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         tty_flush_to_ldisc(tty->link);
  57         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  58         wake_up_interruptible(&tty->link->read_wait);
  59         wake_up_interruptible(&tty->link->write_wait);
  60         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  61                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  62 #ifdef CONFIG_UNIX98_PTYS
  63                 if (tty->driver == ptm_driver) {
  64                         mutex_lock(&devpts_mutex);
  65                         if (tty->link->driver_data)
  66                                 devpts_pty_kill(tty->link->driver_data);
  67                         mutex_unlock(&devpts_mutex);
  68                 }
  69 #endif
  70                 tty_vhangup(tty->link);
  71         }
  72 }
  73
  74 /*
  75  * The unthrottle routine is called by the line discipline to signal
  76  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  77  * flag is always set, to force the line discipline to always call the
  78  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  79  * characters in the queue.  This is necessary since each time this
  80  * happens, we need to wake up any sleeping processes that could be
  81  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  82  * for the pty buffer to be drained.
  83  */
  84 static void pty_unthrottle(struct tty_struct *tty)
  85 {
  86         tty_wakeup(tty->link);
  87         set_bit(TTY_THROTTLED, &tty->flags);
  88 }
  89
  90 /**
  91  *      pty_space       -       report space left for writing
  92  *      @to: tty we are writing into
  93  *
  94  *      Limit the buffer space used by ptys to 8k.
  95  */
  96
  97 static int pty_space(struct tty_struct *to)
  98 {
  99         int n = tty_buffer_space_avail(to->port);
 100         return min(n, 8192);
 101 }
 102
 103 /**
 104  *      pty_write               -       write to a pty
 105  *      @tty: the tty we write from
 106  *      @buf: kernel buffer of data
 107  *      @count: bytes to write
 108  *
 109  *      Our "hardware" write method. Data is coming from the ldisc which
 110  *      may be in a non sleeping state. We simply throw this at the other
 111  *      end of the link as if we were an IRQ handler receiving stuff for
 112  *      the other side of the pty/tty pair.
 113  */
 114
 115 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 116 {
 117         struct tty_struct *to = tty->link;
 118
 119         if (tty->stopped)
 120                 return 0;
 121
 122         if (c > 0) {
 123                 /* Stuff the data into the input queue of the other end */
 124                 c = tty_insert_flip_string(to->port, buf, c);
 125                 /* And shovel */
 126                 if (c)
 127                         tty_flip_buffer_push(to->port);
 128         }
 129         return c;
 130 }
 131
 132 /**
 133  *      pty_write_room  -       write space
 134  *      @tty: tty we are writing from
 135  *
 136  *      Report how many bytes the ldisc can send into the queue for
 137  *      the other device.
 138  */
 139
 140 static int pty_write_room(struct tty_struct *tty)
 141 {
 142         if (tty->stopped)
 143                 return 0;
 144         return pty_space(tty->link);
 145 }
 146
 147 /**
 148  *      pty_chars_in_buffer     -       characters currently in our tx queue
 149  *      @tty: our tty
 150  *
 151  *      Report how much we have in the transmit queue. As everything is
 152  *      instantly at the other end this is easy to implement.
 153  */
 154
 155 static int pty_chars_in_buffer(struct tty_struct *tty)
 156 {
 157         return 0;
 158 }
 159
 160 /* Set the lock flag on a pty */
 161 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 162 {
 163         int val;
 164         if (get_user(val, arg))
 165                 return -EFAULT;
 166         if (val)
 167                 set_bit(TTY_PTY_LOCK, &tty->flags);
 168         else
 169                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 170         return 0;
 171 }
 172
 173 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 174 {
 175         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 176         return put_user(locked, arg);
 177 }
 178
 179 /* Set the packet mode on a pty */
 180 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 181 {
 182         int pktmode;
 183
 184         if (get_user(pktmode, arg))
 185                 return -EFAULT;
 186
 187         spin_lock_irq(&tty->ctrl_lock);
 188         if (pktmode) {
 189                 if (!tty->packet) {
 190                         tty->link->ctrl_status = 0;
 191                         smp_mb();
 192                         tty->packet = 1;
 193                 }
 194         } else
 195                 tty->packet = 0;
 196         spin_unlock_irq(&tty->ctrl_lock);
 197
 198         return 0;
 199 }
 200
 201 /* Get the packet mode of a pty */
 202 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 203 {
 204         int pktmode = tty->packet;
 205         return put_user(pktmode, arg);
 206 }
 207
 208 /* Send a signal to the slave */
 209 static int pty_signal(struct tty_struct *tty, int sig)
 210 {
 211         struct pid *pgrp;
 212
 213         if (tty->link) {
 214                 pgrp = tty_get_pgrp(tty->link);
 215                 if (pgrp)
 216                         kill_pgrp(pgrp, sig, 1);
 217                 put_pid(pgrp);
 218         }
 219         return 0;
 220 }
 221
 222 static void pty_flush_buffer(struct tty_struct *tty)
 223 {
 224         struct tty_struct *to = tty->link;
 225
 226         if (!to)
 227                 return;
 228         /* tty_buffer_flush(to); FIXME */
 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
 403         if (legacy) {
 404                 /* We always use new tty termios data so we can do this
 405                    the easy way .. */
 406                 retval = tty_init_termios(tty);
 407                 if (retval)
 408                         goto err_deinit_tty;
 409
 410                 retval = tty_init_termios(o_tty);
 411                 if (retval)
 412                         goto err_free_termios;
 413
 414                 driver->other->ttys[idx] = o_tty;
 415                 driver->ttys[idx] = tty;
 416         } else {
 417                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 418                 tty->termios = driver->init_termios;
 419                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 420                 o_tty->termios = driver->other->init_termios;
 421         }
 422
 423         /*
 424          * Everything allocated ... set up the o_tty structure.
 425          */
 426         tty_driver_kref_get(driver->other);
 427         /* Establish the links in both directions */
 428         tty->link   = o_tty;
 429         o_tty->link = tty;
 430         tty_port_init(ports[0]);
 431         tty_port_init(ports[1]);
 432         o_tty->port = ports[0];
 433         tty->port = ports[1];
 434         o_tty->port->itty = o_tty;
 435
 436         tty_driver_kref_get(driver);
 437         tty->count++;
 438         o_tty->count++;
 439         return 0;
 440 err_free_termios:
 441         if (legacy)
 442                 tty_free_termios(tty);
 443 err_deinit_tty:
 444         deinitialize_tty_struct(o_tty);
 445         free_tty_struct(o_tty);
 446 err_put_module:
 447         module_put(driver->other->owner);
 448 err:
 449         kfree(ports[0]);
 450         kfree(ports[1]);
 451         return retval;
 452 }
 453
 454 static void pty_cleanup(struct tty_struct *tty)
 455 {
 456         tty_port_put(tty->port);
 457 }
 458
 459 /* Traditional BSD devices */
 460 #ifdef CONFIG_LEGACY_PTYS
 461
 462 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 463 {
 464         return pty_common_install(driver, tty, true);
 465 }
 466
 467 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 468 {
 469         struct tty_struct *pair = tty->link;
 470         driver->ttys[tty->index] = NULL;
 471         if (pair)
 472                 pair->driver->ttys[pair->index] = NULL;
 473 }
 474
 475 static int pty_bsd_ioctl(struct tty_struct *tty,
 476                          unsigned int cmd, unsigned long arg)
 477 {
 478         switch (cmd) {
 479         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 480                 return pty_set_lock(tty, (int __user *) arg);
 481         case TIOCGPTLCK: /* Get PT Lock status */
 482                 return pty_get_lock(tty, (int __user *)arg);
 483         case TIOCPKT: /* Set PT packet mode */
 484                 return pty_set_pktmode(tty, (int __user *)arg);
 485         case TIOCGPKT: /* Get PT packet mode */
 486                 return pty_get_pktmode(tty, (int __user *)arg);
 487         case TIOCSIG:    /* Send signal to other side of pty */
 488                 return pty_signal(tty, (int) arg);
 489         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 490                 return -EINVAL;
 491         }
 492         return -ENOIOCTLCMD;
 493 }
 494
 495 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 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 /* We have no need to install and remove our tty objects as devpts does all
 659    the work for us */
 660
 661 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 662 {
 663         return pty_common_install(driver, tty, false);
 664 }
 665
 666 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 667 {
 668 }
 669
 670 /* this is called once with whichever end is closed last */
 671 static void pty_unix98_shutdown(struct tty_struct *tty)
 672 {
 673         devpts_kill_index(tty->driver_data, tty->index);
 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         .shutdown = pty_unix98_shutdown,
 690         .cleanup = pty_cleanup
 691 };
 692
 693 static const struct tty_operations pty_unix98_ops = {
 694         .lookup = pts_unix98_lookup,
 695         .install = pty_unix98_install,
 696         .remove = pty_unix98_remove,
 697         .open = pty_open,
 698         .close = pty_close,
 699         .write = pty_write,
 700         .write_room = pty_write_room,
 701         .flush_buffer = pty_flush_buffer,
 702         .chars_in_buffer = pty_chars_in_buffer,
 703         .unthrottle = pty_unthrottle,
 704         .set_termios = pty_set_termios,
 705         .start = pty_start,
 706         .stop = pty_stop,
 707         .shutdown = pty_unix98_shutdown,
 708         .cleanup = pty_cleanup,
 709 };
 710
 711 /**
 712  *      ptmx_open               -       open a unix 98 pty master
 713  *      @inode: inode of device file
 714  *      @filp: file pointer to tty
 715  *
 716  *      Allocate a unix98 pty master device from the ptmx driver.
 717  *
 718  *      Locking: tty_mutex protects the init_dev work. tty->count should
 719  *              protect the rest.
 720  *              allocated_ptys_lock handles the list of free pty numbers
 721  */
 722
 723 static int ptmx_open(struct inode *inode, struct file *filp)
 724 {
 725         struct tty_struct *tty;
 726         struct inode *slave_inode;
 727         int retval;
 728         int index;
 729
 730         nonseekable_open(inode, filp);
 731
 732         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 733         filp->f_mode |= FMODE_NONOTIFY;
 734
 735         retval = tty_alloc_file(filp);
 736         if (retval)
 737                 return retval;
 738
 739         /* find a device that is not in use. */
 740         mutex_lock(&devpts_mutex);
 741         index = devpts_new_index(inode);
 742         if (index < 0) {
 743                 retval = index;
 744                 mutex_unlock(&devpts_mutex);
 745                 goto err_file;
 746         }
 747
 748         mutex_unlock(&devpts_mutex);
 749
 750         mutex_lock(&tty_mutex);
 751         tty = tty_init_dev(ptm_driver, index);
 752
 753         if (IS_ERR(tty)) {
 754                 retval = PTR_ERR(tty);
 755                 goto out;
 756         }
 757
 758         /* The tty returned here is locked so we can safely
 759            drop the mutex */
 760         mutex_unlock(&tty_mutex);
 761
 762         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 763         tty->driver_data = inode;
 764
 765         tty_add_file(tty, filp);
 766
 767         slave_inode = devpts_pty_new(inode,
 768                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 769                         tty->link);
 770         if (IS_ERR(slave_inode)) {
 771                 retval = PTR_ERR(slave_inode);
 772                 goto err_release;
 773         }
 774         tty->link->driver_data = slave_inode;
 775
 776         retval = ptm_driver->ops->open(tty, filp);
 777         if (retval)
 778                 goto err_release;
 779
 780         tty_unlock(tty);
 781         return 0;
 782 err_release:
 783         tty_unlock(tty);
 784         tty_release(inode, filp);
 785         return retval;
 786 out:
 787         mutex_unlock(&tty_mutex);
 788         devpts_kill_index(inode, index);
 789 err_file:
 790         tty_free_file(filp);
 791         return retval;
 792 }
 793
 794 static struct file_operations ptmx_fops;
 795
 796 static void __init unix98_pty_init(void)
 797 {
 798         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 799                         TTY_DRIVER_RESET_TERMIOS |
 800                         TTY_DRIVER_REAL_RAW |
 801                         TTY_DRIVER_DYNAMIC_DEV |
 802                         TTY_DRIVER_DEVPTS_MEM |
 803                         TTY_DRIVER_DYNAMIC_ALLOC);
 804         if (IS_ERR(ptm_driver))
 805                 panic("Couldn't allocate Unix98 ptm driver");
 806         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 807                         TTY_DRIVER_RESET_TERMIOS |
 808                         TTY_DRIVER_REAL_RAW |
 809                         TTY_DRIVER_DYNAMIC_DEV |
 810                         TTY_DRIVER_DEVPTS_MEM |
 811                         TTY_DRIVER_DYNAMIC_ALLOC);
 812         if (IS_ERR(pts_driver))
 813                 panic("Couldn't allocate Unix98 pts driver");
 814
 815         ptm_driver->driver_name = "pty_master";
 816         ptm_driver->name = "ptm";
 817         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 818         ptm_driver->minor_start = 0;
 819         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 820         ptm_driver->subtype = PTY_TYPE_MASTER;
 821         ptm_driver->init_termios = tty_std_termios;
 822         ptm_driver->init_termios.c_iflag = 0;
 823         ptm_driver->init_termios.c_oflag = 0;
 824         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 825         ptm_driver->init_termios.c_lflag = 0;
 826         ptm_driver->init_termios.c_ispeed = 38400;
 827         ptm_driver->init_termios.c_ospeed = 38400;
 828         ptm_driver->other = pts_driver;
 829         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 830
 831         pts_driver->driver_name = "pty_slave";
 832         pts_driver->name = "pts";
 833         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 834         pts_driver->minor_start = 0;
 835         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 836         pts_driver->subtype = PTY_TYPE_SLAVE;
 837         pts_driver->init_termios = tty_std_termios;
 838         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 839         pts_driver->init_termios.c_ispeed = 38400;
 840         pts_driver->init_termios.c_ospeed = 38400;
 841         pts_driver->other = ptm_driver;
 842         tty_set_operations(pts_driver, &pty_unix98_ops);
 843
 844         if (tty_register_driver(ptm_driver))
 845                 panic("Couldn't register Unix98 ptm driver");
 846         if (tty_register_driver(pts_driver))
 847                 panic("Couldn't register Unix98 pts driver");
 848
 849         /* Now create the /dev/ptmx special device */
 850         tty_default_fops(&ptmx_fops);
 851         ptmx_fops.open = ptmx_open;
 852
 853         cdev_init(&ptmx_cdev, &ptmx_fops);
 854         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 855             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 856                 panic("Couldn't register /dev/ptmx driver");
 857         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 858 }
 859
 860 #else
 861 static inline void unix98_pty_init(void) { }
 862 #endif
 863
 864 static int __init pty_init(void)
 865 {
 866         legacy_pty_init();
 867         unix98_pty_init();
 868         return 0;
 869 }
 870 module_init(pty_init);