init.c

早期freebsd实现

			if (errno == EINTR)
				continue;
			warning("wait for single-user shell failed: %m; restarting");
			return (state_func_t) single_user;
		}
		if (wpid == pid && WIFSTOPPED(status)) {
			warning("init: shell stopped, restarting\n");
			kill(pid, SIGCONT);
			wpid = -1;
		}
	} while (wpid != pid && !requested_transition);

	if (requested_transition)
		return (state_func_t) requested_transition;

	if (!WIFEXITED(status)) {
		if (WTERMSIG(status) == SIGKILL) { 
			/* 
			 *  reboot(8) killed shell? 
			 */
			warning("single user shell terminated.");
			sleep(STALL_TIMEOUT);
			_exit(0);
		} else {	
			warning("single user shell terminated, restarting");
			return (state_func_t) single_user;
		}
	}

	runcom_mode = FASTBOOT;
	return (state_func_t) runcom;
}

/*
 * Run the system startup script.
 */
state_func_t
runcom()
{
	pid_t pid, wpid;
	int status;
	char *argv[4];
	struct sigaction sa;

	if ((pid = fork()) == 0) {
		sigemptyset(&sa.sa_mask);
		sa.sa_flags = 0;
		sa.sa_handler = SIG_IGN;
		(void) sigaction(SIGTSTP, &sa, (struct sigaction *)0);
		(void) sigaction(SIGHUP, &sa, (struct sigaction *)0);

		setctty(_PATH_CONSOLE);

		argv[0] = "sh";
		argv[1] = _PATH_RUNCOM;
		argv[2] = runcom_mode == AUTOBOOT ? "autoboot" : 0;
		argv[3] = 0;

		sigprocmask(SIG_SETMASK, &sa.sa_mask, (sigset_t *) 0);

		execv(_PATH_BSHELL, argv);
		stall("can't exec %s for %s: %m", _PATH_BSHELL, _PATH_RUNCOM);
		_exit(1);	/* force single user mode */
	}

	if (pid == -1) {
		emergency("can't fork for %s on %s: %m",
			_PATH_BSHELL, _PATH_RUNCOM);
		while (waitpid(-1, (int *) 0, WNOHANG) > 0)
			continue;
		sleep(STALL_TIMEOUT);
		return (state_func_t) single_user;
	}

	/*
	 * Copied from single_user().  This is a bit paranoid.
	 */
	do {
		if ((wpid = waitpid(-1, &status, WUNTRACED)) != -1)
			collect_child(wpid);
		if (wpid == -1) {
			if (errno == EINTR)
				continue;
			warning("wait for %s on %s failed: %m; going to single user mode",
				_PATH_BSHELL, _PATH_RUNCOM);
			return (state_func_t) single_user;
		}
		if (wpid == pid && WIFSTOPPED(status)) {
			warning("init: %s on %s stopped, restarting\n",
				_PATH_BSHELL, _PATH_RUNCOM);
			kill(pid, SIGCONT);
			wpid = -1;
		}
	} while (wpid != pid);

	if (WIFSIGNALED(status) && WTERMSIG(status) == SIGTERM &&
	    requested_transition == catatonia) {
		/* /etc/rc executed /sbin/reboot; wait for the end quietly */
		sigset_t s;

		sigfillset(&s);
		for (;;)
			sigsuspend(&s);
	}

	if (!WIFEXITED(status)) {
		warning("%s on %s terminated abnormally, going to single user mode",
			_PATH_BSHELL, _PATH_RUNCOM);
		return (state_func_t) single_user;
	}

	if (WEXITSTATUS(status))
		return (state_func_t) single_user;

	runcom_mode = AUTOBOOT;		/* the default */
	/* NB: should send a message to the session logger to avoid blocking. */
	logwtmp("~", "reboot", "");
	return (state_func_t) read_ttys;
}

/*
 * Open the session database.
 *
 * NB: We could pass in the size here; is it necessary?
 */
int
start_session_db()
{
	if (session_db && (*session_db->close)(session_db))
		emergency("session database close: %s", strerror(errno));
	if ((session_db = dbopen(NULL, O_RDWR, 0, DB_HASH, NULL)) == 0) {
		emergency("session database open: %s", strerror(errno));
		return (1);
	}
	return (0);
		
}

/*
 * Add a new login session.
 */
void
add_session(sp)
	session_t *sp;
{
	DBT key;
	DBT data;

	key.data = &sp->se_process;
	key.size = sizeof sp->se_process;
	data.data = &sp;
	data.size = sizeof sp;

	if ((*session_db->put)(session_db, &key, &data, 0))
		emergency("insert %d: %s", sp->se_process, strerror(errno));
}

/*
 * Delete an old login session.
 */
void
del_session(sp)
	session_t *sp;
{
	DBT key;

	key.data = &sp->se_process;
	key.size = sizeof sp->se_process;

	if ((*session_db->del)(session_db, &key, 0))
		emergency("delete %d: %s", sp->se_process, strerror(errno));
}

/*
 * Look up a login session by pid.
 */
session_t *
#ifdef __STDC__
find_session(pid_t pid)
#else
find_session(pid)
	pid_t pid;
#endif
{
	DBT key;
	DBT data;
	session_t *ret;

	key.data = &pid;
	key.size = sizeof pid;
	if ((*session_db->get)(session_db, &key, &data, 0) != 0)
		return 0;
	bcopy(data.data, (char *)&ret, sizeof(ret));
	return ret;
}

/*
 * Construct an argument vector from a command line.
 */
char **
construct_argv(command)
	char *command;
{
	register int argc = 0;
	register char **argv = (char **) malloc(((strlen(command) + 1) / 2 + 1)
						* sizeof (char *));
	static const char separators[] = " \t";

	if ((argv[argc++] = strtok(command, separators)) == 0)
		return 0;
	while (argv[argc++] = strtok((char *) 0, separators))
		continue;
	return argv;
}

/*
 * Deallocate a session descriptor.
 */
void
free_session(sp)
	register session_t *sp;
{
	free(sp->se_device);
	if (sp->se_getty) {
		free(sp->se_getty);
		free(sp->se_getty_argv);
	}
	if (sp->se_window) {
		free(sp->se_window);
		free(sp->se_window_argv);
	}
	free(sp);
}

/*
 * Allocate a new session descriptor.
 */
session_t *
new_session(sprev, session_index, typ)
	session_t *sprev;
	int session_index;
	register struct ttyent *typ;
{
	register session_t *sp;

	if ((typ->ty_status & TTY_ON) == 0 ||
	    typ->ty_name == 0 ||
	    typ->ty_getty == 0)
		return 0;

	sp = (session_t *) malloc(sizeof (session_t));
	bzero(sp, sizeof *sp);

	sp->se_index = session_index;

	sp->se_device = malloc(sizeof(_PATH_DEV) + strlen(typ->ty_name));
	(void) sprintf(sp->se_device, "%s%s", _PATH_DEV, typ->ty_name);

	if (setupargv(sp, typ) == 0) {
		free_session(sp);
		return (0);
	}

	sp->se_next = 0;
	if (sprev == 0) {
		sessions = sp;
		sp->se_prev = 0;
	} else {
		sprev->se_next = sp;
		sp->se_prev = sprev;
	}

	return sp;
}

/*
 * Calculate getty and if useful window argv vectors.
 */
int
setupargv(sp, typ)
	session_t *sp;
	struct ttyent *typ;
{

	if (sp->se_getty) {
		free(sp->se_getty);
		free(sp->se_getty_argv);
	}
	sp->se_getty = malloc(strlen(typ->ty_getty) + strlen(typ->ty_name) + 2);
	(void) sprintf(sp->se_getty, "%s %s", typ->ty_getty, typ->ty_name);
	sp->se_getty_argv = construct_argv(sp->se_getty);
	if (sp->se_getty_argv == 0) {
		warning("can't parse getty for port %s", sp->se_device);
		free(sp->se_getty);
		sp->se_getty = 0;
		return (0);
	}
	if (typ->ty_window) {
		if (sp->se_window)
			free(sp->se_window);
		sp->se_window = strdup(typ->ty_window);
		sp->se_window_argv = construct_argv(sp->se_window);
		if (sp->se_window_argv == 0) {
			warning("can't parse window for port %s",
				sp->se_device);
			free(sp->se_window);
			sp->se_window = 0;
			return (0);
		}
	}
	return (1);
}

/*
 * Walk the list of ttys and create sessions for each active line.
 */
state_func_t
read_ttys()
{
	int session_index = 0;
	register session_t *sp, *snext;
	register struct ttyent *typ;

	/*
	 * Destroy any previous session state.
	 * There shouldn't be any, but just in case...
	 */
	for (sp = sessions; sp; sp = snext) {
		if (sp->se_process)
			clear_session_logs(sp);
		snext = sp->se_next;
		free_session(sp);
	}
	sessions = 0;
	if (start_session_db())
		return (state_func_t) single_user;

	/*
	 * Allocate a session entry for each active port.
	 * Note that sp starts at 0.
	 */
	while (typ = getttyent())
		if (snext = new_session(sp, ++session_index, typ))
			sp = snext;

	endttyent();

	return (state_func_t) multi_user;
}

/*
 * Start a window system running.
 */
void
start_window_system(sp)
	session_t *sp;
{
	pid_t pid;
	sigset_t mask;

	if ((pid = fork()) == -1) {
		emergency("can't fork for window system on port %s: %m",
			sp->se_device);
		/* hope that getty fails and we can try again */
		return;
	}

	if (pid)
		return;

	sigemptyset(&mask);
	sigprocmask(SIG_SETMASK, &mask, (sigset_t *) 0);

	if (setsid() < 0)
		emergency("setsid failed (window) %m");

	execv(sp->se_window_argv[0], sp->se_window_argv);
	stall("can't exec window system '%s' for port %s: %m",
		sp->se_window_argv[0], sp->se_device);
	_exit(1);
}

/*
 * Start a login session running.
 */
pid_t
start_getty(sp)
	session_t *sp;
{
	pid_t pid;
	sigset_t mask;
	time_t current_time = time((time_t *) 0);

	/*
	 * fork(), not vfork() -- we can't afford to block.
	 */
	if ((pid = fork()) == -1) {
		emergency("can't fork for getty on port %s: %m", sp->se_device);
		return -1;
	}

	if (pid)
		return pid;

	if (current_time > sp->se_started &&
	    current_time - sp->se_started < GETTY_SPACING) {
		warning("getty repeating too quickly on port %s, sleeping",
		        sp->se_device);
		sleep((unsigned) GETTY_SLEEP);
	}

	if (sp->se_window) {
		start_window_system(sp);
		sleep(WINDOW_WAIT);
	}

	sigemptyset(&mask);
	sigprocmask(SIG_SETMASK, &mask, (sigset_t *) 0);

	execv(sp->se_getty_argv[0], sp->se_getty_argv);
	stall("can't exec getty '%s' for port %s: %m",
		sp->se_getty_argv[0], sp->se_device);
	_exit(1);
}

/*
 * Collect exit status for a child.
 * If an exiting login, start a new login running.
 */
void
#ifdef __STDC__
collect_child(pid_t pid)
#else
collect_child(pid)
	pid_t pid;
#endif
{
	register session_t *sp, *sprev, *snext;

	if (! sessions)
		return;

	if (! (sp = find_session(pid)))
		return;

	clear_session_logs(sp);
	del_session(sp);
	sp->se_process = 0;

	if (sp->se_flags & SE_SHUTDOWN) {
		if (sprev = sp->se_prev)
			sprev->se_next = sp->se_next;
		else
			sessions = sp->se_next;
		if (snext = sp->se_next)
			snext->se_prev = sp->se_prev;
		free_session(sp);
		return;
	}

	if ((pid = start_getty(sp)) == -1) {
		/* serious trouble */
		requested_transition = clean_ttys;
		return;
	}

	sp->se_process = pid;
	sp->se_started = time((time_t *) 0);
	add_session(sp);
}

/*
 * Catch a signal and request a state transition.
 */
void
transition_handler(sig)
	int sig;
{

	switch (sig) {
	case SIGHUP:
		requested_transition = clean_ttys;
		break;
	case SIGTERM:
		requested_transition = death;
		break;
	case SIGTSTP:
		requested_transition = catatonia;
		break;
	default:
		requested_transition = 0;
		break;
	}
}

/*
 * Take the system multiuser.
 */
state_func_t
multi_user()
{
	pid_t pid;
	register session_t *sp;

	requested_transition = 0;

	/*
	 * If the administrator has not set the security level to -1
	 * to indicate that the kernel should not run multiuser in secure
	 * mode, and the run script has not set a higher level of security 
	 * than level 1, then put the kernel into secure mode.
	 */
	if (getsecuritylevel() == 0)
		setsecuritylevel(1);

	for (sp = sessions; sp; sp = sp->se_next) {
		if (sp->se_process)
			continue;
		if ((pid = start_getty(sp)) == -1) {
			/* serious trouble */
			requested_transition = clean_ttys;
			break;
		}
		sp->se_process = pid;
		sp->se_started = time((time_t *) 0);
		add_session(sp);
	}

	while (!requested_transition)
		if ((pid = waitpid(-1, (int *) 0, 0)) != -1)
			collect_child(pid);

	return (state_func_t) requested_transition;
}

/*
 * This is an n-squared algorithm.  We hope it isn't run often...
 */
state_func_t
clean_ttys()
{
	register session_t *sp, *sprev;
	register struct ttyent *typ;
	register int session_index = 0;
	register int devlen;

	if (! sessions)
		return (state_func_t) multi_user;

	devlen = sizeof(_PATH_DEV) - 1;
	while (typ = getttyent()) {
		++session_index;

		for (sprev = 0, sp = sessions; sp; sprev = sp, sp = sp->se_next)
			if (strcmp(typ->ty_name, sp->se_device + devlen) == 0)
				break;

		if (sp) {
			if (sp->se_index != session_index) {
				warning("port %s changed utmp index from %d to %d",
				       sp->se_device, sp->se_index,
				       session_index);
				sp->se_index = session_index;
			}
			if ((typ->ty_status & TTY_ON) == 0 ||
			    typ->ty_getty == 0) {
				sp->se_flags |= SE_SHUTDOWN;
				kill(sp->se_process, SIGHUP);
				continue;
			}
			sp->se_flags &= ~SE_SHUTDOWN;
			if (setupargv(sp, typ) == 0) {
				warning("can't parse getty for port %s",
					sp->se_device);
				sp->se_flags |= SE_SHUTDOWN;
				kill(sp->se_process, SIGHUP);
			}
			continue;
		}

		new_session(sprev, session_index, typ);
	}

	endttyent();

	return (state_func_t) multi_user;
}

/*
 * Block further logins.
 */
state_func_t
catatonia()
{
	register session_t *sp;

	for (sp = sessions; sp; sp = sp->se_next)
		sp->se_flags |= SE_SHUTDOWN;

	return (state_func_t) multi_user;
}

/*
 * Note SIGALRM.
 */
void
alrm_handler(sig)
	int sig;
{
	clang = 1;
}

/*
 * Bring the system down to single user.
 */
state_func_t
death()
{
	register session_t *sp;
	register int i;
	pid_t pid;
	static const int death_sigs[3] = { SIGHUP, SIGTERM, SIGKILL };

	for (sp = sessions; sp; sp = sp->se_next)
		sp->se_flags |= SE_SHUTDOWN;

	/* NB: should send a message to the session logger to avoid blocking. */
	logwtmp("~", "shutdown", "");

	for (i = 0; i < 3; ++i) {
		if (kill(-1, death_sigs[i]) == -1 && errno == ESRCH)
			return (state_func_t) single_user;

		clang = 0;
		alarm(DEATH_WATCH);
		do
			if ((pid = waitpid(-1, (int *)0, 0)) != -1)
				collect_child(pid);
		while (clang == 0 && errno != ECHILD);

		if (errno == ECHILD)
			return (state_func_t) single_user;
	}

	warning("some processes would not die; ps axl advised");

	return (state_func_t) single_user;
}