blob: c192829b55fca8388f3f356a94c15d2314dd6e03
| 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. */ |
| 22 | pid_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. */ |
| 63 | pid_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 \ |
| 72 | || ENABLE_FEATURE_SH_NOFORK |
| 73 | static jmp_buf die_jmp; |
| 74 | static void jump(void) |
| 75 | { |
| 76 | /* Special case. We arrive here if NOFORK applet |
| 77 | * calls xfunc, which then decides to die. |
| 78 | * We don't die, but jump instead back to caller. |
| 79 | * NOFORK applets still cannot carelessly call xfuncs: |
| 80 | * p = xmalloc(10); |
| 81 | * q = xmalloc(10); // BUG! if this dies, we leak p! |
| 82 | */ |
| 83 | /* | 0x100 allows to pass zero exitcode (longjmp can't pass 0). |
| 84 | * This works because exitcodes are bytes, |
| 85 | * run_nofork_applet() ensures that by "& 0xff" */ |
| 86 | longjmp(die_jmp, xfunc_error_retval | 0x100); |
| 87 | } |
| 88 | |
| 89 | struct nofork_save_area { |
| 90 | jmp_buf die_jmp; |
| 91 | void (*die_func)(void); |
| 92 | const char *applet_name; |
| 93 | uint32_t option_mask32; |
| 94 | uint8_t xfunc_error_retval; |
| 95 | }; |
| 96 | static void save_nofork_data(struct nofork_save_area *save) |
| 97 | { |
| 98 | memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp)); |
| 99 | save->die_func = die_func; |
| 100 | save->applet_name = applet_name; |
| 101 | save->option_mask32 = option_mask32; |
| 102 | save->xfunc_error_retval = xfunc_error_retval; |
| 103 | } |
| 104 | static void restore_nofork_data(struct nofork_save_area *save) |
| 105 | { |
| 106 | memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp)); |
| 107 | die_func = save->die_func; |
| 108 | applet_name = save->applet_name; |
| 109 | option_mask32 = save->option_mask32; |
| 110 | xfunc_error_retval = save->xfunc_error_retval; |
| 111 | } |
| 112 | |
| 113 | int FAST_FUNC run_nofork_applet(int applet_no, char **argv) |
| 114 | { |
| 115 | int rc, argc; |
| 116 | struct nofork_save_area old; |
| 117 | |
| 118 | save_nofork_data(&old); |
| 119 | |
| 120 | xfunc_error_retval = EXIT_FAILURE; |
| 121 | |
| 122 | /* In case getopt() or getopt32() was already called: |
| 123 | * reset the libc getopt() function, which keeps internal state. |
| 124 | * |
| 125 | * BSD-derived getopt() functions require that optind be set to 1 in |
| 126 | * order to reset getopt() state. This used to be generally accepted |
| 127 | * way of resetting getopt(). However, glibc's getopt() |
| 128 | * has additional getopt() state beyond optind, and requires that |
| 129 | * optind be set to zero to reset its state. So the unfortunate state of |
| 130 | * affairs is that BSD-derived versions of getopt() misbehave if |
| 131 | * optind is set to 0 in order to reset getopt(), and glibc's getopt() |
| 132 | * will core dump if optind is set 1 in order to reset getopt(). |
| 133 | * |
| 134 | * More modern versions of BSD require that optreset be set to 1 in |
| 135 | * order to reset getopt(). Sigh. Standards, anyone? |
| 136 | */ |
| 137 | #ifdef __GLIBC__ |
| 138 | optind = 0; |
| 139 | #else /* BSD style */ |
| 140 | optind = 1; |
| 141 | /* optreset = 1; */ |
| 142 | #endif |
| 143 | /* optarg = NULL; opterr = 1; optopt = 63; - do we need this too? */ |
| 144 | /* (values above are what they initialized to in glibc and uclibc) */ |
| 145 | /* option_mask32 = 0; - not needed, no applet depends on it being 0 */ |
| 146 | |
| 147 | argc = 1; |
| 148 | while (argv[argc]) |
| 149 | argc++; |
| 150 | |
| 151 | /* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */ |
| 152 | die_func = jump; |
| 153 | rc = setjmp(die_jmp); |
| 154 | if (!rc) { |
| 155 | /* Some callers (xargs) |
| 156 | * need argv untouched because they free argv[i]! */ |
| 157 | char *tmp_argv[argc+1]; |
| 158 | memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0])); |
| 159 | applet_name = tmp_argv[0]; |
| 160 | /* Finally we can call NOFORK applet's main() */ |
| 161 | rc = applet_main[applet_no](argc, tmp_argv); |
| 162 | } else { |
| 163 | /* xfunc died in NOFORK applet */ |
| 164 | } |
| 165 | |
| 166 | /* Restoring some globals */ |
| 167 | restore_nofork_data(&old); |
| 168 | |
| 169 | /* Other globals can be simply reset to defaults */ |
| 170 | #ifdef __GLIBC__ |
| 171 | optind = 0; |
| 172 | #else /* BSD style */ |
| 173 | optind = 1; |
| 174 | #endif |
| 175 | |
| 176 | return rc & 0xff; /* don't confuse people with "exitcodes" >255 */ |
| 177 | } |
| 178 | #endif /* FEATURE_PREFER_APPLETS || FEATURE_SH_NOFORK */ |
| 179 | |
| 180 | int FAST_FUNC spawn_and_wait(char **argv) |
| 181 | { |
| 182 | int rc; |
| 183 | #if ENABLE_FEATURE_PREFER_APPLETS |
| 184 | int a = find_applet_by_name(argv[0]); |
| 185 | |
| 186 | if (a >= 0 && (APPLET_IS_NOFORK(a) |
| 187 | # if BB_MMU |
| 188 | || APPLET_IS_NOEXEC(a) /* NOEXEC trick needs fork() */ |
| 189 | # endif |
| 190 | )) { |
| 191 | # if BB_MMU |
| 192 | if (APPLET_IS_NOFORK(a)) |
| 193 | # endif |
| 194 | { |
| 195 | return run_nofork_applet(a, argv); |
| 196 | } |
| 197 | # if BB_MMU |
| 198 | /* MMU only */ |
| 199 | /* a->noexec is true */ |
| 200 | rc = fork(); |
| 201 | if (rc) /* parent or error */ |
| 202 | return wait4pid(rc); |
| 203 | /* child */ |
| 204 | xfunc_error_retval = EXIT_FAILURE; |
| 205 | run_applet_no_and_exit(a, argv); |
| 206 | # endif |
| 207 | } |
| 208 | #endif /* FEATURE_PREFER_APPLETS */ |
| 209 | rc = spawn(argv); |
| 210 | return wait4pid(rc); |
| 211 | } |
| 212 | |
| 213 | #if !BB_MMU |
| 214 | void FAST_FUNC re_exec(char **argv) |
| 215 | { |
| 216 | /* high-order bit of first char in argv[0] is a hidden |
| 217 | * "we have (already) re-execed, don't do it again" flag */ |
| 218 | argv[0][0] |= 0x80; |
| 219 | execv(bb_busybox_exec_path, argv); |
| 220 | bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path); |
| 221 | } |
| 222 | |
| 223 | pid_t FAST_FUNC fork_or_rexec(char **argv) |
| 224 | { |
| 225 | pid_t pid; |
| 226 | /* Maybe we are already re-execed and come here again? */ |
| 227 | if (re_execed) |
| 228 | return 0; |
| 229 | pid = xvfork(); |
| 230 | if (pid) /* parent */ |
| 231 | return pid; |
| 232 | /* child - re-exec ourself */ |
| 233 | re_exec(argv); |
| 234 | } |
| 235 | #endif |
| 236 | |
| 237 | /* Due to a #define in libbb.h on MMU systems we actually have 1 argument - |
| 238 | * char **argv "vanishes" */ |
| 239 | void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv) |
| 240 | { |
| 241 | int fd; |
| 242 | |
| 243 | if (flags & DAEMON_CHDIR_ROOT) |
| 244 | xchdir("/"); |
| 245 | |
| 246 | if (flags & DAEMON_DEVNULL_STDIO) { |
| 247 | close(0); |
| 248 | close(1); |
| 249 | close(2); |
| 250 | } |
| 251 | |
| 252 | fd = open(bb_dev_null, O_RDWR); |
| 253 | if (fd < 0) { |
| 254 | /* NB: we can be called as bb_sanitize_stdio() from init |
| 255 | * or mdev, and there /dev/null may legitimately not (yet) exist! |
| 256 | * Do not use xopen above, but obtain _ANY_ open descriptor, |
| 257 | * even bogus one as below. */ |
| 258 | fd = xopen("/", O_RDONLY); /* don't believe this can fail */ |
| 259 | } |
| 260 | |
| 261 | while ((unsigned)fd < 2) |
| 262 | fd = dup(fd); /* have 0,1,2 open at least to /dev/null */ |
| 263 | |
| 264 | if (!(flags & DAEMON_ONLY_SANITIZE)) { |
| 265 | if (fork_or_rexec(argv)) |
| 266 | exit(EXIT_SUCCESS); /* parent */ |
| 267 | /* if daemonizing, detach from stdio & ctty */ |
| 268 | setsid(); |
| 269 | dup2(fd, 0); |
| 270 | dup2(fd, 1); |
| 271 | dup2(fd, 2); |
| 272 | if (flags & DAEMON_DOUBLE_FORK) { |
| 273 | /* On Linux, session leader can acquire ctty |
| 274 | * unknowingly, by opening a tty. |
| 275 | * Prevent this: stop being a session leader. |
| 276 | */ |
| 277 | if (fork_or_rexec(argv)) |
| 278 | exit(EXIT_SUCCESS); /* parent */ |
| 279 | } |
| 280 | } |
| 281 | while (fd > 2) { |
| 282 | close(fd--); |
| 283 | if (!(flags & DAEMON_CLOSE_EXTRA_FDS)) |
| 284 | return; |
| 285 | /* else close everything after fd#2 */ |
| 286 | } |
| 287 | } |
| 288 | |
| 289 | void FAST_FUNC bb_sanitize_stdio(void) |
| 290 | { |
| 291 | bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL); |
| 292 | } |
| 293 |