static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg)
{
	struct tty_struct *tty = file_tty(file);
	struct tty_ldisc *ld;
	int retval = -ENOIOCTLCMD;

	switch (cmd) {
	case TIOCOUTQ:
	case TIOCSTI:
	case TIOCGWINSZ:
	case TIOCSWINSZ:
	case TIOCGEXCL:
	case TIOCGETD:
	case TIOCSETD:
	case TIOCGDEV:
	case TIOCMGET:
	case TIOCMSET:
	case TIOCMBIC:
	case TIOCMBIS:
	case TIOCGICOUNT:
	case TIOCGPGRP:
	case TIOCSPGRP:
	case TIOCGSID:
	case TIOCSERGETLSR:
	case TIOCGRS485:
	case TIOCSRS485:
#ifdef TIOCGETP
	case TIOCGETP:
	case TIOCSETP:
	case TIOCSETN:
#endif
#ifdef TIOCGETC
	case TIOCGETC:
	case TIOCSETC:
#endif
#ifdef TIOCGLTC
	case TIOCGLTC:
	case TIOCSLTC:
#endif
	case TCSETSF:
	case TCSETSW:
	case TCSETS:
	case TCGETS:
#ifdef TCGETS2
	case TCGETS2:
	case TCSETSF2:
	case TCSETSW2:
	case TCSETS2:
#endif
	case TCGETA:
	case TCSETAF:
	case TCSETAW:
	case TCSETA:
	case TIOCGLCKTRMIOS:
	case TIOCSLCKTRMIOS:
#ifdef TCGETX
	case TCGETX:
	case TCSETX:
	case TCSETXW:
	case TCSETXF:
#endif
	case TIOCGSOFTCAR:
	case TIOCSSOFTCAR:

	case PPPIOCGCHAN:
	case PPPIOCGUNIT:
		return tty_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
	case TIOCCONS:
	case TIOCEXCL:
	case TIOCNXCL:
	case TIOCVHANGUP:
	case TIOCSBRK:
	case TIOCCBRK:
	case TCSBRK:
	case TCSBRKP:
	case TCFLSH:
	case TIOCGPTPEER:
	case TIOCNOTTY:
	case TIOCSCTTY:
	case TCXONC:
	case TIOCMIWAIT:
	case TIOCSERCONFIG:
		return tty_ioctl(file, cmd, arg);
	}

	if (tty_paranoia_check(tty, file_inode(file), "tty_ioctl"))
		return -EINVAL;

	switch (cmd) {
	case TIOCSSERIAL:
		return compat_tty_tiocsserial(tty, compat_ptr(arg));
	case TIOCGSERIAL:
		return compat_tty_tiocgserial(tty, compat_ptr(arg));
	}
	if (tty->ops->compat_ioctl) {
		retval = tty->ops->compat_ioctl(tty, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}

	ld = tty_ldisc_ref_wait(tty);
	if (!ld)
		return hung_up_tty_compat_ioctl(file, cmd, arg);
	if (ld->ops->compat_ioctl)
		retval = ld->ops->compat_ioctl(tty, file, cmd, arg);
	if (retval == -ENOIOCTLCMD && ld->ops->ioctl)
		retval = ld->ops->ioctl(tty, file,
				(unsigned long)compat_ptr(cmd), arg);
	tty_ldisc_deref(ld);

	return retval;
}


struct device *tty_register_device_attr(struct tty_driver *driver,
				   unsigned index, struct device *device,
				   void *drvdata,
				   const struct attribute_group **attr_grp)
{
	char name[64];
	dev_t devt = MKDEV(driver->major, driver->minor_start) + index;
	struct ktermios *tp;
	struct device *dev;
	int retval;

	if (index >= driver->num) {
		pr_err("%s: Attempt to register invalid tty line number (%d)\n",
		       driver->name, index);
		return ERR_PTR(-EINVAL);
	}

	if (driver->type == TTY_DRIVER_TYPE_PTY)
		pty_line_name(driver, index, name);
	else
		tty_line_name(driver, index, name);

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return ERR_PTR(-ENOMEM);

	dev->devt = devt;
	dev->class = tty_class;
	dev->parent = device;
	dev->release = tty_device_create_release;
	dev_set_name(dev, "%s", name);
	dev->groups = attr_grp;
	dev_set_drvdata(dev, drvdata);

	dev_set_uevent_suppress(dev, 1);

	retval = device_register(dev);
	if (retval)
		goto err_put;

	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
		/*
		 * Free any saved termios data so that the termios state is
		 * reset when reusing a minor number.
		 */
		tp = driver->termios[index];
		if (tp) {
			driver->termios[index] = NULL;
			kfree(tp);
		}

		retval = tty_cdev_add(driver, devt, index, 1);
		if (retval)
			goto err_del;
	}

	dev_set_uevent_suppress(dev, 0);
	kobject_uevent(&dev->kobj, KOBJ_ADD);

	return dev;

err_del:
	device_del(dev);
err_put:
	put_device(dev);

	return ERR_PTR(retval);
}

tty: Fix ->session locking

Currently, locking of ->session is very inconsistent; most places
protect it using the legacy tty mutex, but disassociate_ctty(),
__do_SAK(), tiocspgrp() and tiocgsid() don't.
Two of the writers hold the ctrl_lock (because they already need it for
->pgrp), but __proc_set_tty() doesn't do that yet.

On a PREEMPT=y system, an unprivileged user can theoretically abuse
this broken locking to read 4 bytes of freed memory via TIOCGSID if
tiocgsid() is preempted long enough at the right point. (Other things
might also go wrong, especially if root-only ioctls are involved; I'm
not sure about that.)

Change the locking on ->session such that:

 - tty_lock() is held by all writers: By making disassociate_ctty()
   hold it. This should be fine because the same lock can already be
   taken through the call to tty_vhangup_session().
   The tricky part is that we need to shorten the area covered by
   siglock to be able to take tty_lock() without ugly retry logic; as
   far as I can tell, this should be fine, since nothing in the
   signal_struct is touched in the `if (tty)` branch.
 - ctrl_lock is held by all writers: By changing __proc_set_tty() to
   hold the lock a little longer.
 - All readers that aren't holding tty_lock() hold ctrl_lock: By
   adding locking to tiocgsid() and __do_SAK(), and expanding the area
   covered by ctrl_lock in tiocspgrp().

Cc: stable@kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;

extern void tty_sysctl_init(void);

static char ptychar[] = "pqrstuvwxyzabcde";


struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
{
	struct tty_struct *tty;

	tty = kzalloc(sizeof(*tty), GFP_KERNEL);
	if (!tty)
		return NULL;

	kref_init(&tty->kref);
	tty->magic = TTY_MAGIC;
	if (tty_ldisc_init(tty)) {
		kfree(tty);
		return NULL;
	}
	tty->session = NULL;
	tty->pgrp = NULL;
	mutex_init(&tty->legacy_mutex);
	mutex_init(&tty->throttle_mutex);
	init_rwsem(&tty->termios_rwsem);
	mutex_init(&tty->winsize_mutex);
	init_ldsem(&tty->ldisc_sem);
	init_waitqueue_head(&tty->write_wait);
	init_waitqueue_head(&tty->read_wait);
	INIT_WORK(&tty->hangup_work, do_tty_hangup);
	mutex_init(&tty->atomic_write_lock);
	spin_lock_init(&tty->ctrl_lock);
	spin_lock_init(&tty->flow_lock);
	spin_lock_init(&tty->files_lock);
	INIT_LIST_HEAD(&tty->tty_files);
	INIT_WORK(&tty->SAK_work, do_SAK_work);

	tty->driver = driver;
	tty->ops = driver->ops;
	tty->index = idx;
	tty_line_name(driver, idx, tty->name);
	tty->dev = tty_get_device(tty);

	return tty;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;


static void do_SAK_work(struct work_struct *work)
{
	struct tty_struct *tty =
		container_of(work, struct tty_struct, SAK_work);
	__do_SAK(tty);
}


struct pid *tty_get_pgrp(struct tty_struct *tty)
{
	unsigned long flags;
	struct pid *pgrp;

	spin_lock_irqsave(&tty->ctrl_lock, flags);
	pgrp = get_pid(tty->pgrp);
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);

	return pgrp;
}


static void pty_line_name(struct tty_driver *driver, int index, char *p)
{
	int i = index + driver->name_base;
	/* ->name is initialized to "ttyp", but "tty" is expected */
	sprintf(p, "%s%c%x",
		driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
		ptychar[i >> 4 & 0xf], i & 0xf);
}


static void __proc_set_tty(struct tty_struct *tty)
{
	unsigned long flags;

	spin_lock_irqsave(&tty->ctrl_lock, flags);
	/*
	 * The session and fg pgrp references will be non-NULL if
	 * tiocsctty() is stealing the controlling tty
	 */
	put_pid(tty->session);
	put_pid(tty->pgrp);
	tty->pgrp = get_pid(task_pgrp(current));
	tty->session = get_pid(task_session(current));
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
	if (current->signal->tty) {
		tty_debug(tty, "current tty %s not NULL!!\n",
			  current->signal->tty->name);
		tty_kref_put(current->signal->tty);
	}
	put_pid(current->signal->tty_old_pgrp);
	current->signal->tty = tty_kref_get(tty);
	current->signal->tty_old_pgrp = NULL;
}

/* No explicit global definitions found. */


static int tty_tiocgicount(struct tty_struct *tty, void __user *arg)
{
	int retval = -EINVAL;
	struct serial_icounter_struct icount;
	memset(&icount, 0, sizeof(icount));
	if (tty->ops->get_icount)
		retval = tty->ops->get_icount(tty, &icount);
	if (retval != 0)
		return retval;
	if (copy_to_user(arg, &icount, sizeof(icount)))
		return -EFAULT;
	return 0;
}


ssize_t redirected_tty_write(struct file *file, const char __user *buf,
						size_t count, loff_t *ppos)
{
	struct file *p = NULL;

	spin_lock(&redirect_lock);
	if (redirect)
		p = get_file(redirect);
	spin_unlock(&redirect_lock);

	if (p) {
		ssize_t res;
		res = vfs_write(p, buf, count, &p->f_pos);
		fput(p);
		return res;
	}
	return tty_write(file, buf, count, ppos);
}


static void tty_device_create_release(struct device *dev)
{
	dev_dbg(dev, "releasing...\n");
	kfree(dev);
}


void session_clear_tty(struct pid *session)
{
	struct task_struct *p;
	do_each_pid_task(session, PIDTYPE_SID, p) {
		proc_clear_tty(p);
	} while_each_pid_task(session, PIDTYPE_SID, p);
}


static int tiocswinsz(struct tty_struct *tty, struct winsize __user *arg)
{
	struct winsize tmp_ws;
	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
		return -EFAULT;

	if (tty->ops->resize)
		return tty->ops->resize(tty, &tmp_ws);
	else
		return tty_do_resize(tty, &tmp_ws);
}


void disassociate_ctty(int on_exit)
{
	struct tty_struct *tty;

	if (!current->signal->leader)
		return;

	tty = get_current_tty();
	if (tty) {
		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY) {
			tty_vhangup_session(tty);
		} else {
			struct pid *tty_pgrp = tty_get_pgrp(tty);
			if (tty_pgrp) {
				kill_pgrp(tty_pgrp, SIGHUP, on_exit);
				if (!on_exit)
					kill_pgrp(tty_pgrp, SIGCONT, on_exit);
				put_pid(tty_pgrp);
			}
		}
		tty_kref_put(tty);

	} else if (on_exit) {
		struct pid *old_pgrp;
		spin_lock_irq(&current->sighand->siglock);
		old_pgrp = current->signal->tty_old_pgrp;
		current->signal->tty_old_pgrp = NULL;
		spin_unlock_irq(&current->sighand->siglock);
		if (old_pgrp) {
			kill_pgrp(old_pgrp, SIGHUP, on_exit);
			kill_pgrp(old_pgrp, SIGCONT, on_exit);
			put_pid(old_pgrp);
		}
		return;
	}

	spin_lock_irq(&current->sighand->siglock);
	put_pid(current->signal->tty_old_pgrp);
	current->signal->tty_old_pgrp = NULL;
	tty = tty_kref_get(current->signal->tty);
	spin_unlock_irq(&current->sighand->siglock);

	if (tty) {
		unsigned long flags;

		tty_lock(tty);
		spin_lock_irqsave(&tty->ctrl_lock, flags);
		put_pid(tty->session);
		put_pid(tty->pgrp);
		tty->session = NULL;
		tty->pgrp = NULL;
		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
		tty_unlock(tty);
		tty_kref_put(tty);
	}

	/* Now clear signal->tty under the lock */
	read_lock(&tasklist_lock);
	session_clear_tty(task_session(current));
	read_unlock(&tasklist_lock);
}


const char *tty_driver_name(const struct tty_struct *tty)
{
	if (!tty || !tty->driver)
		return "";
	return tty->driver->name;
}


static __poll_t hung_up_tty_poll(struct file *filp, poll_table *wait)
{
	return EPOLLIN | EPOLLOUT | EPOLLERR | EPOLLHUP | EPOLLRDNORM | EPOLLWRNORM;
}

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

static char ptychar[] = "pqrstuvwxyzabcde";

struct serial_struct32 {
	compat_int_t    type;
	compat_int_t    line;
	compat_uint_t   port;
	compat_int_t    irq;
	compat_int_t    flags;
	compat_int_t    xmit_fifo_size;
	compat_int_t    custom_divisor;
	compat_int_t    baud_base;
	unsigned short  close_delay;
	char    io_type;
	char    reserved_char;
	compat_int_t    hub6;
	unsigned short  closing_wait; /* time to wait before closing */
	unsigned short  closing_wait2; /* no longer used... */
	compat_uint_t   iomem_base;
	unsigned short  iomem_reg_shift;
	unsigned int    port_high;
	/* compat_ulong_t  iomap_base FIXME */
	compat_int_t    reserved;
}


static struct tty_struct *tty_open_by_driver(dev_t device,
					     struct file *filp)
{
	struct tty_struct *tty;
	struct tty_driver *driver = NULL;
	int index = -1;
	int retval;

	mutex_lock(&tty_mutex);
	driver = tty_lookup_driver(device, filp, &index);
	if (IS_ERR(driver)) {
		mutex_unlock(&tty_mutex);
		return ERR_CAST(driver);
	}

	/* check whether we're reopening an existing tty */
	tty = tty_driver_lookup_tty(driver, filp, index);
	if (IS_ERR(tty)) {
		mutex_unlock(&tty_mutex);
		goto out;
	}

	if (tty) {
		if (tty_port_kopened(tty->port)) {
			tty_kref_put(tty);
			mutex_unlock(&tty_mutex);
			tty = ERR_PTR(-EBUSY);
			goto out;
		}
		mutex_unlock(&tty_mutex);
		retval = tty_lock_interruptible(tty);
		tty_kref_put(tty);  /* drop kref from tty_driver_lookup_tty() */
		if (retval) {
			if (retval == -EINTR)
				retval = -ERESTARTSYS;
			tty = ERR_PTR(retval);
			goto out;
		}
		retval = tty_reopen(tty);
		if (retval < 0) {
			tty_unlock(tty);
			tty = ERR_PTR(retval);
		}
	} else { /* Returns with the tty_lock held for now */
		tty = tty_init_dev(driver, index);
		mutex_unlock(&tty_mutex);
	}
out:
	tty_driver_kref_put(driver);
	return tty;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

static char ptychar[] = "pqrstuvwxyzabcde";


void tty_set_operations(struct tty_driver *driver,
			const struct tty_operations *op)
{
	driver->ops = op;
};


static ssize_t hung_up_tty_write(struct file *file, const char __user *buf,
				 size_t count, loff_t *ppos)
{
	return -EIO;
}


void tty_init_termios(struct tty_struct *tty)
{
	struct ktermios *tp;
	int idx = tty->index;

	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
		tty->termios = tty->driver->init_termios;
	else {
		/* Check for lazy saved data */
		tp = tty->driver->termios[idx];
		if (tp != NULL) {
			tty->termios = *tp;
			tty->termios.c_line  = tty->driver->init_termios.c_line;
		} else
			tty->termios = tty->driver->init_termios;
	}
	/* Compatibility until drivers always set this */
	tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
	tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;

extern void tty_sysctl_init(void);


static void release_tty(struct tty_struct *tty, int idx)
{
	/* This should always be true but check for the moment */
	WARN_ON(tty->index != idx);
	WARN_ON(!mutex_is_locked(&tty_mutex));
	if (tty->ops->shutdown)
		tty->ops->shutdown(tty);
	tty_save_termios(tty);
	tty_driver_remove_tty(tty->driver, tty);
	if (tty->port)
		tty->port->itty = NULL;
	if (tty->link)
		tty->link->port->itty = NULL;
	if (tty->port)
		tty_buffer_cancel_work(tty->port);
	if (tty->link)
		tty_buffer_cancel_work(tty->link->port);

	tty_kref_put(tty->link);
	tty_kref_put(tty);
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

extern void tty_sysctl_init(void);

static char ptychar[] = "pqrstuvwxyzabcde";


static char *tty_devnode(struct device *dev, umode_t *mode)
{
	if (!mode)
		return NULL;
	if (dev->devt == MKDEV(TTYAUX_MAJOR, 0) ||
	    dev->devt == MKDEV(TTYAUX_MAJOR, 2))
		*mode = 0666;
	return NULL;
}


int tty_unregister_driver(struct tty_driver *driver)
{
#if 0
	/* FIXME */
	if (driver->refcount)
		return -EBUSY;
#endif
	unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
				driver->num);
	mutex_lock(&tty_mutex);
	list_del(&driver->tty_drivers);
	mutex_unlock(&tty_mutex);
	return 0;
}


void tty_vhangup_self(void)
{
	struct tty_struct *tty;

	tty = get_current_tty();
	if (tty) {
		tty_vhangup(tty);
		tty_kref_put(tty);
	}
}


static int tiocsctty(struct tty_struct *tty, struct file *file, int arg)
{
	int ret = 0;

	tty_lock(tty);
	read_lock(&tasklist_lock);

	if (current->signal->leader && (task_session(current) == tty->session))
		goto unlock;

	/*
	 * The process must be a session leader and
	 * not have a controlling tty already.
	 */
	if (!current->signal->leader || current->signal->tty) {
		ret = -EPERM;
		goto unlock;
	}

	if (tty->session) {
		/*
		 * This tty is already the controlling
		 * tty for another session group!
		 */
		if (arg == 1 && capable(CAP_SYS_ADMIN)) {
			/*
			 * Steal it away
			 */
			session_clear_tty(tty->session);
		} else {
			ret = -EPERM;
			goto unlock;
		}
	}

	/* See the comment in tty_open_proc_set_tty(). */
	if ((file->f_mode & FMODE_READ) == 0 && !capable(CAP_SYS_ADMIN)) {
		ret = -EPERM;
		goto unlock;
	}

	proc_set_tty(tty);
unlock:
	read_unlock(&tasklist_lock);
	tty_unlock(tty);
	return ret;
}


void no_tty(void)
{
	/* FIXME: Review locking here. The tty_lock never covered any race
	   between a new association and proc_clear_tty but possible we need
	   to protect against this anyway */
	struct task_struct *tsk = current;
	disassociate_ctty(0);
	proc_clear_tty(tsk);
}


static void do_tty_hangup(struct work_struct *work)
{
	struct tty_struct *tty =
		container_of(work, struct tty_struct, hangup_work);

	__tty_hangup(tty, 0);
}


static int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
			      const char *routine)
{
#ifdef TTY_PARANOIA_CHECK
	if (!tty) {
		pr_warn("(%d:%d): %s: NULL tty\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
	if (tty->magic != TTY_MAGIC) {
		pr_warn("(%d:%d): %s: bad magic number\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
#endif
	return 0;
}


struct tty_driver *tty_find_polling_driver(char *name, int *line)
{
	struct tty_driver *p, *res = NULL;
	int tty_line = 0;
	int len;
	char *str, *stp;

	for (str = name; *str; str++)
		if ((*str >= '0' && *str <= '9') || *str == ',')
			break;
	if (!*str)
		return NULL;

	len = str - name;
	tty_line = simple_strtoul(str, &str, 10);

	mutex_lock(&tty_mutex);
	/* Search through the tty devices to look for a match */
	list_for_each_entry(p, &tty_drivers, tty_drivers) {
		if (!len || strncmp(name, p->name, len) != 0)
			continue;
		stp = str;
		if (*stp == ',')
			stp++;
		if (*stp == '\0')
			stp = NULL;

		if (tty_line >= 0 && tty_line < p->num && p->ops &&
		    p->ops->poll_init && !p->ops->poll_init(p, tty_line, stp)) {
			res = tty_driver_kref_get(p);
			*line = tty_line;
			break;
		}
	}
	mutex_unlock(&tty_mutex);

	return res;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;

static char ptychar[] = "pqrstuvwxyzabcde";


void tty_add_file(struct tty_struct *tty, struct file *file)
{
	struct tty_file_private *priv = file->private_data;

	priv->tty = tty;
	priv->file = file;

	spin_lock(&tty->files_lock);
	list_add(&priv->list, &tty->tty_files);
	spin_unlock(&tty->files_lock);
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;

extern void tty_sysctl_init(void);


static int this_tty(const void *t, struct file *file, unsigned fd)
{
	if (likely(file->f_op->read != tty_read))
		return 0;
	return file_tty(file) != t ? 0 : fd + 1;
}


void tty_vhangup(struct tty_struct *tty)
{
	tty_debug_hangup(tty, "vhangup\n");
	__tty_hangup(tty, 0);
}


int tty_put_char(struct tty_struct *tty, unsigned char ch)
{
	if (tty->ops->put_char)
		return tty->ops->put_char(tty, ch);
	return tty->ops->write(tty, &ch, 1);
}


static int tiocgetd(struct tty_struct *tty, int __user *p)
{
	struct tty_ldisc *ld;
	int ret;

	ld = tty_ldisc_ref_wait(tty);
	if (!ld)
		return -EIO;
	ret = put_user(ld->ops->num, p);
	tty_ldisc_deref(ld);
	return ret;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

static char ptychar[] = "pqrstuvwxyzabcde";


int tty_alloc_file(struct file *file)
{
	struct tty_file_private *priv;

	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	file->private_data = priv;

	return 0;
}


static int tty_write_lock(struct tty_struct *tty, int ndelay)
{
	if (!mutex_trylock(&tty->atomic_write_lock)) {
		if (ndelay)
			return -EAGAIN;
		if (mutex_lock_interruptible(&tty->atomic_write_lock))
			return -ERESTARTSYS;
	}
	return 0;
}


dev_t tty_devnum(struct tty_struct *tty)
{
	return MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
}


static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	unsigned long flags;
	pid_t sid;

	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	*/
	if (tty == real_tty && current->signal->tty != real_tty)
		return -ENOTTY;

	spin_lock_irqsave(&real_tty->ctrl_lock, flags);
	if (!real_tty->session)
		goto err;
	sid = pid_vnr(real_tty->session);
	spin_unlock_irqrestore(&real_tty->ctrl_lock, flags);

	return put_user(sid, p);

err:
	spin_unlock_irqrestore(&real_tty->ctrl_lock, flags);
	return -ENOTTY;
}


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

	tty_lock(tty);
	if (!tty_hung_up_p(filp))
		retval = __tty_fasync(fd, filp, on);
	tty_unlock(tty);

	return retval;
}


int tty_dev_name_to_number(const char *name, dev_t *number)
{
	struct tty_driver *p;
	int ret;
	int index, prefix_length = 0;
	const char *str;

	for (str = name; *str && !isdigit(*str); str++)
		;

	if (!*str)
		return -EINVAL;

	ret = kstrtoint(str, 10, &index);
	if (ret)
		return ret;

	prefix_length = str - name;
	mutex_lock(&tty_mutex);

	list_for_each_entry(p, &tty_drivers, tty_drivers)
		if (prefix_length == strlen(p->name) && strncmp(name,
					p->name, prefix_length) == 0) {
			if (index < p->num) {
				*number = MKDEV(p->major, p->minor_start + index);
				goto out;
			}
		}

	/* if here then driver wasn't found */
	ret = -ENODEV;
out:
	mutex_unlock(&tty_mutex);
	return ret;
}

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;

static char ptychar[] = "pqrstuvwxyzabcde";

struct serial_struct32 {
	compat_int_t    type;
	compat_int_t    line;
	compat_uint_t   port;
	compat_int_t    irq;
	compat_int_t    flags;
	compat_int_t    xmit_fifo_size;
	compat_int_t    custom_divisor;
	compat_int_t    baud_base;
	unsigned short  close_delay;
	char    io_type;
	char    reserved_char;
	compat_int_t    hub6;
	unsigned short  closing_wait; /* time to wait before closing */
	unsigned short  closing_wait2; /* no longer used... */
	compat_uint_t   iomem_base;
	unsigned short  iomem_reg_shift;
	unsigned int    port_high;
	/* compat_ulong_t  iomap_base FIXME */
	compat_int_t    reserved;
}

struct class *tty_class;


static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver,
		struct file *file, int idx)
{
	struct tty_struct *tty;

	if (driver->ops->lookup)
		if (!file)
			tty = ERR_PTR(-EIO);
		else
			tty = driver->ops->lookup(driver, file, idx);
	else
		tty = driver->ttys[idx];

	if (!IS_ERR(tty))
		tty_kref_get(tty);
	return tty;
}


static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
		int *index)
{
	struct tty_driver *driver = NULL;

	switch (device) {
#ifdef CONFIG_VT
	case MKDEV(TTY_MAJOR, 0): {
		extern struct tty_driver *console_driver;
		driver = tty_driver_kref_get(console_driver);
		*index = fg_console;
		break;
	}
#endif
	case MKDEV(TTYAUX_MAJOR, 1): {
		struct tty_driver *console_driver = console_device(index);
		if (console_driver) {
			driver = tty_driver_kref_get(console_driver);
			if (driver && filp) {
				/* Don't let /dev/console block */
				filp->f_flags |= O_NONBLOCK;
				break;
			}
		}
		if (driver)
			tty_driver_kref_put(driver);
		return ERR_PTR(-ENODEV);
	}
	default:
		driver = get_tty_driver(device, index);
		if (!driver)
			return ERR_PTR(-ENODEV);
		break;
	}
	return driver;
}

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

extern void tty_sysctl_init(void);

static char ptychar[] = "pqrstuvwxyzabcde";


static int compat_tty_tiocgserial(struct tty_struct *tty,
			struct serial_struct32 __user *ss)
{
	struct serial_struct32 v32;
	struct serial_struct v;
	int err;

	memset(&v, 0, sizeof(v));
	memset(&v32, 0, sizeof(v32));

	if (!tty->ops->get_serial)
		return -ENOTTY;
	err = tty->ops->get_serial(tty, &v);
	if (!err) {
		memcpy(&v32, &v, offsetof(struct serial_struct32, iomem_base));
		v32.iomem_base = (unsigned long)v.iomem_base >> 32 ?
			0xfffffff : ptr_to_compat(v.iomem_base);
		v32.iomem_reg_shift = v.iomem_reg_shift;
		v32.port_high = v.port_high;
		if (copy_to_user(ss, &v32, sizeof(v32)))
			err = -EFAULT;
	}
	return err;
}


static int __init tty_class_init(void)
{
	tty_class = class_create(THIS_MODULE, "tty");
	if (IS_ERR(tty_class))
		return PTR_ERR(tty_class);
	tty_class->devnode = tty_devnode;
	return 0;
}


static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
{
	struct tty_struct *tty;
	int retval;

	if (device != MKDEV(TTYAUX_MAJOR, 0))
		return NULL;

	tty = get_current_tty();
	if (!tty)
		return ERR_PTR(-ENXIO);

	filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
	/* noctty = 1; */
	tty_lock(tty);
	tty_kref_put(tty);	/* safe to drop the kref now */

	retval = tty_reopen(tty);
	if (retval < 0) {
		tty_unlock(tty);
		tty = ERR_PTR(retval);
	}
	return tty;
}


const char *tty_name(const struct tty_struct *tty)
{
	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
		return "NULL tty";
	return tty->name;
}


int tty_signal_session_leader(struct tty_struct *tty, int exit_session)
{
	struct task_struct *p;
	int refs = 0;
	struct pid *tty_pgrp = NULL;

	read_lock(&tasklist_lock);
	if (tty->session) {
		do_each_pid_task(tty->session, PIDTYPE_SID, p) {
			spin_lock_irq(&p->sighand->siglock);
			if (p->signal->tty == tty) {
				p->signal->tty = NULL;
				/* We defer the dereferences outside fo
				   the tasklist lock */
				refs++;
			}
			if (!p->signal->leader) {
				spin_unlock_irq(&p->sighand->siglock);
				continue;
			}
			__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
			__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
			put_pid(p->signal->tty_old_pgrp);  /* A noop */
			spin_lock(&tty->ctrl_lock);
			tty_pgrp = get_pid(tty->pgrp);
			if (tty->pgrp)
				p->signal->tty_old_pgrp = get_pid(tty->pgrp);
			spin_unlock(&tty->ctrl_lock);
			spin_unlock_irq(&p->sighand->siglock);
		} while_each_pid_task(tty->session, PIDTYPE_SID, p);
	}
	read_unlock(&tasklist_lock);

	if (tty_pgrp) {
		if (exit_session)
			kill_pgrp(tty_pgrp, SIGHUP, exit_session);
		put_pid(tty_pgrp);
	}

	return refs;
}


long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct tty_struct *tty = file_tty(file);
	struct tty_struct *real_tty;
	void __user *p = (void __user *)arg;
	int retval;
	struct tty_ldisc *ld;

	if (tty_paranoia_check(tty, file_inode(file), "tty_ioctl"))
		return -EINVAL;

	real_tty = tty_pair_get_tty(tty);

	/*
	 * 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;
	}

	/*
	 *	Now do the stuff.
	 */
	switch (cmd) {
	case TIOCSTI:
		return tiocsti(tty, p);
	case TIOCGWINSZ:
		return tiocgwinsz(real_tty, p);
	case TIOCSWINSZ:
		return tiocswinsz(real_tty, p);
	case TIOCCONS:
		return real_tty != tty ? -EINVAL : tioccons(file);
	case TIOCEXCL:
		set_bit(TTY_EXCLUSIVE, &tty->flags);
		return 0;
	case TIOCNXCL:
		clear_bit(TTY_EXCLUSIVE, &tty->flags);
		return 0;
	case TIOCGEXCL:
	{
		int excl = test_bit(TTY_EXCLUSIVE, &tty->flags);
		return put_user(excl, (int __user *)p);
	}
	case TIOCGETD:
		return tiocgetd(tty, p);
	case TIOCSETD:
		return tiocsetd(tty, p);
	case TIOCVHANGUP:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		tty_vhangup(tty);
		return 0;
	case TIOCGDEV:
	{
		unsigned int ret = new_encode_dev(tty_devnum(real_tty));
		return put_user(ret, (unsigned int __user *)p);
	}
	/*
	 * Break handling
	 */
	case TIOCSBRK:	/* Turn break on, unconditionally */
		if (tty->ops->break_ctl)
			return tty->ops->break_ctl(tty, -1);
		return 0;
	case TIOCCBRK:	/* Turn break off, unconditionally */
		if (tty->ops->break_ctl)
			return tty->ops->break_ctl(tty, 0);
		return 0;
	case TCSBRK:   /* SVID version: non-zero arg --> no break */
		/* non-zero arg means wait for all output data
		 * to be sent (performed above) but don't send break.
		 * This is used by the tcdrain() termios function.
		 */
		if (!arg)
			return send_break(tty, 250);
		return 0;
	case TCSBRKP:	/* support for POSIX tcsendbreak() */
		return send_break(tty, arg ? arg*100 : 250);

	case TIOCMGET:
		return tty_tiocmget(tty, p);
	case TIOCMSET:
	case TIOCMBIC:
	case TIOCMBIS:
		return tty_tiocmset(tty, cmd, p);
	case TIOCGICOUNT:
		return tty_tiocgicount(tty, p);
	case TCFLSH:
		switch (arg) {
		case TCIFLUSH:
		case TCIOFLUSH:
		/* flush tty buffer and allow ldisc to process ioctl */
			tty_buffer_flush(tty, NULL);
			break;
		}
		break;
	case TIOCSSERIAL:
		return tty_tiocsserial(tty, p);
	case TIOCGSERIAL:
		return tty_tiocgserial(tty, p);
	case TIOCGPTPEER:
		/* Special because the struct file is needed */
		return ptm_open_peer(file, tty, (int)arg);
	default:
		retval = tty_jobctrl_ioctl(tty, real_tty, file, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}
	if (tty->ops->ioctl) {
		retval = tty->ops->ioctl(tty, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}
	ld = tty_ldisc_ref_wait(tty);
	if (!ld)
		return hung_up_tty_ioctl(file, cmd, arg);
	retval = -EINVAL;
	if (ld->ops->ioctl) {
		retval = ld->ops->ioctl(tty, file, cmd, arg);
		if (retval == -ENOIOCTLCMD)
			retval = -ENOTTY;
	}
	tty_ldisc_deref(ld);
	return retval;
}


static int is_ignored(int sig)
{
	return (sigismember(&current->blocked, sig) ||
		current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
}


void tty_driver_kref_put(struct tty_driver *driver)
{
	kref_put(&driver->kref, destruct_tty_driver);
}


void tty_default_fops(struct file_operations *fops)
{
	*fops = tty_fops;
}


void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty)
{
	read_lock(&tasklist_lock);
	spin_lock_irq(&current->sighand->siglock);
	if (current->signal->leader &&
	    !current->signal->tty &&
	    tty->session == NULL) {
		/*
		 * Don't let a process that only has write access to the tty
		 * obtain the privileges associated with having a tty as
		 * controlling terminal (being able to reopen it with full
		 * access through /dev/tty, being able to perform pushback).
		 * Many distributions set the group of all ttys to "tty" and
		 * grant write-only access to all terminals for setgid tty
		 * binaries, which should not imply full privileges on all ttys.
		 *
		 * This could theoretically break old code that performs open()
		 * on a write-only file descriptor. In that case, it might be
		 * necessary to also permit this if
		 * inode_permission(inode, MAY_READ) == 0.
		 */
		if (filp->f_mode & FMODE_READ)
			__proc_set_tty(tty);
	}
	spin_unlock_irq(&current->sighand->siglock);
	read_unlock(&tasklist_lock);
}


static int tiocsetd(struct tty_struct *tty, int __user *p)
{
	int disc;
	int ret;

	if (get_user(disc, p))
		return -EFAULT;

	ret = tty_set_ldisc(tty, disc);

	return ret;
}


void tty_unregister_device(struct tty_driver *driver, unsigned index)
{
	device_destroy(tty_class,
		MKDEV(driver->major, driver->minor_start) + index);
	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
		cdev_del(driver->cdevs[index]);
		driver->cdevs[index] = NULL;
	}
}


static int tty_tiocgserial(struct tty_struct *tty, struct serial_struct __user *ss)
{
	struct serial_struct v;
	int err;

	memset(&v, 0, sizeof(v));
	if (!tty->ops->get_serial)
		return -ENOTTY;
	err = tty->ops->get_serial(tty, &v);
	if (!err && copy_to_user(ss, &v, sizeof(v)))
		err = -EFAULT;
	return err;
}


static ssize_t show_cons_active(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct console *cs[16];
	int i = 0;
	struct console *c;
	ssize_t count = 0;

	console_lock();
	for_each_console(c) {
		if (!c->device)
			continue;
		if (!c->write)
			continue;
		if ((c->flags & CON_ENABLED) == 0)
			continue;
		cs[i++] = c;
		if (i >= ARRAY_SIZE(cs))
			break;
	}
	while (i--) {
		int index = cs[i]->index;
		struct tty_driver *drv = cs[i]->device(cs[i], &index);

		/* don't resolve tty0 as some programs depend on it */
		if (drv && (cs[i]->index > 0 || drv->major != TTY_MAJOR))
			count += tty_line_name(drv, index, buf + count);
		else
			count += sprintf(buf + count, "%s%d",
					 cs[i]->name, cs[i]->index);

		count += sprintf(buf + count, "%c", i ? ' ':'\n');
	}
	console_unlock();

	return count;
}


void put_tty_driver(struct tty_driver *d)
{
	tty_driver_kref_put(d);
}


int tty_register_driver(struct tty_driver *driver)
{
	int error;
	int i;
	dev_t dev;
	struct device *d;

	if (!driver->major) {
		error = alloc_chrdev_region(&dev, driver->minor_start,
						driver->num, driver->name);
		if (!error) {
			driver->major = MAJOR(dev);
			driver->minor_start = MINOR(dev);
		}
	} else {
		dev = MKDEV(driver->major, driver->minor_start);
		error = register_chrdev_region(dev, driver->num, driver->name);
	}
	if (error < 0)
		goto err;

	if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC) {
		error = tty_cdev_add(driver, dev, 0, driver->num);
		if (error)
			goto err_unreg_char;
	}

	mutex_lock(&tty_mutex);
	list_add(&driver->tty_drivers, &tty_drivers);
	mutex_unlock(&tty_mutex);

	if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {
		for (i = 0; i < driver->num; i++) {
			d = tty_register_device(driver, i, NULL);
			if (IS_ERR(d)) {
				error = PTR_ERR(d);
				goto err_unreg_devs;
			}
		}
	}
	proc_tty_register_driver(driver);
	driver->flags |= TTY_DRIVER_INSTALLED;
	return 0;

err_unreg_devs:
	for (i--; i >= 0; i--)
		tty_unregister_device(driver, i);

	mutex_lock(&tty_mutex);
	list_del(&driver->tty_drivers);
	mutex_unlock(&tty_mutex);

err_unreg_char:
	unregister_chrdev_region(dev, driver->num);
err:
	return error;
}


static ssize_t hung_up_tty_read(struct file *file, char __user *buf,
				size_t count, loff_t *ppos)
{
	return 0;
}


static void tty_flush_works(struct tty_struct *tty)
{
	flush_work(&tty->SAK_work);
	flush_work(&tty->hangup_work);
	if (tty->link) {
		flush_work(&tty->link->SAK_work);
		flush_work(&tty->link->hangup_work);
	}
}


int __tty_check_change(struct tty_struct *tty, int sig)
{
	unsigned long flags;
	struct pid *pgrp, *tty_pgrp;
	int ret = 0;

	if (current->signal->tty != tty)
		return 0;

	rcu_read_lock();
	pgrp = task_pgrp(current);

	spin_lock_irqsave(&tty->ctrl_lock, flags);
	tty_pgrp = tty->pgrp;
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);

	if (tty_pgrp && pgrp != tty_pgrp) {
		if (is_ignored(sig)) {
			if (sig == SIGTTIN)
				ret = -EIO;
		} else if (is_current_pgrp_orphaned())
			ret = -EIO;
		else {
			kill_pgrp(pgrp, sig, 1);
			set_thread_flag(TIF_SIGPENDING);
			ret = -ERESTARTSYS;
		}
	}
	rcu_read_unlock();

	if (!tty_pgrp)
		tty_warn(tty, "sig=%d, tty->pgrp == NULL!\n", sig);

	return ret;
}


static int tiocgwinsz(struct tty_struct *tty, struct winsize __user *arg)
{
	int err;

	mutex_lock(&tty->winsize_mutex);
	err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
	mutex_unlock(&tty->winsize_mutex);

	return err ? -EFAULT: 0;
}


void do_SAK(struct tty_struct *tty)
{
	if (!tty)
		return;
	schedule_work(&tty->SAK_work);
}


static int tty_driver_install_tty(struct tty_driver *driver,
						struct tty_struct *tty)
{
	return driver->ops->install ? driver->ops->install(driver, tty) :
		tty_standard_install(driver, tty);
}


void stop_tty(struct tty_struct *tty)
{
	unsigned long flags;

	spin_lock_irqsave(&tty->flow_lock, flags);
	__stop_tty(tty);
	spin_unlock_irqrestore(&tty->flow_lock, flags);
}


int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
{
	struct pid *pgrp;

	/* Lock the tty */
	mutex_lock(&tty->winsize_mutex);
	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
		goto done;

	/* Signal the foreground process group */
	pgrp = tty_get_pgrp(tty);
	if (pgrp)
		kill_pgrp(pgrp, SIGWINCH, 1);
	put_pid(pgrp);

	tty->winsize = *ws;
done:
	mutex_unlock(&tty->winsize_mutex);
	return 0;
}


static void destruct_tty_driver(struct kref *kref)
{
	struct tty_driver *driver = container_of(kref, struct tty_driver, kref);
	int i;
	struct ktermios *tp;

	if (driver->flags & TTY_DRIVER_INSTALLED) {
		for (i = 0; i < driver->num; i++) {
			tp = driver->termios[i];
			if (tp) {
				driver->termios[i] = NULL;
				kfree(tp);
			}
			if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV))
				tty_unregister_device(driver, i);
		}
		proc_tty_unregister_driver(driver);
		if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)
			cdev_del(driver->cdevs[0]);
	}
	kfree(driver->cdevs);
	kfree(driver->ports);
	kfree(driver->termios);
	kfree(driver->ttys);
	kfree(driver);
}


static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
		unsigned int index, unsigned int count)
{
	int err;

	/* init here, since reused cdevs cause crashes */
	driver->cdevs[index] = cdev_alloc();
	if (!driver->cdevs[index])
		return -ENOMEM;
	driver->cdevs[index]->ops = &tty_fops;
	driver->cdevs[index]->owner = driver->owner;
	err = cdev_add(driver->cdevs[index], dev, count);
	if (err)
		kobject_put(&driver->cdevs[index]->kobj);
	return err;
}


static struct device *tty_get_device(struct tty_struct *tty)
{
	dev_t devt = tty_devnum(tty);
	return class_find_device_by_devt(tty_class, devt);
}


static struct pid *session_of_pgrp(struct pid *pgrp)
{
	struct task_struct *p;
	struct pid *sid = NULL;

	p = pid_task(pgrp, PIDTYPE_PGID);
	if (p == NULL)
		p = pid_task(pgrp, PIDTYPE_PID);
	if (p != NULL)
		sid = task_session(p);

	return sid;
}


static inline ssize_t do_tty_write(
	ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
	struct tty_struct *tty,
	struct file *file,
	const char __user *buf,
	size_t count)
{
	ssize_t ret, written = 0;
	unsigned int chunk;

	ret = tty_write_lock(tty, file->f_flags & O_NDELAY);
	if (ret < 0)
		return ret;

	/*
	 * We chunk up writes into a temporary buffer. This
	 * simplifies low-level drivers immensely, since they
	 * don't have locking issues and user mode accesses.
	 *
	 * But if TTY_NO_WRITE_SPLIT is set, we should use a
	 * big chunk-size..
	 *
	 * The default chunk-size is 2kB, because the NTTY
	 * layer has problems with bigger chunks. It will
	 * claim to be able to handle more characters than
	 * it actually does.
	 *
	 * FIXME: This can probably go away now except that 64K chunks
	 * are too likely to fail unless switched to vmalloc...
	 */
	chunk = 2048;
	if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
		chunk = 65536;
	if (count < chunk)
		chunk = count;

	/* write_buf/write_cnt is protected by the atomic_write_lock mutex */
	if (tty->write_cnt < chunk) {
		unsigned char *buf_chunk;

		if (chunk < 1024)
			chunk = 1024;

		buf_chunk = kmalloc(chunk, GFP_KERNEL);
		if (!buf_chunk) {
			ret = -ENOMEM;
			goto out;
		}
		kfree(tty->write_buf);
		tty->write_cnt = chunk;
		tty->write_buf = buf_chunk;
	}

	/* Do the write .. */
	for (;;) {
		size_t size = count;
		if (size > chunk)
			size = chunk;
		ret = -EFAULT;
		if (copy_from_user(tty->write_buf, buf, size))
			break;
		ret = write(tty, file, tty->write_buf, size);
		if (ret <= 0)
			break;
		written += ret;
		buf += ret;
		count -= ret;
		if (!count)
			break;
		ret = -ERESTARTSYS;
		if (signal_pending(current))
			break;
		cond_resched();
	}
	if (written) {
		tty_update_time(&file_inode(file)->i_mtime);
		ret = written;
	}
out:
	tty_write_unlock(tty);
	return ret;
}


static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
		unsigned long arg)
{
	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}


static int tioccons(struct file *file)
{
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (file->f_op->write == redirected_tty_write) {
		struct file *f;
		spin_lock(&redirect_lock);
		f = redirect;
		redirect = NULL;
		spin_unlock(&redirect_lock);
		if (f)
			fput(f);
		return 0;
	}
	spin_lock(&redirect_lock);
	if (redirect) {
		spin_unlock(&redirect_lock);
		return -EBUSY;
	}
	redirect = get_file(file);
	spin_unlock(&redirect_lock);
	return 0;
}


static int compat_tty_tiocsserial(struct tty_struct *tty,
		struct serial_struct32 __user *ss)
{
	static DEFINE_RATELIMIT_STATE(depr_flags,
			DEFAULT_RATELIMIT_INTERVAL,
			DEFAULT_RATELIMIT_BURST);
	char comm[TASK_COMM_LEN];
	struct serial_struct32 v32;
	struct serial_struct v;
	int flags;

	if (copy_from_user(&v32, ss, sizeof(*ss)))
		return -EFAULT;

	memcpy(&v, &v32, offsetof(struct serial_struct32, iomem_base));
	v.iomem_base = compat_ptr(v32.iomem_base);
	v.iomem_reg_shift = v32.iomem_reg_shift;
	v.port_high = v32.port_high;
	v.iomap_base = 0;

	flags = v.flags & ASYNC_DEPRECATED;

	if (flags && __ratelimit(&depr_flags))
		pr_warn("%s: '%s' is using deprecated serial flags (with no effect): %.8x\n",
			__func__, get_task_comm(comm, current), flags);
	if (!tty->ops->set_serial)
		return -ENOTTY;
	return tty->ops->set_serial(tty, &v);
}


static void proc_set_tty(struct tty_struct *tty)
{
	spin_lock_irq(&current->sighand->siglock);
	__proc_set_tty(tty);
	spin_unlock_irq(&current->sighand->siglock);
}


static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty)
{
	if (driver->ops->remove)
		driver->ops->remove(driver, tty);
	else
		driver->ttys[tty->index] = NULL;
}


static __poll_t tty_poll(struct file *filp, poll_table *wait)
{
	struct tty_struct *tty = file_tty(filp);
	struct tty_ldisc *ld;
	__poll_t ret = 0;

	if (tty_paranoia_check(tty, file_inode(filp), "tty_poll"))
		return 0;

	ld = tty_ldisc_ref_wait(tty);
	if (!ld)
		return hung_up_tty_poll(filp, wait);
	if (ld->ops->poll)
		ret = ld->ops->poll(tty, filp, wait);
	tty_ldisc_deref(ld);
	return ret;
}


void tty_wakeup(struct tty_struct *tty)
{
	struct tty_ldisc *ld;

	if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
		ld = tty_ldisc_ref(tty);
		if (ld) {
			if (ld->ops->write_wakeup)
				ld->ops->write_wakeup(tty);
			tty_ldisc_deref(ld);
		}
	}
	wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
}


struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner,
		unsigned long flags)
{
	struct tty_driver *driver;
	unsigned int cdevs = 1;
	int err;

	if (!lines || (flags & TTY_DRIVER_UNNUMBERED_NODE && lines > 1))
		return ERR_PTR(-EINVAL);

	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
	if (!driver)
		return ERR_PTR(-ENOMEM);

	kref_init(&driver->kref);
	driver->magic = TTY_DRIVER_MAGIC;
	driver->num = lines;
	driver->owner = owner;
	driver->flags = flags;

	if (!(flags & TTY_DRIVER_DEVPTS_MEM)) {
		driver->ttys = kcalloc(lines, sizeof(*driver->ttys),
				GFP_KERNEL);
		driver->termios = kcalloc(lines, sizeof(*driver->termios),
				GFP_KERNEL);
		if (!driver->ttys || !driver->termios) {
			err = -ENOMEM;
			goto err_free_all;
		}
	}

	if (!(flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
		driver->ports = kcalloc(lines, sizeof(*driver->ports),
				GFP_KERNEL);
		if (!driver->ports) {
			err = -ENOMEM;
			goto err_free_all;
		}
		cdevs = lines;
	}

	driver->cdevs = kcalloc(cdevs, sizeof(*driver->cdevs), GFP_KERNEL);
	if (!driver->cdevs) {
		err = -ENOMEM;
		goto err_free_all;
	}

	return driver;
err_free_all:
	kfree(driver->ports);
	kfree(driver->ttys);
	kfree(driver->termios);
	kfree(driver->cdevs);
	kfree(driver);
	return ERR_PTR(err);
}

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;

struct serial_struct32 {
	compat_int_t    type;
	compat_int_t    line;
	compat_uint_t   port;
	compat_int_t    irq;
	compat_int_t    flags;
	compat_int_t    xmit_fifo_size;
	compat_int_t    custom_divisor;
	compat_int_t    baud_base;
	unsigned short  close_delay;
	char    io_type;
	char    reserved_char;
	compat_int_t    hub6;
	unsigned short  closing_wait; /* time to wait before closing */
	unsigned short  closing_wait2; /* no longer used... */
	compat_uint_t   iomem_base;
	unsigned short  iomem_reg_shift;
	unsigned int    port_high;
	/* compat_ulong_t  iomap_base FIXME */
	compat_int_t    reserved;
}

struct class *tty_class;

static struct cdev tty_cdev, console_cdev;


struct tty_struct *get_current_tty(void)
{
	struct tty_struct *tty;
	unsigned long flags;

	spin_lock_irqsave(&current->sighand->siglock, flags);
	tty = tty_kref_get(current->signal->tty);
	spin_unlock_irqrestore(&current->sighand->siglock, flags);
	return tty;
}


static void tty_write_unlock(struct tty_struct *tty)
{
	mutex_unlock(&tty->atomic_write_lock);
	wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

extern void tty_sysctl_init(void);

static char ptychar[] = "pqrstuvwxyzabcde";


void tty_save_termios(struct tty_struct *tty)
{
	struct ktermios *tp;
	int idx = tty->index;

	/* If the port is going to reset then it has no termios to save */
	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
		return;

	/* Stash the termios data */
	tp = tty->driver->termios[idx];
	if (tp == NULL) {
		tp = kmalloc(sizeof(*tp), GFP_KERNEL);
		if (tp == NULL)
			return;
		tty->driver->termios[idx] = tp;
	}
	*tp = tty->termios;
}


int __init tty_init(void)
{
	tty_sysctl_init();
	cdev_init(&tty_cdev, &tty_fops);
	if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
		panic("Couldn't register /dev/tty driver\n");
	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, "tty");

	cdev_init(&console_cdev, &console_fops);
	if (cdev_add(&console_cdev, MKDEV(TTYAUX_MAJOR, 1), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 1), 1, "/dev/console") < 0)
		panic("Couldn't register /dev/console driver\n");
	consdev = device_create_with_groups(tty_class, NULL,
					    MKDEV(TTYAUX_MAJOR, 1), NULL,
					    cons_dev_groups, "console");
	if (IS_ERR(consdev))
		consdev = NULL;

#ifdef CONFIG_VT
	vty_init(&console_fops);
#endif
	return 0;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

#define tty_compat_ioctl NULL

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

extern void tty_sysctl_init(void);

struct serial_struct32 {
	compat_int_t    type;
	compat_int_t    line;
	compat_uint_t   port;
	compat_int_t    irq;
	compat_int_t    flags;
	compat_int_t    xmit_fifo_size;
	compat_int_t    custom_divisor;
	compat_int_t    baud_base;
	unsigned short  close_delay;
	char    io_type;
	char    reserved_char;
	compat_int_t    hub6;
	unsigned short  closing_wait; /* time to wait before closing */
	unsigned short  closing_wait2; /* no longer used... */
	compat_uint_t   iomem_base;
	unsigned short  iomem_reg_shift;
	unsigned int    port_high;
	/* compat_ulong_t  iomap_base FIXME */
	compat_int_t    reserved;
}

struct class *tty_class;

static struct cdev tty_cdev, console_cdev;

static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);

static struct attribute *cons_dev_attrs[] = {
	&dev_attr_active.attr,
	NULL
};

static struct device *consdev;


void tty_release_struct(struct tty_struct *tty, int idx)
{
	/*
	 * Ask the line discipline code to release its structures
	 */
	tty_ldisc_release(tty);

	/* Wait for pending work before tty destruction commmences */
	tty_flush_works(tty);

	tty_debug_hangup(tty, "freeing structure\n");
	/*
	 * The release_tty function takes care of the details of clearing
	 * the slots and preserving the termios structure.
	 */
	mutex_lock(&tty_mutex);
	release_tty(tty, idx);
	mutex_unlock(&tty_mutex);
}


static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	struct pid *pid;
	int ret;
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	 */
	if (tty == real_tty && current->signal->tty != real_tty)
		return -ENOTTY;
	pid = tty_get_pgrp(real_tty);
	ret =  put_user(pid_vnr(pid), p);
	put_pid(pid);
	return ret;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static unsigned int tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

#define TTY_NUMBER(tty) ((tty)->index + (tty)->driver->name_base)

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

static char ptychar[] = "pqrstuvwxyzabcde";

struct class *tty_class;

static struct cdev tty_cdev, console_cdev;

static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);

static struct attribute *cons_dev_attrs[] = {
	&dev_attr_active.attr,
	NULL
};

static struct device *consdev;


struct tty_struct *tty_kopen(dev_t device)
{
	struct tty_struct *tty;
	struct tty_driver *driver;
	int index = -1;

	mutex_lock(&tty_mutex);
	driver = tty_lookup_driver(device, NULL, &index);
	if (IS_ERR(driver)) {
		mutex_unlock(&tty_mutex);
		return ERR_CAST(driver);
	}

	/* check whether we're reopening an existing tty */
	tty = tty_driver_lookup_tty(driver, NULL, index);
	if (IS_ERR(tty))
		goto out;

	if (tty) {
		/* drop kref from tty_driver_lookup_tty() */
		tty_kref_put(tty);
		tty = ERR_PTR(-EBUSY);
	} else { /* tty_init_dev returns tty with the tty_lock held */
		tty = tty_init_dev(driver, index);
		if (IS_ERR(tty))
			goto out;
		tty_port_set_kopened(tty->port, 1);
	}
out:
	mutex_unlock(&tty_mutex);
	tty_driver_kref_put(driver);
	return tty;
}


int tty_release(struct inode *inode, struct file *filp)
{
	struct tty_struct *tty = file_tty(filp);
	struct tty_struct *o_tty = NULL;
	int	do_sleep, final;
	int	idx;
	long	timeout = 0;
	int	once = 1;

	if (tty_paranoia_check(tty, inode, __func__))
		return 0;

	tty_lock(tty);
	check_tty_count(tty, __func__);

	__tty_fasync(-1, filp, 0);

	idx = tty->index;
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		o_tty = tty->link;

	if (tty_release_checks(tty, idx)) {
		tty_unlock(tty);
		return 0;
	}

	tty_debug_hangup(tty, "releasing (count=%d)\n", tty->count);

	if (tty->ops->close)
		tty->ops->close(tty, filp);

	/* If tty is pty master, lock the slave pty (stable lock order) */
	tty_lock_slave(o_tty);

	/*
	 * Sanity check: if tty->count is going to zero, there shouldn't be
	 * any waiters on tty->read_wait or tty->write_wait.  We test the
	 * wait queues and kick everyone out _before_ actually starting to
	 * close.  This ensures that we won't block while releasing the tty
	 * structure.
	 *
	 * The test for the o_tty closing is necessary, since the master and
	 * slave sides may close in any order.  If the slave side closes out
	 * first, its count will be one, since the master side holds an open.
	 * Thus this test wouldn't be triggered at the time the slave closed,
	 * so we do it now.
	 */
	while (1) {
		do_sleep = 0;

		if (tty->count <= 1) {
			if (waitqueue_active(&tty->read_wait)) {
				wake_up_poll(&tty->read_wait, EPOLLIN);
				do_sleep++;
			}
			if (waitqueue_active(&tty->write_wait)) {
				wake_up_poll(&tty->write_wait, EPOLLOUT);
				do_sleep++;
			}
		}
		if (o_tty && o_tty->count <= 1) {
			if (waitqueue_active(&o_tty->read_wait)) {
				wake_up_poll(&o_tty->read_wait, EPOLLIN);
				do_sleep++;
			}
			if (waitqueue_active(&o_tty->write_wait)) {
				wake_up_poll(&o_tty->write_wait, EPOLLOUT);
				do_sleep++;
			}
		}
		if (!do_sleep)
			break;

		if (once) {
			once = 0;
			tty_warn(tty, "read/write wait queue active!\n");
		}
		schedule_timeout_killable(timeout);
		if (timeout < 120 * HZ)
			timeout = 2 * timeout + 1;
		else
			timeout = MAX_SCHEDULE_TIMEOUT;
	}

	if (o_tty) {
		if (--o_tty->count < 0) {
			tty_warn(tty, "bad slave count (%d)\n", o_tty->count);
			o_tty->count = 0;
		}
	}
	if (--tty->count < 0) {
		tty_warn(tty, "bad tty->count (%d)\n", tty->count);
		tty->count = 0;
	}

	/*
	 * We've decremented tty->count, so we need to remove this file
	 * descriptor off the tty->tty_files list; this serves two
	 * purposes:
	 *  - check_tty_count sees the correct number of file descriptors
	 *    associated with this tty.
	 *  - do_tty_hangup no longer sees this file descriptor as
	 *    something that needs to be handled for hangups.
	 */
	tty_del_file(filp);

	/*
	 * Perform some housekeeping before deciding whether to return.
	 *
	 * If _either_ side is closing, make sure there aren't any
	 * processes that still think tty or o_tty is their controlling
	 * tty.
	 */
	if (!tty->count) {
		read_lock(&tasklist_lock);
		session_clear_tty(tty->session);
		if (o_tty)
			session_clear_tty(o_tty->session);
		read_unlock(&tasklist_lock);
	}

	/* check whether both sides are closing ... */
	final = !tty->count && !(o_tty && o_tty->count);

	tty_unlock_slave(o_tty);
	tty_unlock(tty);

	/* At this point, the tty->count == 0 should ensure a dead tty
	   cannot be re-opened by a racing opener */

	if (!final)
		return 0;

	tty_debug_hangup(tty, "final close\n");

	tty_release_struct(tty, idx);
	return 0;
}


static void __tty_hangup(struct tty_struct *tty, int exit_session)
{
	struct file *cons_filp = NULL;
	struct file *filp, *f = NULL;
	struct tty_file_private *priv;
	int    closecount = 0, n;
	int refs;

	if (!tty)
		return;

	spin_lock(&redirect_lock);
	if (redirect && file_tty(redirect) == tty) {
		f = redirect;
		redirect = NULL;
	}
	spin_unlock(&redirect_lock);

	tty_lock(tty);

	if (test_bit(TTY_HUPPED, &tty->flags)) {
		tty_unlock(tty);
		return;
	}

	/*
	 * Some console devices aren't actually hung up for technical and
	 * historical reasons, which can lead to indefinite interruptible
	 * sleep in n_tty_read().  The following explicitly tells
	 * n_tty_read() to abort readers.
	 */
	set_bit(TTY_HUPPING, &tty->flags);

	/* inuse_filps is protected by the single tty lock,
	   this really needs to change if we want to flush the
	   workqueue with the lock held */
	check_tty_count(tty, "tty_hangup");

	spin_lock(&tty->files_lock);
	/* This breaks for file handles being sent over AF_UNIX sockets ? */
	list_for_each_entry(priv, &tty->tty_files, list) {
		filp = priv->file;
		if (filp->f_op->write == redirected_tty_write)
			cons_filp = filp;
		if (filp->f_op->write != tty_write)
			continue;
		closecount++;
		__tty_fasync(-1, filp, 0);	/* can't block */
		filp->f_op = &hung_up_tty_fops;
	}
	spin_unlock(&tty->files_lock);

	refs = tty_signal_session_leader(tty, exit_session);
	/* Account for the p->signal references we killed */
	while (refs--)
		tty_kref_put(tty);

	tty_ldisc_hangup(tty, cons_filp != NULL);

	spin_lock_irq(&tty->ctrl_lock);
	clear_bit(TTY_THROTTLED, &tty->flags);
	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
	put_pid(tty->session);
	put_pid(tty->pgrp);
	tty->session = NULL;
	tty->pgrp = NULL;
	tty->ctrl_status = 0;
	spin_unlock_irq(&tty->ctrl_lock);

	/*
	 * If one of the devices matches a console pointer, we
	 * cannot just call hangup() because that will cause
	 * tty->count and state->count to go out of sync.
	 * So we just call close() the right number of times.
	 */
	if (cons_filp) {
		if (tty->ops->close)
			for (n = 0; n < closecount; n++)
				tty->ops->close(tty, cons_filp);
	} else if (tty->ops->hangup)
		tty->ops->hangup(tty);
	/*
	 * We don't want to have driver/ldisc interactions beyond the ones
	 * we did here. The driver layer expects no calls after ->hangup()
	 * from the ldisc side, which is now guaranteed.
	 */
	set_bit(TTY_HUPPED, &tty->flags);
	clear_bit(TTY_HUPPING, &tty->flags);
	tty_unlock(tty);

	if (f)
		fput(f);
}


void start_tty(struct tty_struct *tty)
{
	unsigned long flags;

	spin_lock_irqsave(&tty->flow_lock, flags);
	__start_tty(tty);
	spin_unlock_irqrestore(&tty->flow_lock, flags);
}


static int tty_tiocmget(struct tty_struct *tty, int __user *p)
{
	int retval = -EINVAL;

	if (tty->ops->tiocmget) {
		retval = tty->ops->tiocmget(tty);

		if (retval >= 0)
			retval = put_user(retval, p);
	}
	return retval;
}


static int hung_up_tty_fasync(int fd, struct file *file, int on)
{
	return -ENOTTY;
}


int tty_standard_install(struct tty_driver *driver, struct tty_struct *tty)
{
	tty_init_termios(tty);
	tty_driver_kref_get(driver);
	tty->count++;
	driver->ttys[tty->index] = tty;
	return 0;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static struct file *redirect;


void tty_vhangup_session(struct tty_struct *tty)
{
	tty_debug_hangup(tty, "session hangup\n");
	__tty_hangup(tty, 1);
}


static struct tty_struct *tty_pair_get_tty(struct tty_struct *tty)
{
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		tty = tty->link;
	return tty;
}


void proc_clear_tty(struct task_struct *p)
{
	unsigned long flags;
	struct tty_struct *tty;
	spin_lock_irqsave(&p->sighand->siglock, flags);
	tty = p->signal->tty;
	p->signal->tty = NULL;
	spin_unlock_irqrestore(&p->sighand->siglock, flags);
	tty_kref_put(tty);
}


static long hung_up_tty_compat_ioctl(struct file *file,
				     unsigned int cmd, unsigned long arg)
{
	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}


static void tty_update_time(struct timespec64 *time)
{
	time64_t sec = ktime_get_real_seconds();

	/*
	 * We only care if the two values differ in anything other than the
	 * lower three bits (i.e every 8 seconds).  If so, then we can update
	 * the time of the tty device, otherwise it could be construded as a
	 * security leak to let userspace know the exact timing of the tty.
	 */
	if ((sec ^ time->tv_sec) & ~7)
		time->tv_sec = sec;
}


void tty_kclose(struct tty_struct *tty)
{
	/*
	 * Ask the line discipline code to release its structures
	 */
	tty_ldisc_release(tty);

	/* Wait for pending work before tty destruction commmences */
	tty_flush_works(tty);

	tty_debug_hangup(tty, "freeing structure\n");
	/*
	 * The release_tty function takes care of the details of clearing
	 * the slots and preserving the termios structure.
	 */
	mutex_lock(&tty_mutex);
	tty_port_set_kopened(tty->port, 0);
	release_tty(tty, tty->index);
	mutex_unlock(&tty_mutex);
}


void __stop_tty(struct tty_struct *tty)
{
	if (tty->stopped)
		return;
	tty->stopped = 1;
	if (tty->ops->stop)
		tty->ops->stop(tty);
}


long tty_jobctrl_ioctl(struct tty_struct *tty, struct tty_struct *real_tty,
		       struct file *file, unsigned int cmd, unsigned long arg)
{
	void __user *p = (void __user *)arg;

	switch (cmd) {
	case TIOCNOTTY:
		if (current->signal->tty != tty)
			return -ENOTTY;
		no_tty();
		return 0;
	case TIOCSCTTY:
		return tiocsctty(real_tty, file, arg);
	case TIOCGPGRP:
		return tiocgpgrp(tty, real_tty, p);
	case TIOCSPGRP:
		return tiocspgrp(tty, real_tty, p);
	case TIOCGSID:
		return tiocgsid(tty, real_tty, p);
	}
	return -ENOIOCTLCMD;
}


void tty_free_file(struct file *file)
{
	struct tty_file_private *priv = file->private_data;

	file->private_data = NULL;
	kfree(priv);
}


static int tty_open(struct inode *inode, struct file *filp)
{
	struct tty_struct *tty;
	int noctty, retval;
	dev_t device = inode->i_rdev;
	unsigned saved_flags = filp->f_flags;

	nonseekable_open(inode, filp);

retry_open:
	retval = tty_alloc_file(filp);
	if (retval)
		return -ENOMEM;

	tty = tty_open_current_tty(device, filp);
	if (!tty)
		tty = tty_open_by_driver(device, filp);

	if (IS_ERR(tty)) {
		tty_free_file(filp);
		retval = PTR_ERR(tty);
		if (retval != -EAGAIN || signal_pending(current))
			return retval;
		schedule();
		goto retry_open;
	}

	tty_add_file(tty, filp);

	check_tty_count(tty, __func__);
	tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);

	if (tty->ops->open)
		retval = tty->ops->open(tty, filp);
	else
		retval = -ENODEV;
	filp->f_flags = saved_flags;

	if (retval) {
		tty_debug_hangup(tty, "open error %d, releasing\n", retval);

		tty_unlock(tty); /* need to call tty_release without BTM */
		tty_release(inode, filp);
		if (retval != -ERESTARTSYS)
			return retval;

		if (signal_pending(current))
			return retval;

		schedule();
		/*
		 * Need to reset f_op in case a hangup happened.
		 */
		if (tty_hung_up_p(filp))
			filp->f_op = &tty_fops;
		goto retry_open;
	}
	clear_bit(TTY_HUPPED, &tty->flags);

	noctty = (filp->f_flags & O_NOCTTY) ||
		 (IS_ENABLED(CONFIG_VT) && device == MKDEV(TTY_MAJOR, 0)) ||
		 device == MKDEV(TTYAUX_MAJOR, 1) ||
		 (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
		  tty->driver->subtype == PTY_TYPE_MASTER);
	if (!noctty)
		tty_open_proc_set_tty(filp, tty);
	tty_unlock(tty);
	return 0;
}


struct device *tty_register_device(struct tty_driver *driver, unsigned index,
				   struct device *device)
{
	return tty_register_device_attr(driver, index, device, NULL, NULL);
}


static struct tty_driver *get_tty_driver(dev_t device, int *index)
{
	struct tty_driver *p;

	list_for_each_entry(p, &tty_drivers, tty_drivers) {
		dev_t base = MKDEV(p->major, p->minor_start);
		if (device < base || device >= base + p->num)
			continue;
		*index = device - base;
		return tty_driver_kref_get(p);
	}
	return NULL;
}


static int tty_tiocsserial(struct tty_struct *tty, struct serial_struct __user *ss)
{
	static DEFINE_RATELIMIT_STATE(depr_flags,
			DEFAULT_RATELIMIT_INTERVAL,
			DEFAULT_RATELIMIT_BURST);
	char comm[TASK_COMM_LEN];
	struct serial_struct v;
	int flags;

	if (copy_from_user(&v, ss, sizeof(*ss)))
		return -EFAULT;

	flags = v.flags & ASYNC_DEPRECATED;

	if (flags && __ratelimit(&depr_flags))
		pr_warn("%s: '%s' is using deprecated serial flags (with no effect): %.8x\n",
			__func__, get_task_comm(comm, current), flags);
	if (!tty->ops->set_serial)
		return -ENOTTY;
	return tty->ops->set_serial(tty, &v);
}


static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
			loff_t *ppos)
{
	int i;
	struct inode *inode = file_inode(file);
	struct tty_struct *tty = file_tty(file);
	struct tty_ldisc *ld;

	if (tty_paranoia_check(tty, inode, "tty_read"))
		return -EIO;
	if (!tty || tty_io_error(tty))
		return -EIO;

	/* We want to wait for the line discipline to sort out in this
	   situation */
	ld = tty_ldisc_ref_wait(tty);
	if (!ld)
		return hung_up_tty_read(file, buf, count, ppos);
	if (ld->ops->read)
		i = ld->ops->read(tty, file, buf, count);
	else
		i = -EIO;
	tty_ldisc_deref(ld);

	if (i > 0)
		tty_update_time(&inode->i_atime);

	return i;
}


static int send_break(struct tty_struct *tty, unsigned int duration)
{
	int retval;

	if (tty->ops->break_ctl == NULL)
		return 0;

	if (tty->driver->flags & TTY_DRIVER_HARDWARE_BREAK)
		retval = tty->ops->break_ctl(tty, duration);
	else {
		/* Do the work ourselves */
		if (tty_write_lock(tty, 0) < 0)
			return -EINTR;
		retval = tty->ops->break_ctl(tty, -1);
		if (retval)
			goto out;
		if (!signal_pending(current))
			msleep_interruptible(duration);
		retval = tty->ops->break_ctl(tty, 0);
out:
		tty_write_unlock(tty);
		if (signal_pending(current))
			retval = -EINTR;
	}
	return retval;
}


int tty_send_xchar(struct tty_struct *tty, char ch)
{
	int	was_stopped = tty->stopped;

	if (tty->ops->send_xchar) {
		down_read(&tty->termios_rwsem);
		tty->ops->send_xchar(tty, ch);
		up_read(&tty->termios_rwsem);
		return 0;
	}

	if (tty_write_lock(tty, 0) < 0)
		return -ERESTARTSYS;

	down_read(&tty->termios_rwsem);
	if (was_stopped)
		start_tty(tty);
	tty->ops->write(tty, &ch, 1);
	if (was_stopped)
		stop_tty(tty);
	up_read(&tty->termios_rwsem);
	tty_write_unlock(tty);
	return 0;
}


void tty_write_message(struct tty_struct *tty, char *msg)
{
	if (tty) {
		mutex_lock(&tty->atomic_write_lock);
		tty_lock(tty);
		if (tty->ops->write && tty->count > 0)
			tty->ops->write(tty, msg, strlen(msg));
		tty_unlock(tty);
		tty_write_unlock(tty);
	}
	return;
}


void tty_hangup(struct tty_struct *tty)
{
	tty_debug_hangup(tty, "hangup\n");
	schedule_work(&tty->hangup_work);
}


int tty_hung_up_p(struct file *filp)
{
	return (filp && filp->f_op == &hung_up_tty_fops);
}


static ssize_t tty_line_name(struct tty_driver *driver, int index, char *p)
{
	if (driver->flags & TTY_DRIVER_UNNUMBERED_NODE)
		return sprintf(p, "%s", driver->name);
	else
		return sprintf(p, "%s%d", driver->name,
			       index + driver->name_base);
}


static int check_tty_count(struct tty_struct *tty, const char *routine)
{
#ifdef CHECK_TTY_COUNT
	struct list_head *p;
	int count = 0, kopen_count = 0;

	spin_lock(&tty->files_lock);
	list_for_each(p, &tty->tty_files) {
		count++;
	}
	spin_unlock(&tty->files_lock);
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_SLAVE &&
	    tty->link && tty->link->count)
		count++;
	if (tty_port_kopened(tty->port))
		kopen_count++;
	if (tty->count != (count + kopen_count)) {
		tty_warn(tty, "%s: tty->count(%d) != (#fd's(%d) + #kopen's(%d))\n",
			 routine, tty->count, count, kopen_count);
		return (count + kopen_count);
	}
#endif
	return 0;
}

# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)

# define tty_debug_hangup(tty, f, args...)	do { } while (0)

#define CHECK_TTY_COUNT 1

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400,
	/* .c_line = N_TTY, */
};

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);

static __poll_t tty_poll(struct file *, poll_table *);

static int tty_open(struct inode *, struct file *);

long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);

static int __tty_fasync(int fd, struct file *filp, int on);

static int tty_fasync(int fd, struct file *filp, int on);

static void release_tty(struct tty_struct *tty, int idx);

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
	.show_fdinfo	= tty_show_fdinfo,
};

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
	.fasync		= hung_up_tty_fasync,
};

static DEFINE_SPINLOCK(redirect_lock);

static struct file *redirect;

static char ptychar[] = "pqrstuvwxyzabcde";


static int tty_release_checks(struct tty_struct *tty, int idx)
{
#ifdef TTY_PARANOIA_CHECK
	if (idx < 0 || idx >= tty->driver->num) {
		tty_debug(tty, "bad idx %d\n", idx);
		return -1;
	}

	/* not much to check for devpts */
	if (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)
		return 0;

	if (tty != tty->driver->ttys[idx]) {
		tty_debug(tty, "bad driver table[%d] = %p\n",
			  idx, tty->driver->ttys[idx]);
		return -1;
	}
	if (tty->driver->other) {
		struct tty_struct *o_tty = tty->link;

		if (o_tty != tty->driver->other->ttys[idx]) {
			tty_debug(tty, "bad other table[%d] = %p\n",
				  idx, tty->driver->other->ttys[idx]);
			return -1;
		}
		if (o_tty->link != tty) {
			tty_debug(tty, "bad link = %p\n", o_tty->link);
			return -1;
		}
	}
#endif
	return 0;
}


static int __tty_fasync(int fd, struct file *filp, int on)
{
	struct tty_struct *tty = file_tty(filp);
	unsigned long flags;
	int retval = 0;

	if (tty_paranoia_check(tty, file_inode(filp), "tty_fasync"))
		goto out;

	retval = fasync_helper(fd, filp, on, &tty->fasync);
	if (retval <= 0)
		goto out;

	if (on) {
		enum pid_type type;
		struct pid *pid;

		spin_lock_irqsave(&tty->ctrl_lock, flags);
		if (tty->pgrp) {
			pid = tty->pgrp;
			type = PIDTYPE_PGID;
		} else {
			pid = task_pid(current);
			type = PIDTYPE_TGID;
		}
		get_pid(pid);
		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
		__f_setown(filp, pid, type, 0);
		put_pid(pid);
		retval = 0;
	}
out:
	return retval;
}


static int tty_reopen(struct tty_struct *tty)
{
	struct tty_driver *driver = tty->driver;
	struct tty_ldisc *ld;
	int retval = 0;

	if (driver->type == TTY_DRIVER_TYPE_PTY &&
	    driver->subtype == PTY_TYPE_MASTER)
		return -EIO;

	if (!tty->count)
		return -EAGAIN;

	if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
		return -EBUSY;

	ld = tty_ldisc_ref_wait(tty);
	if (ld) {
		tty_ldisc_deref(ld);
	} else {
		retval = tty_ldisc_lock(tty, 5 * HZ);
		if (retval)
			return retval;

		if (!tty->ldisc)
			retval = tty_ldisc_reinit(tty, tty->termios.c_line);
		tty_ldisc_unlock(tty);
	}

	if (retval == 0)
		tty->count++;

	return retval;
}


int tty_check_change(struct tty_struct *tty)
{
	return __tty_check_change(tty, SIGTTOU);
}