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 #include <linux/poll.h>
  28
  29
  30 #ifdef CONFIG_UNIX98_PTYS
  31 static struct tty_driver *ptm_driver;
  32 static struct tty_driver *pts_driver;
  33 static DEFINE_MUTEX(devpts_mutex);
  34 #endif
  35
  36 static void pty_close(struct tty_struct *tty, struct file *filp)
  37 {
  38         BUG_ON(!tty);
  39         if (tty->driver->subtype == PTY_TYPE_MASTER)
  40                 WARN_ON(tty->count > 1);
  41         else {
  42                 if (test_bit(TTY_IO_ERROR, &tty->flags))
  43                         return;
  44                 if (tty->count > 2)
  45                         return;
  46         }
  47         set_bit(TTY_IO_ERROR, &tty->flags);
  48         wake_up_interruptible(&tty->read_wait);
  49         wake_up_interruptible(&tty->write_wait);
  50         tty->packet = 0;
  51         /* Review - krefs on tty_link ?? */
  52         if (!tty->link)
  53                 return;
  54         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  55         wake_up_interruptible(&tty->link->read_wait);
  56         wake_up_interruptible(&tty->link->write_wait);
  57         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  58                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  59 #ifdef CONFIG_UNIX98_PTYS
  60                 if (tty->driver == ptm_driver) {
  61                         mutex_lock(&devpts_mutex);
  62                         if (tty->link->driver_data)
  63                                 devpts_pty_kill(tty->link->driver_data);
  64                         mutex_unlock(&devpts_mutex);
  65                 }
  66 #endif
  67                 tty_unlock(tty);
  68                 tty_vhangup(tty->link);
  69                 tty_lock(tty);
  70         }
  71 }
  72
  73 /*
  74  * The unthrottle routine is called by the line discipline to signal
  75  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  76  * flag is always set, to force the line discipline to always call the
  77  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  78  * characters in the queue.  This is necessary since each time this
  79  * happens, we need to wake up any sleeping processes that could be
  80  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  81  * for the pty buffer to be drained.
  82  */
  83 static void pty_unthrottle(struct tty_struct *tty)
  84 {
  85         tty_wakeup(tty->link);
  86         set_bit(TTY_THROTTLED, &tty->flags);
  87 }
  88
  89 /**
  90  *      pty_space       -       report space left for writing
  91  *      @to: tty we are writing into
  92  *
  93  *      Limit the buffer space used by ptys to 8k.
  94  */
  95
  96 static int pty_space(struct tty_struct *to)
  97 {
  98         int n = tty_buffer_space_avail(to->port);
  99         return min(n, 8192);
 100 }
 101
 102 /**
 103  *      pty_write               -       write to a pty
 104  *      @tty: the tty we write from
 105  *      @buf: kernel buffer of data
 106  *      @count: bytes to write
 107  *
 108  *      Our "hardware" write method. Data is coming from the ldisc which
 109  *      may be in a non sleeping state. We simply throw this at the other
 110  *      end of the link as if we were an IRQ handler receiving stuff for
 111  *      the other side of the pty/tty pair.
 112  */
 113
 114 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 115 {
 116         struct tty_struct *to = tty->link;
 117
 118         if (tty->stopped)
 119                 return 0;
 120
 121         if (c > 0) {
 122                 /* Stuff the data into the input queue of the other end */
 123                 c = tty_insert_flip_string(to->port, buf, c);
 124                 /* And shovel */
 125                 if (c)
 126                         tty_flip_buffer_push(to->port);
 127         }
 128         return c;
 129 }
 130
 131 /**
 132  *      pty_write_room  -       write space
 133  *      @tty: tty we are writing from
 134  *
 135  *      Report how many bytes the ldisc can send into the queue for
 136  *      the other device.
 137  */
 138
 139 static int pty_write_room(struct tty_struct *tty)
 140 {
 141         if (tty->stopped)
 142                 return 0;
 143         return pty_space(tty->link);
 144 }
 145
 146 /**
 147  *      pty_chars_in_buffer     -       characters currently in our tx queue
 148  *      @tty: our tty
 149  *
 150  *      Report how much we have in the transmit queue. As everything is
 151  *      instantly at the other end this is easy to implement.
 152  */
 153
 154 static int pty_chars_in_buffer(struct tty_struct *tty)
 155 {
 156         return 0;
 157 }
 158
 159 /* Set the lock flag on a pty */
 160 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 161 {
 162         int val;
 163         if (get_user(val, arg))
 164                 return -EFAULT;
 165         if (val)
 166                 set_bit(TTY_PTY_LOCK, &tty->flags);
 167         else
 168                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 169         return 0;
 170 }
 171
 172 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 173 {
 174         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 175         return put_user(locked, arg);
 176 }
 177
 178 /* Set the packet mode on a pty */
 179 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 180 {
 181         int pktmode;
 182
 183         if (get_user(pktmode, arg))
 184                 return -EFAULT;
 185
 186         spin_lock_irq(&tty->ctrl_lock);
 187         if (pktmode) {
 188                 if (!tty->packet) {
 189                         tty->packet = 1;
 190                         tty->link->ctrl_status = 0;
 191                 }
 192         } else
 193                 tty->packet = 0;
 194         spin_unlock_irq(&tty->ctrl_lock);
 195
 196         return 0;
 197 }
 198
 199 /* Get the packet mode of a pty */
 200 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 201 {
 202         int pktmode = tty->packet;
 203         return put_user(pktmode, arg);
 204 }
 205
 206 /* Send a signal to the slave */
 207 static int pty_signal(struct tty_struct *tty, int sig)
 208 {
 209         struct pid *pgrp;
 210
 211         if (tty->link) {
 212                 pgrp = tty_get_pgrp(tty->link);
 213                 if (pgrp)
 214                         kill_pgrp(pgrp, sig, 1);
 215                 put_pid(pgrp);
 216         }
 217         return 0;
 218 }
 219
 220 static void pty_flush_buffer(struct tty_struct *tty)
 221 {
 222         struct tty_struct *to = tty->link;
 223
 224         if (!to)
 225                 return;
 226         /* tty_buffer_flush(to); FIXME */
 227         if (to->packet) {
 228                 spin_lock_irq(&tty->ctrl_lock);
 229                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 230                 wake_up_interruptible(&to->read_wait);
 231                 spin_unlock_irq(&tty->ctrl_lock);
 232         }
 233 }
 234
 235 static int pty_open(struct tty_struct *tty, struct file *filp)
 236 {
 237         if (!tty || !tty->link)
 238                 return -ENODEV;
 239
 240         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 241                 goto out;
 242         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 243                 goto out;
 244         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 245                 goto out;
 246
 247         clear_bit(TTY_IO_ERROR, &tty->flags);
 248         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 249         set_bit(TTY_THROTTLED, &tty->flags);
 250         return 0;
 251
 252 out:
 253         set_bit(TTY_IO_ERROR, &tty->flags);
 254         return -EIO;
 255 }
 256
 257 static void pty_set_termios(struct tty_struct *tty,
 258                                         struct ktermios *old_termios)
 259 {
 260         /* See if packet mode change of state. */
 261         if (tty->link && tty->link->packet) {
 262                 int extproc = (old_termios->c_lflag & EXTPROC) |
 263                                 (tty->termios.c_lflag & EXTPROC);
 264                 int old_flow = ((old_termios->c_iflag & IXON) &&
 265                                 (old_termios->c_cc[VSTOP] == '\023') &&
 266                                 (old_termios->c_cc[VSTART] == '\021'));
 267                 int new_flow = (I_IXON(tty) &&
 268                                 STOP_CHAR(tty) == '\023' &&
 269                                 START_CHAR(tty) == '\021');
 270                 if ((old_flow != new_flow) || extproc) {
 271                         spin_lock_irq(&tty->ctrl_lock);
 272                         if (old_flow != new_flow) {
 273                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 274                                 if (new_flow)
 275                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 276                                 else
 277                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 278                         }
 279                         if (extproc)
 280                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 281                         spin_unlock_irq(&tty->ctrl_lock);
 282                         wake_up_interruptible(&tty->link->read_wait);
 283                 }
 284         }
 285
 286         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 287         tty->termios.c_cflag |= (CS8 | CREAD);
 288 }
 289
 290 /**
 291  *      pty_do_resize           -       resize event
 292  *      @tty: tty being resized
 293  *      @ws: window size being set.
 294  *
 295  *      Update the termios variables and send the necessary signals to
 296  *      peform a terminal resize correctly
 297  */
 298
 299 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 300 {
 301         struct pid *pgrp, *rpgrp;
 302         struct tty_struct *pty = tty->link;
 303
 304         /* For a PTY we need to lock the tty side */
 305         mutex_lock(&tty->winsize_mutex);
 306         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 307                 goto done;
 308
 309         /* Signal the foreground process group of both ptys */
 310         pgrp = tty_get_pgrp(tty);
 311         rpgrp = tty_get_pgrp(pty);
 312
 313         if (pgrp)
 314                 kill_pgrp(pgrp, SIGWINCH, 1);
 315         if (rpgrp != pgrp && rpgrp)
 316                 kill_pgrp(rpgrp, SIGWINCH, 1);
 317
 318         put_pid(pgrp);
 319         put_pid(rpgrp);
 320
 321         tty->winsize = *ws;
 322         pty->winsize = *ws;     /* Never used so will go away soon */
 323 done:
 324         mutex_unlock(&tty->winsize_mutex);
 325         return 0;
 326 }
 327
 328 /**
 329  *      pty_start - start() handler
 330  *      pty_stop  - stop() handler
 331  *      @tty: tty being flow-controlled
 332  *
 333  *      Propagates the TIOCPKT status to the master pty.
 334  *
 335  *      NB: only the master pty can be in packet mode so only the slave
 336  *          needs start()/stop() handlers
 337  */
 338 static void pty_start(struct tty_struct *tty)
 339 {
 340         unsigned long flags;
 341
 342         spin_lock_irqsave(&tty->ctrl_lock, flags);
 343         if (tty->link && tty->link->packet) {
 344                 tty->ctrl_status &= ~TIOCPKT_STOP;
 345                 tty->ctrl_status |= TIOCPKT_START;
 346                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 347         }
 348         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 349 }
 350
 351 static void pty_stop(struct tty_struct *tty)
 352 {
 353         unsigned long flags;
 354
 355         spin_lock_irqsave(&tty->ctrl_lock, flags);
 356         if (tty->link && tty->link->packet) {
 357                 tty->ctrl_status &= ~TIOCPKT_START;
 358                 tty->ctrl_status |= TIOCPKT_STOP;
 359                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 360         }
 361         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 362 }
 363
 364 /**
 365  *      pty_common_install              -       set up the pty pair
 366  *      @driver: the pty driver
 367  *      @tty: the tty being instantiated
 368  *      @legacy: true if this is BSD style
 369  *
 370  *      Perform the initial set up for the tty/pty pair. Called from the
 371  *      tty layer when the port is first opened.
 372  *
 373  *      Locking: the caller must hold the tty_mutex
 374  */
 375 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 376                 bool legacy)
 377 {
 378         struct tty_struct *o_tty;
 379         struct tty_port *ports[2];
 380         int idx = tty->index;
 381         int retval = -ENOMEM;
 382
 383         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 384         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 385         if (!ports[0] || !ports[1])
 386                 goto err;
 387         if (!try_module_get(driver->other->owner)) {
 388                 /* This cannot in fact currently happen */
 389                 goto err;
 390         }
 391         o_tty = alloc_tty_struct(driver->other, idx);
 392         if (!o_tty)
 393                 goto err_put_module;
 394
 395         if (legacy) {
 396                 /* We always use new tty termios data so we can do this
 397                    the easy way .. */
 398                 retval = tty_init_termios(tty);
 399                 if (retval)
 400                         goto err_deinit_tty;
 401
 402                 retval = tty_init_termios(o_tty);
 403                 if (retval)
 404                         goto err_free_termios;
 405
 406                 driver->other->ttys[idx] = o_tty;
 407                 driver->ttys[idx] = tty;
 408         } else {
 409                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 410                 tty->termios = driver->init_termios;
 411                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 412                 o_tty->termios = driver->other->init_termios;
 413         }
 414
 415         /*
 416          * Everything allocated ... set up the o_tty structure.
 417          */
 418         tty_driver_kref_get(driver->other);
 419         if (driver->subtype == PTY_TYPE_MASTER)
 420                 o_tty->count++;
 421         /* Establish the links in both directions */
 422         tty->link   = o_tty;
 423         o_tty->link = tty;
 424         tty_port_init(ports[0]);
 425         tty_port_init(ports[1]);
 426         o_tty->port = ports[0];
 427         tty->port = ports[1];
 428         o_tty->port->itty = o_tty;
 429
 430         tty_driver_kref_get(driver);
 431         tty->count++;
 432         return 0;
 433 err_free_termios:
 434         if (legacy)
 435                 tty_free_termios(tty);
 436 err_deinit_tty:
 437         deinitialize_tty_struct(o_tty);
 438         free_tty_struct(o_tty);
 439 err_put_module:
 440         module_put(driver->other->owner);
 441 err:
 442         kfree(ports[0]);
 443         kfree(ports[1]);
 444         return retval;
 445 }
 446
 447 static void pty_cleanup(struct tty_struct *tty)
 448 {
 449         tty_port_put(tty->port);
 450 }
 451
 452 /* Traditional BSD devices */
 453 #ifdef CONFIG_LEGACY_PTYS
 454
 455 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 456 {
 457         return pty_common_install(driver, tty, true);
 458 }
 459
 460 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 461 {
 462         struct tty_struct *pair = tty->link;
 463         driver->ttys[tty->index] = NULL;
 464         if (pair)
 465                 pair->driver->ttys[pair->index] = NULL;
 466 }
 467
 468 static int pty_bsd_ioctl(struct tty_struct *tty,
 469                          unsigned int cmd, unsigned long arg)
 470 {
 471         switch (cmd) {
 472         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 473                 return pty_set_lock(tty, (int __user *) arg);
 474         case TIOCGPTLCK: /* Get PT Lock status */
 475                 return pty_get_lock(tty, (int __user *)arg);
 476         case TIOCPKT: /* Set PT packet mode */
 477                 return pty_set_pktmode(tty, (int __user *)arg);
 478         case TIOCGPKT: /* Get PT packet mode */
 479                 return pty_get_pktmode(tty, (int __user *)arg);
 480         case TIOCSIG:    /* Send signal to other side of pty */
 481                 return pty_signal(tty, (int) arg);
 482         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 483                 return -EINVAL;
 484         }
 485         return -ENOIOCTLCMD;
 486 }
 487
 488 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 489 module_param(legacy_count, int, 0);
 490
 491 /*
 492  * The master side of a pty can do TIOCSPTLCK and thus
 493  * has pty_bsd_ioctl.
 494  */
 495 static const struct tty_operations master_pty_ops_bsd = {
 496         .install = pty_install,
 497         .open = pty_open,
 498         .close = pty_close,
 499         .write = pty_write,
 500         .write_room = pty_write_room,
 501         .flush_buffer = pty_flush_buffer,
 502         .chars_in_buffer = pty_chars_in_buffer,
 503         .unthrottle = pty_unthrottle,
 504         .ioctl = pty_bsd_ioctl,
 505         .cleanup = pty_cleanup,
 506         .resize = pty_resize,
 507         .remove = pty_remove
 508 };
 509
 510 static const struct tty_operations slave_pty_ops_bsd = {
 511         .install = pty_install,
 512         .open = pty_open,
 513         .close = pty_close,
 514         .write = pty_write,
 515         .write_room = pty_write_room,
 516         .flush_buffer = pty_flush_buffer,
 517         .chars_in_buffer = pty_chars_in_buffer,
 518         .unthrottle = pty_unthrottle,
 519         .set_termios = pty_set_termios,
 520         .cleanup = pty_cleanup,
 521         .resize = pty_resize,
 522         .start = pty_start,
 523         .stop = pty_stop,
 524         .remove = pty_remove
 525 };
 526
 527 static void __init legacy_pty_init(void)
 528 {
 529         struct tty_driver *pty_driver, *pty_slave_driver;
 530
 531         if (legacy_count <= 0)
 532                 return;
 533
 534         pty_driver = tty_alloc_driver(legacy_count,
 535                         TTY_DRIVER_RESET_TERMIOS |
 536                         TTY_DRIVER_REAL_RAW |
 537                         TTY_DRIVER_DYNAMIC_ALLOC);
 538         if (IS_ERR(pty_driver))
 539                 panic("Couldn't allocate pty driver");
 540
 541         pty_slave_driver = tty_alloc_driver(legacy_count,
 542                         TTY_DRIVER_RESET_TERMIOS |
 543                         TTY_DRIVER_REAL_RAW |
 544                         TTY_DRIVER_DYNAMIC_ALLOC);
 545         if (IS_ERR(pty_slave_driver))
 546                 panic("Couldn't allocate pty slave driver");
 547
 548         pty_driver->driver_name = "pty_master";
 549         pty_driver->name = "pty";
 550         pty_driver->major = PTY_MASTER_MAJOR;
 551         pty_driver->minor_start = 0;
 552         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 553         pty_driver->subtype = PTY_TYPE_MASTER;
 554         pty_driver->init_termios = tty_std_termios;
 555         pty_driver->init_termios.c_iflag = 0;
 556         pty_driver->init_termios.c_oflag = 0;
 557         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 558         pty_driver->init_termios.c_lflag = 0;
 559         pty_driver->init_termios.c_ispeed = 38400;
 560         pty_driver->init_termios.c_ospeed = 38400;
 561         pty_driver->other = pty_slave_driver;
 562         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 563
 564         pty_slave_driver->driver_name = "pty_slave";
 565         pty_slave_driver->name = "ttyp";
 566         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 567         pty_slave_driver->minor_start = 0;
 568         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 569         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 570         pty_slave_driver->init_termios = tty_std_termios;
 571         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 572         pty_slave_driver->init_termios.c_ispeed = 38400;
 573         pty_slave_driver->init_termios.c_ospeed = 38400;
 574         pty_slave_driver->other = pty_driver;
 575         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 576
 577         if (tty_register_driver(pty_driver))
 578                 panic("Couldn't register pty driver");
 579         if (tty_register_driver(pty_slave_driver))
 580                 panic("Couldn't register pty slave driver");
 581 }
 582 #else
 583 static inline void legacy_pty_init(void) { }
 584 #endif
 585
 586 /* Unix98 devices */
 587 #ifdef CONFIG_UNIX98_PTYS
 588
 589 static struct cdev ptmx_cdev;
 590
 591 static int pty_unix98_ioctl(struct tty_struct *tty,
 592                             unsigned int cmd, unsigned long arg)
 593 {
 594         switch (cmd) {
 595         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 596                 return pty_set_lock(tty, (int __user *)arg);
 597         case TIOCGPTLCK: /* Get PT Lock status */
 598                 return pty_get_lock(tty, (int __user *)arg);
 599         case TIOCPKT: /* Set PT packet mode */
 600                 return pty_set_pktmode(tty, (int __user *)arg);
 601         case TIOCGPKT: /* Get PT packet mode */
 602                 return pty_get_pktmode(tty, (int __user *)arg);
 603         case TIOCGPTN: /* Get PT Number */
 604                 return put_user(tty->index, (unsigned int __user *)arg);
 605         case TIOCSIG:    /* Send signal to other side of pty */
 606                 return pty_signal(tty, (int) arg);
 607         }
 608
 609         return -ENOIOCTLCMD;
 610 }
 611
 612 /**
 613  *      ptm_unix98_lookup       -       find a pty master
 614  *      @driver: ptm driver
 615  *      @idx: tty index
 616  *
 617  *      Look up a pty master device. Called under the tty_mutex for now.
 618  *      This provides our locking.
 619  */
 620
 621 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 622                 struct inode *ptm_inode, int idx)
 623 {
 624         /* Master must be open via /dev/ptmx */
 625         return ERR_PTR(-EIO);
 626 }
 627
 628 /**
 629  *      pts_unix98_lookup       -       find a pty slave
 630  *      @driver: pts driver
 631  *      @idx: tty index
 632  *
 633  *      Look up a pty master device. Called under the tty_mutex for now.
 634  *      This provides our locking for the tty pointer.
 635  */
 636
 637 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 638                 struct inode *pts_inode, int idx)
 639 {
 640         struct tty_struct *tty;
 641
 642         mutex_lock(&devpts_mutex);
 643         tty = devpts_get_priv(pts_inode);
 644         mutex_unlock(&devpts_mutex);
 645         /* Master must be open before slave */
 646         if (!tty)
 647                 return ERR_PTR(-EIO);
 648         return tty;
 649 }
 650
 651 /* We have no need to install and remove our tty objects as devpts does all
 652    the work for us */
 653
 654 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 655 {
 656         return pty_common_install(driver, tty, false);
 657 }
 658
 659 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 660 {
 661 }
 662
 663 /* this is called once with whichever end is closed last */
 664 static void pty_unix98_shutdown(struct tty_struct *tty)
 665 {
 666         devpts_kill_index(tty->driver_data, tty->index);
 667 }
 668
 669 static const struct tty_operations ptm_unix98_ops = {
 670         .lookup = ptm_unix98_lookup,
 671         .install = pty_unix98_install,
 672         .remove = pty_unix98_remove,
 673         .open = pty_open,
 674         .close = pty_close,
 675         .write = pty_write,
 676         .write_room = pty_write_room,
 677         .flush_buffer = pty_flush_buffer,
 678         .chars_in_buffer = pty_chars_in_buffer,
 679         .unthrottle = pty_unthrottle,
 680         .ioctl = pty_unix98_ioctl,
 681         .resize = pty_resize,
 682         .shutdown = pty_unix98_shutdown,
 683         .cleanup = pty_cleanup
 684 };
 685
 686 static const struct tty_operations pty_unix98_ops = {
 687         .lookup = pts_unix98_lookup,
 688         .install = pty_unix98_install,
 689         .remove = pty_unix98_remove,
 690         .open = pty_open,
 691         .close = pty_close,
 692         .write = pty_write,
 693         .write_room = pty_write_room,
 694         .flush_buffer = pty_flush_buffer,
 695         .chars_in_buffer = pty_chars_in_buffer,
 696         .unthrottle = pty_unthrottle,
 697         .set_termios = pty_set_termios,
 698         .start = pty_start,
 699         .stop = pty_stop,
 700         .shutdown = pty_unix98_shutdown,
 701         .cleanup = pty_cleanup,
 702 };
 703
 704 /**
 705  *      ptmx_open               -       open a unix 98 pty master
 706  *      @inode: inode of device file
 707  *      @filp: file pointer to tty
 708  *
 709  *      Allocate a unix98 pty master device from the ptmx driver.
 710  *
 711  *      Locking: tty_mutex protects the init_dev work. tty->count should
 712  *              protect the rest.
 713  *              allocated_ptys_lock handles the list of free pty numbers
 714  */
 715
 716 static int ptmx_open(struct inode *inode, struct file *filp)
 717 {
 718         struct tty_struct *tty;
 719         struct inode *slave_inode;
 720         int retval;
 721         int index;
 722
 723         nonseekable_open(inode, filp);
 724
 725         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 726         filp->f_mode |= FMODE_NONOTIFY;
 727
 728         retval = tty_alloc_file(filp);
 729         if (retval)
 730                 return retval;
 731
 732         /* find a device that is not in use. */
 733         mutex_lock(&devpts_mutex);
 734         index = devpts_new_index(inode);
 735         if (index < 0) {
 736                 retval = index;
 737                 mutex_unlock(&devpts_mutex);
 738                 goto err_file;
 739         }
 740
 741         mutex_unlock(&devpts_mutex);
 742
 743         mutex_lock(&tty_mutex);
 744         tty = tty_init_dev(ptm_driver, index);
 745
 746         if (IS_ERR(tty)) {
 747                 retval = PTR_ERR(tty);
 748                 goto out;
 749         }
 750
 751         /* The tty returned here is locked so we can safely
 752            drop the mutex */
 753         mutex_unlock(&tty_mutex);
 754
 755         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 756         tty->driver_data = inode;
 757
 758         tty_add_file(tty, filp);
 759
 760         slave_inode = devpts_pty_new(inode,
 761                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 762                         tty->link);
 763         if (IS_ERR(slave_inode)) {
 764                 retval = PTR_ERR(slave_inode);
 765                 goto err_release;
 766         }
 767         tty->link->driver_data = slave_inode;
 768
 769         retval = ptm_driver->ops->open(tty, filp);
 770         if (retval)
 771                 goto err_release;
 772
 773         tty_unlock(tty);
 774         return 0;
 775 err_release:
 776         tty_unlock(tty);
 777         tty_release(inode, filp);
 778         return retval;
 779 out:
 780         mutex_unlock(&tty_mutex);
 781         devpts_kill_index(inode, index);
 782 err_file:
 783         tty_free_file(filp);
 784         return retval;
 785 }
 786
 787 static struct file_operations ptmx_fops;
 788
 789 static void __init unix98_pty_init(void)
 790 {
 791         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 792                         TTY_DRIVER_RESET_TERMIOS |
 793                         TTY_DRIVER_REAL_RAW |
 794                         TTY_DRIVER_DYNAMIC_DEV |
 795                         TTY_DRIVER_DEVPTS_MEM |
 796                         TTY_DRIVER_DYNAMIC_ALLOC);
 797         if (IS_ERR(ptm_driver))
 798                 panic("Couldn't allocate Unix98 ptm driver");
 799         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 800                         TTY_DRIVER_RESET_TERMIOS |
 801                         TTY_DRIVER_REAL_RAW |
 802                         TTY_DRIVER_DYNAMIC_DEV |
 803                         TTY_DRIVER_DEVPTS_MEM |
 804                         TTY_DRIVER_DYNAMIC_ALLOC);
 805         if (IS_ERR(pts_driver))
 806                 panic("Couldn't allocate Unix98 pts driver");
 807
 808         ptm_driver->driver_name = "pty_master";
 809         ptm_driver->name = "ptm";
 810         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 811         ptm_driver->minor_start = 0;
 812         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 813         ptm_driver->subtype = PTY_TYPE_MASTER;
 814         ptm_driver->init_termios = tty_std_termios;
 815         ptm_driver->init_termios.c_iflag = 0;
 816         ptm_driver->init_termios.c_oflag = 0;
 817         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 818         ptm_driver->init_termios.c_lflag = 0;
 819         ptm_driver->init_termios.c_ispeed = 38400;
 820         ptm_driver->init_termios.c_ospeed = 38400;
 821         ptm_driver->other = pts_driver;
 822         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 823
 824         pts_driver->driver_name = "pty_slave";
 825         pts_driver->name = "pts";
 826         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 827         pts_driver->minor_start = 0;
 828         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 829         pts_driver->subtype = PTY_TYPE_SLAVE;
 830         pts_driver->init_termios = tty_std_termios;
 831         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 832         pts_driver->init_termios.c_ispeed = 38400;
 833         pts_driver->init_termios.c_ospeed = 38400;
 834         pts_driver->other = ptm_driver;
 835         tty_set_operations(pts_driver, &pty_unix98_ops);
 836
 837         if (tty_register_driver(ptm_driver))
 838                 panic("Couldn't register Unix98 ptm driver");
 839         if (tty_register_driver(pts_driver))
 840                 panic("Couldn't register Unix98 pts driver");
 841
 842         /* Now create the /dev/ptmx special device */
 843         tty_default_fops(&ptmx_fops);
 844         ptmx_fops.open = ptmx_open;
 845
 846         cdev_init(&ptmx_cdev, &ptmx_fops);
 847         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 848             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 849                 panic("Couldn't register /dev/ptmx driver");
 850         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 851 }
 852
 853 #else
 854 static inline void unix98_pty_init(void) { }
 855 #endif
 856
 857 static int __init pty_init(void)
 858 {
 859         legacy_pty_init();
 860         unix98_pty_init();
 861         return 0;
 862 }
 863 module_init(pty_init);