Adding upstream version 5.10.209.upstream/5.10.209upstream

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

1 files changed, 908 insertions, 0 deletions

diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
new file mode 100644
index 000000000..12a30329a
--- /dev/null
+++ b/drivers/tty/tty_ioctl.c
@@ -0,0 +1,908 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *
+ * 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).
+ */
+
+#include <linux/types.h>
+#include <linux/termios.h>
+#include <linux/errno.h>
+#include <linux/sched/signal.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/tty.h>
+#include <linux/fcntl.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/bitops.h>
+#include <linux/mutex.h>
+#include <linux/compat.h>
+#include "tty.h"
+
+#include <asm/io.h>
+#include <linux/uaccess.h>
+
+#undef TTY_DEBUG_WAIT_UNTIL_SENT
+
+#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
+# define tty_debug_wait_until_sent(tty, f, args...)    tty_debug(tty, f, ##args)
+#else
+# define tty_debug_wait_until_sent(tty, f, args...)    do {} while (0)
+#endif
+
+#undef	DEBUG
+
+/*
+ * Internal flag options for termios setting behavior
+ */
+#define TERMIOS_FLUSH	1
+#define TERMIOS_WAIT	2
+#define TERMIOS_TERMIO	4
+#define TERMIOS_OLD	8
+
+
+/**
+ *	tty_chars_in_buffer	-	characters pending
+ *	@tty: terminal
+ *
+ *	Return the number of bytes of data in the device private
+ *	output queue. If no private method is supplied there is assumed
+ *	to be no queue on the device.
+ */
+
+int tty_chars_in_buffer(struct tty_struct *tty)
+{
+	if (tty->ops->chars_in_buffer)
+		return tty->ops->chars_in_buffer(tty);
+	else
+		return 0;
+}
+EXPORT_SYMBOL(tty_chars_in_buffer);
+
+/**
+ *	tty_write_room		-	write queue space
+ *	@tty: terminal
+ *
+ *	Return the number of bytes that can be queued to this device
+ *	at the present time. The result should be treated as a guarantee
+ *	and the driver cannot offer a value it later shrinks by more than
+ *	the number of bytes written. If no method is provided 2K is always
+ *	returned and data may be lost as there will be no flow control.
+ */
+ 
+int tty_write_room(struct tty_struct *tty)
+{
+	if (tty->ops->write_room)
+		return tty->ops->write_room(tty);
+	return 2048;
+}
+EXPORT_SYMBOL(tty_write_room);
+
+/**
+ *	tty_driver_flush_buffer	-	discard internal buffer
+ *	@tty: terminal
+ *
+ *	Discard the internal output buffer for this device. If no method
+ *	is provided then either the buffer cannot be hardware flushed or
+ *	there is no buffer driver side.
+ */
+void tty_driver_flush_buffer(struct tty_struct *tty)
+{
+	if (tty->ops->flush_buffer)
+		tty->ops->flush_buffer(tty);
+}
+EXPORT_SYMBOL(tty_driver_flush_buffer);
+
+/**
+ *	tty_throttle		-	flow control
+ *	@tty: terminal
+ *
+ *	Indicate that a tty should stop transmitting data down the stack.
+ *	Takes the termios rwsem to protect against parallel throttle/unthrottle
+ *	and also to ensure the driver can consistently reference its own
+ *	termios data at this point when implementing software flow control.
+ */
+
+void tty_throttle(struct tty_struct *tty)
+{
+	down_write(&tty->termios_rwsem);
+	/* check TTY_THROTTLED first so it indicates our state */
+	if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
+	    tty->ops->throttle)
+		tty->ops->throttle(tty);
+	tty->flow_change = 0;
+	up_write(&tty->termios_rwsem);
+}
+EXPORT_SYMBOL(tty_throttle);
+
+/**
+ *	tty_unthrottle		-	flow control
+ *	@tty: terminal
+ *
+ *	Indicate that a tty may continue transmitting data down the stack.
+ *	Takes the termios rwsem to protect against parallel throttle/unthrottle
+ *	and also to ensure the driver can consistently reference its own
+ *	termios data at this point when implementing software flow control.
+ *
+ *	Drivers should however remember that the stack can issue a throttle,
+ *	then change flow control method, then unthrottle.
+ */
+
+void tty_unthrottle(struct tty_struct *tty)
+{
+	down_write(&tty->termios_rwsem);
+	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
+	    tty->ops->unthrottle)
+		tty->ops->unthrottle(tty);
+	tty->flow_change = 0;
+	up_write(&tty->termios_rwsem);
+}
+EXPORT_SYMBOL(tty_unthrottle);
+
+/**
+ *	tty_throttle_safe	-	flow control
+ *	@tty: terminal
+ *
+ *	Similar to tty_throttle() but will only attempt throttle
+ *	if tty->flow_change is TTY_THROTTLE_SAFE. Prevents an accidental
+ *	throttle due to race conditions when throttling is conditional
+ *	on factors evaluated prior to throttling.
+ *
+ *	Returns 0 if tty is throttled (or was already throttled)
+ */
+
+int tty_throttle_safe(struct tty_struct *tty)
+{
+	int ret = 0;
+
+	mutex_lock(&tty->throttle_mutex);
+	if (!tty_throttled(tty)) {
+		if (tty->flow_change != TTY_THROTTLE_SAFE)
+			ret = 1;
+		else {
+			set_bit(TTY_THROTTLED, &tty->flags);
+			if (tty->ops->throttle)
+				tty->ops->throttle(tty);
+		}
+	}
+	mutex_unlock(&tty->throttle_mutex);
+
+	return ret;
+}
+
+/**
+ *	tty_unthrottle_safe	-	flow control
+ *	@tty: terminal
+ *
+ *	Similar to tty_unthrottle() but will only attempt unthrottle
+ *	if tty->flow_change is TTY_UNTHROTTLE_SAFE. Prevents an accidental
+ *	unthrottle due to race conditions when unthrottling is conditional
+ *	on factors evaluated prior to unthrottling.
+ *
+ *	Returns 0 if tty is unthrottled (or was already unthrottled)
+ */
+
+int tty_unthrottle_safe(struct tty_struct *tty)
+{
+	int ret = 0;
+
+	mutex_lock(&tty->throttle_mutex);
+	if (tty_throttled(tty)) {
+		if (tty->flow_change != TTY_UNTHROTTLE_SAFE)
+			ret = 1;
+		else {
+			clear_bit(TTY_THROTTLED, &tty->flags);
+			if (tty->ops->unthrottle)
+				tty->ops->unthrottle(tty);
+		}
+	}
+	mutex_unlock(&tty->throttle_mutex);
+
+	return ret;
+}
+
+/**
+ *	tty_wait_until_sent	-	wait for I/O to finish
+ *	@tty: tty we are waiting for
+ *	@timeout: how long we will wait
+ *
+ *	Wait for characters pending in a tty driver to hit the wire, or
+ *	for a timeout to occur (eg due to flow control)
+ *
+ *	Locking: none
+ */
+
+void tty_wait_until_sent(struct tty_struct *tty, long timeout)
+{
+	tty_debug_wait_until_sent(tty, "wait until sent, timeout=%ld\n", timeout);
+
+	if (!timeout)
+		timeout = MAX_SCHEDULE_TIMEOUT;
+
+	timeout = wait_event_interruptible_timeout(tty->write_wait,
+			!tty_chars_in_buffer(tty), timeout);
+	if (timeout <= 0)
+		return;
+
+	if (timeout == MAX_SCHEDULE_TIMEOUT)
+		timeout = 0;
+
+	if (tty->ops->wait_until_sent)
+		tty->ops->wait_until_sent(tty, timeout);
+}
+EXPORT_SYMBOL(tty_wait_until_sent);
+
+
+/*
+ *		Termios Helper Methods
+ */
+
+static void unset_locked_termios(struct tty_struct *tty, struct ktermios *old)
+{
+	struct ktermios *termios = &tty->termios;
+	struct ktermios *locked  = &tty->termios_locked;
+	int	i;
+
+#define NOSET_MASK(x, y, z) (x = ((x) & ~(z)) | ((y) & (z)))
+
+	NOSET_MASK(termios->c_iflag, old->c_iflag, locked->c_iflag);
+	NOSET_MASK(termios->c_oflag, old->c_oflag, locked->c_oflag);
+	NOSET_MASK(termios->c_cflag, old->c_cflag, locked->c_cflag);
+	NOSET_MASK(termios->c_lflag, old->c_lflag, locked->c_lflag);
+	termios->c_line = locked->c_line ? old->c_line : termios->c_line;
+	for (i = 0; i < NCCS; i++)
+		termios->c_cc[i] = locked->c_cc[i] ?
+			old->c_cc[i] : termios->c_cc[i];
+	/* FIXME: What should we do for i/ospeed */
+}
+
+/**
+ *	tty_termios_copy_hw	-	copy hardware settings
+ *	@new: New termios
+ *	@old: Old termios
+ *
+ *	Propagate the hardware specific terminal setting bits from
+ *	the old termios structure to the new one. This is used in cases
+ *	where the hardware does not support reconfiguration or as a helper
+ *	in some cases where only minimal reconfiguration is supported
+ */
+
+void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old)
+{
+	/* The bits a dumb device handles in software. Smart devices need
+	   to always provide a set_termios method */
+	new->c_cflag &= HUPCL | CREAD | CLOCAL;
+	new->c_cflag |= old->c_cflag & ~(HUPCL | CREAD | CLOCAL);
+	new->c_ispeed = old->c_ispeed;
+	new->c_ospeed = old->c_ospeed;
+}
+EXPORT_SYMBOL(tty_termios_copy_hw);
+
+/**
+ *	tty_termios_hw_change	-	check for setting change
+ *	@a: termios
+ *	@b: termios to compare
+ *
+ *	Check if any of the bits that affect a dumb device have changed
+ *	between the two termios structures, or a speed change is needed.
+ */
+
+int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b)
+{
+	if (a->c_ispeed != b->c_ispeed || a->c_ospeed != b->c_ospeed)
+		return 1;
+	if ((a->c_cflag ^ b->c_cflag) & ~(HUPCL | CREAD | CLOCAL))
+		return 1;
+	return 0;
+}
+EXPORT_SYMBOL(tty_termios_hw_change);
+
+/**
+ *	tty_set_termios		-	update termios values
+ *	@tty: tty to update
+ *	@new_termios: desired new value
+ *
+ *	Perform updates to the termios values set on this terminal.
+ *	A master pty's termios should never be set.
+ *
+ *	Locking: termios_rwsem
+ */
+
+int tty_set_termios(struct tty_struct *tty, struct ktermios *new_termios)
+{
+	struct ktermios old_termios;
+	struct tty_ldisc *ld;
+
+	WARN_ON(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+		tty->driver->subtype == PTY_TYPE_MASTER);
+	/*
+	 *	Perform the actual termios internal changes under lock.
+	 */
+
+
+	/* FIXME: we need to decide on some locking/ordering semantics
+	   for the set_termios notification eventually */
+	down_write(&tty->termios_rwsem);
+	old_termios = tty->termios;
+	tty->termios = *new_termios;
+	unset_locked_termios(tty, &old_termios);
+
+	if (tty->ops->set_termios)
+		tty->ops->set_termios(tty, &old_termios);
+	else
+		tty_termios_copy_hw(&tty->termios, &old_termios);
+
+	ld = tty_ldisc_ref(tty);
+	if (ld != NULL) {
+		if (ld->ops->set_termios)
+			ld->ops->set_termios(tty, &old_termios);
+		tty_ldisc_deref(ld);
+	}
+	up_write(&tty->termios_rwsem);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tty_set_termios);
+
+/**
+ *	set_termios		-	set termios values for a tty
+ *	@tty: terminal device
+ *	@arg: user data
+ *	@opt: option information
+ *
+ *	Helper function to prepare termios data and run necessary other
+ *	functions before using tty_set_termios to do the actual changes.
+ *
+ *	Locking:
+ *		Called functions take ldisc and termios_rwsem locks
+ */
+
+static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
+{
+	struct ktermios tmp_termios;
+	struct tty_ldisc *ld;
+	int retval = tty_check_change(tty);
+
+	if (retval)
+		return retval;
+
+	down_read(&tty->termios_rwsem);
+	tmp_termios = tty->termios;
+	up_read(&tty->termios_rwsem);
+
+	if (opt & TERMIOS_TERMIO) {
+		if (user_termio_to_kernel_termios(&tmp_termios,
+						(struct termio __user *)arg))
+			return -EFAULT;
+#ifdef TCGETS2
+	} else if (opt & TERMIOS_OLD) {
+		if (user_termios_to_kernel_termios_1(&tmp_termios,
+						(struct termios __user *)arg))
+			return -EFAULT;
+	} else {
+		if (user_termios_to_kernel_termios(&tmp_termios,
+						(struct termios2 __user *)arg))
+			return -EFAULT;
+	}
+#else
+	} else if (user_termios_to_kernel_termios(&tmp_termios,
+					(struct termios __user *)arg))
+		return -EFAULT;
+#endif
+
+	/* If old style Bfoo values are used then load c_ispeed/c_ospeed
+	 * with the real speed so its unconditionally usable */
+	tmp_termios.c_ispeed = tty_termios_input_baud_rate(&tmp_termios);
+	tmp_termios.c_ospeed = tty_termios_baud_rate(&tmp_termios);
+
+	if (opt & (TERMIOS_FLUSH|TERMIOS_WAIT)) {
+retry_write_wait:
+		retval = wait_event_interruptible(tty->write_wait, !tty_chars_in_buffer(tty));
+		if (retval < 0)
+			return retval;
+
+		if (tty_write_lock(tty, false) < 0)
+			goto retry_write_wait;
+
+		/* Racing writer? */
+		if (tty_chars_in_buffer(tty)) {
+			tty_write_unlock(tty);
+			goto retry_write_wait;
+		}
+
+		ld = tty_ldisc_ref(tty);
+		if (ld != NULL) {
+			if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
+				ld->ops->flush_buffer(tty);
+			tty_ldisc_deref(ld);
+		}
+
+		if ((opt & TERMIOS_WAIT) && tty->ops->wait_until_sent) {
+			tty->ops->wait_until_sent(tty, 0);
+			if (signal_pending(current)) {
+				tty_write_unlock(tty);
+				return -ERESTARTSYS;
+			}
+		}
+
+		tty_set_termios(tty, &tmp_termios);
+
+		tty_write_unlock(tty);
+	} else {
+		tty_set_termios(tty, &tmp_termios);
+	}
+
+	/* FIXME: Arguably if tmp_termios == tty->termios AND the
+	   actual requested termios was not tmp_termios then we may
+	   want to return an error as no user requested change has
+	   succeeded */
+	return 0;
+}
+
+static void copy_termios(struct tty_struct *tty, struct ktermios *kterm)
+{
+	down_read(&tty->termios_rwsem);
+	*kterm = tty->termios;
+	up_read(&tty->termios_rwsem);
+}
+
+static void copy_termios_locked(struct tty_struct *tty, struct ktermios *kterm)
+{
+	down_read(&tty->termios_rwsem);
+	*kterm = tty->termios_locked;
+	up_read(&tty->termios_rwsem);
+}
+
+static int get_termio(struct tty_struct *tty, struct termio __user *termio)
+{
+	struct ktermios kterm;
+	copy_termios(tty, &kterm);
+	if (kernel_termios_to_user_termio(termio, &kterm))
+		return -EFAULT;
+	return 0;
+}
+
+#ifdef TIOCGETP
+/*
+ * These are deprecated, but there is limited support..
+ *
+ * The "sg_flags" translation is a joke..
+ */
+static int get_sgflags(struct tty_struct *tty)
+{
+	int flags = 0;
+
+	if (!L_ICANON(tty)) {
+		if (L_ISIG(tty))
+			flags |= 0x02;		/* cbreak */
+		else
+			flags |= 0x20;		/* raw */
+	}
+	if (L_ECHO(tty))
+		flags |= 0x08;			/* echo */
+	if (O_OPOST(tty))
+		if (O_ONLCR(tty))
+			flags |= 0x10;		/* crmod */
+	return flags;
+}
+
+static int get_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
+{
+	struct sgttyb tmp;
+
+	down_read(&tty->termios_rwsem);
+	tmp.sg_ispeed = tty->termios.c_ispeed;
+	tmp.sg_ospeed = tty->termios.c_ospeed;
+	tmp.sg_erase = tty->termios.c_cc[VERASE];
+	tmp.sg_kill = tty->termios.c_cc[VKILL];
+	tmp.sg_flags = get_sgflags(tty);
+	up_read(&tty->termios_rwsem);
+
+	return copy_to_user(sgttyb, &tmp, sizeof(tmp)) ? -EFAULT : 0;
+}
+
+static void set_sgflags(struct ktermios *termios, int flags)
+{
+	termios->c_iflag = ICRNL | IXON;
+	termios->c_oflag = 0;
+	termios->c_lflag = ISIG | ICANON;
+	if (flags & 0x02) {	/* cbreak */
+		termios->c_iflag = 0;
+		termios->c_lflag &= ~ICANON;
+	}
+	if (flags & 0x08) {		/* echo */
+		termios->c_lflag |= ECHO | ECHOE | ECHOK |
+				    ECHOCTL | ECHOKE | IEXTEN;
+	}
+	if (flags & 0x10) {		/* crmod */
+		termios->c_oflag |= OPOST | ONLCR;
+	}
+	if (flags & 0x20) {	/* raw */
+		termios->c_iflag = 0;
+		termios->c_lflag &= ~(ISIG | ICANON);
+	}
+	if (!(termios->c_lflag & ICANON)) {
+		termios->c_cc[VMIN] = 1;
+		termios->c_cc[VTIME] = 0;
+	}
+}
+
+/**
+ *	set_sgttyb		-	set legacy terminal values
+ *	@tty: tty structure
+ *	@sgttyb: pointer to old style terminal structure
+ *
+ *	Updates a terminal from the legacy BSD style terminal information
+ *	structure.
+ *
+ *	Locking: termios_rwsem
+ */
+
+static int set_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
+{
+	int retval;
+	struct sgttyb tmp;
+	struct ktermios termios;
+
+	retval = tty_check_change(tty);
+	if (retval)
+		return retval;
+
+	if (copy_from_user(&tmp, sgttyb, sizeof(tmp)))
+		return -EFAULT;
+
+	down_write(&tty->termios_rwsem);
+	termios = tty->termios;
+	termios.c_cc[VERASE] = tmp.sg_erase;
+	termios.c_cc[VKILL] = tmp.sg_kill;
+	set_sgflags(&termios, tmp.sg_flags);
+	/* Try and encode into Bfoo format */
+#ifdef BOTHER
+	tty_termios_encode_baud_rate(&termios, termios.c_ispeed,
+						termios.c_ospeed);
+#endif
+	up_write(&tty->termios_rwsem);
+	tty_set_termios(tty, &termios);
+	return 0;
+}
+#endif
+
+#ifdef TIOCGETC
+static int get_tchars(struct tty_struct *tty, struct tchars __user *tchars)
+{
+	struct tchars tmp;
+
+	down_read(&tty->termios_rwsem);
+	tmp.t_intrc = tty->termios.c_cc[VINTR];
+	tmp.t_quitc = tty->termios.c_cc[VQUIT];
+	tmp.t_startc = tty->termios.c_cc[VSTART];
+	tmp.t_stopc = tty->termios.c_cc[VSTOP];
+	tmp.t_eofc = tty->termios.c_cc[VEOF];
+	tmp.t_brkc = tty->termios.c_cc[VEOL2];	/* what is brkc anyway? */
+	up_read(&tty->termios_rwsem);
+	return copy_to_user(tchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
+}
+
+static int set_tchars(struct tty_struct *tty, struct tchars __user *tchars)
+{
+	struct tchars tmp;
+
+	if (copy_from_user(&tmp, tchars, sizeof(tmp)))
+		return -EFAULT;
+	down_write(&tty->termios_rwsem);
+	tty->termios.c_cc[VINTR] = tmp.t_intrc;
+	tty->termios.c_cc[VQUIT] = tmp.t_quitc;
+	tty->termios.c_cc[VSTART] = tmp.t_startc;
+	tty->termios.c_cc[VSTOP] = tmp.t_stopc;
+	tty->termios.c_cc[VEOF] = tmp.t_eofc;
+	tty->termios.c_cc[VEOL2] = tmp.t_brkc;	/* what is brkc anyway? */
+	up_write(&tty->termios_rwsem);
+	return 0;
+}
+#endif
+
+#ifdef TIOCGLTC
+static int get_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
+{
+	struct ltchars tmp;
+
+	down_read(&tty->termios_rwsem);
+	tmp.t_suspc = tty->termios.c_cc[VSUSP];
+	/* what is dsuspc anyway? */
+	tmp.t_dsuspc = tty->termios.c_cc[VSUSP];
+	tmp.t_rprntc = tty->termios.c_cc[VREPRINT];
+	/* what is flushc anyway? */
+	tmp.t_flushc = tty->termios.c_cc[VEOL2];
+	tmp.t_werasc = tty->termios.c_cc[VWERASE];
+	tmp.t_lnextc = tty->termios.c_cc[VLNEXT];
+	up_read(&tty->termios_rwsem);
+	return copy_to_user(ltchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
+}
+
+static int set_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
+{
+	struct ltchars tmp;
+
+	if (copy_from_user(&tmp, ltchars, sizeof(tmp)))
+		return -EFAULT;
+
+	down_write(&tty->termios_rwsem);
+	tty->termios.c_cc[VSUSP] = tmp.t_suspc;
+	/* what is dsuspc anyway? */
+	tty->termios.c_cc[VEOL2] = tmp.t_dsuspc;
+	tty->termios.c_cc[VREPRINT] = tmp.t_rprntc;
+	/* what is flushc anyway? */
+	tty->termios.c_cc[VEOL2] = tmp.t_flushc;
+	tty->termios.c_cc[VWERASE] = tmp.t_werasc;
+	tty->termios.c_cc[VLNEXT] = tmp.t_lnextc;
+	up_write(&tty->termios_rwsem);
+	return 0;
+}
+#endif
+
+/**
+ *	tty_change_softcar	-	carrier change ioctl helper
+ *	@tty: tty to update
+ *	@arg: enable/disable CLOCAL
+ *
+ *	Perform a change to the CLOCAL state and call into the driver
+ *	layer to make it visible. All done with the termios rwsem
+ */
+
+static int tty_change_softcar(struct tty_struct *tty, int arg)
+{
+	int ret = 0;
+	int bit = arg ? CLOCAL : 0;
+	struct ktermios old;
+
+	down_write(&tty->termios_rwsem);
+	old = tty->termios;
+	tty->termios.c_cflag &= ~CLOCAL;
+	tty->termios.c_cflag |= bit;
+	if (tty->ops->set_termios)
+		tty->ops->set_termios(tty, &old);
+	if (C_CLOCAL(tty) != bit)
+		ret = -EINVAL;
+	up_write(&tty->termios_rwsem);
+	return ret;
+}
+
+/**
+ *	tty_mode_ioctl		-	mode related ioctls
+ *	@tty: tty for the ioctl
+ *	@file: file pointer for the tty
+ *	@cmd: command
+ *	@arg: ioctl argument
+ *
+ *	Perform non line discipline specific mode control ioctls. This
+ *	is designed to be called by line disciplines to ensure they provide
+ *	consistent mode setting.
+ */
+
+int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
+			unsigned int cmd, unsigned long arg)
+{
+	struct tty_struct *real_tty;
+	void __user *p = (void __user *)arg;
+	int ret = 0;
+	struct ktermios kterm;
+
+	BUG_ON(file == NULL);
+
+	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+	    tty->driver->subtype == PTY_TYPE_MASTER)
+		real_tty = tty->link;
+	else
+		real_tty = tty;
+
+	switch (cmd) {
+#ifdef TIOCGETP
+	case TIOCGETP:
+		return get_sgttyb(real_tty, (struct sgttyb __user *) arg);
+	case TIOCSETP:
+	case TIOCSETN:
+		return set_sgttyb(real_tty, (struct sgttyb __user *) arg);
+#endif
+#ifdef TIOCGETC
+	case TIOCGETC:
+		return get_tchars(real_tty, p);
+	case TIOCSETC:
+		return set_tchars(real_tty, p);
+#endif
+#ifdef TIOCGLTC
+	case TIOCGLTC:
+		return get_ltchars(real_tty, p);
+	case TIOCSLTC:
+		return set_ltchars(real_tty, p);
+#endif
+	case TCSETSF:
+		return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_OLD);
+	case TCSETSW:
+		return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_OLD);
+	case TCSETS:
+		return set_termios(real_tty, p, TERMIOS_OLD);
+#ifndef TCGETS2
+	case TCGETS:
+		copy_termios(real_tty, &kterm);
+		if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
+			ret = -EFAULT;
+		return ret;
+#else
+	case TCGETS:
+		copy_termios(real_tty, &kterm);
+		if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
+			ret = -EFAULT;
+		return ret;
+	case TCGETS2:
+		copy_termios(real_tty, &kterm);
+		if (kernel_termios_to_user_termios((struct termios2 __user *)arg, &kterm))
+			ret = -EFAULT;
+		return ret;
+	case TCSETSF2:
+		return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT);
+	case TCSETSW2:
+		return set_termios(real_tty, p, TERMIOS_WAIT);
+	case TCSETS2:
+		return set_termios(real_tty, p, 0);
+#endif
+	case TCGETA:
+		return get_termio(real_tty, p);
+	case TCSETAF:
+		return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_TERMIO);
+	case TCSETAW:
+		return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_TERMIO);
+	case TCSETA:
+		return set_termios(real_tty, p, TERMIOS_TERMIO);
+#ifndef TCGETS2
+	case TIOCGLCKTRMIOS:
+		copy_termios_locked(real_tty, &kterm);
+		if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
+			ret = -EFAULT;
+		return ret;
+	case TIOCSLCKTRMIOS:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		copy_termios_locked(real_tty, &kterm);
+		if (user_termios_to_kernel_termios(&kterm,
+					       (struct termios __user *) arg))
+			return -EFAULT;
+		down_write(&real_tty->termios_rwsem);
+		real_tty->termios_locked = kterm;
+		up_write(&real_tty->termios_rwsem);
+		return 0;
+#else
+	case TIOCGLCKTRMIOS:
+		copy_termios_locked(real_tty, &kterm);
+		if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
+			ret = -EFAULT;
+		return ret;
+	case TIOCSLCKTRMIOS:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		copy_termios_locked(real_tty, &kterm);
+		if (user_termios_to_kernel_termios_1(&kterm,
+					       (struct termios __user *) arg))
+			return -EFAULT;
+		down_write(&real_tty->termios_rwsem);
+		real_tty->termios_locked = kterm;
+		up_write(&real_tty->termios_rwsem);
+		return ret;
+#endif
+#ifdef TCGETX
+	case TCGETX:
+	case TCSETX:
+	case TCSETXW:
+	case TCSETXF:
+		return -ENOTTY;
+#endif
+	case TIOCGSOFTCAR:
+		copy_termios(real_tty, &kterm);
+		ret = put_user((kterm.c_cflag & CLOCAL) ? 1 : 0,
+						(int __user *)arg);
+		return ret;
+	case TIOCSSOFTCAR:
+		if (get_user(arg, (unsigned int __user *) arg))
+			return -EFAULT;
+		return tty_change_softcar(real_tty, arg);
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+EXPORT_SYMBOL_GPL(tty_mode_ioctl);
+
+
+/* Caller guarantees ldisc reference is held */
+static int __tty_perform_flush(struct tty_struct *tty, unsigned long arg)
+{
+	struct tty_ldisc *ld = tty->ldisc;
+
+	switch (arg) {
+	case TCIFLUSH:
+		if (ld && ld->ops->flush_buffer) {
+			ld->ops->flush_buffer(tty);
+			tty_unthrottle(tty);
+		}
+		break;
+	case TCIOFLUSH:
+		if (ld && ld->ops->flush_buffer) {
+			ld->ops->flush_buffer(tty);
+			tty_unthrottle(tty);
+		}
+		fallthrough;
+	case TCOFLUSH:
+		tty_driver_flush_buffer(tty);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
+{
+	struct tty_ldisc *ld;
+	int retval = tty_check_change(tty);
+	if (retval)
+		return retval;
+
+	ld = tty_ldisc_ref_wait(tty);
+	retval = __tty_perform_flush(tty, arg);
+	if (ld)
+		tty_ldisc_deref(ld);
+	return retval;
+}
+EXPORT_SYMBOL_GPL(tty_perform_flush);
+
+int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
+		       unsigned int cmd, unsigned long arg)
+{
+	int retval;
+
+	switch (cmd) {
+	case TCXONC:
+		retval = tty_check_change(tty);
+		if (retval)
+			return retval;
+		switch (arg) {
+		case TCOOFF:
+			spin_lock_irq(&tty->flow_lock);
+			if (!tty->flow_stopped) {
+				tty->flow_stopped = 1;
+				__stop_tty(tty);
+			}
+			spin_unlock_irq(&tty->flow_lock);
+			break;
+		case TCOON:
+			spin_lock_irq(&tty->flow_lock);
+			if (tty->flow_stopped) {
+				tty->flow_stopped = 0;
+				__start_tty(tty);
+			}
+			spin_unlock_irq(&tty->flow_lock);
+			break;
+		case TCIOFF:
+			if (STOP_CHAR(tty) != __DISABLED_CHAR)
+				retval = tty_send_xchar(tty, STOP_CHAR(tty));
+			break;
+		case TCION:
+			if (START_CHAR(tty) != __DISABLED_CHAR)
+				retval = tty_send_xchar(tty, START_CHAR(tty));
+			break;
+		default:
+			return -EINVAL;
+		}
+		return retval;
+	case TCFLSH:
+		retval = tty_check_change(tty);
+		if (retval)
+			return retval;
+		return __tty_perform_flush(tty, arg);
+	default:
+		/* Try the mode commands */
+		return tty_mode_ioctl(tty, file, cmd, arg);
+	}
+}
+EXPORT_SYMBOL(n_tty_ioctl_helper);