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 (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 219                 return -EINVAL;
 220
 221         if (tty->link) {
 222                 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
 223                 pgrp = get_pid(tty->link->pgrp);
 224                 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
 225
 226                 kill_pgrp(pgrp, sig, 1);
 227                 put_pid(pgrp);
 228         }
 229         return 0;
 230 }
 231
 232 static void pty_flush_buffer(struct tty_struct *tty)
 233 {
 234         struct tty_struct *to = tty->link;
 235         unsigned long flags;
 236
 237         if (!to)
 238                 return;
 239         /* tty_buffer_flush(to); FIXME */
 240         if (to->packet) {
 241                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 242                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 243                 wake_up_interruptible(&to->read_wait);
 244                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 245         }
 246 }
 247
 248 static int pty_open(struct tty_struct *tty, struct file *filp)
 249 {
 250         if (!tty || !tty->link)
 251                 return -ENODEV;
 252
 253         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 254                 goto out;
 255         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 256                 goto out;
 257         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 258                 goto out;
 259
 260         clear_bit(TTY_IO_ERROR, &tty->flags);
 261         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 262         set_bit(TTY_THROTTLED, &tty->flags);
 263         return 0;
 264
 265 out:
 266         set_bit(TTY_IO_ERROR, &tty->flags);
 267         return -EIO;
 268 }
 269
 270 static void pty_set_termios(struct tty_struct *tty,
 271                                         struct ktermios *old_termios)
 272 {
 273         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 274         tty->termios.c_cflag |= (CS8 | CREAD);
 275 }
 276
 277 /**
 278  *      pty_do_resize           -       resize event
 279  *      @tty: tty being resized
 280  *      @ws: window size being set.
 281  *
 282  *      Update the termios variables and send the necessary signals to
 283  *      peform a terminal resize correctly
 284  */
 285
 286 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 287 {
 288         struct pid *pgrp, *rpgrp;
 289         unsigned long flags;
 290         struct tty_struct *pty = tty->link;
 291
 292         /* For a PTY we need to lock the tty side */
 293         mutex_lock(&tty->termios_mutex);
 294         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 295                 goto done;
 296
 297         /* Get the PID values and reference them so we can
 298            avoid holding the tty ctrl lock while sending signals.
 299            We need to lock these individually however. */
 300
 301         spin_lock_irqsave(&tty->ctrl_lock, flags);
 302         pgrp = get_pid(tty->pgrp);
 303         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 304
 305         spin_lock_irqsave(&pty->ctrl_lock, flags);
 306         rpgrp = get_pid(pty->pgrp);
 307         spin_unlock_irqrestore(&pty->ctrl_lock, flags);
 308
 309         if (pgrp)
 310                 kill_pgrp(pgrp, SIGWINCH, 1);
 311         if (rpgrp != pgrp && rpgrp)
 312                 kill_pgrp(rpgrp, SIGWINCH, 1);
 313
 314         put_pid(pgrp);
 315         put_pid(rpgrp);
 316
 317         tty->winsize = *ws;
 318         pty->winsize = *ws;     /* Never used so will go away soon */
 319 done:
 320         mutex_unlock(&tty->termios_mutex);
 321         return 0;
 322 }
 323
 324 /**
 325  *      pty_common_install              -       set up the pty pair
 326  *      @driver: the pty driver
 327  *      @tty: the tty being instantiated
 328  *      @bool: legacy, true if this is BSD style
 329  *
 330  *      Perform the initial set up for the tty/pty pair. Called from the
 331  *      tty layer when the port is first opened.
 332  *
 333  *      Locking: the caller must hold the tty_mutex
 334  */
 335 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 336                 bool legacy)
 337 {
 338         struct tty_struct *o_tty;
 339         struct tty_port *ports[2];
 340         int idx = tty->index;
 341         int retval = -ENOMEM;
 342
 343         o_tty = alloc_tty_struct();
 344         if (!o_tty)
 345                 goto err;
 346         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 347         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 348         if (!ports[0] || !ports[1])
 349                 goto err_free_tty;
 350         if (!try_module_get(driver->other->owner)) {
 351                 /* This cannot in fact currently happen */
 352                 goto err_free_tty;
 353         }
 354         initialize_tty_struct(o_tty, driver->other, idx);
 355
 356         if (legacy) {
 357                 /* We always use new tty termios data so we can do this
 358                    the easy way .. */
 359                 retval = tty_init_termios(tty);
 360                 if (retval)
 361                         goto err_deinit_tty;
 362
 363                 retval = tty_init_termios(o_tty);
 364                 if (retval)
 365                         goto err_free_termios;
 366
 367                 driver->other->ttys[idx] = o_tty;
 368                 driver->ttys[idx] = tty;
 369         } else {
 370                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 371                 tty->termios = driver->init_termios;
 372                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 373                 o_tty->termios = driver->other->init_termios;
 374         }
 375
 376         /*
 377          * Everything allocated ... set up the o_tty structure.
 378          */
 379         tty_driver_kref_get(driver->other);
 380         if (driver->subtype == PTY_TYPE_MASTER)
 381                 o_tty->count++;
 382         /* Establish the links in both directions */
 383         tty->link   = o_tty;
 384         o_tty->link = tty;
 385         tty_port_init(ports[0]);
 386         tty_port_init(ports[1]);
 387         o_tty->port = ports[0];
 388         tty->port = ports[1];
 389         o_tty->port->itty = o_tty;
 390
 391         tty_driver_kref_get(driver);
 392         tty->count++;
 393         return 0;
 394 err_free_termios:
 395         if (legacy)
 396                 tty_free_termios(tty);
 397 err_deinit_tty:
 398         deinitialize_tty_struct(o_tty);
 399         module_put(o_tty->driver->owner);
 400 err_free_tty:
 401         kfree(ports[0]);
 402         kfree(ports[1]);
 403         free_tty_struct(o_tty);
 404 err:
 405         return retval;
 406 }
 407
 408 static void pty_cleanup(struct tty_struct *tty)
 409 {
 410         tty_port_put(tty->port);
 411 }
 412
 413 /* Traditional BSD devices */
 414 #ifdef CONFIG_LEGACY_PTYS
 415
 416 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 417 {
 418         return pty_common_install(driver, tty, true);
 419 }
 420
 421 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 422 {
 423         struct tty_struct *pair = tty->link;
 424         driver->ttys[tty->index] = NULL;
 425         if (pair)
 426                 pair->driver->ttys[pair->index] = NULL;
 427 }
 428
 429 static int pty_bsd_ioctl(struct tty_struct *tty,
 430                          unsigned int cmd, unsigned long arg)
 431 {
 432         switch (cmd) {
 433         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 434                 return pty_set_lock(tty, (int __user *) arg);
 435         case TIOCGPTLCK: /* Get PT Lock status */
 436                 return pty_get_lock(tty, (int __user *)arg);
 437         case TIOCPKT: /* Set PT packet mode */
 438                 return pty_set_pktmode(tty, (int __user *)arg);
 439         case TIOCGPKT: /* Get PT packet mode */
 440                 return pty_get_pktmode(tty, (int __user *)arg);
 441         case TIOCSIG:    /* Send signal to other side of pty */
 442                 return pty_signal(tty, (int) arg);
 443         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 444                 return -EINVAL;
 445         }
 446         return -ENOIOCTLCMD;
 447 }
 448
 449 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 450 module_param(legacy_count, int, 0);
 451
 452 /*
 453  * The master side of a pty can do TIOCSPTLCK and thus
 454  * has pty_bsd_ioctl.
 455  */
 456 static const struct tty_operations master_pty_ops_bsd = {
 457         .install = pty_install,
 458         .open = pty_open,
 459         .close = pty_close,
 460         .write = pty_write,
 461         .write_room = pty_write_room,
 462         .flush_buffer = pty_flush_buffer,
 463         .chars_in_buffer = pty_chars_in_buffer,
 464         .unthrottle = pty_unthrottle,
 465         .set_termios = pty_set_termios,
 466         .ioctl = pty_bsd_ioctl,
 467         .cleanup = pty_cleanup,
 468         .resize = pty_resize,
 469         .remove = pty_remove
 470 };
 471
 472 static const struct tty_operations slave_pty_ops_bsd = {
 473         .install = pty_install,
 474         .open = pty_open,
 475         .close = pty_close,
 476         .write = pty_write,
 477         .write_room = pty_write_room,
 478         .flush_buffer = pty_flush_buffer,
 479         .chars_in_buffer = pty_chars_in_buffer,
 480         .unthrottle = pty_unthrottle,
 481         .set_termios = pty_set_termios,
 482         .cleanup = pty_cleanup,
 483         .resize = pty_resize,
 484         .remove = pty_remove
 485 };
 486
 487 static void __init legacy_pty_init(void)
 488 {
 489         struct tty_driver *pty_driver, *pty_slave_driver;
 490
 491         if (legacy_count <= 0)
 492                 return;
 493
 494         pty_driver = tty_alloc_driver(legacy_count,
 495                         TTY_DRIVER_RESET_TERMIOS |
 496                         TTY_DRIVER_REAL_RAW |
 497                         TTY_DRIVER_DYNAMIC_ALLOC);
 498         if (IS_ERR(pty_driver))
 499                 panic("Couldn't allocate pty driver");
 500
 501         pty_slave_driver = tty_alloc_driver(legacy_count,
 502                         TTY_DRIVER_RESET_TERMIOS |
 503                         TTY_DRIVER_REAL_RAW |
 504                         TTY_DRIVER_DYNAMIC_ALLOC);
 505         if (IS_ERR(pty_slave_driver))
 506                 panic("Couldn't allocate pty slave driver");
 507
 508         pty_driver->driver_name = "pty_master";
 509         pty_driver->name = "pty";
 510         pty_driver->major = PTY_MASTER_MAJOR;
 511         pty_driver->minor_start = 0;
 512         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 513         pty_driver->subtype = PTY_TYPE_MASTER;
 514         pty_driver->init_termios = tty_std_termios;
 515         pty_driver->init_termios.c_iflag = 0;
 516         pty_driver->init_termios.c_oflag = 0;
 517         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 518         pty_driver->init_termios.c_lflag = 0;
 519         pty_driver->init_termios.c_ispeed = 38400;
 520         pty_driver->init_termios.c_ospeed = 38400;
 521         pty_driver->other = pty_slave_driver;
 522         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 523
 524         pty_slave_driver->driver_name = "pty_slave";
 525         pty_slave_driver->name = "ttyp";
 526         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 527         pty_slave_driver->minor_start = 0;
 528         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 529         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 530         pty_slave_driver->init_termios = tty_std_termios;
 531         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 532         pty_slave_driver->init_termios.c_ispeed = 38400;
 533         pty_slave_driver->init_termios.c_ospeed = 38400;
 534         pty_slave_driver->other = pty_driver;
 535         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 536
 537         if (tty_register_driver(pty_driver))
 538                 panic("Couldn't register pty driver");
 539         if (tty_register_driver(pty_slave_driver))
 540                 panic("Couldn't register pty slave driver");
 541 }
 542 #else
 543 static inline void legacy_pty_init(void) { }
 544 #endif
 545
 546 /* Unix98 devices */
 547 #ifdef CONFIG_UNIX98_PTYS
 548
 549 static struct cdev ptmx_cdev;
 550
 551 static int pty_unix98_ioctl(struct tty_struct *tty,
 552                             unsigned int cmd, unsigned long arg)
 553 {
 554         switch (cmd) {
 555         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 556                 return pty_set_lock(tty, (int __user *)arg);
 557         case TIOCGPTLCK: /* Get PT Lock status */
 558                 return pty_get_lock(tty, (int __user *)arg);
 559         case TIOCPKT: /* Set PT packet mode */
 560                 return pty_set_pktmode(tty, (int __user *)arg);
 561         case TIOCGPKT: /* Get PT packet mode */
 562                 return pty_get_pktmode(tty, (int __user *)arg);
 563         case TIOCGPTN: /* Get PT Number */
 564                 return put_user(tty->index, (unsigned int __user *)arg);
 565         case TIOCSIG:    /* Send signal to other side of pty */
 566                 return pty_signal(tty, (int) arg);
 567         }
 568
 569         return -ENOIOCTLCMD;
 570 }
 571
 572 /**
 573  *      ptm_unix98_lookup       -       find a pty master
 574  *      @driver: ptm driver
 575  *      @idx: tty index
 576  *
 577  *      Look up a pty master device. Called under the tty_mutex for now.
 578  *      This provides our locking.
 579  */
 580
 581 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 582                 struct inode *ptm_inode, int idx)
 583 {
 584         /* Master must be open via /dev/ptmx */
 585         return ERR_PTR(-EIO);
 586 }
 587
 588 /**
 589  *      pts_unix98_lookup       -       find a pty slave
 590  *      @driver: pts driver
 591  *      @idx: tty index
 592  *
 593  *      Look up a pty master device. Called under the tty_mutex for now.
 594  *      This provides our locking for the tty pointer.
 595  */
 596
 597 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 598                 struct inode *pts_inode, int idx)
 599 {
 600         struct tty_struct *tty;
 601
 602         mutex_lock(&devpts_mutex);
 603         tty = devpts_get_priv(pts_inode);
 604         mutex_unlock(&devpts_mutex);
 605         /* Master must be open before slave */
 606         if (!tty)
 607                 return ERR_PTR(-EIO);
 608         return tty;
 609 }
 610
 611 /* We have no need to install and remove our tty objects as devpts does all
 612    the work for us */
 613
 614 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 615 {
 616         return pty_common_install(driver, tty, false);
 617 }
 618
 619 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 620 {
 621 }
 622
 623 /* this is called once with whichever end is closed last */
 624 static void pty_unix98_shutdown(struct tty_struct *tty)
 625 {
 626         devpts_kill_index(tty->driver_data, tty->index);
 627 }
 628
 629 static const struct tty_operations ptm_unix98_ops = {
 630         .lookup = ptm_unix98_lookup,
 631         .install = pty_unix98_install,
 632         .remove = pty_unix98_remove,
 633         .open = pty_open,
 634         .close = pty_close,
 635         .write = pty_write,
 636         .write_room = pty_write_room,
 637         .flush_buffer = pty_flush_buffer,
 638         .chars_in_buffer = pty_chars_in_buffer,
 639         .unthrottle = pty_unthrottle,
 640         .set_termios = pty_set_termios,
 641         .ioctl = pty_unix98_ioctl,
 642         .resize = pty_resize,
 643         .shutdown = pty_unix98_shutdown,
 644         .cleanup = pty_cleanup
 645 };
 646
 647 static const struct tty_operations pty_unix98_ops = {
 648         .lookup = pts_unix98_lookup,
 649         .install = pty_unix98_install,
 650         .remove = pty_unix98_remove,
 651         .open = pty_open,
 652         .close = pty_close,
 653         .write = pty_write,
 654         .write_room = pty_write_room,
 655         .flush_buffer = pty_flush_buffer,
 656         .chars_in_buffer = pty_chars_in_buffer,
 657         .unthrottle = pty_unthrottle,
 658         .set_termios = pty_set_termios,
 659         .shutdown = pty_unix98_shutdown,
 660         .cleanup = pty_cleanup,
 661 };
 662
 663 /**
 664  *      ptmx_open               -       open a unix 98 pty master
 665  *      @inode: inode of device file
 666  *      @filp: file pointer to tty
 667  *
 668  *      Allocate a unix98 pty master device from the ptmx driver.
 669  *
 670  *      Locking: tty_mutex protects the init_dev work. tty->count should
 671  *              protect the rest.
 672  *              allocated_ptys_lock handles the list of free pty numbers
 673  */
 674
 675 static int ptmx_open(struct inode *inode, struct file *filp)
 676 {
 677         struct tty_struct *tty;
 678         struct inode *slave_inode;
 679         int retval;
 680         int index;
 681
 682         nonseekable_open(inode, filp);
 683
 684         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 685         filp->f_mode |= FMODE_NONOTIFY;
 686
 687         retval = tty_alloc_file(filp);
 688         if (retval)
 689                 return retval;
 690
 691         /* find a device that is not in use. */
 692         mutex_lock(&devpts_mutex);
 693         index = devpts_new_index(inode);
 694         if (index < 0) {
 695                 retval = index;
 696                 mutex_unlock(&devpts_mutex);
 697                 goto err_file;
 698         }
 699
 700         mutex_unlock(&devpts_mutex);
 701
 702         mutex_lock(&tty_mutex);
 703         tty = tty_init_dev(ptm_driver, index);
 704
 705         if (IS_ERR(tty)) {
 706                 retval = PTR_ERR(tty);
 707                 goto out;
 708         }
 709
 710         /* The tty returned here is locked so we can safely
 711            drop the mutex */
 712         mutex_unlock(&tty_mutex);
 713
 714         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 715         tty->driver_data = inode;
 716
 717         tty_add_file(tty, filp);
 718
 719         slave_inode = devpts_pty_new(inode,
 720                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 721                         tty->link);
 722         if (IS_ERR(slave_inode)) {
 723                 retval = PTR_ERR(slave_inode);
 724                 goto err_release;
 725         }
 726         tty->link->driver_data = slave_inode;
 727
 728         retval = ptm_driver->ops->open(tty, filp);
 729         if (retval)
 730                 goto err_release;
 731
 732         tty_unlock(tty);
 733         return 0;
 734 err_release:
 735         tty_unlock(tty);
 736         tty_release(inode, filp);
 737         return retval;
 738 out:
 739         mutex_unlock(&tty_mutex);
 740         devpts_kill_index(inode, index);
 741 err_file:
 742         tty_free_file(filp);
 743         return retval;
 744 }
 745
 746 static struct file_operations ptmx_fops;
 747
 748 static void __init unix98_pty_init(void)
 749 {
 750         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 751                         TTY_DRIVER_RESET_TERMIOS |
 752                         TTY_DRIVER_REAL_RAW |
 753                         TTY_DRIVER_DYNAMIC_DEV |
 754                         TTY_DRIVER_DEVPTS_MEM |
 755                         TTY_DRIVER_DYNAMIC_ALLOC);
 756         if (IS_ERR(ptm_driver))
 757                 panic("Couldn't allocate Unix98 ptm driver");
 758         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 759                         TTY_DRIVER_RESET_TERMIOS |
 760                         TTY_DRIVER_REAL_RAW |
 761                         TTY_DRIVER_DYNAMIC_DEV |
 762                         TTY_DRIVER_DEVPTS_MEM |
 763                         TTY_DRIVER_DYNAMIC_ALLOC);
 764         if (IS_ERR(pts_driver))
 765                 panic("Couldn't allocate Unix98 pts driver");
 766
 767         ptm_driver->driver_name = "pty_master";
 768         ptm_driver->name = "ptm";
 769         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 770         ptm_driver->minor_start = 0;
 771         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 772         ptm_driver->subtype = PTY_TYPE_MASTER;
 773         ptm_driver->init_termios = tty_std_termios;
 774         ptm_driver->init_termios.c_iflag = 0;
 775         ptm_driver->init_termios.c_oflag = 0;
 776         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 777         ptm_driver->init_termios.c_lflag = 0;
 778         ptm_driver->init_termios.c_ispeed = 38400;
 779         ptm_driver->init_termios.c_ospeed = 38400;
 780         ptm_driver->other = pts_driver;
 781         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 782
 783         pts_driver->driver_name = "pty_slave";
 784         pts_driver->name = "pts";
 785         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 786         pts_driver->minor_start = 0;
 787         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 788         pts_driver->subtype = PTY_TYPE_SLAVE;
 789         pts_driver->init_termios = tty_std_termios;
 790         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 791         pts_driver->init_termios.c_ispeed = 38400;
 792         pts_driver->init_termios.c_ospeed = 38400;
 793         pts_driver->other = ptm_driver;
 794         tty_set_operations(pts_driver, &pty_unix98_ops);
 795
 796         if (tty_register_driver(ptm_driver))
 797                 panic("Couldn't register Unix98 ptm driver");
 798         if (tty_register_driver(pts_driver))
 799                 panic("Couldn't register Unix98 pts driver");
 800
 801         /* Now create the /dev/ptmx special device */
 802         tty_default_fops(&ptmx_fops);
 803         ptmx_fops.open = ptmx_open;
 804
 805         cdev_init(&ptmx_cdev, &ptmx_fops);
 806         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 807             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 808                 panic("Couldn't register /dev/ptmx driver");
 809         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 810 }
 811
 812 #else
 813 static inline void unix98_pty_init(void) { }
 814 #endif
 815
 816 static int __init pty_init(void)
 817 {
 818         legacy_pty_init();
 819         unix98_pty_init();
 820         return 0;
 821 }
 822 module_init(pty_init);