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" /* for struct bb_applet */
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. */
23pid_t 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. */
61pid_t xspawn(char **argv)
62{
63	pid_t pid = spawn(argv);
64	if (pid < 0)
65		bb_perror_msg_and_die("%s", *argv);
66	return pid;
67}
68
69// Wait for the specified child PID to exit, returning child's error return.
70int wait4pid(int pid)
71{
72	int status;
73
74	if (pid <= 0) {
75		/*errno = ECHILD; -- wrong. */
76		/* we expect errno to be already set from failed [v]fork/exec */
77		return -1;
78	}
79	if (waitpid(pid, &status, 0) == -1)
80		return -1;
81	if (WIFEXITED(status))
82		return WEXITSTATUS(status);
83	if (WIFSIGNALED(status))
84		return WTERMSIG(status) + 1000;
85	return 0;
86}
87
88int wait_nohang(int *wstat)
89{
90	return waitpid(-1, wstat, WNOHANG);
91}
92
93int wait_pid(int *wstat, int pid)
94{
95	int r;
96
97	do
98		r = waitpid(pid, wstat, 0);
99	while ((r == -1) && (errno == EINTR));
100	return r;
101}
102
103#if ENABLE_FEATURE_PREFER_APPLETS
104void save_nofork_data(struct nofork_save_area *save)
105{
106	memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
107	save->current_applet = current_applet;
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
114void restore_nofork_data(struct nofork_save_area *save)
115{
116	memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
117	current_applet = save->current_applet;
118	xfunc_error_retval = save->xfunc_error_retval;
119	option_mask32 = save->option_mask32;
120	die_sleep = save->die_sleep;
121
122	applet_name = current_applet->name;
123}
124
125int run_nofork_applet_prime(struct nofork_save_area *old, const struct bb_applet *a, char **argv)
126{
127	int rc, argc;
128
129	current_applet = a;
130	applet_name = a->name;
131	xfunc_error_retval = EXIT_FAILURE;
132	/*option_mask32 = 0; - not needed */
133	/* special flag for xfunc_die(). If xfunc will "die"
134	 * in NOFORK applet, xfunc_die() sees negative
135	 * die_sleep and longjmp here instead. */
136	die_sleep = -1;
137
138	argc = 1;
139	while (argv[argc])
140		argc++;
141
142	rc = setjmp(die_jmp);
143	if (!rc) {
144		/* Some callers (xargs)
145		 * need argv untouched because they free argv[i]! */
146		char *tmp_argv[argc+1];
147		memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
148		/* Finally we can call NOFORK applet's main() */
149		rc = a->main(argc, tmp_argv);
150	} else { /* xfunc died in NOFORK applet */
151		/* in case they meant to return 0... */
152		if (rc == -2222)
153			rc = 0;
154	}
155
156	/* Restoring globals */
157	restore_nofork_data(old);
158	return rc;
159}
160
161int run_nofork_applet(const struct bb_applet *a, char **argv)
162{
163	struct nofork_save_area old;
164
165	/* Saving globals */
166	save_nofork_data(&old);
167	return run_nofork_applet_prime(&old, a, argv);
168}
169#endif /* FEATURE_PREFER_APPLETS */
170
171int spawn_and_wait(char **argv)
172{
173	int rc;
174#if ENABLE_FEATURE_PREFER_APPLETS
175	const struct bb_applet *a = find_applet_by_name(argv[0]);
176
177	if (a && (a->nofork
178#if BB_MMU
179		 || a->noexec /* NOEXEC trick needs fork() */
180#endif
181	)) {
182#if BB_MMU
183		if (a->nofork)
184#endif
185		{
186			return run_nofork_applet(a, argv);
187		}
188#if BB_MMU
189		/* MMU only */
190		/* a->noexec is true */
191		rc = fork();
192		if (rc) /* parent or error */
193			return wait4pid(rc);
194		/* child */
195		xfunc_error_retval = EXIT_FAILURE;
196		current_applet = a;
197		run_current_applet_and_exit(argv);
198#endif
199	}
200#endif /* FEATURE_PREFER_APPLETS */
201	rc = spawn(argv);
202	return wait4pid(rc);
203}
204
205#if !BB_MMU
206void re_exec(char **argv)
207{
208	/* high-order bit of first char in argv[0] is a hidden
209	 * "we have (already) re-execed, don't do it again" flag */
210	argv[0][0] |= 0x80;
211	execv(bb_busybox_exec_path, argv);
212	bb_perror_msg_and_die("exec %s", bb_busybox_exec_path);
213}
214
215void forkexit_or_rexec(char **argv)
216{
217	pid_t pid;
218	/* Maybe we are already re-execed and come here again? */
219	if (re_execed)
220		return;
221
222	pid = vfork();
223	if (pid < 0) /* wtf? */
224		bb_perror_msg_and_die("vfork");
225	if (pid) /* parent */
226		exit(0);
227	/* child - re-exec ourself */
228	re_exec(argv);
229}
230#else
231/* Dance around (void)...*/
232#undef forkexit_or_rexec
233void forkexit_or_rexec(void)
234{
235	pid_t pid;
236	pid = fork();
237	if (pid < 0) /* wtf? */
238		bb_perror_msg_and_die("fork");
239	if (pid) /* parent */
240		exit(0);
241	/* child */
242}
243#define forkexit_or_rexec(argv) forkexit_or_rexec()
244#endif
245
246/* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
247 * char **argv "vanishes" */
248void bb_daemonize_or_rexec(int flags, char **argv)
249{
250	int fd;
251
252	if (flags & DAEMON_CHDIR_ROOT)
253		xchdir("/");
254
255	if (flags & DAEMON_DEVNULL_STDIO) {
256		close(0);
257		close(1);
258		close(2);
259	}
260
261	fd = xopen(bb_dev_null, O_RDWR);
262
263	while ((unsigned)fd < 2)
264		fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
265
266	if (!(flags & DAEMON_ONLY_SANITIZE)) {
267		forkexit_or_rexec(argv);
268		/* if daemonizing, make sure we detach from stdio & ctty */
269		setsid();
270		dup2(fd, 0);
271		dup2(fd, 1);
272		dup2(fd, 2);
273	}
274	while (fd > 2) {
275		close(fd--);
276		if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
277			return;
278		/* else close everything after fd#2 */
279	}
280}
281
282void bb_sanitize_stdio(void)
283{
284	bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
285}
286