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  */
   8
   9 #include <linux/module.h>
  10
  11 #include <linux/errno.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/tty.h>
  14 #include <linux/tty_flip.h>
  15 #include <linux/fcntl.h>
  16 #include <linux/sched.h>
  17 #include <linux/string.h>
  18 #include <linux/major.h>
  19 #include <linux/mm.h>
  20 #include <linux/init.h>
  21 #include <linux/device.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/bitops.h>
  24 #include <linux/devpts_fs.h>
  25 #include <linux/slab.h>
  26 #include <linux/mutex.h>
  27
  28
  29 #ifdef CONFIG_UNIX98_PTYS
  30 static struct tty_driver *ptm_driver;
  31 static struct tty_driver *pts_driver;
  32 static DEFINE_MUTEX(devpts_mutex);
  33 #endif
  34
  35 static void pty_close(struct tty_struct *tty, struct file *filp)
  36 {
  37         BUG_ON(!tty);
  38         if (tty->driver->subtype == PTY_TYPE_MASTER)
  39                 WARN_ON(tty->count > 1);
  40         else {
  41                 if (test_bit(TTY_IO_ERROR, &tty->flags))
  42                         return;
  43                 if (tty->count > 2)
  44                         return;
  45         }
  46         set_bit(TTY_IO_ERROR, &tty->flags);
  47         wake_up_interruptible(&tty->read_wait);
  48         wake_up_interruptible(&tty->write_wait);
  49         tty->packet = 0;
  50         /* Review - krefs on tty_link ?? */
  51         if (!tty->link)
  52                 return;
  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                         mutex_lock(&devpts_mutex);
  61                         if (tty->link->driver_data)
  62                                 devpts_pty_kill(tty->link->driver_data);
  63                         mutex_unlock(&devpts_mutex);
  64                 }
  65 #endif
  66                 tty_unlock(tty);
  67                 tty_vhangup(tty->link);
  68                 tty_lock(tty);
  69         }
  70 }
  71
  72 /*
  73  * The unthrottle routine is called by the line discipline to signal
  74  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  75  * flag is always set, to force the line discipline to always call the
  76  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  77  * characters in the queue.  This is necessary since each time this
  78  * happens, we need to wake up any sleeping processes that could be
  79  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  80  * for the pty buffer to be drained.
  81  */
  82 static void pty_unthrottle(struct tty_struct *tty)
  83 {
  84         tty_wakeup(tty->link);
  85         set_bit(TTY_THROTTLED, &tty->flags);
  86 }
  87
  88 /**
  89  *      pty_space       -       report space left for writing
  90  *      @to: tty we are writing into
  91  *
  92  *      The tty buffers allow 64K but we sneak a peak and clip at 8K this
  93  *      allows a lot of overspill room for echo and other fun messes to
  94  *      be handled properly
  95  */
  96
  97 static int pty_space(struct tty_struct *to)
  98 {
  99         int n = 8192 - to->port->buf.memory_used;
 100         if (n < 0)
 101                 return 0;
 102         return n;
 103 }
 104
 105 /**
 106  *      pty_write               -       write to a pty
 107  *      @tty: the tty we write from
 108  *      @buf: kernel buffer of data
 109  *      @count: bytes to write
 110  *
 111  *      Our "hardware" write method. Data is coming from the ldisc which
 112  *      may be in a non sleeping state. We simply throw this at the other
 113  *      end of the link as if we were an IRQ handler receiving stuff for
 114  *      the other side of the pty/tty pair.
 115  */
 116
 117 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 118 {
 119         struct tty_struct *to = tty->link;
 120
 121         if (tty->stopped)
 122                 return 0;
 123
 124         if (c > 0) {
 125                 /* Stuff the data into the input queue of the other end */
 126                 c = tty_insert_flip_string(to->port, buf, c);
 127                 /* And shovel */
 128                 if (c) {
 129                         tty_flip_buffer_push(to->port);
 130                         tty_wakeup(tty);
 131                 }
 132         }
 133         return c;
 134 }
 135
 136 /**
 137  *      pty_write_room  -       write space
 138  *      @tty: tty we are writing from
 139  *
 140  *      Report how many bytes the ldisc can send into the queue for
 141  *      the other device.
 142  */
 143
 144 static int pty_write_room(struct tty_struct *tty)
 145 {
 146         if (tty->stopped)
 147                 return 0;
 148         return pty_space(tty->link);
 149 }
 150
 151 /**
 152  *      pty_chars_in_buffer     -       characters currently in our tx queue
 153  *      @tty: our tty
 154  *
 155  *      Report how much we have in the transmit queue. As everything is
 156  *      instantly at the other end this is easy to implement.
 157  */
 158
 159 static int pty_chars_in_buffer(struct tty_struct *tty)
 160 {
 161         return 0;
 162 }
 163
 164 /* Set the lock flag on a pty */
 165 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 166 {
 167         int val;
 168         if (get_user(val, arg))
 169                 return -EFAULT;
 170         if (val)
 171                 set_bit(TTY_PTY_LOCK, &tty->flags);
 172         else
 173                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 174         return 0;
 175 }
 176
 177 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 178 {
 179         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 180         return put_user(locked, arg);
 181 }
 182
 183 /* Set the packet mode on a pty */
 184 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 185 {
 186         unsigned long flags;
 187         int pktmode;
 188
 189         if (get_user(pktmode, arg))
 190                 return -EFAULT;
 191
 192         spin_lock_irqsave(&tty->ctrl_lock, flags);
 193         if (pktmode) {
 194                 if (!tty->packet) {
 195                         tty->packet = 1;
 196                         tty->link->ctrl_status = 0;
 197                 }
 198         } else
 199                 tty->packet = 0;
 200         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 201
 202         return 0;
 203 }
 204
 205 /* Get the packet mode of a pty */
 206 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 207 {
 208         int pktmode = tty->packet;
 209         return put_user(pktmode, arg);
 210 }
 211
 212 /* Send a signal to the slave */
 213 static int pty_signal(struct tty_struct *tty, int sig)
 214 {
 215         unsigned long flags;
 216         struct pid *pgrp;
 217
 218         if (tty->link) {
 219                 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
 220                 pgrp = get_pid(tty->link->pgrp);
 221                 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
 222
 223                 kill_pgrp(pgrp, sig, 1);
 224                 put_pid(pgrp);
 225         }
 226         return 0;
 227 }
 228
 229 static void pty_flush_buffer(struct tty_struct *tty)
 230 {
 231         struct tty_struct *to = tty->link;
 232         unsigned long flags;
 233
 234         if (!to)
 235                 return;
 236         /* tty_buffer_flush(to); FIXME */
 237         if (to->packet) {
 238                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 239                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 240                 wake_up_interruptible(&to->read_wait);
 241                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 242         }
 243 }
 244
 245 static int pty_open(struct tty_struct *tty, struct file *filp)
 246 {
 247         if (!tty || !tty->link)
 248                 return -ENODEV;
 249
 250         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 251                 goto out;
 252         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 253                 goto out;
 254         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 255                 goto out;
 256
 257         clear_bit(TTY_IO_ERROR, &tty->flags);
 258         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 259         set_bit(TTY_THROTTLED, &tty->flags);
 260         return 0;
 261
 262 out:
 263         set_bit(TTY_IO_ERROR, &tty->flags);
 264         return -EIO;
 265 }
 266
 267 static void pty_set_termios(struct tty_struct *tty,
 268                                         struct ktermios *old_termios)
 269 {
 270         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 271         tty->termios.c_cflag |= (CS8 | CREAD);
 272 }
 273
 274 /**
 275  *      pty_do_resize           -       resize event
 276  *      @tty: tty being resized
 277  *      @ws: window size being set.
 278  *
 279  *      Update the termios variables and send the necessary signals to
 280  *      peform a terminal resize correctly
 281  */
 282
 283 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 284 {
 285         struct pid *pgrp, *rpgrp;
 286         unsigned long flags;
 287         struct tty_struct *pty = tty->link;
 288
 289         /* For a PTY we need to lock the tty side */
 290         mutex_lock(&tty->termios_mutex);
 291         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 292                 goto done;
 293
 294         /* Get the PID values and reference them so we can
 295            avoid holding the tty ctrl lock while sending signals.
 296            We need to lock these individually however. */
 297
 298         spin_lock_irqsave(&tty->ctrl_lock, flags);
 299         pgrp = get_pid(tty->pgrp);
 300         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 301
 302         spin_lock_irqsave(&pty->ctrl_lock, flags);
 303         rpgrp = get_pid(pty->pgrp);
 304         spin_unlock_irqrestore(&pty->ctrl_lock, flags);
 305
 306         if (pgrp)
 307                 kill_pgrp(pgrp, SIGWINCH, 1);
 308         if (rpgrp != pgrp && rpgrp)
 309                 kill_pgrp(rpgrp, SIGWINCH, 1);
 310
 311         put_pid(pgrp);
 312         put_pid(rpgrp);
 313
 314         tty->winsize = *ws;
 315         pty->winsize = *ws;     /* Never used so will go away soon */
 316 done:
 317         mutex_unlock(&tty->termios_mutex);
 318         return 0;
 319 }
 320
 321 /**
 322  *      pty_common_install              -       set up the pty pair
 323  *      @driver: the pty driver
 324  *      @tty: the tty being instantiated
 325  *      @bool: legacy, true if this is BSD style
 326  *
 327  *      Perform the initial set up for the tty/pty pair. Called from the
 328  *      tty layer when the port is first opened.
 329  *
 330  *      Locking: the caller must hold the tty_mutex
 331  */
 332 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 333                 bool legacy)
 334 {
 335         struct tty_struct *o_tty;
 336         struct tty_port *ports[2];
 337         int idx = tty->index;
 338         int retval = -ENOMEM;
 339
 340         o_tty = alloc_tty_struct();
 341         if (!o_tty)
 342                 goto err;
 343         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 344         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 345         if (!ports[0] || !ports[1])
 346                 goto err_free_tty;
 347         if (!try_module_get(driver->other->owner)) {
 348                 /* This cannot in fact currently happen */
 349                 goto err_free_tty;
 350         }
 351         initialize_tty_struct(o_tty, driver->other, idx);
 352
 353         if (legacy) {
 354                 /* We always use new tty termios data so we can do this
 355                    the easy way .. */
 356                 retval = tty_init_termios(tty);
 357                 if (retval)
 358                         goto err_deinit_tty;
 359
 360                 retval = tty_init_termios(o_tty);
 361                 if (retval)
 362                         goto err_free_termios;
 363
 364                 driver->other->ttys[idx] = o_tty;
 365                 driver->ttys[idx] = tty;
 366         } else {
 367                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 368                 tty->termios = driver->init_termios;
 369                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 370                 o_tty->termios = driver->other->init_termios;
 371         }
 372
 373         /*
 374          * Everything allocated ... set up the o_tty structure.
 375          */
 376         tty_driver_kref_get(driver->other);
 377         if (driver->subtype == PTY_TYPE_MASTER)
 378                 o_tty->count++;
 379         /* Establish the links in both directions */
 380         tty->link   = o_tty;
 381         o_tty->link = tty;
 382         tty_port_init(ports[0]);
 383         tty_port_init(ports[1]);
 384         o_tty->port = ports[0];
 385         tty->port = ports[1];
 386         o_tty->port->itty = o_tty;
 387
 388         tty_driver_kref_get(driver);
 389         tty->count++;
 390         return 0;
 391 err_free_termios:
 392         if (legacy)
 393                 tty_free_termios(tty);
 394 err_deinit_tty:
 395         deinitialize_tty_struct(o_tty);
 396         module_put(o_tty->driver->owner);
 397 err_free_tty:
 398         kfree(ports[0]);
 399         kfree(ports[1]);
 400         free_tty_struct(o_tty);
 401 err:
 402         return retval;
 403 }
 404
 405 static void pty_cleanup(struct tty_struct *tty)
 406 {
 407         tty_port_put(tty->port);
 408 }
 409
 410 /* Traditional BSD devices */
 411 #ifdef CONFIG_LEGACY_PTYS
 412
 413 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 414 {
 415         return pty_common_install(driver, tty, true);
 416 }
 417
 418 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 419 {
 420         struct tty_struct *pair = tty->link;
 421         driver->ttys[tty->index] = NULL;
 422         if (pair)
 423                 pair->driver->ttys[pair->index] = NULL;
 424 }
 425
 426 static int pty_bsd_ioctl(struct tty_struct *tty,
 427                          unsigned int cmd, unsigned long arg)
 428 {
 429         switch (cmd) {
 430         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 431                 return pty_set_lock(tty, (int __user *) arg);
 432         case TIOCGPTLCK: /* Get PT Lock status */
 433                 return pty_get_lock(tty, (int __user *)arg);
 434         case TIOCPKT: /* Set PT packet mode */
 435                 return pty_set_pktmode(tty, (int __user *)arg);
 436         case TIOCGPKT: /* Get PT packet mode */
 437                 return pty_get_pktmode(tty, (int __user *)arg);
 438         case TIOCSIG:    /* Send signal to other side of pty */
 439                 return pty_signal(tty, (int) arg);
 440         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 441                 return -EINVAL;
 442         }
 443         return -ENOIOCTLCMD;
 444 }
 445
 446 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 447 module_param(legacy_count, int, 0);
 448
 449 /*
 450  * The master side of a pty can do TIOCSPTLCK and thus
 451  * has pty_bsd_ioctl.
 452  */
 453 static const struct tty_operations master_pty_ops_bsd = {
 454         .install = pty_install,
 455         .open = pty_open,
 456         .close = pty_close,
 457         .write = pty_write,
 458         .write_room = pty_write_room,
 459         .flush_buffer = pty_flush_buffer,
 460         .chars_in_buffer = pty_chars_in_buffer,
 461         .unthrottle = pty_unthrottle,
 462         .set_termios = pty_set_termios,
 463         .ioctl = pty_bsd_ioctl,
 464         .cleanup = pty_cleanup,
 465         .resize = pty_resize,
 466         .remove = pty_remove
 467 };
 468
 469 static const struct tty_operations slave_pty_ops_bsd = {
 470         .install = pty_install,
 471         .open = pty_open,
 472         .close = pty_close,
 473         .write = pty_write,
 474         .write_room = pty_write_room,
 475         .flush_buffer = pty_flush_buffer,
 476         .chars_in_buffer = pty_chars_in_buffer,
 477         .unthrottle = pty_unthrottle,
 478         .set_termios = pty_set_termios,
 479         .cleanup = pty_cleanup,
 480         .resize = pty_resize,
 481         .remove = pty_remove
 482 };
 483
 484 static void __init legacy_pty_init(void)
 485 {
 486         struct tty_driver *pty_driver, *pty_slave_driver;
 487
 488         if (legacy_count <= 0)
 489                 return;
 490
 491         pty_driver = tty_alloc_driver(legacy_count,
 492                         TTY_DRIVER_RESET_TERMIOS |
 493                         TTY_DRIVER_REAL_RAW |
 494                         TTY_DRIVER_DYNAMIC_ALLOC);
 495         if (IS_ERR(pty_driver))
 496                 panic("Couldn't allocate pty driver");
 497
 498         pty_slave_driver = tty_alloc_driver(legacy_count,
 499                         TTY_DRIVER_RESET_TERMIOS |
 500                         TTY_DRIVER_REAL_RAW |
 501                         TTY_DRIVER_DYNAMIC_ALLOC);
 502         if (IS_ERR(pty_slave_driver))
 503                 panic("Couldn't allocate pty slave driver");
 504
 505         pty_driver->driver_name = "pty_master";
 506         pty_driver->name = "pty";
 507         pty_driver->major = PTY_MASTER_MAJOR;
 508         pty_driver->minor_start = 0;
 509         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 510         pty_driver->subtype = PTY_TYPE_MASTER;
 511         pty_driver->init_termios = tty_std_termios;
 512         pty_driver->init_termios.c_iflag = 0;
 513         pty_driver->init_termios.c_oflag = 0;
 514         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 515         pty_driver->init_termios.c_lflag = 0;
 516         pty_driver->init_termios.c_ispeed = 38400;
 517         pty_driver->init_termios.c_ospeed = 38400;
 518         pty_driver->other = pty_slave_driver;
 519         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 520
 521         pty_slave_driver->driver_name = "pty_slave";
 522         pty_slave_driver->name = "ttyp";
 523         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 524         pty_slave_driver->minor_start = 0;
 525         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 526         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 527         pty_slave_driver->init_termios = tty_std_termios;
 528         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 529         pty_slave_driver->init_termios.c_ispeed = 38400;
 530         pty_slave_driver->init_termios.c_ospeed = 38400;
 531         pty_slave_driver->other = pty_driver;
 532         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 533
 534         if (tty_register_driver(pty_driver))
 535                 panic("Couldn't register pty driver");
 536         if (tty_register_driver(pty_slave_driver))
 537                 panic("Couldn't register pty slave driver");
 538 }
 539 #else
 540 static inline void legacy_pty_init(void) { }
 541 #endif
 542
 543 /* Unix98 devices */
 544 #ifdef CONFIG_UNIX98_PTYS
 545
 546 static struct cdev ptmx_cdev;
 547
 548 static int pty_unix98_ioctl(struct tty_struct *tty,
 549                             unsigned int cmd, unsigned long arg)
 550 {
 551         switch (cmd) {
 552         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 553                 return pty_set_lock(tty, (int __user *)arg);
 554         case TIOCGPTLCK: /* Get PT Lock status */
 555                 return pty_get_lock(tty, (int __user *)arg);
 556         case TIOCPKT: /* Set PT packet mode */
 557                 return pty_set_pktmode(tty, (int __user *)arg);
 558         case TIOCGPKT: /* Get PT packet mode */
 559                 return pty_get_pktmode(tty, (int __user *)arg);
 560         case TIOCGPTN: /* Get PT Number */
 561                 return put_user(tty->index, (unsigned int __user *)arg);
 562         case TIOCSIG:    /* Send signal to other side of pty */
 563                 return pty_signal(tty, (int) arg);
 564         }
 565
 566         return -ENOIOCTLCMD;
 567 }
 568
 569 /**
 570  *      ptm_unix98_lookup       -       find a pty master
 571  *      @driver: ptm driver
 572  *      @idx: tty index
 573  *
 574  *      Look up a pty master device. Called under the tty_mutex for now.
 575  *      This provides our locking.
 576  */
 577
 578 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 579                 struct inode *ptm_inode, int idx)
 580 {
 581         /* Master must be open via /dev/ptmx */
 582         return ERR_PTR(-EIO);
 583 }
 584
 585 /**
 586  *      pts_unix98_lookup       -       find a pty slave
 587  *      @driver: pts driver
 588  *      @idx: tty index
 589  *
 590  *      Look up a pty master device. Called under the tty_mutex for now.
 591  *      This provides our locking for the tty pointer.
 592  */
 593
 594 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 595                 struct inode *pts_inode, int idx)
 596 {
 597         struct tty_struct *tty;
 598
 599         mutex_lock(&devpts_mutex);
 600         tty = devpts_get_priv(pts_inode);
 601         mutex_unlock(&devpts_mutex);
 602         /* Master must be open before slave */
 603         if (!tty)
 604                 return ERR_PTR(-EIO);
 605         return tty;
 606 }
 607
 608 /* We have no need to install and remove our tty objects as devpts does all
 609    the work for us */
 610
 611 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 612 {
 613         return pty_common_install(driver, tty, false);
 614 }
 615
 616 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 617 {
 618 }
 619
 620 /* this is called once with whichever end is closed last */
 621 static void pty_unix98_shutdown(struct tty_struct *tty)
 622 {
 623         devpts_kill_index(tty->driver_data, tty->index);
 624 }
 625
 626 static const struct tty_operations ptm_unix98_ops = {
 627         .lookup = ptm_unix98_lookup,
 628         .install = pty_unix98_install,
 629         .remove = pty_unix98_remove,
 630         .open = pty_open,
 631         .close = pty_close,
 632         .write = pty_write,
 633         .write_room = pty_write_room,
 634         .flush_buffer = pty_flush_buffer,
 635         .chars_in_buffer = pty_chars_in_buffer,
 636         .unthrottle = pty_unthrottle,
 637         .set_termios = pty_set_termios,
 638         .ioctl = pty_unix98_ioctl,
 639         .resize = pty_resize,
 640         .shutdown = pty_unix98_shutdown,
 641         .cleanup = pty_cleanup
 642 };
 643
 644 static const struct tty_operations pty_unix98_ops = {
 645         .lookup = pts_unix98_lookup,
 646         .install = pty_unix98_install,
 647         .remove = pty_unix98_remove,
 648         .open = pty_open,
 649         .close = pty_close,
 650         .write = pty_write,
 651         .write_room = pty_write_room,
 652         .flush_buffer = pty_flush_buffer,
 653         .chars_in_buffer = pty_chars_in_buffer,
 654         .unthrottle = pty_unthrottle,
 655         .set_termios = pty_set_termios,
 656         .shutdown = pty_unix98_shutdown,
 657         .cleanup = pty_cleanup,
 658 };
 659
 660 /**
 661  *      ptmx_open               -       open a unix 98 pty master
 662  *      @inode: inode of device file
 663  *      @filp: file pointer to tty
 664  *
 665  *      Allocate a unix98 pty master device from the ptmx driver.
 666  *
 667  *      Locking: tty_mutex protects the init_dev work. tty->count should
 668  *              protect the rest.
 669  *              allocated_ptys_lock handles the list of free pty numbers
 670  */
 671
 672 static int ptmx_open(struct inode *inode, struct file *filp)
 673 {
 674         struct tty_struct *tty;
 675         struct inode *slave_inode;
 676         int retval;
 677         int index;
 678
 679         nonseekable_open(inode, filp);
 680
 681         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 682         filp->f_mode |= FMODE_NONOTIFY;
 683
 684         retval = tty_alloc_file(filp);
 685         if (retval)
 686                 return retval;
 687
 688         /* find a device that is not in use. */
 689         mutex_lock(&devpts_mutex);
 690         index = devpts_new_index(inode);
 691         if (index < 0) {
 692                 retval = index;
 693                 mutex_unlock(&devpts_mutex);
 694                 goto err_file;
 695         }
 696
 697         mutex_unlock(&devpts_mutex);
 698
 699         mutex_lock(&tty_mutex);
 700         tty = tty_init_dev(ptm_driver, index);
 701
 702         if (IS_ERR(tty)) {
 703                 retval = PTR_ERR(tty);
 704                 goto out;
 705         }
 706
 707         /* The tty returned here is locked so we can safely
 708            drop the mutex */
 709         mutex_unlock(&tty_mutex);
 710
 711         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 712         tty->driver_data = inode;
 713
 714         tty_add_file(tty, filp);
 715
 716         slave_inode = devpts_pty_new(inode,
 717                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 718                         tty->link);
 719         if (IS_ERR(slave_inode)) {
 720                 retval = PTR_ERR(slave_inode);
 721                 goto err_release;
 722         }
 723         tty->link->driver_data = slave_inode;
 724
 725         retval = ptm_driver->ops->open(tty, filp);
 726         if (retval)
 727                 goto err_release;
 728
 729         tty_unlock(tty);
 730         return 0;
 731 err_release:
 732         tty_unlock(tty);
 733         tty_release(inode, filp);
 734         return retval;
 735 out:
 736         mutex_unlock(&tty_mutex);
 737         devpts_kill_index(inode, index);
 738 err_file:
 739         tty_free_file(filp);
 740         return retval;
 741 }
 742
 743 static struct file_operations ptmx_fops;
 744
 745 static void __init unix98_pty_init(void)
 746 {
 747         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 748                         TTY_DRIVER_RESET_TERMIOS |
 749                         TTY_DRIVER_REAL_RAW |
 750                         TTY_DRIVER_DYNAMIC_DEV |
 751                         TTY_DRIVER_DEVPTS_MEM |
 752                         TTY_DRIVER_DYNAMIC_ALLOC);
 753         if (IS_ERR(ptm_driver))
 754                 panic("Couldn't allocate Unix98 ptm driver");
 755         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 756                         TTY_DRIVER_RESET_TERMIOS |
 757                         TTY_DRIVER_REAL_RAW |
 758                         TTY_DRIVER_DYNAMIC_DEV |
 759                         TTY_DRIVER_DEVPTS_MEM |
 760                         TTY_DRIVER_DYNAMIC_ALLOC);
 761         if (IS_ERR(pts_driver))
 762                 panic("Couldn't allocate Unix98 pts driver");
 763
 764         ptm_driver->driver_name = "pty_master";
 765         ptm_driver->name = "ptm";
 766         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 767         ptm_driver->minor_start = 0;
 768         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 769         ptm_driver->subtype = PTY_TYPE_MASTER;
 770         ptm_driver->init_termios = tty_std_termios;
 771         ptm_driver->init_termios.c_iflag = 0;
 772         ptm_driver->init_termios.c_oflag = 0;
 773         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 774         ptm_driver->init_termios.c_lflag = 0;
 775         ptm_driver->init_termios.c_ispeed = 38400;
 776         ptm_driver->init_termios.c_ospeed = 38400;
 777         ptm_driver->other = pts_driver;
 778         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 779
 780         pts_driver->driver_name = "pty_slave";
 781         pts_driver->name = "pts";
 782         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 783         pts_driver->minor_start = 0;
 784         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 785         pts_driver->subtype = PTY_TYPE_SLAVE;
 786         pts_driver->init_termios = tty_std_termios;
 787         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 788         pts_driver->init_termios.c_ispeed = 38400;
 789         pts_driver->init_termios.c_ospeed = 38400;
 790         pts_driver->other = ptm_driver;
 791         tty_set_operations(pts_driver, &pty_unix98_ops);
 792
 793         if (tty_register_driver(ptm_driver))
 794                 panic("Couldn't register Unix98 ptm driver");
 795         if (tty_register_driver(pts_driver))
 796                 panic("Couldn't register Unix98 pts driver");
 797
 798         /* Now create the /dev/ptmx special device */
 799         tty_default_fops(&ptmx_fops);
 800         ptmx_fops.open = ptmx_open;
 801
 802         cdev_init(&ptmx_cdev, &ptmx_fops);
 803         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 804             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 805                 panic("Couldn't register /dev/ptmx driver");
 806         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 807 }
 808
 809 #else
 810 static inline void unix98_pty_init(void) { }
 811 #endif
 812
 813 static int __init pty_init(void)
 814 {
 815         legacy_pty_init();
 816         unix98_pty_init();
 817         return 0;
 818 }
 819 module_init(pty_init);