*
* Copyright 2005, 2007 by Rob Landley <rob@landley.net>.
-USE_ONEIT(NEWTOY(oneit, "^<1c:p", TOYFLAG_SBIN))
+USE_ONEIT(NEWTOY(oneit, "^<1nc:p3[!pn]", TOYFLAG_SBIN))
config ONEIT
bool "oneit"
help
usage: oneit [-p] [-c /dev/tty0] command [...]
- A simple init program that runs a single supplied command line with a
+ Simple init program that runs a single supplied command line with a
controlling tty (so CTRL-C can kill it).
+ -c Which console device to use (/dev/console doesn't do CTRL-C, etc).
-p Power off instead of rebooting when command exits.
- -c Which console device to use.
+ -r Restart child when it exits.
+ -3 Write 32 bit PID of each exiting reparented process to fd 3 of child.
+ (Blocking writes, child must read to avoid eventual deadlock.)
- The oneit command runs the supplied command line as a child process
- (because PID 1 has signals blocked), attached to /dev/tty0, in its
- own session. Then oneit reaps zombies until the child exits, at
- which point it reboots (or with -p, powers off) the system.
+ Spawns a single child process (because PID 1 has signals blocked)
+ in its own session, reaps zombies until the child exits, then
+ reboots the system (or powers off with -p, or restarts the child with -r).
*/
#define FOR_oneit
// PID 1 then reaps zombies until the child process it spawned exits, at which
// point it calls sync() and reboot(). I could stick a kill -1 in there.
+// Perform actions in response to signals. (Only root can send us signals.)
+static void oneit_signaled(int signal)
+{
+ int action = RB_AUTOBOOT;
+
+ toys.signal = signal;
+ if (signal == SIGUSR1) action = RB_HALT_SYSTEM;
+ if (signal == SIGUSR2) action = RB_POWER_OFF;
+
+ // PID 1 can't call reboot() because it kills the task that calls it,
+ // which causes the kernel to panic before the actual reboot happens.
+ sync();
+ if (!vfork()) reboot(action);
+}
void oneit_main(void)
{
- int i;
- pid_t pid;
-
- // Create a new child process.
- pid = vfork();
- if (pid) {
-
- // pid 1 just reaps zombies until it gets its child, then halts the system.
- while (pid != wait(&i));
- sync();
-
- // PID 1 can't call reboot() because it kills the task that calls it,
- // which causes the kernel to panic before the actual reboot happens.
- if (!vfork()) reboot((toys.optflags & FLAG_p) ? RB_POWER_OFF : RB_AUTOBOOT);
- sleep(5);
- _exit(1);
+ int i, pid, pipes[] = {SIGUSR1, SIGUSR2, SIGTERM, SIGINT};
+
+ if (FLAG_3) {
+ // Ensure next available filehandle is #3
+ while (open("/", 0) < 3);
+ close(3);
+ close(4);
+ if (pipe(pipes)) perror_exit("pipe");
+ fcntl(4, F_SETFD, FD_CLOEXEC);
}
- // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
- setsid();
- for (i=0; i<3; i++) {
- close(i);
- // Remember, O_CLOEXEC is backwards for xopen()
- xopen(TT.console ? TT.console : "/dev/tty0", O_RDWR|O_CLOEXEC);
+ // Setup signal handlers for signals of interest
+ for (i = 0; i<ARRAY_LEN(pipes); i++) xsignal(pipes[i], oneit_signaled);
+
+ while (!toys.signal) {
+
+ // Create a new child process.
+ pid = vfork();
+ if (pid) {
+
+ // pid 1 reaps zombies until it gets its child, then halts system.
+ // We ignore the return value of write (what would we do with it?)
+ // but save it in a variable we never read to make fortify shut up.
+ // (Real problem is if pid2 never reads, write() fills pipe and blocks.)
+ while (pid != wait(&i)) if (FLAG_3) i = write(4, &pid, 4);
+ if (toys.optflags & FLAG_n) continue;
+
+ oneit_signaled((toys.optflags & FLAG_p) ? SIGUSR2 : SIGTERM);
+ } else {
+ // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works.
+ setsid();
+ for (i=0; i<3; i++) {
+ close(i);
+ // Remember, O_CLOEXEC is backwards for xopen()
+ xopen(TT.console ? TT.console : "/dev/tty0", O_RDWR|O_CLOEXEC);
+ }
+
+ // Can't xexec() here, we vforked so we don't want to error_exit().
+ toy_exec(toys.optargs);
+ execvp(*toys.optargs, toys.optargs);
+ perror_msg("%s not in PATH=%s", *toys.optargs, getenv("PATH"));
+
+ break;
+ }
}
- // Can't xexec() here, because we vforked so we don't want to error_exit().
- toy_exec(toys.optargs);
- execvp(*toys.optargs, toys.optargs);
+ // Give reboot() time to kick in, or avoid rapid spinning if exec failed
+ sleep(5);
_exit(127);
}