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         tty_flip_buffer_push(tty->link->port);
  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         /* TTY_OTHER_CLOSED must be cleared before TTY_OTHER_DONE */
 251         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 252         clear_bit(TTY_OTHER_DONE, &tty->link->flags);
 253         set_bit(TTY_THROTTLED, &tty->flags);
 254         return 0;
 255
 256 out:
 257         set_bit(TTY_IO_ERROR, &tty->flags);
 258         return -EIO;
 259 }
 260
 261 static void pty_set_termios(struct tty_struct *tty,
 262                                         struct ktermios *old_termios)
 263 {
 264         /* See if packet mode change of state. */
 265         if (tty->link && tty->link->packet) {
 266                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
 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         tty_set_lock_subclass(o_tty);
 403         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 404
 405         if (legacy) {
 406                 /* We always use new tty termios data so we can do this
 407                    the easy way .. */
 408                 tty_init_termios(tty);
 409                 tty_init_termios(o_tty);
 410
 411                 driver->other->ttys[idx] = o_tty;
 412                 driver->ttys[idx] = tty;
 413         } else {
 414                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 415                 tty->termios = driver->init_termios;
 416                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 417                 o_tty->termios = driver->other->init_termios;
 418         }
 419
 420         /*
 421          * Everything allocated ... set up the o_tty structure.
 422          */
 423         tty_driver_kref_get(driver->other);
 424         /* Establish the links in both directions */
 425         tty->link   = o_tty;
 426         o_tty->link = tty;
 427         tty_port_init(ports[0]);
 428         tty_port_init(ports[1]);
 429         tty_buffer_set_limit(ports[0], 8192);
 430         tty_buffer_set_limit(ports[1], 8192);
 431         o_tty->port = ports[0];
 432         tty->port = ports[1];
 433         o_tty->port->itty = o_tty;
 434
 435         tty_buffer_set_lock_subclass(o_tty->port);
 436
 437         tty_driver_kref_get(driver);
 438         tty->count++;
 439         o_tty->count++;
 440         return 0;
 441
 442 err_put_module:
 443         module_put(driver->other->owner);
 444 err:
 445         kfree(ports[0]);
 446         kfree(ports[1]);
 447         return retval;
 448 }
 449
 450 static void pty_cleanup(struct tty_struct *tty)
 451 {
 452         tty_port_put(tty->port);
 453 }
 454
 455 /* Traditional BSD devices */
 456 #ifdef CONFIG_LEGACY_PTYS
 457
 458 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 459 {
 460         return pty_common_install(driver, tty, true);
 461 }
 462
 463 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 464 {
 465         struct tty_struct *pair = tty->link;
 466         driver->ttys[tty->index] = NULL;
 467         if (pair)
 468                 pair->driver->ttys[pair->index] = NULL;
 469 }
 470
 471 static int pty_bsd_ioctl(struct tty_struct *tty,
 472                          unsigned int cmd, unsigned long arg)
 473 {
 474         switch (cmd) {
 475         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 476                 return pty_set_lock(tty, (int __user *) arg);
 477         case TIOCGPTLCK: /* Get PT Lock status */
 478                 return pty_get_lock(tty, (int __user *)arg);
 479         case TIOCPKT: /* Set PT packet mode */
 480                 return pty_set_pktmode(tty, (int __user *)arg);
 481         case TIOCGPKT: /* Get PT packet mode */
 482                 return pty_get_pktmode(tty, (int __user *)arg);
 483         case TIOCSIG:    /* Send signal to other side of pty */
 484                 return pty_signal(tty, (int) arg);
 485         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 486                 return -EINVAL;
 487         }
 488         return -ENOIOCTLCMD;
 489 }
 490
 491 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 492 /*
 493  * not really modular, but the easiest way to keep compat with existing
 494  * bootargs behaviour is to continue using module_param here.
 495  */
 496 module_param(legacy_count, int, 0);
 497
 498 /*
 499  * The master side of a pty can do TIOCSPTLCK and thus
 500  * has pty_bsd_ioctl.
 501  */
 502 static const struct tty_operations master_pty_ops_bsd = {
 503         .install = pty_install,
 504         .open = pty_open,
 505         .close = pty_close,
 506         .write = pty_write,
 507         .write_room = pty_write_room,
 508         .flush_buffer = pty_flush_buffer,
 509         .chars_in_buffer = pty_chars_in_buffer,
 510         .unthrottle = pty_unthrottle,
 511         .ioctl = pty_bsd_ioctl,
 512         .cleanup = pty_cleanup,
 513         .resize = pty_resize,
 514         .remove = pty_remove
 515 };
 516
 517 static const struct tty_operations slave_pty_ops_bsd = {
 518         .install = pty_install,
 519         .open = pty_open,
 520         .close = pty_close,
 521         .write = pty_write,
 522         .write_room = pty_write_room,
 523         .flush_buffer = pty_flush_buffer,
 524         .chars_in_buffer = pty_chars_in_buffer,
 525         .unthrottle = pty_unthrottle,
 526         .set_termios = pty_set_termios,
 527         .cleanup = pty_cleanup,
 528         .resize = pty_resize,
 529         .start = pty_start,
 530         .stop = pty_stop,
 531         .remove = pty_remove
 532 };
 533
 534 static void __init legacy_pty_init(void)
 535 {
 536         struct tty_driver *pty_driver, *pty_slave_driver;
 537
 538         if (legacy_count <= 0)
 539                 return;
 540
 541         pty_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_driver))
 546                 panic("Couldn't allocate pty driver");
 547
 548         pty_slave_driver = tty_alloc_driver(legacy_count,
 549                         TTY_DRIVER_RESET_TERMIOS |
 550                         TTY_DRIVER_REAL_RAW |
 551                         TTY_DRIVER_DYNAMIC_ALLOC);
 552         if (IS_ERR(pty_slave_driver))
 553                 panic("Couldn't allocate pty slave driver");
 554
 555         pty_driver->driver_name = "pty_master";
 556         pty_driver->name = "pty";
 557         pty_driver->major = PTY_MASTER_MAJOR;
 558         pty_driver->minor_start = 0;
 559         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 560         pty_driver->subtype = PTY_TYPE_MASTER;
 561         pty_driver->init_termios = tty_std_termios;
 562         pty_driver->init_termios.c_iflag = 0;
 563         pty_driver->init_termios.c_oflag = 0;
 564         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 565         pty_driver->init_termios.c_lflag = 0;
 566         pty_driver->init_termios.c_ispeed = 38400;
 567         pty_driver->init_termios.c_ospeed = 38400;
 568         pty_driver->other = pty_slave_driver;
 569         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 570
 571         pty_slave_driver->driver_name = "pty_slave";
 572         pty_slave_driver->name = "ttyp";
 573         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 574         pty_slave_driver->minor_start = 0;
 575         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 576         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 577         pty_slave_driver->init_termios = tty_std_termios;
 578         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 579         pty_slave_driver->init_termios.c_ispeed = 38400;
 580         pty_slave_driver->init_termios.c_ospeed = 38400;
 581         pty_slave_driver->other = pty_driver;
 582         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 583
 584         if (tty_register_driver(pty_driver))
 585                 panic("Couldn't register pty driver");
 586         if (tty_register_driver(pty_slave_driver))
 587                 panic("Couldn't register pty slave driver");
 588 }
 589 #else
 590 static inline void legacy_pty_init(void) { }
 591 #endif
 592
 593 /* Unix98 devices */
 594 #ifdef CONFIG_UNIX98_PTYS
 595
 596 static struct cdev ptmx_cdev;
 597
 598 static int pty_unix98_ioctl(struct tty_struct *tty,
 599                             unsigned int cmd, unsigned long arg)
 600 {
 601         switch (cmd) {
 602         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 603                 return pty_set_lock(tty, (int __user *)arg);
 604         case TIOCGPTLCK: /* Get PT Lock status */
 605                 return pty_get_lock(tty, (int __user *)arg);
 606         case TIOCPKT: /* Set PT packet mode */
 607                 return pty_set_pktmode(tty, (int __user *)arg);
 608         case TIOCGPKT: /* Get PT packet mode */
 609                 return pty_get_pktmode(tty, (int __user *)arg);
 610         case TIOCGPTN: /* Get PT Number */
 611                 return put_user(tty->index, (unsigned int __user *)arg);
 612         case TIOCSIG:    /* Send signal to other side of pty */
 613                 return pty_signal(tty, (int) arg);
 614         }
 615
 616         return -ENOIOCTLCMD;
 617 }
 618
 619 /**
 620  *      ptm_unix98_lookup       -       find a pty master
 621  *      @driver: ptm driver
 622  *      @idx: tty index
 623  *
 624  *      Look up a pty master device. Called under the tty_mutex for now.
 625  *      This provides our locking.
 626  */
 627
 628 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 629                 struct inode *ptm_inode, int idx)
 630 {
 631         /* Master must be open via /dev/ptmx */
 632         return ERR_PTR(-EIO);
 633 }
 634
 635 /**
 636  *      pts_unix98_lookup       -       find a pty slave
 637  *      @driver: pts driver
 638  *      @idx: tty index
 639  *
 640  *      Look up a pty master device. Called under the tty_mutex for now.
 641  *      This provides our locking for the tty pointer.
 642  */
 643
 644 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 645                 struct inode *pts_inode, int idx)
 646 {
 647         struct tty_struct *tty;
 648
 649         mutex_lock(&devpts_mutex);
 650         tty = devpts_get_priv(pts_inode);
 651         mutex_unlock(&devpts_mutex);
 652         /* Master must be open before slave */
 653         if (!tty)
 654                 return ERR_PTR(-EIO);
 655         return tty;
 656 }
 657
 658 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 659 {
 660         return pty_common_install(driver, tty, false);
 661 }
 662
 663 /* this is called once with whichever end is closed last */
 664 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 665 {
 666         struct inode *ptmx_inode;
 667
 668         if (tty->driver->subtype == PTY_TYPE_MASTER)
 669                 ptmx_inode = tty->driver_data;
 670         else
 671                 ptmx_inode = tty->link->driver_data;
 672         devpts_kill_index(ptmx_inode, tty->index);
 673         devpts_del_ref(ptmx_inode);
 674 }
 675
 676 static const struct tty_operations ptm_unix98_ops = {
 677         .lookup = ptm_unix98_lookup,
 678         .install = pty_unix98_install,
 679         .remove = pty_unix98_remove,
 680         .open = pty_open,
 681         .close = pty_close,
 682         .write = pty_write,
 683         .write_room = pty_write_room,
 684         .flush_buffer = pty_flush_buffer,
 685         .chars_in_buffer = pty_chars_in_buffer,
 686         .unthrottle = pty_unthrottle,
 687         .ioctl = pty_unix98_ioctl,
 688         .resize = pty_resize,
 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         .cleanup = pty_cleanup,
 707 };
 708
 709 /**
 710  *      ptmx_open               -       open a unix 98 pty master
 711  *      @inode: inode of device file
 712  *      @filp: file pointer to tty
 713  *
 714  *      Allocate a unix98 pty master device from the ptmx driver.
 715  *
 716  *      Locking: tty_mutex protects the init_dev work. tty->count should
 717  *              protect the rest.
 718  *              allocated_ptys_lock handles the list of free pty numbers
 719  */
 720
 721 static int ptmx_open(struct inode *inode, struct file *filp)
 722 {
 723         struct tty_struct *tty;
 724         struct inode *slave_inode;
 725         int retval;
 726         int index;
 727
 728         nonseekable_open(inode, filp);
 729
 730         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 731         filp->f_mode |= FMODE_NONOTIFY;
 732
 733         retval = tty_alloc_file(filp);
 734         if (retval)
 735                 return retval;
 736
 737         /* find a device that is not in use. */
 738         mutex_lock(&devpts_mutex);
 739         index = devpts_new_index(inode);
 740         if (index < 0) {
 741                 retval = index;
 742                 mutex_unlock(&devpts_mutex);
 743                 goto err_file;
 744         }
 745
 746         mutex_unlock(&devpts_mutex);
 747
 748         mutex_lock(&tty_mutex);
 749         tty = tty_init_dev(ptm_driver, index);
 750
 751         if (IS_ERR(tty)) {
 752                 retval = PTR_ERR(tty);
 753                 goto out;
 754         }
 755
 756         /* The tty returned here is locked so we can safely
 757            drop the mutex */
 758         mutex_unlock(&tty_mutex);
 759
 760         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 761         tty->driver_data = inode;
 762
 763         /*
 764          * In the case where all references to ptmx inode are dropped and we
 765          * still have /dev/tty opened pointing to the master/slave pair (ptmx
 766          * is closed/released before /dev/tty), we must make sure that the inode
 767          * is still valid when we call the final pty_unix98_shutdown, thus we
 768          * hold an additional reference to the ptmx inode. For the same /dev/tty
 769          * last close case, we also need to make sure the super_block isn't
 770          * destroyed (devpts instance unmounted), before /dev/tty is closed and
 771          * on its release devpts_kill_index is called.
 772          */
 773         devpts_add_ref(inode);
 774
 775         tty_add_file(tty, filp);
 776
 777         slave_inode = devpts_pty_new(inode,
 778                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 779                         tty->link);
 780         if (IS_ERR(slave_inode)) {
 781                 retval = PTR_ERR(slave_inode);
 782                 goto err_release;
 783         }
 784         tty->link->driver_data = slave_inode;
 785
 786         retval = ptm_driver->ops->open(tty, filp);
 787         if (retval)
 788                 goto err_release;
 789
 790         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 791
 792         tty_unlock(tty);
 793         return 0;
 794 err_release:
 795         tty_unlock(tty);
 796         tty_release(inode, filp);
 797         return retval;
 798 out:
 799         mutex_unlock(&tty_mutex);
 800         devpts_kill_index(inode, index);
 801 err_file:
 802         tty_free_file(filp);
 803         return retval;
 804 }
 805
 806 static struct file_operations ptmx_fops;
 807
 808 static void __init unix98_pty_init(void)
 809 {
 810         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 811                         TTY_DRIVER_RESET_TERMIOS |
 812                         TTY_DRIVER_REAL_RAW |
 813                         TTY_DRIVER_DYNAMIC_DEV |
 814                         TTY_DRIVER_DEVPTS_MEM |
 815                         TTY_DRIVER_DYNAMIC_ALLOC);
 816         if (IS_ERR(ptm_driver))
 817                 panic("Couldn't allocate Unix98 ptm driver");
 818         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 819                         TTY_DRIVER_RESET_TERMIOS |
 820                         TTY_DRIVER_REAL_RAW |
 821                         TTY_DRIVER_DYNAMIC_DEV |
 822                         TTY_DRIVER_DEVPTS_MEM |
 823                         TTY_DRIVER_DYNAMIC_ALLOC);
 824         if (IS_ERR(pts_driver))
 825                 panic("Couldn't allocate Unix98 pts driver");
 826
 827         ptm_driver->driver_name = "pty_master";
 828         ptm_driver->name = "ptm";
 829         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 830         ptm_driver->minor_start = 0;
 831         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 832         ptm_driver->subtype = PTY_TYPE_MASTER;
 833         ptm_driver->init_termios = tty_std_termios;
 834         ptm_driver->init_termios.c_iflag = 0;
 835         ptm_driver->init_termios.c_oflag = 0;
 836         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 837         ptm_driver->init_termios.c_lflag = 0;
 838         ptm_driver->init_termios.c_ispeed = 38400;
 839         ptm_driver->init_termios.c_ospeed = 38400;
 840         ptm_driver->other = pts_driver;
 841         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 842
 843         pts_driver->driver_name = "pty_slave";
 844         pts_driver->name = "pts";
 845         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 846         pts_driver->minor_start = 0;
 847         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 848         pts_driver->subtype = PTY_TYPE_SLAVE;
 849         pts_driver->init_termios = tty_std_termios;
 850         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 851         pts_driver->init_termios.c_ispeed = 38400;
 852         pts_driver->init_termios.c_ospeed = 38400;
 853         pts_driver->other = ptm_driver;
 854         tty_set_operations(pts_driver, &pty_unix98_ops);
 855
 856         if (tty_register_driver(ptm_driver))
 857                 panic("Couldn't register Unix98 ptm driver");
 858         if (tty_register_driver(pts_driver))
 859                 panic("Couldn't register Unix98 pts driver");
 860
 861         /* Now create the /dev/ptmx special device */
 862         tty_default_fops(&ptmx_fops);
 863         ptmx_fops.open = ptmx_open;
 864
 865         cdev_init(&ptmx_cdev, &ptmx_fops);
 866         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 867             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 868                 panic("Couldn't register /dev/ptmx driver");
 869         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 870 }
 871
 872 #else
 873 static inline void unix98_pty_init(void) { }
 874 #endif
 875
 876 static int __init pty_init(void)
 877 {
 878         legacy_pty_init();
 879         unix98_pty_init();
 880         return 0;
 881 }
 882 device_initcall(pty_init);