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         spin_lock_irq(&tty->ctrl_lock);
  51         tty->packet = 0;
  52         spin_unlock_irq(&tty->ctrl_lock);
  53         /* Review - krefs on tty_link ?? */
  54         if (!tty->link)
  55                 return;
  56         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  57         wake_up_interruptible(&tty->link->read_wait);
  58         wake_up_interruptible(&tty->link->write_wait);
  59         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  60                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  61 #ifdef CONFIG_UNIX98_PTYS
  62                 if (tty->driver == ptm_driver) {
  63                         mutex_lock(&devpts_mutex);
  64                         if (tty->link->driver_data)
  65                                 devpts_pty_kill(tty->link->driver_data);
  66                         mutex_unlock(&devpts_mutex);
  67                 }
  68 #endif
  69                 tty_unlock(tty);
  70                 tty_vhangup(tty->link);
  71                 tty_lock(tty);
  72         }
  73 }
  74
  75 /*
  76  * The unthrottle routine is called by the line discipline to signal
  77  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  78  * flag is always set, to force the line discipline to always call the
  79  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  80  * characters in the queue.  This is necessary since each time this
  81  * happens, we need to wake up any sleeping processes that could be
  82  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  83  * for the pty buffer to be drained.
  84  */
  85 static void pty_unthrottle(struct tty_struct *tty)
  86 {
  87         tty_wakeup(tty->link);
  88         set_bit(TTY_THROTTLED, &tty->flags);
  89 }
  90
  91 /**
  92  *      pty_space       -       report space left for writing
  93  *      @to: tty we are writing into
  94  *
  95  *      Limit the buffer space used by ptys to 8k.
  96  */
  97
  98 static int pty_space(struct tty_struct *to)
  99 {
 100         int n = tty_buffer_space_avail(to->port);
 101         return min(n, 8192);
 102 }
 103
 104 /**
 105  *      pty_write               -       write to a pty
 106  *      @tty: the tty we write from
 107  *      @buf: kernel buffer of data
 108  *      @count: bytes to write
 109  *
 110  *      Our "hardware" write method. Data is coming from the ldisc which
 111  *      may be in a non sleeping state. We simply throw this at the other
 112  *      end of the link as if we were an IRQ handler receiving stuff for
 113  *      the other side of the pty/tty pair.
 114  */
 115
 116 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 117 {
 118         struct tty_struct *to = tty->link;
 119
 120         if (tty->stopped)
 121                 return 0;
 122
 123         if (c > 0) {
 124                 /* Stuff the data into the input queue of the other end */
 125                 c = tty_insert_flip_string(to->port, buf, c);
 126                 /* And shovel */
 127                 if (c)
 128                         tty_flip_buffer_push(to->port);
 129         }
 130         return c;
 131 }
 132
 133 /**
 134  *      pty_write_room  -       write space
 135  *      @tty: tty we are writing from
 136  *
 137  *      Report how many bytes the ldisc can send into the queue for
 138  *      the other device.
 139  */
 140
 141 static int pty_write_room(struct tty_struct *tty)
 142 {
 143         if (tty->stopped)
 144                 return 0;
 145         return pty_space(tty->link);
 146 }
 147
 148 /**
 149  *      pty_chars_in_buffer     -       characters currently in our tx queue
 150  *      @tty: our tty
 151  *
 152  *      Report how much we have in the transmit queue. As everything is
 153  *      instantly at the other end this is easy to implement.
 154  */
 155
 156 static int pty_chars_in_buffer(struct tty_struct *tty)
 157 {
 158         return 0;
 159 }
 160
 161 /* Set the lock flag on a pty */
 162 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 163 {
 164         int val;
 165         if (get_user(val, arg))
 166                 return -EFAULT;
 167         if (val)
 168                 set_bit(TTY_PTY_LOCK, &tty->flags);
 169         else
 170                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 171         return 0;
 172 }
 173
 174 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 175 {
 176         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 177         return put_user(locked, arg);
 178 }
 179
 180 /* Set the packet mode on a pty */
 181 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 182 {
 183         int pktmode;
 184
 185         if (get_user(pktmode, arg))
 186                 return -EFAULT;
 187
 188         spin_lock_irq(&tty->ctrl_lock);
 189         if (pktmode) {
 190                 if (!tty->packet) {
 191                         tty->link->ctrl_status = 0;
 192                         smp_mb();
 193                         tty->packet = 1;
 194                 }
 195         } else
 196                 tty->packet = 0;
 197         spin_unlock_irq(&tty->ctrl_lock);
 198
 199         return 0;
 200 }
 201
 202 /* Get the packet mode of a pty */
 203 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 204 {
 205         int pktmode = tty->packet;
 206         return put_user(pktmode, arg);
 207 }
 208
 209 /* Send a signal to the slave */
 210 static int pty_signal(struct tty_struct *tty, int sig)
 211 {
 212         struct pid *pgrp;
 213
 214         if (tty->link) {
 215                 pgrp = tty_get_pgrp(tty->link);
 216                 if (pgrp)
 217                         kill_pgrp(pgrp, sig, 1);
 218                 put_pid(pgrp);
 219         }
 220         return 0;
 221 }
 222
 223 static void pty_flush_buffer(struct tty_struct *tty)
 224 {
 225         struct tty_struct *to = tty->link;
 226
 227         if (!to)
 228                 return;
 229         /* tty_buffer_flush(to); FIXME */
 230         if (to->packet) {
 231                 spin_lock_irq(&tty->ctrl_lock);
 232                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 233                 wake_up_interruptible(&to->read_wait);
 234                 spin_unlock_irq(&tty->ctrl_lock);
 235         }
 236 }
 237
 238 static int pty_open(struct tty_struct *tty, struct file *filp)
 239 {
 240         if (!tty || !tty->link)
 241                 return -ENODEV;
 242
 243         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 244                 goto out;
 245         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 246                 goto out;
 247         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 248                 goto out;
 249
 250         clear_bit(TTY_IO_ERROR, &tty->flags);
 251         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 252         set_bit(TTY_THROTTLED, &tty->flags);
 253         return 0;
 254
 255 out:
 256         set_bit(TTY_IO_ERROR, &tty->flags);
 257         return -EIO;
 258 }
 259
 260 static void pty_set_termios(struct tty_struct *tty,
 261                                         struct ktermios *old_termios)
 262 {
 263         /* See if packet mode change of state. */
 264         if (tty->link && tty->link->packet) {
 265                 int extproc = (old_termios->c_lflag & EXTPROC) |
 266                                 (tty->termios.c_lflag & EXTPROC);
 267                 int old_flow = ((old_termios->c_iflag & IXON) &&
 268                                 (old_termios->c_cc[VSTOP] == '\023') &&
 269                                 (old_termios->c_cc[VSTART] == '\021'));
 270                 int new_flow = (I_IXON(tty) &&
 271                                 STOP_CHAR(tty) == '\023' &&
 272                                 START_CHAR(tty) == '\021');
 273                 if ((old_flow != new_flow) || extproc) {
 274                         spin_lock_irq(&tty->ctrl_lock);
 275                         if (old_flow != new_flow) {
 276                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 277                                 if (new_flow)
 278                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 279                                 else
 280                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 281                         }
 282                         if (extproc)
 283                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 284                         spin_unlock_irq(&tty->ctrl_lock);
 285                         wake_up_interruptible(&tty->link->read_wait);
 286                 }
 287         }
 288
 289         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 290         tty->termios.c_cflag |= (CS8 | CREAD);
 291 }
 292
 293 /**
 294  *      pty_do_resize           -       resize event
 295  *      @tty: tty being resized
 296  *      @ws: window size being set.
 297  *
 298  *      Update the termios variables and send the necessary signals to
 299  *      peform a terminal resize correctly
 300  */
 301
 302 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 303 {
 304         struct pid *pgrp, *rpgrp;
 305         struct tty_struct *pty = tty->link;
 306
 307         /* For a PTY we need to lock the tty side */
 308         mutex_lock(&tty->winsize_mutex);
 309         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 310                 goto done;
 311
 312         /* Signal the foreground process group of both ptys */
 313         pgrp = tty_get_pgrp(tty);
 314         rpgrp = tty_get_pgrp(pty);
 315
 316         if (pgrp)
 317                 kill_pgrp(pgrp, SIGWINCH, 1);
 318         if (rpgrp != pgrp && rpgrp)
 319                 kill_pgrp(rpgrp, SIGWINCH, 1);
 320
 321         put_pid(pgrp);
 322         put_pid(rpgrp);
 323
 324         tty->winsize = *ws;
 325         pty->winsize = *ws;     /* Never used so will go away soon */
 326 done:
 327         mutex_unlock(&tty->winsize_mutex);
 328         return 0;
 329 }
 330
 331 /**
 332  *      pty_start - start() handler
 333  *      pty_stop  - stop() handler
 334  *      @tty: tty being flow-controlled
 335  *
 336  *      Propagates the TIOCPKT status to the master pty.
 337  *
 338  *      NB: only the master pty can be in packet mode so only the slave
 339  *          needs start()/stop() handlers
 340  */
 341 static void pty_start(struct tty_struct *tty)
 342 {
 343         unsigned long flags;
 344
 345         if (tty->link && tty->link->packet) {
 346                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 347                 tty->ctrl_status &= ~TIOCPKT_STOP;
 348                 tty->ctrl_status |= TIOCPKT_START;
 349                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 350                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 351         }
 352 }
 353
 354 static void pty_stop(struct tty_struct *tty)
 355 {
 356         unsigned long flags;
 357
 358         if (tty->link && tty->link->packet) {
 359                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 360                 tty->ctrl_status &= ~TIOCPKT_START;
 361                 tty->ctrl_status |= TIOCPKT_STOP;
 362                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 363                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 364         }
 365 }
 366
 367 /**
 368  *      pty_common_install              -       set up the pty pair
 369  *      @driver: the pty driver
 370  *      @tty: the tty being instantiated
 371  *      @legacy: true if this is BSD style
 372  *
 373  *      Perform the initial set up for the tty/pty pair. Called from the
 374  *      tty layer when the port is first opened.
 375  *
 376  *      Locking: the caller must hold the tty_mutex
 377  */
 378 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 379                 bool legacy)
 380 {
 381         struct tty_struct *o_tty;
 382         struct tty_port *ports[2];
 383         int idx = tty->index;
 384         int retval = -ENOMEM;
 385
 386         /* Opening the slave first has always returned -EIO */
 387         if (driver->subtype != PTY_TYPE_MASTER)
 388                 return -EIO;
 389
 390         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 391         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 392         if (!ports[0] || !ports[1])
 393                 goto err;
 394         if (!try_module_get(driver->other->owner)) {
 395                 /* This cannot in fact currently happen */
 396                 goto err;
 397         }
 398         o_tty = alloc_tty_struct(driver->other, idx);
 399         if (!o_tty)
 400                 goto err_put_module;
 401
 402         if (legacy) {
 403                 /* We always use new tty termios data so we can do this
 404                    the easy way .. */
 405                 retval = tty_init_termios(tty);
 406                 if (retval)
 407                         goto err_deinit_tty;
 408
 409                 retval = tty_init_termios(o_tty);
 410                 if (retval)
 411                         goto err_free_termios;
 412
 413                 driver->other->ttys[idx] = o_tty;
 414                 driver->ttys[idx] = tty;
 415         } else {
 416                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 417                 tty->termios = driver->init_termios;
 418                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 419                 o_tty->termios = driver->other->init_termios;
 420         }
 421
 422         /*
 423          * Everything allocated ... set up the o_tty structure.
 424          */
 425         tty_driver_kref_get(driver->other);
 426         /* Establish the links in both directions */
 427         tty->link   = o_tty;
 428         o_tty->link = tty;
 429         tty_port_init(ports[0]);
 430         tty_port_init(ports[1]);
 431         o_tty->port = ports[0];
 432         tty->port = ports[1];
 433         o_tty->port->itty = o_tty;
 434
 435         tty_driver_kref_get(driver);
 436         tty->count++;
 437         o_tty->count++;
 438         return 0;
 439 err_free_termios:
 440         if (legacy)
 441                 tty_free_termios(tty);
 442 err_deinit_tty:
 443         deinitialize_tty_struct(o_tty);
 444         free_tty_struct(o_tty);
 445 err_put_module:
 446         module_put(driver->other->owner);
 447 err:
 448         kfree(ports[0]);
 449         kfree(ports[1]);
 450         return retval;
 451 }
 452
 453 static void pty_cleanup(struct tty_struct *tty)
 454 {
 455         tty_port_put(tty->port);
 456 }
 457
 458 /* Traditional BSD devices */
 459 #ifdef CONFIG_LEGACY_PTYS
 460
 461 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 462 {
 463         return pty_common_install(driver, tty, true);
 464 }
 465
 466 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 467 {
 468         struct tty_struct *pair = tty->link;
 469         driver->ttys[tty->index] = NULL;
 470         if (pair)
 471                 pair->driver->ttys[pair->index] = NULL;
 472 }
 473
 474 static int pty_bsd_ioctl(struct tty_struct *tty,
 475                          unsigned int cmd, unsigned long arg)
 476 {
 477         switch (cmd) {
 478         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 479                 return pty_set_lock(tty, (int __user *) arg);
 480         case TIOCGPTLCK: /* Get PT Lock status */
 481                 return pty_get_lock(tty, (int __user *)arg);
 482         case TIOCPKT: /* Set PT packet mode */
 483                 return pty_set_pktmode(tty, (int __user *)arg);
 484         case TIOCGPKT: /* Get PT packet mode */
 485                 return pty_get_pktmode(tty, (int __user *)arg);
 486         case TIOCSIG:    /* Send signal to other side of pty */
 487                 return pty_signal(tty, (int) arg);
 488         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 489                 return -EINVAL;
 490         }
 491         return -ENOIOCTLCMD;
 492 }
 493
 494 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 495 module_param(legacy_count, int, 0);
 496
 497 /*
 498  * The master side of a pty can do TIOCSPTLCK and thus
 499  * has pty_bsd_ioctl.
 500  */
 501 static const struct tty_operations master_pty_ops_bsd = {
 502         .install = pty_install,
 503         .open = pty_open,
 504         .close = pty_close,
 505         .write = pty_write,
 506         .write_room = pty_write_room,
 507         .flush_buffer = pty_flush_buffer,
 508         .chars_in_buffer = pty_chars_in_buffer,
 509         .unthrottle = pty_unthrottle,
 510         .ioctl = pty_bsd_ioctl,
 511         .cleanup = pty_cleanup,
 512         .resize = pty_resize,
 513         .remove = pty_remove
 514 };
 515
 516 static const struct tty_operations slave_pty_ops_bsd = {
 517         .install = pty_install,
 518         .open = pty_open,
 519         .close = pty_close,
 520         .write = pty_write,
 521         .write_room = pty_write_room,
 522         .flush_buffer = pty_flush_buffer,
 523         .chars_in_buffer = pty_chars_in_buffer,
 524         .unthrottle = pty_unthrottle,
 525         .set_termios = pty_set_termios,
 526         .cleanup = pty_cleanup,
 527         .resize = pty_resize,
 528         .start = pty_start,
 529         .stop = pty_stop,
 530         .remove = pty_remove
 531 };
 532
 533 static void __init legacy_pty_init(void)
 534 {
 535         struct tty_driver *pty_driver, *pty_slave_driver;
 536
 537         if (legacy_count <= 0)
 538                 return;
 539
 540         pty_driver = tty_alloc_driver(legacy_count,
 541                         TTY_DRIVER_RESET_TERMIOS |
 542                         TTY_DRIVER_REAL_RAW |
 543                         TTY_DRIVER_DYNAMIC_ALLOC);
 544         if (IS_ERR(pty_driver))
 545                 panic("Couldn't allocate pty driver");
 546
 547         pty_slave_driver = tty_alloc_driver(legacy_count,
 548                         TTY_DRIVER_RESET_TERMIOS |
 549                         TTY_DRIVER_REAL_RAW |
 550                         TTY_DRIVER_DYNAMIC_ALLOC);
 551         if (IS_ERR(pty_slave_driver))
 552                 panic("Couldn't allocate pty slave driver");
 553
 554         pty_driver->driver_name = "pty_master";
 555         pty_driver->name = "pty";
 556         pty_driver->major = PTY_MASTER_MAJOR;
 557         pty_driver->minor_start = 0;
 558         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 559         pty_driver->subtype = PTY_TYPE_MASTER;
 560         pty_driver->init_termios = tty_std_termios;
 561         pty_driver->init_termios.c_iflag = 0;
 562         pty_driver->init_termios.c_oflag = 0;
 563         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 564         pty_driver->init_termios.c_lflag = 0;
 565         pty_driver->init_termios.c_ispeed = 38400;
 566         pty_driver->init_termios.c_ospeed = 38400;
 567         pty_driver->other = pty_slave_driver;
 568         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 569
 570         pty_slave_driver->driver_name = "pty_slave";
 571         pty_slave_driver->name = "ttyp";
 572         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 573         pty_slave_driver->minor_start = 0;
 574         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 575         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 576         pty_slave_driver->init_termios = tty_std_termios;
 577         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 578         pty_slave_driver->init_termios.c_ispeed = 38400;
 579         pty_slave_driver->init_termios.c_ospeed = 38400;
 580         pty_slave_driver->other = pty_driver;
 581         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 582
 583         if (tty_register_driver(pty_driver))
 584                 panic("Couldn't register pty driver");
 585         if (tty_register_driver(pty_slave_driver))
 586                 panic("Couldn't register pty slave driver");
 587 }
 588 #else
 589 static inline void legacy_pty_init(void) { }
 590 #endif
 591
 592 /* Unix98 devices */
 593 #ifdef CONFIG_UNIX98_PTYS
 594
 595 static struct cdev ptmx_cdev;
 596
 597 static int pty_unix98_ioctl(struct tty_struct *tty,
 598                             unsigned int cmd, unsigned long arg)
 599 {
 600         switch (cmd) {
 601         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 602                 return pty_set_lock(tty, (int __user *)arg);
 603         case TIOCGPTLCK: /* Get PT Lock status */
 604                 return pty_get_lock(tty, (int __user *)arg);
 605         case TIOCPKT: /* Set PT packet mode */
 606                 return pty_set_pktmode(tty, (int __user *)arg);
 607         case TIOCGPKT: /* Get PT packet mode */
 608                 return pty_get_pktmode(tty, (int __user *)arg);
 609         case TIOCGPTN: /* Get PT Number */
 610                 return put_user(tty->index, (unsigned int __user *)arg);
 611         case TIOCSIG:    /* Send signal to other side of pty */
 612                 return pty_signal(tty, (int) arg);
 613         }
 614
 615         return -ENOIOCTLCMD;
 616 }
 617
 618 /**
 619  *      ptm_unix98_lookup       -       find a pty master
 620  *      @driver: ptm driver
 621  *      @idx: tty index
 622  *
 623  *      Look up a pty master device. Called under the tty_mutex for now.
 624  *      This provides our locking.
 625  */
 626
 627 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 628                 struct inode *ptm_inode, int idx)
 629 {
 630         /* Master must be open via /dev/ptmx */
 631         return ERR_PTR(-EIO);
 632 }
 633
 634 /**
 635  *      pts_unix98_lookup       -       find a pty slave
 636  *      @driver: pts driver
 637  *      @idx: tty index
 638  *
 639  *      Look up a pty master device. Called under the tty_mutex for now.
 640  *      This provides our locking for the tty pointer.
 641  */
 642
 643 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 644                 struct inode *pts_inode, int idx)
 645 {
 646         struct tty_struct *tty;
 647
 648         mutex_lock(&devpts_mutex);
 649         tty = devpts_get_priv(pts_inode);
 650         mutex_unlock(&devpts_mutex);
 651         /* Master must be open before slave */
 652         if (!tty)
 653                 return ERR_PTR(-EIO);
 654         return tty;
 655 }
 656
 657 /* We have no need to install and remove our tty objects as devpts does all
 658    the work for us */
 659
 660 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 661 {
 662         return pty_common_install(driver, tty, false);
 663 }
 664
 665 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 666 {
 667 }
 668
 669 /* this is called once with whichever end is closed last */
 670 static void pty_unix98_shutdown(struct tty_struct *tty)
 671 {
 672         devpts_kill_index(tty->driver_data, tty->index);
 673 }
 674
 675 static const struct tty_operations ptm_unix98_ops = {
 676         .lookup = ptm_unix98_lookup,
 677         .install = pty_unix98_install,
 678         .remove = pty_unix98_remove,
 679         .open = pty_open,
 680         .close = pty_close,
 681         .write = pty_write,
 682         .write_room = pty_write_room,
 683         .flush_buffer = pty_flush_buffer,
 684         .chars_in_buffer = pty_chars_in_buffer,
 685         .unthrottle = pty_unthrottle,
 686         .ioctl = pty_unix98_ioctl,
 687         .resize = pty_resize,
 688         .shutdown = pty_unix98_shutdown,
 689         .cleanup = pty_cleanup
 690 };
 691
 692 static const struct tty_operations pty_unix98_ops = {
 693         .lookup = pts_unix98_lookup,
 694         .install = pty_unix98_install,
 695         .remove = pty_unix98_remove,
 696         .open = pty_open,
 697         .close = pty_close,
 698         .write = pty_write,
 699         .write_room = pty_write_room,
 700         .flush_buffer = pty_flush_buffer,
 701         .chars_in_buffer = pty_chars_in_buffer,
 702         .unthrottle = pty_unthrottle,
 703         .set_termios = pty_set_termios,
 704         .start = pty_start,
 705         .stop = pty_stop,
 706         .shutdown = pty_unix98_shutdown,
 707         .cleanup = pty_cleanup,
 708 };
 709
 710 /**
 711  *      ptmx_open               -       open a unix 98 pty master
 712  *      @inode: inode of device file
 713  *      @filp: file pointer to tty
 714  *
 715  *      Allocate a unix98 pty master device from the ptmx driver.
 716  *
 717  *      Locking: tty_mutex protects the init_dev work. tty->count should
 718  *              protect the rest.
 719  *              allocated_ptys_lock handles the list of free pty numbers
 720  */
 721
 722 static int ptmx_open(struct inode *inode, struct file *filp)
 723 {
 724         struct tty_struct *tty;
 725         struct inode *slave_inode;
 726         int retval;
 727         int index;
 728
 729         nonseekable_open(inode, filp);
 730
 731         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 732         filp->f_mode |= FMODE_NONOTIFY;
 733
 734         retval = tty_alloc_file(filp);
 735         if (retval)
 736                 return retval;
 737
 738         /* find a device that is not in use. */
 739         mutex_lock(&devpts_mutex);
 740         index = devpts_new_index(inode);
 741         if (index < 0) {
 742                 retval = index;
 743                 mutex_unlock(&devpts_mutex);
 744                 goto err_file;
 745         }
 746
 747         mutex_unlock(&devpts_mutex);
 748
 749         mutex_lock(&tty_mutex);
 750         tty = tty_init_dev(ptm_driver, index);
 751
 752         if (IS_ERR(tty)) {
 753                 retval = PTR_ERR(tty);
 754                 goto out;
 755         }
 756
 757         /* The tty returned here is locked so we can safely
 758            drop the mutex */
 759         mutex_unlock(&tty_mutex);
 760
 761         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 762         tty->driver_data = inode;
 763
 764         tty_add_file(tty, filp);
 765
 766         slave_inode = devpts_pty_new(inode,
 767                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 768                         tty->link);
 769         if (IS_ERR(slave_inode)) {
 770                 retval = PTR_ERR(slave_inode);
 771                 goto err_release;
 772         }
 773         tty->link->driver_data = slave_inode;
 774
 775         retval = ptm_driver->ops->open(tty, filp);
 776         if (retval)
 777                 goto err_release;
 778
 779         tty_unlock(tty);
 780         return 0;
 781 err_release:
 782         tty_unlock(tty);
 783         tty_release(inode, filp);
 784         return retval;
 785 out:
 786         mutex_unlock(&tty_mutex);
 787         devpts_kill_index(inode, index);
 788 err_file:
 789         tty_free_file(filp);
 790         return retval;
 791 }
 792
 793 static struct file_operations ptmx_fops;
 794
 795 static void __init unix98_pty_init(void)
 796 {
 797         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 798                         TTY_DRIVER_RESET_TERMIOS |
 799                         TTY_DRIVER_REAL_RAW |
 800                         TTY_DRIVER_DYNAMIC_DEV |
 801                         TTY_DRIVER_DEVPTS_MEM |
 802                         TTY_DRIVER_DYNAMIC_ALLOC);
 803         if (IS_ERR(ptm_driver))
 804                 panic("Couldn't allocate Unix98 ptm driver");
 805         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 806                         TTY_DRIVER_RESET_TERMIOS |
 807                         TTY_DRIVER_REAL_RAW |
 808                         TTY_DRIVER_DYNAMIC_DEV |
 809                         TTY_DRIVER_DEVPTS_MEM |
 810                         TTY_DRIVER_DYNAMIC_ALLOC);
 811         if (IS_ERR(pts_driver))
 812                 panic("Couldn't allocate Unix98 pts driver");
 813
 814         ptm_driver->driver_name = "pty_master";
 815         ptm_driver->name = "ptm";
 816         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 817         ptm_driver->minor_start = 0;
 818         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 819         ptm_driver->subtype = PTY_TYPE_MASTER;
 820         ptm_driver->init_termios = tty_std_termios;
 821         ptm_driver->init_termios.c_iflag = 0;
 822         ptm_driver->init_termios.c_oflag = 0;
 823         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 824         ptm_driver->init_termios.c_lflag = 0;
 825         ptm_driver->init_termios.c_ispeed = 38400;
 826         ptm_driver->init_termios.c_ospeed = 38400;
 827         ptm_driver->other = pts_driver;
 828         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 829
 830         pts_driver->driver_name = "pty_slave";
 831         pts_driver->name = "pts";
 832         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 833         pts_driver->minor_start = 0;
 834         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 835         pts_driver->subtype = PTY_TYPE_SLAVE;
 836         pts_driver->init_termios = tty_std_termios;
 837         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 838         pts_driver->init_termios.c_ispeed = 38400;
 839         pts_driver->init_termios.c_ospeed = 38400;
 840         pts_driver->other = ptm_driver;
 841         tty_set_operations(pts_driver, &pty_unix98_ops);
 842
 843         if (tty_register_driver(ptm_driver))
 844                 panic("Couldn't register Unix98 ptm driver");
 845         if (tty_register_driver(pts_driver))
 846                 panic("Couldn't register Unix98 pts driver");
 847
 848         /* Now create the /dev/ptmx special device */
 849         tty_default_fops(&ptmx_fops);
 850         ptmx_fops.open = ptmx_open;
 851
 852         cdev_init(&ptmx_cdev, &ptmx_fops);
 853         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 854             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 855                 panic("Couldn't register /dev/ptmx driver");
 856         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 857 }
 858
 859 #else
 860 static inline void unix98_pty_init(void) { }
 861 #endif
 862
 863 static int __init pty_init(void)
 864 {
 865         legacy_pty_init();
 866         unix98_pty_init();
 867         return 0;
 868 }
 869 module_init(pty_init);