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 #include <linux/errno.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/tty.h>
  13 #include <linux/tty_flip.h>
  14 #include <linux/fcntl.h>
  15 #include <linux/sched.h>
  16 #include <linux/string.h>
  17 #include <linux/major.h>
  18 #include <linux/mm.h>
  19 #include <linux/init.h>
  20 #include <linux/device.h>
  21 #include <linux/uaccess.h>
  22 #include <linux/bitops.h>
  23 #include <linux/devpts_fs.h>
  24 #include <linux/slab.h>
  25 #include <linux/mutex.h>
  26 #include <linux/poll.h>
  27
  28 #undef TTY_DEBUG_HANGUP
  29 #ifdef TTY_DEBUG_HANGUP
  30 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
  31 #else
  32 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
  33 #endif
  34
  35 #ifdef CONFIG_UNIX98_PTYS
  36 static struct tty_driver *ptm_driver;
  37 static struct tty_driver *pts_driver;
  38 static DEFINE_MUTEX(devpts_mutex);
  39 #endif
  40
  41 static void pty_close(struct tty_struct *tty, struct file *filp)
  42 {
  43         BUG_ON(!tty);
  44         if (tty->driver->subtype == PTY_TYPE_MASTER)
  45                 WARN_ON(tty->count > 1);
  46         else {
  47                 if (test_bit(TTY_IO_ERROR, &tty->flags))
  48                         return;
  49                 if (tty->count > 2)
  50                         return;
  51         }
  52         set_bit(TTY_IO_ERROR, &tty->flags);
  53         wake_up_interruptible(&tty->read_wait);
  54         wake_up_interruptible(&tty->write_wait);
  55         spin_lock_irq(&tty->ctrl_lock);
  56         tty->packet = 0;
  57         spin_unlock_irq(&tty->ctrl_lock);
  58         /* Review - krefs on tty_link ?? */
  59         if (!tty->link)
  60                 return;
  61         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  62         wake_up_interruptible(&tty->link->read_wait);
  63         wake_up_interruptible(&tty->link->write_wait);
  64         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  65                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  66 #ifdef CONFIG_UNIX98_PTYS
  67                 if (tty->driver == ptm_driver) {
  68                         mutex_lock(&devpts_mutex);
  69                         if (tty->link->driver_data)
  70                                 devpts_pty_kill(tty->link->driver_data);
  71                         mutex_unlock(&devpts_mutex);
  72                 }
  73 #endif
  74                 tty_vhangup(tty->link);
  75         }
  76 }
  77
  78 /*
  79  * The unthrottle routine is called by the line discipline to signal
  80  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  81  * flag is always set, to force the line discipline to always call the
  82  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  83  * characters in the queue.  This is necessary since each time this
  84  * happens, we need to wake up any sleeping processes that could be
  85  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  86  * for the pty buffer to be drained.
  87  */
  88 static void pty_unthrottle(struct tty_struct *tty)
  89 {
  90         tty_wakeup(tty->link);
  91         set_bit(TTY_THROTTLED, &tty->flags);
  92 }
  93
  94 /**
  95  *      pty_write               -       write to a pty
  96  *      @tty: the tty we write from
  97  *      @buf: kernel buffer of data
  98  *      @count: bytes to write
  99  *
 100  *      Our "hardware" write method. Data is coming from the ldisc which
 101  *      may be in a non sleeping state. We simply throw this at the other
 102  *      end of the link as if we were an IRQ handler receiving stuff for
 103  *      the other side of the pty/tty pair.
 104  */
 105
 106 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 107 {
 108         struct tty_struct *to = tty->link;
 109
 110         if (tty->stopped)
 111                 return 0;
 112
 113         if (c > 0) {
 114                 /* Stuff the data into the input queue of the other end */
 115                 c = tty_insert_flip_string(to->port, buf, c);
 116                 /* And shovel */
 117                 if (c)
 118                         tty_flip_buffer_push(to->port);
 119         }
 120         return c;
 121 }
 122
 123 /**
 124  *      pty_write_room  -       write space
 125  *      @tty: tty we are writing from
 126  *
 127  *      Report how many bytes the ldisc can send into the queue for
 128  *      the other device.
 129  */
 130
 131 static int pty_write_room(struct tty_struct *tty)
 132 {
 133         if (tty->stopped)
 134                 return 0;
 135         return tty_buffer_space_avail(tty->link->port);
 136 }
 137
 138 /**
 139  *      pty_chars_in_buffer     -       characters currently in our tx queue
 140  *      @tty: our tty
 141  *
 142  *      Report how much we have in the transmit queue. As everything is
 143  *      instantly at the other end this is easy to implement.
 144  */
 145
 146 static int pty_chars_in_buffer(struct tty_struct *tty)
 147 {
 148         return 0;
 149 }
 150
 151 /* Set the lock flag on a pty */
 152 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 153 {
 154         int val;
 155         if (get_user(val, arg))
 156                 return -EFAULT;
 157         if (val)
 158                 set_bit(TTY_PTY_LOCK, &tty->flags);
 159         else
 160                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 161         return 0;
 162 }
 163
 164 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 165 {
 166         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 167         return put_user(locked, arg);
 168 }
 169
 170 /* Set the packet mode on a pty */
 171 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 172 {
 173         int pktmode;
 174
 175         if (get_user(pktmode, arg))
 176                 return -EFAULT;
 177
 178         spin_lock_irq(&tty->ctrl_lock);
 179         if (pktmode) {
 180                 if (!tty->packet) {
 181                         tty->link->ctrl_status = 0;
 182                         smp_mb();
 183                         tty->packet = 1;
 184                 }
 185         } else
 186                 tty->packet = 0;
 187         spin_unlock_irq(&tty->ctrl_lock);
 188
 189         return 0;
 190 }
 191
 192 /* Get the packet mode of a pty */
 193 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 194 {
 195         int pktmode = tty->packet;
 196         return put_user(pktmode, arg);
 197 }
 198
 199 /* Send a signal to the slave */
 200 static int pty_signal(struct tty_struct *tty, int sig)
 201 {
 202         struct pid *pgrp;
 203
 204         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 205                 return -EINVAL;
 206
 207         if (tty->link) {
 208                 pgrp = tty_get_pgrp(tty->link);
 209                 if (pgrp)
 210                         kill_pgrp(pgrp, sig, 1);
 211                 put_pid(pgrp);
 212         }
 213         return 0;
 214 }
 215
 216 static void pty_flush_buffer(struct tty_struct *tty)
 217 {
 218         struct tty_struct *to = tty->link;
 219         struct tty_ldisc *ld;
 220
 221         if (!to)
 222                 return;
 223
 224         ld = tty_ldisc_ref(to);
 225         tty_buffer_flush(to, ld);
 226         if (ld)
 227                 tty_ldisc_deref(ld);
 228
 229         if (to->packet) {
 230                 spin_lock_irq(&tty->ctrl_lock);
 231                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 232                 wake_up_interruptible(&to->read_wait);
 233                 spin_unlock_irq(&tty->ctrl_lock);
 234         }
 235 }
 236
 237 static int pty_open(struct tty_struct *tty, struct file *filp)
 238 {
 239         if (!tty || !tty->link)
 240                 return -ENODEV;
 241
 242         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 243                 goto out;
 244         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 245                 goto out;
 246         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 247                 goto out;
 248
 249         clear_bit(TTY_IO_ERROR, &tty->flags);
 250         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 251         set_bit(TTY_THROTTLED, &tty->flags);
 252         return 0;
 253
 254 out:
 255         set_bit(TTY_IO_ERROR, &tty->flags);
 256         return -EIO;
 257 }
 258
 259 static void pty_set_termios(struct tty_struct *tty,
 260                                         struct ktermios *old_termios)
 261 {
 262         /* See if packet mode change of state. */
 263         if (tty->link && tty->link->packet) {
 264                 int extproc = (old_termios->c_lflag & EXTPROC) |
 265                                 (tty->termios.c_lflag & EXTPROC);
 266                 int old_flow = ((old_termios->c_iflag & IXON) &&
 267                                 (old_termios->c_cc[VSTOP] == '\023') &&
 268                                 (old_termios->c_cc[VSTART] == '\021'));
 269                 int new_flow = (I_IXON(tty) &&
 270                                 STOP_CHAR(tty) == '\023' &&
 271                                 START_CHAR(tty) == '\021');
 272                 if ((old_flow != new_flow) || extproc) {
 273                         spin_lock_irq(&tty->ctrl_lock);
 274                         if (old_flow != new_flow) {
 275                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 276                                 if (new_flow)
 277                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 278                                 else
 279                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 280                         }
 281                         if (extproc)
 282                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 283                         spin_unlock_irq(&tty->ctrl_lock);
 284                         wake_up_interruptible(&tty->link->read_wait);
 285                 }
 286         }
 287
 288         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 289         tty->termios.c_cflag |= (CS8 | CREAD);
 290 }
 291
 292 /**
 293  *      pty_do_resize           -       resize event
 294  *      @tty: tty being resized
 295  *      @ws: window size being set.
 296  *
 297  *      Update the termios variables and send the necessary signals to
 298  *      peform a terminal resize correctly
 299  */
 300
 301 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 302 {
 303         struct pid *pgrp, *rpgrp;
 304         struct tty_struct *pty = tty->link;
 305
 306         /* For a PTY we need to lock the tty side */
 307         mutex_lock(&tty->winsize_mutex);
 308         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 309                 goto done;
 310
 311         /* Signal the foreground process group of both ptys */
 312         pgrp = tty_get_pgrp(tty);
 313         rpgrp = tty_get_pgrp(pty);
 314
 315         if (pgrp)
 316                 kill_pgrp(pgrp, SIGWINCH, 1);
 317         if (rpgrp != pgrp && rpgrp)
 318                 kill_pgrp(rpgrp, SIGWINCH, 1);
 319
 320         put_pid(pgrp);
 321         put_pid(rpgrp);
 322
 323         tty->winsize = *ws;
 324         pty->winsize = *ws;     /* Never used so will go away soon */
 325 done:
 326         mutex_unlock(&tty->winsize_mutex);
 327         return 0;
 328 }
 329
 330 /**
 331  *      pty_start - start() handler
 332  *      pty_stop  - stop() handler
 333  *      @tty: tty being flow-controlled
 334  *
 335  *      Propagates the TIOCPKT status to the master pty.
 336  *
 337  *      NB: only the master pty can be in packet mode so only the slave
 338  *          needs start()/stop() handlers
 339  */
 340 static void pty_start(struct tty_struct *tty)
 341 {
 342         unsigned long flags;
 343
 344         if (tty->link && tty->link->packet) {
 345                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 346                 tty->ctrl_status &= ~TIOCPKT_STOP;
 347                 tty->ctrl_status |= TIOCPKT_START;
 348                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 349                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 350         }
 351 }
 352
 353 static void pty_stop(struct tty_struct *tty)
 354 {
 355         unsigned long flags;
 356
 357         if (tty->link && tty->link->packet) {
 358                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 359                 tty->ctrl_status &= ~TIOCPKT_START;
 360                 tty->ctrl_status |= TIOCPKT_STOP;
 361                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 362                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 363         }
 364 }
 365
 366 /**
 367  *      pty_common_install              -       set up the pty pair
 368  *      @driver: the pty driver
 369  *      @tty: the tty being instantiated
 370  *      @legacy: true if this is BSD style
 371  *
 372  *      Perform the initial set up for the tty/pty pair. Called from the
 373  *      tty layer when the port is first opened.
 374  *
 375  *      Locking: the caller must hold the tty_mutex
 376  */
 377 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 378                 bool legacy)
 379 {
 380         struct tty_struct *o_tty;
 381         struct tty_port *ports[2];
 382         int idx = tty->index;
 383         int retval = -ENOMEM;
 384
 385         /* Opening the slave first has always returned -EIO */
 386         if (driver->subtype != PTY_TYPE_MASTER)
 387                 return -EIO;
 388
 389         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 390         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 391         if (!ports[0] || !ports[1])
 392                 goto err;
 393         if (!try_module_get(driver->other->owner)) {
 394                 /* This cannot in fact currently happen */
 395                 goto err;
 396         }
 397         o_tty = alloc_tty_struct(driver->other, idx);
 398         if (!o_tty)
 399                 goto err_put_module;
 400
 401         tty_set_lock_subclass(o_tty);
 402         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 403
 404         if (legacy) {
 405                 /* We always use new tty termios data so we can do this
 406                    the easy way .. */
 407                 retval = tty_init_termios(tty);
 408                 if (retval)
 409                         goto err_deinit_tty;
 410
 411                 retval = tty_init_termios(o_tty);
 412                 if (retval)
 413                         goto err_free_termios;
 414
 415                 driver->other->ttys[idx] = o_tty;
 416                 driver->ttys[idx] = tty;
 417         } else {
 418                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 419                 tty->termios = driver->init_termios;
 420                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 421                 o_tty->termios = driver->other->init_termios;
 422         }
 423
 424         /*
 425          * Everything allocated ... set up the o_tty structure.
 426          */
 427         tty_driver_kref_get(driver->other);
 428         /* Establish the links in both directions */
 429         tty->link   = o_tty;
 430         o_tty->link = tty;
 431         tty_port_init(ports[0]);
 432         tty_port_init(ports[1]);
 433         tty_buffer_set_limit(ports[0], 8192);
 434         tty_buffer_set_limit(ports[1], 8192);
 435         o_tty->port = ports[0];
 436         tty->port = ports[1];
 437         o_tty->port->itty = o_tty;
 438
 439         tty_buffer_set_lock_subclass(o_tty->port);
 440
 441         tty_driver_kref_get(driver);
 442         tty->count++;
 443         o_tty->count++;
 444         return 0;
 445 err_free_termios:
 446         if (legacy)
 447                 tty_free_termios(tty);
 448 err_deinit_tty:
 449         deinitialize_tty_struct(o_tty);
 450         free_tty_struct(o_tty);
 451 err_put_module:
 452         module_put(driver->other->owner);
 453 err:
 454         kfree(ports[0]);
 455         kfree(ports[1]);
 456         return retval;
 457 }
 458
 459 static void pty_cleanup(struct tty_struct *tty)
 460 {
 461         tty_port_put(tty->port);
 462 }
 463
 464 /* Traditional BSD devices */
 465 #ifdef CONFIG_LEGACY_PTYS
 466
 467 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 468 {
 469         return pty_common_install(driver, tty, true);
 470 }
 471
 472 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 473 {
 474         struct tty_struct *pair = tty->link;
 475         driver->ttys[tty->index] = NULL;
 476         if (pair)
 477                 pair->driver->ttys[pair->index] = NULL;
 478 }
 479
 480 static int pty_bsd_ioctl(struct tty_struct *tty,
 481                          unsigned int cmd, unsigned long arg)
 482 {
 483         switch (cmd) {
 484         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 485                 return pty_set_lock(tty, (int __user *) arg);
 486         case TIOCGPTLCK: /* Get PT Lock status */
 487                 return pty_get_lock(tty, (int __user *)arg);
 488         case TIOCPKT: /* Set PT packet mode */
 489                 return pty_set_pktmode(tty, (int __user *)arg);
 490         case TIOCGPKT: /* Get PT packet mode */
 491                 return pty_get_pktmode(tty, (int __user *)arg);
 492         case TIOCSIG:    /* Send signal to other side of pty */
 493                 return pty_signal(tty, (int) arg);
 494         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 495                 return -EINVAL;
 496         }
 497         return -ENOIOCTLCMD;
 498 }
 499
 500 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 501 /*
 502  * not really modular, but the easiest way to keep compat with existing
 503  * bootargs behaviour is to continue using module_param here.
 504  */
 505 module_param(legacy_count, int, 0);
 506
 507 /*
 508  * The master side of a pty can do TIOCSPTLCK and thus
 509  * has pty_bsd_ioctl.
 510  */
 511 static const struct tty_operations master_pty_ops_bsd = {
 512         .install = pty_install,
 513         .open = pty_open,
 514         .close = pty_close,
 515         .write = pty_write,
 516         .write_room = pty_write_room,
 517         .flush_buffer = pty_flush_buffer,
 518         .chars_in_buffer = pty_chars_in_buffer,
 519         .unthrottle = pty_unthrottle,
 520         .ioctl = pty_bsd_ioctl,
 521         .cleanup = pty_cleanup,
 522         .resize = pty_resize,
 523         .remove = pty_remove
 524 };
 525
 526 static const struct tty_operations slave_pty_ops_bsd = {
 527         .install = pty_install,
 528         .open = pty_open,
 529         .close = pty_close,
 530         .write = pty_write,
 531         .write_room = pty_write_room,
 532         .flush_buffer = pty_flush_buffer,
 533         .chars_in_buffer = pty_chars_in_buffer,
 534         .unthrottle = pty_unthrottle,
 535         .set_termios = pty_set_termios,
 536         .cleanup = pty_cleanup,
 537         .resize = pty_resize,
 538         .start = pty_start,
 539         .stop = pty_stop,
 540         .remove = pty_remove
 541 };
 542
 543 static void __init legacy_pty_init(void)
 544 {
 545         struct tty_driver *pty_driver, *pty_slave_driver;
 546
 547         if (legacy_count <= 0)
 548                 return;
 549
 550         pty_driver = tty_alloc_driver(legacy_count,
 551                         TTY_DRIVER_RESET_TERMIOS |
 552                         TTY_DRIVER_REAL_RAW |
 553                         TTY_DRIVER_DYNAMIC_ALLOC);
 554         if (IS_ERR(pty_driver))
 555                 panic("Couldn't allocate pty driver");
 556
 557         pty_slave_driver = tty_alloc_driver(legacy_count,
 558                         TTY_DRIVER_RESET_TERMIOS |
 559                         TTY_DRIVER_REAL_RAW |
 560                         TTY_DRIVER_DYNAMIC_ALLOC);
 561         if (IS_ERR(pty_slave_driver))
 562                 panic("Couldn't allocate pty slave driver");
 563
 564         pty_driver->driver_name = "pty_master";
 565         pty_driver->name = "pty";
 566         pty_driver->major = PTY_MASTER_MAJOR;
 567         pty_driver->minor_start = 0;
 568         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 569         pty_driver->subtype = PTY_TYPE_MASTER;
 570         pty_driver->init_termios = tty_std_termios;
 571         pty_driver->init_termios.c_iflag = 0;
 572         pty_driver->init_termios.c_oflag = 0;
 573         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 574         pty_driver->init_termios.c_lflag = 0;
 575         pty_driver->init_termios.c_ispeed = 38400;
 576         pty_driver->init_termios.c_ospeed = 38400;
 577         pty_driver->other = pty_slave_driver;
 578         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 579
 580         pty_slave_driver->driver_name = "pty_slave";
 581         pty_slave_driver->name = "ttyp";
 582         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 583         pty_slave_driver->minor_start = 0;
 584         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 585         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 586         pty_slave_driver->init_termios = tty_std_termios;
 587         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 588         pty_slave_driver->init_termios.c_ispeed = 38400;
 589         pty_slave_driver->init_termios.c_ospeed = 38400;
 590         pty_slave_driver->other = pty_driver;
 591         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 592
 593         if (tty_register_driver(pty_driver))
 594                 panic("Couldn't register pty driver");
 595         if (tty_register_driver(pty_slave_driver))
 596                 panic("Couldn't register pty slave driver");
 597 }
 598 #else
 599 static inline void legacy_pty_init(void) { }
 600 #endif
 601
 602 /* Unix98 devices */
 603 #ifdef CONFIG_UNIX98_PTYS
 604
 605 static struct cdev ptmx_cdev;
 606
 607 static int pty_unix98_ioctl(struct tty_struct *tty,
 608                             unsigned int cmd, unsigned long arg)
 609 {
 610         switch (cmd) {
 611         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 612                 return pty_set_lock(tty, (int __user *)arg);
 613         case TIOCGPTLCK: /* Get PT Lock status */
 614                 return pty_get_lock(tty, (int __user *)arg);
 615         case TIOCPKT: /* Set PT packet mode */
 616                 return pty_set_pktmode(tty, (int __user *)arg);
 617         case TIOCGPKT: /* Get PT packet mode */
 618                 return pty_get_pktmode(tty, (int __user *)arg);
 619         case TIOCGPTN: /* Get PT Number */
 620                 return put_user(tty->index, (unsigned int __user *)arg);
 621         case TIOCSIG:    /* Send signal to other side of pty */
 622                 return pty_signal(tty, (int) arg);
 623         }
 624
 625         return -ENOIOCTLCMD;
 626 }
 627
 628 /**
 629  *      ptm_unix98_lookup       -       find a pty master
 630  *      @driver: ptm 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.
 635  */
 636
 637 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 638                 struct inode *ptm_inode, int idx)
 639 {
 640         /* Master must be open via /dev/ptmx */
 641         return ERR_PTR(-EIO);
 642 }
 643
 644 /**
 645  *      pts_unix98_lookup       -       find a pty slave
 646  *      @driver: pts driver
 647  *      @idx: tty index
 648  *
 649  *      Look up a pty master device. Called under the tty_mutex for now.
 650  *      This provides our locking for the tty pointer.
 651  */
 652
 653 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 654                 struct inode *pts_inode, int idx)
 655 {
 656         struct tty_struct *tty;
 657
 658         mutex_lock(&devpts_mutex);
 659         tty = devpts_get_priv(pts_inode);
 660         mutex_unlock(&devpts_mutex);
 661         /* Master must be open before slave */
 662         if (!tty)
 663                 return ERR_PTR(-EIO);
 664         return tty;
 665 }
 666
 667 /* We have no need to install and remove our tty objects as devpts does all
 668    the work for us */
 669
 670 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 671 {
 672         return pty_common_install(driver, tty, false);
 673 }
 674
 675 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 676 {
 677 }
 678
 679 /* this is called once with whichever end is closed last */
 680 static void pty_unix98_shutdown(struct tty_struct *tty)
 681 {
 682         struct inode *ptmx_inode;
 683
 684         if (tty->driver->subtype == PTY_TYPE_MASTER)
 685                 ptmx_inode = tty->driver_data;
 686         else
 687                 ptmx_inode = tty->link->driver_data;
 688         devpts_kill_index(ptmx_inode, tty->index);
 689         devpts_del_ref(ptmx_inode);
 690 }
 691
 692 static const struct tty_operations ptm_unix98_ops = {
 693         .lookup = ptm_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         .ioctl = pty_unix98_ioctl,
 704         .resize = pty_resize,
 705         .shutdown = pty_unix98_shutdown,
 706         .cleanup = pty_cleanup
 707 };
 708
 709 static const struct tty_operations pty_unix98_ops = {
 710         .lookup = pts_unix98_lookup,
 711         .install = pty_unix98_install,
 712         .remove = pty_unix98_remove,
 713         .open = pty_open,
 714         .close = pty_close,
 715         .write = pty_write,
 716         .write_room = pty_write_room,
 717         .flush_buffer = pty_flush_buffer,
 718         .chars_in_buffer = pty_chars_in_buffer,
 719         .unthrottle = pty_unthrottle,
 720         .set_termios = pty_set_termios,
 721         .start = pty_start,
 722         .stop = pty_stop,
 723         .shutdown = pty_unix98_shutdown,
 724         .cleanup = pty_cleanup,
 725 };
 726
 727 /**
 728  *      ptmx_open               -       open a unix 98 pty master
 729  *      @inode: inode of device file
 730  *      @filp: file pointer to tty
 731  *
 732  *      Allocate a unix98 pty master device from the ptmx driver.
 733  *
 734  *      Locking: tty_mutex protects the init_dev work. tty->count should
 735  *              protect the rest.
 736  *              allocated_ptys_lock handles the list of free pty numbers
 737  */
 738
 739 static int ptmx_open(struct inode *inode, struct file *filp)
 740 {
 741         struct tty_struct *tty;
 742         struct inode *slave_inode;
 743         int retval;
 744         int index;
 745
 746         nonseekable_open(inode, filp);
 747
 748         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 749         filp->f_mode |= FMODE_NONOTIFY;
 750
 751         retval = tty_alloc_file(filp);
 752         if (retval)
 753                 return retval;
 754
 755         /* find a device that is not in use. */
 756         mutex_lock(&devpts_mutex);
 757         index = devpts_new_index(inode);
 758         if (index < 0) {
 759                 retval = index;
 760                 mutex_unlock(&devpts_mutex);
 761                 goto err_file;
 762         }
 763
 764         mutex_unlock(&devpts_mutex);
 765
 766         mutex_lock(&tty_mutex);
 767         tty = tty_init_dev(ptm_driver, index);
 768
 769         if (IS_ERR(tty)) {
 770                 retval = PTR_ERR(tty);
 771                 goto out;
 772         }
 773
 774         /* The tty returned here is locked so we can safely
 775            drop the mutex */
 776         mutex_unlock(&tty_mutex);
 777
 778         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 779         tty->driver_data = inode;
 780
 781         /*
 782          * In the case where all references to ptmx inode are dropped and we
 783          * still have /dev/tty opened pointing to the master/slave pair (ptmx
 784          * is closed/released before /dev/tty), we must make sure that the inode
 785          * is still valid when we call the final pty_unix98_shutdown, thus we
 786          * hold an additional reference to the ptmx inode. For the same /dev/tty
 787          * last close case, we also need to make sure the super_block isn't
 788          * destroyed (devpts instance unmounted), before /dev/tty is closed and
 789          * on its release devpts_kill_index is called.
 790          */
 791         devpts_add_ref(inode);
 792
 793         tty_add_file(tty, filp);
 794
 795         slave_inode = devpts_pty_new(inode,
 796                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 797                         tty->link);
 798         if (IS_ERR(slave_inode)) {
 799                 retval = PTR_ERR(slave_inode);
 800                 goto err_release;
 801         }
 802         tty->link->driver_data = slave_inode;
 803
 804         retval = ptm_driver->ops->open(tty, filp);
 805         if (retval)
 806                 goto err_release;
 807
 808         tty_debug_hangup(tty, "(tty count=%d)\n", tty->count);
 809
 810         tty_unlock(tty);
 811         return 0;
 812 err_release:
 813         tty_unlock(tty);
 814         tty_release(inode, filp);
 815         return retval;
 816 out:
 817         mutex_unlock(&tty_mutex);
 818         devpts_kill_index(inode, index);
 819 err_file:
 820         tty_free_file(filp);
 821         return retval;
 822 }
 823
 824 static struct file_operations ptmx_fops;
 825
 826 static void __init unix98_pty_init(void)
 827 {
 828         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 829                         TTY_DRIVER_RESET_TERMIOS |
 830                         TTY_DRIVER_REAL_RAW |
 831                         TTY_DRIVER_DYNAMIC_DEV |
 832                         TTY_DRIVER_DEVPTS_MEM |
 833                         TTY_DRIVER_DYNAMIC_ALLOC);
 834         if (IS_ERR(ptm_driver))
 835                 panic("Couldn't allocate Unix98 ptm driver");
 836         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 837                         TTY_DRIVER_RESET_TERMIOS |
 838                         TTY_DRIVER_REAL_RAW |
 839                         TTY_DRIVER_DYNAMIC_DEV |
 840                         TTY_DRIVER_DEVPTS_MEM |
 841                         TTY_DRIVER_DYNAMIC_ALLOC);
 842         if (IS_ERR(pts_driver))
 843                 panic("Couldn't allocate Unix98 pts driver");
 844
 845         ptm_driver->driver_name = "pty_master";
 846         ptm_driver->name = "ptm";
 847         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 848         ptm_driver->minor_start = 0;
 849         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 850         ptm_driver->subtype = PTY_TYPE_MASTER;
 851         ptm_driver->init_termios = tty_std_termios;
 852         ptm_driver->init_termios.c_iflag = 0;
 853         ptm_driver->init_termios.c_oflag = 0;
 854         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 855         ptm_driver->init_termios.c_lflag = 0;
 856         ptm_driver->init_termios.c_ispeed = 38400;
 857         ptm_driver->init_termios.c_ospeed = 38400;
 858         ptm_driver->other = pts_driver;
 859         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 860
 861         pts_driver->driver_name = "pty_slave";
 862         pts_driver->name = "pts";
 863         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 864         pts_driver->minor_start = 0;
 865         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 866         pts_driver->subtype = PTY_TYPE_SLAVE;
 867         pts_driver->init_termios = tty_std_termios;
 868         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 869         pts_driver->init_termios.c_ispeed = 38400;
 870         pts_driver->init_termios.c_ospeed = 38400;
 871         pts_driver->other = ptm_driver;
 872         tty_set_operations(pts_driver, &pty_unix98_ops);
 873
 874         if (tty_register_driver(ptm_driver))
 875                 panic("Couldn't register Unix98 ptm driver");
 876         if (tty_register_driver(pts_driver))
 877                 panic("Couldn't register Unix98 pts driver");
 878
 879         /* Now create the /dev/ptmx special device */
 880         tty_default_fops(&ptmx_fops);
 881         ptmx_fops.open = ptmx_open;
 882
 883         cdev_init(&ptmx_cdev, &ptmx_fops);
 884         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 885             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 886                 panic("Couldn't register /dev/ptmx driver");
 887         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 888 }
 889
 890 #else
 891 static inline void unix98_pty_init(void) { }
 892 #endif
 893
 894 static int __init pty_init(void)
 895 {
 896         legacy_pty_init();
 897         unix98_pty_init();
 898         return 0;
 899 }
 900 device_initcall(pty_init);