git.oblomov.eu Git - linux-2.6/blob - drivers/char/pty.c

   1 /*
   2  *  linux/drivers/char/pty.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  Added support for a Unix98-style ptmx device.
   7  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
   8  *
   9  *  When reading this code see also fs/devpts. In particular note that the
  10  *  driver_data field is used by the devpts side as a binding to the devpts
  11  *  inode.
  12  */
  13
  14 #include <linux/module.h>
  15
  16 #include <linux/errno.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/tty.h>
  19 #include <linux/tty_flip.h>
  20 #include <linux/fcntl.h>
  21 #include <linux/string.h>
  22 #include <linux/major.h>
  23 #include <linux/mm.h>
  24 #include <linux/init.h>
  25 #include <linux/sysctl.h>
  26 #include <linux/device.h>
  27 #include <linux/uaccess.h>
  28 #include <linux/bitops.h>
  29 #include <linux/devpts_fs.h>
  30
  31 #include <asm/system.h>
  32
  33 /* These are global because they are accessed in tty_io.c */
  34 #ifdef CONFIG_UNIX98_PTYS
  35 struct tty_driver *ptm_driver;
  36 static struct tty_driver *pts_driver;
  37 #endif
  38
  39 static void pty_close(struct tty_struct *tty, struct file *filp)
  40 {
  41         BUG_ON(!tty);
  42         if (tty->driver->subtype == PTY_TYPE_MASTER)
  43                 WARN_ON(tty->count > 1);
  44         else {
  45                 if (tty->count > 2)
  46                         return;
  47         }
  48         wake_up_interruptible(&tty->read_wait);
  49         wake_up_interruptible(&tty->write_wait);
  50         tty->packet = 0;
  51         if (!tty->link)
  52                 return;
  53         tty->link->packet = 0;
  54         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  55         wake_up_interruptible(&tty->link->read_wait);
  56         wake_up_interruptible(&tty->link->write_wait);
  57         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  58                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  59 #ifdef CONFIG_UNIX98_PTYS
  60                 if (tty->driver == ptm_driver)
  61                         devpts_pty_kill(tty->link);
  62 #endif
  63                 tty_vhangup(tty->link);
  64         }
  65 }
  66
  67 /*
  68  * The unthrottle routine is called by the line discipline to signal
  69  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  70  * flag is always set, to force the line discipline to always call the
  71  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  72  * characters in the queue.  This is necessary since each time this
  73  * happens, we need to wake up any sleeping processes that could be
  74  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  75  * for the pty buffer to be drained.
  76  */
  77 static void pty_unthrottle(struct tty_struct *tty)
  78 {
  79         struct tty_struct *o_tty = tty->link;
  80
  81         if (!o_tty)
  82                 return;
  83
  84         tty_wakeup(o_tty);
  85         set_bit(TTY_THROTTLED, &tty->flags);
  86 }
  87
  88 /*
  89  * WSH 05/24/97: modified to
  90  *   (1) use space in tty->flip instead of a shared temp buffer
  91  *       The flip buffers aren't being used for a pty, so there's lots
  92  *       of space available.  The buffer is protected by a per-pty
  93  *       semaphore that should almost never come under contention.
  94  *   (2) avoid redundant copying for cases where count >> receive_room
  95  * N.B. Calls from user space may now return an error code instead of
  96  * a count.
  97  *
  98  * FIXME: Our pty_write method is called with our ldisc lock held but
  99  * not our partners. We can't just take the other one blindly without
 100  * risking deadlocks.
 101  */
 102 static int pty_write(struct tty_struct *tty, const unsigned char *buf,
 103                                                                 int count)
 104 {
 105         struct tty_struct *to = tty->link;
 106         int     c;
 107
 108         if (!to || tty->stopped)
 109                 return 0;
 110
 111         c = to->receive_room;
 112         if (c > count)
 113                 c = count;
 114         to->ldisc.ops->receive_buf(to, buf, NULL, c);
 115
 116         return c;
 117 }
 118
 119 static int pty_write_room(struct tty_struct *tty)
 120 {
 121         struct tty_struct *to = tty->link;
 122
 123         if (!to || tty->stopped)
 124                 return 0;
 125
 126         return to->receive_room;
 127 }
 128
 129 /*
 130  *      WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior
 131  *      The chars_in_buffer() value is used by the ldisc select() function
 132  *      to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
 133  *      The pty driver chars_in_buffer() Master/Slave must behave differently:
 134  *
 135  *      The Master side needs to allow typed-ahead commands to accumulate
 136  *      while being canonicalized, so we report "our buffer" as empty until
 137  *      some threshold is reached, and then report the count. (Any count >
 138  *      WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock
 139  *      the count returned must be 0 if no canonical data is available to be
 140  *      read. (The N_TTY ldisc.chars_in_buffer now knows this.)
 141  *
 142  *      The Slave side passes all characters in raw mode to the Master side's
 143  *      buffer where they can be read immediately, so in this case we can
 144  *      return the true count in the buffer.
 145  */
 146 static int pty_chars_in_buffer(struct tty_struct *tty)
 147 {
 148         struct tty_struct *to = tty->link;
 149         int count;
 150
 151         /* We should get the line discipline lock for "tty->link" */
 152         if (!to || !to->ldisc.ops->chars_in_buffer)
 153                 return 0;
 154
 155         /* The ldisc must report 0 if no characters available to be read */
 156         count = to->ldisc.ops->chars_in_buffer(to);
 157
 158         if (tty->driver->subtype == PTY_TYPE_SLAVE)
 159                 return count;
 160
 161         /* Master side driver ... if the other side's read buffer is less than
 162          * half full, return 0 to allow writers to proceed; otherwise return
 163          * the count.  This leaves a comfortable margin to avoid overflow,
 164          * and still allows half a buffer's worth of typed-ahead commands.
 165          */
 166         return (count < N_TTY_BUF_SIZE/2) ? 0 : count;
 167 }
 168
 169 /* Set the lock flag on a pty */
 170 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 171 {
 172         int val;
 173         if (get_user(val, arg))
 174                 return -EFAULT;
 175         if (val)
 176                 set_bit(TTY_PTY_LOCK, &tty->flags);
 177         else
 178                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 179         return 0;
 180 }
 181
 182 static void pty_flush_buffer(struct tty_struct *tty)
 183 {
 184         struct tty_struct *to = tty->link;
 185         unsigned long flags;
 186
 187         if (!to)
 188                 return;
 189
 190         if (to->ldisc.ops->flush_buffer)
 191                 to->ldisc.ops->flush_buffer(to);
 192
 193         if (to->packet) {
 194                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 195                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 196                 wake_up_interruptible(&to->read_wait);
 197                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 198         }
 199 }
 200
 201 static int pty_open(struct tty_struct *tty, struct file *filp)
 202 {
 203         int     retval = -ENODEV;
 204
 205         if (!tty || !tty->link)
 206                 goto out;
 207
 208         retval = -EIO;
 209         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 210                 goto out;
 211         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 212                 goto out;
 213         if (tty->link->count != 1)
 214                 goto out;
 215
 216         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 217         set_bit(TTY_THROTTLED, &tty->flags);
 218         retval = 0;
 219 out:
 220         return retval;
 221 }
 222
 223 static void pty_set_termios(struct tty_struct *tty,
 224                                         struct ktermios *old_termios)
 225 {
 226         tty->termios->c_cflag &= ~(CSIZE | PARENB);
 227         tty->termios->c_cflag |= (CS8 | CREAD);
 228 }
 229
 230 /**
 231  *      pty_do_resize           -       resize event
 232  *      @tty: tty being resized
 233  *      @real_tty: real tty (not the same as tty if using a pty/tty pair)
 234  *      @rows: rows (character)
 235  *      @cols: cols (character)
 236  *
 237  *      Update the termios variables and send the neccessary signals to
 238  *      peform a terminal resize correctly
 239  */
 240
 241 int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 242 {
 243         struct pid *pgrp, *rpgrp;
 244         unsigned long flags;
 245         struct tty_struct *pty = tty->link;
 246
 247         /* For a PTY we need to lock the tty side */
 248         mutex_lock(&tty->termios_mutex);
 249         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 250                 goto done;
 251
 252         /* Get the PID values and reference them so we can
 253            avoid holding the tty ctrl lock while sending signals.
 254            We need to lock these individually however. */
 255
 256         spin_lock_irqsave(&tty->ctrl_lock, flags);
 257         pgrp = get_pid(tty->pgrp);
 258         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 259
 260         spin_lock_irqsave(&pty->ctrl_lock, flags);
 261         rpgrp = get_pid(pty->pgrp);
 262         spin_unlock_irqrestore(&pty->ctrl_lock, flags);
 263
 264         if (pgrp)
 265                 kill_pgrp(pgrp, SIGWINCH, 1);
 266         if (rpgrp != pgrp && rpgrp)
 267                 kill_pgrp(rpgrp, SIGWINCH, 1);
 268
 269         put_pid(pgrp);
 270         put_pid(rpgrp);
 271
 272         tty->winsize = *ws;
 273         pty->winsize = *ws;     /* Never used so will go away soon */
 274 done:
 275         mutex_unlock(&tty->termios_mutex);
 276         return 0;
 277 }
 278
 279 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 280 {
 281         struct tty_struct *o_tty;
 282         int idx = tty->index;
 283         int retval;
 284
 285         o_tty = alloc_tty_struct();
 286         if (!o_tty)
 287                 return -ENOMEM;
 288         if (!try_module_get(driver->other->owner)) {
 289                 /* This cannot in fact currently happen */
 290                 free_tty_struct(o_tty);
 291                 return -ENOMEM;
 292         }
 293         initialize_tty_struct(o_tty, driver->other, idx);
 294
 295         /* We always use new tty termios data so we can do this
 296            the easy way .. */
 297         retval = tty_init_termios(tty);
 298         if (retval)
 299                 goto free_mem_out;
 300
 301         retval = tty_init_termios(o_tty);
 302         if (retval) {
 303                 tty_free_termios(tty);
 304                 goto free_mem_out;
 305         }
 306
 307         /*
 308          * Everything allocated ... set up the o_tty structure.
 309          */
 310         driver->other->ttys[idx] = o_tty;
 311         tty_driver_kref_get(driver->other);
 312         if (driver->subtype == PTY_TYPE_MASTER)
 313                 o_tty->count++;
 314         /* Establish the links in both directions */
 315         tty->link   = o_tty;
 316         o_tty->link = tty;
 317
 318         tty_driver_kref_get(driver);
 319         tty->count++;
 320         driver->ttys[idx] = tty;
 321         return 0;
 322 free_mem_out:
 323         module_put(o_tty->driver->owner);
 324         free_tty_struct(o_tty);
 325         return -ENOMEM;
 326 }
 327
 328
 329 static const struct tty_operations pty_ops = {
 330         .install = pty_install,
 331         .open = pty_open,
 332         .close = pty_close,
 333         .write = pty_write,
 334         .write_room = pty_write_room,
 335         .flush_buffer = pty_flush_buffer,
 336         .chars_in_buffer = pty_chars_in_buffer,
 337         .unthrottle = pty_unthrottle,
 338         .set_termios = pty_set_termios,
 339         .resize = pty_resize
 340 };
 341
 342 /* Traditional BSD devices */
 343 #ifdef CONFIG_LEGACY_PTYS
 344 static struct tty_driver *pty_driver, *pty_slave_driver;
 345
 346 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
 347                          unsigned int cmd, unsigned long arg)
 348 {
 349         switch (cmd) {
 350         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 351                 return pty_set_lock(tty, (int __user *) arg);
 352         }
 353         return -ENOIOCTLCMD;
 354 }
 355
 356 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 357 module_param(legacy_count, int, 0);
 358
 359 static const struct tty_operations pty_ops_bsd = {
 360         .open = pty_open,
 361         .close = pty_close,
 362         .write = pty_write,
 363         .write_room = pty_write_room,
 364         .flush_buffer = pty_flush_buffer,
 365         .chars_in_buffer = pty_chars_in_buffer,
 366         .unthrottle = pty_unthrottle,
 367         .set_termios = pty_set_termios,
 368         .ioctl = pty_bsd_ioctl,
 369         .resize = pty_resize
 370 };
 371
 372 static void __init legacy_pty_init(void)
 373 {
 374         if (legacy_count <= 0)
 375                 return;
 376
 377         pty_driver = alloc_tty_driver(legacy_count);
 378         if (!pty_driver)
 379                 panic("Couldn't allocate pty driver");
 380
 381         pty_slave_driver = alloc_tty_driver(legacy_count);
 382         if (!pty_slave_driver)
 383                 panic("Couldn't allocate pty slave driver");
 384
 385         pty_driver->owner = THIS_MODULE;
 386         pty_driver->driver_name = "pty_master";
 387         pty_driver->name = "pty";
 388         pty_driver->major = PTY_MASTER_MAJOR;
 389         pty_driver->minor_start = 0;
 390         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 391         pty_driver->subtype = PTY_TYPE_MASTER;
 392         pty_driver->init_termios = tty_std_termios;
 393         pty_driver->init_termios.c_iflag = 0;
 394         pty_driver->init_termios.c_oflag = 0;
 395         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 396         pty_driver->init_termios.c_lflag = 0;
 397         pty_driver->init_termios.c_ispeed = 38400;
 398         pty_driver->init_termios.c_ospeed = 38400;
 399         pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
 400         pty_driver->other = pty_slave_driver;
 401         tty_set_operations(pty_driver, &pty_ops);
 402
 403         pty_slave_driver->owner = THIS_MODULE;
 404         pty_slave_driver->driver_name = "pty_slave";
 405         pty_slave_driver->name = "ttyp";
 406         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 407         pty_slave_driver->minor_start = 0;
 408         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 409         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 410         pty_slave_driver->init_termios = tty_std_termios;
 411         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 412         pty_slave_driver->init_termios.c_ispeed = 38400;
 413         pty_slave_driver->init_termios.c_ospeed = 38400;
 414         pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
 415                                         TTY_DRIVER_REAL_RAW;
 416         pty_slave_driver->other = pty_driver;
 417         tty_set_operations(pty_slave_driver, &pty_ops);
 418
 419         if (tty_register_driver(pty_driver))
 420                 panic("Couldn't register pty driver");
 421         if (tty_register_driver(pty_slave_driver))
 422                 panic("Couldn't register pty slave driver");
 423 }
 424 #else
 425 static inline void legacy_pty_init(void) { }
 426 #endif
 427
 428 /* Unix98 devices */
 429 #ifdef CONFIG_UNIX98_PTYS
 430 /*
 431  * sysctl support for setting limits on the number of Unix98 ptys allocated.
 432  * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
 433  */
 434 int pty_limit = NR_UNIX98_PTY_DEFAULT;
 435 static int pty_limit_min;
 436 static int pty_limit_max = NR_UNIX98_PTY_MAX;
 437 static int pty_count;
 438
 439 static struct cdev ptmx_cdev;
 440
 441 static struct ctl_table pty_table[] = {
 442         {
 443                 .ctl_name       = PTY_MAX,
 444                 .procname       = "max",
 445                 .maxlen         = sizeof(int),
 446                 .mode           = 0644,
 447                 .data           = &pty_limit,
 448                 .proc_handler   = &proc_dointvec_minmax,
 449                 .strategy       = &sysctl_intvec,
 450                 .extra1         = &pty_limit_min,
 451                 .extra2         = &pty_limit_max,
 452         }, {
 453                 .ctl_name       = PTY_NR,
 454                 .procname       = "nr",
 455                 .maxlen         = sizeof(int),
 456                 .mode           = 0444,
 457                 .data           = &pty_count,
 458                 .proc_handler   = &proc_dointvec,
 459         }, {
 460                 .ctl_name       = 0
 461         }
 462 };
 463
 464 static struct ctl_table pty_kern_table[] = {
 465         {
 466                 .ctl_name       = KERN_PTY,
 467                 .procname       = "pty",
 468                 .mode           = 0555,
 469                 .child          = pty_table,
 470         },
 471         {}
 472 };
 473
 474 static struct ctl_table pty_root_table[] = {
 475         {
 476                 .ctl_name       = CTL_KERN,
 477                 .procname       = "kernel",
 478                 .mode           = 0555,
 479                 .child          = pty_kern_table,
 480         },
 481         {}
 482 };
 483
 484
 485 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
 486                             unsigned int cmd, unsigned long arg)
 487 {
 488         switch (cmd) {
 489         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 490                 return pty_set_lock(tty, (int __user *)arg);
 491         case TIOCGPTN: /* Get PT Number */
 492                 return put_user(tty->index, (unsigned int __user *)arg);
 493         }
 494
 495         return -ENOIOCTLCMD;
 496 }
 497
 498 /**
 499  *      ptm_unix98_lookup       -       find a pty master
 500  *      @driver: ptm driver
 501  *      @idx: tty index
 502  *
 503  *      Look up a pty master device. Called under the tty_mutex for now.
 504  *      This provides our locking.
 505  */
 506
 507 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 508                 struct inode *ptm_inode, int idx)
 509 {
 510         struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
 511         if (tty)
 512                 tty = tty->link;
 513         return tty;
 514 }
 515
 516 /**
 517  *      pts_unix98_lookup       -       find a pty slave
 518  *      @driver: pts driver
 519  *      @idx: tty index
 520  *
 521  *      Look up a pty master device. Called under the tty_mutex for now.
 522  *      This provides our locking.
 523  */
 524
 525 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 526                 struct inode *pts_inode, int idx)
 527 {
 528         struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
 529         /* Master must be open before slave */
 530         if (!tty)
 531                 return ERR_PTR(-EIO);
 532         return tty;
 533 }
 534
 535 static void pty_unix98_shutdown(struct tty_struct *tty)
 536 {
 537         /* We have our own method as we don't use the tty index */
 538         kfree(tty->termios);
 539 }
 540
 541 /* We have no need to install and remove our tty objects as devpts does all
 542    the work for us */
 543
 544 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 545 {
 546         struct tty_struct *o_tty;
 547         int idx = tty->index;
 548
 549         o_tty = alloc_tty_struct();
 550         if (!o_tty)
 551                 return -ENOMEM;
 552         if (!try_module_get(driver->other->owner)) {
 553                 /* This cannot in fact currently happen */
 554                 free_tty_struct(o_tty);
 555                 return -ENOMEM;
 556         }
 557         initialize_tty_struct(o_tty, driver->other, idx);
 558
 559         tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
 560         if (tty->termios == NULL)
 561                 goto free_mem_out;
 562         *tty->termios = driver->init_termios;
 563         tty->termios_locked = tty->termios + 1;
 564
 565         o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
 566         if (o_tty->termios == NULL)
 567                 goto free_mem_out;
 568         *o_tty->termios = driver->other->init_termios;
 569         o_tty->termios_locked = o_tty->termios + 1;
 570
 571         tty_driver_kref_get(driver->other);
 572         if (driver->subtype == PTY_TYPE_MASTER)
 573                 o_tty->count++;
 574         /* Establish the links in both directions */
 575         tty->link   = o_tty;
 576         o_tty->link = tty;
 577         /*
 578          * All structures have been allocated, so now we install them.
 579          * Failures after this point use release_tty to clean up, so
 580          * there's no need to null out the local pointers.
 581          */
 582         tty_driver_kref_get(driver);
 583         tty->count++;
 584         pty_count++;
 585         return 0;
 586 free_mem_out:
 587         kfree(o_tty->termios);
 588         module_put(o_tty->driver->owner);
 589         free_tty_struct(o_tty);
 590         kfree(tty->termios);
 591         return -ENOMEM;
 592 }
 593
 594 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 595 {
 596         pty_count--;
 597 }
 598
 599 static const struct tty_operations ptm_unix98_ops = {
 600         .lookup = ptm_unix98_lookup,
 601         .install = pty_unix98_install,
 602         .remove = pty_unix98_remove,
 603         .open = pty_open,
 604         .close = pty_close,
 605         .write = pty_write,
 606         .write_room = pty_write_room,
 607         .flush_buffer = pty_flush_buffer,
 608         .chars_in_buffer = pty_chars_in_buffer,
 609         .unthrottle = pty_unthrottle,
 610         .set_termios = pty_set_termios,
 611         .ioctl = pty_unix98_ioctl,
 612         .shutdown = pty_unix98_shutdown,
 613         .resize = pty_resize
 614 };
 615
 616 static const struct tty_operations pty_unix98_ops = {
 617         .lookup = pts_unix98_lookup,
 618         .install = pty_unix98_install,
 619         .remove = pty_unix98_remove,
 620         .open = pty_open,
 621         .close = pty_close,
 622         .write = pty_write,
 623         .write_room = pty_write_room,
 624         .flush_buffer = pty_flush_buffer,
 625         .chars_in_buffer = pty_chars_in_buffer,
 626         .unthrottle = pty_unthrottle,
 627         .set_termios = pty_set_termios,
 628         .shutdown = pty_unix98_shutdown
 629 };
 630
 631 /**
 632  *      ptmx_open               -       open a unix 98 pty master
 633  *      @inode: inode of device file
 634  *      @filp: file pointer to tty
 635  *
 636  *      Allocate a unix98 pty master device from the ptmx driver.
 637  *
 638  *      Locking: tty_mutex protects the init_dev work. tty->count should
 639  *              protect the rest.
 640  *              allocated_ptys_lock handles the list of free pty numbers
 641  */
 642
 643 static int __ptmx_open(struct inode *inode, struct file *filp)
 644 {
 645         struct tty_struct *tty;
 646         int retval;
 647         int index;
 648
 649         nonseekable_open(inode, filp);
 650
 651         /* find a device that is not in use. */
 652         index = devpts_new_index(inode);
 653         if (index < 0)
 654                 return index;
 655
 656         mutex_lock(&tty_mutex);
 657         tty = tty_init_dev(ptm_driver, index, 1);
 658         mutex_unlock(&tty_mutex);
 659
 660         if (IS_ERR(tty)) {
 661                 retval = PTR_ERR(tty);
 662                 goto out;
 663         }
 664
 665         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 666         filp->private_data = tty;
 667         file_move(filp, &tty->tty_files);
 668
 669         retval = devpts_pty_new(inode, tty->link);
 670         if (retval)
 671                 goto out1;
 672
 673         retval = ptm_driver->ops->open(tty, filp);
 674         if (!retval)
 675                 return 0;
 676 out1:
 677         tty_release_dev(filp);
 678         return retval;
 679 out:
 680         devpts_kill_index(inode, index);
 681         return retval;
 682 }
 683
 684 static int ptmx_open(struct inode *inode, struct file *filp)
 685 {
 686         int ret;
 687
 688         lock_kernel();
 689         ret = __ptmx_open(inode, filp);
 690         unlock_kernel();
 691         return ret;
 692 }
 693
 694 static struct file_operations ptmx_fops;
 695
 696 static void __init unix98_pty_init(void)
 697 {
 698         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 699         if (!ptm_driver)
 700                 panic("Couldn't allocate Unix98 ptm driver");
 701         pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 702         if (!pts_driver)
 703                 panic("Couldn't allocate Unix98 pts driver");
 704
 705         ptm_driver->owner = THIS_MODULE;
 706         ptm_driver->driver_name = "pty_master";
 707         ptm_driver->name = "ptm";
 708         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 709         ptm_driver->minor_start = 0;
 710         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 711         ptm_driver->subtype = PTY_TYPE_MASTER;
 712         ptm_driver->init_termios = tty_std_termios;
 713         ptm_driver->init_termios.c_iflag = 0;
 714         ptm_driver->init_termios.c_oflag = 0;
 715         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 716         ptm_driver->init_termios.c_lflag = 0;
 717         ptm_driver->init_termios.c_ispeed = 38400;
 718         ptm_driver->init_termios.c_ospeed = 38400;
 719         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 720                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 721         ptm_driver->other = pts_driver;
 722         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 723
 724         pts_driver->owner = THIS_MODULE;
 725         pts_driver->driver_name = "pty_slave";
 726         pts_driver->name = "pts";
 727         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 728         pts_driver->minor_start = 0;
 729         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 730         pts_driver->subtype = PTY_TYPE_SLAVE;
 731         pts_driver->init_termios = tty_std_termios;
 732         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 733         pts_driver->init_termios.c_ispeed = 38400;
 734         pts_driver->init_termios.c_ospeed = 38400;
 735         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 736                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 737         pts_driver->other = ptm_driver;
 738         tty_set_operations(pts_driver, &pty_unix98_ops);
 739
 740         if (tty_register_driver(ptm_driver))
 741                 panic("Couldn't register Unix98 ptm driver");
 742         if (tty_register_driver(pts_driver))
 743                 panic("Couldn't register Unix98 pts driver");
 744
 745         register_sysctl_table(pty_root_table);
 746
 747         /* Now create the /dev/ptmx special device */
 748         tty_default_fops(&ptmx_fops);
 749         ptmx_fops.open = ptmx_open;
 750
 751         cdev_init(&ptmx_cdev, &ptmx_fops);
 752         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 753             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 754                 panic("Couldn't register /dev/ptmx driver\n");
 755         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 756 }
 757
 758 #else
 759 static inline void unix98_pty_init(void) { }
 760 #endif
 761
 762 static int __init pty_init(void)
 763 {
 764         legacy_pty_init();
 765         unix98_pty_init();
 766         return 0;
 767 }
 768 module_init(pty_init);