pty.c 22.5 KB
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/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Added support for a Unix98-style ptmx device.
 *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
 *
 */

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#include <linux/module.h>
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#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/fcntl.h>
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#include <linux/sched.h>
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#include <linux/string.h>
#include <linux/major.h>
#include <linux/mm.h>
#include <linux/init.h>
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#include <linux/device.h>
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#include <linux/uaccess.h>
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#include <linux/bitops.h>
#include <linux/devpts_fs.h>
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#include <linux/slab.h>
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#include <linux/mutex.h>
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#include <linux/poll.h>
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#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
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#ifdef CONFIG_UNIX98_PTYS
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static struct tty_driver *ptm_driver;
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static struct tty_driver *pts_driver;
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static DEFINE_MUTEX(devpts_mutex);
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#endif

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static void pty_close(struct tty_struct *tty, struct file *filp)
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{
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	BUG_ON(!tty);
	if (tty->driver->subtype == PTY_TYPE_MASTER)
		WARN_ON(tty->count > 1);
	else {
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		if (test_bit(TTY_IO_ERROR, &tty->flags))
			return;
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		if (tty->count > 2)
			return;
	}
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	set_bit(TTY_IO_ERROR, &tty->flags);
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	wake_up_interruptible(&tty->read_wait);
	wake_up_interruptible(&tty->write_wait);
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	spin_lock_irq(&tty->ctrl_lock);
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	tty->packet = 0;
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	spin_unlock_irq(&tty->ctrl_lock);
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	/* Review - krefs on tty_link ?? */
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	if (!tty->link)
		return;
	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
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	tty_flip_buffer_push(tty->link->port);
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	wake_up_interruptible(&tty->link->write_wait);
	if (tty->driver->subtype == PTY_TYPE_MASTER) {
		set_bit(TTY_OTHER_CLOSED, &tty->flags);
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#ifdef CONFIG_UNIX98_PTYS
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		if (tty->driver == ptm_driver) {
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			mutex_lock(&devpts_mutex);
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			if (tty->link->driver_data)
				devpts_pty_kill(tty->link->driver_data);
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			mutex_unlock(&devpts_mutex);
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		}
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#endif
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		tty_vhangup(tty->link);
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	}
}

/*
 * The unthrottle routine is called by the line discipline to signal
 * that it can receive more characters.  For PTY's, the TTY_THROTTLED
 * flag is always set, to force the line discipline to always call the
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 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
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 * characters in the queue.  This is necessary since each time this
 * happens, we need to wake up any sleeping processes that could be
 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
 * for the pty buffer to be drained.
 */
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static void pty_unthrottle(struct tty_struct *tty)
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{
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	tty_wakeup(tty->link);
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	set_bit(TTY_THROTTLED, &tty->flags);
}

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/**
 *	pty_write		-	write to a pty
 *	@tty: the tty we write from
 *	@buf: kernel buffer of data
 *	@count: bytes to write
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 *
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 *	Our "hardware" write method. Data is coming from the ldisc which
 *	may be in a non sleeping state. We simply throw this at the other
 *	end of the link as if we were an IRQ handler receiving stuff for
 *	the other side of the pty/tty pair.
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 */
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static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
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{
	struct tty_struct *to = tty->link;

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	if (tty->stopped)
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		return 0;
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	if (c > 0) {
		/* Stuff the data into the input queue of the other end */
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		c = tty_insert_flip_string(to->port, buf, c);
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		/* And shovel */
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		if (c)
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			tty_flip_buffer_push(to->port);
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	}
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	return c;
}

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/**
 *	pty_write_room	-	write space
 *	@tty: tty we are writing from
 *
 *	Report how many bytes the ldisc can send into the queue for
 *	the other device.
 */

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static int pty_write_room(struct tty_struct *tty)
{
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	if (tty->stopped)
		return 0;
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	return tty_buffer_space_avail(tty->link->port);
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}

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/**
 *	pty_chars_in_buffer	-	characters currently in our tx queue
 *	@tty: our tty
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 *
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 *	Report how much we have in the transmit queue. As everything is
 *	instantly at the other end this is easy to implement.
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 */
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static int pty_chars_in_buffer(struct tty_struct *tty)
{
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	return 0;
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}

/* Set the lock flag on a pty */
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static int pty_set_lock(struct tty_struct *tty, int __user *arg)
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{
	int val;
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	if (get_user(val, arg))
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		return -EFAULT;
	if (val)
		set_bit(TTY_PTY_LOCK, &tty->flags);
	else
		clear_bit(TTY_PTY_LOCK, &tty->flags);
	return 0;
}

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static int pty_get_lock(struct tty_struct *tty, int __user *arg)
{
	int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
	return put_user(locked, arg);
}

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/* Set the packet mode on a pty */
static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
{
	int pktmode;

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

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	spin_lock_irq(&tty->ctrl_lock);
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	if (pktmode) {
		if (!tty->packet) {
			tty->link->ctrl_status = 0;
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			smp_mb();
			tty->packet = 1;
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		}
	} else
		tty->packet = 0;
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	spin_unlock_irq(&tty->ctrl_lock);
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	return 0;
}

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/* Get the packet mode of a pty */
static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
{
	int pktmode = tty->packet;
	return put_user(pktmode, arg);
}

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/* Send a signal to the slave */
static int pty_signal(struct tty_struct *tty, int sig)
{
	struct pid *pgrp;

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	if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
		return -EINVAL;

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	if (tty->link) {
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		pgrp = tty_get_pgrp(tty->link);
		if (pgrp)
			kill_pgrp(pgrp, sig, 1);
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		put_pid(pgrp);
	}
	return 0;
}

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static void pty_flush_buffer(struct tty_struct *tty)
{
	struct tty_struct *to = tty->link;
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	struct tty_ldisc *ld;
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	if (!to)
		return;
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	ld = tty_ldisc_ref(to);
	tty_buffer_flush(to, ld);
	if (ld)
		tty_ldisc_deref(ld);

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	if (to->packet) {
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		spin_lock_irq(&tty->ctrl_lock);
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		tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
		wake_up_interruptible(&to->read_wait);
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		spin_unlock_irq(&tty->ctrl_lock);
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	}
}

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static int pty_open(struct tty_struct *tty, struct file *filp)
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{
	if (!tty || !tty->link)
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		return -ENODEV;
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	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
		goto out;
	if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
		goto out;
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	if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
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		goto out;

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	clear_bit(TTY_IO_ERROR, &tty->flags);
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	/* TTY_OTHER_CLOSED must be cleared before TTY_OTHER_DONE */
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	clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
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	clear_bit(TTY_OTHER_DONE, &tty->link->flags);
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	set_bit(TTY_THROTTLED, &tty->flags);
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	return 0;

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out:
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	set_bit(TTY_IO_ERROR, &tty->flags);
	return -EIO;
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}

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static void pty_set_termios(struct tty_struct *tty,
					struct ktermios *old_termios)
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{
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	/* See if packet mode change of state. */
	if (tty->link && tty->link->packet) {
		int extproc = (old_termios->c_lflag & EXTPROC) |
				(tty->termios.c_lflag & EXTPROC);
		int old_flow = ((old_termios->c_iflag & IXON) &&
				(old_termios->c_cc[VSTOP] == '\023') &&
				(old_termios->c_cc[VSTART] == '\021'));
		int new_flow = (I_IXON(tty) &&
				STOP_CHAR(tty) == '\023' &&
				START_CHAR(tty) == '\021');
		if ((old_flow != new_flow) || extproc) {
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			spin_lock_irq(&tty->ctrl_lock);
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			if (old_flow != new_flow) {
				tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
				if (new_flow)
					tty->ctrl_status |= TIOCPKT_DOSTOP;
				else
					tty->ctrl_status |= TIOCPKT_NOSTOP;
			}
			if (extproc)
				tty->ctrl_status |= TIOCPKT_IOCTL;
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			spin_unlock_irq(&tty->ctrl_lock);
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			wake_up_interruptible(&tty->link->read_wait);
		}
	}

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	tty->termios.c_cflag &= ~(CSIZE | PARENB);
	tty->termios.c_cflag |= (CS8 | CREAD);
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}

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/**
 *	pty_do_resize		-	resize event
 *	@tty: tty being resized
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 *	@ws: window size being set.
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 *
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 *	Update the termios variables and send the necessary signals to
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 *	peform a terminal resize correctly
 */

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static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
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{
	struct pid *pgrp, *rpgrp;
	struct tty_struct *pty = tty->link;

	/* For a PTY we need to lock the tty side */
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	mutex_lock(&tty->winsize_mutex);
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	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
		goto done;

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	/* Signal the foreground process group of both ptys */
	pgrp = tty_get_pgrp(tty);
	rpgrp = tty_get_pgrp(pty);
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	if (pgrp)
		kill_pgrp(pgrp, SIGWINCH, 1);
	if (rpgrp != pgrp && rpgrp)
		kill_pgrp(rpgrp, SIGWINCH, 1);

	put_pid(pgrp);
	put_pid(rpgrp);

	tty->winsize = *ws;
	pty->winsize = *ws;	/* Never used so will go away soon */
done:
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	mutex_unlock(&tty->winsize_mutex);
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	return 0;
}

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/**
 *	pty_start - start() handler
 *	pty_stop  - stop() handler
 *	@tty: tty being flow-controlled
 *
 *	Propagates the TIOCPKT status to the master pty.
 *
 *	NB: only the master pty can be in packet mode so only the slave
 *	    needs start()/stop() handlers
 */
static void pty_start(struct tty_struct *tty)
{
	unsigned long flags;

	if (tty->link && tty->link->packet) {
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		spin_lock_irqsave(&tty->ctrl_lock, flags);
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		tty->ctrl_status &= ~TIOCPKT_STOP;
		tty->ctrl_status |= TIOCPKT_START;
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		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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		wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
	}
}

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

	if (tty->link && tty->link->packet) {
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		spin_lock_irqsave(&tty->ctrl_lock, flags);
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		tty->ctrl_status &= ~TIOCPKT_START;
		tty->ctrl_status |= TIOCPKT_STOP;
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		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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		wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
	}
}

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/**
 *	pty_common_install		-	set up the pty pair
 *	@driver: the pty driver
 *	@tty: the tty being instantiated
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 *	@legacy: true if this is BSD style
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 *
 *	Perform the initial set up for the tty/pty pair. Called from the
 *	tty layer when the port is first opened.
 *
 *	Locking: the caller must hold the tty_mutex
 */
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static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
		bool legacy)
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{
	struct tty_struct *o_tty;
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	struct tty_port *ports[2];
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	int idx = tty->index;
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	int retval = -ENOMEM;
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	/* Opening the slave first has always returned -EIO */
	if (driver->subtype != PTY_TYPE_MASTER)
		return -EIO;

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	ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
	ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
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	if (!ports[0] || !ports[1])
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		goto err;
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	if (!try_module_get(driver->other->owner)) {
		/* This cannot in fact currently happen */
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		goto err;
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	}
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	o_tty = alloc_tty_struct(driver->other, idx);
	if (!o_tty)
		goto err_put_module;
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	tty_set_lock_subclass(o_tty);
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	lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
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	if (legacy) {
		/* We always use new tty termios data so we can do this
		   the easy way .. */
		retval = tty_init_termios(tty);
		if (retval)
			goto err_deinit_tty;

		retval = tty_init_termios(o_tty);
		if (retval)
			goto err_free_termios;

		driver->other->ttys[idx] = o_tty;
		driver->ttys[idx] = tty;
	} else {
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		memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
		tty->termios = driver->init_termios;
		memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
		o_tty->termios = driver->other->init_termios;
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	}
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	/*
	 * Everything allocated ... set up the o_tty structure.
	 */
	tty_driver_kref_get(driver->other);
	/* Establish the links in both directions */
	tty->link   = o_tty;
	o_tty->link = tty;
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	tty_port_init(ports[0]);
	tty_port_init(ports[1]);
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	tty_buffer_set_limit(ports[0], 8192);
	tty_buffer_set_limit(ports[1], 8192);
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	o_tty->port = ports[0];
	tty->port = ports[1];
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	o_tty->port->itty = o_tty;
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	tty_buffer_set_lock_subclass(o_tty->port);

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	tty_driver_kref_get(driver);
	tty->count++;
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	o_tty->count++;
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	return 0;
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err_free_termios:
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	if (legacy)
		tty_free_termios(tty);
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err_deinit_tty:
	deinitialize_tty_struct(o_tty);
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	free_tty_struct(o_tty);
err_put_module:
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	module_put(driver->other->owner);
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err:
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	kfree(ports[0]);
	kfree(ports[1]);
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	return retval;
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}

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static void pty_cleanup(struct tty_struct *tty)
{
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	tty_port_put(tty->port);
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}

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/* Traditional BSD devices */
#ifdef CONFIG_LEGACY_PTYS

static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
{
	return pty_common_install(driver, tty, true);
}

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static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
{
	struct tty_struct *pair = tty->link;
	driver->ttys[tty->index] = NULL;
	if (pair)
		pair->driver->ttys[pair->index] = NULL;
}

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static int pty_bsd_ioctl(struct tty_struct *tty,
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			 unsigned int cmd, unsigned long arg)
{
	switch (cmd) {
	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
		return pty_set_lock(tty, (int __user *) arg);
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	case TIOCGPTLCK: /* Get PT Lock status */
		return pty_get_lock(tty, (int __user *)arg);
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	case TIOCPKT: /* Set PT packet mode */
		return pty_set_pktmode(tty, (int __user *)arg);
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	case TIOCGPKT: /* Get PT packet mode */
		return pty_get_pktmode(tty, (int __user *)arg);
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	case TIOCSIG:    /* Send signal to other side of pty */
		return pty_signal(tty, (int) arg);
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	case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
		return -EINVAL;
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	}
	return -ENOIOCTLCMD;
}

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static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
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/*
 * not really modular, but the easiest way to keep compat with existing
 * bootargs behaviour is to continue using module_param here.
 */
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module_param(legacy_count, int, 0);

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/*
 * The master side of a pty can do TIOCSPTLCK and thus
 * has pty_bsd_ioctl.
 */
static const struct tty_operations master_pty_ops_bsd = {
	.install = pty_install,
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	.open = pty_open,
	.close = pty_close,
	.write = pty_write,
	.write_room = pty_write_room,
	.flush_buffer = pty_flush_buffer,
	.chars_in_buffer = pty_chars_in_buffer,
	.unthrottle = pty_unthrottle,
	.ioctl = pty_bsd_ioctl,
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	.cleanup = pty_cleanup,
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	.resize = pty_resize,
	.remove = pty_remove
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};

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static const struct tty_operations slave_pty_ops_bsd = {
	.install = pty_install,
	.open = pty_open,
	.close = pty_close,
	.write = pty_write,
	.write_room = pty_write_room,
	.flush_buffer = pty_flush_buffer,
	.chars_in_buffer = pty_chars_in_buffer,
	.unthrottle = pty_unthrottle,
	.set_termios = pty_set_termios,
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	.cleanup = pty_cleanup,
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	.resize = pty_resize,
540 541
	.start = pty_start,
	.stop = pty_stop,
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	.remove = pty_remove
543 544
};

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static void __init legacy_pty_init(void)
{
547 548
	struct tty_driver *pty_driver, *pty_slave_driver;

549 550
	if (legacy_count <= 0)
		return;
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552 553 554 555
	pty_driver = tty_alloc_driver(legacy_count,
			TTY_DRIVER_RESET_TERMIOS |
			TTY_DRIVER_REAL_RAW |
			TTY_DRIVER_DYNAMIC_ALLOC);
556
	if (IS_ERR(pty_driver))
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		panic("Couldn't allocate pty driver");

559 560 561 562
	pty_slave_driver = tty_alloc_driver(legacy_count,
			TTY_DRIVER_RESET_TERMIOS |
			TTY_DRIVER_REAL_RAW |
			TTY_DRIVER_DYNAMIC_ALLOC);
563
	if (IS_ERR(pty_slave_driver))
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		panic("Couldn't allocate pty slave driver");

	pty_driver->driver_name = "pty_master";
	pty_driver->name = "pty";
	pty_driver->major = PTY_MASTER_MAJOR;
	pty_driver->minor_start = 0;
	pty_driver->type = TTY_DRIVER_TYPE_PTY;
	pty_driver->subtype = PTY_TYPE_MASTER;
	pty_driver->init_termios = tty_std_termios;
	pty_driver->init_termios.c_iflag = 0;
	pty_driver->init_termios.c_oflag = 0;
	pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
	pty_driver->init_termios.c_lflag = 0;
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	pty_driver->init_termios.c_ispeed = 38400;
	pty_driver->init_termios.c_ospeed = 38400;
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	pty_driver->other = pty_slave_driver;
580
	tty_set_operations(pty_driver, &master_pty_ops_bsd);
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	pty_slave_driver->driver_name = "pty_slave";
	pty_slave_driver->name = "ttyp";
	pty_slave_driver->major = PTY_SLAVE_MAJOR;
	pty_slave_driver->minor_start = 0;
	pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
	pty_slave_driver->subtype = PTY_TYPE_SLAVE;
	pty_slave_driver->init_termios = tty_std_termios;
	pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
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	pty_slave_driver->init_termios.c_ispeed = 38400;
	pty_slave_driver->init_termios.c_ospeed = 38400;
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	pty_slave_driver->other = pty_driver;
593
	tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
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	if (tty_register_driver(pty_driver))
		panic("Couldn't register pty driver");
	if (tty_register_driver(pty_slave_driver))
		panic("Couldn't register pty slave driver");
}
#else
static inline void legacy_pty_init(void) { }
#endif

/* Unix98 devices */
#ifdef CONFIG_UNIX98_PTYS

607 608
static struct cdev ptmx_cdev;

609
static int pty_unix98_ioctl(struct tty_struct *tty,
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			    unsigned int cmd, unsigned long arg)
{
	switch (cmd) {
	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
		return pty_set_lock(tty, (int __user *)arg);
615 616
	case TIOCGPTLCK: /* Get PT Lock status */
		return pty_get_lock(tty, (int __user *)arg);
617 618
	case TIOCPKT: /* Set PT packet mode */
		return pty_set_pktmode(tty, (int __user *)arg);
619 620
	case TIOCGPKT: /* Get PT packet mode */
		return pty_get_pktmode(tty, (int __user *)arg);
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	case TIOCGPTN: /* Get PT Number */
		return put_user(tty->index, (unsigned int __user *)arg);
623 624
	case TIOCSIG:    /* Send signal to other side of pty */
		return pty_signal(tty, (int) arg);
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	}

	return -ENOIOCTLCMD;
}

630 631 632 633 634 635 636 637 638
/**
 *	ptm_unix98_lookup	-	find a pty master
 *	@driver: ptm driver
 *	@idx: tty index
 *
 *	Look up a pty master device. Called under the tty_mutex for now.
 *	This provides our locking.
 */

639 640
static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
		struct inode *ptm_inode, int idx)
641
{
642 643
	/* Master must be open via /dev/ptmx */
	return ERR_PTR(-EIO);
644 645 646 647 648 649 650 651
}

/**
 *	pts_unix98_lookup	-	find a pty slave
 *	@driver: pts driver
 *	@idx: tty index
 *
 *	Look up a pty master device. Called under the tty_mutex for now.
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 *	This provides our locking for the tty pointer.
653 654
 */

655 656
static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
		struct inode *pts_inode, int idx)
657
{
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	struct tty_struct *tty;

	mutex_lock(&devpts_mutex);
661
	tty = devpts_get_priv(pts_inode);
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	mutex_unlock(&devpts_mutex);
663 664 665 666 667 668
	/* Master must be open before slave */
	if (!tty)
		return ERR_PTR(-EIO);
	return tty;
}

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/* We have no need to install and remove our tty objects as devpts does all
   the work for us */

672
static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
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{
674
	return pty_common_install(driver, tty, false);
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}

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static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
A
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{
}

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/* this is called once with whichever end is closed last */
static void pty_unix98_shutdown(struct tty_struct *tty)
{
	devpts_kill_index(tty->driver_data, tty->index);
}

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static const struct tty_operations ptm_unix98_ops = {
688
	.lookup = ptm_unix98_lookup,
689
	.install = pty_unix98_install,
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	.remove = pty_unix98_remove,
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	.open = pty_open,
	.close = pty_close,
	.write = pty_write,
	.write_room = pty_write_room,
	.flush_buffer = pty_flush_buffer,
	.chars_in_buffer = pty_chars_in_buffer,
	.unthrottle = pty_unthrottle,
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	.ioctl = pty_unix98_ioctl,
699
	.resize = pty_resize,
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	.shutdown = pty_unix98_shutdown,
701
	.cleanup = pty_cleanup
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};

704 705
static const struct tty_operations pty_unix98_ops = {
	.lookup = pts_unix98_lookup,
706
	.install = pty_unix98_install,
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	.remove = pty_unix98_remove,
708 709 710 711 712 713 714 715
	.open = pty_open,
	.close = pty_close,
	.write = pty_write,
	.write_room = pty_write_room,
	.flush_buffer = pty_flush_buffer,
	.chars_in_buffer = pty_chars_in_buffer,
	.unthrottle = pty_unthrottle,
	.set_termios = pty_set_termios,
716 717
	.start = pty_start,
	.stop = pty_stop,
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	.shutdown = pty_unix98_shutdown,
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	.cleanup = pty_cleanup,
720
};
721 722 723 724 725 726 727 728 729

/**
 *	ptmx_open		-	open a unix 98 pty master
 *	@inode: inode of device file
 *	@filp: file pointer to tty
 *
 *	Allocate a unix98 pty master device from the ptmx driver.
 *
 *	Locking: tty_mutex protects the init_dev work. tty->count should
730
 *		protect the rest.
731 732 733
 *		allocated_ptys_lock handles the list of free pty numbers
 */

734
static int ptmx_open(struct inode *inode, struct file *filp)
735 736
{
	struct tty_struct *tty;
737
	struct inode *slave_inode;
738 739 740 741 742
	int retval;
	int index;

	nonseekable_open(inode, filp);

743 744 745
	/* We refuse fsnotify events on ptmx, since it's a shared resource */
	filp->f_mode |= FMODE_NONOTIFY;

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	retval = tty_alloc_file(filp);
	if (retval)
		return retval;

750
	/* find a device that is not in use. */
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	mutex_lock(&devpts_mutex);
752
	index = devpts_new_index(inode);
J
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753 754
	if (index < 0) {
		retval = index;
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		mutex_unlock(&devpts_mutex);
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		goto err_file;
	}
758

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	mutex_unlock(&devpts_mutex);

761
	mutex_lock(&tty_mutex);
762
	tty = tty_init_dev(ptm_driver, index);
763

764 765
	if (IS_ERR(tty)) {
		retval = PTR_ERR(tty);
766
		goto out;
767
	}
768

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	/* The tty returned here is locked so we can safely
	   drop the mutex */
	mutex_unlock(&tty_mutex);

773
	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
774
	tty->driver_data = inode;
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	tty_add_file(tty, filp);
777

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	slave_inode = devpts_pty_new(inode,
			MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
			tty->link);
781 782
	if (IS_ERR(slave_inode)) {
		retval = PTR_ERR(slave_inode);
783
		goto err_release;
784
	}
785
	tty->link->driver_data = slave_inode;
786 787

	retval = ptm_driver->ops->open(tty, filp);
788
	if (retval)
789 790
		goto err_release;

791
	tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
792

A
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	tty_unlock(tty);
794 795
	return 0;
err_release:
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796
	tty_unlock(tty);
797
	tty_release(inode, filp);
798 799
	return retval;
out:
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	mutex_unlock(&tty_mutex);
J
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801
	devpts_kill_index(inode, index);
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err_file:
	tty_free_file(filp);
804
	return retval;
805 806 807 808
}

static struct file_operations ptmx_fops;

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static void __init unix98_pty_init(void)
{
811 812 813 814 815 816
	ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
			TTY_DRIVER_RESET_TERMIOS |
			TTY_DRIVER_REAL_RAW |
			TTY_DRIVER_DYNAMIC_DEV |
			TTY_DRIVER_DEVPTS_MEM |
			TTY_DRIVER_DYNAMIC_ALLOC);
817
	if (IS_ERR(ptm_driver))
L
Linus Torvalds 已提交
818
		panic("Couldn't allocate Unix98 ptm driver");
819 820 821 822 823 824
	pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
			TTY_DRIVER_RESET_TERMIOS |
			TTY_DRIVER_REAL_RAW |
			TTY_DRIVER_DYNAMIC_DEV |
			TTY_DRIVER_DEVPTS_MEM |
			TTY_DRIVER_DYNAMIC_ALLOC);
825
	if (IS_ERR(pts_driver))
L
Linus Torvalds 已提交
826 827 828 829 830 831 832 833 834 835 836 837 838
		panic("Couldn't allocate Unix98 pts driver");

	ptm_driver->driver_name = "pty_master";
	ptm_driver->name = "ptm";
	ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
	ptm_driver->minor_start = 0;
	ptm_driver->type = TTY_DRIVER_TYPE_PTY;
	ptm_driver->subtype = PTY_TYPE_MASTER;
	ptm_driver->init_termios = tty_std_termios;
	ptm_driver->init_termios.c_iflag = 0;
	ptm_driver->init_termios.c_oflag = 0;
	ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
	ptm_driver->init_termios.c_lflag = 0;
A
Alan Cox 已提交
839 840
	ptm_driver->init_termios.c_ispeed = 38400;
	ptm_driver->init_termios.c_ospeed = 38400;
L
Linus Torvalds 已提交
841
	ptm_driver->other = pts_driver;
A
Alan Cox 已提交
842
	tty_set_operations(ptm_driver, &ptm_unix98_ops);
L
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843 844 845 846 847 848 849 850 851

	pts_driver->driver_name = "pty_slave";
	pts_driver->name = "pts";
	pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
	pts_driver->minor_start = 0;
	pts_driver->type = TTY_DRIVER_TYPE_PTY;
	pts_driver->subtype = PTY_TYPE_SLAVE;
	pts_driver->init_termios = tty_std_termios;
	pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
A
Alan Cox 已提交
852 853
	pts_driver->init_termios.c_ispeed = 38400;
	pts_driver->init_termios.c_ospeed = 38400;
L
Linus Torvalds 已提交
854
	pts_driver->other = ptm_driver;
855
	tty_set_operations(pts_driver, &pty_unix98_ops);
A
Alan Cox 已提交
856

L
Linus Torvalds 已提交
857 858 859 860 861
	if (tty_register_driver(ptm_driver))
		panic("Couldn't register Unix98 ptm driver");
	if (tty_register_driver(pts_driver))
		panic("Couldn't register Unix98 pts driver");

862 863 864 865 866 867 868
	/* Now create the /dev/ptmx special device */
	tty_default_fops(&ptmx_fops);
	ptmx_fops.open = ptmx_open;

	cdev_init(&ptmx_cdev, &ptmx_fops);
	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
C
Cong Ding 已提交
869
		panic("Couldn't register /dev/ptmx driver");
870
	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
L
Linus Torvalds 已提交
871
}
872

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873 874 875 876 877 878 879 880 881 882
#else
static inline void unix98_pty_init(void) { }
#endif

static int __init pty_init(void)
{
	legacy_pty_init();
	unix98_pty_init();
	return 0;
}
883
device_initcall(pty_init);