init.c

手机嵌入式Linux下可用的busybox源码

/* vi: set sw=4 ts=4: */
/*
 * Mini init implementation for busybox
 *
 *
 * Copyright (C) 1995, 1996 by Bruce Perens <[e-mail]>.
 * Copyright (C) 1999-2002 Erik Andersen <[e-mail]>
 * Adjusted by so many folks, it's impossible to keep track.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

/* Turn this on to disable all the dangerous 
   rebooting stuff when debugging.
#define DEBUG_INIT
*/

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <paths.h>
#include <signal.h>
#include <stdarg.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <limits.h>
#include <sys/fcntl.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/wait.h>
#include "busybox.h"
#ifdef BB_SYSLOGD
# include <sys/syslog.h>
#endif

#define INIT_BUFFS_SIZE 256

/* From <linux/vt.h> */
struct vt_stat {
	unsigned short v_active;        /* active vt */
	unsigned short v_signal;        /* signal to send */
	unsigned short v_state;         /* vt bitmask */
};
static const int VT_GETSTATE = 0x5603;  /* get global vt state info */

/* From <linux/serial.h> */
struct serial_struct {
	int     type;
	int     line;
	int     port;
	int     irq;
	int     flags;
	int     xmit_fifo_size;
	int     custom_divisor;
	int     baud_base;
	unsigned short  close_delay;
	char    reserved_char[2];
	int     hub6;
	unsigned short  closing_wait; /* time to wait before closing */
	unsigned short  closing_wait2; /* no longer used... */
	int     reserved[4];
};


#if (__GNU_LIBRARY__ > 5) || defined(__dietlibc__) 
  #include <sys/reboot.h>
  #define init_reboot(magic) reboot(magic)
#else
  #define init_reboot(magic) reboot(0xfee1dead, 672274793, magic)
#endif

#ifndef _PATH_STDPATH
#define _PATH_STDPATH	"/usr/bin:/bin:/usr/sbin:/sbin"
#endif

#if defined BB_FEATURE_INIT_COREDUMPS
/*
 * When a file named CORE_ENABLE_FLAG_FILE 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....
 */
#define CORE_ENABLE_FLAG_FILE "/.init_enable_core"
#include <sys/resource.h>
#include <sys/time.h>
#endif

#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))

#if __GNU_LIBRARY__ > 5
	#include <sys/kdaemon.h>
#else
	extern int bdflush (int func, long int data);
#endif

#define SHELL        "/bin/sh"	     /* Default shell */
#define LOGIN_SHELL  "-" SHELL	     /* Default login shell */
#define INITTAB      "/etc/inittab"  /* inittab file location */
#ifndef INIT_SCRIPT
#define INIT_SCRIPT  "/etc/init.d/rcS"   /* Default sysinit script. */
#endif

#define MAXENV	16		/* Number of env. vars */

/* Allowed init action types */
#define SYSINIT     0x001
#define RESPAWN     0x002
#define ASKFIRST    0x004
#define WAIT        0x008
#define ONCE        0x010
#define CTRLALTDEL  0x020
#define SHUTDOWN    0x040
#define RESTART     0x080

/* A mapping between "inittab" action name strings and action type codes. */
struct init_action_type {
	const char *name;
	int action;
};

static const struct init_action_type actions[] = {
	{"sysinit", SYSINIT},
	{"respawn", RESPAWN},
	{"askfirst", ASKFIRST},
	{"wait", WAIT},
	{"once", ONCE},
	{"ctrlaltdel", CTRLALTDEL},
	{"shutdown", SHUTDOWN},
	{"restart", RESTART},
	{0, 0}
};

/* Set up a linked list of init_actions, to be read from inittab */
struct init_action {
	pid_t pid;
	char command[INIT_BUFFS_SIZE];
	char terminal[INIT_BUFFS_SIZE];
	struct init_action *next;
	int action;
};

/* Static variables */
static struct init_action *init_action_list = NULL;
static int  kernelVersion  = 0;
static char termType[32]   = "TERM=linux";
static char console[32]    = _PATH_CONSOLE;
#ifndef BB_SYSLOGD
static char *log           = VC_5;
#endif
static sig_atomic_t got_cont = 0;
static const int LOG = 0x1;
static const int CONSOLE = 0x2;
#if defined BB_FEATURE_EXTRA_QUIET
static const int MAYBE_CONSOLE = 0x0;
#else
#define MAYBE_CONSOLE	CONSOLE
#endif
#ifndef RB_HALT_SYSTEM
static const int RB_HALT_SYSTEM = 0xcdef0123;
static const int RB_ENABLE_CAD = 0x89abcdef;
static const int RB_DISABLE_CAD = 0;
#define RB_POWER_OFF    0x4321fedc
static const int RB_AUTOBOOT = 0x01234567;
#endif

/* Function prototypes */
static void delete_init_action(struct init_action *a);
static int waitfor(struct init_action *a);


static void loop_forever(void)
{
	while (1)
		sleep (1);
}

/* Print a message to the specified device.
 * Device may be bitwise-or'd from LOG | CONSOLE */
#ifdef DEBUG_INIT
static inline messageND(int device, char *fmt, ...) { }
#else 
#define messageND message
#endif
static void message(int device, char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
static void message(int device, char *fmt, ...)
{
	va_list arguments;
	int fd;

#ifdef BB_SYSLOGD

	/* Log the message to syslogd */
	if (device & LOG) {
		char msg[1024];

		va_start(arguments, fmt);
		vsnprintf(msg, sizeof(msg), fmt, arguments);
		va_end(arguments);
		syslog_msg(LOG_USER, LOG_INFO, msg);
	}
#else
	static int log_fd = -1;

	/* Take full control of the log tty, and never close it.
	 * It's mine, all mine!  Muhahahaha! */
	if (log_fd < 0) {
		if ((log_fd = device_open(log, O_RDWR|O_NDELAY)) < 0) {
			log_fd = -2;
			fprintf(stderr, "Bummer, can't write to log on %s!\n", log);
			device = CONSOLE;
		} else {
			fcntl(log_fd, F_SETFD, FD_CLOEXEC);
		}
	}
	if ((device & LOG) && (log_fd >= 0)) {
		va_start(arguments, fmt);
		vdprintf(log_fd, fmt, arguments);
		va_end(arguments);
	}
#endif

	if (device & CONSOLE) {
		/* Always send console messages to /dev/console so people will see them. */
		if (
			(fd =
			 device_open(_PATH_CONSOLE, O_WRONLY | O_NOCTTY | O_NDELAY)) >= 0) {
			va_start(arguments, fmt);
			vdprintf(fd, fmt, arguments);
			va_end(arguments);
			close(fd);
		} else {
			fprintf(stderr, "Bummer, can't print: ");
			va_start(arguments, fmt);
			vfprintf(stderr, fmt, arguments);
			va_end(arguments);
		}
	}
}

/* Set terminal settings to reasonable defaults */
static void set_term(int fd)
{
	struct termios tty;

	tcgetattr(fd, &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 */

	/* use line dicipline 0 */
	tty.c_line = 0;

	/* Make it be sane */
	tty.c_cflag &= CBAUD|CBAUDEX|CSIZE|CSTOPB|PARENB|PARODD;
	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(fd, TCSANOW, &tty);
}

/* How much memory does this machine have?
   Units are kBytes to avoid overflow on 4GB machines */
static int check_free_memory(void)
{
	struct sysinfo info;
	unsigned int result, u, s=10;

	if (sysinfo(&info) != 0) {
		perror_msg("Error checking free memory");
		return -1;
	}

	/* Kernels 2.0.x and 2.2.x return info.mem_unit==0 with values in bytes.
	 * Kernels 2.4.0 return info.mem_unit in bytes. */
	u = info.mem_unit;
	if (u==0) u=1;
	while ( (u&1) == 0 && s > 0 ) { u>>=1; s--; }
	result = (info.totalram>>s) + (info.totalswap>>s);
	result = result*u;
	if (result < 0) result = INT_MAX;
	return result;
}

static void console_init(void)
{
	int fd;
	int tried_devcons = 0;
	int tried_vtprimary = 0;
	struct vt_stat vt;
	struct serial_struct sr;
	char *s;

	if ((s = getenv("TERM")) != NULL) {
		snprintf(termType, sizeof(termType) - 1, "TERM=%s", s);
	}

	if ((s = getenv("CONSOLE")) != NULL) {
		safe_strncpy(console, s, sizeof(console));
	}
#if #cpu(sparc)
	/* sparc kernel supports console=tty[ab] parameter which is also 
	 * passed to init, so catch it here */
	else if ((s = getenv("console")) != NULL) {
		/* remap tty[ab] to /dev/ttyS[01] */
		if (strcmp(s, "ttya") == 0)
			safe_strncpy(console, SC_0, sizeof(console));
		else if (strcmp(s, "ttyb") == 0)
			safe_strncpy(console, SC_1, sizeof(console));
	}
#endif
	else {
		/* 2.2 kernels: identify the real console backend and try to use it */
		if (ioctl(0, TIOCGSERIAL, &sr) == 0) {
			/* this is a serial console */
			snprintf(console, sizeof(console) - 1, SC_FORMAT, sr.line);
		} else if (ioctl(0, VT_GETSTATE, &vt) == 0) {
			/* this is linux virtual tty */
			snprintf(console, sizeof(console) - 1, VC_FORMAT, vt.v_active);
		} else {
			safe_strncpy(console, _PATH_CONSOLE, sizeof(console));
			tried_devcons++;
		}
	}

	while ((fd = open(console, O_RDONLY | O_NONBLOCK)) < 0) {
		/* Can't open selected console -- try /dev/console */
		if (!tried_devcons) {
			tried_devcons++;
			safe_strncpy(console, _PATH_CONSOLE, sizeof(console));
			continue;
		}
		/* Can't open selected console -- try vt1 */
		if (!tried_vtprimary) {
			tried_vtprimary++;
			safe_strncpy(console, VC_1, sizeof(console));
			continue;
		}
		break;
	}
	if (fd < 0) {
		/* Perhaps we should panic here? */
		safe_strncpy(console, "/dev/null", sizeof(console));
	} else {
		/* check for serial console */
		if (ioctl(0, TIOCGSERIAL, &sr) == 0) {
			/* Force the TERM setting to vt102 for serial console --
			 * if TERM is set to linux (the default) */
			if (strcmp( termType, "TERM=linux" ) == 0)
				safe_strncpy(termType, "TERM=vt102", sizeof(termType));
		}
		close(fd);
	}
	message(LOG, "console=%s\n", console);
}
	
static void fixup_argv(int argc, char **argv, char *new_argv0)
{
	int len;
	/* Fix up argv[0] to be certain we claim to be init */
	len = strlen(argv[0]);
	memset(argv[0], 0, len);
	safe_strncpy(argv[0], new_argv0, len + 1);

	/* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
	len = 1;
	while (argc > len) {
		memset(argv[len], 0, strlen(argv[len]));
		len++;
	}
}

/* Make sure there is enough memory to do something useful. *
 * Calls "swapon -a" if needed so be sure /etc/fstab is present... */
static void check_memory(void)
{
#if !defined(__UCLIBC__) || defined(__UCLIBC_HAS_MMU__)
	struct stat statBuf;
#endif

	if (check_free_memory() > 1000)
		return;

#if !defined(__UCLIBC__) || defined(__UCLIBC_HAS_MMU__)
	if (stat("/etc/fstab", &statBuf) == 0) {
		/* swapon -a requires /proc typically */
		system("/bin/mount -t proc proc /proc");
		/* Try to turn on swap */
		system("/sbin/swapon -a");
		if (check_free_memory() < 1000)
			goto goodnight;
	} else
		goto goodnight;
	return;
  goodnight:
#endif
	message(CONSOLE,
			"\rSorry, your computer does not have enough memory.\n");
	loop_forever();
}

static pid_t run(struct init_action *a)
{
	struct stat sb;
	int i, j, junk;
	pid_t pid, pgrp, tmp_pid;
	char *s, *tmpCmd, *cmd[INIT_BUFFS_SIZE], *cmdpath;
	char buf[INIT_BUFFS_SIZE+6];    /* INIT_BUFFS_SIZE+strlen("exec ")+1 */
	sigset_t nmask, omask;
	char *environment[MAXENV+1] = {
		termType,
		"HOME=/",
		"PATH=" _PATH_STDPATH,
		"SHELL=" SHELL,
		"USER=root",
		NULL
	};
	static const char press_enter[] =
#ifdef CUSTOMIZED_BANNER
#include CUSTOMIZED_BANNER
#endif
		"\nPlease press Enter to activate this console. ";
#if __GNUC__
	/* Avoid longjmp clobbering */
	(void) &tmp_pid;
#endif

	/* inherit environment to the child, merging our values -andy */
	for (i=0; environ[i]; i++) {
		for (j=0; environment[j]; j++) {
			s = strchr(environment[j], '=');
			if (!strncmp(environ[i], environment[j], s - environment[j]))
				break;
		}
		if (!environment[j]) {
			environment[j++] = environ[i];
			environment[j] = NULL;
		}
	}

	/* Block sigchild while forking.  */
	sigemptyset(&nmask);
	sigaddset(&nmask, SIGCHLD);
	sigprocmask(SIG_BLOCK, &nmask, &omask);

	if ((pid = fork()) == 0) 
	{
		/* Clean up */
		close(0);
		close(1);
		close(2);
		sigprocmask(SIG_SETMASK, &omask, NULL);

		/* Reset signal handlers that were set by the parent process */
		signal(SIGUSR1, SIG_DFL);
		signal(SIGUSR2, SIG_DFL);
		signal(SIGINT,  SIG_DFL);
		signal(SIGTERM, SIG_DFL);
		signal(SIGHUP,  SIG_DFL);
		signal(SIGCONT, SIG_DFL);
		signal(SIGSTOP, SIG_DFL);
		signal(SIGTSTP, SIG_DFL);

		/* Create a new session and make ourself the process
		 * group leader */
		setsid();

		/* Open the new terminal device */
		if ((device_open(a->terminal, O_RDWR)) < 0) {
			if (stat(a->terminal, &sb) != 0) {
				message(LOG | CONSOLE, "\rdevice '%s' does not exist.\n",
						a->terminal);
				_exit(1);
			}
			message(LOG | CONSOLE, "\rBummer, can't open %s\n", a->terminal);
			_exit(1);
		}

		/* Make sure the terminal will act fairly normal for us */
		set_term(0);
		/* Setup stdout, stderr for the new process so
		 * they point to the supplied terminal */
		dup(0);
		dup(0);

		/* If the init Action requires us to wait, then force the
		 * supplied terminal to be the controlling tty. */
		if (a->action & (SYSINIT|WAIT|CTRLALTDEL|SHUTDOWN|RESTART)) {

			/* Now fork off another process to just hang around */
			if ((pid = fork()) < 0) {
				message(LOG | CONSOLE, "Can't fork!\n");
				_exit(1);
			}

			if (pid > 0) {

				/* We are the parent -- wait till the child is done */
				signal(SIGINT, SIG_IGN);
				signal(SIGTSTP, SIG_IGN);
				signal(SIGQUIT, SIG_IGN);
				signal(SIGCHLD, SIG_DFL);

				/* Wait for child to exit */
				while ((tmp_pid = waitpid(pid, &junk, 0)) != pid)
					;

				/* See if stealing the controlling tty back is necessary */
				pgrp = tcgetpgrp(0);
				if (pgrp != getpid())
					_exit(0);

				/* Use a temporary process to steal the controlling tty. */
				if ((pid = fork()) < 0) {
					message(LOG | CONSOLE, "\rCan't fork!\n");
					_exit(1);
				}       
				if (pid == 0) {
					setsid();
					ioctl(0, TIOCSCTTY, 1);
					_exit(0);
				}       
				while((tmp_pid = waitpid(pid, &junk, 0)) != pid) {
					if (tmp_pid < 0 && errno == ECHILD)
						break;
				}
				_exit(0);
			}

			/* Now fall though to actually execute things */
		}

		/* See if any special /bin/sh requiring characters are present */
		if (strpbrk(a->command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
			cmd[0] = SHELL;
			cmd[1] = "-c";
			strcat(strcpy(buf, "exec "), a->command);
			cmd[2] = buf;
			cmd[3] = NULL;
		} else {
			/* Convert command (char*) into cmd (char**, one word per string) */
			strcpy(buf, a->command);
			s = buf;
			for (tmpCmd = buf, i = 0;
					(tmpCmd = strsep(&s, " \t")) != NULL;) {
				if (*tmpCmd != '\0') {
					cmd[i] = tmpCmd;
					i++;
				}