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/*

 *  linux/drivers/char/pty.c

 *

 *  Copyright (C) 1991, 1992  Linus Torvalds

 *

 *  Added support for a Unix98-style ptmx device.

 *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998

 *  Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to

 *      waiting writers -- Sapan Bhatia <sapan@corewars.org>

 *

 *

 */

#include <linux/module.h>       /* For EXPORT_SYMBOL */

#include <linux/errno.h>

#include <linux/interrupt.h>

#include <linux/tty.h>

#include <linux/tty_flip.h>

#include <linux/fcntl.h>

#include <linux/string.h>

#include <linux/major.h>

#include <linux/mm.h>

#include <linux/init.h>

#include <linux/sysctl.h>

#include <asm/uaccess.h>

#include <asm/system.h>

#include <linux/bitops.h>

#include <linux/devpts_fs.h>

/* These are global because they are accessed in tty_io.c */

#ifdef CONFIG_UNIX98_PTYS

struct tty_driver *ptm_driver;

static struct tty_driver *pts_driver;

#endif

static void pty_close(struct tty_struct * tty, struct file * filp)

{

        if (!tty)

                return;

        if (tty->driver->subtype == PTY_TYPE_MASTER) {

                if (tty->count > 1)

                        printk("master pty_close: count = %d!!\n", tty->count);

        } else {

                if (tty->count > 2)

                        return;

        }

        wake_up_interruptible(&tty->read_wait);

        wake_up_interruptible(&tty->write_wait);

        tty->packet = 0;

        if (!tty->link)

                return;

        tty->link->packet = 0;

        set_bit(TTY_OTHER_CLOSED, &tty->link->flags);

        wake_up_interruptible(&tty->link->read_wait);

        wake_up_interruptible(&tty->link->write_wait);

        if (tty->driver->subtype == PTY_TYPE_MASTER) {

                set_bit(TTY_OTHER_CLOSED, &tty->flags);

#ifdef CONFIG_UNIX98_PTYS

                if (tty->driver == ptm_driver)

                        devpts_pty_kill(tty->index);

#endif

                tty_vhangup(tty->link);

        }

}

/*

 * 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

 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE

 * 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.

 */

static void pty_unthrottle(struct tty_struct * tty)

{

        struct tty_struct *o_tty = tty->link;

        if (!o_tty)

                return;

        tty_wakeup(o_tty);

        set_bit(TTY_THROTTLED, &tty->flags);

}

/*

 * WSH 05/24/97: modified to

 *   (1) use space in tty->flip instead of a shared temp buffer

 *       The flip buffers aren't being used for a pty, so there's lots

 *       of space available.  The buffer is protected by a per-pty

 *       semaphore that should almost never come under contention.

 *   (2) avoid redundant copying for cases where count >> receive_room

 * N.B. Calls from user space may now return an error code instead of

 * a count.

 *

 * FIXME: Our pty_write method is called with our ldisc lock held but

 * not our partners. We can't just take the other one blindly without

 * risking deadlocks.

 */

static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)

{

        struct tty_struct *to = tty->link;

        int     c;

        if (!to || tty->stopped)

                return 0;

        c = to->receive_room;

        if (c > count)

                c = count;

        to->ldisc.receive_buf(to, buf, NULL, c);

        return c;

}

static int pty_write_room(struct tty_struct *tty)

{

        struct tty_struct *to = tty->link;

        if (!to || tty->stopped)

                return 0;

        return to->receive_room;

}

/*

 *      WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior

 *      The chars_in_buffer() value is used by the ldisc select() function

 *      to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).

 *      The pty driver chars_in_buffer() Master/Slave must behave differently:

 *

 *      The Master side needs to allow typed-ahead commands to accumulate

 *      while being canonicalized, so we report "our buffer" as empty until

 *      some threshold is reached, and then report the count. (Any count >

 *      WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock

 *      the count returned must be 0 if no canonical data is available to be

 *      read. (The N_TTY ldisc.chars_in_buffer now knows this.)

 *

 *      The Slave side passes all characters in raw mode to the Master side's

 *      buffer where they can be read immediately, so in this case we can

 *      return the true count in the buffer.

 */

static int pty_chars_in_buffer(struct tty_struct *tty)

{

        struct tty_struct *to = tty->link;

        int count;

        /* We should get the line discipline lock for "tty->link" */

        if (!to || !to->ldisc.chars_in_buffer)

                return 0;

        /* The ldisc must report 0 if no characters available to be read */

        count = to->ldisc.chars_in_buffer(to);

        if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;

        /* Master side driver ... if the other side's read buffer is less than

         * half full, return 0 to allow writers to proceed; otherwise return

         * the count.  This leaves a comfortable margin to avoid overflow,

         * and still allows half a buffer's worth of typed-ahead commands.

         */

        return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);

}

/* Set the lock flag on a pty */

static int pty_set_lock(struct tty_struct *tty, int __user * arg)

{

        int val;

        if (get_user(val,arg))

                return -EFAULT;

        if (val)

                set_bit(TTY_PTY_LOCK, &tty->flags);

        else

                clear_bit(TTY_PTY_LOCK, &tty->flags);

        return 0;

}

static void pty_flush_buffer(struct tty_struct *tty)

{

        struct tty_struct *to = tty->link;

        if (!to)

                return;

        if (to->ldisc.flush_buffer)

                to->ldisc.flush_buffer(to);

        if (to->packet) {

                tty->ctrl_status |= TIOCPKT_FLUSHWRITE;

                wake_up_interruptible(&to->read_wait);

        }

}

static int pty_open(struct tty_struct *tty, struct file * filp)

{

        int     retval = -ENODEV;

        if (!tty || !tty->link)

                goto out;

        retval = -EIO;

        if (test_bit(TTY_OTHER_CLOSED, &tty->flags))

                goto out;

        if (test_bit(TTY_PTY_LOCK, &tty->link->flags))

                goto out;

        if (tty->link->count != 1)

                goto out;

        clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);

        set_bit(TTY_THROTTLED, &tty->flags);

        set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

        retval = 0;

out:

        return retval;

}

static void pty_set_termios(struct tty_struct *tty, struct ktermios *old_termios)

{

        tty->termios->c_cflag &= ~(CSIZE | PARENB);

        tty->termios->c_cflag |= (CS8 | CREAD);

}

static const struct tty_operations pty_ops = {

        .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,

};

/* Traditional BSD devices */

#ifdef CONFIG_LEGACY_PTYS

static struct tty_driver *pty_driver, *pty_slave_driver;

static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,

                         unsigned int cmd, unsigned long arg)

{

        switch (cmd) {

        case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */

                return pty_set_lock(tty, (int __user *) arg);

        }

        return -ENOIOCTLCMD;

}

static int legacy_count = CONFIG_LEGACY_PTY_COUNT;

module_param(legacy_count, int, 0);

static void __init legacy_pty_init(void)

{

        if (legacy_count <= 0)

                return;

        pty_driver = alloc_tty_driver(legacy_count);

        if (!pty_driver)

                panic("Couldn't allocate pty driver");

        pty_slave_driver = alloc_tty_driver(legacy_count);

        if (!pty_slave_driver)

                panic("Couldn't allocate pty slave driver");

        pty_driver->owner = THIS_MODULE;

        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;

        pty_driver->init_termios.c_ispeed = 38400;

        pty_driver->init_termios.c_ospeed = 38400;

        pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;

        pty_driver->other = pty_slave_driver;

        tty_set_operations(pty_driver, &pty_ops);

        pty_driver->ioctl = pty_bsd_ioctl;

        pty_slave_driver->owner = THIS_MODULE;

        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;

        pty_slave_driver->init_termios.c_ispeed = 38400;

        pty_slave_driver->init_termios.c_ospeed = 38400;

        pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |

                                        TTY_DRIVER_REAL_RAW;

        pty_slave_driver->other = pty_driver;

        tty_set_operations(pty_slave_driver, &pty_ops);

        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

/*

 * sysctl support for setting limits on the number of Unix98 ptys allocated.

 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.

 */

int pty_limit = NR_UNIX98_PTY_DEFAULT;

static int pty_limit_min = 0;

static int pty_limit_max = NR_UNIX98_PTY_MAX;

static struct ctl_table pty_table[] = {

        {

                .ctl_name       = PTY_MAX,

                .procname       = "max",

                .maxlen         = sizeof(int),

                .mode           = 0644,

                .data           = &pty_limit,

                .proc_handler   = &proc_dointvec_minmax,

                .strategy       = &sysctl_intvec,

                .extra1         = &pty_limit_min,

                .extra2         = &pty_limit_max,

        }, {

                .ctl_name       = PTY_NR,

                .procname       = "nr",

                .maxlen         = sizeof(int),

                .mode           = 0444,

                .proc_handler   = &proc_dointvec,

        }, {

                .ctl_name       = 0

        }

};

static struct ctl_table pty_kern_table[] = {

        {

                .ctl_name       = KERN_PTY,

                .procname       = "pty",

                .mode           = 0555,

                .child          = pty_table,

        },

        {}

};

static struct ctl_table pty_root_table[] = {

        {

                .ctl_name       = CTL_KERN,

                .procname       = "kernel",

                .mode           = 0555,

                .child          = pty_kern_table,

        },

        {}

};

static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,

                            unsigned int cmd, unsigned long arg)

{

        switch (cmd) {

        case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */

                return pty_set_lock(tty, (int __user *)arg);

        case TIOCGPTN: /* Get PT Number */

                return put_user(tty->index, (unsigned int __user *)arg);

        }

        return -ENOIOCTLCMD;

}

static void __init unix98_pty_init(void)

{

        ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);

        if (!ptm_driver)

                panic("Couldn't allocate Unix98 ptm driver");

        pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);

        if (!pts_driver)

                panic("Couldn't allocate Unix98 pts driver");

        ptm_driver->owner = THIS_MODULE;

        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;

        ptm_driver->init_termios.c_ispeed = 38400;

        ptm_driver->init_termios.c_ospeed = 38400;

        ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |

                TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;

        ptm_driver->other = pts_driver;

        tty_set_operations(ptm_driver, &pty_ops);

        ptm_driver->ioctl = pty_unix98_ioctl;

        pts_driver->owner = THIS_MODULE;

        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;

        pts_driver->init_termios.c_ispeed = 38400;

        pts_driver->init_termios.c_ospeed = 38400;

        pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |

                TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;

        pts_driver->other = ptm_driver;

        tty_set_operations(pts_driver, &pty_ops);

        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");

        pty_table[1].data = &ptm_driver->refcount;

        register_sysctl_table(pty_root_table);

}

#else

static inline void unix98_pty_init(void) { }

#endif

static int __init pty_init(void)

{

        legacy_pty_init();

        unix98_pty_init();

        return 0;

}

module_init(pty_init);