source: branches/3.2/mindi-busybox/libbb/vfork_daemon_rexec.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 5 years ago
  • Update mindi-busybox to 1.21.1
File size: 7.4 KB
Line 
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 source tree.
16 */
17
18#include "busybox.h" /* uses applet tables */
19
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. */
22pid_t FAST_FUNC spawn(char **argv)
23{
24    /* Compiler should not optimize stores here */
25    volatile int failed;
26    pid_t pid;
27
28    fflush_all();
29
30    /* Be nice to nommu machines. */
31    failed = 0;
32    pid = vfork();
33    if (pid < 0) /* error */
34        return pid;
35    if (!pid) { /* child */
36        /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
37        BB_EXECVP(argv[0], argv);
38
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.)
42         */
43        failed = errno;
44        /* mount, for example, does not want the message */
45        /*bb_perror_msg("can't execute '%s'", argv[0]);*/
46        _exit(111);
47    }
48    /* parent */
49    /* Unfortunately, this is not reliable: according to standards
50     * vfork() can be equivalent to fork() and we won't see value
51     * of 'failed'.
52     * Interested party can wait on pid and learn exit code.
53     * If 111 - then it (most probably) failed to exec */
54    if (failed) {
55        safe_waitpid(pid, NULL, 0); /* prevent zombie */
56        errno = failed;
57        return -1;
58    }
59    return pid;
60}
61
62/* Die with an error message if we can't spawn a child process. */
63pid_t FAST_FUNC xspawn(char **argv)
64{
65    pid_t pid = spawn(argv);
66    if (pid < 0)
67        bb_simple_perror_msg_and_die(*argv);
68    return pid;
69}
70
71#if ENABLE_FEATURE_PREFER_APPLETS
72struct nofork_save_area {
73    jmp_buf die_jmp;
74    const char *applet_name;
75    uint32_t option_mask32;
76    int die_sleep;
77    uint8_t xfunc_error_retval;
78};
79static void save_nofork_data(struct nofork_save_area *save)
80{
81    memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
82    save->applet_name = applet_name;
83    save->xfunc_error_retval = xfunc_error_retval;
84    save->option_mask32 = option_mask32;
85    save->die_sleep = die_sleep;
86}
87static void restore_nofork_data(struct nofork_save_area *save)
88{
89    memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
90    applet_name = save->applet_name;
91    xfunc_error_retval = save->xfunc_error_retval;
92    option_mask32 = save->option_mask32;
93    die_sleep = save->die_sleep;
94}
95
96int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
97{
98    int rc, argc;
99    struct nofork_save_area old;
100
101    save_nofork_data(&old);
102
103    applet_name = APPLET_NAME(applet_no);
104
105    xfunc_error_retval = EXIT_FAILURE;
106
107    /* In case getopt() or getopt32() was already called:
108     * reset the libc getopt() function, which keeps internal state.
109     *
110     * BSD-derived getopt() functions require that optind be set to 1 in
111     * order to reset getopt() state.  This used to be generally accepted
112     * way of resetting getopt().  However, glibc's getopt()
113     * has additional getopt() state beyond optind, and requires that
114     * optind be set to zero to reset its state.  So the unfortunate state of
115     * affairs is that BSD-derived versions of getopt() misbehave if
116     * optind is set to 0 in order to reset getopt(), and glibc's getopt()
117     * will core dump if optind is set 1 in order to reset getopt().
118     *
119     * More modern versions of BSD require that optreset be set to 1 in
120     * order to reset getopt().  Sigh.  Standards, anyone?
121     */
122#ifdef __GLIBC__
123    optind = 0;
124#else /* BSD style */
125    optind = 1;
126    /* optreset = 1; */
127#endif
128    /* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
129    /* (values above are what they initialized to in glibc and uclibc) */
130    /* option_mask32 = 0; - not needed, no applet depends on it being 0 */
131
132    argc = 1;
133    while (argv[argc])
134        argc++;
135
136    /* Special flag for xfunc_die(). If xfunc will "die"
137     * in NOFORK applet, xfunc_die() sees negative
138     * die_sleep and longjmp here instead. */
139    die_sleep = -1;
140
141    rc = setjmp(die_jmp);
142    if (!rc) {
143        /* Some callers (xargs)
144         * need argv untouched because they free argv[i]! */
145        char *tmp_argv[argc+1];
146        memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
147        /* Finally we can call NOFORK applet's main() */
148        rc = applet_main[applet_no](argc, tmp_argv);
149    } else { /* xfunc died in NOFORK applet */
150        /* in case they meant to return 0... */
151        if (rc == -2222)
152            rc = 0;
153    }
154
155    /* Restoring some globals */
156    restore_nofork_data(&old);
157
158    /* Other globals can be simply reset to defaults */
159#ifdef __GLIBC__
160    optind = 0;
161#else /* BSD style */
162    optind = 1;
163#endif
164
165    return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
166}
167#endif /* FEATURE_PREFER_APPLETS */
168
169int FAST_FUNC spawn_and_wait(char **argv)
170{
171    int rc;
172#if ENABLE_FEATURE_PREFER_APPLETS
173    int a = find_applet_by_name(argv[0]);
174
175    if (a >= 0 && (APPLET_IS_NOFORK(a)
176# if BB_MMU
177            || APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
178# endif
179    )) {
180# if BB_MMU
181        if (APPLET_IS_NOFORK(a))
182# endif
183        {
184            return run_nofork_applet(a, argv);
185        }
186# if BB_MMU
187        /* MMU only */
188        /* a->noexec is true */
189        rc = fork();
190        if (rc) /* parent or error */
191            return wait4pid(rc);
192        /* child */
193        xfunc_error_retval = EXIT_FAILURE;
194        run_applet_no_and_exit(a, argv);
195# endif
196    }
197#endif /* FEATURE_PREFER_APPLETS */
198    rc = spawn(argv);
199    return wait4pid(rc);
200}
201
202#if !BB_MMU
203void FAST_FUNC re_exec(char **argv)
204{
205    /* high-order bit of first char in argv[0] is a hidden
206     * "we have (already) re-execed, don't do it again" flag */
207    argv[0][0] |= 0x80;
208    execv(bb_busybox_exec_path, argv);
209    bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path);
210}
211
212pid_t FAST_FUNC fork_or_rexec(char **argv)
213{
214    pid_t pid;
215    /* Maybe we are already re-execed and come here again? */
216    if (re_execed)
217        return 0;
218    pid = xvfork();
219    if (pid) /* parent */
220        return pid;
221    /* child - re-exec ourself */
222    re_exec(argv);
223}
224#endif
225
226/* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
227 * char **argv "vanishes" */
228void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
229{
230    int fd;
231
232    if (flags & DAEMON_CHDIR_ROOT)
233        xchdir("/");
234
235    if (flags & DAEMON_DEVNULL_STDIO) {
236        close(0);
237        close(1);
238        close(2);
239    }
240
241    fd = open(bb_dev_null, O_RDWR);
242    if (fd < 0) {
243        /* NB: we can be called as bb_sanitize_stdio() from init
244         * or mdev, and there /dev/null may legitimately not (yet) exist!
245         * Do not use xopen above, but obtain _ANY_ open descriptor,
246         * even bogus one as below. */
247        fd = xopen("/", O_RDONLY); /* don't believe this can fail */
248    }
249
250    while ((unsigned)fd < 2)
251        fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
252
253    if (!(flags & DAEMON_ONLY_SANITIZE)) {
254        if (fork_or_rexec(argv))
255            exit(EXIT_SUCCESS); /* parent */
256        /* if daemonizing, detach from stdio & ctty */
257        setsid();
258        dup2(fd, 0);
259        dup2(fd, 1);
260        dup2(fd, 2);
261        if (flags & DAEMON_DOUBLE_FORK) {
262            /* On Linux, session leader can acquire ctty
263             * unknowingly, by opening a tty.
264             * Prevent this: stop being a session leader.
265             */
266            if (fork_or_rexec(argv))
267                exit(EXIT_SUCCESS); /* parent */
268        }
269    }
270    while (fd > 2) {
271        close(fd--);
272        if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
273            return;
274        /* else close everything after fd#2 */
275    }
276}
277
278void FAST_FUNC bb_sanitize_stdio(void)
279{
280    bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
281}
Note: See TracBrowser for help on using the repository browser.