Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3608 insertions, 0 deletions

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
new file mode 100644
index 000000000..aaf77a561
--- /dev/null
+++ b/drivers/tty/tty_io.c
@@ -0,0 +1,3608 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+/*
+ * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
+ * or rs-channels. It also implements echoing, cooked mode etc.
+ *
+ * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
+ *
+ * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
+ * tty_struct and tty_queue structures.  Previously there was an array
+ * of 256 tty_struct's which was statically allocated, and the
+ * tty_queue structures were allocated at boot time.  Both are now
+ * dynamically allocated only when the tty is open.
+ *
+ * Also restructured routines so that there is more of a separation
+ * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
+ * the low-level tty routines (serial.c, pty.c, console.c).  This
+ * makes for cleaner and more compact code.  -TYT, 9/17/92
+ *
+ * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
+ * which can be dynamically activated and de-activated by the line
+ * discipline handling modules (like SLIP).
+ *
+ * NOTE: pay no attention to the line discipline code (yet); its
+ * interface is still subject to change in this version...
+ * -- TYT, 1/31/92
+ *
+ * Added functionality to the OPOST tty handling.  No delays, but all
+ * other bits should be there.
+ *	-- Nick Holloway <alfie@dcs.warwick.ac.uk>, 27th May 1993.
+ *
+ * Rewrote canonical mode and added more termios flags.
+ *	-- julian@uhunix.uhcc.hawaii.edu (J. Cowley), 13Jan94
+ *
+ * Reorganized FASYNC support so mouse code can share it.
+ *	-- ctm@ardi.com, 9Sep95
+ *
+ * New TIOCLINUX variants added.
+ *	-- mj@k332.feld.cvut.cz, 19-Nov-95
+ *
+ * Restrict vt switching via ioctl()
+ *      -- grif@cs.ucr.edu, 5-Dec-95
+ *
+ * Move console and virtual terminal code to more appropriate files,
+ * implement CONFIG_VT and generalize console device interface.
+ *	-- Marko Kohtala <Marko.Kohtala@hut.fi>, March 97
+ *
+ * Rewrote tty_init_dev and tty_release_dev to eliminate races.
+ *	-- Bill Hawes <whawes@star.net>, June 97
+ *
+ * Added devfs support.
+ *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 13-Jan-1998
+ *
+ * Added support for a Unix98-style ptmx device.
+ *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
+ *
+ * Reduced memory usage for older ARM systems
+ *      -- Russell King <rmk@arm.linux.org.uk>
+ *
+ * Move do_SAK() into process context.  Less stack use in devfs functions.
+ * alloc_tty_struct() always uses kmalloc()
+ *			 -- Andrew Morton <andrewm@uow.edu.eu> 17Mar01
+ */
+
+#include <linux/types.h>
+#include <linux/major.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/fcntl.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/devpts_fs.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/console.h>
+#include <linux/timer.h>
+#include <linux/ctype.h>
+#include <linux/kd.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/ppp-ioctl.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/seq_file.h>
+#include <linux/serial.h>
+#include <linux/ratelimit.h>
+#include <linux/compat.h>
+#include <linux/uaccess.h>
+#include <linux/termios_internal.h>
+
+#include <linux/kbd_kern.h>
+#include <linux/vt_kern.h>
+#include <linux/selection.h>
+
+#include <linux/kmod.h>
+#include <linux/nsproxy.h>
+#include "tty.h"
+
+#undef TTY_DEBUG_HANGUP
+#ifdef TTY_DEBUG_HANGUP
+# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)
+#else
+# define tty_debug_hangup(tty, f, args...)	do { } while (0)
+#endif
+
+#define TTY_PARANOIA_CHECK 1
+#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, */
+};
+EXPORT_SYMBOL(tty_std_termios);
+
+/* This list gets poked at by procfs and various bits of boot up code. This
+ * could do with some rationalisation such as pulling the tty proc function
+ * into this file.
+ */
+
+LIST_HEAD(tty_drivers);			/* linked list of tty drivers */
+
+/* Mutex to protect creating and releasing a tty */
+DEFINE_MUTEX(tty_mutex);
+
+static ssize_t tty_read(struct kiocb *, struct iov_iter *);
+static ssize_t tty_write(struct kiocb *, struct iov_iter *);
+static __poll_t tty_poll(struct file *, poll_table *);
+static int tty_open(struct inode *, struct file *);
+#ifdef CONFIG_COMPAT
+static long tty_compat_ioctl(struct file *file, unsigned int cmd,
+				unsigned long arg);
+#else
+#define tty_compat_ioctl NULL
+#endif
+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);
+
+/**
+ * free_tty_struct	-	free a disused tty
+ * @tty: tty struct to free
+ *
+ * Free the write buffers, tty queue and tty memory itself.
+ *
+ * Locking: none. Must be called after tty is definitely unused
+ */
+static void free_tty_struct(struct tty_struct *tty)
+{
+	tty_ldisc_deinit(tty);
+	put_device(tty->dev);
+	kvfree(tty->write_buf);
+	kfree(tty);
+}
+
+static inline struct tty_struct *file_tty(struct file *file)
+{
+	return ((struct tty_file_private *)file->private_data)->tty;
+}
+
+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;
+}
+
+/* Associate a new file with the tty structure */
+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);
+}
+
+/**
+ * tty_free_file - free file->private_data
+ * @file: to free private_data of
+ *
+ * This shall be used only for fail path handling when tty_add_file was not
+ * called yet.
+ */
+void tty_free_file(struct file *file)
+{
+	struct tty_file_private *priv = file->private_data;
+
+	file->private_data = NULL;
+	kfree(priv);
+}
+
+/* Delete file from its tty */
+static void tty_del_file(struct file *file)
+{
+	struct tty_file_private *priv = file->private_data;
+	struct tty_struct *tty = priv->tty;
+
+	spin_lock(&tty->files_lock);
+	list_del(&priv->list);
+	spin_unlock(&tty->files_lock);
+	tty_free_file(file);
+}
+
+/**
+ * tty_name	-	return tty naming
+ * @tty: tty structure
+ *
+ * Convert a tty structure into a name. The name reflects the kernel naming
+ * policy and if udev is in use may not reflect user space
+ *
+ * Locking: none
+ */
+const char *tty_name(const struct tty_struct *tty)
+{
+	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
+		return "NULL tty";
+	return tty->name;
+}
+EXPORT_SYMBOL(tty_name);
+
+const char *tty_driver_name(const struct tty_struct *tty)
+{
+	if (!tty || !tty->driver)
+		return "";
+	return tty->driver->name;
+}
+
+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;
+	}
+#endif
+	return 0;
+}
+
+/* Caller must hold tty_lock */
+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;
+}
+
+/**
+ * get_tty_driver		-	find device of a tty
+ * @device: device identifier
+ * @index: returns the index of the tty
+ *
+ * This routine returns a tty driver structure, given a device number and also
+ * passes back the index number.
+ *
+ * Locking: caller must hold tty_mutex
+ */
+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;
+}
+
+/**
+ * tty_dev_name_to_number	-	return dev_t for device name
+ * @name: user space name of device under /dev
+ * @number: pointer to dev_t that this function will populate
+ *
+ * This function converts device names like ttyS0 or ttyUSB1 into dev_t like
+ * (4, 64) or (188, 1). If no corresponding driver is registered then the
+ * function returns -%ENODEV.
+ *
+ * Locking: this acquires tty_mutex to protect the tty_drivers list from
+ *	being modified while we are traversing it, and makes sure to
+ *	release it before exiting.
+ */
+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;
+}
+EXPORT_SYMBOL_GPL(tty_dev_name_to_number);
+
+#ifdef CONFIG_CONSOLE_POLL
+
+/**
+ * tty_find_polling_driver	-	find device of a polled tty
+ * @name: name string to match
+ * @line: pointer to resulting tty line nr
+ *
+ * This routine returns a tty driver structure, given a name and the condition
+ * that the tty driver is capable of polled operation.
+ */
+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;
+}
+EXPORT_SYMBOL_GPL(tty_find_polling_driver);
+#endif
+
+static ssize_t hung_up_tty_read(struct kiocb *iocb, struct iov_iter *to)
+{
+	return 0;
+}
+
+static ssize_t hung_up_tty_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	return -EIO;
+}
+
+/* No kernel lock held - none needed ;) */
+static __poll_t hung_up_tty_poll(struct file *filp, poll_table *wait)
+{
+	return EPOLLIN | EPOLLOUT | EPOLLERR | EPOLLHUP | EPOLLRDNORM | EPOLLWRNORM;
+}
+
+static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
+		unsigned long arg)
+{
+	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
+}
+
+static long hung_up_tty_compat_ioctl(struct file *file,
+				     unsigned int cmd, unsigned long arg)
+{
+	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
+}
+
+static int hung_up_tty_fasync(int fd, struct file *file, int on)
+{
+	return -ENOTTY;
+}
+
+static void tty_show_fdinfo(struct seq_file *m, struct file *file)
+{
+	struct tty_struct *tty = file_tty(file);
+
+	if (tty && tty->ops && tty->ops->show_fdinfo)
+		tty->ops->show_fdinfo(tty, m);
+}
+
+static const struct file_operations tty_fops = {
+	.llseek		= no_llseek,
+	.read_iter	= tty_read,
+	.write_iter	= tty_write,
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_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_iter	= tty_read,
+	.write_iter	= redirected_tty_write,
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_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_iter	= hung_up_tty_read,
+	.write_iter	= 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;
+
+/**
+ * tty_wakeup	-	request more data
+ * @tty: terminal
+ *
+ * Internal and external helper for wakeups of tty. This function informs the
+ * line discipline if present that the driver is ready to receive more output
+ * data.
+ */
+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);
+}
+EXPORT_SYMBOL_GPL(tty_wakeup);
+
+/**
+ * tty_release_redirect	-	Release a redirect on a pty if present
+ * @tty: tty device
+ *
+ * This is available to the pty code so if the master closes, if the slave is a
+ * redirect it can release the redirect.
+ */
+static struct file *tty_release_redirect(struct tty_struct *tty)
+{
+	struct file *f = NULL;
+
+	spin_lock(&redirect_lock);
+	if (redirect && file_tty(redirect) == tty) {
+		f = redirect;
+		redirect = NULL;
+	}
+	spin_unlock(&redirect_lock);
+
+	return f;
+}
+
+/**
+ * __tty_hangup		-	actual handler for hangup events
+ * @tty: tty device
+ * @exit_session: if non-zero, signal all foreground group processes
+ *
+ * This can be called by a "kworker" kernel thread. That is process synchronous
+ * but doesn't hold any locks, so we need to make sure we have the appropriate
+ * locks for what we're doing.
+ *
+ * The hangup event clears any pending redirections onto the hung up device. It
+ * ensures future writes will error and it does the needed line discipline
+ * hangup and signal delivery. The tty object itself remains intact.
+ *
+ * Locking:
+ *  * BTM
+ *
+ *   * redirect lock for undoing redirection
+ *   * file list lock for manipulating list of ttys
+ *   * tty_ldiscs_lock from called functions
+ *   * termios_rwsem resetting termios data
+ *   * tasklist_lock to walk task list for hangup event
+ *
+ *    * ->siglock to protect ->signal/->sighand
+ *
+ */
+static void __tty_hangup(struct tty_struct *tty, int exit_session)
+{
+	struct file *cons_filp = NULL;
+	struct file *filp, *f;
+	struct tty_file_private *priv;
+	int    closecount = 0, n;
+	int refs;
+
+	if (!tty)
+		return;
+
+	f = tty_release_redirect(tty);
+
+	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_iter == redirected_tty_write)
+			cons_filp = filp;
+		if (filp->f_op->write_iter != 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->ctrl.session);
+	put_pid(tty->ctrl.pgrp);
+	tty->ctrl.session = NULL;
+	tty->ctrl.pgrp = NULL;
+	tty->ctrl.pktstatus = 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);
+}
+
+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);
+}
+
+/**
+ * tty_hangup		-	trigger a hangup event
+ * @tty: tty to hangup
+ *
+ * A carrier loss (virtual or otherwise) has occurred on @tty. Schedule a
+ * hangup sequence to run after this event.
+ */
+void tty_hangup(struct tty_struct *tty)
+{
+	tty_debug_hangup(tty, "hangup\n");
+	schedule_work(&tty->hangup_work);
+}
+EXPORT_SYMBOL(tty_hangup);
+
+/**
+ * tty_vhangup		-	process vhangup
+ * @tty: tty to hangup
+ *
+ * The user has asked via system call for the terminal to be hung up. We do
+ * this synchronously so that when the syscall returns the process is complete.
+ * That guarantee is necessary for security reasons.
+ */
+void tty_vhangup(struct tty_struct *tty)
+{
+	tty_debug_hangup(tty, "vhangup\n");
+	__tty_hangup(tty, 0);
+}
+EXPORT_SYMBOL(tty_vhangup);
+
+
+/**
+ * tty_vhangup_self	-	process vhangup for own ctty
+ *
+ * Perform a vhangup on the current controlling tty
+ */
+void tty_vhangup_self(void)
+{
+	struct tty_struct *tty;
+
+	tty = get_current_tty();
+	if (tty) {
+		tty_vhangup(tty);
+		tty_kref_put(tty);
+	}
+}
+
+/**
+ * tty_vhangup_session	-	hangup session leader exit
+ * @tty: tty to hangup
+ *
+ * The session leader is exiting and hanging up its controlling terminal.
+ * Every process in the foreground process group is signalled %SIGHUP.
+ *
+ * We do this synchronously so that when the syscall returns the process is
+ * complete. That guarantee is necessary for security reasons.
+ */
+void tty_vhangup_session(struct tty_struct *tty)
+{
+	tty_debug_hangup(tty, "session hangup\n");
+	__tty_hangup(tty, 1);
+}
+
+/**
+ * tty_hung_up_p	-	was tty hung up
+ * @filp: file pointer of tty
+ *
+ * Return: true if the tty has been subject to a vhangup or a carrier loss
+ */
+int tty_hung_up_p(struct file *filp)
+{
+	return (filp && filp->f_op == &hung_up_tty_fops);
+}
+EXPORT_SYMBOL(tty_hung_up_p);
+
+void __stop_tty(struct tty_struct *tty)
+{
+	if (tty->flow.stopped)
+		return;
+	tty->flow.stopped = true;
+	if (tty->ops->stop)
+		tty->ops->stop(tty);
+}
+
+/**
+ * stop_tty	-	propagate flow control
+ * @tty: tty to stop
+ *
+ * Perform flow control to the driver. May be called on an already stopped
+ * device and will not re-call the &tty_driver->stop() method.
+ *
+ * This functionality is used by both the line disciplines for halting incoming
+ * flow and by the driver. It may therefore be called from any context, may be
+ * under the tty %atomic_write_lock but not always.
+ *
+ * Locking:
+ *	flow.lock
+ */
+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);
+}
+EXPORT_SYMBOL(stop_tty);
+
+void __start_tty(struct tty_struct *tty)
+{
+	if (!tty->flow.stopped || tty->flow.tco_stopped)
+		return;
+	tty->flow.stopped = false;
+	if (tty->ops->start)
+		tty->ops->start(tty);
+	tty_wakeup(tty);
+}
+
+/**
+ * start_tty	-	propagate flow control
+ * @tty: tty to start
+ *
+ * Start a tty that has been stopped if at all possible. If @tty was previously
+ * stopped and is now being started, the &tty_driver->start() method is invoked
+ * and the line discipline woken.
+ *
+ * Locking:
+ *	flow.lock
+ */
+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);
+}
+EXPORT_SYMBOL(start_tty);
+
+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;
+}
+
+/*
+ * Iterate on the ldisc ->read() function until we've gotten all
+ * the data the ldisc has for us.
+ *
+ * The "cookie" is something that the ldisc read function can fill
+ * in to let us know that there is more data to be had.
+ *
+ * We promise to continue to call the ldisc until it stops returning
+ * data or clears the cookie. The cookie may be something that the
+ * ldisc maintains state for and needs to free.
+ */
+static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty,
+		struct file *file, struct iov_iter *to)
+{
+	int retval = 0;
+	void *cookie = NULL;
+	unsigned long offset = 0;
+	char kernel_buf[64];
+	size_t count = iov_iter_count(to);
+
+	do {
+		int size, copied;
+
+		size = count > sizeof(kernel_buf) ? sizeof(kernel_buf) : count;
+		size = ld->ops->read(tty, file, kernel_buf, size, &cookie, offset);
+		if (!size)
+			break;
+
+		if (size < 0) {
+			/* Did we have an earlier error (ie -EFAULT)? */
+			if (retval)
+				break;
+			retval = size;
+
+			/*
+			 * -EOVERFLOW means we didn't have enough space
+			 * for a whole packet, and we shouldn't return
+			 * a partial result.
+			 */
+			if (retval == -EOVERFLOW)
+				offset = 0;
+			break;
+		}
+
+		copied = copy_to_iter(kernel_buf, size, to);
+		offset += copied;
+		count -= copied;
+
+		/*
+		 * If the user copy failed, we still need to do another ->read()
+		 * call if we had a cookie to let the ldisc clear up.
+		 *
+		 * But make sure size is zeroed.
+		 */
+		if (unlikely(copied != size)) {
+			count = 0;
+			retval = -EFAULT;
+		}
+	} while (cookie);
+
+	/* We always clear tty buffer in case they contained passwords */
+	memzero_explicit(kernel_buf, sizeof(kernel_buf));
+	return offset ? offset : retval;
+}
+
+
+/**
+ * tty_read	-	read method for tty device files
+ * @iocb: kernel I/O control block
+ * @to: destination for the data read
+ *
+ * Perform the read system call function on this terminal device. Checks
+ * for hung up devices before calling the line discipline method.
+ *
+ * Locking:
+ *	Locks the line discipline internally while needed. Multiple read calls
+ *	may be outstanding in parallel.
+ */
+static ssize_t tty_read(struct kiocb *iocb, struct iov_iter *to)
+{
+	int i;
+	struct file *file = iocb->ki_filp;
+	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(iocb, to);
+	i = -EIO;
+	if (ld->ops->read)
+		i = iterate_tty_read(ld, tty, file, to);
+	tty_ldisc_deref(ld);
+
+	if (i > 0)
+		tty_update_time(&inode->i_atime);
+
+	return i;
+}
+
+void tty_write_unlock(struct tty_struct *tty)
+{
+	mutex_unlock(&tty->atomic_write_lock);
+	wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
+}
+
+int tty_write_lock(struct tty_struct *tty, bool ndelay)
+{
+	if (!mutex_trylock(&tty->atomic_write_lock)) {
+		if (ndelay)
+			return -EAGAIN;
+		if (mutex_lock_interruptible(&tty->atomic_write_lock))
+			return -ERESTARTSYS;
+	}
+	return 0;
+}
+
+/*
+ * Split writes up in sane blocksizes to avoid
+ * denial-of-service type attacks
+ */
+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,
+	struct iov_iter *from)
+{
+	size_t count = iov_iter_count(from);
+	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.
+	 */
+	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 = kvmalloc(chunk, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
+		if (!buf_chunk) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		kvfree(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_iter(tty->write_buf, size, from) != size)
+			break;
+
+		ret = write(tty, file, tty->write_buf, size);
+		if (ret <= 0)
+			break;
+
+		written += ret;
+		if (ret > size)
+			break;
+
+		/* FIXME! Have Al check this! */
+		if (ret != size)
+			iov_iter_revert(from, size-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;
+}
+
+/**
+ * tty_write_message - write a message to a certain tty, not just the console.
+ * @tty: the destination tty_struct
+ * @msg: the message to write
+ *
+ * This is used for messages that need to be redirected to a specific tty. We
+ * don't put it into the syslog queue right now maybe in the future if really
+ * needed.
+ *
+ * We must still hold the BTM and test the CLOSING flag for the moment.
+ */
+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);
+	}
+}
+
+static ssize_t file_tty_write(struct file *file, struct kiocb *iocb, struct iov_iter *from)
+{
+	struct tty_struct *tty = file_tty(file);
+	struct tty_ldisc *ld;
+	ssize_t ret;
+
+	if (tty_paranoia_check(tty, file_inode(file), "tty_write"))
+		return -EIO;
+	if (!tty || !tty->ops->write ||	tty_io_error(tty))
+		return -EIO;
+	/* Short term debug to catch buggy drivers */
+	if (tty->ops->write_room == NULL)
+		tty_err(tty, "missing write_room method\n");
+	ld = tty_ldisc_ref_wait(tty);
+	if (!ld)
+		return hung_up_tty_write(iocb, from);
+	if (!ld->ops->write)
+		ret = -EIO;
+	else
+		ret = do_tty_write(ld->ops->write, tty, file, from);
+	tty_ldisc_deref(ld);
+	return ret;
+}
+
+/**
+ * tty_write		-	write method for tty device file
+ * @iocb: kernel I/O control block
+ * @from: iov_iter with data to write
+ *
+ * Write data to a tty device via the line discipline.
+ *
+ * Locking:
+ *	Locks the line discipline as required
+ *	Writes to the tty driver are serialized by the atomic_write_lock
+ *	and are then processed in chunks to the device. The line
+ *	discipline write method will not be invoked in parallel for
+ *	each device.
+ */
+static ssize_t tty_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	return file_tty_write(iocb->ki_filp, iocb, from);
+}
+
+ssize_t redirected_tty_write(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct file *p = NULL;
+
+	spin_lock(&redirect_lock);
+	if (redirect)
+		p = get_file(redirect);
+	spin_unlock(&redirect_lock);
+
+	/*
+	 * We know the redirected tty is just another tty, we can
+	 * call file_tty_write() directly with that file pointer.
+	 */
+	if (p) {
+		ssize_t res;
+
+		res = file_tty_write(p, iocb, iter);
+		fput(p);
+		return res;
+	}
+	return tty_write(iocb, iter);
+}
+
+/**
+ * tty_send_xchar	-	send priority character
+ * @tty: the tty to send to
+ * @ch: xchar to send
+ *
+ * Send a high priority character to the tty even if stopped.
+ *
+ * Locking: none for xchar method, write ordering for write method.
+ */
+int tty_send_xchar(struct tty_struct *tty, char ch)
+{
+	bool was_stopped = tty->flow.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, false) < 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;
+}
+
+/**
+ * pty_line_name	-	generate name for a pty
+ * @driver: the tty driver in use
+ * @index: the minor number
+ * @p: output buffer of at least 6 bytes
+ *
+ * Generate a name from a @driver reference and write it to the output buffer
+ * @p.
+ *
+ * Locking: None
+ */
+static void pty_line_name(struct tty_driver *driver, int index, char *p)
+{
+	static const char ptychar[] = "pqrstuvwxyzabcde";
+	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);
+}
+
+/**
+ * tty_line_name	-	generate name for a tty
+ * @driver: the tty driver in use
+ * @index: the minor number
+ * @p: output buffer of at least 7 bytes
+ *
+ * Generate a name from a @driver reference and write it to the output buffer
+ * @p.
+ *
+ * Locking: None
+ */
+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);
+}
+
+/**
+ * tty_driver_lookup_tty() - find an existing tty, if any
+ * @driver: the driver for the tty
+ * @file: file object
+ * @idx: the minor number
+ *
+ * Return: the tty, if found. If not found, return %NULL or ERR_PTR() if the
+ * driver lookup() method returns an error.
+ *
+ * Locking: tty_mutex must be held. If the tty is found, bump the tty kref.
+ */
+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 {
+		if (idx >= driver->num)
+			return ERR_PTR(-EINVAL);
+		tty = driver->ttys[idx];
+	}
+	if (!IS_ERR(tty))
+		tty_kref_get(tty);
+	return tty;
+}
+
+/**
+ * tty_init_termios	-  helper for termios setup
+ * @tty: the tty to set up
+ *
+ * Initialise the termios structure for this tty. This runs under the
+ * %tty_mutex currently so we can be relaxed about ordering.
+ */
+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);
+}
+EXPORT_SYMBOL_GPL(tty_init_termios);
+
+/**
+ * tty_standard_install - usual tty->ops->install
+ * @driver: the driver for the tty
+ * @tty: the tty
+ *
+ * If the @driver overrides @tty->ops->install, it still can call this function
+ * to perform the standard install operations.
+ */
+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;
+}
+EXPORT_SYMBOL_GPL(tty_standard_install);
+
+/**
+ * tty_driver_install_tty() - install a tty entry in the driver
+ * @driver: the driver for the tty
+ * @tty: the tty
+ *
+ * Install a tty object into the driver tables. The @tty->index field will be
+ * set by the time this is called. This method is responsible for ensuring any
+ * need additional structures are allocated and configured.
+ *
+ * Locking: tty_mutex for now
+ */
+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);
+}
+
+/**
+ * tty_driver_remove_tty() - remove a tty from the driver tables
+ * @driver: the driver for the tty
+ * @tty: tty to remove
+ *
+ * Remove a tty object from the driver tables. The tty->index field will be set
+ * by the time this is called.
+ *
+ * Locking: tty_mutex for now
+ */
+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;
+}
+
+/**
+ * tty_reopen()	- fast re-open of an open tty
+ * @tty: the tty to open
+ *
+ * Re-opens on master ptys are not allowed and return -%EIO.
+ *
+ * Locking: Caller must hold tty_lock
+ * Return: 0 on success, -errno on error.
+ */
+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;
+}
+
+/**
+ * tty_init_dev		-	initialise a tty device
+ * @driver: tty driver we are opening a device on
+ * @idx: device index
+ *
+ * Prepare a tty device. This may not be a "new" clean device but could also be
+ * an active device. The pty drivers require special handling because of this.
+ *
+ * Locking:
+ *	The function is called under the tty_mutex, which protects us from the
+ *	tty struct or driver itself going away.
+ *
+ * On exit the tty device has the line discipline attached and a reference
+ * count of 1. If a pair was created for pty/tty use and the other was a pty
+ * master then it too has a reference count of 1.
+ *
+ * WSH 06/09/97: Rewritten to remove races and properly clean up after a failed
+ * open. The new code protects the open with a mutex, so it's really quite
+ * straightforward. The mutex locking can probably be relaxed for the (most
+ * common) case of reopening a tty.
+ *
+ * Return: new tty structure
+ */
+struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
+{
+	struct tty_struct *tty;
+	int retval;
+
+	/*
+	 * First time open is complex, especially for PTY devices.
+	 * This code guarantees that either everything succeeds and the
+	 * TTY is ready for operation, or else the table slots are vacated
+	 * and the allocated memory released.  (Except that the termios
+	 * may be retained.)
+	 */
+
+	if (!try_module_get(driver->owner))
+		return ERR_PTR(-ENODEV);
+
+	tty = alloc_tty_struct(driver, idx);
+	if (!tty) {
+		retval = -ENOMEM;
+		goto err_module_put;
+	}
+
+	tty_lock(tty);
+	retval = tty_driver_install_tty(driver, tty);
+	if (retval < 0)
+		goto err_free_tty;
+
+	if (!tty->port)
+		tty->port = driver->ports[idx];
+
+	if (WARN_RATELIMIT(!tty->port,
+			"%s: %s driver does not set tty->port. This would crash the kernel. Fix the driver!\n",
+			__func__, tty->driver->name)) {
+		retval = -EINVAL;
+		goto err_release_lock;
+	}
+
+	retval = tty_ldisc_lock(tty, 5 * HZ);
+	if (retval)
+		goto err_release_lock;
+	tty->port->itty = tty;
+
+	/*
+	 * Structures all installed ... call the ldisc open routines.
+	 * If we fail here just call release_tty to clean up.  No need
+	 * to decrement the use counts, as release_tty doesn't care.
+	 */
+	retval = tty_ldisc_setup(tty, tty->link);
+	if (retval)
+		goto err_release_tty;
+	tty_ldisc_unlock(tty);
+	/* Return the tty locked so that it cannot vanish under the caller */
+	return tty;
+
+err_free_tty:
+	tty_unlock(tty);
+	free_tty_struct(tty);
+err_module_put:
+	module_put(driver->owner);
+	return ERR_PTR(retval);
+
+	/* call the tty release_tty routine to clean out this slot */
+err_release_tty:
+	tty_ldisc_unlock(tty);
+	tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
+			     retval, idx);
+err_release_lock:
+	tty_unlock(tty);
+	release_tty(tty, idx);
+	return ERR_PTR(retval);
+}
+
+/**
+ * tty_save_termios() - save tty termios data in driver table
+ * @tty: tty whose termios data to save
+ *
+ * Locking: Caller guarantees serialisation with tty_init_termios().
+ */
+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;
+}
+EXPORT_SYMBOL_GPL(tty_save_termios);
+
+/**
+ * tty_flush_works	-	flush all works of a tty/pty pair
+ * @tty: tty device to flush works for (or either end of a pty pair)
+ *
+ * Sync flush all works belonging to @tty (and the 'other' tty).
+ */
+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);
+	}
+}
+
+/**
+ * release_one_tty	-	release tty structure memory
+ * @work: work of tty we are obliterating
+ *
+ * Releases memory associated with a tty structure, and clears out the
+ * driver table slots. This function is called when a device is no longer
+ * in use. It also gets called when setup of a device fails.
+ *
+ * Locking:
+ *	takes the file list lock internally when working on the list of ttys
+ *	that the driver keeps.
+ *
+ * This method gets called from a work queue so that the driver private
+ * cleanup ops can sleep (needed for USB at least)
+ */
+static void release_one_tty(struct work_struct *work)
+{
+	struct tty_struct *tty =
+		container_of(work, struct tty_struct, hangup_work);
+	struct tty_driver *driver = tty->driver;
+	struct module *owner = driver->owner;
+
+	if (tty->ops->cleanup)
+		tty->ops->cleanup(tty);
+
+	tty_driver_kref_put(driver);
+	module_put(owner);
+
+	spin_lock(&tty->files_lock);
+	list_del_init(&tty->tty_files);
+	spin_unlock(&tty->files_lock);
+
+	put_pid(tty->ctrl.pgrp);
+	put_pid(tty->ctrl.session);
+	free_tty_struct(tty);
+}
+
+static void queue_release_one_tty(struct kref *kref)
+{
+	struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
+
+	/* The hangup queue is now free so we can reuse it rather than
+	 *  waste a chunk of memory for each port.
+	 */
+	INIT_WORK(&tty->hangup_work, release_one_tty);
+	schedule_work(&tty->hangup_work);
+}
+
+/**
+ * tty_kref_put		-	release a tty kref
+ * @tty: tty device
+ *
+ * Release a reference to the @tty device and if need be let the kref layer
+ * destruct the object for us.
+ */
+void tty_kref_put(struct tty_struct *tty)
+{
+	if (tty)
+		kref_put(&tty->kref, queue_release_one_tty);
+}
+EXPORT_SYMBOL(tty_kref_put);
+
+/**
+ * release_tty		-	release tty structure memory
+ * @tty: tty device release
+ * @idx: index of the tty device release
+ *
+ * Release both @tty and a possible linked partner (think pty pair),
+ * and decrement the refcount of the backing module.
+ *
+ * Locking:
+ *	tty_mutex
+ *	takes the file list lock internally when working on the list of ttys
+ *	that the driver keeps.
+ */
+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);
+}
+
+/**
+ * tty_release_checks - check a tty before real release
+ * @tty: tty to check
+ * @idx: index of the tty
+ *
+ * Performs some paranoid checking before true release of the @tty. This is a
+ * no-op unless %TTY_PARANOIA_CHECK is defined.
+ */
+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;
+}
+
+/**
+ * tty_kclose      -       closes tty opened by tty_kopen
+ * @tty: tty device
+ *
+ * Performs the final steps to release and free a tty device. It is the same as
+ * tty_release_struct() except that it also resets %TTY_PORT_KOPENED flag on
+ * @tty->port.
+ */
+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 commences */
+	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);
+}
+EXPORT_SYMBOL_GPL(tty_kclose);
+
+/**
+ * tty_release_struct	-	release a tty struct
+ * @tty: tty device
+ * @idx: index of the tty
+ *
+ * Performs the final steps to release and free a tty device. It is roughly the
+ * reverse of tty_init_dev().
+ */
+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);
+}
+EXPORT_SYMBOL_GPL(tty_release_struct);
+
+/**
+ * tty_release		-	vfs callback for close
+ * @inode: inode of tty
+ * @filp: file pointer for handle to tty
+ *
+ * Called the last time each file handle is closed that references this tty.
+ * There may however be several such references.
+ *
+ * Locking:
+ *	Takes BKL. See tty_release_dev().
+ *
+ * Even releasing the tty structures is a tricky business. We have to be very
+ * careful that the structures are all released at the same time, as interrupts
+ * might otherwise get the wrong pointers.
+ *
+ * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
+ * lead to double frees or releasing memory still in use.
+ */
+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->ctrl.session);
+		if (o_tty)
+			session_clear_tty(o_tty->ctrl.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;
+}
+
+/**
+ * tty_open_current_tty - get locked tty of current task
+ * @device: device number
+ * @filp: file pointer to tty
+ * @return: locked tty of the current task iff @device is /dev/tty
+ *
+ * Performs a re-open of the current task's controlling tty.
+ *
+ * We cannot return driver and index like for the other nodes because devpts
+ * will not work then. It expects inodes to be from devpts FS.
+ */
+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;
+}
+
+/**
+ * tty_lookup_driver - lookup a tty driver for a given device file
+ * @device: device number
+ * @filp: file pointer to tty
+ * @index: index for the device in the @return driver
+ *
+ * If returned value is not erroneous, the caller is responsible to decrement
+ * the refcount by tty_driver_kref_put().
+ *
+ * Locking: %tty_mutex protects get_tty_driver()
+ *
+ * Return: driver for this inode (with increased refcount)
+ */
+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;
+}
+
+static struct tty_struct *tty_kopen(dev_t device, int shared)
+{
+	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) || shared)
+		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;
+}
+
+/**
+ * tty_kopen_exclusive	-	open a tty device for kernel
+ * @device: dev_t of device to open
+ *
+ * Opens tty exclusively for kernel. Performs the driver lookup, makes sure
+ * it's not already opened and performs the first-time tty initialization.
+ *
+ * Claims the global %tty_mutex to serialize:
+ *  * concurrent first-time tty initialization
+ *  * concurrent tty driver removal w/ lookup
+ *  * concurrent tty removal from driver table
+ *
+ * Return: the locked initialized &tty_struct
+ */
+struct tty_struct *tty_kopen_exclusive(dev_t device)
+{
+	return tty_kopen(device, 0);
+}
+EXPORT_SYMBOL_GPL(tty_kopen_exclusive);
+
+/**
+ * tty_kopen_shared	-	open a tty device for shared in-kernel use
+ * @device: dev_t of device to open
+ *
+ * Opens an already existing tty for in-kernel use. Compared to
+ * tty_kopen_exclusive() above it doesn't ensure to be the only user.
+ *
+ * Locking: identical to tty_kopen() above.
+ */
+struct tty_struct *tty_kopen_shared(dev_t device)
+{
+	return tty_kopen(device, 1);
+}
+EXPORT_SYMBOL_GPL(tty_kopen_shared);
+
+/**
+ * tty_open_by_driver	-	open a tty device
+ * @device: dev_t of device to open
+ * @filp: file pointer to tty
+ *
+ * Performs the driver lookup, checks for a reopen, or otherwise performs the
+ * first-time tty initialization.
+ *
+ *
+ * Claims the global tty_mutex to serialize:
+ *  * concurrent first-time tty initialization
+ *  * concurrent tty driver removal w/ lookup
+ *  * concurrent tty removal from driver table
+ *
+ * Return: the locked initialized or re-opened &tty_struct
+ */
+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;
+}
+
+/**
+ * tty_open	-	open a tty device
+ * @inode: inode of device file
+ * @filp: file pointer to tty
+ *
+ * tty_open() and tty_release() keep up the tty count that contains the number
+ * of opens done on a tty. We cannot use the inode-count, as different inodes
+ * might point to the same tty.
+ *
+ * Open-counting is needed for pty masters, as well as for keeping track of
+ * serial lines: DTR is dropped when the last close happens.
+ * (This is not done solely through tty->count, now.  - Ted 1/27/92)
+ *
+ * The termios state of a pty is reset on the first open so that settings don't
+ * persist across reuse.
+ *
+ * Locking:
+ *  * %tty_mutex protects tty, tty_lookup_driver() and tty_init_dev().
+ *  * @tty->count should protect the rest.
+ *  * ->siglock protects ->signal/->sighand
+ *
+ * Note: the tty_unlock/lock cases without a ref are only safe due to %tty_mutex
+ */
+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;
+}
+
+
+/**
+ * tty_poll	-	check tty status
+ * @filp: file being polled
+ * @wait: poll wait structures to update
+ *
+ * Call the line discipline polling method to obtain the poll status of the
+ * device.
+ *
+ * Locking: locks called line discipline but ldisc poll method may be
+ * re-entered freely by other callers.
+ */
+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;
+}
+
+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->ctrl.pgrp) {
+			pid = tty->ctrl.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_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;
+}
+
+/**
+ * tiocsti		-	fake input character
+ * @tty: tty to fake input into
+ * @p: pointer to character
+ *
+ * Fake input to a tty device. Does the necessary locking and input management.
+ *
+ * FIXME: does not honour flow control ??
+ *
+ * Locking:
+ *  * Called functions take tty_ldiscs_lock
+ *  * current->signal->tty check is safe without locks
+ */
+static int tiocsti(struct tty_struct *tty, char __user *p)
+{
+	char ch, mbz = 0;
+	struct tty_ldisc *ld;
+
+	if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (get_user(ch, p))
+		return -EFAULT;
+	tty_audit_tiocsti(tty, ch);
+	ld = tty_ldisc_ref_wait(tty);
+	if (!ld)
+		return -EIO;
+	tty_buffer_lock_exclusive(tty->port);
+	if (ld->ops->receive_buf)
+		ld->ops->receive_buf(tty, &ch, &mbz, 1);
+	tty_buffer_unlock_exclusive(tty->port);
+	tty_ldisc_deref(ld);
+	return 0;
+}
+
+/**
+ * tiocgwinsz		-	implement window query ioctl
+ * @tty: tty
+ * @arg: user buffer for result
+ *
+ * Copies the kernel idea of the window size into the user buffer.
+ *
+ * Locking: @tty->winsize_mutex is taken to ensure the winsize data is
+ * consistent.
+ */
+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;
+}
+
+/**
+ * tty_do_resize	-	resize event
+ * @tty: tty being resized
+ * @ws: new dimensions
+ *
+ * Update the termios variables and send the necessary signals to peform a
+ * terminal resize correctly.
+ */
+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;
+}
+EXPORT_SYMBOL(tty_do_resize);
+
+/**
+ * tiocswinsz		-	implement window size set ioctl
+ * @tty: tty side of tty
+ * @arg: user buffer for result
+ *
+ * Copies the user idea of the window size to the kernel. Traditionally this is
+ * just advisory information but for the Linux console it actually has driver
+ * level meaning and triggers a VC resize.
+ *
+ * Locking:
+ *	Driver dependent. The default do_resize method takes the tty termios
+ *	mutex and ctrl.lock. The console takes its own lock then calls into the
+ *	default method.
+ */
+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);
+}
+
+/**
+ * tioccons	-	allow admin to move logical console
+ * @file: the file to become console
+ *
+ * Allow the administrator to move the redirected console device.
+ *
+ * Locking: uses redirect_lock to guard the redirect information
+ */
+static int tioccons(struct file *file)
+{
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (file->f_op->write_iter == redirected_tty_write) {
+		struct file *f;
+
+		spin_lock(&redirect_lock);
+		f = redirect;
+		redirect = NULL;
+		spin_unlock(&redirect_lock);
+		if (f)
+			fput(f);
+		return 0;
+	}
+	if (file->f_op->write_iter != tty_write)
+		return -ENOTTY;
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EBADF;
+	if (!(file->f_mode & FMODE_CAN_WRITE))
+		return -EINVAL;
+	spin_lock(&redirect_lock);
+	if (redirect) {
+		spin_unlock(&redirect_lock);
+		return -EBUSY;
+	}
+	redirect = get_file(file);
+	spin_unlock(&redirect_lock);
+	return 0;
+}
+
+/**
+ * tiocsetd	-	set line discipline
+ * @tty: tty device
+ * @p: pointer to user data
+ *
+ * Set the line discipline according to user request.
+ *
+ * Locking: see tty_set_ldisc(), this function is just a helper
+ */
+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;
+}
+
+/**
+ * tiocgetd	-	get line discipline
+ * @tty: tty device
+ * @p: pointer to user data
+ *
+ * Retrieves the line discipline id directly from the ldisc.
+ *
+ * Locking: waits for ldisc reference (in case the line discipline is changing
+ * or the @tty is being hungup)
+ */
+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;
+}
+
+/**
+ * send_break	-	performed time break
+ * @tty: device to break on
+ * @duration: timeout in mS
+ *
+ * Perform a timed break on hardware that lacks its own driver level timed
+ * break functionality.
+ *
+ * Locking:
+ *	@tty->atomic_write_lock serializes
+ */
+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)
+		return tty->ops->break_ctl(tty, duration);
+
+	/* Do the work ourselves */
+	if (tty_write_lock(tty, false) < 0)
+		return -EINTR;
+
+	retval = tty->ops->break_ctl(tty, -1);
+	if (!retval) {
+		msleep_interruptible(duration);
+		retval = tty->ops->break_ctl(tty, 0);
+	} else if (retval == -EOPNOTSUPP) {
+		/* some drivers can tell only dynamically */
+		retval = 0;
+	}
+	tty_write_unlock(tty);
+
+	if (signal_pending(current))
+		retval = -EINTR;
+
+	return retval;
+}
+
+/**
+ * tty_tiocmget		-	get modem status
+ * @tty: tty device
+ * @p: pointer to result
+ *
+ * Obtain the modem status bits from the tty driver if the feature is
+ * supported. Return -%ENOTTY if it is not available.
+ *
+ * Locking: none (up to the driver)
+ */
+static int tty_tiocmget(struct tty_struct *tty, int __user *p)
+{
+	int retval = -ENOTTY;
+
+	if (tty->ops->tiocmget) {
+		retval = tty->ops->tiocmget(tty);
+
+		if (retval >= 0)
+			retval = put_user(retval, p);
+	}
+	return retval;
+}
+
+/**
+ * tty_tiocmset		-	set modem status
+ * @tty: tty device
+ * @cmd: command - clear bits, set bits or set all
+ * @p: pointer to desired bits
+ *
+ * Set the modem status bits from the tty driver if the feature
+ * is supported. Return -%ENOTTY if it is not available.
+ *
+ * Locking: none (up to the driver)
+ */
+static int tty_tiocmset(struct tty_struct *tty, unsigned int cmd,
+	     unsigned __user *p)
+{
+	int retval;
+	unsigned int set, clear, val;
+
+	if (tty->ops->tiocmset == NULL)
+		return -ENOTTY;
+
+	retval = get_user(val, p);
+	if (retval)
+		return retval;
+	set = clear = 0;
+	switch (cmd) {
+	case TIOCMBIS:
+		set = val;
+		break;
+	case TIOCMBIC:
+		clear = val;
+		break;
+	case TIOCMSET:
+		set = val;
+		clear = ~val;
+		break;
+	}
+	set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
+	clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
+	return tty->ops->tiocmset(tty, set, clear);
+}
+
+/**
+ * tty_get_icount	-	get tty statistics
+ * @tty: tty device
+ * @icount: output parameter
+ *
+ * Gets a copy of the @tty's icount statistics.
+ *
+ * Locking: none (up to the driver)
+ */
+int tty_get_icount(struct tty_struct *tty,
+		   struct serial_icounter_struct *icount)
+{
+	memset(icount, 0, sizeof(*icount));
+
+	if (tty->ops->get_icount)
+		return tty->ops->get_icount(tty, icount);
+	else
+		return -ENOTTY;
+}
+EXPORT_SYMBOL_GPL(tty_get_icount);
+
+static int tty_tiocgicount(struct tty_struct *tty, void __user *arg)
+{
+	struct serial_icounter_struct icount;
+	int retval;
+
+	retval = tty_get_icount(tty, &icount);
+	if (retval != 0)
+		return retval;
+
+	if (copy_to_user(arg, &icount, sizeof(icount)))
+		return -EFAULT;
+	return 0;
+}
+
+static int tty_set_serial(struct tty_struct *tty, struct serial_struct *ss)
+{
+	char comm[TASK_COMM_LEN];
+	int flags;
+
+	flags = ss->flags & ASYNC_DEPRECATED;
+
+	if (flags)
+		pr_warn_ratelimited("%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, ss);
+}
+
+static int tty_tiocsserial(struct tty_struct *tty, struct serial_struct __user *ss)
+{
+	struct serial_struct v;
+
+	if (copy_from_user(&v, ss, sizeof(*ss)))
+		return -EFAULT;
+
+	return tty_set_serial(tty, &v);
+}
+
+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;
+}
+
+/*
+ * if pty, return the slave side (real_tty)
+ * otherwise, return self
+ */
+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;
+}
+
+/*
+ * Split this up, as gcc can choke on it otherwise..
+ */
+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, cmd, arg);
+		if (retval == -ENOIOCTLCMD)
+			retval = -ENOTTY;
+	}
+	tty_ldisc_deref(ld);
+	return retval;
+}
+
+#ifdef CONFIG_COMPAT
+
+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 int compat_tty_tiocsserial(struct tty_struct *tty,
+		struct serial_struct32 __user *ss)
+{
+	struct serial_struct32 v32;
+	struct serial_struct v;
+
+	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;
+
+	return tty_set_serial(tty, &v);
+}
+
+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 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, cmd, arg);
+	if (retval == -ENOIOCTLCMD && ld->ops->ioctl)
+		retval = ld->ops->ioctl(tty, (unsigned long)compat_ptr(cmd),
+				arg);
+	tty_ldisc_deref(ld);
+
+	return retval;
+}
+#endif
+
+static int this_tty(const void *t, struct file *file, unsigned fd)
+{
+	if (likely(file->f_op->read_iter != tty_read))
+		return 0;
+	return file_tty(file) != t ? 0 : fd + 1;
+}
+
+/*
+ * This implements the "Secure Attention Key" ---  the idea is to
+ * prevent trojan horses by killing all processes associated with this
+ * tty when the user hits the "Secure Attention Key".  Required for
+ * super-paranoid applications --- see the Orange Book for more details.
+ *
+ * This code could be nicer; ideally it should send a HUP, wait a few
+ * seconds, then send a INT, and then a KILL signal.  But you then
+ * have to coordinate with the init process, since all processes associated
+ * with the current tty must be dead before the new getty is allowed
+ * to spawn.
+ *
+ * Now, if it would be correct ;-/ The current code has a nasty hole -
+ * it doesn't catch files in flight. We may send the descriptor to ourselves
+ * via AF_UNIX socket, close it and later fetch from socket. FIXME.
+ *
+ * Nasty bug: do_SAK is being called in interrupt context.  This can
+ * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
+ */
+void __do_SAK(struct tty_struct *tty)
+{
+	struct task_struct *g, *p;
+	struct pid *session;
+	int i;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tty->ctrl.lock, flags);
+	session = get_pid(tty->ctrl.session);
+	spin_unlock_irqrestore(&tty->ctrl.lock, flags);
+
+	tty_ldisc_flush(tty);
+
+	tty_driver_flush_buffer(tty);
+
+	read_lock(&tasklist_lock);
+	/* Kill the entire session */
+	do_each_pid_task(session, PIDTYPE_SID, p) {
+		tty_notice(tty, "SAK: killed process %d (%s): by session\n",
+			   task_pid_nr(p), p->comm);
+		group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID);
+	} while_each_pid_task(session, PIDTYPE_SID, p);
+
+	/* Now kill any processes that happen to have the tty open */
+	do_each_thread(g, p) {
+		if (p->signal->tty == tty) {
+			tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n",
+				   task_pid_nr(p), p->comm);
+			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
+					PIDTYPE_SID);
+			continue;
+		}
+		task_lock(p);
+		i = iterate_fd(p->files, 0, this_tty, tty);
+		if (i != 0) {
+			tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n",
+				   task_pid_nr(p), p->comm, i - 1);
+			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
+					PIDTYPE_SID);
+		}
+		task_unlock(p);
+	} while_each_thread(g, p);
+	read_unlock(&tasklist_lock);
+	put_pid(session);
+}
+
+static void do_SAK_work(struct work_struct *work)
+{
+	struct tty_struct *tty =
+		container_of(work, struct tty_struct, SAK_work);
+	__do_SAK(tty);
+}
+
+/*
+ * The tq handling here is a little racy - tty->SAK_work may already be queued.
+ * Fortunately we don't need to worry, because if ->SAK_work is already queued,
+ * the values which we write to it will be identical to the values which it
+ * already has. --akpm
+ */
+void do_SAK(struct tty_struct *tty)
+{
+	if (!tty)
+		return;
+	schedule_work(&tty->SAK_work);
+}
+EXPORT_SYMBOL(do_SAK);
+
+/* Must put_device() after it's unused! */
+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);
+}
+
+
+/**
+ * alloc_tty_struct - allocate a new tty
+ * @driver: driver which will handle the returned tty
+ * @idx: minor of the tty
+ *
+ * This subroutine allocates and initializes a tty structure.
+ *
+ * Locking: none - @tty in question is not exposed at this point
+ */
+struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
+{
+	struct tty_struct *tty;
+
+	tty = kzalloc(sizeof(*tty), GFP_KERNEL_ACCOUNT);
+	if (!tty)
+		return NULL;
+
+	kref_init(&tty->kref);
+	if (tty_ldisc_init(tty)) {
+		kfree(tty);
+		return NULL;
+	}
+	tty->ctrl.session = NULL;
+	tty->ctrl.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;
+}
+
+/**
+ * tty_put_char	- write one character to a tty
+ * @tty: tty
+ * @ch: character to write
+ *
+ * Write one byte to the @tty using the provided @tty->ops->put_char() method
+ * if present.
+ *
+ * Note: the specific put_char operation in the driver layer may go
+ * away soon. Don't call it directly, use this method
+ *
+ * Return: the number of characters successfully output.
+ */
+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);
+}
+EXPORT_SYMBOL_GPL(tty_put_char);
+
+struct class *tty_class;
+
+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;
+}
+
+/**
+ * tty_register_device - register a tty device
+ * @driver: the tty driver that describes the tty device
+ * @index: the index in the tty driver for this tty device
+ * @device: a struct device that is associated with this tty device.
+ *	This field is optional, if there is no known struct device
+ *	for this tty device it can be set to NULL safely.
+ *
+ * This call is required to be made to register an individual tty device
+ * if the tty driver's flags have the %TTY_DRIVER_DYNAMIC_DEV bit set.  If
+ * that bit is not set, this function should not be called by a tty
+ * driver.
+ *
+ * Locking: ??
+ *
+ * Return: A pointer to the struct device for this tty device (or
+ * ERR_PTR(-EFOO) on error).
+ */
+struct device *tty_register_device(struct tty_driver *driver, unsigned index,
+				   struct device *device)
+{
+	return tty_register_device_attr(driver, index, device, NULL, NULL);
+}
+EXPORT_SYMBOL(tty_register_device);
+
+static void tty_device_create_release(struct device *dev)
+{
+	dev_dbg(dev, "releasing...\n");
+	kfree(dev);
+}
+
+/**
+ * tty_register_device_attr - register a tty device
+ * @driver: the tty driver that describes the tty device
+ * @index: the index in the tty driver for this tty device
+ * @device: a struct device that is associated with this tty device.
+ *	This field is optional, if there is no known struct device
+ *	for this tty device it can be set to %NULL safely.
+ * @drvdata: Driver data to be set to device.
+ * @attr_grp: Attribute group to be set on device.
+ *
+ * This call is required to be made to register an individual tty device if the
+ * tty driver's flags have the %TTY_DRIVER_DYNAMIC_DEV bit set. If that bit is
+ * not set, this function should not be called by a tty driver.
+ *
+ * Locking: ??
+ *
+ * Return: A pointer to the struct device for this tty device (or
+ * ERR_PTR(-EFOO) on error).
+ */
+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);
+}
+EXPORT_SYMBOL_GPL(tty_register_device_attr);
+
+/**
+ * tty_unregister_device - unregister a tty device
+ * @driver: the tty driver that describes the tty device
+ * @index: the index in the tty driver for this tty device
+ *
+ * If a tty device is registered with a call to tty_register_device() then
+ * this function must be called when the tty device is gone.
+ *
+ * Locking: ??
+ */
+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;
+	}
+}
+EXPORT_SYMBOL(tty_unregister_device);
+
+/**
+ * __tty_alloc_driver -- allocate tty driver
+ * @lines: count of lines this driver can handle at most
+ * @owner: module which is responsible for this driver
+ * @flags: some of %TTY_DRIVER_ flags, will be set in driver->flags
+ *
+ * This should not be called directly, some of the provided macros should be
+ * used instead. Use IS_ERR() and friends on @retval.
+ */
+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->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);
+}
+EXPORT_SYMBOL(__tty_alloc_driver);
+
+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);
+}
+
+/**
+ * tty_driver_kref_put -- drop a reference to a tty driver
+ * @driver: driver of which to drop the reference
+ *
+ * The final put will destroy and free up the driver.
+ */
+void tty_driver_kref_put(struct tty_driver *driver)
+{
+	kref_put(&driver->kref, destruct_tty_driver);
+}
+EXPORT_SYMBOL(tty_driver_kref_put);
+
+/**
+ * tty_register_driver -- register a tty driver
+ * @driver: driver to register
+ *
+ * Called by a tty driver to register itself.
+ */
+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;
+}
+EXPORT_SYMBOL(tty_register_driver);
+
+/**
+ * tty_unregister_driver -- unregister a tty driver
+ * @driver: driver to unregister
+ *
+ * Called by a tty driver to unregister itself.
+ */
+void tty_unregister_driver(struct tty_driver *driver)
+{
+	unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
+				driver->num);
+	mutex_lock(&tty_mutex);
+	list_del(&driver->tty_drivers);
+	mutex_unlock(&tty_mutex);
+}
+EXPORT_SYMBOL(tty_unregister_driver);
+
+dev_t tty_devnum(struct tty_struct *tty)
+{
+	return MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
+}
+EXPORT_SYMBOL(tty_devnum);
+
+void tty_default_fops(struct file_operations *fops)
+{
+	*fops = tty_fops;
+}
+
+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;
+}
+
+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;
+}
+
+postcore_initcall(tty_class_init);
+
+/* 3/2004 jmc: why do these devices exist? */
+static struct cdev tty_cdev, console_cdev;
+
+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;
+}
+static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);
+
+static struct attribute *cons_dev_attrs[] = {
+	&dev_attr_active.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(cons_dev);
+
+static struct device *consdev;
+
+void console_sysfs_notify(void)
+{
+	if (consdev)
+		sysfs_notify(&consdev->kobj, NULL, "active");
+}
+
+/*
+ * Ok, now we can initialize the rest of the tty devices and can count
+ * on memory allocations, interrupts etc..
+ */
+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;
+}
+