| /* vi: set sw=4 ts=4: */ |
| /* |
| * Rexec program for system have fork() as vfork() with foreground option |
| * |
| * Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru> |
| * Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu> |
| * |
| * daemon() portion taken from uClibc: |
| * |
| * Copyright (c) 1991, 1993 |
| * The Regents of the University of California. All rights reserved. |
| * |
| * Modified for uClibc by Erik Andersen <andersee@debian.org> |
| * |
| * Licensed under GPLv2 or later, see file LICENSE in this source tree. |
| */ |
| |
| #include "busybox.h" /* uses applet tables */ |
| #include "NUM_APPLETS.h" |
| |
| /* This does a fork/exec in one call, using vfork(). Returns PID of new child, |
| * -1 for failure. Runs argv[0], searching path if that has no / in it. */ |
| pid_t FAST_FUNC spawn(char **argv) |
| { |
| /* Compiler should not optimize stores here */ |
| volatile int failed; |
| pid_t pid; |
| |
| fflush_all(); |
| |
| /* Be nice to nommu machines. */ |
| failed = 0; |
| pid = vfork(); |
| if (pid < 0) /* error */ |
| return pid; |
| if (!pid) { /* child */ |
| /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */ |
| BB_EXECVP(argv[0], argv); |
| |
| /* We are (maybe) sharing a stack with blocked parent, |
| * let parent know we failed and then exit to unblock parent |
| * (but don't run atexit() stuff, which would screw up parent.) |
| */ |
| failed = errno; |
| /* mount, for example, does not want the message */ |
| /*bb_perror_msg("can't execute '%s'", argv[0]);*/ |
| _exit(111); |
| } |
| /* parent */ |
| /* Unfortunately, this is not reliable: according to standards |
| * vfork() can be equivalent to fork() and we won't see value |
| * of 'failed'. |
| * Interested party can wait on pid and learn exit code. |
| * If 111 - then it (most probably) failed to exec */ |
| if (failed) { |
| safe_waitpid(pid, NULL, 0); /* prevent zombie */ |
| errno = failed; |
| return -1; |
| } |
| return pid; |
| } |
| |
| /* Die with an error message if we can't spawn a child process. */ |
| pid_t FAST_FUNC xspawn(char **argv) |
| { |
| pid_t pid = spawn(argv); |
| if (pid < 0) |
| bb_simple_perror_msg_and_die(*argv); |
| return pid; |
| } |
| |
| #if ENABLE_FEATURE_PREFER_APPLETS \ |
| || ENABLE_FEATURE_SH_NOFORK |
| static jmp_buf die_jmp; |
| static void jump(void) |
| { |
| /* Special case. We arrive here if NOFORK applet |
| * calls xfunc, which then decides to die. |
| * We don't die, but jump instead back to caller. |
| * NOFORK applets still cannot carelessly call xfuncs: |
| * p = xmalloc(10); |
| * q = xmalloc(10); // BUG! if this dies, we leak p! |
| */ |
| /* | 0x100 allows to pass zero exitcode (longjmp can't pass 0). |
| * This works because exitcodes are bytes, |
| * run_nofork_applet() ensures that by "& 0xff" */ |
| longjmp(die_jmp, xfunc_error_retval | 0x100); |
| } |
| |
| struct nofork_save_area { |
| jmp_buf die_jmp; |
| void (*die_func)(void); |
| const char *applet_name; |
| uint32_t option_mask32; |
| uint8_t xfunc_error_retval; |
| }; |
| static void save_nofork_data(struct nofork_save_area *save) |
| { |
| memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp)); |
| save->die_func = die_func; |
| save->applet_name = applet_name; |
| save->option_mask32 = option_mask32; |
| save->xfunc_error_retval = xfunc_error_retval; |
| } |
| static void restore_nofork_data(struct nofork_save_area *save) |
| { |
| memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp)); |
| die_func = save->die_func; |
| applet_name = save->applet_name; |
| option_mask32 = save->option_mask32; |
| xfunc_error_retval = save->xfunc_error_retval; |
| } |
| |
| int FAST_FUNC run_nofork_applet(int applet_no, char **argv) |
| { |
| int rc, argc; |
| struct nofork_save_area old; |
| |
| save_nofork_data(&old); |
| |
| xfunc_error_retval = EXIT_FAILURE; |
| |
| /* In case getopt() or getopt32() was already called: |
| * reset the libc getopt() function, which keeps internal state. |
| */ |
| GETOPT_RESET(); |
| |
| argc = 1; |
| while (argv[argc]) |
| argc++; |
| |
| /* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */ |
| die_func = jump; |
| rc = setjmp(die_jmp); |
| if (!rc) { |
| /* Some callers (xargs) |
| * need argv untouched because they free argv[i]! */ |
| char *tmp_argv[argc+1]; |
| memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0])); |
| applet_name = tmp_argv[0]; |
| /* Finally we can call NOFORK applet's main() */ |
| rc = applet_main[applet_no](argc, tmp_argv); |
| } else { |
| /* xfunc died in NOFORK applet */ |
| } |
| |
| /* Restoring some globals */ |
| restore_nofork_data(&old); |
| |
| /* Other globals can be simply reset to defaults */ |
| GETOPT_RESET(); |
| |
| return rc & 0xff; /* don't confuse people with "exitcodes" >255 */ |
| } |
| #endif /* FEATURE_PREFER_APPLETS || FEATURE_SH_NOFORK */ |
| |
| int FAST_FUNC spawn_and_wait(char **argv) |
| { |
| int rc; |
| #if ENABLE_FEATURE_PREFER_APPLETS && (NUM_APPLETS > 1) |
| int a = find_applet_by_name(argv[0]); |
| |
| if (a >= 0) { |
| if (APPLET_IS_NOFORK(a)) |
| return run_nofork_applet(a, argv); |
| # if BB_MMU /* NOEXEC needs fork(), thus this is done only on MMU machines: */ |
| if (APPLET_IS_NOEXEC(a)) { |
| fflush_all(); |
| rc = fork(); |
| if (rc) /* parent or error */ |
| return wait4pid(rc); |
| |
| /* child */ |
| /* reset some state and run without execing */ |
| |
| /* msg_eol = "\n"; - no caller needs this reinited yet */ |
| logmode = LOGMODE_STDIO; |
| /* die_func = NULL; - needed if the caller is a shell, |
| * init, or a NOFORK applet. But none of those call us |
| * as of yet (and that should probably always stay true). |
| */ |
| /* xfunc_error_retval and applet_name are init by: */ |
| run_applet_no_and_exit(a, argv); |
| } |
| # endif |
| } |
| #endif /* FEATURE_PREFER_APPLETS */ |
| rc = spawn(argv); |
| return wait4pid(rc); |
| } |
| |
| #if !BB_MMU |
| void FAST_FUNC re_exec(char **argv) |
| { |
| /* high-order bit of first char in argv[0] is a hidden |
| * "we have (already) re-execed, don't do it again" flag */ |
| argv[0][0] |= 0x80; |
| execv(bb_busybox_exec_path, argv); |
| bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path); |
| } |
| |
| pid_t FAST_FUNC fork_or_rexec(char **argv) |
| { |
| pid_t pid; |
| /* Maybe we are already re-execed and come here again? */ |
| if (re_execed) |
| return 0; |
| pid = xvfork(); |
| if (pid) /* parent */ |
| return pid; |
| /* child - re-exec ourself */ |
| re_exec(argv); |
| } |
| #endif |
| |
| /* Due to a #define in libbb.h on MMU systems we actually have 1 argument - |
| * char **argv "vanishes" */ |
| void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv) |
| { |
| int fd; |
| |
| if (flags & DAEMON_CHDIR_ROOT) |
| xchdir("/"); |
| |
| if (flags & DAEMON_DEVNULL_STDIO) { |
| close(0); |
| close(1); |
| close(2); |
| } |
| |
| fd = open(bb_dev_null, O_RDWR); |
| if (fd < 0) { |
| /* NB: we can be called as bb_sanitize_stdio() from init |
| * or mdev, and there /dev/null may legitimately not (yet) exist! |
| * Do not use xopen above, but obtain _ANY_ open descriptor, |
| * even bogus one as below. */ |
| fd = xopen("/", O_RDONLY); /* don't believe this can fail */ |
| } |
| |
| while ((unsigned)fd < 2) |
| fd = dup(fd); /* have 0,1,2 open at least to /dev/null */ |
| |
| if (!(flags & DAEMON_ONLY_SANITIZE)) { |
| if (fork_or_rexec(argv)) |
| exit(EXIT_SUCCESS); /* parent */ |
| /* if daemonizing, detach from stdio & ctty */ |
| setsid(); |
| dup2(fd, 0); |
| dup2(fd, 1); |
| dup2(fd, 2); |
| if (flags & DAEMON_DOUBLE_FORK) { |
| /* On Linux, session leader can acquire ctty |
| * unknowingly, by opening a tty. |
| * Prevent this: stop being a session leader. |
| */ |
| if (fork_or_rexec(argv)) |
| exit(EXIT_SUCCESS); /* parent */ |
| } |
| } |
| while (fd > 2) { |
| close(fd--); |
| if (!(flags & DAEMON_CLOSE_EXTRA_FDS)) |
| return; |
| /* else close everything after fd#2 */ |
| } |
| } |
| |
| void FAST_FUNC bb_sanitize_stdio(void) |
| { |
| bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL); |
| } |