init.c

sysvinit--linux系统下的init

  int			quit = 0;

  /*
   *	First, try to create /dev/initctl if not present.
   */
  if (stat(INIT_FIFO, &st2) < 0 && errno == ENOENT)
	(void)mkfifo(INIT_FIFO, 0600);

  /*
   *	If /dev/initctl is open, stat the file to see if it
   *	is still the _same_ inode.
   */
  if (pipe_fd >= 0) {
	fstat(pipe_fd, &st);
	if (stat(INIT_FIFO, &st2) < 0 ||
	    st.st_dev != st2.st_dev ||
	    st.st_ino != st2.st_ino) {
		close(pipe_fd);
		pipe_fd = -1;
	}
  }

  /*
   *	Now finally try to open /dev/initctl
   */
  if (pipe_fd < 0) {
	if ((pipe_fd = open(INIT_FIFO, O_RDWR|O_NONBLOCK)) >= 0) {
		fstat(pipe_fd, &st);
		if (!S_ISFIFO(st.st_mode)) {
			initlog(L_VB, "%s is not a fifo", INIT_FIFO);
			close(pipe_fd);
			pipe_fd = -1;
		}
	}
	if (pipe_fd >= 0) {
		/*
		 *	Don't use fd's 0, 1 or 2.
		 */
		(void) dup2(pipe_fd, PIPE_FD);
		close(pipe_fd);
		pipe_fd = PIPE_FD;

		/*
		 *	Return to caller - we'll be back later.
		 */
	}
  }

  /* Wait for data to appear, _if_ the pipe was opened. */
  if (pipe_fd >= 0) while(!quit) {

	/* Do select, return on EINTR. */
	FD_ZERO(&fds);
	FD_SET(pipe_fd, &fds);
	tv.tv_sec = 5;
	tv.tv_usec = 0;
	n = select(pipe_fd + 1, &fds, NULL, NULL, &tv);
	if (n <= 0) {
		if (n == 0 || errno == EINTR) return;
		continue;
	}

	/* Read the data, return on EINTR. */
	n = read(pipe_fd, &request, sizeof(request));
	if (n == 0) {
		/*
		 *	End of file. This can't happen under Linux (because
		 *	the pipe is opened O_RDWR - see select() in the
		 *	kernel) but you never know...
		 */
		close(pipe_fd);
		pipe_fd = -1;
		return;
	}
	if (n <= 0) {
		if (errno == EINTR) return;
		initlog(L_VB, "error reading initrequest");
		continue;
	}

	/*
	 *	This is a convenient point to also try to
	 *	find the console device or check if it changed.
	 */
	console_init();

	/*
	 *	Process request.
	 */
	if (request.magic != INIT_MAGIC || n != sizeof(request)) {
		initlog(L_VB, "got bogus initrequest");
		continue;
	}
	switch(request.cmd) {
		case INIT_CMD_RUNLVL:
			sltime = request.sleeptime;
			fifo_new_level(request.runlevel);
			quit = 1;
			break;
		case INIT_CMD_POWERFAIL:
			sltime = request.sleeptime;
			do_power_fail('F');
			quit = 1;
			break;
		case INIT_CMD_POWERFAILNOW:
			sltime = request.sleeptime;
			do_power_fail('L');
			quit = 1;
			break;
		case INIT_CMD_POWEROK:
			sltime = request.sleeptime;
			do_power_fail('O');
			quit = 1;
			break;
		case INIT_CMD_SETENV:
			initcmd_setenv(request.i.data, sizeof(request.i.data));
			break;
		case INIT_CMD_CHANGECONS:
			if (user_console) {
				free(user_console);
				user_console = NULL;
			}
			if (!request.i.bsd.reserved[0])
				user_console = NULL;
			else
				user_console = strdup(request.i.bsd.reserved);
			console_init();
			quit = 1;
			break;
		default:
			initlog(L_VB, "got unimplemented initrequest.");
			break;
	}
  }

  /*
   *	We come here if the pipe couldn't be opened.
   */
  if (pipe_fd < 0) pause();

}


/*
 *	This function is used in the transition
 *	sysinit (-> single user) boot -> multi-user.
 */
void boot_transitions()
{
  CHILD		*ch;
  static int	newlevel = 0;
  static int	warn = 1;
  int		loglevel;
  int		oldlevel;

  /* Check if there is something to wait for! */
  for( ch = family; ch; ch = ch->next )
	if ((ch->flags & RUNNING) && ch->action != BOOT) break;
     
  if (ch == NULL) {
	/* No processes left in this level, proceed to next level. */
	loglevel = -1;
	oldlevel = 'N';
	switch(runlevel) {
		case '#': /* SYSINIT -> BOOT */
			INITDBG(L_VB, "SYSINIT -> BOOT");

			/* Write a boot record. */
			wrote_utmp_reboot = 0;
			wrote_wtmp_reboot = 0;
			write_utmp_wtmp("reboot", "~~", 0, BOOT_TIME, "~");

  			/* Get our run level */
  			newlevel = dfl_level ? dfl_level : get_init_default();
			if (newlevel == 'S') {
				runlevel = newlevel;
				/* Not really 'S' but show anyway. */
				setproctitle("init [S]");
			} else
				runlevel = '*';
			break;
		case '*': /* BOOT -> NORMAL */
			INITDBG(L_VB, "BOOT -> NORMAL");
			if (runlevel != newlevel)
				loglevel = newlevel;
			runlevel = newlevel;
			did_boot = 1;
			warn = 1;
			break;
		case 'S': /* Ended SU mode */
		case 's':
			INITDBG(L_VB, "END SU MODE");
			newlevel = get_init_default();
			if (!did_boot && newlevel != 'S')
				runlevel = '*';
			else {
				if (runlevel != newlevel)
					loglevel = newlevel;
				runlevel = newlevel;
				oldlevel = 'S';
			}
			warn = 1;
			for(ch = family; ch; ch = ch->next)
			    if (strcmp(ch->rlevel, "S") == 0)
				ch->flags &= ~(FAILING|WAITING|XECUTED);
			break;
		default:
			if (warn)
			  initlog(L_VB,
				"no more processes left in this runlevel");
			warn = 0;
			loglevel = -1;
			if (got_signals == 0)
				check_init_fifo();
			break;
	}
	if (loglevel > 0) {
		initlog(L_VB, "Entering runlevel: %c", runlevel);
		write_utmp_wtmp("runlevel", "~~", runlevel + 256 * oldlevel, RUN_LVL, "~");
		thislevel = runlevel;
		prevlevel = oldlevel;
		setproctitle("init [%c]", runlevel);
	}
  }
}

/*
 *	Init got hit by a signal. See which signal it is,
 *	and act accordingly.
 */
void process_signals()
{
  CHILD		*ch;
  int		pwrstat;
  int		oldlevel;
  int		fd;
  char		c;

  if (ISMEMBER(got_signals, SIGPWR)) {
	INITDBG(L_VB, "got SIGPWR");
	/* See _what_ kind of SIGPWR this is. */
	pwrstat = 0;
	if ((fd = open(PWRSTAT, O_RDONLY)) >= 0) {
		c = 0;
		read(fd, &c, 1);
		pwrstat = c;
		close(fd);
		unlink(PWRSTAT);
	}
	do_power_fail(pwrstat);
	DELSET(got_signals, SIGPWR);
  }

  if (ISMEMBER(got_signals, SIGINT)) {
	INITDBG(L_VB, "got SIGINT");
	/* Tell ctrlaltdel entry to start up */
	for(ch = family; ch; ch = ch->next)
		if (ch->action == CTRLALTDEL)
			ch->flags &= ~XECUTED;
	DELSET(got_signals, SIGINT);
  }

  if (ISMEMBER(got_signals, SIGWINCH)) {
	INITDBG(L_VB, "got SIGWINCH");
	/* Tell kbrequest entry to start up */
	for(ch = family; ch; ch = ch->next)
		if (ch->action == KBREQUEST)
			ch->flags &= ~XECUTED;
	DELSET(got_signals, SIGWINCH);
  }

  if (ISMEMBER(got_signals, SIGALRM)) {
	INITDBG(L_VB, "got SIGALRM");
	/* The timer went off: check it out */
	DELSET(got_signals, SIGALRM);
  }

  if (ISMEMBER(got_signals, SIGCHLD)) {
	INITDBG(L_VB, "got SIGCHLD");
	/* First set flag to 0 */
	DELSET(got_signals, SIGCHLD);

	/* See which child this was */
	for(ch = family; ch; ch = ch->next)
	    if (ch->flags & ZOMBIE) {
		INITDBG(L_VB, "Child died, PID= %d", ch->pid);
		ch->flags &= ~(RUNNING|ZOMBIE|WAITING);
		if (ch->process[0] != '+')
			write_utmp_wtmp("", ch->id, ch->pid, DEAD_PROCESS, NULL);
	    }

  }

  if (ISMEMBER(got_signals, SIGHUP)) {
	INITDBG(L_VB, "got SIGHUP");
#if CHANGE_WAIT
	/* Are we waiting for a child? */
	for(ch = family; ch; ch = ch->next)
		if (ch->flags & WAITING) break;
	if (ch == NULL)
#endif
	{
		/* We need to go into a new runlevel */
		oldlevel = runlevel;
#ifdef INITLVL
		runlevel = read_level(0);
#endif
		if (runlevel == 'U') {
			runlevel = oldlevel;
			re_exec();
		} else {
			if (oldlevel != 'S' && runlevel == 'S') console_stty();
			if (runlevel == '6' || runlevel == '0' ||
			    runlevel == '1') console_stty();
			read_inittab();
			fail_cancel();
			setproctitle("init [%c]", runlevel);
			DELSET(got_signals, SIGHUP);
		}
	}
  }
  if (ISMEMBER(got_signals, SIGUSR1)) {
	/*
	 *	SIGUSR1 means close and reopen /dev/initctl
	 */
	INITDBG(L_VB, "got SIGUSR1");
	close(pipe_fd);
	pipe_fd = -1;
	DELSET(got_signals, SIGUSR1);
  }
}

/*
 *	The main loop
 */ 
int init_main()
{
  CHILD			*ch;
  struct sigaction	sa;
  sigset_t		sgt;
  pid_t			rc;
  int			f, st;

  if (!reload) {
  
#if INITDEBUG
	/*
	 * Fork so we can debug the init process.
	 */
	if ((f = fork()) > 0) {
		static const char killmsg[] = "PRNT: init killed.\r\n";
		pid_t rc;

		while((rc = wait(&st)) != f)
			if (rc < 0 && errno == ECHILD)
				break;
		write(1, killmsg, sizeof(killmsg) - 1);
		while(1) pause();
	}
#endif

#ifdef __linux__
	/*
	 *	Tell the kernel to send us SIGINT when CTRL-ALT-DEL
	 *	is pressed, and that we want to handle keyboard signals.
	 */
	init_reboot(BMAGIC_SOFT);
	if ((f = open(VT_MASTER, O_RDWR | O_NOCTTY)) >= 0) {
		(void) ioctl(f, KDSIGACCEPT, SIGWINCH);
		close(f);
	} else
		(void) ioctl(0, KDSIGACCEPT, SIGWINCH);
#endif

	/*
	 *	Ignore all signals.
	 */
	for(f = 1; f <= NSIG; f++)
		SETSIG(sa, f, SIG_IGN, SA_RESTART);
  }

  SETSIG(sa, SIGALRM,  signal_handler, 0);
  SETSIG(sa, SIGHUP,   signal_handler, 0);
  SETSIG(sa, SIGINT,   signal_handler, 0);
  SETSIG(sa, SIGCHLD,  chld_handler, SA_RESTART);
  SETSIG(sa, SIGPWR,   signal_handler, 0);
  SETSIG(sa, SIGWINCH, signal_handler, 0);
  SETSIG(sa, SIGUSR1,  signal_handler, 0);
  SETSIG(sa, SIGSTOP,  stop_handler, SA_RESTART);
  SETSIG(sa, SIGTSTP,  stop_handler, SA_RESTART);
  SETSIG(sa, SIGCONT,  cont_handler, SA_RESTART);
  SETSIG(sa, SIGSEGV,  (void (*)(int))segv_handler, SA_RESTART);

  console_init();

  if (!reload) {

  	/* Close whatever files are open, and reset the console. */
	close(0);
	close(1);
	close(2);
  	console_stty();
  	setsid();

  	/*
	 *	Set default PATH variable.
	 */
  	putenv(PATH_DFL);

  	/*
	 *	Initialize /var/run/utmp (only works if /var is on
	 *	root and mounted rw)
	 */
  	(void) close(open(UTMP_FILE, O_WRONLY|O_CREAT|O_TRUNC, 0644));

  	/*
	 *	Say hello to the world
	 */
  	initlog(L_CO, bootmsg, "booting");

  	/*
	 *	See if we have to start an emergency shell.
	 */
	if (emerg_shell) {
		SETSIG(sa, SIGCHLD, SIG_DFL, SA_RESTART);
		if (spawn(&ch_emerg, &f) > 0) {
			while((rc = wait(&st)) != f)
				if (rc < 0 && errno == ECHILD)
					break;
		}
  		SETSIG(sa, SIGCHLD,  chld_handler, SA_RESTART);
  	}

  	/*
	 *	Start normal boot procedure.
	 */
  	runlevel = '#';
  	read_inittab();
  
  } else {
	/*
	 *	Restart: unblock signals and let the show go on
	 */
	initlog(L_CO, bootmsg, "reloading");
	sigfillset(&sgt);
	sigprocmask(SIG_UNBLOCK, &sgt, NULL);
  }
  start_if_needed();

  while(1) {

     /* See if we need to make the boot transitions. */
     boot_transitions();
     INITDBG(L_VB, "init_main: waiting..");

     /* Check if there are processes to be waited on. */
     for(ch = family; ch; ch = ch->next)
	if ((ch->flags & RUNNING) && ch->action != BOOT) break;

#if CHANGE_WAIT
     /* Wait until we get hit by some signal. */
     while (ch != NULL && got_signals == 0) {
	if (ISMEMBER(got_signals, SIGHUP)) {
		/* See if there are processes to be waited on. */
		for(ch = family; ch; ch = ch->next)
			if (ch->flags & WAITING) break;
	}
	if (ch != NULL) check_init_fifo();
     }
#else /* CHANGE_WAIT */
     if (ch != NULL && got_signals == 0) check_init_fifo();
#endif /* CHANGE_WAIT */

     /* Check the 'failing' flags */
     fail_check();

     /* Process any signals. */
     process_signals();

     /* See what we need to start up (again) */
     start_if_needed();
  }
  /*NOTREACHED*/
}

/*
 * Tell the user about the syntax we expect.
 */
void usage(char *s)
{
	fprintf(stderr, "Usage: %s 0123456SsQqAaBbCcUu\n", s);
	exit(1);
}

int telinit(char *progname, int argc, char **argv)
{
#ifdef TELINIT_USES_INITLVL
	FILE			*fp;
#endif
	struct init_request	request;
	struct sigaction	sa;
	int			f, fd, l;
	char			*env = NULL;

	memset(&request, 0, sizeof(request));
	request.magic     = INIT_MAGIC;

	while ((f = getopt(argc, argv, "t:e:")) != EOF) switch(f) {
		case 't':
			sltime = atoi(optarg);
			break;
		case 'e':
			if (env == NULL)
				env = request.i.data;
			l = strlen(optarg);
			if (env + l + 2 > request.i.data + sizeof(request.i.data)) {
				fprintf(stderr, "%s: -e option data "
					"too large\n", progname);
				exit(1);
			}
			memcpy(env, optarg, l);
			env += l;
			*env++ = 0;
			break;
		default:
			usage(progname);
			break;
	}

	if (env) *env++ = 0;

	if (env) {
		if (argc != optind)
			usage(progname);
		request.cmd = INIT_CMD_SETENV;
	} else {
		if (argc - optind != 1 || strlen(argv[optind]) != 1)
			usage(progname);
		if (!strchr("0123456789SsQqAaBbCcUu", argv[optind][0]))
			usage(progname);
		request.cmd = INIT_CMD_RUNLVL;
		request.runlevel  = env ? 0 : argv[optind][0];
		request.sleeptime = sltime;
	}

	/* Open the fifo and write a command. */
	/* Make sure we don't hang on opening /dev/initctl */
	SETSIG(sa, SIGALRM, signal_handler, 0);
	alarm(3);
	if ((fd = open(INIT_FIFO, O_WRONLY)) >= 0 &&
	    write(fd, &request, sizeof(request)) == sizeof(request)) {
		close(fd);
		alarm(0);
		return 0;
	}

#ifdef TELINIT_USES_INITLVL
	if (request.cmd == INIT_CMD_RUNLVL) {
		/* Fallthrough to the old method. */

		/* Now write the new runlevel. */
		if ((fp = fopen(INITLVL, "w")) == NULL) {
			fprintf(stderr, "%s: cannot create %s\n",
				progname, INITLVL);
			exit(1);
		}
		fprintf(fp, "%s %d", argv[optind], sltime);
		fclose(fp);

		/* And tell init about the pending runlevel change. */
		if (kill(INITPID, SIGHUP) < 0) perror(progname);

		return 0;
	}
#endif

	fprintf(stderr, "%s: ", progname);
	if (ISMEMBER(got_signals, SIGALRM)) {
		fprintf(stderr, "timeout opening/writing control channel %s\n",
			INIT_FIFO);
	} else {
		perror(INIT_FIFO);
	}
	return 1;
}

/*
 * Main entry for init and telinit.
 */
int main(int argc, char **argv)
{
	char			*p;
	int			f;
	int			isinit;

	/* Get my own name */
	if ((p = strrchr(argv[0], '/')) != NULL)
  		p++;
	else
  		p = argv[0];
	umask(022);

	/* Quick check */
	if (geteuid() != 0) {
		fprintf(stderr, "%s: must be superuser.\n", p);
		exit(1);
	}

	/*
	 *	Is this telinit or init ?
	 */
	isinit = (getpid() == 1);
	for (f = 1; f < argc; f++) {
		if (!strcmp(argv[f], "-i") || !strcmp(argv[f], "--init"))
			isinit = 1;
			break;
	}
	if (!isinit) exit(telinit(p, argc, argv));

	/*
	 *	Check for re-exec
	 */ 	
	if (check_pipe(STATE_PIPE)) {

		receive_state(STATE_PIPE);

		myname = istrdup(argv[0]);
		argv0 = argv[0];
		maxproclen = 0;
		for (f = 0; f < argc; f++)
			maxproclen += strlen(argv[f]) + 1;
		reload = 1;
		setproctitle("init [%c]",runlevel);

		init_main();
	}

  	/* Check command line arguments */
	maxproclen = strlen(argv[0]) + 1;
  	for(f = 1; f < argc; f++) {
		if (!strcmp(argv[f], "single") || !strcmp(argv[f], "-s"))
			dfl_level = 'S';
		else if (!strcmp(argv[f], "-a") || !strcmp(argv[f], "auto"))
			putenv("AUTOBOOT=YES");
		else if (!strcmp(argv[f], "-b") || !strcmp(argv[f],"emergency"))
			emerg_shell = 1;
		else if (!strcmp(argv[f], "-z")) {
			/* Ignore -z xxx */
			if (argv[f + 1]) f++;
		} else if (strchr("0123456789sS", argv[f][0])
			&& strlen(argv[f]) == 1)
			dfl_level = argv[f][0];
		/* "init u" in the very beginning makes no sense */
		if (dfl_level == 's') dfl_level = 'S';
		maxproclen += strlen(argv[f]) + 1;
	}

	/* Start booting. */
	argv0 = argv[0];
	argv[1] = NULL;
	setproctitle("init boot");
	init_main(dfl_level);

	/*NOTREACHED*/
	return 0;
}