From 1884e0bc0174ea4e98ded1db8e1fdf56d741baf0 Mon Sep 17 00:00:00 2001
From: Ayrton Munoz <adm@immunant.com>
Date: Mon, 11 Aug 2025 12:18:22 -0700
Subject: [PATCH] misc/test_runner: Replace _exit with syscall after segfault

libia2.a provides exit, _exit and call_libc_exit but we can't call any of these
after catching a segfault because we're in a signal handler at that point. exit
accesses ia2_stackptr_0 (a thread-local) using the %fs segment register whihc
does not work from a signal handler. _exit just jumps to exit so it also doesn't
work for the same reason and call_libc_exit calls dlopen which calls many
functions that are not async-signal-safe. This commit replaces the call to _exit
in the signal handler for tests with a syscall for exit instead.
---
 misc/test_runner/test_runner.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/misc/test_runner/test_runner.c b/misc/test_runner/test_runner.c
index e1ed85558..123430d00 100644
--- a/misc/test_runner/test_runner.c
+++ b/misc/test_runner/test_runner.c
@@ -7,6 +7,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
+#include <sys/syscall.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
@@ -68,11 +69,19 @@ void print_mpk_message(int sig) {
     }
     /* Write directly to stdout since printf is not async-signal-safe */
     write(1, msg, strlen(msg));
+    /*
+     * None of the various wrappers libia2.a defines for exit are
+     * async-signal-safe because they access thread-locals via the %fs segment
+     * register or call dlopen and other functions that are not
+     * async-signal-safe. Instead we just use a syscall since we just care about
+     * terminating the process without trying to do any other clean up at this
+     * point
+     */
     if (!expect_fault) {
-      _exit(-1);
+      syscall(SYS_exit, -1);
     }
   }
-  _exit(0);
+  syscall(SYS_exit, 0);
 }
 
 int main() {