/* vi: set sw=4 ts=4: */ /* * Rexec program for system have fork() as vfork() with foreground option * * Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru> * Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu> * * daemon() portion taken from uClibc: * * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * * Modified for uClibc by Erik Andersen <andersee@debian.org> * * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ #include "busybox.h" /* uses applet tables */ #include "NUM_APPLETS.h" #define NOFORK_SUPPORT ((NUM_APPLETS > 1) && (ENABLE_FEATURE_PREFER_APPLETS || ENABLE_FEATURE_SH_NOFORK)) #define NOEXEC_SUPPORT ((NUM_APPLETS > 1) && (ENABLE_FEATURE_PREFER_APPLETS || ENABLE_FEATURE_SH_STANDALONE)) #if defined(__linux__) && (NUM_APPLETS > 1) # include <sys/prctl.h> # ifndef PR_SET_NAME # define PR_SET_NAME 15 # endif # ifndef PR_GET_NAME # define PR_GET_NAME 16 # endif void FAST_FUNC set_task_comm(const char *comm) { /* okay if too long (truncates) */ prctl(PR_SET_NAME, (long)comm, 0, 0, 0); } #endif /* * NOFORK/NOEXEC support */ #if NOFORK_SUPPORT static jmp_buf die_jmp; static void jump(void) { /* Special case. We arrive here if NOFORK applet * calls xfunc, which then decides to die. * We don't die, but instead jump back to caller. * NOFORK applets still cannot carelessly call xfuncs: * p = xmalloc(10); * q = xmalloc(10); // BUG! if this dies, we leak p! */ /* | 0x100 allows to pass zero exitcode (longjmp can't pass 0). * This works because exitcodes are bytes, * run_nofork_applet() ensures that by "& 0xff" */ longjmp(die_jmp, xfunc_error_retval | 0x100); } struct nofork_save_area { jmp_buf die_jmp; void (*die_func)(void); const char *applet_name; uint32_t option_mask32; smallint logmode; uint8_t xfunc_error_retval; }; static void save_nofork_data(struct nofork_save_area *save) { memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp)); save->die_func = die_func; save->applet_name = applet_name; save->option_mask32 = option_mask32; save->logmode = logmode; save->xfunc_error_retval = xfunc_error_retval; } static void restore_nofork_data(struct nofork_save_area *save) { memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp)); die_func = save->die_func; applet_name = save->applet_name; option_mask32 = save->option_mask32; logmode = save->logmode; xfunc_error_retval = save->xfunc_error_retval; } int FAST_FUNC run_nofork_applet(int applet_no, char **argv) { int rc, argc; struct nofork_save_area old; save_nofork_data(&old); logmode = LOGMODE_STDIO; xfunc_error_retval = EXIT_FAILURE; /* In case getopt() was already called: * reset the libc getopt() function, which keeps internal state. * (getopt32() does it itself, but getopt() doesn't (and can't)) */ GETOPT_RESET(); argc = string_array_len(argv); /* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */ die_func = jump; rc = setjmp(die_jmp); if (!rc) { /* Some callers (xargs) * need argv untouched because they free argv[i]! */ char *tmp_argv[argc+1]; memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0])); applet_name = tmp_argv[0]; /* Finally we can call NOFORK applet's main() */ rc = applet_main[applet_no](argc, tmp_argv); /* Important for shells: `which CMD` was failing */ fflush_all(); } else { /* xfunc died in NOFORK applet */ } /* Restoring some globals */ restore_nofork_data(&old); /* Other globals can be simply reset to defaults */ GETOPT_RESET(); return rc & 0xff; /* don't confuse people with "exitcodes" >255 */ } #endif #if NOEXEC_SUPPORT void FAST_FUNC run_noexec_applet_and_exit(int a, const char *name, char **argv) { /* reset some state and run without execing */ /* msg_eol = "\n"; - no caller needs this reinited yet */ logmode = LOGMODE_STDIO; xfunc_error_retval = EXIT_FAILURE; die_func = NULL; GETOPT_RESET(); //TODO: think pidof, pgrep, pkill! //set_task_comm() makes our pidof find NOEXECs (e.g. "yes >/dev/null"), //but one from procps-ng-3.3.10 needs more! //Rewrite /proc/PID/cmdline? (need to save argv0 and length at init for this to work!) set_task_comm(name); /* applet_name is set by this function: */ run_applet_no_and_exit(a, name, argv); } #endif /* * Higher-level code, hiding optional NOFORK/NOEXEC trickery. */ /* This does a fork/exec in one call, using vfork(). Returns PID of new child, * -1 for failure. Runs argv[0], searching path if that has no / in it. */ pid_t FAST_FUNC spawn(char **argv) { /* Compiler should not optimize stores here */ volatile int failed; pid_t pid; fflush_all(); /* Be nice to nommu machines. */ failed = 0; pid = vfork(); if (pid < 0) /* error */ return pid; if (!pid) { /* child */ /* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */ BB_EXECVP(argv[0], argv); /* We are (maybe) sharing a stack with blocked parent, * let parent know we failed and then exit to unblock parent * (but don't run atexit() stuff, which would screw up parent.) */ failed = errno; /* mount, for example, does not want the message */ /*bb_perror_msg("can't execute '%s'", argv[0]);*/ _exit(111); } /* parent */ /* Unfortunately, this is not reliable: according to standards * vfork() can be equivalent to fork() and we won't see value * of 'failed'. * Interested party can wait on pid and learn exit code. * If 111 - then it (most probably) failed to exec */ if (failed) { safe_waitpid(pid, NULL, 0); /* prevent zombie */ errno = failed; return -1; } return pid; } /* Die with an error message if we can't spawn a child process. */ pid_t FAST_FUNC xspawn(char **argv) { pid_t pid = spawn(argv); if (pid < 0) bb_simple_perror_msg_and_die(*argv); return pid; } int FAST_FUNC spawn_and_wait(char **argv) { int rc; #if ENABLE_FEATURE_PREFER_APPLETS && (NUM_APPLETS > 1) int a = find_applet_by_name(argv[0]); if (a >= 0) { if (APPLET_IS_NOFORK(a)) return run_nofork_applet(a, argv); # if BB_MMU /* NOEXEC needs fork(), thus this is done only on MMU machines: */ if (APPLET_IS_NOEXEC(a)) { fflush_all(); rc = fork(); if (rc) /* parent or error */ return wait4pid(rc); /* child */ run_noexec_applet_and_exit(a, argv[0], argv); } # endif } #endif rc = spawn(argv); return wait4pid(rc); } #if !BB_MMU void FAST_FUNC re_exec(char **argv) { /* high-order bit of first char in argv[0] is a hidden * "we have (already) re-execed, don't do it again" flag */ argv[0][0] |= 0x80; execv(bb_busybox_exec_path, argv); bb_perror_msg_and_die("can't execute '%s'", bb_busybox_exec_path); } pid_t FAST_FUNC fork_or_rexec(char **argv) { pid_t pid; /* Maybe we are already re-execed and come here again? */ if (re_execed) return 0; /* fflush_all(); ? - so far all callers had no buffered output to flush */ pid = xvfork(); if (pid) /* parent */ return pid; /* child - re-exec ourself */ re_exec(argv); } #endif /* Due to a #define in libbb.h on MMU systems we actually have 1 argument - * char **argv "vanishes" */ void FAST_FUNC bb_daemonize_or_rexec(int flags, char **argv) { int fd; if (flags & DAEMON_CHDIR_ROOT) xchdir("/"); if (flags & DAEMON_DEVNULL_STDIO) { close(0); close(1); close(2); } fd = open(bb_dev_null, O_RDWR); if (fd < 0) { /* NB: we can be called as bb_sanitize_stdio() from init * or mdev, and there /dev/null may legitimately not (yet) exist! * Do not use xopen above, but obtain _ANY_ open descriptor, * even bogus one as below. */ fd = xopen("/", O_RDONLY); /* don't believe this can fail */ } while ((unsigned)fd < 2) fd = dup(fd); /* have 0,1,2 open at least to /dev/null */ if (!(flags & DAEMON_ONLY_SANITIZE)) { /* fflush_all(); - add it in fork_or_rexec() if necessary */ if (fork_or_rexec(argv)) _exit(EXIT_SUCCESS); /* parent */ /* if daemonizing, detach from stdio & ctty */ setsid(); dup2(fd, 0); dup2(fd, 1); dup2(fd, 2); if (flags & DAEMON_DOUBLE_FORK) { /* On Linux, session leader can acquire ctty * unknowingly, by opening a tty. * Prevent this: stop being a session leader. */ if (fork_or_rexec(argv)) _exit(EXIT_SUCCESS); /* parent */ } } while (fd > 2) { close(fd--); if (!(flags & DAEMON_CLOSE_EXTRA_FDS)) return; /* else close everything after fd#2 */ } } void FAST_FUNC bb_sanitize_stdio(void) { bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL); }