init.c

sysvinit--linux系统下的init

/*
 * Init		A System-V Init Clone.
 *
 * Usage:	/sbin/init
 *		     init [0123456SsQqAaBbCc]
 *		  telinit [0123456SsQqAaBbCc]
 *
 * Version:	@(#)init.c  2.86  30-Jul-2004  [e-mail]
 */
#define VERSION "2.86"
#define DATE    "31-Jul-2004"
/*
 *		This file is part of the sysvinit suite,
 *		Copyright 1991-2004 Miquel van Smoorenburg.
 *
 *		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.
 *
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#ifdef __linux__
#include <sys/kd.h>
#endif
#include <sys/resource.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <time.h>
#include <fcntl.h>
#include <string.h>
#include <signal.h>
#include <termios.h>
#include <utmp.h>
#include <ctype.h>
#include <stdarg.h>
#include <sys/syslog.h>
#include <sys/time.h>

#ifdef __i386__
#  if (__GLIBC__ >= 2)
     /* GNU libc 2.x */
#    define STACK_DEBUG 1
#    if (__GLIBC__ == 2 && __GLIBC_MINOR__ == 0)
       /* Only glibc 2.0 needs this */
#      include <sigcontext.h>
#    endif
#  endif
#endif

#include "init.h"
#include "initreq.h"
#include "paths.h"
#include "reboot.h"
#include "set.h"

#ifndef SIGPWR
#  define SIGPWR SIGUSR2
#endif

#ifndef CBAUD
#  define CBAUD		0
#endif
#ifndef CBAUDEX
#  define CBAUDEX	0
#endif

/* Set a signal handler. */
#define SETSIG(sa, sig, fun, flags) \
		do { \
			sa.sa_handler = fun; \
			sa.sa_flags = flags; \
			sigemptyset(&sa.sa_mask); \
			sigaction(sig, &sa, NULL); \
		} while(0)

/* Version information */
char *Version = "@(#) init " VERSION "  " DATE "  [e-mail]";
char *bootmsg = "version " VERSION " %s";
#define E_VERSION "INIT_VERSION=sysvinit-" VERSION

CHILD *family = NULL;		/* The linked list of all entries */
CHILD *newFamily = NULL;	/* The list after inittab re-read */

CHILD ch_emerg = {		/* Emergency shell */
	0, 0, 0, 0, 0,
	"~~",
	"S",
	3,
	"/sbin/sulogin",
	NULL,
	NULL
};

char runlevel = 'S';		/* The current run level */
char thislevel = 'S';		/* The current runlevel */
char prevlevel = 'N';		/* Previous runlevel */
int dfl_level = 0;		/* Default runlevel */
sig_atomic_t got_cont = 0;	/* Set if we received the SIGCONT signal */
sig_atomic_t got_signals;	/* Set if we received a signal. */
int emerg_shell = 0;		/* Start emergency shell? */
int wrote_wtmp_reboot = 1;	/* Set when we wrote the reboot record */
int wrote_utmp_reboot = 1;	/* Set when we wrote the reboot record */
int sltime = 5;			/* Sleep time between TERM and KILL */
char *argv0;			/* First arguments; show up in ps listing */
int maxproclen;			/* Maximal length of argv[0] with \0 */
struct utmp utproto;		/* Only used for sizeof(utproto.ut_id) */
char *user_console = NULL;	/* User console device */
char *console_dev;		/* Console device. */
int pipe_fd = -1;		/* /dev/initctl */
int did_boot = 0;		/* Did we already do BOOT* stuff? */
int main(int, char **);

/*	Used by re-exec part */
int reload = 0;			/* Should we do initialization stuff? */
char *myname="/sbin/init";	/* What should we exec */
int oops_error;			/* Used by some of the re-exec code. */
const char *Signature = "12567362";	/* Signature for re-exec fd */

/* Macro to see if this is a special action */
#define ISPOWER(i) ((i) == POWERWAIT || (i) == POWERFAIL || \
		    (i) == POWEROKWAIT || (i) == POWERFAILNOW || \
		    (i) == CTRLALTDEL)

/* ascii values for the `action' field. */
struct actions {
  char *name;
  int act;
} actions[] = {
  { "respawn", 	   RESPAWN	},
  { "wait",	   WAIT		},
  { "once",	   ONCE		},
  { "boot",	   BOOT		},
  { "bootwait",	   BOOTWAIT	},
  { "powerfail",   POWERFAIL	},
  { "powerfailnow",POWERFAILNOW },
  { "powerwait",   POWERWAIT	},
  { "powerokwait", POWEROKWAIT	},
  { "ctrlaltdel",  CTRLALTDEL	},
  { "off",	   OFF		},
  { "ondemand",	   ONDEMAND	},
  { "initdefault", INITDEFAULT	},
  { "sysinit",	   SYSINIT	},
  { "kbrequest",   KBREQUEST    },
  { NULL,	   0		},
};

/*
 *	State parser token table (see receive_state)
 */
struct {
  char name[4];	
  int cmd;
} cmds[] = {
  { "VER", 	   C_VER	},
  { "END",	   C_END	},
  { "REC",	   C_REC	},
  { "EOR",	   C_EOR	},
  { "LEV",	   C_LEV	},
  { "FL ",	   C_FLAG	},
  { "AC ",	   C_ACTION	},
  { "CMD",	   C_PROCESS	},
  { "PID",	   C_PID	},
  { "EXS",	   C_EXS	},
  { "-RL",	   D_RUNLEVEL	},
  { "-TL",	   D_THISLEVEL	},
  { "-PL",	   D_PREVLEVEL	},
  { "-SI",	   D_GOTSIGN	},
  { "-WR",	   D_WROTE_WTMP_REBOOT},
  { "-WU",	   D_WROTE_UTMP_REBOOT},
  { "-ST",	   D_SLTIME	},
  { "-DB",	   D_DIDBOOT	},
  { "",	   	   0		}
};
struct {
	char *name;
	int mask;
} flags[]={
	{"RU",RUNNING},
	{"DE",DEMAND},
	{"XD",XECUTED},
	{NULL,0}
};

#define NR_EXTRA_ENV	16
char *extra_env[NR_EXTRA_ENV];


/*
 *	Sleep a number of seconds.
 *
 *	This only works correctly because the linux select updates
 *	the elapsed time in the struct timeval passed to select!
 */
void do_sleep(int sec)
{
	struct timeval tv;

	tv.tv_sec = sec;
	tv.tv_usec = 0;

	while(select(0, NULL, NULL, NULL, &tv) < 0 && errno == EINTR)
		;
}


/*
 *	Non-failing allocation routines (init cannot fail).
 */
void *imalloc(size_t size)
{
	void	*m;

	while ((m = malloc(size)) == NULL) {
		initlog(L_VB, "out of memory");
		do_sleep(5);
	}
	memset(m, 0, size);
	return m;
}


char *istrdup(char *s)
{
	char	*m;
	int	l;

	l = strlen(s) + 1;
	m = imalloc(l);
	memcpy(m, s, l);
	return m;
}


/*
 *	Send the state info of the previous running init to
 *	the new one, in a version-independant way.
 */
void send_state(int fd)
{
	FILE	*fp;
	CHILD	*p;
	int	i,val;

	fp = fdopen(fd,"w");

	fprintf(fp, "VER%s\n", Version);
	fprintf(fp, "-RL%c\n", runlevel);
	fprintf(fp, "-TL%c\n", thislevel);
	fprintf(fp, "-PL%c\n", prevlevel);
	fprintf(fp, "-SI%u\n", got_signals);
	fprintf(fp, "-WR%d\n", wrote_wtmp_reboot);
	fprintf(fp, "-WU%d\n", wrote_utmp_reboot);
	fprintf(fp, "-ST%d\n", sltime);
	fprintf(fp, "-DB%d\n", did_boot);

	for (p = family; p; p = p->next) {
		fprintf(fp, "REC%s\n", p->id);
		fprintf(fp, "LEV%s\n", p->rlevel);
		for (i = 0, val = p->flags; flags[i].mask; i++)
			if (val & flags[i].mask) {
				val &= ~flags[i].mask;
				fprintf(fp, "FL %s\n",flags[i].name);
			}
		fprintf(fp, "PID%d\n",p->pid);
		fprintf(fp, "EXS%u\n",p->exstat);
		for(i = 0; actions[i].act; i++)
			if (actions[i].act == p->action) {
				fprintf(fp, "AC %s\n", actions[i].name);
				break;
			}
		fprintf(fp, "CMD%s\n", p->process);
		fprintf(fp, "EOR\n");
	}
	fprintf(fp, "END\n");
	fclose(fp);
}

/*
 *	Read a string from a file descriptor.
 *	FIXME: why not use fgets() ?
 */
static int get_string(char *p, int size, FILE *f)
{
	int	c;

	while ((c = getc(f)) != EOF && c != '\n') {
		if (--size > 0)
			*p++ = c;
	}
	*p = '\0';
	return (c != EOF) && (size > 0);
}

/*
 *	Read trailing data from the state pipe until we see a newline.
 */
static int get_void(FILE *f)
{
	int	c;

	while ((c = getc(f)) != EOF && c != '\n')
		;

	return (c != EOF);
}

/*
 *	Read the next "command" from the state pipe.
 */
static int get_cmd(FILE *f)
{
	char	cmd[4] = "   ";
	int	i;

	if (fread(cmd, 1, sizeof(cmd) - 1, f) != sizeof(cmd) - 1)
		return C_EOF;

	for(i = 0; cmds[i].cmd && strcmp(cmds[i].name, cmd) != 0; i++)
		;
	return cmds[i].cmd;
}

/*
 *	Read a CHILD * from the state pipe.
 */
static CHILD *get_record(FILE *f)
{
	int	cmd;
	char	s[32];
	int	i;
	CHILD	*p;

	do {
		switch (cmd = get_cmd(f)) {
			case C_END:
				get_void(f);
				return NULL;
			case 0:
				get_void(f);
				break;
			case C_REC:
				break;
			case D_RUNLEVEL:
				fscanf(f, "%c\n", &runlevel);
				break;
			case D_THISLEVEL:
				fscanf(f, "%c\n", &thislevel);
				break;
			case D_PREVLEVEL:
				fscanf(f, "%c\n", &prevlevel);
				break;
			case D_GOTSIGN:
				fscanf(f, "%u\n", &got_signals);
				break;
			case D_WROTE_WTMP_REBOOT:
				fscanf(f, "%d\n", &wrote_wtmp_reboot);
				break;
			case D_WROTE_UTMP_REBOOT:
				fscanf(f, "%d\n", &wrote_utmp_reboot);
				break;
			case D_SLTIME:
				fscanf(f, "%d\n", &sltime);
				break;
			case D_DIDBOOT:
				fscanf(f, "%d\n", &did_boot);
				break;
			default:
				if (cmd > 0 || cmd == C_EOF) {
					oops_error = -1;
					return NULL;
				}
		}
	} while (cmd != C_REC);

	p = imalloc(sizeof(CHILD));
	get_string(p->id, sizeof(p->id), f);

	do switch(cmd = get_cmd(f)) {
		case 0:
		case C_EOR:
			get_void(f);
			break;
		case C_PID:
			fscanf(f, "%d\n", &(p->pid));
			break;
		case C_EXS:
			fscanf(f, "%u\n", &(p->exstat));
			break;
		case C_LEV:
			get_string(p->rlevel, sizeof(p->rlevel), f);
			break;
		case C_PROCESS:
			get_string(p->process, sizeof(p->process), f);
			break;
		case C_FLAG:
			get_string(s, sizeof(s), f);
			for(i = 0; flags[i].name; i++) {
				if (strcmp(flags[i].name,s) == 0)
					break;
			}
			p->flags |= flags[i].mask;
			break;
		case C_ACTION:
			get_string(s, sizeof(s), f);
			for(i = 0; actions[i].name; i++) {
				if (strcmp(actions[i].name, s) == 0)
					break;
			}
			p->action = actions[i].act ? actions[i].act : OFF;
			break;
		default:
			free(p);
			oops_error = -1;
			return NULL;
	} while( cmd != C_EOR);

	return p;
}

/*
 *	Read the complete state info from the state pipe.
 *	Returns 0 on success
 */
int receive_state(int fd)
{
	FILE	*f;
	char	old_version[256];
	CHILD	**pp;

	f = fdopen(fd, "r");

 	if (get_cmd(f) != C_VER)
		return -1;
	get_string(old_version, sizeof(old_version), f);
	oops_error = 0;
	for (pp = &family; (*pp = get_record(f)) != NULL; pp = &((*pp)->next))
		;
	fclose(f);
	return oops_error;
}

/*
 *	Set the process title.
 */
#ifdef __GNUC__
__attribute__ ((format (printf, 1, 2)))
#endif
static int setproctitle(char *fmt, ...)
{
	va_list ap;
	int len;
	char buf[256];

	buf[0] = 0;

	va_start(ap, fmt);
	len = vsnprintf(buf, sizeof(buf), fmt, ap);
	va_end(ap);

	if (maxproclen > 2) {
		memset(argv0, 0, maxproclen);
		strncpy(argv0, buf, maxproclen - 2);
	}

	return len;
}

/*
 *	Set console_dev to a working console.
 */
void console_init(void)
{
	int fd;
	int tried_devcons = 0;
	int tried_vtmaster = 0;
	char *s;

	if (user_console) {
		console_dev = user_console;
	} else if ((s = getenv("CONSOLE")) != NULL)
		console_dev = s;
	else {
		console_dev = CONSOLE;
		tried_devcons++;
	}

	while ((fd = open(console_dev, O_RDONLY|O_NONBLOCK)) < 0) {
		if (!tried_devcons) {
			tried_devcons++;
			console_dev = CONSOLE;
			continue;
		}
		if (!tried_vtmaster) {
			tried_vtmaster++;
			console_dev = VT_MASTER;
			continue;
		}
		break;
	}
	if (fd < 0)
		console_dev = "/dev/null";
	else
		close(fd);
}


/*
 *	Open the console with retries.
 */
int console_open(int mode)
{
	int f, fd = -1;
	int m;

	/*
	 *	Open device in nonblocking mode.
	 */
	m = mode | O_NONBLOCK;

	/*
	 *	Retry the open five times.
	 */
	for(f = 0; f < 5; f++)
		if ((fd = open(console_dev, m)) >= 0) break;

	if (fd < 0) return fd;

	/*
	 *	Set original flags.
	 */
	if (m != mode)
  		fcntl(fd, F_SETFL, mode);
	return fd;
}

/*
 *	We got a signal (HUP PWR WINCH ALRM INT)
 */
void signal_handler(int sig)
{
	ADDSET(got_signals, sig);
}

/*
 *	SIGCHLD: one of our children has died.
 */
void chld_handler()
{
	CHILD		*ch;
	int		pid, st;
	int		saved_errno = errno;

	/*
	 *	Find out which process(es) this was (were)
	 */
	while((pid = waitpid(-1, &st, WNOHANG)) != 0) {
		if (errno == ECHILD) break;
		for( ch = family; ch; ch = ch->next )
			if ( ch->pid == pid && (ch->flags & RUNNING) ) {
				INITDBG(L_VB,
					"chld_handler: marked %d as zombie",
					ch->pid);
				ADDSET(got_signals, SIGCHLD);
				ch->exstat = st;
				ch->flags |= ZOMBIE;
				if (ch->new) {
					ch->new->exstat = st;
					ch->new->flags |= ZOMBIE;
				}
				break;
			}
		if (ch == NULL)
			INITDBG(L_VB, "chld_handler: unknown child %d exited.",
				pid);
	}
	errno = saved_errno;
}

/*
 *	Linux ignores all signals sent to init when the
 *	SIG_DFL handler is installed. Therefore we must catch SIGTSTP
 *	and SIGCONT, or else they won't work....
 *
 *	The SIGCONT handler
 */
void cont_handler()
{
	got_cont = 1;
}

/*
 *	Fork and dump core in /.
 */
void coredump(void)
{
	static int		dumped = 0;
	struct rlimit		rlim;
	sigset_t		mask;

	if (dumped) return;
	dumped = 1;

	if (fork() != 0) return;

	sigfillset(&mask);
	sigprocmask(SIG_SETMASK, &mask, NULL);

	rlim.rlim_cur = RLIM_INFINITY;
	rlim.rlim_max = RLIM_INFINITY;
	setrlimit(RLIMIT_CORE, &rlim);
	chdir("/");

	signal(SIGSEGV, SIG_DFL);
	raise(SIGSEGV);
	sigdelset(&mask, SIGSEGV);
	sigprocmask(SIG_SETMASK, &mask, NULL);

	do_sleep(5);
	exit(0);
}

/*
 *	OOPS: segmentation violation!
 *	If we have the info, print where it occured.
 *	Then sleep 30 seconds and try to continue.
 */
#if defined(STACK_DEBUG) && defined(__linux__)
void segv_handler(int sig, struct sigcontext ctx)
{
	char	*p = "";
	int	saved_errno = errno;

	if ((void *)ctx.eip >= (void *)do_sleep &&
	    (void *)ctx.eip < (void *)main)
		p = " (code)";
	initlog(L_VB, "PANIC: segmentation violation at %p%s! "
		  "sleeping for 30 seconds.", (void *)ctx.eip, p);
	coredump();
	do_sleep(30);
	errno = saved_errno;
}
#else
void segv_handler()
{
	int	saved_errno = errno;

	initlog(L_VB,
		"PANIC: segmentation violation! sleeping for 30 seconds.");
	coredump();
	do_sleep(30);
	errno = saved_errno;
}
#endif

/*
 *	The SIGSTOP & SIGTSTP handler
 */
void stop_handler()
{
	int	saved_errno = errno;

	got_cont = 0;