init.c

sysvinit--linux系统下的init

	/*
	 *	Only BOOT processes may live in all levels
	 */
	if (ch->action != BOOT &&
	    strchr(ch->rlevel, runlevel) == NULL) {
		/*
		 *	Ondemand procedures live always,
		 *	except in single user
		 */
		if (runlevel == 'S' || !(ch->flags & DEMAND))
			ch->flags |= KILLME;
	}

	/*
	 *	Now, if this process may live note so in the new list
	 */
	if ((ch->flags & KILLME) == 0) {
		ch->new->flags  = ch->flags;
		ch->new->pid    = ch->pid;
		ch->new->exstat = ch->exstat;
		continue;
	}


	/*
	 *	Is this process still around?
	 */
	if ((ch->flags & RUNNING) == 0) {
		ch->flags &= ~KILLME;
		continue;
	}
	INITDBG(L_VB, "Killing \"%s\"", ch->process);
	switch(round) {
		case 0: /* Send TERM signal */
			if (talk)
				initlog(L_CO,
					"Sending processes the TERM signal");
			kill(-(ch->pid), SIGTERM);
			foundOne = 1;
			break;
		case 1: /* Send KILL signal and collect status */
			if (talk)
				initlog(L_CO,
					"Sending processes the KILL signal");
			kill(-(ch->pid), SIGKILL);
			break;
	}
	talk = 0;
	
    }
    /*
     *	See if we have to wait 5 seconds
     */
    if (foundOne && round == 0) {
	/*
	 *	Yup, but check every second if we still have children.
	 */
	for(f = 0; f < sltime; f++) {
		for(ch = family; ch; ch = ch->next) {
			if (!(ch->flags & KILLME)) continue;
			if ((ch->flags & RUNNING) && !(ch->flags & ZOMBIE))
				break;
		}
		if (ch == NULL) {
			/*
			 *	No running children, skip SIGKILL
			 */
			round = 1;
			foundOne = 0; /* Skip the sleep below. */
			break;
		}
		do_sleep(1);
	}
    }
  }

  /*
   *	Now give all processes the chance to die and collect exit statuses.
   */
  if (foundOne) do_sleep(1);
  for(ch = family; ch; ch = ch->next)
	if (ch->flags & KILLME) {
		if (!(ch->flags & ZOMBIE))
		    initlog(L_CO, "Pid %d [id %s] seems to hang", ch->pid,
				ch->id);
		else {
		    INITDBG(L_VB, "Updating utmp for pid %d [id %s]",
				ch->pid, ch->id);
		    ch->flags &= ~RUNNING;
		    if (ch->process[0] != '+')
		    	write_utmp_wtmp("", ch->id, ch->pid, DEAD_PROCESS, NULL);
		}
	}

  /*
   *	Both rounds done; clean up the list.
   */
  sigemptyset(&nmask);
  sigaddset(&nmask, SIGCHLD);
  sigprocmask(SIG_BLOCK, &nmask, &omask);
  for(ch = family; ch; ch = old) {
	old = ch->next;
	free(ch);
  }
  family = newFamily;
  for(ch = family; ch; ch = ch->next) ch->new = NULL;
  newFamily = NULL;
  sigprocmask(SIG_SETMASK, &omask, NULL);

#ifdef INITLVL
  /*
   *	Dispose of INITLVL file.
   */
  if (lstat(INITLVL, &st) >= 0 && S_ISLNK(st.st_mode)) {
	/*
	 *	INITLVL is a symbolic link, so just truncate the file.
	 */
	close(open(INITLVL, O_WRONLY|O_TRUNC));
  } else {
	/*
	 *	Delete INITLVL file.
	 */
  	unlink(INITLVL);
  }
#endif
#ifdef INITLVL2
  /*
   *	Dispose of INITLVL2 file.
   */
  if (lstat(INITLVL2, &st) >= 0 && S_ISLNK(st.st_mode)) {
	/*
	 *	INITLVL2 is a symbolic link, so just truncate the file.
	 */
	close(open(INITLVL2, O_WRONLY|O_TRUNC));
  } else {
	/*
	 *	Delete INITLVL2 file.
	 */
  	unlink(INITLVL2);
  }
#endif
}

/*
 *	Walk through the family list and start up children.
 *	The entries that do not belong here at all are removed
 *	from the list.
 */
void start_if_needed(void)
{
	CHILD *ch;		/* Pointer to child */
	int delete;		/* Delete this entry from list? */

	INITDBG(L_VB, "Checking for children to start");

	for(ch = family; ch; ch = ch->next) {

#if DEBUG
		if (ch->rlevel[0] == 'C') {
			INITDBG(L_VB, "%s: flags %d", ch->process, ch->flags);
		}
#endif

		/* Are we waiting for this process? Then quit here. */
		if (ch->flags & WAITING) break;

		/* Already running? OK, don't touch it */
		if (ch->flags & RUNNING) continue;

		/* See if we have to start it up */
		delete = 1;
		if (strchr(ch->rlevel, runlevel) ||
		    ((ch->flags & DEMAND) && !strchr("#*Ss", runlevel))) {
			startup(ch);
			delete = 0;
		}

		if (delete) {
			/* FIXME: is this OK? */
			ch->flags &= ~(RUNNING|WAITING);
			if (!ISPOWER(ch->action) && ch->action != KBREQUEST)
				ch->flags &= ~XECUTED;
			ch->pid = 0;
		} else
			/* Do we have to wait for this process? */
			if (ch->flags & WAITING) break;
	}
	/* Done. */
}

/*
 *	Ask the user on the console for a runlevel
 */
int ask_runlevel(void)
{
	const char	prompt[] = "\nEnter runlevel: ";
	char		buf[8];
	int		lvl = -1;
	int		fd;

	console_stty();
	fd = console_open(O_RDWR|O_NOCTTY);

	if (fd < 0) return('S');

	while(!strchr("0123456789S", lvl)) {
  		write(fd, prompt, sizeof(prompt) - 1);
		buf[0] = 0;
  		read(fd, buf, sizeof(buf));
  		if (buf[0] != 0 && (buf[1] == '\r' || buf[1] == '\n'))
			lvl = buf[0];
		if (islower(lvl)) lvl = toupper(lvl);
	}
	close(fd);
	return lvl;
}

/*
 *	Search the INITTAB file for the 'initdefault' field, with the default
 *	runlevel. If this fails, ask the user to supply a runlevel.
 */
int get_init_default(void)
{
	CHILD *ch;
	int lvl = -1;
	char *p;

	/*
	 *	Look for initdefault.
	 */
	for(ch = family; ch; ch = ch->next)
		if (ch->action == INITDEFAULT) {
			p = ch->rlevel;
			while(*p) {
				if (*p > lvl) lvl = *p;
				p++;
			}
			break;
		}
	/*
	 *	See if level is valid
	 */
	if (lvl > 0) {
		if (islower(lvl)) lvl = toupper(lvl);
		if (strchr("0123456789S", lvl) == NULL) {
			initlog(L_VB,
				"Initdefault level '%c' is invalid", lvl);
			lvl = 0;
		}
	}
	/*
	 *	Ask for runlevel on console if needed.
	 */
	if (lvl <= 0) lvl = ask_runlevel();

	/*
	 *	Log the fact that we have a runlevel now.
	 */
	return lvl;
}


/*
 *	We got signaled.
 *
 *	Do actions for the new level. If we are compatible with
 *	the "old" INITLVL and arg == 0, try to read the new
 *	runlevel from that file first.
 */
int read_level(int arg)
{
	CHILD		*ch;			/* Walk through list */
	unsigned char	foo = 'X';		/* Contents of INITLVL */
	int		ok = 1;
#ifdef INITLVL
	FILE		*fp;
	struct stat	stt;
	int		st;
#endif

	if (arg) foo = arg;

#ifdef INITLVL
	ok = 0;

	if (arg == 0) {
		fp = NULL;
		if (stat(INITLVL, &stt) != 0 || stt.st_size != 0L)
			fp = fopen(INITLVL, "r");
#ifdef INITLVL2
		if (fp == NULL &&
		    (stat(INITLVL2, &stt) != 0 || stt.st_size != 0L))
			fp = fopen(INITLVL2, "r");
#endif
		if (fp == NULL) {
			/* INITLVL file empty or not there - act as 'init q' */
			initlog(L_SY, "Re-reading inittab");
  			return(runlevel);
		}
		ok = fscanf(fp, "%c %d", &foo, &st);
		fclose(fp);
	} else {
		/* We go to the new runlevel passed as an argument. */
		foo = arg;
		ok = 1;
	}
	if (ok == 2) sltime = st;

#endif /* INITLVL */

	if (islower(foo)) foo = toupper(foo);
	if (ok < 1 || ok > 2 || strchr("QS0123456789ABCU", foo) == NULL) {
 		initlog(L_VB, "bad runlevel: %c", foo);
  		return runlevel;
	}

	/* Log this action */
	switch(foo) {
		case 'S':
  			initlog(L_VB, "Going single user");
			break;
		case 'Q':
			initlog(L_SY, "Re-reading inittab");
			break;
		case 'A':
		case 'B':
		case 'C':
			initlog(L_SY,
				"Activating demand-procedures for '%c'", foo);
			break;
		case 'U':
			initlog(L_SY, "Trying to re-exec init");
			return 'U';
		default:
		  	initlog(L_VB, "Switching to runlevel: %c", foo);
	}

	if (foo == 'Q') return runlevel;

	/* Check if this is a runlevel a, b or c */
	if (strchr("ABC", foo)) {
		if (runlevel == 'S') return(runlevel);

		/* Read inittab again first! */
		read_inittab();

  		/* Mark those special tasks */
		for(ch = family; ch; ch = ch->next)
			if (strchr(ch->rlevel, foo) != NULL ||
			    strchr(ch->rlevel, tolower(foo)) != NULL) {
				ch->flags |= DEMAND;
				ch->flags &= ~XECUTED;
				INITDBG(L_VB,
					"Marking (%s) as ondemand, flags %d",
					ch->id, ch->flags);
			}
  		return runlevel;
	}

	/* Store both the old and the new runlevel. */
	write_utmp_wtmp("runlevel", "~~", foo + 256*runlevel, RUN_LVL, "~");
	thislevel = foo;
	prevlevel = runlevel;
	return foo;
}


/*
 *	This procedure is called after every signal (SIGHUP, SIGALRM..)
 *
 *	Only clear the 'failing' flag if the process is sleeping
 *	longer than 5 minutes, or inittab was read again due
 *	to user interaction.
 */
void fail_check(void)
{
	CHILD	*ch;			/* Pointer to child structure */
	time_t	t;			/* System time */
	time_t	next_alarm = 0;		/* When to set next alarm */

	time(&t);

	for(ch = family; ch; ch = ch->next) {

		if (ch->flags & FAILING) {
			/* Can we free this sucker? */
			if (ch->tm + SLEEPTIME < t) {
				ch->flags &= ~FAILING;
				ch->count = 0;
				ch->tm = 0;
			} else {
				/* No, we'll look again later */
				if (next_alarm == 0 ||
				    ch->tm + SLEEPTIME > next_alarm)
					next_alarm = ch->tm + SLEEPTIME;
			}
		}
	}
	if (next_alarm) {
		next_alarm -= t;
		if (next_alarm < 1) next_alarm = 1;
		alarm(next_alarm);
	}
}

/* Set all 'Fail' timers to 0 */
void fail_cancel(void)
{
	CHILD *ch;

	for(ch = family; ch; ch = ch->next) {
		ch->count = 0;
		ch->tm = 0;
		ch->flags &= ~FAILING;
	}
}

/*
 *	Start up powerfail entries.
 */
void do_power_fail(int pwrstat)
{
	CHILD *ch;

	/*
	 *	Tell powerwait & powerfail entries to start up
	 */
	for (ch = family; ch; ch = ch->next) {
		if (pwrstat == 'O') {
			/*
		 	 *	The power is OK again.
		 	 */
			if (ch->action == POWEROKWAIT)
				ch->flags &= ~XECUTED;
		} else if (pwrstat == 'L') {
			/*
			 *	Low battery, shut down now.
			 */
			if (ch->action == POWERFAILNOW)
				ch->flags &= ~XECUTED;
		} else {
			/*
			 *	Power is failing, shutdown imminent
			 */
			if (ch->action == POWERFAIL || ch->action == POWERWAIT)
				ch->flags &= ~XECUTED;
		}
	}
}

/*
 *	Check for state-pipe presence
 */
int check_pipe(int fd)
{
	struct timeval	t;
	fd_set		s;
	char		signature[8];

	FD_ZERO(&s);
	FD_SET(fd, &s);
	t.tv_sec = t.tv_usec = 0;

	if (select(fd+1, &s, NULL, NULL, &t) != 1)
		return 0;
	if (read(fd, signature, 8) != 8)
		 return 0;
	return strncmp(Signature, signature, 8) == 0;
}

/*
 *	 Make a state-pipe.
 */
int make_pipe(int fd)
{
	int fds[2];

	pipe(fds);
	dup2(fds[0], fd);
	close(fds[0]);
	fcntl(fds[1], F_SETFD, 1);
	fcntl(fd, F_SETFD, 0);
	write(fds[1], Signature, 8);

	return fds[1];
}

/*
 *	Attempt to re-exec.
 */
void re_exec(void)
{
	CHILD		*ch;
	sigset_t	mask, oldset;
	pid_t		pid;
	char		**env;
	int		fd;

	if (strchr("S12345",runlevel) == NULL)
		return;

	/*
	 *	Reset the alarm, and block all signals.
	 */
	alarm(0);
	sigfillset(&mask);
	sigprocmask(SIG_BLOCK, &mask, &oldset);

	/*
	 *	construct a pipe fd --> STATE_PIPE and write a signature
	 */
	fd = make_pipe(STATE_PIPE);

	/* 
	 * It's a backup day today, so I'm pissed off.  Being a BOFH, however, 
	 * does have it's advantages...
	 */
	fail_cancel();
	close(pipe_fd);
	pipe_fd = -1;
	DELSET(got_signals, SIGCHLD);
	DELSET(got_signals, SIGHUP);
	DELSET(got_signals, SIGUSR1);

	/*
	 *	That should be cleaned.
	 */
	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 ((pid = fork()) == 0) {
		/*
		 *	Child sends state information to the parent.
		 */
		send_state(fd);
		exit(0);
	}

	/*
	 *	The existing init process execs a new init binary.
	 */
	env = init_buildenv(0);
	execl(myname, myname, "--init", NULL, env);

	/*
	 *	We shouldn't be here, something failed. 
	 *	Bitch, close the state pipe, unblock signals and return.
	 */
	close(fd);
	close(STATE_PIPE);
	sigprocmask(SIG_SETMASK, &oldset, NULL);
	init_freeenv(env);
	initlog(L_CO, "Attempt to re-exec failed");
}


/*
 *	We got a change runlevel request through the
 *	init.fifo. Process it.
 */
void fifo_new_level(int level)
{
#if CHANGE_WAIT
	CHILD	*ch;
#endif
	int	oldlevel;

	if (level == runlevel) return;

#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;
		runlevel = read_level(level);
		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);
		}
	}
}


/*
 *	Set/unset environment variables. The variables are
 *	encoded as KEY=VAL\0KEY=VAL\0\0. With "=VAL" it means
 *	setenv, without it means unsetenv.
 */
void initcmd_setenv(char *data, int size)
{
	char		*env, *p, *e, *eq;
	int		i, sz;

	e = data + size;

	while (*data && data < e) {
		eq = NULL;
		for (p = data; *p && p < e; p++)
			if (*p == '=') eq = p;
		if (*p) break;
		env = data;
		data = ++p;

		sz = eq ? (eq - env) : (p - env);

		/*initlog(L_SY, "init_setenv: %s, %s, %d", env, eq, sz);*/

		/*
		 *	We only allow INIT_* to be set.
		 */
		if (strncmp(env, "INIT_", 5) != 0)
			continue;

		/* Free existing vars. */
		for (i = 0; i < NR_EXTRA_ENV; i++) {
			if (extra_env[i] == NULL) continue;
			if (!strncmp(extra_env[i], env, sz) &&
			    extra_env[i][sz] == '=') {
				free(extra_env[i]);
				extra_env[i] = NULL;
			}
		}

		/* Set new vars if needed. */
		if (eq == NULL) continue;
		for (i = 0; i < NR_EXTRA_ENV; i++) {
			if (extra_env[i] == NULL) {
				extra_env[i] = istrdup(env);
				break;
			}
		}
	}
}


/*
 *	Read from the init FIFO. Processes like telnetd and rlogind can
 *	ask us to create login processes on their behalf.
 *
 *	FIXME:	this needs to be finished. NOT that it is buggy, but we need
 *		to add the telnetd/rlogind stuff so people can start using it.
 *		Maybe move to using an AF_UNIX socket so we can use
 *		the 2.2 kernel credential stuff to see who we're talking to.
 *	
 */
void check_init_fifo(void)
{
  struct init_request	request;
  struct timeval	tv;
  struct stat		st, st2;
  fd_set		fds;
  int			n;