| /* oneit.c - tiny init replacement to launch a single child process. |
| * |
| * Copyright 2005, 2007 by Rob Landley <rob@landley.net>. |
| |
| USE_ONEIT(NEWTOY(oneit, "^<1nc:p3[!pn]", TOYFLAG_SBIN)) |
| |
| config ONEIT |
| bool "oneit" |
| default y |
| help |
| usage: oneit [-prn3] [-c CONSOLE] [COMMAND...] |
| |
| 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 |
| -r Restart child when it exits |
| -n No reboot, just relaunch command line |
| -3 Write 32 bit PID of each exiting reparented process to fd 3 of child |
| (Blocking writes, child must read to avoid eventual deadlock.) |
| |
| 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). |
| |
| Responds to SIGUSR1 by halting the system, SIGUSR2 by powering off, |
| and SIGTERM or SIGINT reboot. |
| */ |
| |
| #define FOR_oneit |
| #include "toys.h" |
| #include <sys/reboot.h> |
| |
| GLOBALS( |
| char *c; |
| ) |
| |
| // The minimum amount of work necessary to get ctrl-c and such to work is: |
| // |
| // - Fork a child (PID 1 is special: can't exit, has various signals blocked). |
| // - Do a setsid() (so we have our own session). |
| // - In the child, attach stdio to TT.c (/dev/console is special) |
| // - Exec the rest of the command line. |
| // |
| // 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 (getpid()!=1) _exit(127+signal); |
| if (!vfork()) reboot(action); |
| } |
| |
| void oneit_main(void) |
| { |
| int i, pid, pipes[] = {SIGUSR1, SIGUSR2, SIGTERM, SIGINT}; |
| char *ss = toybuf+5; |
| |
| // Setup signal handlers for signals of interest |
| for (i = 0; i<ARRAY_LEN(pipes); i++) xsignal(pipes[i], oneit_signaled); |
| |
| // Autodetect console from sysfs if no -c |
| memcpy(toybuf, "/dev/", 5); |
| i = sizeof(toybuf)-6; |
| if (!TT.c && (TT.c = readfile("/sys/class/tty/console/active", ss, i))) { |
| // Take last entry, remove newline terminator |
| while (TT.c[i = strcspn(TT.c, " \n")]) { |
| TT.c[i++] = 0; |
| if (TT.c[i]) TT.c += i; |
| else break; |
| } |
| // Ensure exactly one /dev prefix |
| strstart(&TT.c, "/dev/"); |
| memmove(toybuf+5, TT.c, strlen(TT.c)); |
| TT.c = toybuf; |
| } |
| |
| // Redirect stdin/out/err. Remember, O_CLOEXEC is backwards for xopen() |
| close(0); |
| xopen_stdio(TT.c ? : "/dev/tty0", O_RDWR|O_CLOEXEC); |
| close(1); |
| (void)dup(0); |
| close(2); |
| (void)dup(0); |
| |
| if (FLAG(3)) { |
| // Ensure next available filehandles are #3 and #4 |
| close(3); |
| close(4); |
| xpipe(pipes); |
| fcntl(4, F_SETFD, FD_CLOEXEC); |
| } |
| |
| while (!toys.signal) { |
| |
| // Create a new child process. |
| pid = XVFORK(); |
| 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 (FLAG(n)) continue; |
| |
| oneit_signaled(FLAG(p) ? SIGUSR2 : SIGTERM); |
| } else { |
| // new session ID in child, so ctrl-c works. |
| setsid(); |
| |
| // 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; |
| } |
| } |
| |
| // Give reboot() time to kick in, or avoid rapid spinning if exec failed |
| sleep(5); |
| _exit(127); |
| } |