1 /* vi: set sw=4 ts=4: */
3 * Mini init implementation for busybox
5 * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
6 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
7 * Adjusted by so many folks, it's impossible to keep track.
9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
15 //config: select FEATURE_SYSLOG
17 //config: init is the first program run when the system boots.
19 //config:config LINUXRC
20 //config: bool "linuxrc: support running init from initrd (not initramfs)"
22 //config: select FEATURE_SYSLOG
24 //config: Legacy support for running init under the old-style initrd. Allows
25 //config: the name linuxrc to act as init, and it doesn't assume init is PID 1.
27 //config: This does not apply to initramfs, which runs /init as PID 1 and
28 //config: requires no special support.
30 //config:config FEATURE_USE_INITTAB
31 //config: bool "Support reading an inittab file"
33 //config: depends on INIT || LINUXRC
35 //config: Allow init to read an inittab file when the system boot.
37 //config:config FEATURE_KILL_REMOVED
38 //config: bool "Support killing processes that have been removed from inittab"
40 //config: depends on FEATURE_USE_INITTAB
42 //config: When respawn entries are removed from inittab and a SIGHUP is
43 //config: sent to init, this option will make init kill the processes
44 //config: that have been removed.
46 //config:config FEATURE_KILL_DELAY
47 //config: int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED
48 //config: range 0 1024
50 //config: depends on FEATURE_KILL_REMOVED
52 //config: With nonzero setting, init sends TERM, forks, child waits N
53 //config: seconds, sends KILL and exits. Setting it too high is unwise
54 //config: (child will hang around for too long and could actually kill
55 //config: the wrong process!)
57 //config:config FEATURE_INIT_SCTTY
58 //config: bool "Run commands with leading dash with controlling tty"
60 //config: depends on INIT || LINUXRC
62 //config: If this option is enabled, init will try to give a controlling
63 //config: tty to any command which has leading hyphen (often it's "-/bin/sh").
64 //config: More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)".
65 //config: If device attached to STDIN_FILENO can be a ctty but is not yet
66 //config: a ctty for other session, it will become this process' ctty.
67 //config: This is not the traditional init behavour, but is often what you want
68 //config: in an embedded system where the console is only accessed during
69 //config: development or for maintenance.
70 //config: NB: using cttyhack applet may work better.
72 //config:config FEATURE_INIT_SYSLOG
73 //config: bool "Enable init to write to syslog"
75 //config: depends on INIT || LINUXRC
77 //config: If selected, some init messages are sent to syslog.
78 //config: Otherwise, they are sent to VT #5 if linux virtual tty is detected
79 //config: (if not, no separate logging is done).
81 //config:config FEATURE_INIT_QUIET
82 //config: bool "Be quiet on boot (no 'init started:' message)"
84 //config: depends on INIT || LINUXRC
86 //config:config FEATURE_INIT_COREDUMPS
87 //config: bool "Support dumping core for child processes (debugging only)"
88 //config: default n # not Y because this is a debug option
89 //config: depends on INIT || LINUXRC
91 //config: If this option is enabled and the file /.init_enable_core
92 //config: exists, then init will call setrlimit() to allow unlimited
93 //config: core file sizes. If this option is disabled, processes
94 //config: will not generate any core files.
96 //config:config INIT_TERMINAL_TYPE
97 //config: string "Initial terminal type"
98 //config: default "linux"
99 //config: depends on INIT || LINUXRC
101 //config: This is the initial value set by init for the TERM environment
102 //config: variable. This variable is used by programs which make use of
103 //config: extended terminal capabilities.
105 //config: Note that on Linux, init attempts to detect serial terminal and
106 //config: sets TERM to "vt102" if one is found.
108 //config:config FEATURE_INIT_MODIFY_CMDLINE
109 //config: bool "Clear init's command line"
111 //config: depends on INIT || LINUXRC
113 //config: When launched as PID 1 and after parsing its arguments, init
114 //config: wipes all the arguments but argv[0] and rewrites argv[0] to
115 //config: contain only "init", so that its command line appears solely as
116 //config: "init" in tools such as ps.
117 //config: If this option is set to Y, init will keep its original behavior,
118 //config: otherwise, all the arguments including argv[0] will be preserved,
119 //config: be they parsed or ignored by init.
120 //config: The original command-line used to launch init can then be
121 //config: retrieved in /proc/1/cmdline on Linux, for example.
123 //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
124 //applet:IF_LINUXRC(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
126 //kbuild:lib-$(CONFIG_INIT) += init.o
127 //kbuild:lib-$(CONFIG_LINUXRC) += init.o
129 #define DEBUG_SEGV_HANDLER 0
133 #include <sys/resource.h>
135 # include <linux/vt.h>
136 # include <sys/sysinfo.h>
138 #include "reboot.h" /* reboot() constants */
140 #if DEBUG_SEGV_HANDLER
142 # define _GNU_SOURCE 1
145 # include <execinfo.h>
146 # include <sys/ucontext.h>
149 /* Used only for sanitizing purposes in set_sane_term() below. On systems where
150 * the baud rate is stored in a separate field, we can safely disable them. */
156 /* Was a CONFIG_xxx option. A lot of people were building
157 * not fully functional init by switching it on! */
160 #define CONSOLE_NAME_SIZE 32
162 /* Default sysinit script. */
164 # define INIT_SCRIPT "/etc/init.d/rcS"
167 /* Each type of actions can appear many times. They will be
168 * handled in order. RESTART is an exception, only 1st is used.
170 /* Start these actions first and wait for completion */
172 /* Start these after SYSINIT and wait for completion */
174 /* Start these after WAIT and *dont* wait for completion */
177 * NB: while SYSINIT/WAIT/ONCE are being processed,
178 * SIGHUP ("reread /etc/inittab") will be processed only after
179 * each group of actions. If new inittab adds, say, a SYSINIT action,
180 * it will not be run, since init is already "past SYSINIT stage".
182 /* Start these after ONCE are started, restart on exit */
184 /* Like RESPAWN, but wait for <Enter> to be pressed on tty */
185 #define ASKFIRST 0x10
187 * Start these on SIGINT, and wait for completion.
188 * Then go back to respawning RESPAWN and ASKFIRST actions.
189 * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
191 #define CTRLALTDEL 0x20
193 * Start these before killing all processes in preparation for
194 * running RESTART actions or doing low-level halt/reboot/poweroff
195 * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
196 * Wait for completion before proceeding.
198 #define SHUTDOWN 0x40
200 * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
201 * then all processes are killed, then init exec's 1st RESTART action,
202 * replacing itself by it. If no RESTART action specified,
203 * SIGQUIT has no effect.
208 /* A linked list of init_actions, to be read from inittab */
210 struct init_action *next;
213 char terminal[CONSOLE_NAME_SIZE];
217 static struct init_action *init_action_list = NULL;
219 #if !ENABLE_FEATURE_INIT_SYSLOG
220 static const char *log_console = VC_5;
228 /* Print a message to the specified device.
229 * "where" may be bitwise-or'd from L_LOG | L_CONSOLE
230 * NB: careful, we can be called after vfork!
232 #define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
233 static void message(int where, const char *fmt, ...)
234 __attribute__ ((format(printf, 2, 3)));
235 static void message(int where, const char *fmt, ...)
242 va_start(arguments, fmt);
243 l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments);
244 if (l > sizeof(msg) - 2)
248 #if ENABLE_FEATURE_INIT_SYSLOG
251 /* Log the message to syslogd */
252 openlog(applet_name, 0, LOG_DAEMON);
253 /* don't print "\r" */
254 syslog(LOG_INFO, "%s", msg + 1);
263 /* Take full control of the log tty, and never close it.
264 * It's mine, all mine! Muhahahaha! */
265 static int log_fd = -1;
268 log_fd = STDERR_FILENO;
270 log_fd = device_open(log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY);
272 bb_error_msg("can't log to %s", log_console);
275 close_on_exec_on(log_fd);
279 full_write(log_fd, msg, l);
280 if (log_fd == STDERR_FILENO)
281 return; /* don't print dup messages */
285 if (where & L_CONSOLE) {
286 /* Send console messages to console so people will see them. */
287 full_write(STDERR_FILENO, msg, l);
291 static void console_init(void)
298 s = getenv("CONSOLE");
300 s = getenv("console");
301 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
302 /* BSD people say their kernels do not open fd 0,1,2; they need this: */
304 s = (char*)"/dev/console";
307 int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY);
309 dup2(fd, STDIN_FILENO);
310 dup2(fd, STDOUT_FILENO);
311 xmove_fd(fd, STDERR_FILENO);
313 dbg_message(L_LOG, "console='%s'", s);
315 /* Make sure fd 0,1,2 are not closed
316 * (so that they won't be used by future opens) */
318 // Users report problems
319 // /* Make sure init can't be blocked by writing to stderr */
320 // fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK);
325 if (ioctl(STDIN_FILENO, VT_OPENQRY, &vtno) != 0) {
326 /* Not a linux terminal, probably serial console.
327 * Force the TERM setting to vt102
328 * if TERM is set to linux (the default) */
329 if (!s || strcmp(s, "linux") == 0)
330 putenv((char*)"TERM=vt102");
331 # if !ENABLE_FEATURE_INIT_SYSLOG
337 putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE);
340 /* Set terminal settings to reasonable defaults.
341 * NB: careful, we can be called after vfork! */
342 static void set_sane_term(void)
346 tcgetattr(STDIN_FILENO, &tty);
348 /* set control chars */
349 tty.c_cc[VINTR] = 3; /* C-c */
350 tty.c_cc[VQUIT] = 28; /* C-\ */
351 tty.c_cc[VERASE] = 127; /* C-? */
352 tty.c_cc[VKILL] = 21; /* C-u */
353 tty.c_cc[VEOF] = 4; /* C-d */
354 tty.c_cc[VSTART] = 17; /* C-q */
355 tty.c_cc[VSTOP] = 19; /* C-s */
356 tty.c_cc[VSUSP] = 26; /* C-z */
359 /* use line discipline 0 */
363 /* Make it be sane */
367 /* added CRTSCTS to fix Debian bug 528560 */
368 tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS;
369 tty.c_cflag |= CREAD | HUPCL | CLOCAL;
372 tty.c_iflag = ICRNL | IXON | IXOFF;
375 tty.c_oflag = OPOST | ONLCR;
378 tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN;
380 tcsetattr_stdin_TCSANOW(&tty);
383 /* Open the new terminal device.
384 * NB: careful, we can be called after vfork! */
385 static int open_stdio_to_tty(const char* tty_name)
387 /* empty tty_name means "use init's tty", else... */
392 /* fd can be only < 0 or 0: */
393 fd = device_open(tty_name, O_RDWR);
395 message(L_LOG | L_CONSOLE, "can't open %s: %s",
396 tty_name, strerror(errno));
397 return 0; /* failure */
399 dup2(STDIN_FILENO, STDOUT_FILENO);
400 dup2(STDIN_FILENO, STDERR_FILENO);
403 return 1; /* success */
406 static void reset_sighandlers_and_unblock_sigs(void)
418 sigprocmask_allsigs(SIG_UNBLOCK);
421 /* Wrapper around exec:
423 * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
424 * Otherwise splits words on whitespace, deals with leading dash,
425 * and uses plain exec().
426 * NB: careful, we can be called after vfork!
428 static void init_exec(const char *command)
430 /* +8 allows to write VLA sizes below more efficiently: */
431 unsigned command_size = strlen(command) + 8;
432 /* strlen(command) + strlen("exec ")+1: */
433 char buf[command_size];
434 /* strlen(command) / 2 + 4: */
435 char *cmd[command_size / 2];
438 dash = (command[0] == '-' /* maybe? && command[1] == '/' */);
441 /* See if any special /bin/sh requiring characters are present */
442 if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
443 sprintf(buf, "exec %s", command); /* excluding "-" */
444 /* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
445 cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash);
446 cmd[1] = (char*)"-c";
449 command = LIBBB_DEFAULT_LOGIN_SHELL + 1;
451 /* Convert command (char*) into cmd (char**, one word per string) */
454 next = strcpy(buf, command - dash); /* command including "-" */
455 command = next + dash;
456 while ((word = strsep(&next, " \t")) != NULL) {
457 if (*word != '\0') { /* not two spaces/tabs together? */
464 /* If we saw leading "-", it is interactive shell.
465 * Try harder to give it a controlling tty.
467 if (ENABLE_FEATURE_INIT_SCTTY && dash) {
468 /* _Attempt_ to make stdin a controlling tty. */
469 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/);
471 /* Here command never contains the dash, cmd[0] might */
472 BB_EXECVP(command, cmd);
473 message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno));
474 /* returns if execvp fails */
477 /* Used only by run_actions */
478 static pid_t run(const struct init_action *a)
482 /* Careful: don't be affected by a signal in vforked child */
483 sigprocmask_allsigs(SIG_BLOCK);
484 if (BB_MMU && (a->action_type & ASKFIRST))
489 message(L_LOG | L_CONSOLE, "can't fork");
491 sigprocmask_allsigs(SIG_UNBLOCK);
492 return pid; /* Parent or error */
497 /* Reset signal handlers that were set by the parent process */
498 reset_sighandlers_and_unblock_sigs();
500 /* Create a new session and make ourself the process group leader */
503 /* Open the new terminal device */
504 if (!open_stdio_to_tty(a->terminal))
507 /* NB: on NOMMU we can't wait for input in child, so
508 * "askfirst" will work the same as "respawn". */
509 if (BB_MMU && (a->action_type & ASKFIRST)) {
510 static const char press_enter[] ALIGN1 =
511 #ifdef CUSTOMIZED_BANNER
512 #include CUSTOMIZED_BANNER
514 "\nPlease press Enter to activate this console. ";
517 * Save memory by not exec-ing anything large (like a shell)
518 * before the user wants it. This is critical if swap is not
519 * enabled and the system has low memory. Generally this will
520 * be run on the second virtual console, and the first will
521 * be allowed to start a shell or whatever an init script
524 dbg_message(L_LOG, "waiting for enter to start '%s'"
525 "(pid %d, tty '%s')\n",
526 a->command, getpid(), a->terminal);
527 full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1);
528 while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n')
533 * When a file named /.init_enable_core exists, setrlimit is called
534 * before processes are spawned to set core file size as unlimited.
535 * This is for debugging only. Don't use this is production, unless
536 * you want core dumps lying about....
538 if (ENABLE_FEATURE_INIT_COREDUMPS) {
539 if (access("/.init_enable_core", F_OK) == 0) {
541 limit.rlim_cur = RLIM_INFINITY;
542 limit.rlim_max = RLIM_INFINITY;
543 setrlimit(RLIMIT_CORE, &limit);
547 /* Log the process name and args */
548 message(L_LOG, "starting pid %u, tty '%s': '%s'",
549 (int)getpid(), a->terminal, a->command);
551 /* Now run it. The new program will take over this PID,
552 * so nothing further in init.c should be run. */
553 init_exec(a->command);
554 /* We're still here? Some error happened. */
558 static struct init_action *mark_terminated(pid_t pid)
560 struct init_action *a;
563 update_utmp_DEAD_PROCESS(pid);
564 for (a = init_action_list; a; a = a->next) {
574 static void waitfor(pid_t pid)
576 /* waitfor(run(x)): protect against failed fork inside run() */
580 /* Wait for any child (prevent zombies from exiting orphaned processes)
581 * but exit the loop only when specified one has exited. */
583 pid_t wpid = wait(NULL);
584 mark_terminated(wpid);
585 /* Unsafe. SIGTSTP handler might have wait'ed it already */
586 /*if (wpid == pid) break;*/
593 /* Run all commands of a particular type */
594 static void run_actions(int action_type)
596 struct init_action *a;
598 for (a = init_action_list; a; a = a->next) {
599 if (!(a->action_type & action_type))
602 if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
604 if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
607 if (a->action_type & (RESPAWN | ASKFIRST)) {
608 /* Only run stuff with pid == 0. If pid != 0,
609 * it is already running
617 static void new_init_action(uint8_t action_type, const char *command, const char *cons)
619 struct init_action *a, **nextp;
623 * ::shutdown:umount -a -r
624 * ::shutdown:swapoff -a
626 * ::shutdown:swapoff -a
627 * ::shutdown:umount -a -r
628 * On reload, we must ensure entries end up in correct order.
629 * To achieve that, if we find a matching entry, we move it
632 nextp = &init_action_list;
633 while ((a = *nextp) != NULL) {
634 /* Don't enter action if it's already in the list.
635 * This prevents losing running RESPAWNs.
637 if (strcmp(a->command, command) == 0
638 && strcmp(a->terminal, cons) == 0
640 /* Remove from list */
642 /* Find the end of the list */
643 while (*nextp != NULL)
644 nextp = &(*nextp)->next;
651 a = xzalloc(sizeof(*a) + strlen(command));
653 /* Append to the end of the list */
656 a->action_type = action_type;
657 strcpy(a->command, command);
658 safe_strncpy(a->terminal, cons, sizeof(a->terminal));
659 dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%x tty='%s'\n",
660 a->command, a->action_type, a->terminal);
663 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
664 * then parse_inittab() simply adds in some default
665 * actions (i.e., runs INIT_SCRIPT and then starts a pair
666 * of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB
667 * _is_ defined, but /etc/inittab is missing, this
668 * results in the same set of default behaviors.
670 static void parse_inittab(void)
672 #if ENABLE_FEATURE_USE_INITTAB
674 parser_t *parser = config_open2("/etc/inittab", fopen_for_read);
679 /* No inittab file - set up some default behavior */
681 new_init_action(SYSINIT, INIT_SCRIPT, "");
682 /* Askfirst shell on tty1-4 */
683 new_init_action(ASKFIRST, bb_default_login_shell, "");
684 //TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
685 new_init_action(ASKFIRST, bb_default_login_shell, VC_2);
686 new_init_action(ASKFIRST, bb_default_login_shell, VC_3);
687 new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
688 /* Reboot on Ctrl-Alt-Del */
689 new_init_action(CTRLALTDEL, "reboot", "");
690 /* Umount all filesystems on halt/reboot */
691 new_init_action(SHUTDOWN, "umount -a -r", "");
692 /* Swapoff on halt/reboot */
693 new_init_action(SHUTDOWN, "swapoff -a", "");
694 /* Restart init when a QUIT is received */
695 new_init_action(RESTART, "init", "");
699 #if ENABLE_FEATURE_USE_INITTAB
700 /* optional_tty:ignored_runlevel:action:command
701 * Delims are not to be collapsed and need exactly 4 tokens
703 while (config_read(parser, token, 4, 0, "#:",
704 PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
705 /* order must correspond to SYSINIT..RESTART constants */
706 static const char actions[] ALIGN1 =
707 "sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
708 "ctrlaltdel\0""shutdown\0""restart\0";
710 char *tty = token[0];
712 if (!token[3]) /* less than 4 tokens */
714 action = index_in_strings(actions, token[2]);
715 if (action < 0 || !token[3][0]) /* token[3]: command */
717 /* turn .*TTY -> /dev/TTY */
719 tty = concat_path_file("/dev/", skip_dev_pfx(tty));
721 new_init_action(1 << action, token[3], tty);
726 message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d",
729 config_close(parser);
733 static void pause_and_low_level_reboot(unsigned magic) NORETURN;
734 static void pause_and_low_level_reboot(unsigned magic)
738 /* Allow time for last message to reach serial console, etc */
741 /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
742 * in linux/kernel/sys.c, which can cause the machine to panic when
743 * the init process exits... */
745 if (pid == 0) { /* child */
753 static void run_shutdown_and_kill_processes(void)
755 /* Run everything to be run at "shutdown". This is done _prior_
756 * to killing everything, in case people wish to use scripts to
757 * shut things down gracefully... */
758 run_actions(SHUTDOWN);
760 message(L_CONSOLE | L_LOG, "The system is going down NOW!");
762 /* Send signals to every process _except_ pid 1 */
764 message(L_CONSOLE, "Sent SIG%s to all processes", "TERM");
769 message(L_CONSOLE, "Sent SIG%s to all processes", "KILL");
771 /*sleep(1); - callers take care about making a pause */
774 /* Signal handling by init:
776 * For process with PID==1, on entry kernel sets all signals to SIG_DFL
777 * and unmasks all signals. However, for process with PID==1,
778 * default action (SIG_DFL) on any signal is to ignore it,
779 * even for special signals SIGKILL and SIGCONT.
780 * Also, any signal can be caught or blocked.
781 * (but SIGSTOP is still handled specially, at least in 2.6.20)
783 * We install two kinds of handlers, "immediate" and "delayed".
785 * Immediate handlers execute at any time, even while, say, sysinit
788 * Delayed handlers just set a flag variable. The variable is checked
789 * in the main loop and acted upon.
791 * halt/poweroff/reboot and restart have immediate handlers.
792 * They only traverse linked list of struct action's, never modify it,
793 * this should be safe to do even in signal handler. Also they
796 * SIGSTOP and SIGTSTP have immediate handlers. They just wait
797 * for SIGCONT to happen.
799 * SIGHUP has a delayed handler, because modifying linked list
800 * of struct action's from a signal handler while it is manipulated
801 * by the program may be disastrous.
803 * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
804 * it to happen even somewhere inside "sysinit" would be a bit awkward.
806 * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
807 * and only one will be remembered and acted upon.
810 /* The SIGPWR/SIGUSR[12]/SIGTERM handler */
811 static void halt_reboot_pwoff(int sig) NORETURN;
812 static void halt_reboot_pwoff(int sig)
817 /* We may call run() and it unmasks signals,
818 * including the one masked inside this signal handler.
819 * Testcase which would start multiple reboot scripts:
820 * while true; do reboot; done
823 reset_sighandlers_and_unblock_sigs();
825 run_shutdown_and_kill_processes();
829 if (sig == SIGTERM) {
832 } else if (sig == SIGUSR2) {
836 message(L_CONSOLE, "Requesting system %s", m);
837 pause_and_low_level_reboot(rb);
841 /* Handler for QUIT - exec "restart" action,
842 * else (no such action defined) do nothing */
843 static void exec_restart_action(void)
845 struct init_action *a;
847 for (a = init_action_list; a; a = a->next) {
848 if (!(a->action_type & RESTART))
851 /* Starting from here, we won't return.
852 * Thus don't need to worry about preserving errno
856 reset_sighandlers_and_unblock_sigs();
858 run_shutdown_and_kill_processes();
861 /* Allow Ctrl-Alt-Del to reboot the system.
862 * This is how kernel sets it up for init, we follow suit.
864 reboot(RB_ENABLE_CAD); /* misnomer */
867 if (open_stdio_to_tty(a->terminal)) {
868 dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
869 /* Theoretically should be safe.
870 * But in practice, kernel bugs may leave
871 * unkillable processes, and wait() may block forever.
872 * Oh well. Hoping "new" init won't be too surprised
873 * by having children it didn't create.
875 //while (wait(NULL) > 0)
877 init_exec(a->command);
879 /* Open or exec failed */
880 pause_and_low_level_reboot(RB_HALT_SYSTEM);
885 /* The SIGSTOP/SIGTSTP handler
886 * NB: inside it, all signals except SIGCONT are masked
887 * via appropriate setup in sigaction().
889 static void stop_handler(int sig UNUSED_PARAM)
891 smallint saved_bb_got_signal;
894 saved_bb_got_signal = bb_got_signal;
896 signal(SIGCONT, record_signo);
901 if (bb_got_signal == SIGCONT)
903 /* NB: this can accidentally wait() for a process
904 * which we waitfor() elsewhere! waitfor() must have
905 * code which is resilient against this.
907 wpid = wait_any_nohang(NULL);
908 mark_terminated(wpid);
912 signal(SIGCONT, SIG_DFL);
914 bb_got_signal = saved_bb_got_signal;
917 #if ENABLE_FEATURE_USE_INITTAB
918 static void reload_inittab(void)
920 struct init_action *a, **nextp;
922 message(L_LOG, "reloading /etc/inittab");
924 /* Disable old entries */
925 for (a = init_action_list; a; a = a->next)
928 /* Append new entries, or modify existing entries
929 * (incl. setting a->action_type) if cmd and device name
930 * match new ones. End result: only entries with
931 * a->action_type == 0 are stale.
935 #if ENABLE_FEATURE_KILL_REMOVED
936 /* Kill stale entries */
937 /* Be nice and send SIGTERM first */
938 for (a = init_action_list; a; a = a->next)
939 if (a->action_type == 0 && a->pid != 0)
940 kill(a->pid, SIGTERM);
941 if (CONFIG_FEATURE_KILL_DELAY) {
942 /* NB: parent will wait in NOMMU case */
943 if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
944 sleep(CONFIG_FEATURE_KILL_DELAY);
945 for (a = init_action_list; a; a = a->next)
946 if (a->action_type == 0 && a->pid != 0)
947 kill(a->pid, SIGKILL);
953 /* Remove stale entries and SYSINIT entries.
954 * We never rerun SYSINIT entries anyway,
955 * removing them too saves a few bytes
957 nextp = &init_action_list;
958 while ((a = *nextp) != NULL) {
960 * Why pid == 0 check?
961 * Process can be removed from inittab and added *later*.
962 * If we delete its entry but process still runs,
963 * duplicate is spawned when the entry is re-added.
965 if ((a->action_type & ~SYSINIT) == 0 && a->pid == 0) {
974 /* run_actions(RESPAWN | ASKFIRST); */
975 /* - we return to main loop, which does this automagically */
979 static int check_delayed_sigs(void)
984 smallint sig = bb_got_signal;
990 #if ENABLE_FEATURE_USE_INITTAB
995 run_actions(CTRLALTDEL);
996 if (sig == SIGQUIT) {
997 exec_restart_action();
998 /* returns only if no restart action defined */
1008 halt_reboot_pwoff(sig);
1013 #if DEBUG_SEGV_HANDLER
1015 void handle_sigsegv(int sig, siginfo_t *info, void *ucontext)
1021 ip = uc->uc_mcontext.gregs[REG_EIP];
1022 fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n",
1024 /* this is void*, but using %p would print "(null)"
1025 * even for ptrs which are not exactly 0, but, say, 0x123:
1027 (long)info->si_addr,
1030 /* glibc extension */
1033 size = backtrace(array, 50);
1034 backtrace_symbols_fd(array, size, 2);
1036 for (;;) sleep(9999);
1040 static void sleep_much(void)
1042 sleep(30 * 24*60*60);
1045 int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1046 int init_main(int argc UNUSED_PARAM, char **argv)
1048 if (argv[1] && strcmp(argv[1], "-q") == 0) {
1049 return kill(1, SIGHUP);
1052 #if DEBUG_SEGV_HANDLER
1054 struct sigaction sa;
1055 memset(&sa, 0, sizeof(sa));
1056 sa.sa_sigaction = handle_sigsegv;
1057 sa.sa_flags = SA_SIGINFO;
1058 sigaction(SIGSEGV, &sa, NULL);
1059 sigaction(SIGILL, &sa, NULL);
1060 sigaction(SIGFPE, &sa, NULL);
1061 sigaction(SIGBUS, &sa, NULL);
1066 /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
1068 && (!ENABLE_LINUXRC || applet_name[0] != 'l') /* not linuxrc? */
1070 bb_error_msg_and_die("must be run as PID 1");
1072 #ifdef RB_DISABLE_CAD
1073 /* Turn off rebooting via CTL-ALT-DEL - we get a
1074 * SIGINT on CAD so we can shut things down gracefully... */
1075 reboot(RB_DISABLE_CAD); /* misnomer */
1079 /* If, say, xmalloc would ever die, we don't want to oops kernel
1081 * NB: we set die_func *after* PID 1 check and bb_show_usage.
1082 * Otherwise, for example, "init u" ("please rexec yourself"
1083 * command for sysvinit) will show help text (which isn't too bad),
1084 * *and sleep forever* (which is bad!)
1086 die_func = sleep_much;
1088 /* Figure out where the default console should be */
1094 /* Make sure environs is set to something sane */
1095 putenv((char *) "HOME=/");
1096 putenv((char *) bb_PATH_root_path);
1097 putenv((char *) "SHELL=/bin/sh");
1098 putenv((char *) "USER=root"); /* needed? why? */
1101 xsetenv("RUNLEVEL", argv[1]);
1103 #if !ENABLE_FEATURE_INIT_QUIET
1105 message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
1109 /* It's 2013, does anyone really still depend on this? */
1110 /* If you do, consider adding swapon to sysinit actions then! */
1111 /* struct sysinfo is linux-specific */
1113 /* Make sure there is enough memory to do something useful. */
1114 /*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ {
1115 struct sysinfo info;
1117 if (sysinfo(&info) == 0
1118 && (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024
1120 message(L_CONSOLE, "Low memory, forcing swapon");
1121 /* swapon -a requires /proc typically */
1122 new_init_action(SYSINIT, "mount -t proc proc /proc", "");
1123 /* Try to turn on swap */
1124 new_init_action(SYSINIT, "swapon -a", "");
1125 run_actions(SYSINIT); /* wait and removing */
1131 /* Check if we are supposed to be in single user mode */
1133 && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
1135 /* ??? shouldn't we set RUNLEVEL="b" here? */
1136 /* Start a shell on console */
1137 new_init_action(RESPAWN, bb_default_login_shell, "");
1139 /* Not in single user mode - see what inittab says */
1141 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
1142 * then parse_inittab() simply adds in some default
1143 * actions (i.e., INIT_SCRIPT and a pair
1144 * of "askfirst" shells) */
1149 if (getenv("SELINUX_INIT") == NULL) {
1152 putenv((char*)"SELINUX_INIT=YES");
1153 if (selinux_init_load_policy(&enforce) == 0) {
1154 BB_EXECVP(argv[0], argv);
1155 } else if (enforce > 0) {
1156 /* SELinux in enforcing mode but load_policy failed */
1157 message(L_CONSOLE, "can't load SELinux Policy. "
1158 "Machine is in enforcing mode. Halting now.");
1159 return EXIT_FAILURE;
1164 if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE) {
1165 /* Make the command line just say "init" - that's all, nothing else */
1166 strncpy(argv[0], "init", strlen(argv[0]));
1167 /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
1172 /* Set up signal handlers */
1174 struct sigaction sa;
1176 /* Stop handler must allow only SIGCONT inside itself */
1177 memset(&sa, 0, sizeof(sa));
1178 sigfillset(&sa.sa_mask);
1179 sigdelset(&sa.sa_mask, SIGCONT);
1180 sa.sa_handler = stop_handler;
1181 /* NB: sa_flags doesn't have SA_RESTART.
1182 * It must be able to interrupt wait().
1184 sigaction_set(SIGTSTP, &sa); /* pause */
1185 /* Does not work as intended, at least in 2.6.20.
1186 * SIGSTOP is simply ignored by init:
1188 sigaction_set(SIGSTOP, &sa); /* pause */
1190 /* These signals must interrupt wait(),
1191 * setting handler without SA_RESTART flag.
1193 bb_signals_recursive_norestart(0
1194 + (1 << SIGINT) /* Ctrl-Alt-Del */
1195 + (1 << SIGQUIT) /* re-exec another init */
1197 + (1 << SIGPWR) /* halt */
1199 + (1 << SIGUSR1) /* halt */
1200 + (1 << SIGTERM) /* reboot */
1201 + (1 << SIGUSR2) /* poweroff */
1202 #if ENABLE_FEATURE_USE_INITTAB
1203 + (1 << SIGHUP) /* reread /etc/inittab */
1208 /* Now run everything that needs to be run */
1209 /* First run the sysinit command */
1210 run_actions(SYSINIT);
1211 check_delayed_sigs();
1212 /* Next run anything that wants to block */
1214 check_delayed_sigs();
1215 /* Next run anything to be run only once */
1218 /* Now run the looping stuff for the rest of forever.
1223 maybe_WNOHANG = check_delayed_sigs();
1225 /* (Re)run the respawn/askfirst stuff */
1226 run_actions(RESPAWN | ASKFIRST);
1227 maybe_WNOHANG |= check_delayed_sigs();
1229 /* Don't consume all CPU time - sleep a bit */
1231 maybe_WNOHANG |= check_delayed_sigs();
1233 /* Wait for any child process(es) to exit.
1235 * If check_delayed_sigs above reported that a signal
1236 * was caught, wait will be nonblocking. This ensures
1237 * that if SIGHUP has reloaded inittab, respawn and askfirst
1238 * actions will not be delayed until next child death.
1241 maybe_WNOHANG = WNOHANG;
1244 struct init_action *a;
1246 /* If signals happen _in_ the wait, they interrupt it,
1247 * bb_signals_recursive_norestart set them up that way
1249 wpid = waitpid(-1, NULL, maybe_WNOHANG);
1253 a = mark_terminated(wpid);
1255 message(L_LOG, "process '%s' (pid %d) exited. "
1256 "Scheduling for restart.",
1259 /* See if anyone else is waiting to be reaped */
1260 maybe_WNOHANG = WNOHANG;
1265 //usage:#define linuxrc_trivial_usage NOUSAGE_STR
1266 //usage:#define linuxrc_full_usage ""
1268 //usage:#define init_trivial_usage
1270 //usage:#define init_full_usage "\n\n"
1271 //usage: "Init is the first process started during boot. It never exits."
1272 //usage: IF_FEATURE_USE_INITTAB(
1273 //usage: "\n""It (re)spawns children according to /etc/inittab."
1275 //usage: IF_NOT_FEATURE_USE_INITTAB(
1276 //usage: "\n""This version of init doesn't use /etc/inittab,"
1277 //usage: "\n""has fixed set of processed to run."
1280 //usage:#define init_notes_usage
1281 //usage: "This version of init is designed to be run only by the kernel.\n"
1283 //usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
1284 //usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
1285 //usage: "runlevels, use sysvinit.\n"
1287 //usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n"
1288 //usage: "it has the following default behavior:\n"
1290 //usage: " ::sysinit:/etc/init.d/rcS\n"
1291 //usage: " ::askfirst:/bin/sh\n"
1292 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1293 //usage: " ::shutdown:/sbin/swapoff -a\n"
1294 //usage: " ::shutdown:/bin/umount -a -r\n"
1295 //usage: " ::restart:/sbin/init\n"
1296 //usage: " tty2::askfirst:/bin/sh\n"
1297 //usage: " tty3::askfirst:/bin/sh\n"
1298 //usage: " tty4::askfirst:/bin/sh\n"
1300 //usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
1302 //usage: " <id>:<runlevels>:<action>:<process>\n"
1306 //usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n"
1307 //usage: " The id field is used by BusyBox init to specify the controlling tty for\n"
1308 //usage: " the specified process to run on. The contents of this field are\n"
1309 //usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n"
1310 //usage: " be unique, although if it isn't you may have strange results. If this\n"
1311 //usage: " field is left blank, then the init's stdin/out will be used.\n"
1313 //usage: " <runlevels>:\n"
1315 //usage: " The runlevels field is completely ignored.\n"
1317 //usage: " <action>:\n"
1319 //usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n"
1320 //usage: " once, restart, ctrlaltdel, and shutdown.\n"
1322 //usage: " The available actions can be classified into two groups: actions\n"
1323 //usage: " that are run only once, and actions that are re-run when the specified\n"
1324 //usage: " process exits.\n"
1326 //usage: " Run only-once actions:\n"
1328 //usage: " 'sysinit' is the first item run on boot. init waits until all\n"
1329 //usage: " sysinit actions are completed before continuing. Following the\n"
1330 //usage: " completion of all sysinit actions, all 'wait' actions are run.\n"
1331 //usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n"
1332 //usage: " the specified task completes. 'once' actions are asynchronous,\n"
1333 //usage: " therefore, init does not wait for them to complete. 'restart' is\n"
1334 //usage: " the action taken to restart the init process. By default this should\n"
1335 //usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n"
1336 //usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
1337 //usage: " actions are run when the system detects that someone on the system\n"
1338 //usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
1339 //usage: " wants to run 'reboot' at this point to cause the system to reboot.\n"
1340 //usage: " Finally the 'shutdown' action specifies the actions to taken when\n"
1341 //usage: " init is told to reboot. Unmounting filesystems and disabling swap\n"
1342 //usage: " is a very good here.\n"
1344 //usage: " Run repeatedly actions:\n"
1346 //usage: " 'respawn' actions are run after the 'once' actions. When a process\n"
1347 //usage: " started with a 'respawn' action exits, init automatically restarts\n"
1348 //usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n"
1349 //usage: " respawning out of control. The 'askfirst' actions acts just like\n"
1350 //usage: " respawn, except that before running the specified process it\n"
1351 //usage: " displays the line \"Please press Enter to activate this console.\"\n"
1352 //usage: " and then waits for the user to press enter before starting the\n"
1353 //usage: " specified process.\n"
1355 //usage: " Unrecognized actions (like initdefault) will cause init to emit an\n"
1356 //usage: " error message, and then go along with its business. All actions are\n"
1357 //usage: " run in the order they appear in /etc/inittab.\n"
1359 //usage: " <process>:\n"
1361 //usage: " Specifies the process to be executed and its command line.\n"
1363 //usage: "Example /etc/inittab file:\n"
1365 //usage: " # This is run first except when booting in single-user mode\n"
1367 //usage: " ::sysinit:/etc/init.d/rcS\n"
1369 //usage: " # /bin/sh invocations on selected ttys\n"
1371 //usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n"
1372 //usage: " ::askfirst:-/bin/sh\n"
1373 //usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n"
1374 //usage: " tty2::askfirst:-/bin/sh\n"
1375 //usage: " tty3::askfirst:-/bin/sh\n"
1376 //usage: " tty4::askfirst:-/bin/sh\n"
1378 //usage: " # /sbin/getty invocations for selected ttys\n"
1380 //usage: " tty4::respawn:/sbin/getty 38400 tty4\n"
1381 //usage: " tty5::respawn:/sbin/getty 38400 tty5\n"
1384 //usage: " # Example of how to put a getty on a serial line (for a terminal)\n"
1386 //usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
1387 //usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
1389 //usage: " # Example how to put a getty on a modem line\n"
1390 //usage: " #::respawn:/sbin/getty 57600 ttyS2\n"
1392 //usage: " # Stuff to do when restarting the init process\n"
1393 //usage: " ::restart:/sbin/init\n"
1395 //usage: " # Stuff to do before rebooting\n"
1396 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1397 //usage: " ::shutdown:/bin/umount -a -r\n"
1398 //usage: " ::shutdown:/sbin/swapoff -a\n"