hush/init/init.c
Denys Vlasenko 67905e2d7c *: work around sysinfo.h versus linux/*.h problems
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2011-07-26 13:42:12 +02:00

1293 lines
39 KiB
C

/* vi: set sw=4 ts=4: */
/*
* Mini init implementation for busybox
*
* Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
* Adjusted by so many folks, it's impossible to keep track.
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
//applet:IF_FEATURE_INITRD(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
//kbuild:lib-$(CONFIG_INIT) += init.o
//config:config INIT
//config: bool "init"
//config: default y
//config: select FEATURE_SYSLOG
//config: help
//config: init is the first program run when the system boots.
//config:
//config:config FEATURE_USE_INITTAB
//config: bool "Support reading an inittab file"
//config: default y
//config: depends on INIT
//config: help
//config: Allow init to read an inittab file when the system boot.
//config:
//config:config FEATURE_KILL_REMOVED
//config: bool "Support killing processes that have been removed from inittab"
//config: default n
//config: depends on FEATURE_USE_INITTAB
//config: help
//config: When respawn entries are removed from inittab and a SIGHUP is
//config: sent to init, this option will make init kill the processes
//config: that have been removed.
//config:
//config:config FEATURE_KILL_DELAY
//config: int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED
//config: range 0 1024
//config: default 0
//config: depends on FEATURE_KILL_REMOVED
//config: help
//config: With nonzero setting, init sends TERM, forks, child waits N
//config: seconds, sends KILL and exits. Setting it too high is unwise
//config: (child will hang around for too long and could actually kill
//config: the wrong process!)
//config:
//config:config FEATURE_INIT_SCTTY
//config: bool "Run commands with leading dash with controlling tty"
//config: default y
//config: depends on INIT
//config: help
//config: If this option is enabled, init will try to give a controlling
//config: tty to any command which has leading hyphen (often it's "-/bin/sh").
//config: More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)".
//config: If device attached to STDIN_FILENO can be a ctty but is not yet
//config: a ctty for other session, it will become this process' ctty.
//config: This is not the traditional init behavour, but is often what you want
//config: in an embedded system where the console is only accessed during
//config: development or for maintenance.
//config: NB: using cttyhack applet may work better.
//config:
//config:config FEATURE_INIT_SYSLOG
//config: bool "Enable init to write to syslog"
//config: default y
//config: depends on INIT
//config:
//config:config FEATURE_EXTRA_QUIET
//config: bool "Be _extra_ quiet on boot"
//config: default y
//config: depends on INIT
//config: help
//config: Prevent init from logging some messages to the console during boot.
//config:
//config:config FEATURE_INIT_COREDUMPS
//config: bool "Support dumping core for child processes (debugging only)"
//config: default y
//config: depends on INIT
//config: help
//config: If this option is enabled and the file /.init_enable_core
//config: exists, then init will call setrlimit() to allow unlimited
//config: core file sizes. If this option is disabled, processes
//config: will not generate any core files.
//config:
//config:config FEATURE_INITRD
//config: bool "Support running init from within an initrd (not initramfs)"
//config: default y
//config: depends on INIT
//config: help
//config: Legacy support for running init under the old-style initrd. Allows
//config: the name linuxrc to act as init, and it doesn't assume init is PID 1.
//config:
//config: This does not apply to initramfs, which runs /init as PID 1 and
//config: requires no special support.
//config:
//config:config INIT_TERMINAL_TYPE
//config: string "Initial terminal type"
//config: default "linux"
//config: depends on INIT
//config: help
//config: This is the initial value set by init for the TERM environment
//config: variable. This variable is used by programs which make use of
//config: extended terminal capabilities.
//config:
//config: Note that on Linux, init attempts to detect serial terminal and
//config: sets TERM to "vt102" if one is found.
#include "libbb.h"
#include <syslog.h>
#include <paths.h>
#include <sys/resource.h>
#ifdef __linux__
# include <linux/vt.h>
# include <sys/sysinfo.h>
#endif
#include "reboot.h" /* reboot() constants */
/* Used only for sanitizing purposes in set_sane_term() below. On systems where
* the baud rate is stored in a separate field, we can safely disable them. */
#ifndef CBAUD
# define CBAUD 0
# define CBAUDEX 0
#endif
/* Was a CONFIG_xxx option. A lot of people were building
* not fully functional init by switching it on! */
#define DEBUG_INIT 0
#define COMMAND_SIZE 256
#define CONSOLE_NAME_SIZE 32
/* Default sysinit script. */
#ifndef INIT_SCRIPT
#define INIT_SCRIPT "/etc/init.d/rcS"
#endif
/* Each type of actions can appear many times. They will be
* handled in order. RESTART is an exception, only 1st is used.
*/
/* Start these actions first and wait for completion */
#define SYSINIT 0x01
/* Start these after SYSINIT and wait for completion */
#define WAIT 0x02
/* Start these after WAIT and *dont* wait for completion */
#define ONCE 0x04
/*
* NB: while SYSINIT/WAIT/ONCE are being processed,
* SIGHUP ("reread /etc/inittab") will be processed only after
* each group of actions. If new inittab adds, say, a SYSINIT action,
* it will not be run, since init is already "past SYSINIT stage".
*/
/* Start these after ONCE are started, restart on exit */
#define RESPAWN 0x08
/* Like RESPAWN, but wait for <Enter> to be pressed on tty */
#define ASKFIRST 0x10
/*
* Start these on SIGINT, and wait for completion.
* Then go back to respawning RESPAWN and ASKFIRST actions.
* NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
*/
#define CTRLALTDEL 0x20
/*
* Start these before killing all processes in preparation for
* running RESTART actions or doing low-level halt/reboot/poweroff
* (initiated by SIGUSR1/SIGTERM/SIGUSR2).
* Wait for completion before proceeding.
*/
#define SHUTDOWN 0x40
/*
* exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
* then all processes are killed, then init exec's 1st RESTART action,
* replacing itself by it. If no RESTART action specified,
* SIGQUIT has no effect.
*/
#define RESTART 0x80
/* A linked list of init_actions, to be read from inittab */
struct init_action {
struct init_action *next;
pid_t pid;
uint8_t action_type;
char terminal[CONSOLE_NAME_SIZE];
char command[COMMAND_SIZE];
};
static struct init_action *init_action_list = NULL;
static const char *log_console = VC_5;
enum {
L_LOG = 0x1,
L_CONSOLE = 0x2,
};
/* Print a message to the specified device.
* "where" may be bitwise-or'd from L_LOG | L_CONSOLE
* NB: careful, we can be called after vfork!
*/
#define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
static void message(int where, const char *fmt, ...)
__attribute__ ((format(printf, 2, 3)));
static void message(int where, const char *fmt, ...)
{
va_list arguments;
unsigned l;
char msg[128];
msg[0] = '\r';
va_start(arguments, fmt);
l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments);
if (l > sizeof(msg) - 1)
l = sizeof(msg) - 1;
va_end(arguments);
#if ENABLE_FEATURE_INIT_SYSLOG
msg[l] = '\0';
if (where & L_LOG) {
/* Log the message to syslogd */
openlog(applet_name, 0, LOG_DAEMON);
/* don't print "\r" */
syslog(LOG_INFO, "%s", msg + 1);
closelog();
}
msg[l++] = '\n';
msg[l] = '\0';
#else
{
static int log_fd = -1;
msg[l++] = '\n';
msg[l] = '\0';
/* Take full control of the log tty, and never close it.
* It's mine, all mine! Muhahahaha! */
if (log_fd < 0) {
if (!log_console) {
log_fd = STDERR_FILENO;
} else {
log_fd = device_open(log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY);
if (log_fd < 0) {
bb_error_msg("can't log to %s", log_console);
where = L_CONSOLE;
} else {
close_on_exec_on(log_fd);
}
}
}
if (where & L_LOG) {
full_write(log_fd, msg, l);
if (log_fd == STDERR_FILENO)
return; /* don't print dup messages */
}
}
#endif
if (where & L_CONSOLE) {
/* Send console messages to console so people will see them. */
full_write(STDERR_FILENO, msg, l);
}
}
static void console_init(void)
{
#ifdef VT_OPENQRY
int vtno;
#endif
char *s;
s = getenv("CONSOLE");
if (!s)
s = getenv("console");
if (s) {
int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY);
if (fd >= 0) {
dup2(fd, STDIN_FILENO);
dup2(fd, STDOUT_FILENO);
xmove_fd(fd, STDERR_FILENO);
}
dbg_message(L_LOG, "console='%s'", s);
} else {
/* Make sure fd 0,1,2 are not closed
* (so that they won't be used by future opens) */
bb_sanitize_stdio();
// Users report problems
// /* Make sure init can't be blocked by writing to stderr */
// fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK);
}
s = getenv("TERM");
#ifdef VT_OPENQRY
if (ioctl(STDIN_FILENO, VT_OPENQRY, &vtno) != 0) {
/* Not a linux terminal, probably serial console.
* Force the TERM setting to vt102
* if TERM is set to linux (the default) */
if (!s || strcmp(s, "linux") == 0)
putenv((char*)"TERM=vt102");
if (!ENABLE_FEATURE_INIT_SYSLOG)
log_console = NULL;
} else
#endif
if (!s)
putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE);
}
/* Set terminal settings to reasonable defaults.
* NB: careful, we can be called after vfork! */
static void set_sane_term(void)
{
struct termios tty;
tcgetattr(STDIN_FILENO, &tty);
/* set control chars */
tty.c_cc[VINTR] = 3; /* C-c */
tty.c_cc[VQUIT] = 28; /* C-\ */
tty.c_cc[VERASE] = 127; /* C-? */
tty.c_cc[VKILL] = 21; /* C-u */
tty.c_cc[VEOF] = 4; /* C-d */
tty.c_cc[VSTART] = 17; /* C-q */
tty.c_cc[VSTOP] = 19; /* C-s */
tty.c_cc[VSUSP] = 26; /* C-z */
#ifdef __linux__
/* use line discipline 0 */
tty.c_line = 0;
#endif
/* Make it be sane */
#ifndef CRTSCTS
# define CRTSCTS 0
#endif
/* added CRTSCTS to fix Debian bug 528560 */
tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS;
tty.c_cflag |= CREAD | HUPCL | CLOCAL;
/* input modes */
tty.c_iflag = ICRNL | IXON | IXOFF;
/* output modes */
tty.c_oflag = OPOST | ONLCR;
/* local modes */
tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN;
tcsetattr_stdin_TCSANOW(&tty);
}
/* Open the new terminal device.
* NB: careful, we can be called after vfork! */
static int open_stdio_to_tty(const char* tty_name)
{
/* empty tty_name means "use init's tty", else... */
if (tty_name[0]) {
int fd;
close(STDIN_FILENO);
/* fd can be only < 0 or 0: */
fd = device_open(tty_name, O_RDWR);
if (fd) {
message(L_LOG | L_CONSOLE, "can't open %s: %s",
tty_name, strerror(errno));
return 0; /* failure */
}
dup2(STDIN_FILENO, STDOUT_FILENO);
dup2(STDIN_FILENO, STDERR_FILENO);
}
set_sane_term();
return 1; /* success */
}
static void reset_sighandlers_and_unblock_sigs(void)
{
bb_signals(0
+ (1 << SIGUSR1)
+ (1 << SIGUSR2)
+ (1 << SIGTERM)
+ (1 << SIGQUIT)
+ (1 << SIGINT)
+ (1 << SIGHUP)
+ (1 << SIGTSTP)
+ (1 << SIGSTOP)
, SIG_DFL);
sigprocmask_allsigs(SIG_UNBLOCK);
}
/* Wrapper around exec:
* Takes string (max COMMAND_SIZE chars).
* If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
* Otherwise splits words on whitespace, deals with leading dash,
* and uses plain exec().
* NB: careful, we can be called after vfork!
*/
static void init_exec(const char *command)
{
char *cmd[COMMAND_SIZE / 2];
char buf[COMMAND_SIZE + 6]; /* COMMAND_SIZE+strlen("exec ")+1 */
int dash = (command[0] == '-' /* maybe? && command[1] == '/' */);
command += dash;
/* See if any special /bin/sh requiring characters are present */
if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
sprintf(buf, "exec %s", command); /* excluding "-" */
/* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash);
cmd[1] = (char*)"-c";
cmd[2] = buf;
cmd[3] = NULL;
command = LIBBB_DEFAULT_LOGIN_SHELL + 1;
} else {
/* Convert command (char*) into cmd (char**, one word per string) */
char *word, *next;
int i = 0;
next = strcpy(buf, command - dash); /* command including "-" */
command = next + dash;
while ((word = strsep(&next, " \t")) != NULL) {
if (*word != '\0') { /* not two spaces/tabs together? */
cmd[i] = word;
i++;
}
}
cmd[i] = NULL;
}
/* If we saw leading "-", it is interactive shell.
* Try harder to give it a controlling tty.
*/
if (ENABLE_FEATURE_INIT_SCTTY && dash) {
/* _Attempt_ to make stdin a controlling tty. */
ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/);
}
/* Here command never contains the dash, cmd[0] might */
BB_EXECVP(command, cmd);
message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno));
/* returns if execvp fails */
}
/* Used only by run_actions */
static pid_t run(const struct init_action *a)
{
pid_t pid;
/* Careful: don't be affected by a signal in vforked child */
sigprocmask_allsigs(SIG_BLOCK);
if (BB_MMU && (a->action_type & ASKFIRST))
pid = fork();
else
pid = vfork();
if (pid < 0)
message(L_LOG | L_CONSOLE, "can't fork");
if (pid) {
sigprocmask_allsigs(SIG_UNBLOCK);
return pid; /* Parent or error */
}
/* Child */
/* Reset signal handlers that were set by the parent process */
reset_sighandlers_and_unblock_sigs();
/* Create a new session and make ourself the process group leader */
setsid();
/* Open the new terminal device */
if (!open_stdio_to_tty(a->terminal))
_exit(EXIT_FAILURE);
/* NB: on NOMMU we can't wait for input in child, so
* "askfirst" will work the same as "respawn". */
if (BB_MMU && (a->action_type & ASKFIRST)) {
static const char press_enter[] ALIGN1 =
#ifdef CUSTOMIZED_BANNER
#include CUSTOMIZED_BANNER
#endif
"\nPlease press Enter to activate this console. ";
char c;
/*
* Save memory by not exec-ing anything large (like a shell)
* before the user wants it. This is critical if swap is not
* enabled and the system has low memory. Generally this will
* be run on the second virtual console, and the first will
* be allowed to start a shell or whatever an init script
* specifies.
*/
dbg_message(L_LOG, "waiting for enter to start '%s'"
"(pid %d, tty '%s')\n",
a->command, getpid(), a->terminal);
full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1);
while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n')
continue;
}
/*
* When a file named /.init_enable_core exists, setrlimit is called
* before processes are spawned to set core file size as unlimited.
* This is for debugging only. Don't use this is production, unless
* you want core dumps lying about....
*/
if (ENABLE_FEATURE_INIT_COREDUMPS) {
if (access("/.init_enable_core", F_OK) == 0) {
struct rlimit limit;
limit.rlim_cur = RLIM_INFINITY;
limit.rlim_max = RLIM_INFINITY;
setrlimit(RLIMIT_CORE, &limit);
}
}
/* Log the process name and args */
message(L_LOG, "starting pid %d, tty '%s': '%s'",
getpid(), a->terminal, a->command);
/* Now run it. The new program will take over this PID,
* so nothing further in init.c should be run. */
init_exec(a->command);
/* We're still here? Some error happened. */
_exit(-1);
}
static struct init_action *mark_terminated(pid_t pid)
{
struct init_action *a;
if (pid > 0) {
for (a = init_action_list; a; a = a->next) {
if (a->pid == pid) {
a->pid = 0;
return a;
}
}
update_utmp(pid, DEAD_PROCESS, /*tty_name:*/ NULL,
/*username:*/ NULL,
/*hostname:*/ NULL);
}
return NULL;
}
static void waitfor(pid_t pid)
{
/* waitfor(run(x)): protect against failed fork inside run() */
if (pid <= 0)
return;
/* Wait for any child (prevent zombies from exiting orphaned processes)
* but exit the loop only when specified one has exited. */
while (1) {
pid_t wpid = wait(NULL);
mark_terminated(wpid);
/* Unsafe. SIGTSTP handler might have wait'ed it already */
/*if (wpid == pid) break;*/
/* More reliable: */
if (kill(pid, 0))
break;
}
}
/* Run all commands of a particular type */
static void run_actions(int action_type)
{
struct init_action *a;
for (a = init_action_list; a; a = a->next) {
if (!(a->action_type & action_type))
continue;
if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
pid_t pid = run(a);
if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
waitfor(pid);
}
if (a->action_type & (RESPAWN | ASKFIRST)) {
/* Only run stuff with pid == 0. If pid != 0,
* it is already running
*/
if (a->pid == 0)
a->pid = run(a);
}
}
}
static void new_init_action(uint8_t action_type, const char *command, const char *cons)
{
struct init_action *a, **nextp;
/* Scenario:
* old inittab:
* ::shutdown:umount -a -r
* ::shutdown:swapoff -a
* new inittab:
* ::shutdown:swapoff -a
* ::shutdown:umount -a -r
* On reload, we must ensure entries end up in correct order.
* To achieve that, if we find a matching entry, we move it
* to the end.
*/
nextp = &init_action_list;
while ((a = *nextp) != NULL) {
/* Don't enter action if it's already in the list,
* This prevents losing running RESPAWNs.
*/
if (strcmp(a->command, command) == 0
&& strcmp(a->terminal, cons) == 0
) {
/* Remove from list */
*nextp = a->next;
/* Find the end of the list */
while (*nextp != NULL)
nextp = &(*nextp)->next;
a->next = NULL;
break;
}
nextp = &a->next;
}
if (!a)
a = xzalloc(sizeof(*a));
/* Append to the end of the list */
*nextp = a;
a->action_type = action_type;
safe_strncpy(a->command, command, sizeof(a->command));
safe_strncpy(a->terminal, cons, sizeof(a->terminal));
dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%d tty='%s'\n",
a->command, a->action_type, a->terminal);
}
/* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
* then parse_inittab() simply adds in some default
* actions(i.e., runs INIT_SCRIPT and then starts a pair
* of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB
* _is_ defined, but /etc/inittab is missing, this
* results in the same set of default behaviors.
*/
static void parse_inittab(void)
{
#if ENABLE_FEATURE_USE_INITTAB
char *token[4];
parser_t *parser = config_open2("/etc/inittab", fopen_for_read);
if (parser == NULL)
#endif
{
/* No inittab file - set up some default behavior */
/* Reboot on Ctrl-Alt-Del */
new_init_action(CTRLALTDEL, "reboot", "");
/* Umount all filesystems on halt/reboot */
new_init_action(SHUTDOWN, "umount -a -r", "");
/* Swapoff on halt/reboot */
if (ENABLE_SWAPONOFF)
new_init_action(SHUTDOWN, "swapoff -a", "");
/* Prepare to restart init when a QUIT is received */
new_init_action(RESTART, "init", "");
/* Askfirst shell on tty1-4 */
new_init_action(ASKFIRST, bb_default_login_shell, "");
//TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
new_init_action(ASKFIRST, bb_default_login_shell, VC_2);
new_init_action(ASKFIRST, bb_default_login_shell, VC_3);
new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
/* sysinit */
new_init_action(SYSINIT, INIT_SCRIPT, "");
return;
}
#if ENABLE_FEATURE_USE_INITTAB
/* optional_tty:ignored_runlevel:action:command
* Delims are not to be collapsed and need exactly 4 tokens
*/
while (config_read(parser, token, 4, 0, "#:",
PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
/* order must correspond to SYSINIT..RESTART constants */
static const char actions[] ALIGN1 =
"sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
"ctrlaltdel\0""shutdown\0""restart\0";
int action;
char *tty = token[0];
if (!token[3]) /* less than 4 tokens */
goto bad_entry;
action = index_in_strings(actions, token[2]);
if (action < 0 || !token[3][0]) /* token[3]: command */
goto bad_entry;
/* turn .*TTY -> /dev/TTY */
if (tty[0]) {
tty = concat_path_file("/dev/", skip_dev_pfx(tty));
}
new_init_action(1 << action, token[3], tty);
if (tty[0])
free(tty);
continue;
bad_entry:
message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d",
parser->lineno);
}
config_close(parser);
#endif
}
static void pause_and_low_level_reboot(unsigned magic) NORETURN;
static void pause_and_low_level_reboot(unsigned magic)
{
pid_t pid;
/* Allow time for last message to reach serial console, etc */
sleep(1);
/* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
* in linux/kernel/sys.c, which can cause the machine to panic when
* the init process exits... */
pid = vfork();
if (pid == 0) { /* child */
reboot(magic);
_exit(EXIT_SUCCESS);
}
while (1)
sleep(1);
}
static void run_shutdown_and_kill_processes(void)
{
/* Run everything to be run at "shutdown". This is done _prior_
* to killing everything, in case people wish to use scripts to
* shut things down gracefully... */
run_actions(SHUTDOWN);
message(L_CONSOLE | L_LOG, "The system is going down NOW!");
/* Send signals to every process _except_ pid 1 */
kill(-1, SIGTERM);
message(L_CONSOLE | L_LOG, "Sent SIG%s to all processes", "TERM");
sync();
sleep(1);
kill(-1, SIGKILL);
message(L_CONSOLE, "Sent SIG%s to all processes", "KILL");
sync();
/*sleep(1); - callers take care about making a pause */
}
/* Signal handling by init:
*
* For process with PID==1, on entry kernel sets all signals to SIG_DFL
* and unmasks all signals. However, for process with PID==1,
* default action (SIG_DFL) on any signal is to ignore it,
* even for special signals SIGKILL and SIGCONT.
* Also, any signal can be caught or blocked.
* (but SIGSTOP is still handled specially, at least in 2.6.20)
*
* We install two kinds of handlers, "immediate" and "delayed".
*
* Immediate handlers execute at any time, even while, say, sysinit
* is running.
*
* Delayed handlers just set a flag variable. The variable is checked
* in the main loop and acted upon.
*
* halt/poweroff/reboot and restart have immediate handlers.
* They only traverse linked list of struct action's, never modify it,
* this should be safe to do even in signal handler. Also they
* never return.
*
* SIGSTOP and SIGTSTP have immediate handlers. They just wait
* for SIGCONT to happen.
*
* SIGHUP has a delayed handler, because modifying linked list
* of struct action's from a signal handler while it is manipulated
* by the program may be disastrous.
*
* Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
* it to happen even somewhere inside "sysinit" would be a bit awkward.
*
* There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
* and only one will be remembered and acted upon.
*/
/* The SIGUSR[12]/SIGTERM handler */
static void halt_reboot_pwoff(int sig) NORETURN;
static void halt_reboot_pwoff(int sig)
{
const char *m;
unsigned rb;
/* We may call run() and it unmasks signals,
* including the one masked inside this signal handler.
* Testcase which would start multiple reboot scripts:
* while true; do reboot; done
* Preventing it:
*/
reset_sighandlers_and_unblock_sigs();
run_shutdown_and_kill_processes();
m = "halt";
rb = RB_HALT_SYSTEM;
if (sig == SIGTERM) {
m = "reboot";
rb = RB_AUTOBOOT;
} else if (sig == SIGUSR2) {
m = "poweroff";
rb = RB_POWER_OFF;
}
message(L_CONSOLE, "Requesting system %s", m);
pause_and_low_level_reboot(rb);
/* not reached */
}
/* Handler for QUIT - exec "restart" action,
* else (no such action defined) do nothing */
static void restart_handler(int sig UNUSED_PARAM)
{
struct init_action *a;
for (a = init_action_list; a; a = a->next) {
if (!(a->action_type & RESTART))
continue;
/* Starting from here, we won't return.
* Thus don't need to worry about preserving errno
* and such.
*/
reset_sighandlers_and_unblock_sigs();
run_shutdown_and_kill_processes();
#ifdef RB_ENABLE_CAD
/* Allow Ctrl-Alt-Del to reboot the system.
* This is how kernel sets it up for init, we follow suit.
*/
reboot(RB_ENABLE_CAD); /* misnomer */
#endif
if (open_stdio_to_tty(a->terminal)) {
dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
/* Theoretically should be safe.
* But in practice, kernel bugs may leave
* unkillable processes, and wait() may block forever.
* Oh well. Hoping "new" init won't be too surprised
* by having children it didn't create.
*/
//while (wait(NULL) > 0)
// continue;
init_exec(a->command);
}
/* Open or exec failed */
pause_and_low_level_reboot(RB_HALT_SYSTEM);
/* not reached */
}
}
/* The SIGSTOP/SIGTSTP handler
* NB: inside it, all signals except SIGCONT are masked
* via appropriate setup in sigaction().
*/
static void stop_handler(int sig UNUSED_PARAM)
{
smallint saved_bb_got_signal;
int saved_errno;
saved_bb_got_signal = bb_got_signal;
saved_errno = errno;
signal(SIGCONT, record_signo);
while (1) {
pid_t wpid;
if (bb_got_signal == SIGCONT)
break;
/* NB: this can accidentally wait() for a process
* which we waitfor() elsewhere! waitfor() must have
* code which is resilient against this.
*/
wpid = wait_any_nohang(NULL);
mark_terminated(wpid);
sleep(1);
}
signal(SIGCONT, SIG_DFL);
errno = saved_errno;
bb_got_signal = saved_bb_got_signal;
}
#if ENABLE_FEATURE_USE_INITTAB
static void reload_inittab(void)
{
struct init_action *a, **nextp;
message(L_LOG, "reloading /etc/inittab");
/* Disable old entries */
for (a = init_action_list; a; a = a->next)
a->action_type = 0;
/* Append new entries, or modify existing entries
* (incl. setting a->action_type) if cmd and device name
* match new ones. End result: only entries with
* a->action_type == 0 are stale.
*/
parse_inittab();
#if ENABLE_FEATURE_KILL_REMOVED
/* Kill stale entries */
/* Be nice and send SIGTERM first */
for (a = init_action_list; a; a = a->next)
if (a->action_type == 0 && a->pid != 0)
kill(a->pid, SIGTERM);
if (CONFIG_FEATURE_KILL_DELAY) {
/* NB: parent will wait in NOMMU case */
if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
sleep(CONFIG_FEATURE_KILL_DELAY);
for (a = init_action_list; a; a = a->next)
if (a->action_type == 0 && a->pid != 0)
kill(a->pid, SIGKILL);
_exit(EXIT_SUCCESS);
}
}
#endif
/* Remove stale entries and SYSINIT entries.
* We never rerun SYSINIT entries anyway,
* removing them too saves a few bytes */
nextp = &init_action_list;
while ((a = *nextp) != NULL) {
if ((a->action_type & ~SYSINIT) == 0) {
*nextp = a->next;
free(a);
} else {
nextp = &a->next;
}
}
/* Not needed: */
/* run_actions(RESPAWN | ASKFIRST); */
/* - we return to main loop, which does this automagically */
}
#endif
static int check_delayed_sigs(void)
{
int sigs_seen = 0;
while (1) {
smallint sig = bb_got_signal;
if (!sig)
return sigs_seen;
bb_got_signal = 0;
sigs_seen = 1;
#if ENABLE_FEATURE_USE_INITTAB
if (sig == SIGHUP)
reload_inittab();
#endif
if (sig == SIGINT)
run_actions(CTRLALTDEL);
}
}
int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int init_main(int argc UNUSED_PARAM, char **argv)
{
if (argv[1] && strcmp(argv[1], "-q") == 0) {
return kill(1, SIGHUP);
}
if (!DEBUG_INIT) {
/* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
if (getpid() != 1
&& (!ENABLE_FEATURE_INITRD || applet_name[0] != 'l') /* not linuxrc? */
) {
bb_error_msg_and_die("must be run as PID 1");
}
#ifdef RB_DISABLE_CAD
/* Turn off rebooting via CTL-ALT-DEL - we get a
* SIGINT on CAD so we can shut things down gracefully... */
reboot(RB_DISABLE_CAD); /* misnomer */
#endif
}
/* If, say, xmalloc would ever die, we don't want to oops kernel
* by exiting.
* NB: we set die_sleep *after* PID 1 check and bb_show_usage.
* Otherwise, for example, "init u" ("please rexec yourself"
* command for sysvinit) will show help text (which isn't too bad),
* *and sleep forever* (which is bad!)
*/
die_sleep = 30 * 24*60*60;
/* Figure out where the default console should be */
console_init();
set_sane_term();
xchdir("/");
setsid();
/* Make sure environs is set to something sane */
putenv((char *) "HOME=/");
putenv((char *) bb_PATH_root_path);
putenv((char *) "SHELL=/bin/sh");
putenv((char *) "USER=root"); /* needed? why? */
if (argv[1])
xsetenv("RUNLEVEL", argv[1]);
#if !ENABLE_FEATURE_EXTRA_QUIET
/* Hello world */
message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
#endif
/* struct sysinfo is linux-specific */
#ifdef __linux__
/* Make sure there is enough memory to do something useful. */
if (ENABLE_SWAPONOFF) {
struct sysinfo info;
if (sysinfo(&info) == 0
&& (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024
) {
message(L_CONSOLE, "Low memory, forcing swapon");
/* swapon -a requires /proc typically */
new_init_action(SYSINIT, "mount -t proc proc /proc", "");
/* Try to turn on swap */
new_init_action(SYSINIT, "swapon -a", "");
run_actions(SYSINIT); /* wait and removing */
}
}
#endif
/* Check if we are supposed to be in single user mode */
if (argv[1]
&& (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
) {
/* ??? shouldn't we set RUNLEVEL="b" here? */
/* Start a shell on console */
new_init_action(RESPAWN, bb_default_login_shell, "");
} else {
/* Not in single user mode - see what inittab says */
/* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
* then parse_inittab() simply adds in some default
* actions(i.e., INIT_SCRIPT and a pair
* of "askfirst" shells */
parse_inittab();
}
#if ENABLE_SELINUX
if (getenv("SELINUX_INIT") == NULL) {
int enforce = 0;
putenv((char*)"SELINUX_INIT=YES");
if (selinux_init_load_policy(&enforce) == 0) {
BB_EXECVP(argv[0], argv);
} else if (enforce > 0) {
/* SELinux in enforcing mode but load_policy failed */
message(L_CONSOLE, "can't load SELinux Policy. "
"Machine is in enforcing mode. Halting now.");
return EXIT_FAILURE;
}
}
#endif
/* Make the command line just say "init" - thats all, nothing else */
strncpy(argv[0], "init", strlen(argv[0]));
/* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
while (*++argv)
memset(*argv, 0, strlen(*argv));
/* Set up signal handlers */
if (!DEBUG_INIT) {
struct sigaction sa;
bb_signals(0
+ (1 << SIGUSR1) /* halt */
+ (1 << SIGTERM) /* reboot */
+ (1 << SIGUSR2) /* poweroff */
, halt_reboot_pwoff);
signal(SIGQUIT, restart_handler); /* re-exec another init */
/* Stop handler must allow only SIGCONT inside itself */
memset(&sa, 0, sizeof(sa));
sigfillset(&sa.sa_mask);
sigdelset(&sa.sa_mask, SIGCONT);
sa.sa_handler = stop_handler;
/* NB: sa_flags doesn't have SA_RESTART.
* It must be able to interrupt wait().
*/
sigaction_set(SIGTSTP, &sa); /* pause */
/* Does not work as intended, at least in 2.6.20.
* SIGSTOP is simply ignored by init:
*/
sigaction_set(SIGSTOP, &sa); /* pause */
/* SIGINT (Ctrl-Alt-Del) must interrupt wait(),
* setting handler without SA_RESTART flag.
*/
bb_signals_recursive_norestart((1 << SIGINT), record_signo);
}
/* Set up "reread /etc/inittab" handler.
* Handler is set up without SA_RESTART, it will interrupt syscalls.
*/
if (!DEBUG_INIT && ENABLE_FEATURE_USE_INITTAB)
bb_signals_recursive_norestart((1 << SIGHUP), record_signo);
/* Now run everything that needs to be run */
/* First run the sysinit command */
run_actions(SYSINIT);
check_delayed_sigs();
/* Next run anything that wants to block */
run_actions(WAIT);
check_delayed_sigs();
/* Next run anything to be run only once */
run_actions(ONCE);
/* Now run the looping stuff for the rest of forever.
*/
while (1) {
int maybe_WNOHANG;
maybe_WNOHANG = check_delayed_sigs();
/* (Re)run the respawn/askfirst stuff */
run_actions(RESPAWN | ASKFIRST);
maybe_WNOHANG |= check_delayed_sigs();
/* Don't consume all CPU time - sleep a bit */
sleep(1);
maybe_WNOHANG |= check_delayed_sigs();
/* Wait for any child process(es) to exit.
*
* If check_delayed_sigs above reported that a signal
* was caught, wait will be nonblocking. This ensures
* that if SIGHUP has reloaded inittab, respawn and askfirst
* actions will not be delayed until next child death.
*/
if (maybe_WNOHANG)
maybe_WNOHANG = WNOHANG;
while (1) {
pid_t wpid;
struct init_action *a;
/* If signals happen _in_ the wait, they interrupt it,
* bb_signals_recursive_norestart set them up that way
*/
wpid = waitpid(-1, NULL, maybe_WNOHANG);
if (wpid <= 0)
break;
a = mark_terminated(wpid);
if (a) {
message(L_LOG, "process '%s' (pid %d) exited. "
"Scheduling for restart.",
a->command, wpid);
}
/* See if anyone else is waiting to be reaped */
maybe_WNOHANG = WNOHANG;
}
} /* while (1) */
}
//usage:#define linuxrc_trivial_usage NOUSAGE_STR
//usage:#define linuxrc_full_usage ""
//usage:#define init_trivial_usage
//usage: ""
//usage:#define init_full_usage "\n\n"
//usage: "Init is the parent of all processes"
//usage:
//usage:#define init_notes_usage
//usage: "This version of init is designed to be run only by the kernel.\n"
//usage: "\n"
//usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
//usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
//usage: "runlevels, use sysvinit.\n"
//usage: "\n"
//usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n"
//usage: "it has the following default behavior:\n"
//usage: "\n"
//usage: " ::sysinit:/etc/init.d/rcS\n"
//usage: " ::askfirst:/bin/sh\n"
//usage: " ::ctrlaltdel:/sbin/reboot\n"
//usage: " ::shutdown:/sbin/swapoff -a\n"
//usage: " ::shutdown:/bin/umount -a -r\n"
//usage: " ::restart:/sbin/init\n"
//usage: "\n"
//usage: "if it detects that /dev/console is _not_ a serial console, it will also run:\n"
//usage: "\n"
//usage: " tty2::askfirst:/bin/sh\n"
//usage: " tty3::askfirst:/bin/sh\n"
//usage: " tty4::askfirst:/bin/sh\n"
//usage: "\n"
//usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
//usage: "\n"
//usage: " <id>:<runlevels>:<action>:<process>\n"
//usage: "\n"
//usage: " <id>:\n"
//usage: "\n"
//usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n"
//usage: " The id field is used by BusyBox init to specify the controlling tty for\n"
//usage: " the specified process to run on. The contents of this field are\n"
//usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n"
//usage: " be unique, although if it isn't you may have strange results. If this\n"
//usage: " field is left blank, the controlling tty is set to the console. Also\n"
//usage: " note that if BusyBox detects that a serial console is in use, then only\n"
//usage: " entries whose controlling tty is either the serial console or /dev/null\n"
//usage: " will be run. BusyBox init does nothing with utmp. We don't need no\n"
//usage: " stinkin' utmp.\n"
//usage: "\n"
//usage: " <runlevels>:\n"
//usage: "\n"
//usage: " The runlevels field is completely ignored.\n"
//usage: "\n"
//usage: " <action>:\n"
//usage: "\n"
//usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n"
//usage: " once, restart, ctrlaltdel, and shutdown.\n"
//usage: "\n"
//usage: " The available actions can be classified into two groups: actions\n"
//usage: " that are run only once, and actions that are re-run when the specified\n"
//usage: " process exits.\n"
//usage: "\n"
//usage: " Run only-once actions:\n"
//usage: "\n"
//usage: " 'sysinit' is the first item run on boot. init waits until all\n"
//usage: " sysinit actions are completed before continuing. Following the\n"
//usage: " completion of all sysinit actions, all 'wait' actions are run.\n"
//usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n"
//usage: " the specified task completes. 'once' actions are asynchronous,\n"
//usage: " therefore, init does not wait for them to complete. 'restart' is\n"
//usage: " the action taken to restart the init process. By default this should\n"
//usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n"
//usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
//usage: " actions are run when the system detects that someone on the system\n"
//usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
//usage: " wants to run 'reboot' at this point to cause the system to reboot.\n"
//usage: " Finally the 'shutdown' action specifies the actions to taken when\n"
//usage: " init is told to reboot. Unmounting filesystems and disabling swap\n"
//usage: " is a very good here.\n"
//usage: "\n"
//usage: " Run repeatedly actions:\n"
//usage: "\n"
//usage: " 'respawn' actions are run after the 'once' actions. When a process\n"
//usage: " started with a 'respawn' action exits, init automatically restarts\n"
//usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n"
//usage: " respawning out of control. The 'askfirst' actions acts just like\n"
//usage: " respawn, except that before running the specified process it\n"
//usage: " displays the line \"Please press Enter to activate this console.\"\n"
//usage: " and then waits for the user to press enter before starting the\n"
//usage: " specified process.\n"
//usage: "\n"
//usage: " Unrecognized actions (like initdefault) will cause init to emit an\n"
//usage: " error message, and then go along with its business. All actions are\n"
//usage: " run in the order they appear in /etc/inittab.\n"
//usage: "\n"
//usage: " <process>:\n"
//usage: "\n"
//usage: " Specifies the process to be executed and its command line.\n"
//usage: "\n"
//usage: "Example /etc/inittab file:\n"
//usage: "\n"
//usage: " # This is run first except when booting in single-user mode\n"
//usage: " #\n"
//usage: " ::sysinit:/etc/init.d/rcS\n"
//usage: " \n"
//usage: " # /bin/sh invocations on selected ttys\n"
//usage: " #\n"
//usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n"
//usage: " ::askfirst:-/bin/sh\n"
//usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n"
//usage: " tty2::askfirst:-/bin/sh\n"
//usage: " tty3::askfirst:-/bin/sh\n"
//usage: " tty4::askfirst:-/bin/sh\n"
//usage: " \n"
//usage: " # /sbin/getty invocations for selected ttys\n"
//usage: " #\n"
//usage: " tty4::respawn:/sbin/getty 38400 tty4\n"
//usage: " tty5::respawn:/sbin/getty 38400 tty5\n"
//usage: " \n"
//usage: " \n"
//usage: " # Example of how to put a getty on a serial line (for a terminal)\n"
//usage: " #\n"
//usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
//usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
//usage: " #\n"
//usage: " # Example how to put a getty on a modem line\n"
//usage: " #::respawn:/sbin/getty 57600 ttyS2\n"
//usage: " \n"
//usage: " # Stuff to do when restarting the init process\n"
//usage: " ::restart:/sbin/init\n"
//usage: " \n"
//usage: " # Stuff to do before rebooting\n"
//usage: " ::ctrlaltdel:/sbin/reboot\n"
//usage: " ::shutdown:/bin/umount -a -r\n"
//usage: " ::shutdown:/sbin/swapoff -a\n"