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sig.c
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sig.c
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/* Signal management - Be conservative with what finit responds to!
*
* Copyright (c) 2008-2010 Claudio Matsuoka <cmatsuoka@gmail.com>
* Copyright (c) 2008-2014 Joachim Nilsson <troglobit@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* The standard SysV init only responds to the following signals:
* SIGHUP
* Has the same effect as telinit q.
*
* SIGUSR1
* On receipt of this signals, init closes and re-opens its control
* fifo, /dev/initctl. Useful for bootscripts when /dev is remounted.
*
* SIGINT
* Normally the kernel sends this signal to init when CTRL-ALT-DEL is
* pressed. It activates the ctrlaltdel action.
*
* SIGWINCH
* The kernel sends this signal when the KeyboardSignal key is hit.
* It activates the kbrequest action.
*/
#include <string.h> /* strerror() */
#include <sys/reboot.h>
#include <sys/wait.h>
#include "finit.h"
#include "conf.h"
#include "helpers.h"
#include "plugin.h"
#include "private.h"
#include "sig.h"
#include "service.h"
#include "libite/lite.h"
static int stopped = 0;
static uev_t sighup_watcher, sigint_watcher, sigpwr_watcher;
static uev_t sigchld_watcher, sigsegv_watcher;
static uev_t sigstop_watcher, sigtstp_watcher, sigcont_watcher;
void do_shutdown(int sig)
{
touch(SYNC_SHUTDOWN);
if (sdown)
run_interactive(sdown, "Calling shutdown hook: %s", sdown);
/* Call all shutdown hooks before rebooting... */
plugin_run_hooks(HOOK_SHUTDOWN);
/* Here is where we signal watchdogd to do a forced reset for us */
_d("Sending SIGTERM to all processes.");
kill(-1, SIGTERM);
/* Wait for WDT to timeout, should be no more than ~1 sec. */
do_sleep(2);
_d("Sending SIGKILL to remaining processes.");
kill(-1, SIGKILL);
sync();
sync();
_d("Unmounting file systems, remounting / read-only.");
run("/bin/umount -fa 2>/dev/null");
run("/bin/mount -n -o remount,ro / 2>/dev/null");
run("/sbin/swapoff -ea");
_d("%s.", sig == SIGINT || sig == SIGUSR1 ? "Rebooting" : "Halting");
if (sig == SIGINT || sig == SIGUSR1)
reboot(RB_AUTOBOOT);
reboot(RB_POWER_OFF);
}
/*
* Reload .conf files in /etc/finit.d/
*/
static void sighup_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
{
service_reload_dynamic();
}
/*
* Shut down on INT PWR
*/
static void sigint_cb(uev_t *w, void *UNUSED(arg), int UNUSED(events))
{
do_shutdown(w->signo);
}
/*
* SIGCHLD: one of our children has died
*/
static void sigchld_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
{
pid_t pid;
/* Reap all the children! */
do {
pid = waitpid(-1, NULL, WNOHANG);
if (pid > 0) {
_d("Collected child %d", pid);
service_monitor(pid);
}
} while (pid > 0);
}
/*
* SIGSEGV: mostly if service callbacks segfault
*/
static void sigsegv_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
{
_e("PID %d caused a segfault!\n", getpid());
exit(-1);
}
/*
* SIGSTOP/SIGTSTP: Paused by user or netflash
*/
static void sigstop_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
{
touch(SYNC_STOPPED);
stopped++;
}
/*
* SIGCONT: Restart service monitor
*/
static void sigcont_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
{
stopped = 0;
erase(SYNC_STOPPED);
}
/*
* Is SIGSTOP asserted?
*/
int sig_stopped(void)
{
return stopped;
}
/*
* Inital signal setup - ignore everything but SIGCHLD until we're capable of responding
*/
static void chld_handler(int UNUSED(sig), siginfo_t *UNUSED(info), void *UNUSED(ctx))
{
/* NOP */
}
void sig_init(void)
{
int i;
struct sigaction sa;
for (i = 1; i < NSIG; i++)
IGNSIG(sa, i, SA_RESTART);
SETSIG(sa, SIGCHLD, chld_handler, SA_RESTART);
}
/*
* Unblock all signals blocked by finit when starting children
*/
void sig_unblock(void)
{
int i;
sigset_t nmask;
struct sigaction sa;
sigemptyset(&nmask);
sigaddset(&nmask, SIGCHLD);
sigaddset(&nmask, SIGINT);
sigaddset(&nmask, SIGPWR);
sigaddset(&nmask, SIGSTOP);
sigaddset(&nmask, SIGTSTP);
sigaddset(&nmask, SIGCONT);
sigprocmask(SIG_UNBLOCK, &nmask, NULL);
/* Reset signal handlers that were set by the parent process */
for (i = 1; i < NSIG; i++)
DFLSIG(sa, i, 0);
}
/*
* Setup limited set of SysV compatible signals to respond to
*/
void sig_setup(uev_ctx_t *ctx)
{
struct sigaction sa;
_d("Setup signals");
/* Cleanup any stale finit control files */
erase(SYNC_SHUTDOWN);
erase(SYNC_STOPPED);
/* Standard SysV init calls ctrl-alt-delete handler */
uev_signal_init(ctx, &sigint_watcher, sigint_cb, NULL, SIGINT);
uev_signal_init(ctx, &sigpwr_watcher, sigint_cb, NULL, SIGPWR);
/* Ignore SIGUSR1/2 for now, only BusyBox init implements them as reboot+halt. */
// uev_signal_init(&ctx, &sigusr1_watcher, reopen_initctl_cb, NULL, SIGUSR1);
// uev_signal_init(&ctx, &sigusr2_watcher, pwrdwn_cb, NULL, SIGUSR2);
/* Init must ignore SIGTERM. May otherwise get false SIGTERM in forked children! */
IGNSIG(sa, SIGTERM, 0);
/* Some C APIs may need SIGALRM for implementing timers. */
IGNSIG(sa, SIGALRM, 0);
/* /etc/inittab not supported yet, instead /etc/finit.d/ is scanned for *.conf */
uev_signal_init(ctx, &sighup_watcher, sighup_cb, NULL, SIGHUP);
/* After initial bootstrap of Finit we call the service monitor to reap children */
uev_signal_init(ctx, &sigchld_watcher, sigchld_cb, NULL, SIGCHLD);
/* Trap SIGSEGV in case service callbacks crash */
uev_signal_init(ctx, &sigsegv_watcher, sigsegv_cb, NULL, SIGSEGV);
/* Stopping init is a bit tricky. */
uev_signal_init(ctx, &sigstop_watcher, sigstop_cb, NULL, SIGSTOP);
uev_signal_init(ctx, &sigtstp_watcher, sigstop_cb, NULL, SIGTSTP);
uev_signal_init(ctx, &sigcont_watcher, sigcont_cb, NULL, SIGCONT);
/* Disable CTRL-ALT-DELETE from kernel, we handle shutdown gracefully with SIGINT, above */
reboot(RB_DISABLE_CAD);
setsid();
}
/**
* Local Variables:
* version-control: t
* indent-tabs-mode: t
* c-file-style: "linux"
* End:
*/