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 "Support running init from within an 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:config FEATURE_EXTRA_QUIET
78 //config: bool "Be _extra_ quiet on boot"
80 //config: depends on INIT || LINUXRC
82 //config: Prevent init from logging some messages to the console during boot.
84 //config:config FEATURE_INIT_COREDUMPS
85 //config: bool "Support dumping core for child processes (debugging only)"
87 //config: depends on INIT || LINUXRC
89 //config: If this option is enabled and the file /.init_enable_core
90 //config: exists, then init will call setrlimit() to allow unlimited
91 //config: core file sizes. If this option is disabled, processes
92 //config: will not generate any core files.
94 //config:config INIT_TERMINAL_TYPE
95 //config: string "Initial terminal type"
96 //config: default "linux"
97 //config: depends on INIT || LINUXRC
99 //config: This is the initial value set by init for the TERM environment
100 //config: variable. This variable is used by programs which make use of
101 //config: extended terminal capabilities.
103 //config: Note that on Linux, init attempts to detect serial terminal and
104 //config: sets TERM to "vt102" if one is found.
106 //config:config FEATURE_INIT_MODIFY_CMDLINE
107 //config: bool "Modify the command-line to \"init\""
109 //config: depends on INIT || LINUXRC
111 //config: When launched as PID 1 and after parsing its arguments, init
112 //config: wipes all the arguments but argv[0] and rewrites argv[0] to
113 //config: contain only "init", so that its command-line appears solely as
114 //config: "init" in tools such as ps.
115 //config: If this option is set to Y, init will keep its original behavior,
116 //config: otherwise, all the arguments including argv[0] will be preserved,
117 //config: be they parsed or ignored by init.
118 //config: The original command-line used to launch init can then be
119 //config: retrieved in /proc/1/cmdline on Linux, for example.
121 //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
122 //applet:IF_LINUXRC(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
124 //kbuild:lib-$(CONFIG_INIT) += init.o
125 //kbuild:lib-$(CONFIG_LINUXRC) += init.o
127 #define DEBUG_SEGV_HANDLER 0
131 #include <sys/resource.h>
133 # include <linux/vt.h>
134 # include <sys/sysinfo.h>
136 #include "reboot.h" /* reboot() constants */
138 #if DEBUG_SEGV_HANDLER
140 # define _GNU_SOURCE 1
143 # include <execinfo.h>
144 # include <sys/ucontext.h>
147 /* Used only for sanitizing purposes in set_sane_term() below. On systems where
148 * the baud rate is stored in a separate field, we can safely disable them. */
154 /* Was a CONFIG_xxx option. A lot of people were building
155 * not fully functional init by switching it on! */
158 #define CONSOLE_NAME_SIZE 32
160 /* Default sysinit script. */
162 # define INIT_SCRIPT "/etc/init.d/rcS"
165 /* Each type of actions can appear many times. They will be
166 * handled in order. RESTART is an exception, only 1st is used.
168 /* Start these actions first and wait for completion */
170 /* Start these after SYSINIT and wait for completion */
172 /* Start these after WAIT and *dont* wait for completion */
175 * NB: while SYSINIT/WAIT/ONCE are being processed,
176 * SIGHUP ("reread /etc/inittab") will be processed only after
177 * each group of actions. If new inittab adds, say, a SYSINIT action,
178 * it will not be run, since init is already "past SYSINIT stage".
180 /* Start these after ONCE are started, restart on exit */
182 /* Like RESPAWN, but wait for <Enter> to be pressed on tty */
183 #define ASKFIRST 0x10
185 * Start these on SIGINT, and wait for completion.
186 * Then go back to respawning RESPAWN and ASKFIRST actions.
187 * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
189 #define CTRLALTDEL 0x20
191 * Start these before killing all processes in preparation for
192 * running RESTART actions or doing low-level halt/reboot/poweroff
193 * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
194 * Wait for completion before proceeding.
196 #define SHUTDOWN 0x40
198 * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
199 * then all processes are killed, then init exec's 1st RESTART action,
200 * replacing itself by it. If no RESTART action specified,
201 * SIGQUIT has no effect.
206 /* A linked list of init_actions, to be read from inittab */
208 struct init_action
*next
;
211 char terminal
[CONSOLE_NAME_SIZE
];
215 static struct init_action
*init_action_list
= NULL
;
217 static const char *log_console
= VC_5
;
224 /* Print a message to the specified device.
225 * "where" may be bitwise-or'd from L_LOG | L_CONSOLE
226 * NB: careful, we can be called after vfork!
228 #define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
229 static void message(int where
, const char *fmt
, ...)
230 __attribute__ ((format(printf
, 2, 3)));
231 static void message(int where
, const char *fmt
, ...)
238 va_start(arguments
, fmt
);
239 l
= 1 + vsnprintf(msg
+ 1, sizeof(msg
) - 2, fmt
, arguments
);
240 if (l
> sizeof(msg
) - 2)
244 #if ENABLE_FEATURE_INIT_SYSLOG
247 /* Log the message to syslogd */
248 openlog(applet_name
, 0, LOG_DAEMON
);
249 /* don't print "\r" */
250 syslog(LOG_INFO
, "%s", msg
+ 1);
257 static int log_fd
= -1;
261 /* Take full control of the log tty, and never close it.
262 * It's mine, all mine! Muhahahaha! */
265 log_fd
= STDERR_FILENO
;
267 log_fd
= device_open(log_console
, O_WRONLY
| O_NONBLOCK
| O_NOCTTY
);
269 bb_error_msg("can't log to %s", log_console
);
272 close_on_exec_on(log_fd
);
277 full_write(log_fd
, msg
, l
);
278 if (log_fd
== STDERR_FILENO
)
279 return; /* don't print dup messages */
284 if (where
& L_CONSOLE
) {
285 /* Send console messages to console so people will see them. */
286 full_write(STDERR_FILENO
, msg
, l
);
290 static void console_init(void)
297 s
= getenv("CONSOLE");
299 s
= getenv("console");
301 int fd
= open(s
, O_RDWR
| O_NONBLOCK
| O_NOCTTY
);
303 dup2(fd
, STDIN_FILENO
);
304 dup2(fd
, STDOUT_FILENO
);
305 xmove_fd(fd
, STDERR_FILENO
);
307 dbg_message(L_LOG
, "console='%s'", s
);
309 /* Make sure fd 0,1,2 are not closed
310 * (so that they won't be used by future opens) */
312 // Users report problems
313 // /* Make sure init can't be blocked by writing to stderr */
314 // fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK);
319 if (ioctl(STDIN_FILENO
, VT_OPENQRY
, &vtno
) != 0) {
320 /* Not a linux terminal, probably serial console.
321 * Force the TERM setting to vt102
322 * if TERM is set to linux (the default) */
323 if (!s
|| strcmp(s
, "linux") == 0)
324 putenv((char*)"TERM=vt102");
325 if (!ENABLE_FEATURE_INIT_SYSLOG
)
330 putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE
);
333 /* Set terminal settings to reasonable defaults.
334 * NB: careful, we can be called after vfork! */
335 static void set_sane_term(void)
339 tcgetattr(STDIN_FILENO
, &tty
);
341 /* set control chars */
342 tty
.c_cc
[VINTR
] = 3; /* C-c */
343 tty
.c_cc
[VQUIT
] = 28; /* C-\ */
344 tty
.c_cc
[VERASE
] = 127; /* C-? */
345 tty
.c_cc
[VKILL
] = 21; /* C-u */
346 tty
.c_cc
[VEOF
] = 4; /* C-d */
347 tty
.c_cc
[VSTART
] = 17; /* C-q */
348 tty
.c_cc
[VSTOP
] = 19; /* C-s */
349 tty
.c_cc
[VSUSP
] = 26; /* C-z */
352 /* use line discipline 0 */
356 /* Make it be sane */
360 /* added CRTSCTS to fix Debian bug 528560 */
361 tty
.c_cflag
&= CBAUD
| CBAUDEX
| CSIZE
| CSTOPB
| PARENB
| PARODD
| CRTSCTS
;
362 tty
.c_cflag
|= CREAD
| HUPCL
| CLOCAL
;
365 tty
.c_iflag
= ICRNL
| IXON
| IXOFF
;
368 tty
.c_oflag
= OPOST
| ONLCR
;
371 tty
.c_lflag
= ISIG
| ICANON
| ECHO
| ECHOE
| ECHOK
| ECHOCTL
| ECHOKE
| IEXTEN
;
373 tcsetattr_stdin_TCSANOW(&tty
);
376 /* Open the new terminal device.
377 * NB: careful, we can be called after vfork! */
378 static int open_stdio_to_tty(const char* tty_name
)
380 /* empty tty_name means "use init's tty", else... */
385 /* fd can be only < 0 or 0: */
386 fd
= device_open(tty_name
, O_RDWR
);
388 message(L_LOG
| L_CONSOLE
, "can't open %s: %s",
389 tty_name
, strerror(errno
));
390 return 0; /* failure */
392 dup2(STDIN_FILENO
, STDOUT_FILENO
);
393 dup2(STDIN_FILENO
, STDERR_FILENO
);
396 return 1; /* success */
399 static void reset_sighandlers_and_unblock_sigs(void)
411 sigprocmask_allsigs(SIG_UNBLOCK
);
414 /* Wrapper around exec:
416 * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
417 * Otherwise splits words on whitespace, deals with leading dash,
418 * and uses plain exec().
419 * NB: careful, we can be called after vfork!
421 static void init_exec(const char *command
)
423 /* +8 allows to write VLA sizes below more efficiently: */
424 unsigned command_size
= strlen(command
) + 8;
425 /* strlen(command) + strlen("exec ")+1: */
426 char buf
[command_size
];
427 /* strlen(command) / 2 + 4: */
428 char *cmd
[command_size
/ 2];
431 dash
= (command
[0] == '-' /* maybe? && command[1] == '/' */);
434 /* See if any special /bin/sh requiring characters are present */
435 if (strpbrk(command
, "~`!$^&*()=|\\{}[];\"'<>?") != NULL
) {
436 sprintf(buf
, "exec %s", command
); /* excluding "-" */
437 /* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
438 cmd
[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL
+ !dash
);
439 cmd
[1] = (char*)"-c";
442 command
= LIBBB_DEFAULT_LOGIN_SHELL
+ 1;
444 /* Convert command (char*) into cmd (char**, one word per string) */
447 next
= strcpy(buf
, command
- dash
); /* command including "-" */
448 command
= next
+ dash
;
449 while ((word
= strsep(&next
, " \t")) != NULL
) {
450 if (*word
!= '\0') { /* not two spaces/tabs together? */
457 /* If we saw leading "-", it is interactive shell.
458 * Try harder to give it a controlling tty.
460 if (ENABLE_FEATURE_INIT_SCTTY
&& dash
) {
461 /* _Attempt_ to make stdin a controlling tty. */
462 ioctl(STDIN_FILENO
, TIOCSCTTY
, 0 /*only try, don't steal*/);
464 /* Here command never contains the dash, cmd[0] might */
465 BB_EXECVP(command
, cmd
);
466 message(L_LOG
| L_CONSOLE
, "can't run '%s': %s", command
, strerror(errno
));
467 /* returns if execvp fails */
470 /* Used only by run_actions */
471 static pid_t
run(const struct init_action
*a
)
475 /* Careful: don't be affected by a signal in vforked child */
476 sigprocmask_allsigs(SIG_BLOCK
);
477 if (BB_MMU
&& (a
->action_type
& ASKFIRST
))
482 message(L_LOG
| L_CONSOLE
, "can't fork");
484 sigprocmask_allsigs(SIG_UNBLOCK
);
485 return pid
; /* Parent or error */
490 /* Reset signal handlers that were set by the parent process */
491 reset_sighandlers_and_unblock_sigs();
493 /* Create a new session and make ourself the process group leader */
496 /* Open the new terminal device */
497 if (!open_stdio_to_tty(a
->terminal
))
500 /* NB: on NOMMU we can't wait for input in child, so
501 * "askfirst" will work the same as "respawn". */
502 if (BB_MMU
&& (a
->action_type
& ASKFIRST
)) {
503 static const char press_enter
[] ALIGN1
=
504 #ifdef CUSTOMIZED_BANNER
505 #include CUSTOMIZED_BANNER
507 "\nPlease press Enter to activate this console. ";
510 * Save memory by not exec-ing anything large (like a shell)
511 * before the user wants it. This is critical if swap is not
512 * enabled and the system has low memory. Generally this will
513 * be run on the second virtual console, and the first will
514 * be allowed to start a shell or whatever an init script
517 dbg_message(L_LOG
, "waiting for enter to start '%s'"
518 "(pid %d, tty '%s')\n",
519 a
->command
, getpid(), a
->terminal
);
520 full_write(STDOUT_FILENO
, press_enter
, sizeof(press_enter
) - 1);
521 while (safe_read(STDIN_FILENO
, &c
, 1) == 1 && c
!= '\n')
526 * When a file named /.init_enable_core exists, setrlimit is called
527 * before processes are spawned to set core file size as unlimited.
528 * This is for debugging only. Don't use this is production, unless
529 * you want core dumps lying about....
531 if (ENABLE_FEATURE_INIT_COREDUMPS
) {
532 if (access("/.init_enable_core", F_OK
) == 0) {
534 limit
.rlim_cur
= RLIM_INFINITY
;
535 limit
.rlim_max
= RLIM_INFINITY
;
536 setrlimit(RLIMIT_CORE
, &limit
);
540 /* Log the process name and args */
541 message(L_LOG
, "starting pid %d, tty '%s': '%s'",
542 getpid(), a
->terminal
, a
->command
);
544 /* Now run it. The new program will take over this PID,
545 * so nothing further in init.c should be run. */
546 init_exec(a
->command
);
547 /* We're still here? Some error happened. */
551 static struct init_action
*mark_terminated(pid_t pid
)
553 struct init_action
*a
;
556 update_utmp_DEAD_PROCESS(pid
);
557 for (a
= init_action_list
; a
; a
= a
->next
) {
567 static void waitfor(pid_t pid
)
569 /* waitfor(run(x)): protect against failed fork inside run() */
573 /* Wait for any child (prevent zombies from exiting orphaned processes)
574 * but exit the loop only when specified one has exited. */
576 pid_t wpid
= wait(NULL
);
577 mark_terminated(wpid
);
578 /* Unsafe. SIGTSTP handler might have wait'ed it already */
579 /*if (wpid == pid) break;*/
586 /* Run all commands of a particular type */
587 static void run_actions(int action_type
)
589 struct init_action
*a
;
591 for (a
= init_action_list
; a
; a
= a
->next
) {
592 if (!(a
->action_type
& action_type
))
595 if (a
->action_type
& (SYSINIT
| WAIT
| ONCE
| CTRLALTDEL
| SHUTDOWN
)) {
597 if (a
->action_type
& (SYSINIT
| WAIT
| CTRLALTDEL
| SHUTDOWN
))
600 if (a
->action_type
& (RESPAWN
| ASKFIRST
)) {
601 /* Only run stuff with pid == 0. If pid != 0,
602 * it is already running
610 static void new_init_action(uint8_t action_type
, const char *command
, const char *cons
)
612 struct init_action
*a
, **nextp
;
616 * ::shutdown:umount -a -r
617 * ::shutdown:swapoff -a
619 * ::shutdown:swapoff -a
620 * ::shutdown:umount -a -r
621 * On reload, we must ensure entries end up in correct order.
622 * To achieve that, if we find a matching entry, we move it
625 nextp
= &init_action_list
;
626 while ((a
= *nextp
) != NULL
) {
627 /* Don't enter action if it's already in the list.
628 * This prevents losing running RESPAWNs.
630 if (strcmp(a
->command
, command
) == 0
631 && strcmp(a
->terminal
, cons
) == 0
633 /* Remove from list */
635 /* Find the end of the list */
636 while (*nextp
!= NULL
)
637 nextp
= &(*nextp
)->next
;
644 a
= xzalloc(sizeof(*a
) + strlen(command
));
646 /* Append to the end of the list */
649 a
->action_type
= action_type
;
650 strcpy(a
->command
, command
);
651 safe_strncpy(a
->terminal
, cons
, sizeof(a
->terminal
));
652 dbg_message(L_LOG
| L_CONSOLE
, "command='%s' action=%x tty='%s'\n",
653 a
->command
, a
->action_type
, a
->terminal
);
656 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
657 * then parse_inittab() simply adds in some default
658 * actions (i.e., runs INIT_SCRIPT and then starts a pair
659 * of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB
660 * _is_ defined, but /etc/inittab is missing, this
661 * results in the same set of default behaviors.
663 static void parse_inittab(void)
665 #if ENABLE_FEATURE_USE_INITTAB
667 parser_t
*parser
= config_open2("/etc/inittab", fopen_for_read
);
672 /* No inittab file - set up some default behavior */
674 new_init_action(SYSINIT
, INIT_SCRIPT
, "");
675 /* Askfirst shell on tty1-4 */
676 new_init_action(ASKFIRST
, bb_default_login_shell
, "");
677 //TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
678 new_init_action(ASKFIRST
, bb_default_login_shell
, VC_2
);
679 new_init_action(ASKFIRST
, bb_default_login_shell
, VC_3
);
680 new_init_action(ASKFIRST
, bb_default_login_shell
, VC_4
);
681 /* Reboot on Ctrl-Alt-Del */
682 new_init_action(CTRLALTDEL
, "reboot", "");
683 /* Umount all filesystems on halt/reboot */
684 new_init_action(SHUTDOWN
, "umount -a -r", "");
685 /* Swapoff on halt/reboot */
686 new_init_action(SHUTDOWN
, "swapoff -a", "");
687 /* Restart init when a QUIT is received */
688 new_init_action(RESTART
, "init", "");
692 #if ENABLE_FEATURE_USE_INITTAB
693 /* optional_tty:ignored_runlevel:action:command
694 * Delims are not to be collapsed and need exactly 4 tokens
696 while (config_read(parser
, token
, 4, 0, "#:",
697 PARSE_NORMAL
& ~(PARSE_TRIM
| PARSE_COLLAPSE
))) {
698 /* order must correspond to SYSINIT..RESTART constants */
699 static const char actions
[] ALIGN1
=
700 "sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
701 "ctrlaltdel\0""shutdown\0""restart\0";
703 char *tty
= token
[0];
705 if (!token
[3]) /* less than 4 tokens */
707 action
= index_in_strings(actions
, token
[2]);
708 if (action
< 0 || !token
[3][0]) /* token[3]: command */
710 /* turn .*TTY -> /dev/TTY */
712 tty
= concat_path_file("/dev/", skip_dev_pfx(tty
));
714 new_init_action(1 << action
, token
[3], tty
);
719 message(L_LOG
| L_CONSOLE
, "Bad inittab entry at line %d",
722 config_close(parser
);
726 static void pause_and_low_level_reboot(unsigned magic
) NORETURN
;
727 static void pause_and_low_level_reboot(unsigned magic
)
731 /* Allow time for last message to reach serial console, etc */
734 /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
735 * in linux/kernel/sys.c, which can cause the machine to panic when
736 * the init process exits... */
738 if (pid
== 0) { /* child */
746 static void run_shutdown_and_kill_processes(void)
748 /* Run everything to be run at "shutdown". This is done _prior_
749 * to killing everything, in case people wish to use scripts to
750 * shut things down gracefully... */
751 run_actions(SHUTDOWN
);
753 message(L_CONSOLE
| L_LOG
, "The system is going down NOW!");
755 /* Send signals to every process _except_ pid 1 */
757 message(L_CONSOLE
| L_LOG
, "Sent SIG%s to all processes", "TERM");
762 message(L_CONSOLE
, "Sent SIG%s to all processes", "KILL");
764 /*sleep(1); - callers take care about making a pause */
767 /* Signal handling by init:
769 * For process with PID==1, on entry kernel sets all signals to SIG_DFL
770 * and unmasks all signals. However, for process with PID==1,
771 * default action (SIG_DFL) on any signal is to ignore it,
772 * even for special signals SIGKILL and SIGCONT.
773 * Also, any signal can be caught or blocked.
774 * (but SIGSTOP is still handled specially, at least in 2.6.20)
776 * We install two kinds of handlers, "immediate" and "delayed".
778 * Immediate handlers execute at any time, even while, say, sysinit
781 * Delayed handlers just set a flag variable. The variable is checked
782 * in the main loop and acted upon.
784 * halt/poweroff/reboot and restart have immediate handlers.
785 * They only traverse linked list of struct action's, never modify it,
786 * this should be safe to do even in signal handler. Also they
789 * SIGSTOP and SIGTSTP have immediate handlers. They just wait
790 * for SIGCONT to happen.
792 * SIGHUP has a delayed handler, because modifying linked list
793 * of struct action's from a signal handler while it is manipulated
794 * by the program may be disastrous.
796 * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
797 * it to happen even somewhere inside "sysinit" would be a bit awkward.
799 * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
800 * and only one will be remembered and acted upon.
803 /* The SIGPWR/SIGUSR[12]/SIGTERM handler */
804 static void halt_reboot_pwoff(int sig
) NORETURN
;
805 static void halt_reboot_pwoff(int sig
)
810 /* We may call run() and it unmasks signals,
811 * including the one masked inside this signal handler.
812 * Testcase which would start multiple reboot scripts:
813 * while true; do reboot; done
816 reset_sighandlers_and_unblock_sigs();
818 run_shutdown_and_kill_processes();
822 if (sig
== SIGTERM
) {
825 } else if (sig
== SIGUSR2
) {
829 message(L_CONSOLE
, "Requesting system %s", m
);
830 pause_and_low_level_reboot(rb
);
834 /* Handler for QUIT - exec "restart" action,
835 * else (no such action defined) do nothing */
836 static void exec_restart_action(void)
838 struct init_action
*a
;
840 for (a
= init_action_list
; a
; a
= a
->next
) {
841 if (!(a
->action_type
& RESTART
))
844 /* Starting from here, we won't return.
845 * Thus don't need to worry about preserving errno
849 reset_sighandlers_and_unblock_sigs();
851 run_shutdown_and_kill_processes();
854 /* Allow Ctrl-Alt-Del to reboot the system.
855 * This is how kernel sets it up for init, we follow suit.
857 reboot(RB_ENABLE_CAD
); /* misnomer */
860 if (open_stdio_to_tty(a
->terminal
)) {
861 dbg_message(L_CONSOLE
, "Trying to re-exec %s", a
->command
);
862 /* Theoretically should be safe.
863 * But in practice, kernel bugs may leave
864 * unkillable processes, and wait() may block forever.
865 * Oh well. Hoping "new" init won't be too surprised
866 * by having children it didn't create.
868 //while (wait(NULL) > 0)
870 init_exec(a
->command
);
872 /* Open or exec failed */
873 pause_and_low_level_reboot(RB_HALT_SYSTEM
);
878 /* The SIGSTOP/SIGTSTP handler
879 * NB: inside it, all signals except SIGCONT are masked
880 * via appropriate setup in sigaction().
882 static void stop_handler(int sig UNUSED_PARAM
)
884 smallint saved_bb_got_signal
;
887 saved_bb_got_signal
= bb_got_signal
;
889 signal(SIGCONT
, record_signo
);
894 if (bb_got_signal
== SIGCONT
)
896 /* NB: this can accidentally wait() for a process
897 * which we waitfor() elsewhere! waitfor() must have
898 * code which is resilient against this.
900 wpid
= wait_any_nohang(NULL
);
901 mark_terminated(wpid
);
905 signal(SIGCONT
, SIG_DFL
);
907 bb_got_signal
= saved_bb_got_signal
;
910 #if ENABLE_FEATURE_USE_INITTAB
911 static void reload_inittab(void)
913 struct init_action
*a
, **nextp
;
915 message(L_LOG
, "reloading /etc/inittab");
917 /* Disable old entries */
918 for (a
= init_action_list
; a
; a
= a
->next
)
921 /* Append new entries, or modify existing entries
922 * (incl. setting a->action_type) if cmd and device name
923 * match new ones. End result: only entries with
924 * a->action_type == 0 are stale.
928 #if ENABLE_FEATURE_KILL_REMOVED
929 /* Kill stale entries */
930 /* Be nice and send SIGTERM first */
931 for (a
= init_action_list
; a
; a
= a
->next
)
932 if (a
->action_type
== 0 && a
->pid
!= 0)
933 kill(a
->pid
, SIGTERM
);
934 if (CONFIG_FEATURE_KILL_DELAY
) {
935 /* NB: parent will wait in NOMMU case */
936 if ((BB_MMU
? fork() : vfork()) == 0) { /* child */
937 sleep(CONFIG_FEATURE_KILL_DELAY
);
938 for (a
= init_action_list
; a
; a
= a
->next
)
939 if (a
->action_type
== 0 && a
->pid
!= 0)
940 kill(a
->pid
, SIGKILL
);
946 /* Remove stale entries and SYSINIT entries.
947 * We never rerun SYSINIT entries anyway,
948 * removing them too saves a few bytes
950 nextp
= &init_action_list
;
951 while ((a
= *nextp
) != NULL
) {
953 * Why pid == 0 check?
954 * Process can be removed from inittab and added *later*.
955 * If we delete its entry but process still runs,
956 * duplicate is spawned when the entry is re-added.
958 if ((a
->action_type
& ~SYSINIT
) == 0 && a
->pid
== 0) {
967 /* run_actions(RESPAWN | ASKFIRST); */
968 /* - we return to main loop, which does this automagically */
972 static int check_delayed_sigs(void)
977 smallint sig
= bb_got_signal
;
983 #if ENABLE_FEATURE_USE_INITTAB
988 run_actions(CTRLALTDEL
);
989 if (sig
== SIGQUIT
) {
990 exec_restart_action();
991 /* returns only if no restart action defined */
1001 halt_reboot_pwoff(sig
);
1006 #if DEBUG_SEGV_HANDLER
1008 void handle_sigsegv(int sig
, siginfo_t
*info
, void *ucontext
)
1014 ip
= uc
->uc_mcontext
.gregs
[REG_EIP
];
1015 fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n",
1017 /* this is void*, but using %p would print "(null)"
1018 * even for ptrs which are not exactly 0, but, say, 0x123:
1020 (long)info
->si_addr
,
1023 /* glibc extension */
1026 size
= backtrace(array
, 50);
1027 backtrace_symbols_fd(array
, size
, 2);
1029 for (;;) sleep(9999);
1033 static void sleep_much(void)
1035 sleep(30 * 24*60*60);
1038 int init_main(int argc
, char **argv
) MAIN_EXTERNALLY_VISIBLE
;
1039 int init_main(int argc UNUSED_PARAM
, char **argv
)
1041 if (argv
[1] && strcmp(argv
[1], "-q") == 0) {
1042 return kill(1, SIGHUP
);
1045 #if DEBUG_SEGV_HANDLER
1047 struct sigaction sa
;
1048 memset(&sa
, 0, sizeof(sa
));
1049 sa
.sa_sigaction
= handle_sigsegv
;
1050 sa
.sa_flags
= SA_SIGINFO
;
1051 sigaction(SIGSEGV
, &sa
, NULL
);
1052 sigaction(SIGILL
, &sa
, NULL
);
1053 sigaction(SIGFPE
, &sa
, NULL
);
1054 sigaction(SIGBUS
, &sa
, NULL
);
1059 /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
1061 && (!ENABLE_LINUXRC
|| applet_name
[0] != 'l') /* not linuxrc? */
1063 bb_error_msg_and_die("must be run as PID 1");
1065 #ifdef RB_DISABLE_CAD
1066 /* Turn off rebooting via CTL-ALT-DEL - we get a
1067 * SIGINT on CAD so we can shut things down gracefully... */
1068 reboot(RB_DISABLE_CAD
); /* misnomer */
1072 /* If, say, xmalloc would ever die, we don't want to oops kernel
1074 * NB: we set die_func *after* PID 1 check and bb_show_usage.
1075 * Otherwise, for example, "init u" ("please rexec yourself"
1076 * command for sysvinit) will show help text (which isn't too bad),
1077 * *and sleep forever* (which is bad!)
1079 die_func
= sleep_much
;
1081 /* Figure out where the default console should be */
1087 /* Make sure environs is set to something sane */
1088 putenv((char *) "HOME=/");
1089 putenv((char *) bb_PATH_root_path
);
1090 putenv((char *) "SHELL=/bin/sh");
1091 putenv((char *) "USER=root"); /* needed? why? */
1094 xsetenv("RUNLEVEL", argv
[1]);
1096 #if !ENABLE_FEATURE_EXTRA_QUIET
1098 message(L_CONSOLE
| L_LOG
, "init started: %s", bb_banner
);
1102 /* It's 2013, does anyone really still depend on this? */
1103 /* If you do, consider adding swapon to sysinit actions then! */
1104 /* struct sysinfo is linux-specific */
1106 /* Make sure there is enough memory to do something useful. */
1107 /*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ {
1108 struct sysinfo info
;
1110 if (sysinfo(&info
) == 0
1111 && (info
.mem_unit
? info
.mem_unit
: 1) * (long long)info
.totalram
< 1024*1024
1113 message(L_CONSOLE
, "Low memory, forcing swapon");
1114 /* swapon -a requires /proc typically */
1115 new_init_action(SYSINIT
, "mount -t proc proc /proc", "");
1116 /* Try to turn on swap */
1117 new_init_action(SYSINIT
, "swapon -a", "");
1118 run_actions(SYSINIT
); /* wait and removing */
1124 /* Check if we are supposed to be in single user mode */
1126 && (strcmp(argv
[1], "single") == 0 || strcmp(argv
[1], "-s") == 0 || LONE_CHAR(argv
[1], '1'))
1128 /* ??? shouldn't we set RUNLEVEL="b" here? */
1129 /* Start a shell on console */
1130 new_init_action(RESPAWN
, bb_default_login_shell
, "");
1132 /* Not in single user mode - see what inittab says */
1134 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
1135 * then parse_inittab() simply adds in some default
1136 * actions (i.e., INIT_SCRIPT and a pair
1137 * of "askfirst" shells) */
1142 if (getenv("SELINUX_INIT") == NULL
) {
1145 putenv((char*)"SELINUX_INIT=YES");
1146 if (selinux_init_load_policy(&enforce
) == 0) {
1147 BB_EXECVP(argv
[0], argv
);
1148 } else if (enforce
> 0) {
1149 /* SELinux in enforcing mode but load_policy failed */
1150 message(L_CONSOLE
, "can't load SELinux Policy. "
1151 "Machine is in enforcing mode. Halting now.");
1152 return EXIT_FAILURE
;
1157 if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE
) {
1158 /* Make the command line just say "init" - that's all, nothing else */
1159 strncpy(argv
[0], "init", strlen(argv
[0]));
1160 /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
1165 /* Set up signal handlers */
1167 struct sigaction sa
;
1169 /* Stop handler must allow only SIGCONT inside itself */
1170 memset(&sa
, 0, sizeof(sa
));
1171 sigfillset(&sa
.sa_mask
);
1172 sigdelset(&sa
.sa_mask
, SIGCONT
);
1173 sa
.sa_handler
= stop_handler
;
1174 /* NB: sa_flags doesn't have SA_RESTART.
1175 * It must be able to interrupt wait().
1177 sigaction_set(SIGTSTP
, &sa
); /* pause */
1178 /* Does not work as intended, at least in 2.6.20.
1179 * SIGSTOP is simply ignored by init:
1181 sigaction_set(SIGSTOP
, &sa
); /* pause */
1183 /* These signals must interrupt wait(),
1184 * setting handler without SA_RESTART flag.
1186 bb_signals_recursive_norestart(0
1187 + (1 << SIGINT
) /* Ctrl-Alt-Del */
1188 + (1 << SIGQUIT
) /* re-exec another init */
1190 + (1 << SIGPWR
) /* halt */
1192 + (1 << SIGUSR1
) /* halt */
1193 + (1 << SIGTERM
) /* reboot */
1194 + (1 << SIGUSR2
) /* poweroff */
1195 #if ENABLE_FEATURE_USE_INITTAB
1196 + (1 << SIGHUP
) /* reread /etc/inittab */
1201 /* Now run everything that needs to be run */
1202 /* First run the sysinit command */
1203 run_actions(SYSINIT
);
1204 check_delayed_sigs();
1205 /* Next run anything that wants to block */
1207 check_delayed_sigs();
1208 /* Next run anything to be run only once */
1211 /* Now run the looping stuff for the rest of forever.
1216 maybe_WNOHANG
= check_delayed_sigs();
1218 /* (Re)run the respawn/askfirst stuff */
1219 run_actions(RESPAWN
| ASKFIRST
);
1220 maybe_WNOHANG
|= check_delayed_sigs();
1222 /* Don't consume all CPU time - sleep a bit */
1224 maybe_WNOHANG
|= check_delayed_sigs();
1226 /* Wait for any child process(es) to exit.
1228 * If check_delayed_sigs above reported that a signal
1229 * was caught, wait will be nonblocking. This ensures
1230 * that if SIGHUP has reloaded inittab, respawn and askfirst
1231 * actions will not be delayed until next child death.
1234 maybe_WNOHANG
= WNOHANG
;
1237 struct init_action
*a
;
1239 /* If signals happen _in_ the wait, they interrupt it,
1240 * bb_signals_recursive_norestart set them up that way
1242 wpid
= waitpid(-1, NULL
, maybe_WNOHANG
);
1246 a
= mark_terminated(wpid
);
1248 message(L_LOG
, "process '%s' (pid %d) exited. "
1249 "Scheduling for restart.",
1252 /* See if anyone else is waiting to be reaped */
1253 maybe_WNOHANG
= WNOHANG
;
1258 //usage:#define linuxrc_trivial_usage NOUSAGE_STR
1259 //usage:#define linuxrc_full_usage ""
1261 //usage:#define init_trivial_usage
1263 //usage:#define init_full_usage "\n\n"
1264 //usage: "Init is the first process started during boot. It never exits."
1265 //usage: IF_FEATURE_USE_INITTAB(
1266 //usage: "\n""It (re)spawns children according to /etc/inittab."
1268 //usage: IF_NOT_FEATURE_USE_INITTAB(
1269 //usage: "\n""This version of init doesn't use /etc/inittab,"
1270 //usage: "\n""has fixed set of processed to run."
1273 //usage:#define init_notes_usage
1274 //usage: "This version of init is designed to be run only by the kernel.\n"
1276 //usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
1277 //usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
1278 //usage: "runlevels, use sysvinit.\n"
1280 //usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n"
1281 //usage: "it has the following default behavior:\n"
1283 //usage: " ::sysinit:/etc/init.d/rcS\n"
1284 //usage: " ::askfirst:/bin/sh\n"
1285 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1286 //usage: " ::shutdown:/sbin/swapoff -a\n"
1287 //usage: " ::shutdown:/bin/umount -a -r\n"
1288 //usage: " ::restart:/sbin/init\n"
1289 //usage: " tty2::askfirst:/bin/sh\n"
1290 //usage: " tty3::askfirst:/bin/sh\n"
1291 //usage: " tty4::askfirst:/bin/sh\n"
1293 //usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
1295 //usage: " <id>:<runlevels>:<action>:<process>\n"
1299 //usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n"
1300 //usage: " The id field is used by BusyBox init to specify the controlling tty for\n"
1301 //usage: " the specified process to run on. The contents of this field are\n"
1302 //usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n"
1303 //usage: " be unique, although if it isn't you may have strange results. If this\n"
1304 //usage: " field is left blank, then the init's stdin/out will be used.\n"
1306 //usage: " <runlevels>:\n"
1308 //usage: " The runlevels field is completely ignored.\n"
1310 //usage: " <action>:\n"
1312 //usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n"
1313 //usage: " once, restart, ctrlaltdel, and shutdown.\n"
1315 //usage: " The available actions can be classified into two groups: actions\n"
1316 //usage: " that are run only once, and actions that are re-run when the specified\n"
1317 //usage: " process exits.\n"
1319 //usage: " Run only-once actions:\n"
1321 //usage: " 'sysinit' is the first item run on boot. init waits until all\n"
1322 //usage: " sysinit actions are completed before continuing. Following the\n"
1323 //usage: " completion of all sysinit actions, all 'wait' actions are run.\n"
1324 //usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n"
1325 //usage: " the specified task completes. 'once' actions are asynchronous,\n"
1326 //usage: " therefore, init does not wait for them to complete. 'restart' is\n"
1327 //usage: " the action taken to restart the init process. By default this should\n"
1328 //usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n"
1329 //usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
1330 //usage: " actions are run when the system detects that someone on the system\n"
1331 //usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
1332 //usage: " wants to run 'reboot' at this point to cause the system to reboot.\n"
1333 //usage: " Finally the 'shutdown' action specifies the actions to taken when\n"
1334 //usage: " init is told to reboot. Unmounting filesystems and disabling swap\n"
1335 //usage: " is a very good here.\n"
1337 //usage: " Run repeatedly actions:\n"
1339 //usage: " 'respawn' actions are run after the 'once' actions. When a process\n"
1340 //usage: " started with a 'respawn' action exits, init automatically restarts\n"
1341 //usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n"
1342 //usage: " respawning out of control. The 'askfirst' actions acts just like\n"
1343 //usage: " respawn, except that before running the specified process it\n"
1344 //usage: " displays the line \"Please press Enter to activate this console.\"\n"
1345 //usage: " and then waits for the user to press enter before starting the\n"
1346 //usage: " specified process.\n"
1348 //usage: " Unrecognized actions (like initdefault) will cause init to emit an\n"
1349 //usage: " error message, and then go along with its business. All actions are\n"
1350 //usage: " run in the order they appear in /etc/inittab.\n"
1352 //usage: " <process>:\n"
1354 //usage: " Specifies the process to be executed and its command line.\n"
1356 //usage: "Example /etc/inittab file:\n"
1358 //usage: " # This is run first except when booting in single-user mode\n"
1360 //usage: " ::sysinit:/etc/init.d/rcS\n"
1362 //usage: " # /bin/sh invocations on selected ttys\n"
1364 //usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n"
1365 //usage: " ::askfirst:-/bin/sh\n"
1366 //usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n"
1367 //usage: " tty2::askfirst:-/bin/sh\n"
1368 //usage: " tty3::askfirst:-/bin/sh\n"
1369 //usage: " tty4::askfirst:-/bin/sh\n"
1371 //usage: " # /sbin/getty invocations for selected ttys\n"
1373 //usage: " tty4::respawn:/sbin/getty 38400 tty4\n"
1374 //usage: " tty5::respawn:/sbin/getty 38400 tty5\n"
1377 //usage: " # Example of how to put a getty on a serial line (for a terminal)\n"
1379 //usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
1380 //usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
1382 //usage: " # Example how to put a getty on a modem line\n"
1383 //usage: " #::respawn:/sbin/getty 57600 ttyS2\n"
1385 //usage: " # Stuff to do when restarting the init process\n"
1386 //usage: " ::restart:/sbin/init\n"
1388 //usage: " # Stuff to do before rebooting\n"
1389 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1390 //usage: " ::shutdown:/bin/umount -a -r\n"
1391 //usage: " ::shutdown:/sbin/swapoff -a\n"