tty_io.c

gives an orthogonal feeling to tty s, be they consoles or rs-channels. It also implements echoing, c

		read_lock(&tasklist_lock);
		for_each_task(p) {
			if (p->tty == tty || (o_tty && p->tty == o_tty))
				p->tty = NULL;
		}
		read_unlock(&tasklist_lock);

		if (redirect == tty || (o_tty && redirect == o_tty))
			redirect = NULL;
	}

	/* check whether both sides are closing ... */
	if (!tty_closing || (o_tty && !o_tty_closing))
		return;
	
#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "freeing tty structure...");
#endif

	/*
	 * Shutdown the current line discipline, and reset it to N_TTY.
	 * N.B. why reset ldisc when we're releasing the memory??
	 */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);
	tty->ldisc = ldiscs[N_TTY];
	tty->termios->c_line = N_TTY;
	if (o_tty) {
		if (o_tty->ldisc.close)
			(o_tty->ldisc.close)(o_tty);
		o_tty->ldisc = ldiscs[N_TTY];
	}
	
	/*
	 * Make sure that the tty's task queue isn't activated. 
	 */
	run_task_queue(&tq_timer);
	flush_scheduled_tasks();

	/* 
	 * The release_mem function takes care of the details of clearing
	 * the slots and preserving the termios structure.
	 */
	release_mem(tty, idx);
}

/*
 * tty_open and tty_release keep up the tty count that contains the
 * number of opens done on a tty. We cannot use the inode-count, as
 * different inodes might point to the same tty.
 *
 * Open-counting is needed for pty masters, as well as for keeping
 * track of serial lines: DTR is dropped when the last close happens.
 * (This is not done solely through tty->count, now.  - Ted 1/27/92)
 *
 * The termios state of a pty is reset on first open so that
 * settings don't persist across reuse.
 */
static int tty_open(struct inode * inode, struct file * filp)
{
	struct tty_struct *tty;
	int noctty, retval;
	kdev_t device;
	unsigned short saved_flags;
	char	buf[64];

	saved_flags = filp->f_flags;
retry_open:
	noctty = filp->f_flags & O_NOCTTY;
	device = inode->i_rdev;
	if (device == TTY_DEV) {
		if (!current->tty)
			return -ENXIO;
		device = current->tty->device;
		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
		/* noctty = 1; */
	}
#ifdef CONFIG_VT
	if (device == CONSOLE_DEV) {
		extern int fg_console;
		device = MKDEV(TTY_MAJOR, fg_console + 1);
		noctty = 1;
	}
#endif
	if (device == SYSCONS_DEV) {
		struct console *c = console_drivers;
		while(c && !c->device)
			c = c->next;
		if (!c)
                        return -ENODEV;
                device = c->device(c);
		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/console block */
		noctty = 1;
	}

	if (device == PTMX_DEV) {
#ifdef CONFIG_UNIX98_PTYS

		/* find a free pty. */
		int major, minor;
		struct tty_driver *driver;

		/* find a device that is not in use. */
		retval = -1;
		for ( major = 0 ; major < UNIX98_NR_MAJORS ; major++ ) {
			driver = &ptm_driver[major];
			for (minor = driver->minor_start ;
			     minor < driver->minor_start + driver->num ;
			     minor++) {
				device = MKDEV(driver->major, minor);
				if (!init_dev(device, &tty)) goto ptmx_found; /* ok! */
			}
		}
		return -EIO; /* no free ptys */
	ptmx_found:
		set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
		minor -= driver->minor_start;
		devpts_pty_new(driver->other->name_base + minor, MKDEV(driver->other->major, minor + driver->other->minor_start));
		tty_register_devfs(&pts_driver[major], DEVFS_FL_DEFAULT,
				   pts_driver[major].minor_start + minor);
		noctty = 1;
		goto init_dev_done;

#else   /* CONFIG_UNIX_98_PTYS */

		return -ENODEV;

#endif  /* CONFIG_UNIX_98_PTYS */
	}

	retval = init_dev(device, &tty);
	if (retval)
		return retval;

#ifdef CONFIG_UNIX98_PTYS
init_dev_done:
#endif
	filp->private_data = tty;
	file_move(filp, &tty->tty_files);
	check_tty_count(tty, "tty_open");
	if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver.subtype == PTY_TYPE_MASTER)
		noctty = 1;
#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "opening %s...", tty_name(tty, buf));
#endif
	if (tty->driver.open)
		retval = tty->driver.open(tty, filp);
	else
		retval = -ENODEV;
	filp->f_flags = saved_flags;

	if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) && !suser())
		retval = -EBUSY;

	if (retval) {
#ifdef TTY_DEBUG_HANGUP
		printk(KERN_DEBUG "error %d in opening %s...", retval,
		       tty_name(tty, buf));
#endif

		release_dev(filp);
		if (retval != -ERESTARTSYS)
			return retval;
		if (signal_pending(current))
			return retval;
		schedule();
		/*
		 * Need to reset f_op in case a hangup happened.
		 */
		filp->f_op = &tty_fops;
		goto retry_open;
	}
	if (!noctty &&
	    current->leader &&
	    !current->tty &&
	    tty->session == 0) {
	    	task_lock(current);
		current->tty = tty;
		task_unlock(current);
		current->tty_old_pgrp = 0;
		tty->session = current->session;
		tty->pgrp = current->pgrp;
	}
	if ((tty->driver.type == TTY_DRIVER_TYPE_SERIAL) &&
	    (tty->driver.subtype == SERIAL_TYPE_CALLOUT) &&
	    (tty->count == 1)) {
		static int nr_warns;
		if (nr_warns < 5) {
			printk(KERN_WARNING "tty_io.c: "
				"process %d (%s) used obsolete /dev/%s - "
				"update software to use /dev/ttyS%d\n",
				current->pid, current->comm,
				tty_name(tty, buf), TTY_NUMBER(tty));
			nr_warns++;
		}
	}
	return 0;
}

static int tty_release(struct inode * inode, struct file * filp)
{
	lock_kernel();
	release_dev(filp);
	unlock_kernel();
	return 0;
}

/* No kernel lock held - fine */
static unsigned int tty_poll(struct file * filp, poll_table * wait)
{
	struct tty_struct * tty;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_dentry->d_inode->i_rdev, "tty_poll"))
		return 0;

	if (tty->ldisc.poll)
		return (tty->ldisc.poll)(tty, filp, wait);
	return 0;
}

static int tty_fasync(int fd, struct file * filp, int on)
{
	struct tty_struct * tty;
	int retval;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_dentry->d_inode->i_rdev, "tty_fasync"))
		return 0;
	
	retval = fasync_helper(fd, filp, on, &tty->fasync);
	if (retval <= 0)
		return retval;

	if (on) {
		if (!waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = 1;
		if (filp->f_owner.pid == 0) {
			filp->f_owner.pid = (-tty->pgrp) ? : current->pid;
			filp->f_owner.uid = current->uid;
			filp->f_owner.euid = current->euid;
		}
	} else {
		if (!tty->fasync && !waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = N_TTY_BUF_SIZE;
	}
	return 0;
}

static int tiocsti(struct tty_struct *tty, char * arg)
{
	char ch, mbz = 0;

	if ((current->tty != tty) && !suser())
		return -EPERM;
	if (get_user(ch, arg))
		return -EFAULT;
	tty->ldisc.receive_buf(tty, &ch, &mbz, 1);
	return 0;
}

static int tiocgwinsz(struct tty_struct *tty, struct winsize * arg)
{
	if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
		return -EFAULT;
	return 0;
}

static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
	struct winsize * arg)
{
	struct winsize tmp_ws;

	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
		return -EFAULT;
	if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
		return 0;
	if (tty->pgrp > 0)
		kill_pg(tty->pgrp, SIGWINCH, 1);
	if ((real_tty->pgrp != tty->pgrp) && (real_tty->pgrp > 0))
		kill_pg(real_tty->pgrp, SIGWINCH, 1);
	tty->winsize = tmp_ws;
	real_tty->winsize = tmp_ws;
	return 0;
}

static int tioccons(struct inode *inode,
	struct tty_struct *tty, struct tty_struct *real_tty)
{
	if (inode->i_rdev == SYSCONS_DEV ||
	    inode->i_rdev == CONSOLE_DEV) {
		if (!suser())
			return -EPERM;
		redirect = NULL;
		return 0;
	}
	if (redirect)
		return -EBUSY;
	redirect = real_tty;
	return 0;
}


static int fionbio(struct file *file, int *arg)
{
	int nonblock;

	if (get_user(nonblock, arg))
		return -EFAULT;

	if (nonblock)
		file->f_flags |= O_NONBLOCK;
	else
		file->f_flags &= ~O_NONBLOCK;
	return 0;
}

static int tiocsctty(struct tty_struct *tty, int arg)
{
	if (current->leader &&
	    (current->session == tty->session))
		return 0;
	/*
	 * The process must be a session leader and
	 * not have a controlling tty already.
	 */
	if (!current->leader || current->tty)
		return -EPERM;
	if (tty->session > 0) {
		/*
		 * This tty is already the controlling
		 * tty for another session group!
		 */
		if ((arg == 1) && suser()) {
			/*
			 * Steal it away
			 */
			struct task_struct *p;

			read_lock(&tasklist_lock);
			for_each_task(p)
				if (p->tty == tty)
					p->tty = NULL;
			read_unlock(&tasklist_lock);
		} else
			return -EPERM;
	}
	task_lock(current);
	current->tty = tty;
	task_unlock(current);
	current->tty_old_pgrp = 0;
	tty->session = current->session;
	tty->pgrp = current->pgrp;
	return 0;
}

static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *arg)
{
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	 */
	if (tty == real_tty && current->tty != real_tty)
		return -ENOTTY;
	return put_user(real_tty->pgrp, arg);
}

static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *arg)
{
	pid_t pgrp;
	int retval = tty_check_change(real_tty);

	if (retval == -EIO)
		return -ENOTTY;
	if (retval)
		return retval;
	if (!current->tty ||
	    (current->tty != real_tty) ||
	    (real_tty->session != current->session))
		return -ENOTTY;
	if (get_user(pgrp, (pid_t *) arg))
		return -EFAULT;
	if (pgrp < 0)
		return -EINVAL;
	if (session_of_pgrp(pgrp) != current->session)
		return -EPERM;
	real_tty->pgrp = pgrp;
	return 0;
}

static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *arg)
{
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	*/
	if (tty == real_tty && current->tty != real_tty)
		return -ENOTTY;
	if (real_tty->session <= 0)
		return -ENOTTY;
	return put_user(real_tty->session, arg);
}

static int tiocttygstruct(struct tty_struct *tty, struct tty_struct *arg)
{
	if (copy_to_user(arg, tty, sizeof(*arg)))
		return -EFAULT;
	return 0;
}

static int tiocsetd(struct tty_struct *tty, int *arg)
{
	int ldisc;

	if (get_user(ldisc, arg))
		return -EFAULT;
	return tty_set_ldisc(tty, ldisc);
}

static int send_break(struct tty_struct *tty, int duration)
{
	set_current_state(TASK_INTERRUPTIBLE);

	tty->driver.break_ctl(tty, -1);
	if (!signal_pending(current))
		schedule_timeout(duration);
	tty->driver.break_ctl(tty, 0);
	if (signal_pending(current))
		return -EINTR;
	return 0;
}

/*
 * Split this up, as gcc can choke on it otherwise..
 */
int tty_ioctl(struct inode * inode, struct file * file,
	      unsigned int cmd, unsigned long arg)
{
	struct tty_struct *tty, *real_tty;
	int retval;
	
	tty = (struct tty_struct *)file->private_data;
	if (tty_paranoia_check(tty, inode->i_rdev, "tty_ioctl"))
		return -EINVAL;

	real_tty = tty;
	if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver.subtype == PTY_TYPE_MASTER)
		real_tty = tty->link;

	/*
	 * Break handling by driver
	 */
	if (!tty->driver.break_ctl) {
		switch(cmd) {
		case TIOCSBRK:
		case TIOCCBRK:
			if (tty->driver.ioctl)
				return tty->driver.ioctl(tty, file, cmd, arg);
			return -EINVAL;
			
		/* These two ioctl's always return success; even if */
		/* the driver doesn't support them. */
		case TCSBRK:
		case TCSBRKP:
			if (!tty->driver.ioctl)
				return 0;
			retval = tty->driver.ioctl(tty, file, cmd, arg);
			if (retval == -ENOIOCTLCMD)
				retval = 0;
			return retval;
		}
	}

	/*
	 * Factor out some common prep work
	 */
	switch (cmd) {
	case TIOCSETD:
	case TIOCSBRK:
	case TIOCCBRK:
	case TCSBRK:
	case TCSBRKP:			
		retval = tty_check_change(tty);
		if (retval)
			return retval;
		if (cmd != TIOCCBRK) {
			tty_wait_until_sent(tty, 0);
			if (signal_pending(current))
				return -EINTR;
		}
		break;
	}

	switch (cmd) {
		case TIOCSTI:
			return tiocsti(tty, (char *)arg);
		case TIOCGWINSZ:
			return tiocgwinsz(tty, (struct winsize *) arg);
		case TIOCSWINSZ:
			return tiocswinsz(tty, real_tty, (struct winsize *) arg);
		case TIOCCONS:
			return tioccons(inode, tty, real_tty);
		case FIONBIO:
			return fionbio(file, (int *) arg);
		case TIOCEXCL:
			set_bit(TTY_EXCLUSIVE, &tty->flags);
			return 0;
		case TIOCNXCL:
			clear_bit(TTY_EXCLUSIVE, &tty->flags);
			return 0;
		case TIOCNOTTY:
			if (current->tty != tty)
				return -ENOTTY;
			if (current->leader)
				disassociate_ctty(0);
			task_lock(current);
			current->tty = NULL;
			task_unlock(current);
			return 0;
		case TIOCSCTTY:
			return tiocsctty(tty, arg);
		case TIOCGPGRP:
			return tiocgpgrp(tty, real_tty, (pid_t *) arg);
		case TIOCSPGRP:
			return tiocspgrp(tty, real_tty, (pid_t *) arg);
		case TIOCGSID:
			return tiocgsid(tty, real_tty, (pid_t *) arg);
		case TIOCGETD:
			return put_user(tty->ldisc.num, (int *) arg);
		case TIOCSETD:
			return tiocsetd(tty, (int *) arg);
#ifdef CONFIG_VT
		case TIOCLINUX:
			return tioclinux(tty, arg);
#endif
		case TIOCTTYGSTRUCT:
			return tiocttygstruct(tty, (struct tty_struct *) arg);

		/*
		 * Break handling
		 */
		case TIOCSBRK:	/* Turn break on, unconditionally */
			tty->driver.break_ctl(tty, -1);
			return 0;
			
		case TIOCCBRK:	/* Turn break off, unconditionally */
			tty->driver.break_ctl(tty, 0);
			return 0;
		case TCSBRK:   /* SVID version: non-zero arg --> no break */
			/*
			 * XXX is the above comment correct, or the
			 * code below correct?  Is this ioctl used at
			 * all by anyone?
			 */
			if (!arg)
				return send_break(tty, HZ/4);
			return 0;
		case TCSBRKP:	/* support for POSIX tcsendbreak() */	
			return send_break(tty, arg ? arg*(HZ/10) : HZ/4);
	}
	if (tty->driver.ioctl) {
		int retval = (tty->driver.ioctl)(tty, file, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}
	if (tty->ldisc.ioctl) {
		int retval = (tty->ldisc.ioctl)(tty, file, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}
	return -EINVAL;
}


/*
 * This implements the "Secure Attention Key" ---  the idea is to
 * prevent trojan horses by killing all processes associated with this
 * tty when the user hits the "Secure Attention Key".  Required for
 * super-paranoid applications --- see the Orange Book for more details.