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