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 static jmp_buf die_jmp;
73 static void jump(void)
75 /* Special case. We arrive here if NOFORK applet
76 * calls xfunc, which then decides to die.
77 * We don't die, but jump instead back to caller.
78 * NOFORK applets still cannot carelessly call xfuncs:
80 * q = xmalloc(10); // BUG! if this dies, we leak p!
82 /* | 0x100 allows to pass zero exitcode (longjmp can't pass 0).
83 * This works because exitcodes are bytes,
84 * run_nofork_applet() ensures that by "& 0xff" */
85 longjmp(die_jmp, xfunc_error_retval | 0x100);
88 struct nofork_save_area {
90 void (*die_func)(void);
91 const char *applet_name;
92 uint32_t option_mask32;
93 uint8_t xfunc_error_retval;
95 static void save_nofork_data(struct nofork_save_area *save)
97 memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
98 save->die_func = die_func;
99 save->applet_name = applet_name;
100 save->option_mask32 = option_mask32;
101 save->xfunc_error_retval = xfunc_error_retval;
103 static void restore_nofork_data(struct nofork_save_area *save)
105 memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
106 die_func = save->die_func;
107 applet_name = save->applet_name;
108 option_mask32 = save->option_mask32;
109 xfunc_error_retval = save->xfunc_error_retval;
112 int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
115 struct nofork_save_area old;
117 save_nofork_data(&old);
119 xfunc_error_retval = EXIT_FAILURE;
121 /* In case getopt() or getopt32() was already called:
122 * reset the libc getopt() function, which keeps internal state.
124 * BSD-derived getopt() functions require that optind be set to 1 in
125 * order to reset getopt() state. This used to be generally accepted
126 * way of resetting getopt(). However, glibc's getopt()
127 * has additional getopt() state beyond optind, and requires that
128 * optind be set to zero to reset its state. So the unfortunate state of
129 * affairs is that BSD-derived versions of getopt() misbehave if
130 * optind is set to 0 in order to reset getopt(), and glibc's getopt()
131 * will core dump if optind is set 1 in order to reset getopt().
133 * More modern versions of BSD require that optreset be set to 1 in
134 * order to reset getopt(). Sigh. Standards, anyone?
138 #else /* BSD style */
142 /* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
143 /* (values above are what they initialized to in glibc and uclibc) */
144 /* option_mask32 = 0; - not needed, no applet depends on it being 0 */
150 /* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */
152 rc = setjmp(die_jmp);
154 /* Some callers (xargs)
155 * need argv untouched because they free argv[i]! */
156 char *tmp_argv[argc+1];
157 memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
158 applet_name = tmp_argv[0];
159 /* Finally we can call NOFORK applet's main() */
160 rc = applet_main[applet_no](argc, tmp_argv);
162 /* xfunc died in NOFORK applet */
165 /* Restoring some globals */
166 restore_nofork_data(&old);
168 /* Other globals can be simply reset to defaults */
171 #else /* BSD style */
175 return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
177 #endif /* FEATURE_PREFER_APPLETS */
179 int FAST_FUNC spawn_and_wait(char **argv)
182 #if ENABLE_FEATURE_PREFER_APPLETS
183 int a = find_applet_by_name(argv[0]);
185 if (a >= 0 && (APPLET_IS_NOFORK(a)
187 || APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
191 if (APPLET_IS_NOFORK(a))
194 return run_nofork_applet(a, argv);
198 /* a->noexec is true */
200 if (rc) /* parent or error */
203 xfunc_error_retval = EXIT_FAILURE;
204 run_applet_no_and_exit(a, argv);
207 #endif /* FEATURE_PREFER_APPLETS */
213 void FAST_FUNC re_exec(char **argv)
215 /* high-order bit of first char in argv[0] is a hidden
216 * "we have (already) re-execed, don't do it again" flag */
218 execv(bb_busybox_exec_path, argv);
219 bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path);
222 pid_t FAST_FUNC fork_or_rexec(char **argv)
225 /* Maybe we are already re-execed and come here again? */
229 if (pid) /* parent */
231 /* child - re-exec ourself */
236 /* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
237 * char **argv "vanishes" */
238 void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
242 if (flags & DAEMON_CHDIR_ROOT)
245 if (flags & DAEMON_DEVNULL_STDIO) {
251 fd = open(bb_dev_null, O_RDWR);
253 /* NB: we can be called as bb_sanitize_stdio() from init
254 * or mdev, and there /dev/null may legitimately not (yet) exist!
255 * Do not use xopen above, but obtain _ANY_ open descriptor,
256 * even bogus one as below. */
257 fd = xopen("/", O_RDONLY); /* don't believe this can fail */
260 while ((unsigned)fd < 2)
261 fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
263 if (!(flags & DAEMON_ONLY_SANITIZE)) {
264 if (fork_or_rexec(argv))
265 exit(EXIT_SUCCESS); /* parent */
266 /* if daemonizing, detach from stdio & ctty */
271 if (flags & DAEMON_DOUBLE_FORK) {
272 /* On Linux, session leader can acquire ctty
273 * unknowingly, by opening a tty.
274 * Prevent this: stop being a session leader.
276 if (fork_or_rexec(argv))
277 exit(EXIT_SUCCESS); /* parent */
282 if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
284 /* else close everything after fd#2 */
288 void FAST_FUNC bb_sanitize_stdio(void)
290 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);