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/* crash-handler.c -- PID 1 helper to dump core upon a crash on GNU/Linux.
Copyright © 2019 Ludovic Courtès <ludo@gnu.org>
This file is part of the GNU Shepherd.
The GNU Shepherd is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at
your option) any later version.
The GNU Shepherd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with the GNU Shepherd. If not, see <https://www.gnu.org/licenses/>. */
#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <sched.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h> /* For SYS_xxx definitions */
#include <signal.h>
/* Arrange to dump core. */
static void
handle_crash (int sig)
{
static const char msg[] = "Shepherd crashed!\n";
write (2, msg, sizeof msg);
#ifdef __sparc__
/* See 'raw_clone' in systemd. */
# error "SPARC uses a different 'clone' syscall convention"
#endif
/* Start a child process that will be able to dump core. */
pid_t pid = syscall (SYS_clone, SIGCHLD, NULL);
if (pid < 0)
abort ();
if (pid == 0)
{
/* Restore the default signal handler to get a core dump. */
signal (sig, SIG_DFL);
const struct rlimit infinity = { RLIM_INFINITY, RLIM_INFINITY };
setrlimit (RLIMIT_CORE, &infinity);
chdir ("/");
int pid = syscall (SYS_getpid);
kill (pid, sig);
/* As it turns out, 'kill' simply returns without doing anything, which
is consistent with the "Notes" section of kill(2). Thus, force a
crash. */
* (int *) 0 = 42;
_exit (254);
}
else
{
/* Wait for the child process and terminate. */
signal (sig, SIG_IGN);
int status;
waitpid (pid, &status, 0);
sync ();
_exit (255);
}
_exit (253);
}
static void initialize_crash_handler (void)
__attribute__ ((constructor));
static void
initialize_crash_handler (void)
{
/* Register raw signal handlers. This cannot be done in Scheme because the
handler can only call async-signal-safe functions. */
signal (SIGSEGV, handle_crash);
signal (SIGABRT, handle_crash);
}
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