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.
17 #include <sys/prctl.h>
19 #define PR_SET_NAME 15
22 #define PR_GET_NAME 16
25 #include "busybox.h" /* uses applet tables */
26 #include "NUM_APPLETS.h"
28 #define NOFORK_SUPPORT ((NUM_APPLETS > 1) && (ENABLE_FEATURE_PREFER_APPLETS || ENABLE_FEATURE_SH_NOFORK))
29 #define NOEXEC_SUPPORT ((NUM_APPLETS > 1) && (ENABLE_FEATURE_PREFER_APPLETS || ENABLE_FEATURE_SH_STANDALONE))
31 #if defined(__linux__) && (NUM_APPLETS > 1)
32 void FAST_FUNC set_task_comm(const char *comm)
34 /* okay if too long (truncates) */
35 prctl(PR_SET_NAME, (long)comm, 0, 0, 0);
40 * NOFORK/NOEXEC support
43 static jmp_buf die_jmp;
44 static void jump(void)
46 /* Special case. We arrive here if NOFORK applet
47 * calls xfunc, which then decides to die.
48 * We don't die, but jump instead back to caller.
49 * NOFORK applets still cannot carelessly call xfuncs:
51 * q = xmalloc(10); // BUG! if this dies, we leak p!
53 /* | 0x100 allows to pass zero exitcode (longjmp can't pass 0).
54 * This works because exitcodes are bytes,
55 * run_nofork_applet() ensures that by "& 0xff" */
56 longjmp(die_jmp, xfunc_error_retval | 0x100);
59 struct nofork_save_area {
61 void (*die_func)(void);
62 const char *applet_name;
63 uint32_t option_mask32;
65 uint8_t xfunc_error_retval;
67 static void save_nofork_data(struct nofork_save_area *save)
69 memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
70 save->die_func = die_func;
71 save->applet_name = applet_name;
72 save->option_mask32 = option_mask32;
73 save->logmode = logmode;
74 save->xfunc_error_retval = xfunc_error_retval;
76 static void restore_nofork_data(struct nofork_save_area *save)
78 memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
79 die_func = save->die_func;
80 applet_name = save->applet_name;
81 option_mask32 = save->option_mask32;
82 logmode = save->logmode;
83 xfunc_error_retval = save->xfunc_error_retval;
86 int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
89 struct nofork_save_area old;
91 save_nofork_data(&old);
93 logmode = LOGMODE_STDIO;
94 xfunc_error_retval = EXIT_FAILURE;
95 /* In case getopt() or getopt32() was already called:
96 * reset the libc getopt() function, which keeps internal state.
99 //? applet_long_options = NULL;
100 //? opt_complementary = NULL;
102 argc = string_array_len(argv);
104 /* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */
106 rc = setjmp(die_jmp);
108 /* Some callers (xargs)
109 * need argv untouched because they free argv[i]! */
110 char *tmp_argv[argc+1];
111 memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
112 applet_name = tmp_argv[0];
113 /* Finally we can call NOFORK applet's main() */
114 rc = applet_main[applet_no](argc, tmp_argv);
115 /* Important for shells: `which CMD` was failing */
118 /* xfunc died in NOFORK applet */
121 /* Restoring some globals */
122 restore_nofork_data(&old);
123 /* Other globals can be simply reset to defaults */
125 //? applet_long_options = NULL;
126 //? opt_complementary = NULL;
128 return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
133 void FAST_FUNC run_noexec_applet_and_exit(int a, const char *name, char **argv)
135 /* reset some state and run without execing */
136 /* msg_eol = "\n"; - no caller needs this reinited yet */
137 logmode = LOGMODE_STDIO;
138 xfunc_error_retval = EXIT_FAILURE;
141 //? applet_long_options = NULL;
142 //? opt_complementary = NULL;
144 //TODO: think pidof, pgrep, pkill!
145 //set_task_comm() makes our pidof find NOEXECs (e.g. "yes >/dev/null"),
146 //but one from procps-ng-3.3.10 needs more!
147 //Rewrite /proc/PID/cmdline? (need to save argv0 and length at init for this to work!)
149 /* applet_name is set by this function: */
150 run_applet_no_and_exit(a, name, argv);
155 * Higher-level code, hiding optional NOFORK/NOEXEC trickery.
158 /* This does a fork/exec in one call, using vfork(). Returns PID of new child,
159 * -1 for failure. Runs argv[0], searching path if that has no / in it. */
160 pid_t FAST_FUNC spawn(char **argv)
162 /* Compiler should not optimize stores here */
168 /* Be nice to nommu machines. */
171 if (pid < 0) /* error */
173 if (!pid) { /* child */
174 /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
175 BB_EXECVP(argv[0], argv);
177 /* We are (maybe) sharing a stack with blocked parent,
178 * let parent know we failed and then exit to unblock parent
179 * (but don't run atexit() stuff, which would screw up parent.)
182 /* mount, for example, does not want the message */
183 /*bb_perror_msg("can't execute '%s'", argv[0]);*/
187 /* Unfortunately, this is not reliable: according to standards
188 * vfork() can be equivalent to fork() and we won't see value
190 * Interested party can wait on pid and learn exit code.
191 * If 111 - then it (most probably) failed to exec */
193 safe_waitpid(pid, NULL, 0); /* prevent zombie */
200 /* Die with an error message if we can't spawn a child process. */
201 pid_t FAST_FUNC xspawn(char **argv)
203 pid_t pid = spawn(argv);
205 bb_simple_perror_msg_and_die(*argv);
209 int FAST_FUNC spawn_and_wait(char **argv)
212 #if ENABLE_FEATURE_PREFER_APPLETS && (NUM_APPLETS > 1)
213 int a = find_applet_by_name(argv[0]);
216 if (APPLET_IS_NOFORK(a))
217 return run_nofork_applet(a, argv);
218 # if BB_MMU /* NOEXEC needs fork(), thus this is done only on MMU machines: */
219 if (APPLET_IS_NOEXEC(a)) {
222 if (rc) /* parent or error */
226 run_noexec_applet_and_exit(a, argv[0], argv);
236 void FAST_FUNC re_exec(char **argv)
238 /* high-order bit of first char in argv[0] is a hidden
239 * "we have (already) re-execed, don't do it again" flag */
241 execv(bb_busybox_exec_path, argv);
242 bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path);
245 pid_t FAST_FUNC fork_or_rexec(char **argv)
248 /* Maybe we are already re-execed and come here again? */
252 /* fflush_all(); ? - so far all callers had no buffered output to flush */
255 if (pid) /* parent */
257 /* child - re-exec ourself */
262 /* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
263 * char **argv "vanishes" */
264 void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
268 if (flags & DAEMON_CHDIR_ROOT)
271 if (flags & DAEMON_DEVNULL_STDIO) {
277 fd = open(bb_dev_null, O_RDWR);
279 /* NB: we can be called as bb_sanitize_stdio() from init
280 * or mdev, and there /dev/null may legitimately not (yet) exist!
281 * Do not use xopen above, but obtain _ANY_ open descriptor,
282 * even bogus one as below. */
283 fd = xopen("/", O_RDONLY); /* don't believe this can fail */
286 while ((unsigned)fd < 2)
287 fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
289 if (!(flags & DAEMON_ONLY_SANITIZE)) {
291 /* fflush_all(); - add it in fork_or_rexec() if necessary */
293 if (fork_or_rexec(argv))
294 _exit(EXIT_SUCCESS); /* parent */
295 /* if daemonizing, detach from stdio & ctty */
300 if (flags & DAEMON_DOUBLE_FORK) {
301 /* On Linux, session leader can acquire ctty
302 * unknowingly, by opening a tty.
303 * Prevent this: stop being a session leader.
305 if (fork_or_rexec(argv))
306 _exit(EXIT_SUCCESS); /* parent */
311 if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
313 /* else close everything after fd#2 */
317 void FAST_FUNC bb_sanitize_stdio(void)
319 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);