/* 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. */ //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 LINUXRC //config: bool "Support running init from within an initrd (not initramfs)" //config: default y //config: select FEATURE_SYSLOG //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 FEATURE_USE_INITTAB //config: bool "Support reading an inittab file" //config: default y //config: depends on INIT || LINUXRC //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 || LINUXRC //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 || LINUXRC //config: //config:config FEATURE_EXTRA_QUIET //config: bool "Be _extra_ quiet on boot" //config: default y //config: depends on INIT || LINUXRC //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 || LINUXRC //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 INIT_TERMINAL_TYPE //config: string "Initial terminal type" //config: default "linux" //config: depends on INIT || LINUXRC //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. //config: //config:config FEATURE_INIT_MODIFY_CMDLINE //config: bool "Modify the command-line to \"init\"" //config: default y //config: depends on INIT || LINUXRC //config: help //config: When launched as PID 1 and after parsing its arguments, init //config: wipes all the arguments but argv[0] and rewrites argv[0] to //config: contain only "init", so that its command-line appears solely as //config: "init" in tools such as ps. //config: If this option is set to Y, init will keep its original behavior, //config: otherwise, all the arguments including argv[0] will be preserved, //config: be they parsed or ignored by init. //config: The original command-line used to launch init can then be //config: retrieved in /proc/1/cmdline on Linux, for example. //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP)) //applet:IF_LINUXRC(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc)) //kbuild:lib-$(CONFIG_INIT) += init.o //kbuild:lib-$(CONFIG_LINUXRC) += init.o #define DEBUG_SEGV_HANDLER 0 #include "libbb.h" #include <syslog.h> #include <sys/resource.h> #ifdef __linux__ # include <linux/vt.h> # include <sys/sysinfo.h> #endif #include "reboot.h" /* reboot() constants */ #if DEBUG_SEGV_HANDLER # undef _GNU_SOURCE # define _GNU_SOURCE 1 # undef __USE_GNU # define __USE_GNU 1 # include <execinfo.h> # include <sys/ucontext.h> #endif /* 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 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[1]; }; 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) - 2) l = sizeof(msg) - 2; 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 defined(__FreeBSD__) || defined(__FreeBSD_kernel__) /* BSD people say their kernels do not open fd 0,1,2; they need this: */ if (!s) s = (char*)"/dev/console"; #endif 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. * 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) { /* +8 allows to write VLA sizes below more efficiently: */ unsigned command_size = strlen(command) + 8; /* strlen(command) + strlen("exec ")+1: */ char buf[command_size]; /* strlen(command) / 2 + 4: */ char *cmd[command_size / 2]; int dash; 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) { update_utmp_DEAD_PROCESS(pid); for (a = init_action_list; a; a = a->next) { if (a->pid == pid) { a->pid = 0; return a; } } } 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; goto append; } nextp = &a->next; } a = xzalloc(sizeof(*a) + strlen(command)); /* Append to the end of the list */ append: *nextp = a; a->action_type = action_type; strcpy(a->command, command); safe_strncpy(a->terminal, cons, sizeof(a->terminal)); dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%x 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 */ /* Sysinit */ new_init_action(SYSINIT, INIT_SCRIPT, ""); /* 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); /* 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 */ new_init_action(SHUTDOWN, "swapoff -a", ""); /* Restart init when a QUIT is received */ new_init_action(RESTART, "init", ""); 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 SIGPWR/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 exec_restart_action(void) { 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) { /* * Why pid == 0 check? * Process can be removed from inittab and added *later*. * If we delete its entry but process still runs, * duplicate is spawned when the entry is re-added. */ if ((a->action_type & ~SYSINIT) == 0 && a->pid == 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); if (sig == SIGQUIT) { exec_restart_action(); /* returns only if no restart action defined */ } if ((1 << sig) & (0 #ifdef SIGPWR + (1 << SIGPWR) #endif + (1 << SIGUSR1) + (1 << SIGUSR2) + (1 << SIGTERM) )) { halt_reboot_pwoff(sig); } } } #if DEBUG_SEGV_HANDLER static void handle_sigsegv(int sig, siginfo_t *info, void *ucontext) { long ip; ucontext_t *uc; uc = ucontext; ip = uc->uc_mcontext.gregs[REG_EIP]; fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n", sig, /* this is void*, but using %p would print "(null)" * even for ptrs which are not exactly 0, but, say, 0x123: */ (long)info->si_addr, ip); { /* glibc extension */ void *array[50]; int size; size = backtrace(array, 50); backtrace_symbols_fd(array, size, 2); } for (;;) sleep(9999); } #endif static void sleep_much(void) { sleep(30 * 24*60*60); } 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_SEGV_HANDLER { struct sigaction sa; memset(&sa, 0, sizeof(sa)); sa.sa_sigaction = handle_sigsegv; sa.sa_flags = SA_SIGINFO; sigaction(SIGSEGV, &sa, NULL); sigaction(SIGILL, &sa, NULL); sigaction(SIGFPE, &sa, NULL); sigaction(SIGBUS, &sa, NULL); } #endif if (!DEBUG_INIT) { /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */ if (getpid() != 1 && (!ENABLE_LINUXRC || 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_func *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_func = sleep_much; /* 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 #if 0 /* It's 2013, does anyone really still depend on this? */ /* If you do, consider adding swapon to sysinit actions then! */ /* struct sysinfo is linux-specific */ # ifdef __linux__ /* Make sure there is enough memory to do something useful. */ /*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ { 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 #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 if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE) { /* Make the command line just say "init" - that's 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) nuke_str(*argv); } /* Set up signal handlers */ if (!DEBUG_INIT) { struct sigaction sa; /* 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 */ /* These signals must interrupt wait(), * setting handler without SA_RESTART flag. */ bb_signals_recursive_norestart(0 + (1 << SIGINT) /* Ctrl-Alt-Del */ + (1 << SIGQUIT) /* re-exec another init */ #ifdef SIGPWR + (1 << SIGPWR) /* halt */ #endif + (1 << SIGUSR1) /* halt */ + (1 << SIGTERM) /* reboot */ + (1 << SIGUSR2) /* poweroff */ #if ENABLE_FEATURE_USE_INITTAB + (1 << SIGHUP) /* reread /etc/inittab */ #endif , 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 first process started during boot. It never exits." //usage: IF_FEATURE_USE_INITTAB( //usage: "\n""It (re)spawns children according to /etc/inittab." //usage: ) //usage: IF_NOT_FEATURE_USE_INITTAB( //usage: "\n""This version of init doesn't use /etc/inittab," //usage: "\n""has fixed set of processed to run." //usage: ) //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: " 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, then the init's stdin/out will be used.\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"