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/* Initialization program for the user level of the OS--this is the
 * first thing that gets run: pid 1.
 *
 * Runs /etc/brc.  If it fails spawns a /bin/sh on the console (this is
 * single user mode.)  If /etc/brc exits cleanly it starts multi user
 * mode by running /etc/rc, then it spawns gettys on those terminals in
 * /etc/ttys.
 *
 * In multi user mode it respawns gettys as needed, removes tty locks
 * when a getty dies, and wait()s for orphans.
 *
 * Accepts two signals:  SIG_HUP and SIG_QUIT.
 * SIG_HUP causes init to kill (SIG_KILL) all processes and go to single
 * user mode.  SIG_QUIT causes /etc/ttys to be reread.
 * All other signals are ignored.
 */
#define NEWTTYS	1
#define	NOSWAPPER
#define	NODRIVERS
#define	DEBUG	0

/*
 * Init
 *
 * Compile -s -n -i on machines other than pdp11.
 */

#include <sys/dir.h>
#include <signal.h>
#include <utmp.h>
#include <sgtty.h>
#include <errno.h>
#include <sys/malloc.h>
#include <access.h>

/*
 * Miscellaneous constants.
 */
#define	NULL	((char *)0)
#define	BRCFILE	"/etc/brc"

#if	DEBUG
#define	dbmsg(arglist)	msg arglist
int debug_fd = -1;
#else
#define	dbmsg(arglist)
#endif

/*
 * Structure containing information about each terminal.
 */
typedef struct	tty {
	struct	tty	*t_next;	/* Pointer to next entry */
	int	t_pid;			/* Process id */
	char	t_flag;			/* 0 == no getty, 1 == want getty */
	char	t_linetype;		/* Line type (local, remote, etc.) */
	char	t_baud[2];		/* Baud descriptor */
	char	t_tty[5+DIRSIZ+1];	/* tty name */
} TTY;

/* Console tty for simplified spawn */
TTY contty = {
	NULL, 0, 0, 'l', "P", "/dev/console"
};

/* Null tty for simplified spawn */
TTY nultty = {
	NULL, 0, 0, 'l', "P", "/dev/null"
};

/*
 * Default environment list for shell.
 */
char	*defenv0[] = {		/* Default environment for super user */
	"USER=root",
	"HOME=/etc",
	"PATH=/bin:/usr/bin:/etc:",
	"PS1=# ",
	NULL
};

/*
 * Variables.
 */
static char _version[]="init version 4.0";
struct	tty *ttyp;			/* Terminal list */
int	hangflag;			/* Go to single user */
int	quitflag;			/* Scan tty file */

/*
 * Functions.
 */
extern	int	sighang();
extern	int	sigquit();
extern	int	sigalrm();
extern	struct	tty *findtty();


main(argc, argv) register int argc; char *argv[];
{
	register TTY *tp;
	register int i, n, multi;
	unsigned status;

dbmsg(("Entering init  ", NULL));

	multi = 0;			/* do not go to multiuser */
	/* Make sure that every flag has a usable initial value.  */
	quitflag = 0;	/* Do not rescan /etc/ttys.  */
	hangflag = 0;	/* Do not shut down.  */

	if (getpid() != 1)
		exit(1);
	umask(022);
dbmsg(("About to fakearg  ", NULL));
	fakearg(0, argv);
	if ((n = creat("/etc/boottime", 0644)) >= 0)
		close(n);
dbmsg(("CREATED boottime ", NULL));
#ifndef NOSWAPPER
	if (argc >= 2)
		loadswp(argv[1]);
#endif
#ifndef NODRIVERS
	for (n=2; n<argc; n++)
		loaddrv(argv[n]);
#endif
dbmsg(("About to putwtmp  ", NULL));
	putwtmp("~", "");

	/*
	 * Ignore all possible signals.  We do not want to be able to
	 * accidentally kill init.
	 */
	for (i=1; i<=NSIG; i++)
		signal(i, SIG_IGN);

	/*
	 * We MUST NOT ignore SIGCHLD--we care deeply about our children.
	 */

#if _I386
dbmsg(("About to default for SIGCHLD  ", NULL));
	signal(SIGCHLD, SIG_DFL);
#endif

dbmsg(("About to trap for SIGHUP  ", NULL));
	signal(SIGHUP, sighang);

dbmsg(("About to fork()  ", NULL));
	if (fork() == 0) {			/* paranoid sync */
		sync();
		exit(0);
	}
dbmsg(("About to access brc file  ", NULL));
	if (access(BRCFILE, AEXISTS) == 0) {
		dbmsg(("executing /etc/brc", NULL));
		n = spawn(&contty, "/bin/sh", "sh", BRCFILE, NULL);
		while (wait(&status) != n)
			;
		if (status == 0)
			multi = 1;
	}

	for (;;) {
		while (inittys() == 0) {
			if (!multi) {
				/* Single user - no multi-user ttys active */
				/* No rescan signals accepted */
				signal(SIGQUIT, SIG_IGN);
				/* Wait for things to quiet down */
				/* Necessitated by system shared segment bug */
				/* But don't wait for hung processes */
				signal(SIGALRM, sigalrm);
				alarm(2);
				while (wait(NULL) >= 0)
					;
				alarm(0);

				dbmsg(("sync()ing", NULL));
				sync();	/* Obviates need for user sync.  */
				/* Initiate single user state */
				dbmsg(("spawn single user shell", NULL));
				n = spawn(&contty, "/bin/sh", "-sh", NULL);
				/* Wait for shell to exit */
				if (waitc(n) < 0) {
					hangflag = 0;
					kill9(-1);
					continue;
				}
			}
			/* Start multi-user state */
			dbmsg(("executing /etc/rc", NULL));
			n = spawn(&nultty, "/bin/sh", "sh", "/etc/rc", NULL);
			if (waitc(n) < 0) {
				hangflag = 0;
				kill9(-1);
				continue;
			}
			/* Scan the ttys file */
			scantty(); /* scantty() may reset quitflag */
			/* Prepare for rescan ttys signal */
			quitflag = 0;
			signal(SIGQUIT, sigquit);
		}
		/* Wait for orphaned processes */
		n = wait(&status);
		if (hangflag) {
			/* Return to single user */
			dbmsg(("going single user", NULL));
			hangflag = 0;
			kill9(-1);
			for (tp=ttyp; tp!=NULL; tp=tp->t_next)  {
				tp->t_pid = 0;
				tp->t_flag = 0;
			}
			if (fork() == 0) {		/* paranoid sync */
				sync();
				exit(0);
			}
			multi = 0;
			continue;
		}
		if (quitflag) {
			/* Scan for ttys with changes in status */
			dbmsg(("quit signal, rescan ttys", NULL));
			quitflag = 0;
			scantty();
			continue;
		}
		if (n > 0) {
			/* Logout process n. */
			for (tp=ttyp; tp; tp=tp->t_next) {
				if (n != tp->t_pid)
					continue;
				tp->t_pid = 0;
				dbmsg(("logout process on tty ", tp->t_tty, NULL));
				putwtmp(&tp->t_tty[5], "");
				clrutmp(&tp->t_tty[5]);
				chmod(tp->t_tty, 0700);
				chown(tp->t_tty, 0, 0);

				/*
				 * Unlock the tty; it was locked by 
				 * process n: originally login.
				 *
				 * We don't care about the return value;
				 * if it was locked by somebody else,
				 * locknrm() won't remove the lock.
				 */
 				unlockntty(strrchr(tp->t_tty, '/')+1, n);
				/* See if we panicked */
				if ((status>>8) == 0377)
					tp->t_flag = 0;
			}
		}
	}
}
/*
 * Called when we get a hangup.
 */
sighang()
{
	signal(SIGHUP, sighang);
	hangflag = 1;
}

/*
 * Called when a quit is received.
 */
sigquit()
{
	signal(SIGQUIT, sigquit);
	quitflag = 1;
}

/*
 * Called when an alarm is received in single user mode.
 */
sigalrm()
{
}

/*
 * Called when an alarm is received in multi user mode.
 */
mulsigalrm()
{
	kill(1, SIGQUIT);	/* Cause a rescan of /etc/ttys.  */
}

#ifndef NOSWAPPER
/*
 * Load the swapper.
 */
loadswp(np)
char *np;
{
	if (np[0] == '\0')
		return;
	if (fork() != 0)
		return;
	execve(np, NULL, NULL);
	panic("cannot load ", np);
}
#endif

#ifndef NODRIVERS
/*
 * Load the given driver.
 */
loaddrv(np)
char *np;
{
	register int pid;
	int status;

	pid = spawn(&nultty, "/etc/load", "load", np, NULL);
	while (wait(&status) != pid)
		;
	if (status != 0)
		exit(status);
}
#endif

/*
 * If there are any terminals which need to be serviced, service them.
 * Return the number of active terminals.
*/
inittys()
{
	register TTY *tp;
	register int n;

	n = 0;
	for (tp=ttyp; tp!=NULL; tp=tp->t_next) {
		if (tp->t_pid == 0 && tp->t_flag != 0)
			login(tp);
		n += tp->t_flag;
	}
	return (n);
}

/*
 * Wait for the given process to complete.
 */
waitc(p1)
register int p1;
{
	register int p2;

	while ((p2=wait(NULL))>=0 && p2!=p1)
		;
	return (p2);
}

/*
 * Scan the tty file.
 */
scantty()
{
	register TTY *tp;	/* Used to pick entries from ttyp.  */
	register int fd;	/* File descriptor for /etc/ttys.  */
	TTY tty;		/* Used to hold entries from /etc/ttys.  */

	extern char *sbrk();

	dbmsg(("Rescan", NULL));

	unlockntty("console", 0);	/* Wipe out locks on the console.  */
	
	if ((fd=open("/etc/ttys", 0)) < 0)
		return;
	while (readtty(&tty, fd) != 0) {
		/* If there is no record of this tty, create one.  */
		if ((tp=findtty(&tty)) == NULL) {
			if ((tp = sbrk(sizeof(*tp))) == BADSBRK)
				panic("too many ttys");
			*tp = tty;
			tp->t_next = ttyp;
			ttyp = tp;
			continue;
		}

		/*
		 * If /etc/ttys has changed for this tty,
		 * adjust the in-memory version to the desired state.
		 */
		if (tp->t_flag != tty.t_flag
		 || tp->t_baud[0] != tty.t_baud[0]
		 || tp->t_linetype != tty.t_linetype) {
			/*
			 * If this tty is locked, and we want to start a
			 * getty, do not do it until the lock goes away.
			 *
			 * Ignore locks on the console.
			 */
			if ((0 != strcmp(tty.t_tty, "/dev/console")) &&
			    lockttyexist(strrchr(tty.t_tty, '/')+1) &&
			    0 != tty.t_flag) {
				dbmsg(("Setting an alarm", NULL));
				/* Check again in a few seconds.  */
				signal(SIGALRM, mulsigalrm);
				alarm(10);
			} else {
				dbmsg(("Starting getty", NULL));
				tp->t_flag = tty.t_flag;
				tp->t_baud[0] = tty.t_baud[0];
					tp->t_linetype = tty.t_linetype;
				/* Kill off any process lingering on this tty.  */
				if (tp->t_pid != 0)
					kill9(tp->t_pid);
			}
		}
	}
	close(fd);
}

/*
 * Read a line from the terminal file and save the appropriate fields in
 * the terminal structure.
 */
readtty(tp, fd)
register TTY *tp;
{
	register char *lp;
	char c[1];
	char line[3+DIRSIZ+1];

	lp = line;
	for (;;) {
		if (read(fd, c, sizeof(c)) != sizeof(c))
			return (0);
		if (c[0] == '\n')
			break;
		if (lp < &line[3+DIRSIZ])
			*lp++ = c[0];
	}
	*lp++ = '\0';
	if (lp < &line[5])
		return (0);
	lp = line;
	tp->t_flag = (*lp++) != '0';
#if	NEWTTYS
	tp->t_linetype = *lp++;
#else
	tp->t_linetype = 'l';
#endif
	tp->t_pid = 0;
	tp->t_baud[0] = *lp++;
	tp->t_baud[1] = '\0';
	strcpy(tp->t_tty, "/dev/");
	strncpy(&tp->t_tty[5], lp, DIRSIZ);
	tp->t_tty[5+DIRSIZ] = '\0';
	dbmsg(("readtty: ", tp->t_tty, NULL));
	return (1);
}

/*
 * Given a terminal structure containing the name of a terminal,
 * find the entry in the terminal list.
 */
TTY *
findtty(tp1)
register TTY *tp1;
{
	register TTY *tp2;

	for (tp2=ttyp; tp2!=NULL; tp2=tp2->t_next)
		if (strcmp(tp1->t_tty, tp2->t_tty) == 0)
			return (tp2);
	return (NULL);
}

/*
 * Given a terminal structure, spawn off a login (getty).
 */
login(tp)
register TTY *tp;
{
	register int pid;

	pid = spawn(tp,
		"/etc/getty",
		(tp->t_linetype == 'l') ? "-" : "-r",
		tp->t_baud,
		NULL);
	if (pid < 0) {
		tp->t_flag = 0;
		dbmsg(("spawn failed tty ", tp->t_tty, NULL));
	} else
		tp->t_pid = pid;
}

/*
 * Spawn off a command.
 */
spawn(tp, np, ap)
TTY *tp;
char *np, *ap;
{
	register int pid;
	register int fd;
	int i;

	if ((pid=fork()) != 0)
		return (pid);
#if DEBUG
	close(debug_fd);
#endif
	setpgrp();
	fakearg(1, tp->t_tty);
	while ((fd=open(tp->t_tty, 2)) < 0 && errno==EDBUSY)
		sleep(1);
	if (fd < 0)
		panic("cannot open ", tp->t_tty, NULL);
	ioctl(fd, TIOCSETG);
#if	NEWTTYS
	if (tp->t_linetype == 'r')      /* remote line? */
	   ioctl(fd, TIOCHPCL);   /* "hangup" on last close */
#endif
	dup2(0, 1);
	dup2(0, 2);

	/* Restore all signals for any child process.  */
	for (i=1; i<=NSIG; i++)
		signal(i, SIG_DFL);

	execve(np, &ap, defenv0);
	panic("cannot execute ", np, NULL);
	return (pid);
}

/*
 * Write an entry onto the wtmp file.
 */
putwtmp(lp, np) char *lp, *np;
{
	register int fd;
	struct utmp utmp;
	extern time_t time();

	if ((fd=open("/usr/adm/wtmp", 1)) < 0)
		return;
	strncpy(utmp.ut_line, lp, 8);
	strncpy(utmp.ut_name, np, DIRSIZ);
	utmp.ut_time = time(NULL);
	lseek(fd, 0L, 2);
	write(fd, (char *)&utmp, sizeof(utmp));
	close(fd);
}

/*
 * Clear out a utmp entry.
 */
clrutmp(tty)
char *tty;
{
	register int fd;
	struct utmp utmp;
	static struct utmp ctmp;

	if ((fd=open("/etc/utmp", 2)) < 0)
		return;
	while (read(fd, &utmp, sizeof(utmp)) == sizeof(utmp)) 
	{  if (strncmp(utmp.ut_line, tty, 8))  /* no match? */
		 continue;		    /* yes, go for next record */
	   lseek(fd, (long)-sizeof(utmp), 1);
	   write(fd, &ctmp, sizeof(ctmp));   /* clear utmp record */
	   break;
	}
	close(fd);
}

/*
 * Print out a list of error messages and exit.
 */
panic(cp)
char *cp;
{
	register char **cpp;

	close(0);
	open("/dev/console", 2);
	write(0, "/etc/init: ", 11);
	for (cpp=&cp; *cpp!=NULL; cpp++)
		write(0, *cpp, strlen(*cpp));
	write(0, "\n", 1);
	exit(0377);
}

/*
 * Make the arg listing of ps come out right.
 *	f == 0, first entry, determine buffer limits.
 *	In this case, name the forks of init -tty until the
 *	tty opens.
 *	f != 0, later entry, fill buffer with lies.
 */
fakearg(f, argv)
int f;
char **argv;
{
	static char *fbuf;
	static int nbuf;
	register int n;
	register char *p;

	if (f == 0) {
		fbuf = argv[0];
		nbuf = 0;
		while (argv[1] != NULL)
			argv += 1;
		nbuf = argv[0] - fbuf + strlen(argv[0]) - 1;
	} else {
		if (fbuf == NULL || nbuf == 0)
			return;
		p = (char *)argv;
		p += 5;			/* tty part of /dev/tty* */
		n = 1;
		*fbuf++ = '-';
		do
			*fbuf++ = *p;
		while (++n < nbuf && *p++ != 0);
		*fbuf = 01;		/* non-ascii terminator */
	}
}

/*
 * Send SIGKILL to process, delaying and sending twice to ensure death.
 */
kill9(pid) register int pid;
{
	kill(pid, SIGKILL);
	sleep(1);
	kill(pid, SIGKILL);
}

#if	DEBUG
#define SCREEN_ADDR	0xb0000L	/* Physical address of screen.
					 * Use 0xb8000 for color screen.
					 */
#define SCREEN_SIZE	(80*25*2)	/* Size of screen in bytes.  */

/*
 * Write a debug message to the console.
 * The args should be a NULL-terminated list of strings.
 */
msg(cp) char *cp;
{
	register char **cpp;
#if 0
/* Old init couldn't write to console because it messed up process groups. */
	int fd;
	static long mp = SCREEN_ADDR;
	int i;

	if (mp >= SCREEN_ADDR + SCREEN_SIZE)
		mp = SCREEN_ADDR;
	fd = open("/dev/mem", 2);
	lseek(fd, mp, 0);
	write(fd, ":", 1);
	lseek(fd, 1L, 1);
	mp += 2;
	for (cpp=&cp; *cpp!=NULL; cpp++) {
		for (i = 0; i < strlen(*cpp); i++) {
			write(fd, (*cpp)+i, 1);
			lseek(fd, 1L, 1);
			mp += 2;
		}
		write(fd, " ", 1);
		lseek(fd, 1L, 1);
		mp += 2;
	}	
	close(fd);
#else
	if (debug_fd == -1)
		debug_fd = open("/dev/console", 2);
	write(debug_fd, ":", 1);
	for (cpp=&cp; *cpp!=NULL; cpp++) {
		write(debug_fd, *cpp, strlen(cp));
		write(debug_fd, " ", 1);
	}	
#endif
}
#endif

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