source: branches/3.2/mindi-busybox/libbb/vfork_daemon_rexec.c @ 3186

Last change on this file since 3186 was 2725, checked in by bruno, 8 years ago
  • Update mindi-busybox to 1.18.3 to avoid problems with the tar command which is now failing on recent versions with busybox 1.7.3
File size: 7.6 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
72void FAST_FUNC save_nofork_data(struct nofork_save_area *save)
73{
74    memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
75    save->applet_name = applet_name;
76    save->xfunc_error_retval = xfunc_error_retval;
77    save->option_mask32 = option_mask32;
78    save->die_sleep = die_sleep;
79    save->saved = 1;
80}
81
82void FAST_FUNC restore_nofork_data(struct nofork_save_area *save)
83{
84    memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
85    applet_name = save->applet_name;
86    xfunc_error_retval = save->xfunc_error_retval;
87    option_mask32 = save->option_mask32;
88    die_sleep = save->die_sleep;
89}
90
91int FAST_FUNC run_nofork_applet_prime(struct nofork_save_area *old, int applet_no, char **argv)
92{
93    int rc, argc;
94
95    applet_name = APPLET_NAME(applet_no);
96
97    xfunc_error_retval = EXIT_FAILURE;
98
99    /* Special flag for xfunc_die(). If xfunc will "die"
100     * in NOFORK applet, xfunc_die() sees negative
101     * die_sleep and longjmp here instead. */
102    die_sleep = -1;
103
104    /* In case getopt() or getopt32() was already called:
105     * reset the libc getopt() function, which keeps internal state.
106     *
107     * BSD-derived getopt() functions require that optind be set to 1 in
108     * order to reset getopt() state.  This used to be generally accepted
109     * way of resetting getopt().  However, glibc's getopt()
110     * has additional getopt() state beyond optind, and requires that
111     * optind be set to zero to reset its state.  So the unfortunate state of
112     * affairs is that BSD-derived versions of getopt() misbehave if
113     * optind is set to 0 in order to reset getopt(), and glibc's getopt()
114     * will core dump if optind is set 1 in order to reset getopt().
115     *
116     * More modern versions of BSD require that optreset be set to 1 in
117     * order to reset getopt().  Sigh.  Standards, anyone?
118     */
119#ifdef __GLIBC__
120    optind = 0;
121#else /* BSD style */
122    optind = 1;
123    /* optreset = 1; */
124#endif
125    /* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
126    /* (values above are what they initialized to in glibc and uclibc) */
127    /* option_mask32 = 0; - not needed, no applet depends on it being 0 */
128
129    argc = 1;
130    while (argv[argc])
131        argc++;
132
133    rc = setjmp(die_jmp);
134    if (!rc) {
135        /* Some callers (xargs)
136         * need argv untouched because they free argv[i]! */
137        char *tmp_argv[argc+1];
138        memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
139        /* Finally we can call NOFORK applet's main() */
140        rc = applet_main[applet_no](argc, tmp_argv);
141
142    /* The whole reason behind nofork_save_area is that <applet>_main
143     * may exit non-locally! For example, in hush Ctrl-Z tries
144     * (modulo bugs) to dynamically create a child (backgrounded task)
145     * if it detects that Ctrl-Z was pressed when a NOFORK was running.
146     * Testcase: interactive "rm -i".
147     * Don't fool yourself into thinking "and <applet>_main() returns
148     * quickly here" and removing "useless" nofork_save_area code. */
149
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 some globals */
157    restore_nofork_data(old);
158
159    /* Other globals can be simply reset to defaults */
160#ifdef __GLIBC__
161    optind = 0;
162#else /* BSD style */
163    optind = 1;
164#endif
165
166    return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
167}
168
169int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
170{
171    struct nofork_save_area old;
172
173    /* Saving globals */
174    save_nofork_data(&old);
175    return run_nofork_applet_prime(&old, applet_no, argv);
176}
177#endif /* FEATURE_PREFER_APPLETS */
178
179int FAST_FUNC spawn_and_wait(char **argv)
180{
181    int rc;
182#if ENABLE_FEATURE_PREFER_APPLETS
183    int a = find_applet_by_name(argv[0]);
184
185    if (a >= 0 && (APPLET_IS_NOFORK(a)
186#if BB_MMU
187            || APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
188#endif
189    )) {
190#if BB_MMU
191        if (APPLET_IS_NOFORK(a))
192#endif
193        {
194            return run_nofork_applet(a, argv);
195        }
196#if BB_MMU
197        /* MMU only */
198        /* a->noexec is true */
199        rc = fork();
200        if (rc) /* parent or error */
201            return wait4pid(rc);
202        /* child */
203        xfunc_error_retval = EXIT_FAILURE;
204        run_applet_no_and_exit(a, argv);
205#endif
206    }
207#endif /* FEATURE_PREFER_APPLETS */
208    rc = spawn(argv);
209    return wait4pid(rc);
210}
211
212#if !BB_MMU
213void FAST_FUNC re_exec(char **argv)
214{
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 */
217    argv[0][0] |= 0x80;
218    execv(bb_busybox_exec_path, argv);
219    bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path);
220}
221
222pid_t FAST_FUNC fork_or_rexec(char **argv)
223{
224    pid_t pid;
225    /* Maybe we are already re-execed and come here again? */
226    if (re_execed)
227        return 0;
228    pid = xvfork();
229    if (pid) /* parent */
230        return pid;
231    /* child - re-exec ourself */
232    re_exec(argv);
233}
234#endif
235
236/* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
237 * char **argv "vanishes" */
238void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
239{
240    int fd;
241
242    if (flags & DAEMON_CHDIR_ROOT)
243        xchdir("/");
244
245    if (flags & DAEMON_DEVNULL_STDIO) {
246        close(0);
247        close(1);
248        close(2);
249    }
250
251    fd = open(bb_dev_null, O_RDWR);
252    if (fd < 0) {
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 */
258    }
259
260    while ((unsigned)fd < 2)
261        fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
262
263    if (!(flags & DAEMON_ONLY_SANITIZE)) {
264        if (fork_or_rexec(argv))
265            exit(EXIT_SUCCESS); /* parent */
266        /* if daemonizing, make sure we detach from stdio & ctty */
267        setsid();
268        dup2(fd, 0);
269        dup2(fd, 1);
270        dup2(fd, 2);
271    }
272    while (fd > 2) {
273        close(fd--);
274        if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
275            return;
276        /* else close everything after fd#2 */
277    }
278}
279
280void FAST_FUNC bb_sanitize_stdio(void)
281{
282    bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
283}
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