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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/config.h>

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

#include <linux/errno.h>

#include <linux/sched.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/devfs_fs_kernel.h>

#include <asm/uaccess.h>

#include <asm/system.h>

#include <asm/bitops.h>

#define BUILDING_PTY_C 1

#include <linux/devpts_fs.h>

struct pty_struct {

        int     magic;

        wait_queue_head_t open_wait;

};

#define PTY_MAGIC 0x5001

static struct tty_driver pty_driver, pty_slave_driver;

static int pty_refcount;

/* Note: one set of tables for BSD and one for Unix98 */

static struct tty_struct *pty_table[NR_PTYS];

static struct termios *pty_termios[NR_PTYS];

static struct termios *pty_termios_locked[NR_PTYS];

static struct tty_struct *ttyp_table[NR_PTYS];

static struct termios *ttyp_termios[NR_PTYS];

static struct termios *ttyp_termios_locked[NR_PTYS];

static struct pty_struct pty_state[NR_PTYS];

#ifdef CONFIG_UNIX98_PTYS

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

struct tty_driver ptm_driver[UNIX98_NR_MAJORS];

struct tty_driver pts_driver[UNIX98_NR_MAJORS];

static struct tty_struct *ptm_table[UNIX98_NR_MAJORS][NR_PTYS];

static struct termios *ptm_termios[UNIX98_NR_MAJORS][NR_PTYS];

static struct termios *ptm_termios_locked[UNIX98_NR_MAJORS][NR_PTYS];

static struct tty_struct *pts_table[UNIX98_NR_MAJORS][NR_PTYS];

static struct termios *pts_termios[UNIX98_NR_MAJORS][NR_PTYS];

static struct termios *pts_termios_locked[UNIX98_NR_MAJORS][NR_PTYS];

static struct pty_struct ptm_state[UNIX98_NR_MAJORS][NR_PTYS];

#endif

#define MIN(a,b)        ((a) < (b) ? (a) : (b))

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;

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

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

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

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

                set_bit(TTY_OTHER_CLOSED, &tty->flags);

#ifdef CONFIG_UNIX98_PTYS

                {

                        unsigned int major = MAJOR(tty->device) - UNIX98_PTY_MASTER_MAJOR;

                        if ( major < UNIX98_NR_MAJORS ) {

                                devpts_pty_kill( MINOR(tty->device)

                          - tty->driver.minor_start + tty->driver.name_base );

                        }

                }

#endif

                tty_unregister_devfs (&tty->link->driver, MINOR (tty->device));

                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;

        if ((o_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&

            o_tty->ldisc.write_wakeup)

                (o_tty->ldisc.write_wakeup)(o_tty);

        wake_up_interruptible(&o_tty->write_wait);

        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.

 */

static int pty_write(struct tty_struct * tty, int from_user,

                       const unsigned char *buf, int count)

{

        struct tty_struct *to = tty->link;

        int     c=0, n, room;

        char    *temp_buffer;

        if (!to || tty->stopped)

                return 0;

        if (from_user) {

                down(&tty->flip.pty_sem);

                temp_buffer = &tty->flip.char_buf[0];

                while (count > 0) {

                        /* check space so we don't copy needlessly */

                        n = to->ldisc.receive_room(to);

                        if (n > count)

                                n = count;

                        if (!n) break;

                        n  = MIN(n, PTY_BUF_SIZE);

                        n -= copy_from_user(temp_buffer, buf, n);

                        if (!n) {

                                if (!c)

                                        c = -EFAULT;

                                break;

                        }

                        /* check again in case the buffer filled up */

                        room = to->ldisc.receive_room(to);

                        if (n > room)

                                n = room;

                        if (!n) break;

                        buf   += n;

                        c     += n;

                        count -= n;

                        to->ldisc.receive_buf(to, temp_buffer, 0, n);

                }

                up(&tty->flip.pty_sem);

        } else {

                c = to->ldisc.receive_room(to);

                if (c > count)

                        c = count;

                to->ldisc.receive_buf(to, buf, 0, 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->ldisc.receive_room(to);

}

/*

 *      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;

        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);

}

/*

 * Return the device number of a Unix98 PTY (only!).  This lets us open a

 * master pty with the multi-headed ptmx device, then find out which

 * one we got after it is open, with an ioctl.

 */

#ifdef CONFIG_UNIX98_PTYS

static int pty_get_device_number(struct tty_struct *tty, unsigned int *value)

{

        unsigned int result = MINOR(tty->device)

                - tty->driver.minor_start + tty->driver.name_base;

        return put_user(result, value);

}

#endif

/* Set the lock flag on a pty */

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

                        unsigned int cmd, unsigned long arg)

{

        if (!tty) {

                printk("pty_ioctl called with NULL tty!\n");

                return -EIO;

        }

        switch(cmd) {

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

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

        }

        return -ENOIOCTLCMD;

}

#ifdef CONFIG_UNIX98_PTYS

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

                            unsigned int cmd, unsigned long arg)

{

        if (!tty) {

                printk("pty_unix98_ioctl called with NULL tty!\n");

                return -EIO;

        }

        switch(cmd) {

        case TIOCGPTN: /* Get PT Number */

                return pty_get_device_number(tty, (unsigned int *)arg);

        }

        return pty_bsd_ioctl(tty,file,cmd,arg);

}

#endif

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;

        int     line;

        struct  pty_struct *pty;

        retval = -ENODEV;

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

                goto out;

        line = MINOR(tty->device) - tty->driver.minor_start;

        if ((line < 0) || (line >= NR_PTYS))

                goto out;

        pty = (struct pty_struct *)(tty->driver.driver_state) + line;

        tty->driver_data = pty;

        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);

        wake_up_interruptible(&pty->open_wait);

        set_bit(TTY_THROTTLED, &tty->flags);

        set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

        /*  Register a slave for the master  */

        if (tty->driver.major == PTY_MASTER_MAJOR)

                tty_register_devfs(&tty->link->driver,

                                   DEVFS_FL_CURRENT_OWNER | DEVFS_FL_WAIT,

                                   tty->link->driver.minor_start +

                                   MINOR(tty->device)-tty->driver.minor_start);

        retval = 0;

out:

        return retval;

}

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

{

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

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

}

int __init pty_init(void)

{

        int i;

        /* Traditional BSD devices */

        memset(&pty_state, 0, sizeof(pty_state));

        for (i = 0; i < NR_PTYS; i++)

                init_waitqueue_head(&pty_state[i].open_wait);

        memset(&pty_driver, 0, sizeof(struct tty_driver));

        pty_driver.magic = TTY_DRIVER_MAGIC;

        pty_driver.driver_name = "pty_master";

#ifdef CONFIG_DEVFS_FS

        pty_driver.name = "pty/m%d";

#else

        pty_driver.name = "pty";

#endif

        pty_driver.major = PTY_MASTER_MAJOR;

        pty_driver.minor_start = 0;

        pty_driver.num = NR_PTYS;

        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.flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;

        pty_driver.refcount = &pty_refcount;

        pty_driver.table = pty_table;

        pty_driver.termios = pty_termios;

        pty_driver.termios_locked = pty_termios_locked;

        pty_driver.driver_state = pty_state;

        pty_driver.other = &pty_slave_driver;

        pty_driver.open = pty_open;

        pty_driver.close = pty_close;

        pty_driver.write = pty_write;

        pty_driver.write_room = pty_write_room;

        pty_driver.flush_buffer = pty_flush_buffer;

        pty_driver.chars_in_buffer = pty_chars_in_buffer;

        pty_driver.unthrottle = pty_unthrottle;

        pty_driver.set_termios = pty_set_termios;

        pty_slave_driver = pty_driver;

        pty_slave_driver.driver_name = "pty_slave";

        pty_slave_driver.proc_entry = 0;

#ifdef CONFIG_DEVFS_FS

        pty_slave_driver.name = "pty/s%d";

#else

        pty_slave_driver.name = "ttyp";

#endif

        pty_slave_driver.subtype = PTY_TYPE_SLAVE;

        pty_slave_driver.major = PTY_SLAVE_MAJOR;

        pty_slave_driver.minor_start = 0;

        pty_slave_driver.init_termios = tty_std_termios;

        pty_slave_driver.init_termios.c_cflag = B38400 | CS8 | CREAD;

        /* Slave ptys are registered when their corresponding master pty

         * is opened, and unregistered when the pair is closed.

         */

        pty_slave_driver.flags |= TTY_DRIVER_NO_DEVFS;

        pty_slave_driver.table = ttyp_table;

        pty_slave_driver.termios = ttyp_termios;

        pty_slave_driver.termios_locked = ttyp_termios_locked;

        pty_slave_driver.driver_state = pty_state;

        pty_slave_driver.other = &pty_driver;

        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");

        /*

         * only the master pty gets this ioctl (which is why we

         * assign it here, instead of up with the rest of the

         * pty_driver initialization. <cananian@alumni.princeton.edu>

         */

        pty_driver.ioctl = pty_bsd_ioctl;

        /* Unix98 devices */

#ifdef CONFIG_UNIX98_PTYS

        devfs_mk_dir (NULL, "pts", NULL);

        printk("pty: %d Unix98 ptys configured\n", UNIX98_NR_MAJORS*NR_PTYS);

        for ( i = 0 ; i < UNIX98_NR_MAJORS ; i++ ) {

                int j;

                ptm_driver[i] = pty_driver;

                ptm_driver[i].name = "ptm";

                ptm_driver[i].proc_entry = 0;

                ptm_driver[i].major = UNIX98_PTY_MASTER_MAJOR+i;

                ptm_driver[i].minor_start = 0;

                ptm_driver[i].name_base = i*NR_PTYS;

                ptm_driver[i].num = NR_PTYS;

                ptm_driver[i].other = &pts_driver[i];

                ptm_driver[i].flags |= TTY_DRIVER_NO_DEVFS;

                ptm_driver[i].table = ptm_table[i];

                ptm_driver[i].termios = ptm_termios[i];

                ptm_driver[i].termios_locked = ptm_termios_locked[i];

                ptm_driver[i].driver_state = ptm_state[i];

                for (j = 0; j < NR_PTYS; j++)

                        init_waitqueue_head(&ptm_state[i][j].open_wait);

                pts_driver[i] = pty_slave_driver;

#ifdef CONFIG_DEVFS_FS

                pts_driver[i].name = "pts/%d";

#else

                pts_driver[i].name = "pts";

#endif

                pts_driver[i].proc_entry = 0;

                pts_driver[i].major = UNIX98_PTY_SLAVE_MAJOR+i;

                pts_driver[i].minor_start = 0;

                pts_driver[i].name_base = i*NR_PTYS;

                pts_driver[i].num = ptm_driver[i].num;

                pts_driver[i].other = &ptm_driver[i];

                pts_driver[i].table = pts_table[i];

                pts_driver[i].termios = pts_termios[i];

                pts_driver[i].termios_locked = pts_termios_locked[i];

                pts_driver[i].driver_state = ptm_state[i];

                ptm_driver[i].ioctl = pty_unix98_ioctl;

                if (tty_register_driver(&ptm_driver[i]))

                        panic("Couldn't register Unix98 ptm driver major %d",

                              ptm_driver[i].major);

                if (tty_register_driver(&pts_driver[i]))

                        panic("Couldn't register Unix98 pts driver major %d",

                              pts_driver[i].major);

        }

#endif

        return 0;

}