drivers/tty/pty.c

   1 /*
   2  *  Copyright (C) 1991, 1992  Linus Torvalds
   3  *
   4  *  Added support for a Unix98-style ptmx device.
   5  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
   6  *
   7  *  When reading this code see also fs/devpts. In particular note that the
   8  *  driver_data field is used by the devpts side as a binding to the devpts
   9  *  inode.
  10  */
  11
  12 #include <linux/module.h>
  13
  14 #include <linux/errno.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/tty.h>
  17 #include <linux/tty_flip.h>
  18 #include <linux/fcntl.h>
  19 #include <linux/sched.h>
  20 #include <linux/string.h>
  21 #include <linux/major.h>
  22 #include <linux/mm.h>
  23 #include <linux/init.h>
  24 #include <linux/sysctl.h>
  25 #include <linux/device.h>
  26 #include <linux/uaccess.h>
  27 #include <linux/bitops.h>
  28 #include <linux/devpts_fs.h>
  29 #include <linux/slab.h>
  30
  31 #include <asm/system.h>
  32
  33 #ifdef CONFIG_UNIX98_PTYS
  34 static struct tty_driver *ptm_driver;
  35 static struct tty_driver *pts_driver;
  36 #endif
  37
  38 static void pty_close(struct tty_struct *tty, struct file *filp)
  39 {
  40         BUG_ON(!tty);
  41         if (tty->driver->subtype == PTY_TYPE_MASTER)
  42                 WARN_ON(tty->count > 1);
  43         else {
  44                 if (tty->count > 2)
  45                         return;
  46         }
  47         wake_up_interruptible(&tty->read_wait);
  48         wake_up_interruptible(&tty->write_wait);
  49         tty->packet = 0;
  50         if (!tty->link)
  51                 return;
  52         tty->link->packet = 0;
  53         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  54         wake_up_interruptible(&tty->link->read_wait);
  55         wake_up_interruptible(&tty->link->write_wait);
  56         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  57                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  58 #ifdef CONFIG_UNIX98_PTYS
  59                 if (tty->driver == ptm_driver)
  60                         devpts_pty_kill(tty->link);
  61 #endif
  62                 tty_unlock();
  63                 tty_vhangup(tty->link);
  64                 tty_lock();
  65         }
  66 }
  67
  68 /*
  69  * The unthrottle routine is called by the line discipline to signal
  70  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  71  * flag is always set, to force the line discipline to always call the
  72  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  73  * characters in the queue.  This is necessary since each time this
  74  * happens, we need to wake up any sleeping processes that could be
  75  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  76  * for the pty buffer to be drained.
  77  */
  78 static void pty_unthrottle(struct tty_struct *tty)
  79 {
  80         tty_wakeup(tty->link);
  81         set_bit(TTY_THROTTLED, &tty->flags);
  82 }
  83
  84 /**
  85  *      pty_space       -       report space left for writing
  86  *      @to: tty we are writing into
  87  *
  88  *      The tty buffers allow 64K but we sneak a peak and clip at 8K this
  89  *      allows a lot of overspill room for echo and other fun messes to
  90  *      be handled properly
  91  */
  92
  93 static int pty_space(struct tty_struct *to)
  94 {
  95         int n = 8192 - to->buf.memory_used;
  96         if (n < 0)
  97                 return 0;
  98         return n;
  99 }
 100
 101 /**
 102  *      pty_write               -       write to a pty
 103  *      @tty: the tty we write from
 104  *      @buf: kernel buffer of data
 105  *      @count: bytes to write
 106  *
 107  *      Our "hardware" write method. Data is coming from the ldisc which
 108  *      may be in a non sleeping state. We simply throw this at the other
 109  *      end of the link as if we were an IRQ handler receiving stuff for
 110  *      the other side of the pty/tty pair.
 111  */
 112
 113 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 114 {
 115         struct tty_struct *to = tty->link;
 116
 117         if (tty->stopped)
 118                 return 0;
 119
 120         if (c > 0) {
 121                 /* Stuff the data into the input queue of the other end */
 122                 c = tty_insert_flip_string(to, buf, c);
 123                 /* And shovel */
 124                 if (c) {
 125                         tty_flip_buffer_push(to);
 126                         tty_wakeup(tty);
 127                 }
 128         }
 129         return c;
 130 }
 131
 132 /**
 133  *      pty_write_room  -       write space
 134  *      @tty: tty we are writing from
 135  *
 136  *      Report how many bytes the ldisc can send into the queue for
 137  *      the other device.
 138  */
 139
 140 static int pty_write_room(struct tty_struct *tty)
 141 {
 142         if (tty->stopped)
 143                 return 0;
 144         return pty_space(tty->link);
 145 }
 146
 147 /**
 148  *      pty_chars_in_buffer     -       characters currently in our tx queue
 149  *      @tty: our tty
 150  *
 151  *      Report how much we have in the transmit queue. As everything is
 152  *      instantly at the other end this is easy to implement.
 153  */
 154
 155 static int pty_chars_in_buffer(struct tty_struct *tty)
 156 {
 157         return 0;
 158 }
 159
 160 /* Set the lock flag on a pty */
 161 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 162 {
 163         int val;
 164         if (get_user(val, arg))
 165                 return -EFAULT;
 166         if (val)
 167                 set_bit(TTY_PTY_LOCK, &tty->flags);
 168         else
 169                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 170         return 0;
 171 }
 172
 173 /* Send a signal to the slave */
 174 static int pty_signal(struct tty_struct *tty, int sig)
 175 {
 176         unsigned long flags;
 177         struct pid *pgrp;
 178
 179         if (tty->link) {
 180                 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
 181                 pgrp = get_pid(tty->link->pgrp);
 182                 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
 183
 184                 kill_pgrp(pgrp, sig, 1);
 185                 put_pid(pgrp);
 186         }
 187         return 0;
 188 }
 189
 190 static void pty_flush_buffer(struct tty_struct *tty)
 191 {
 192         struct tty_struct *to = tty->link;
 193         unsigned long flags;
 194
 195         if (!to)
 196                 return;
 197         /* tty_buffer_flush(to); FIXME */
 198         if (to->packet) {
 199                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 200                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 201                 wake_up_interruptible(&to->read_wait);
 202                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 203         }
 204 }
 205
 206 static int pty_open(struct tty_struct *tty, struct file *filp)
 207 {
 208         int     retval = -ENODEV;
 209
 210         if (!tty || !tty->link)
 211                 goto out;
 212
 213         retval = -EIO;
 214         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 215                 goto out;
 216         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 217                 goto out;
 218         if (tty->link->count != 1)
 219                 goto out;
 220
 221         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 222         set_bit(TTY_THROTTLED, &tty->flags);
 223         retval = 0;
 224 out:
 225         return retval;
 226 }
 227
 228 static void pty_set_termios(struct tty_struct *tty,
 229                                         struct ktermios *old_termios)
 230 {
 231         tty->termios->c_cflag &= ~(CSIZE | PARENB);
 232         tty->termios->c_cflag |= (CS8 | CREAD);
 233 }
 234
 235 /**
 236  *      pty_do_resize           -       resize event
 237  *      @tty: tty being resized
 238  *      @ws: window size being set.
 239  *
 240  *      Update the termios variables and send the necessary signals to
 241  *      peform a terminal resize correctly
 242  */
 243
 244 int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 245 {
 246         struct pid *pgrp, *rpgrp;
 247         unsigned long flags;
 248         struct tty_struct *pty = tty->link;
 249
 250         /* For a PTY we need to lock the tty side */
 251         mutex_lock(&tty->termios_mutex);
 252         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 253                 goto done;
 254
 255         /* Get the PID values and reference them so we can
 256            avoid holding the tty ctrl lock while sending signals.
 257            We need to lock these individually however. */
 258
 259         spin_lock_irqsave(&tty->ctrl_lock, flags);
 260         pgrp = get_pid(tty->pgrp);
 261         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 262
 263         spin_lock_irqsave(&pty->ctrl_lock, flags);
 264         rpgrp = get_pid(pty->pgrp);
 265         spin_unlock_irqrestore(&pty->ctrl_lock, flags);
 266
 267         if (pgrp)
 268                 kill_pgrp(pgrp, SIGWINCH, 1);
 269         if (rpgrp != pgrp && rpgrp)
 270                 kill_pgrp(rpgrp, SIGWINCH, 1);
 271
 272         put_pid(pgrp);
 273         put_pid(rpgrp);
 274
 275         tty->winsize = *ws;
 276         pty->winsize = *ws;     /* Never used so will go away soon */
 277 done:
 278         mutex_unlock(&tty->termios_mutex);
 279         return 0;
 280 }
 281
 282 /* Traditional BSD devices */
 283 #ifdef CONFIG_LEGACY_PTYS
 284
 285 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 286 {
 287         struct tty_struct *o_tty;
 288         int idx = tty->index;
 289         int retval;
 290
 291         o_tty = alloc_tty_struct();
 292         if (!o_tty)
 293                 return -ENOMEM;
 294         if (!try_module_get(driver->other->owner)) {
 295                 /* This cannot in fact currently happen */
 296                 retval = -ENOMEM;
 297                 goto err_free_tty;
 298         }
 299         initialize_tty_struct(o_tty, driver->other, idx);
 300
 301         /* We always use new tty termios data so we can do this
 302            the easy way .. */
 303         retval = tty_init_termios(tty);
 304         if (retval)
 305                 goto err_deinit_tty;
 306
 307         retval = tty_init_termios(o_tty);
 308         if (retval)
 309                 goto err_free_termios;
 310
 311         /*
 312          * Everything allocated ... set up the o_tty structure.
 313          */
 314         driver->other->ttys[idx] = o_tty;
 315         tty_driver_kref_get(driver->other);
 316         if (driver->subtype == PTY_TYPE_MASTER)
 317                 o_tty->count++;
 318         /* Establish the links in both directions */
 319         tty->link   = o_tty;
 320         o_tty->link = tty;
 321
 322         tty_driver_kref_get(driver);
 323         tty->count++;
 324         driver->ttys[idx] = tty;
 325         return 0;
 326 err_free_termios:
 327         tty_free_termios(tty);
 328 err_deinit_tty:
 329         deinitialize_tty_struct(o_tty);
 330         module_put(o_tty->driver->owner);
 331 err_free_tty:
 332         free_tty_struct(o_tty);
 333         return retval;
 334 }
 335
 336 static int pty_bsd_ioctl(struct tty_struct *tty,
 337                          unsigned int cmd, unsigned long arg)
 338 {
 339         switch (cmd) {
 340         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 341                 return pty_set_lock(tty, (int __user *) arg);
 342         case TIOCSIG:    /* Send signal to other side of pty */
 343                 return pty_signal(tty, (int) arg);
 344         }
 345         return -ENOIOCTLCMD;
 346 }
 347
 348 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 349 module_param(legacy_count, int, 0);
 350
 351 /*
 352  * The master side of a pty can do TIOCSPTLCK and thus
 353  * has pty_bsd_ioctl.
 354  */
 355 static const struct tty_operations master_pty_ops_bsd = {
 356         .install = pty_install,
 357         .open = pty_open,
 358         .close = pty_close,
 359         .write = pty_write,
 360         .write_room = pty_write_room,
 361         .flush_buffer = pty_flush_buffer,
 362         .chars_in_buffer = pty_chars_in_buffer,
 363         .unthrottle = pty_unthrottle,
 364         .set_termios = pty_set_termios,
 365         .ioctl = pty_bsd_ioctl,
 366         .resize = pty_resize
 367 };
 368
 369 static const struct tty_operations slave_pty_ops_bsd = {
 370         .install = pty_install,
 371         .open = pty_open,
 372         .close = pty_close,
 373         .write = pty_write,
 374         .write_room = pty_write_room,
 375         .flush_buffer = pty_flush_buffer,
 376         .chars_in_buffer = pty_chars_in_buffer,
 377         .unthrottle = pty_unthrottle,
 378         .set_termios = pty_set_termios,
 379         .resize = pty_resize
 380 };
 381
 382 static void __init legacy_pty_init(void)
 383 {
 384         struct tty_driver *pty_driver, *pty_slave_driver;
 385
 386         if (legacy_count <= 0)
 387                 return;
 388
 389         pty_driver = alloc_tty_driver(legacy_count);
 390         if (!pty_driver)
 391                 panic("Couldn't allocate pty driver");
 392
 393         pty_slave_driver = alloc_tty_driver(legacy_count);
 394         if (!pty_slave_driver)
 395                 panic("Couldn't allocate pty slave driver");
 396
 397         pty_driver->owner = THIS_MODULE;
 398         pty_driver->driver_name = "pty_master";
 399         pty_driver->name = "pty";
 400         pty_driver->major = PTY_MASTER_MAJOR;
 401         pty_driver->minor_start = 0;
 402         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 403         pty_driver->subtype = PTY_TYPE_MASTER;
 404         pty_driver->init_termios = tty_std_termios;
 405         pty_driver->init_termios.c_iflag = 0;
 406         pty_driver->init_termios.c_oflag = 0;
 407         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 408         pty_driver->init_termios.c_lflag = 0;
 409         pty_driver->init_termios.c_ispeed = 38400;
 410         pty_driver->init_termios.c_ospeed = 38400;
 411         pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
 412         pty_driver->other = pty_slave_driver;
 413         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 414
 415         pty_slave_driver->owner = THIS_MODULE;
 416         pty_slave_driver->driver_name = "pty_slave";
 417         pty_slave_driver->name = "ttyp";
 418         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 419         pty_slave_driver->minor_start = 0;
 420         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 421         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 422         pty_slave_driver->init_termios = tty_std_termios;
 423         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 424         pty_slave_driver->init_termios.c_ispeed = 38400;
 425         pty_slave_driver->init_termios.c_ospeed = 38400;
 426         pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
 427                                         TTY_DRIVER_REAL_RAW;
 428         pty_slave_driver->other = pty_driver;
 429         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 430
 431         if (tty_register_driver(pty_driver))
 432                 panic("Couldn't register pty driver");
 433         if (tty_register_driver(pty_slave_driver))
 434                 panic("Couldn't register pty slave driver");
 435 }
 436 #else
 437 static inline void legacy_pty_init(void) { }
 438 #endif
 439
 440 /* Unix98 devices */
 441 #ifdef CONFIG_UNIX98_PTYS
 442 /*
 443  * sysctl support for setting limits on the number of Unix98 ptys allocated.
 444  * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
 445  */
 446 int pty_limit = NR_UNIX98_PTY_DEFAULT;
 447 static int pty_limit_min;
 448 static int pty_limit_max = NR_UNIX98_PTY_MAX;
 449 static int tty_count;
 450 static int pty_count;
 451
 452 static inline void pty_inc_count(void)
 453 {
 454         pty_count = (++tty_count) / 2;
 455 }
 456
 457 static inline void pty_dec_count(void)
 458 {
 459         pty_count = (--tty_count) / 2;
 460 }
 461
 462 static struct cdev ptmx_cdev;
 463
 464 static struct ctl_table pty_table[] = {
 465         {
 466                 .procname       = "max",
 467                 .maxlen         = sizeof(int),
 468                 .mode           = 0644,
 469                 .data           = &pty_limit,
 470                 .proc_handler   = proc_dointvec_minmax,
 471                 .extra1         = &pty_limit_min,
 472                 .extra2         = &pty_limit_max,
 473         }, {
 474                 .procname       = "nr",
 475                 .maxlen         = sizeof(int),
 476                 .mode           = 0444,
 477                 .data           = &pty_count,
 478                 .proc_handler   = proc_dointvec,
 479         },
 480         {}
 481 };
 482
 483 static struct ctl_table pty_kern_table[] = {
 484         {
 485                 .procname       = "pty",
 486                 .mode           = 0555,
 487                 .child          = pty_table,
 488         },
 489         {}
 490 };
 491
 492 static struct ctl_table pty_root_table[] = {
 493         {
 494                 .procname       = "kernel",
 495                 .mode           = 0555,
 496                 .child          = pty_kern_table,
 497         },
 498         {}
 499 };
 500
 501
 502 static int pty_unix98_ioctl(struct tty_struct *tty,
 503                             unsigned int cmd, unsigned long arg)
 504 {
 505         switch (cmd) {
 506         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 507                 return pty_set_lock(tty, (int __user *)arg);
 508         case TIOCGPTN: /* Get PT Number */
 509                 return put_user(tty->index, (unsigned int __user *)arg);
 510         case TIOCSIG:    /* Send signal to other side of pty */
 511                 return pty_signal(tty, (int) arg);
 512         }
 513
 514         return -ENOIOCTLCMD;
 515 }
 516
 517 /**
 518  *      ptm_unix98_lookup       -       find a pty master
 519  *      @driver: ptm driver
 520  *      @idx: tty index
 521  *
 522  *      Look up a pty master device. Called under the tty_mutex for now.
 523  *      This provides our locking.
 524  */
 525
 526 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 527                 struct inode *ptm_inode, int idx)
 528 {
 529         struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
 530         if (tty)
 531                 tty = tty->link;
 532         return tty;
 533 }
 534
 535 /**
 536  *      pts_unix98_lookup       -       find a pty slave
 537  *      @driver: pts driver
 538  *      @idx: tty index
 539  *
 540  *      Look up a pty master device. Called under the tty_mutex for now.
 541  *      This provides our locking.
 542  */
 543
 544 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 545                 struct inode *pts_inode, int idx)
 546 {
 547         struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
 548         /* Master must be open before slave */
 549         if (!tty)
 550                 return ERR_PTR(-EIO);
 551         return tty;
 552 }
 553
 554 static void pty_unix98_shutdown(struct tty_struct *tty)
 555 {
 556         tty_driver_remove_tty(tty->driver, tty);
 557         /* We have our own method as we don't use the tty index */
 558         kfree(tty->termios);
 559 }
 560
 561 /* We have no need to install and remove our tty objects as devpts does all
 562    the work for us */
 563
 564 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 565 {
 566         struct tty_struct *o_tty;
 567         int idx = tty->index;
 568
 569         o_tty = alloc_tty_struct();
 570         if (!o_tty)
 571                 return -ENOMEM;
 572         if (!try_module_get(driver->other->owner)) {
 573                 /* This cannot in fact currently happen */
 574                 goto err_free_tty;
 575         }
 576         initialize_tty_struct(o_tty, driver->other, idx);
 577
 578         tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
 579         if (tty->termios == NULL)
 580                 goto err_free_mem;
 581         *tty->termios = driver->init_termios;
 582         tty->termios_locked = tty->termios + 1;
 583
 584         o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
 585         if (o_tty->termios == NULL)
 586                 goto err_free_mem;
 587         *o_tty->termios = driver->other->init_termios;
 588         o_tty->termios_locked = o_tty->termios + 1;
 589
 590         tty_driver_kref_get(driver->other);
 591         if (driver->subtype == PTY_TYPE_MASTER)
 592                 o_tty->count++;
 593         /* Establish the links in both directions */
 594         tty->link   = o_tty;
 595         o_tty->link = tty;
 596         /*
 597          * All structures have been allocated, so now we install them.
 598          * Failures after this point use release_tty to clean up, so
 599          * there's no need to null out the local pointers.
 600          */
 601         tty_driver_kref_get(driver);
 602         tty->count++;
 603         pty_inc_count(); /* tty */
 604         pty_inc_count(); /* tty->link */
 605         return 0;
 606 err_free_mem:
 607         deinitialize_tty_struct(o_tty);
 608         kfree(o_tty->termios);
 609         kfree(tty->termios);
 610         module_put(o_tty->driver->owner);
 611 err_free_tty:
 612         free_tty_struct(o_tty);
 613         return -ENOMEM;
 614 }
 615
 616 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 617 {
 618         pty_dec_count();
 619 }
 620
 621 static const struct tty_operations ptm_unix98_ops = {
 622         .lookup = ptm_unix98_lookup,
 623         .install = pty_unix98_install,
 624         .remove = pty_unix98_remove,
 625         .open = pty_open,
 626         .close = pty_close,
 627         .write = pty_write,
 628         .write_room = pty_write_room,
 629         .flush_buffer = pty_flush_buffer,
 630         .chars_in_buffer = pty_chars_in_buffer,
 631         .unthrottle = pty_unthrottle,
 632         .set_termios = pty_set_termios,
 633         .ioctl = pty_unix98_ioctl,
 634         .shutdown = pty_unix98_shutdown,
 635         .resize = pty_resize
 636 };
 637
 638 static const struct tty_operations pty_unix98_ops = {
 639         .lookup = pts_unix98_lookup,
 640         .install = pty_unix98_install,
 641         .remove = pty_unix98_remove,
 642         .open = pty_open,
 643         .close = pty_close,
 644         .write = pty_write,
 645         .write_room = pty_write_room,
 646         .flush_buffer = pty_flush_buffer,
 647         .chars_in_buffer = pty_chars_in_buffer,
 648         .unthrottle = pty_unthrottle,
 649         .set_termios = pty_set_termios,
 650         .shutdown = pty_unix98_shutdown
 651 };
 652
 653 /**
 654  *      ptmx_open               -       open a unix 98 pty master
 655  *      @inode: inode of device file
 656  *      @filp: file pointer to tty
 657  *
 658  *      Allocate a unix98 pty master device from the ptmx driver.
 659  *
 660  *      Locking: tty_mutex protects the init_dev work. tty->count should
 661  *              protect the rest.
 662  *              allocated_ptys_lock handles the list of free pty numbers
 663  */
 664
 665 static int ptmx_open(struct inode *inode, struct file *filp)
 666 {
 667         struct tty_struct *tty;
 668         int retval;
 669         int index;
 670
 671         nonseekable_open(inode, filp);
 672
 673         retval = tty_alloc_file(filp);
 674         if (retval)
 675                 return retval;
 676
 677         /* find a device that is not in use. */
 678         tty_lock();
 679         index = devpts_new_index(inode);
 680         tty_unlock();
 681         if (index < 0) {
 682                 retval = index;
 683                 goto err_file;
 684         }
 685
 686         mutex_lock(&tty_mutex);
 687         tty_lock();
 688         tty = tty_init_dev(ptm_driver, index, 1);
 689         mutex_unlock(&tty_mutex);
 690
 691         if (IS_ERR(tty)) {
 692                 retval = PTR_ERR(tty);
 693                 goto out;
 694         }
 695
 696         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 697
 698         tty_add_file(tty, filp);
 699
 700         retval = devpts_pty_new(inode, tty->link);
 701         if (retval)
 702                 goto err_release;
 703
 704         retval = ptm_driver->ops->open(tty, filp);
 705         if (retval)
 706                 goto err_release;
 707
 708         tty_unlock();
 709         return 0;
 710 err_release:
 711         tty_unlock();
 712         tty_release(inode, filp);
 713         return retval;
 714 out:
 715         devpts_kill_index(inode, index);
 716         tty_unlock();
 717 err_file:
 718         tty_free_file(filp);
 719         return retval;
 720 }
 721
 722 static struct file_operations ptmx_fops;
 723
 724 static void __init unix98_pty_init(void)
 725 {
 726         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 727         if (!ptm_driver)
 728                 panic("Couldn't allocate Unix98 ptm driver");
 729         pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 730         if (!pts_driver)
 731                 panic("Couldn't allocate Unix98 pts driver");
 732
 733         ptm_driver->owner = THIS_MODULE;
 734         ptm_driver->driver_name = "pty_master";
 735         ptm_driver->name = "ptm";
 736         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 737         ptm_driver->minor_start = 0;
 738         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 739         ptm_driver->subtype = PTY_TYPE_MASTER;
 740         ptm_driver->init_termios = tty_std_termios;
 741         ptm_driver->init_termios.c_iflag = 0;
 742         ptm_driver->init_termios.c_oflag = 0;
 743         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 744         ptm_driver->init_termios.c_lflag = 0;
 745         ptm_driver->init_termios.c_ispeed = 38400;
 746         ptm_driver->init_termios.c_ospeed = 38400;
 747         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 748                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 749         ptm_driver->other = pts_driver;
 750         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 751
 752         pts_driver->owner = THIS_MODULE;
 753         pts_driver->driver_name = "pty_slave";
 754         pts_driver->name = "pts";
 755         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 756         pts_driver->minor_start = 0;
 757         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 758         pts_driver->subtype = PTY_TYPE_SLAVE;
 759         pts_driver->init_termios = tty_std_termios;
 760         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 761         pts_driver->init_termios.c_ispeed = 38400;
 762         pts_driver->init_termios.c_ospeed = 38400;
 763         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 764                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 765         pts_driver->other = ptm_driver;
 766         tty_set_operations(pts_driver, &pty_unix98_ops);
 767
 768         if (tty_register_driver(ptm_driver))
 769                 panic("Couldn't register Unix98 ptm driver");
 770         if (tty_register_driver(pts_driver))
 771                 panic("Couldn't register Unix98 pts driver");
 772
 773         register_sysctl_table(pty_root_table);
 774
 775         /* Now create the /dev/ptmx special device */
 776         tty_default_fops(&ptmx_fops);
 777         ptmx_fops.open = ptmx_open;
 778
 779         cdev_init(&ptmx_cdev, &ptmx_fops);
 780         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 781             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 782                 panic("Couldn't register /dev/ptmx driver\n");
 783         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 784 }
 785
 786 #else
 787 static inline void unix98_pty_init(void) { }
 788 #endif
 789
 790 static int __init pty_init(void)
 791 {
 792         legacy_pty_init();
 793         unix98_pty_init();
 794         return 0;
 795 }
 796 module_init(pty_init);