busybox/libbb/vfork_daemon_rexec.c

/* 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 tarball for details.
 */

#include <paths.h>
#include "busybox.h" /* uses applet tables */

/* 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;

// Ain't it a good place to fflush(NULL)?

	/* 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;
		_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) {
		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;
}

pid_t FAST_FUNC safe_waitpid(pid_t pid, int *wstat, int options)
{
	pid_t r;

	do
		r = waitpid(pid, wstat, options);
	while ((r == -1) && (errno == EINTR));
	return r;
}

pid_t FAST_FUNC wait_any_nohang(int *wstat)
{
	return safe_waitpid(-1, wstat, WNOHANG);
}

// Wait for the specified child PID to exit, returning child's error return.
int FAST_FUNC wait4pid(pid_t pid)
{
	int status;

	if (pid <= 0) {
		/*errno = ECHILD; -- wrong. */
		/* we expect errno to be already set from failed [v]fork/exec */
		return -1;
	}
	if (safe_waitpid(pid, &status, 0) == -1)
		return -1;
	if (WIFEXITED(status))
		return WEXITSTATUS(status);
	if (WIFSIGNALED(status))
		return WTERMSIG(status) + 1000;
	return 0;
}

#if ENABLE_FEATURE_PREFER_APPLETS
void FAST_FUNC save_nofork_data(struct nofork_save_area *save)
{
	memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
	save->applet_name = applet_name;
	save->xfunc_error_retval = xfunc_error_retval;
	save->option_mask32 = option_mask32;
	save->die_sleep = die_sleep;
	save->saved = 1;
}

void FAST_FUNC restore_nofork_data(struct nofork_save_area *save)
{
	memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
	applet_name = save->applet_name;
	xfunc_error_retval = save->xfunc_error_retval;
	option_mask32 = save->option_mask32;
	die_sleep = save->die_sleep;
}

int FAST_FUNC run_nofork_applet_prime(struct nofork_save_area *old, int applet_no, char **argv)
{
	int rc, argc;

	applet_name = APPLET_NAME(applet_no);

	xfunc_error_retval = EXIT_FAILURE;

	/* Special flag for xfunc_die(). If xfunc will "die"
	 * in NOFORK applet, xfunc_die() sees negative
	 * die_sleep and longjmp here instead. */
	die_sleep = -1;

	/* In case getopt() or getopt32() was already called:
	 * reset the libc getopt() function, which keeps internal state.
	 *
	 * BSD-derived getopt() functions require that optind be set to 1 in
	 * order to reset getopt() state.  This used to be generally accepted
	 * way of resetting getopt().  However, glibc's getopt()
	 * has additional getopt() state beyond optind, and requires that
	 * optind be set to zero to reset its state.  So the unfortunate state of
	 * affairs is that BSD-derived versions of getopt() misbehave if
	 * optind is set to 0 in order to reset getopt(), and glibc's getopt()
	 * will core dump if optind is set 1 in order to reset getopt().
	 *
	 * More modern versions of BSD require that optreset be set to 1 in
	 * order to reset getopt().  Sigh.  Standards, anyone?
	 */
#ifdef __GLIBC__
	optind = 0;
#else /* BSD style */
	optind = 1;
	/* optreset = 1; */
#endif
	/* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
	/* (values above are what they initialized to in glibc and uclibc) */
	/* option_mask32 = 0; - not needed, no applet depends on it being 0 */

	argc = 1;
	while (argv[argc])
		argc++;

	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]));
		/* Finally we can call NOFORK applet's main() */
		rc = applet_main[applet_no](argc, tmp_argv);

	/* The whole reason behind nofork_save_area is that <applet>_main
	 * may exit non-locally! For example, in hush Ctrl-Z tries
	 * (modulo bugs) to dynamically create a child (backgrounded task)
	 * if it detects that Ctrl-Z was pressed when a NOFORK was running.
	 * Testcase: interactive "rm -i".
	 * Don't fool yourself into thinking "and <applet>_main() returns
	 * quickly here" and removing "useless" nofork_save_area code. */

	} else { /* xfunc died in NOFORK applet */
		/* in case they meant to return 0... */
		if (rc == -2222)
			rc = 0;
	}

	/* Restoring some globals */
	restore_nofork_data(old);

	/* Other globals can be simply reset to defaults */
#ifdef __GLIBC__
	optind = 0;
#else /* BSD style */
	optind = 1;
#endif

	return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
}

int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
{
	struct nofork_save_area old;

	/* Saving globals */
	save_nofork_data(&old);
	return run_nofork_applet_prime(&old, applet_no, argv);
}
#endif /* FEATURE_PREFER_APPLETS */

int FAST_FUNC spawn_and_wait(char **argv)
{
	int rc;
#if ENABLE_FEATURE_PREFER_APPLETS
	int a = find_applet_by_name(argv[0]);

	if (a >= 0 && (APPLET_IS_NOFORK(a)
#if BB_MMU
			|| APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
#endif
	)) {
#if BB_MMU
		if (APPLET_IS_NOFORK(a))
#endif
		{
			return run_nofork_applet(a, argv);
		}
#if BB_MMU
		/* MMU only */
		/* a->noexec is true */
		rc = fork();
		if (rc) /* parent or error */
			return wait4pid(rc);
		/* child */
		xfunc_error_retval = EXIT_FAILURE;
		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("exec %s", bb_busybox_exec_path);
}

void FAST_FUNC forkexit_or_rexec(char **argv)
{
	pid_t pid;
	/* Maybe we are already re-execed and come here again? */
	if (re_execed)
		return;

	pid = vfork();
	if (pid < 0) /* wtf? */
		bb_perror_msg_and_die("vfork");
	if (pid) /* parent */
		exit(EXIT_SUCCESS);
	/* child - re-exec ourself */
	re_exec(argv);
}
#else
/* Dance around (void)...*/
#undef forkexit_or_rexec
void FAST_FUNC forkexit_or_rexec(void)
{
	pid_t pid;
	pid = fork();
	if (pid < 0) /* wtf? */
		bb_perror_msg_and_die("fork");
	if (pid) /* parent */
		exit(EXIT_SUCCESS);
	/* child */
}
#define forkexit_or_rexec(argv) forkexit_or_rexec()
#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)) {
		forkexit_or_rexec(argv);
		/* if daemonizing, make sure we detach from stdio & ctty */
		setsid();
		dup2(fd, 0);
		dup2(fd, 1);
		dup2(fd, 2);
	}
	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);
}
1	/* vi: set sw=4 ts=4: */
2	/*
3	* Rexec program for system have fork() as vfork() with foreground option
4	*
5	* Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru>
6	* Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu>
7	*
8	* daemon() portion taken from uClibc:
9	*
10	* Copyright (c) 1991, 1993
11	* The Regents of the University of California. All rights reserved.
12	*
13	* Modified for uClibc by Erik Andersen <andersee@debian.org>
14	*
15	* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
16	*/
17
18	#include <paths.h>
19	#include "busybox.h" /* uses applet tables */
20
21	/* This does a fork/exec in one call, using vfork(). Returns PID of new child,
22	* -1 for failure. Runs argv[0], searching path if that has no / in it. */
23	pid_t FAST_FUNC spawn(char **argv)
24	{
25	/* Compiler should not optimize stores here */
26	volatile int failed;
27	pid_t pid;
28
29	// Ain't it a good place to fflush(NULL)?
30
31	/* Be nice to nommu machines. */
32	failed = 0;
33	pid = vfork();
34	if (pid < 0) /* error */
35	return pid;
36	if (!pid) { /* child */
37	/* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
38	BB_EXECVP(argv[0], argv);
39
40	/* We are (maybe) sharing a stack with blocked parent,
41	* let parent know we failed and then exit to unblock parent
42	* (but don't run atexit() stuff, which would screw up parent.)
43	*/
44	failed = errno;
45	_exit(111);
46	}
47	/* parent */
48	/* Unfortunately, this is not reliable: according to standards
49	* vfork() can be equivalent to fork() and we won't see value
50	* of 'failed'.
51	* Interested party can wait on pid and learn exit code.
52	* If 111 - then it (most probably) failed to exec */
53	if (failed) {
54	errno = failed;
55	return -1;
56	}
57	return pid;
58	}
59
60	/* Die with an error message if we can't spawn a child process. */
61	pid_t FAST_FUNC xspawn(char **argv)
62	{
63	pid_t pid = spawn(argv);
64	if (pid < 0)
65	bb_simple_perror_msg_and_die(*argv);
66	return pid;
67	}
68
69	pid_t FAST_FUNC safe_waitpid(pid_t pid, int *wstat, int options)
70	{
71	pid_t r;
72
73	do
74	r = waitpid(pid, wstat, options);
75	while ((r == -1) && (errno == EINTR));
76	return r;
77	}
78
79	pid_t FAST_FUNC wait_any_nohang(int *wstat)
80	{
81	return safe_waitpid(-1, wstat, WNOHANG);
82	}
83
84	// Wait for the specified child PID to exit, returning child's error return.
85	int FAST_FUNC wait4pid(pid_t pid)
86	{
87	int status;
88
89	if (pid <= 0) {
90	/errno = ECHILD; -- wrong. /
91	/* we expect errno to be already set from failed [v]fork/exec */
92	return -1;
93	}
94	if (safe_waitpid(pid, &status, 0) == -1)
95	return -1;
96	if (WIFEXITED(status))
97	return WEXITSTATUS(status);
98	if (WIFSIGNALED(status))
99	return WTERMSIG(status) + 1000;
100	return 0;
101	}
102
103	#if ENABLE_FEATURE_PREFER_APPLETS
104	void FAST_FUNC save_nofork_data(struct nofork_save_area *save)
105	{
106	memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
107	save->applet_name = applet_name;
108	save->xfunc_error_retval = xfunc_error_retval;
109	save->option_mask32 = option_mask32;
110	save->die_sleep = die_sleep;
111	save->saved = 1;
112	}
113
114	void FAST_FUNC restore_nofork_data(struct nofork_save_area *save)
115	{
116	memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
117	applet_name = save->applet_name;
118	xfunc_error_retval = save->xfunc_error_retval;
119	option_mask32 = save->option_mask32;
120	die_sleep = save->die_sleep;
121	}
122
123	int FAST_FUNC run_nofork_applet_prime(struct nofork_save_area old, int applet_no, char *argv)
124	{
125	int rc, argc;
126
127	applet_name = APPLET_NAME(applet_no);
128
129	xfunc_error_retval = EXIT_FAILURE;
130
131	/* Special flag for xfunc_die(). If xfunc will "die"
132	* in NOFORK applet, xfunc_die() sees negative
133	* die_sleep and longjmp here instead. */
134	die_sleep = -1;
135
136	/* In case getopt() or getopt32() was already called:
137	* reset the libc getopt() function, which keeps internal state.
138	*
139	* BSD-derived getopt() functions require that optind be set to 1 in
140	* order to reset getopt() state. This used to be generally accepted
141	* way of resetting getopt(). However, glibc's getopt()
142	* has additional getopt() state beyond optind, and requires that
143	* optind be set to zero to reset its state. So the unfortunate state of
144	* affairs is that BSD-derived versions of getopt() misbehave if
145	* optind is set to 0 in order to reset getopt(), and glibc's getopt()
146	* will core dump if optind is set 1 in order to reset getopt().
147	*
148	* More modern versions of BSD require that optreset be set to 1 in
149	* order to reset getopt(). Sigh. Standards, anyone?
150	*/
151	#ifdef __GLIBC__
152	optind = 0;
153	#else /* BSD style */
154	optind = 1;
155	/* optreset = 1; */
156	#endif
157	/* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
158	/* (values above are what they initialized to in glibc and uclibc) */
159	/* option_mask32 = 0; - not needed, no applet depends on it being 0 */
160
161	argc = 1;
162	while (argv[argc])
163	argc++;
164
165	rc = setjmp(die_jmp);
166	if (!rc) {
167	/* Some callers (xargs)
168	* need argv untouched because they free argv[i]! */
169	char *tmp_argv[argc+1];
170	memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
171	/* Finally we can call NOFORK applet's main() */
172	rc = applet_main[applet_no](argc, tmp_argv);
173
174	/* The whole reason behind nofork_save_area is that <applet>_main
175	* may exit non-locally! For example, in hush Ctrl-Z tries
176	* (modulo bugs) to dynamically create a child (backgrounded task)
177	* if it detects that Ctrl-Z was pressed when a NOFORK was running.
178	* Testcase: interactive "rm -i".
179	* Don't fool yourself into thinking "and <applet>_main() returns
180	* quickly here" and removing "useless" nofork_save_area code. */
181
182	} else { /* xfunc died in NOFORK applet */
183	/* in case they meant to return 0... */
184	if (rc == -2222)
185	rc = 0;
186	}
187
188	/* Restoring some globals */
189	restore_nofork_data(old);
190
191	/* Other globals can be simply reset to defaults */
192	#ifdef __GLIBC__
193	optind = 0;
194	#else /* BSD style */
195	optind = 1;
196	#endif
197
198	return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
199	}
200
201	int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
202	{
203	struct nofork_save_area old;
204
205	/* Saving globals */
206	save_nofork_data(&old);
207	return run_nofork_applet_prime(&old, applet_no, argv);
208	}
209	#endif /* FEATURE_PREFER_APPLETS */
210
211	int FAST_FUNC spawn_and_wait(char **argv)
212	{
213	int rc;
214	#if ENABLE_FEATURE_PREFER_APPLETS
215	int a = find_applet_by_name(argv[0]);
216
217	if (a >= 0 && (APPLET_IS_NOFORK(a)
218	#if BB_MMU
219	\|\| APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
220	#endif
221	)) {
222	#if BB_MMU
223	if (APPLET_IS_NOFORK(a))
224	#endif
225	{
226	return run_nofork_applet(a, argv);
227	}
228	#if BB_MMU
229	/* MMU only */
230	/* a->noexec is true */
231	rc = fork();
232	if (rc) /* parent or error */
233	return wait4pid(rc);
234	/* child */
235	xfunc_error_retval = EXIT_FAILURE;
236	run_applet_no_and_exit(a, argv);
237	#endif
238	}
239	#endif /* FEATURE_PREFER_APPLETS */
240	rc = spawn(argv);
241	return wait4pid(rc);
242	}
243
244	#if !BB_MMU
245	void FAST_FUNC re_exec(char **argv)
246	{
247	/* high-order bit of first char in argv[0] is a hidden
248	* "we have (already) re-execed, don't do it again" flag */
249	argv[0][0] \|= 0x80;
250	execv(bb_busybox_exec_path, argv);
251	bb_perror_msg_and_die("exec %s", bb_busybox_exec_path);
252	}
253
254	void FAST_FUNC forkexit_or_rexec(char **argv)
255	{
256	pid_t pid;
257	/* Maybe we are already re-execed and come here again? */
258	if (re_execed)
259	return;
260
261	pid = vfork();
262	if (pid < 0) /* wtf? */
263	bb_perror_msg_and_die("vfork");
264	if (pid) /* parent */
265	exit(EXIT_SUCCESS);
266	/* child - re-exec ourself */
267	re_exec(argv);
268	}
269	#else
270	/* Dance around (void)...*/
271	#undef forkexit_or_rexec
272	void FAST_FUNC forkexit_or_rexec(void)
273	{
274	pid_t pid;
275	pid = fork();
276	if (pid < 0) /* wtf? */
277	bb_perror_msg_and_die("fork");
278	if (pid) /* parent */
279	exit(EXIT_SUCCESS);
280	/* child */
281	}
282	#define forkexit_or_rexec(argv) forkexit_or_rexec()
283	#endif
284
285	/* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
286	* char *argv "vanishes" /
287	void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
288	{
289	int fd;
290
291	if (flags & DAEMON_CHDIR_ROOT)
292	xchdir("/");
293
294	if (flags & DAEMON_DEVNULL_STDIO) {
295	close(0);
296	close(1);
297	close(2);
298	}
299
300	fd = open(bb_dev_null, O_RDWR);
301	if (fd < 0) {
302	/* NB: we can be called as bb_sanitize_stdio() from init
303	* or mdev, and there /dev/null may legitimately not (yet) exist!
304	* Do not use xopen above, but obtain _ANY_ open descriptor,
305	* even bogus one as below. */
306	fd = xopen("/", O_RDONLY); /* don't believe this can fail */
307	}
308
309	while ((unsigned)fd < 2)
310	fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
311
312	if (!(flags & DAEMON_ONLY_SANITIZE)) {
313	forkexit_or_rexec(argv);
314	/* if daemonizing, make sure we detach from stdio & ctty */
315	setsid();
316	dup2(fd, 0);
317	dup2(fd, 1);
318	dup2(fd, 2);
319	}
320	while (fd > 2) {
321	close(fd--);
322	if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
323	return;
324	/* else close everything after fd#2 */
325	}
326	}
327
328	void FAST_FUNC bb_sanitize_stdio(void)
329	{
330	bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
331	}