1 /* vi: set sw=4 ts=4: */
3 * Rexec program for system have fork() as vfork() with foreground option
5 * Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru>
6 * Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu>
8 * daemon() portion taken from uClibc:
10 * Copyright (c) 1991, 1993
11 * The Regents of the University of California. All rights reserved.
13 * Modified for uClibc by Erik Andersen <andersee@debian.org>
15 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
18 #include "busybox.h" /* uses applet tables */
20 /* This does a fork/exec in one call, using vfork(). Returns PID of new child,
21 * -1 for failure. Runs argv[0], searching path if that has no / in it. */
22 pid_t FAST_FUNC spawn(char **argv)
24 /* Compiler should not optimize stores here */
30 /* Be nice to nommu machines. */
33 if (pid < 0) /* error */
35 if (!pid) { /* child */
36 /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
37 BB_EXECVP(argv[0], argv);
39 /* We are (maybe) sharing a stack with blocked parent,
40 * let parent know we failed and then exit to unblock parent
41 * (but don't run atexit() stuff, which would screw up parent.)
44 /* mount, for example, does not want the message */
45 /*bb_perror_msg("can't execute '%s'", argv[0]);*/
49 /* Unfortunately, this is not reliable: according to standards
50 * vfork() can be equivalent to fork() and we won't see value
52 * Interested party can wait on pid and learn exit code.
53 * If 111 - then it (most probably) failed to exec */
55 safe_waitpid(pid, NULL, 0); /* prevent zombie */
62 /* Die with an error message if we can't spawn a child process. */
63 pid_t FAST_FUNC xspawn(char **argv)
65 pid_t pid = spawn(argv);
67 bb_simple_perror_msg_and_die(*argv);
71 #if ENABLE_FEATURE_PREFER_APPLETS \
72 || ENABLE_FEATURE_SH_NOFORK
73 static jmp_buf die_jmp;
74 static void jump(void)
76 /* Special case. We arrive here if NOFORK applet
77 * calls xfunc, which then decides to die.
78 * We don't die, but jump instead back to caller.
79 * NOFORK applets still cannot carelessly call xfuncs:
81 * q = xmalloc(10); // BUG! if this dies, we leak p!
83 /* | 0x100 allows to pass zero exitcode (longjmp can't pass 0).
84 * This works because exitcodes are bytes,
85 * run_nofork_applet() ensures that by "& 0xff" */
86 longjmp(die_jmp, xfunc_error_retval | 0x100);
89 struct nofork_save_area {
91 void (*die_func)(void);
92 const char *applet_name;
93 uint32_t option_mask32;
94 uint8_t xfunc_error_retval;
96 static void save_nofork_data(struct nofork_save_area *save)
98 memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
99 save->die_func = die_func;
100 save->applet_name = applet_name;
101 save->option_mask32 = option_mask32;
102 save->xfunc_error_retval = xfunc_error_retval;
104 static void restore_nofork_data(struct nofork_save_area *save)
106 memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
107 die_func = save->die_func;
108 applet_name = save->applet_name;
109 option_mask32 = save->option_mask32;
110 xfunc_error_retval = save->xfunc_error_retval;
113 int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
116 struct nofork_save_area old;
118 save_nofork_data(&old);
120 xfunc_error_retval = EXIT_FAILURE;
122 /* In case getopt() or getopt32() was already called:
123 * reset the libc getopt() function, which keeps internal state.
125 * BSD-derived getopt() functions require that optind be set to 1 in
126 * order to reset getopt() state. This used to be generally accepted
127 * way of resetting getopt(). However, glibc's getopt()
128 * has additional getopt() state beyond optind, and requires that
129 * optind be set to zero to reset its state. So the unfortunate state of
130 * affairs is that BSD-derived versions of getopt() misbehave if
131 * optind is set to 0 in order to reset getopt(), and glibc's getopt()
132 * will core dump if optind is set 1 in order to reset getopt().
134 * More modern versions of BSD require that optreset be set to 1 in
135 * order to reset getopt(). Sigh. Standards, anyone?
139 #else /* BSD style */
143 /* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
144 /* (values above are what they initialized to in glibc and uclibc) */
145 /* option_mask32 = 0; - not needed, no applet depends on it being 0 */
151 /* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */
153 rc = setjmp(die_jmp);
155 /* Some callers (xargs)
156 * need argv untouched because they free argv[i]! */
157 char *tmp_argv[argc+1];
158 memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
159 applet_name = tmp_argv[0];
160 /* Finally we can call NOFORK applet's main() */
161 rc = applet_main[applet_no](argc, tmp_argv);
163 /* xfunc died in NOFORK applet */
166 /* Restoring some globals */
167 restore_nofork_data(&old);
169 /* Other globals can be simply reset to defaults */
172 #else /* BSD style */
176 return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
178 #endif /* FEATURE_PREFER_APPLETS || FEATURE_SH_NOFORK */
180 int FAST_FUNC spawn_and_wait(char **argv)
183 #if ENABLE_FEATURE_PREFER_APPLETS
184 int a = find_applet_by_name(argv[0]);
187 if (APPLET_IS_NOFORK(a))
188 return run_nofork_applet(a, argv);
189 # if BB_MMU /* NOEXEC needs fork(), thus this is done only on MMU machines: */
190 if (APPLET_IS_NOEXEC(a)) {
193 if (rc) /* parent or error */
197 /* reset some state and run without execing */
199 /* msg_eol = "\n"; - no caller needs this reinited yet */
200 logmode = LOGMODE_STDIO;
201 /* die_func = NULL; - needed if the caller is a shell,
202 * init, or a NOFORK applet. But none of those call us
203 * as of yet (and that should probably always stay true).
205 /* xfunc_error_retval and applet_name are init by: */
206 run_applet_no_and_exit(a, argv);
210 #endif /* FEATURE_PREFER_APPLETS */
216 void FAST_FUNC re_exec(char **argv)
218 /* high-order bit of first char in argv[0] is a hidden
219 * "we have (already) re-execed, don't do it again" flag */
221 execv(bb_busybox_exec_path, argv);
222 bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path);
225 pid_t FAST_FUNC fork_or_rexec(char **argv)
228 /* Maybe we are already re-execed and come here again? */
232 if (pid) /* parent */
234 /* child - re-exec ourself */
239 /* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
240 * char **argv "vanishes" */
241 void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
245 if (flags & DAEMON_CHDIR_ROOT)
248 if (flags & DAEMON_DEVNULL_STDIO) {
254 fd = open(bb_dev_null, O_RDWR);
256 /* NB: we can be called as bb_sanitize_stdio() from init
257 * or mdev, and there /dev/null may legitimately not (yet) exist!
258 * Do not use xopen above, but obtain _ANY_ open descriptor,
259 * even bogus one as below. */
260 fd = xopen("/", O_RDONLY); /* don't believe this can fail */
263 while ((unsigned)fd < 2)
264 fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
266 if (!(flags & DAEMON_ONLY_SANITIZE)) {
267 if (fork_or_rexec(argv))
268 exit(EXIT_SUCCESS); /* parent */
269 /* if daemonizing, detach from stdio & ctty */
274 if (flags & DAEMON_DOUBLE_FORK) {
275 /* On Linux, session leader can acquire ctty
276 * unknowingly, by opening a tty.
277 * Prevent this: stop being a session leader.
279 if (fork_or_rexec(argv))
280 exit(EXIT_SUCCESS); /* parent */
285 if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
287 /* else close everything after fd#2 */
291 void FAST_FUNC bb_sanitize_stdio(void)
293 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);