-does it

qemu-xtensa -strace names each call from the emulator's own xtensa syscall table. Calibrated first against the row the tree already considered settled — 150 came back getppid and returned the parent pid — then applied:

That collapses the 120/126/127 set recorded in ir_codegen_xtensa.inc, which had asked for a threaded measurement — unbuildable here, because {$threadsafe on} is x86-64/i386/aarch64/arm32 only, so xtensa cannot create a second thread to ask from.

What is not settled

SYS_tkill. Searched: 205–215 (nfsservctl … sched_getscheduler), 227–252 (rt_sig* … timer_getoverrun, plus Unknown syscall 238). Not present in either.

The 118–136 sweep was abandoned, deliberately. Probing it with (0, 0) args made the process exit(0) immediately with none of the loop's calls traced — so something in that range has a side effect that ends the program, and continuing to blind-fire into syscalls that do that is not a measurement, it is a hazard. The three-number question above was already answered; this one did not justify the risk.

A non-sweep source is what this needs — qemu's linux-user/xtensa syscall table, or the kernel's arch/xtensa/include/uapi/asm/unistd.h — read rather than executed, then confirmed with a single targeted -strace call at sig=0. That is one lookup and one call, and it fails differently from a sweep.

Why it matters, and how little

test_signal_siginfo.pas and test_signal_num.pas carry {$ifdef CPU…} blocks defining SYS_gettid/SYS_tkill and have no xtensa arm, so neither builds for xtensa. Both use tkill(gettid(), sig) specifically because it produces SI_TKILL, which the tests assert — kill(getpid(), sig) would give SI_USER and is not a substitute.

Prio 25 because the signal runtime on xtensa is otherwise covered: fault-to- raise, the SP rewrite and stack-overflow-to-exception all run there and match x86-64 byte for byte (see feature-a-xtensa-ucontext-pc-sp-offsets). This is two test arms, not a capability gap.

The trap, left written down

Do not copy the ARM or i386 arm. Both define SYS_gettid = 224, and on xtensa 224 is sigaltstack — it would return plausibly rather than fail, which is the failure mode that gets a wrong number believed.