[821] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Rexec program for system have fork() as vfork() with foreground option
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| 4 | *
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| 5 | * Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru>
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| 6 | * Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu>
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| 7 | *
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| 8 | * daemon() portion taken from uClibc:
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| 9 | *
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| 10 | * Copyright (c) 1991, 1993
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| 11 | * The Regents of the University of California. All rights reserved.
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| 12 | *
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| 13 | * Modified for uClibc by Erik Andersen <andersee@debian.org>
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| 14 | *
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[2725] | 15 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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[821] | 16 | */
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| 17 |
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[2725] | 18 | #include "busybox.h" /* uses applet tables */
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[821] | 19 |
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[1765] | 20 | /* This does a fork/exec in one call, using vfork(). Returns PID of new child,
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| 21 | * -1 for failure. Runs argv[0], searching path if that has no / in it. */
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[2725] | 22 | pid_t FAST_FUNC spawn(char **argv)
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[1765] | 23 | {
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| 24 | /* Compiler should not optimize stores here */
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| 25 | volatile int failed;
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| 26 | pid_t pid;
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[821] | 27 |
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[2725] | 28 | fflush_all();
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[1765] | 29 |
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| 30 | /* Be nice to nommu machines. */
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| 31 | failed = 0;
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| 32 | pid = vfork();
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| 33 | if (pid < 0) /* error */
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| 34 | return pid;
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| 35 | if (!pid) { /* child */
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| 36 | /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
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| 37 | BB_EXECVP(argv[0], argv);
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| 38 |
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| 39 | /* We are (maybe) sharing a stack with blocked parent,
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| 40 | * let parent know we failed and then exit to unblock parent
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| 41 | * (but don't run atexit() stuff, which would screw up parent.)
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| 42 | */
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| 43 | failed = errno;
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[2725] | 44 | /* mount, for example, does not want the message */
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| 45 | /*bb_perror_msg("can't execute '%s'", argv[0]);*/
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[1765] | 46 | _exit(111);
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| 47 | }
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| 48 | /* parent */
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| 49 | /* Unfortunately, this is not reliable: according to standards
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| 50 | * vfork() can be equivalent to fork() and we won't see value
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| 51 | * of 'failed'.
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| 52 | * Interested party can wait on pid and learn exit code.
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| 53 | * If 111 - then it (most probably) failed to exec */
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| 54 | if (failed) {
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[2725] | 55 | safe_waitpid(pid, NULL, 0); /* prevent zombie */
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[1765] | 56 | errno = failed;
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| 57 | return -1;
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| 58 | }
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| 59 | return pid;
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| 60 | }
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| 61 |
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| 62 | /* Die with an error message if we can't spawn a child process. */
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[2725] | 63 | pid_t FAST_FUNC xspawn(char **argv)
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[821] | 64 | {
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[1765] | 65 | pid_t pid = spawn(argv);
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| 66 | if (pid < 0)
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[2725] | 67 | bb_simple_perror_msg_and_die(*argv);
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[1765] | 68 | return pid;
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| 69 | }
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[821] | 70 |
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[1765] | 71 | #if ENABLE_FEATURE_PREFER_APPLETS
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[3621] | 72 | static jmp_buf die_jmp;
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| 73 | static void jump(void)
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| 74 | {
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| 75 | /* Special case. We arrive here if NOFORK applet
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| 76 | * calls xfunc, which then decides to die.
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| 77 | * We don't die, but jump instead back to caller.
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| 78 | * NOFORK applets still cannot carelessly call xfuncs:
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| 79 | * p = xmalloc(10);
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| 80 | * q = xmalloc(10); // BUG! if this dies, we leak p!
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| 81 | */
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| 82 | /* | 0x100 allows to pass zero exitcode (longjmp can't pass 0).
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| 83 | * This works because exitcodes are bytes,
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| 84 | * run_nofork_applet() ensures that by "& 0xff" */
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| 85 | longjmp(die_jmp, xfunc_error_retval | 0x100);
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| 86 | }
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| 87 |
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[3232] | 88 | struct nofork_save_area {
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| 89 | jmp_buf die_jmp;
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[3621] | 90 | void (*die_func)(void);
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[3232] | 91 | const char *applet_name;
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| 92 | uint32_t option_mask32;
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| 93 | uint8_t xfunc_error_retval;
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| 94 | };
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| 95 | static void save_nofork_data(struct nofork_save_area *save)
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[1765] | 96 | {
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| 97 | memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
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[3621] | 98 | save->die_func = die_func;
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[2725] | 99 | save->applet_name = applet_name;
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[3621] | 100 | save->option_mask32 = option_mask32;
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[1765] | 101 | save->xfunc_error_retval = xfunc_error_retval;
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| 102 | }
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[3232] | 103 | static void restore_nofork_data(struct nofork_save_area *save)
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[1765] | 104 | {
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| 105 | memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
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[3621] | 106 | die_func = save->die_func;
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[2725] | 107 | applet_name = save->applet_name;
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[3621] | 108 | option_mask32 = save->option_mask32;
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[1765] | 109 | xfunc_error_retval = save->xfunc_error_retval;
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| 110 | }
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| 111 |
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[3232] | 112 | int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
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[1765] | 113 | {
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| 114 | int rc, argc;
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[3232] | 115 | struct nofork_save_area old;
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[1765] | 116 |
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[3232] | 117 | save_nofork_data(&old);
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| 118 |
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[1765] | 119 | xfunc_error_retval = EXIT_FAILURE;
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[2725] | 120 |
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| 121 | /* In case getopt() or getopt32() was already called:
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| 122 | * reset the libc getopt() function, which keeps internal state.
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| 123 | *
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| 124 | * BSD-derived getopt() functions require that optind be set to 1 in
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| 125 | * order to reset getopt() state. This used to be generally accepted
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| 126 | * way of resetting getopt(). However, glibc's getopt()
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| 127 | * has additional getopt() state beyond optind, and requires that
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| 128 | * optind be set to zero to reset its state. So the unfortunate state of
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| 129 | * affairs is that BSD-derived versions of getopt() misbehave if
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| 130 | * optind is set to 0 in order to reset getopt(), and glibc's getopt()
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| 131 | * will core dump if optind is set 1 in order to reset getopt().
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| 132 | *
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| 133 | * More modern versions of BSD require that optreset be set to 1 in
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| 134 | * order to reset getopt(). Sigh. Standards, anyone?
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| 135 | */
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| 136 | #ifdef __GLIBC__
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| 137 | optind = 0;
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| 138 | #else /* BSD style */
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| 139 | optind = 1;
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| 140 | /* optreset = 1; */
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| 141 | #endif
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| 142 | /* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */
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| 143 | /* (values above are what they initialized to in glibc and uclibc) */
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| 144 | /* option_mask32 = 0; - not needed, no applet depends on it being 0 */
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| 145 |
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[1765] | 146 | argc = 1;
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| 147 | while (argv[argc])
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| 148 | argc++;
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| 149 |
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[3621] | 150 | /* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */
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| 151 | die_func = jump;
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[1765] | 152 | rc = setjmp(die_jmp);
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| 153 | if (!rc) {
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| 154 | /* Some callers (xargs)
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| 155 | * need argv untouched because they free argv[i]! */
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| 156 | char *tmp_argv[argc+1];
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| 157 | memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
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[3621] | 158 | applet_name = tmp_argv[0];
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[1765] | 159 | /* Finally we can call NOFORK applet's main() */
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[2725] | 160 | rc = applet_main[applet_no](argc, tmp_argv);
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[3621] | 161 | } else {
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| 162 | /* xfunc died in NOFORK applet */
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[821] | 163 | }
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| 164 |
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[2725] | 165 | /* Restoring some globals */
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[3232] | 166 | restore_nofork_data(&old);
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[2725] | 167 |
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| 168 | /* Other globals can be simply reset to defaults */
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| 169 | #ifdef __GLIBC__
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| 170 | optind = 0;
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| 171 | #else /* BSD style */
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| 172 | optind = 1;
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| 173 | #endif
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| 174 |
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| 175 | return rc & 0xff; /* don't confuse people with "exitcodes" >255 */
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[1765] | 176 | }
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| 177 | #endif /* FEATURE_PREFER_APPLETS */
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| 178 |
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[2725] | 179 | int FAST_FUNC spawn_and_wait(char **argv)
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[1765] | 180 | {
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| 181 | int rc;
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| 182 | #if ENABLE_FEATURE_PREFER_APPLETS
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[2725] | 183 | int a = find_applet_by_name(argv[0]);
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[1765] | 184 |
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[2725] | 185 | if (a >= 0 && (APPLET_IS_NOFORK(a)
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[3232] | 186 | # if BB_MMU
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[2725] | 187 | || APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */
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[3232] | 188 | # endif
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[1765] | 189 | )) {
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[3232] | 190 | # if BB_MMU
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[2725] | 191 | if (APPLET_IS_NOFORK(a))
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[3232] | 192 | # endif
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[1765] | 193 | {
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| 194 | return run_nofork_applet(a, argv);
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| 195 | }
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[3232] | 196 | # if BB_MMU
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[1765] | 197 | /* MMU only */
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| 198 | /* a->noexec is true */
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| 199 | rc = fork();
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| 200 | if (rc) /* parent or error */
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| 201 | return wait4pid(rc);
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| 202 | /* child */
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| 203 | xfunc_error_retval = EXIT_FAILURE;
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[2725] | 204 | run_applet_no_and_exit(a, argv);
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[3232] | 205 | # endif
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[821] | 206 | }
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[1765] | 207 | #endif /* FEATURE_PREFER_APPLETS */
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| 208 | rc = spawn(argv);
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| 209 | return wait4pid(rc);
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| 210 | }
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| 211 |
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| 212 | #if !BB_MMU
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[2725] | 213 | void FAST_FUNC re_exec(char **argv)
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[1765] | 214 | {
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| 215 | /* high-order bit of first char in argv[0] is a hidden
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| 216 | * "we have (already) re-execed, don't do it again" flag */
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| 217 | argv[0][0] |= 0x80;
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| 218 | execv(bb_busybox_exec_path, argv);
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[2725] | 219 | bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path);
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[1765] | 220 | }
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| 221 |
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[2725] | 222 | pid_t FAST_FUNC fork_or_rexec(char **argv)
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[1765] | 223 | {
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| 224 | pid_t pid;
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| 225 | /* Maybe we are already re-execed and come here again? */
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| 226 | if (re_execed)
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[2725] | 227 | return 0;
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| 228 | pid = xvfork();
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[1765] | 229 | if (pid) /* parent */
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[2725] | 230 | return pid;
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[1765] | 231 | /* child - re-exec ourself */
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| 232 | re_exec(argv);
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| 233 | }
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| 234 | #endif
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| 235 |
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| 236 | /* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
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| 237 | * char **argv "vanishes" */
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[2725] | 238 | void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv)
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[1765] | 239 | {
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| 240 | int fd;
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| 241 |
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| 242 | if (flags & DAEMON_CHDIR_ROOT)
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| 243 | xchdir("/");
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| 244 |
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| 245 | if (flags & DAEMON_DEVNULL_STDIO) {
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| 246 | close(0);
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| 247 | close(1);
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| 248 | close(2);
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[821] | 249 | }
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[1765] | 250 |
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[2725] | 251 | fd = open(bb_dev_null, O_RDWR);
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| 252 | if (fd < 0) {
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| 253 | /* NB: we can be called as bb_sanitize_stdio() from init
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| 254 | * or mdev, and there /dev/null may legitimately not (yet) exist!
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| 255 | * Do not use xopen above, but obtain _ANY_ open descriptor,
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| 256 | * even bogus one as below. */
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| 257 | fd = xopen("/", O_RDONLY); /* don't believe this can fail */
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| 258 | }
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[1765] | 259 |
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| 260 | while ((unsigned)fd < 2)
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| 261 | fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
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| 262 |
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| 263 | if (!(flags & DAEMON_ONLY_SANITIZE)) {
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[2725] | 264 | if (fork_or_rexec(argv))
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| 265 | exit(EXIT_SUCCESS); /* parent */
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[3232] | 266 | /* if daemonizing, detach from stdio & ctty */
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[1765] | 267 | setsid();
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| 268 | dup2(fd, 0);
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| 269 | dup2(fd, 1);
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| 270 | dup2(fd, 2);
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[3232] | 271 | if (flags & DAEMON_DOUBLE_FORK) {
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| 272 | /* On Linux, session leader can acquire ctty
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| 273 | * unknowingly, by opening a tty.
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| 274 | * Prevent this: stop being a session leader.
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| 275 | */
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| 276 | if (fork_or_rexec(argv))
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| 277 | exit(EXIT_SUCCESS); /* parent */
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| 278 | }
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[1765] | 279 | }
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| 280 | while (fd > 2) {
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| 281 | close(fd--);
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| 282 | if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
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| 283 | return;
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| 284 | /* else close everything after fd#2 */
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| 285 | }
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[821] | 286 | }
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[1765] | 287 |
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[2725] | 288 | void FAST_FUNC bb_sanitize_stdio(void)
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[1765] | 289 | {
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| 290 | bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
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| 291 | }
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