drivers/char/pty.c

   1 /*
   2  *  linux/drivers/char/pty.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  Added support for a Unix98-style ptmx device.
   7  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
   8  *
   9  *  When reading this code see also fs/devpts. In particular note that the
  10  *  driver_data field is used by the devpts side as a binding to the devpts
  11  *  inode.
  12  */
  13
  14 #include <linux/module.h>
  15
  16 #include <linux/errno.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/tty.h>
  19 #include <linux/tty_flip.h>
  20 #include <linux/fcntl.h>
  21 #include <linux/string.h>
  22 #include <linux/major.h>
  23 #include <linux/mm.h>
  24 #include <linux/init.h>
  25 #include <linux/sysctl.h>
  26 #include <linux/device.h>
  27 #include <linux/uaccess.h>
  28 #include <linux/bitops.h>
  29 #include <linux/devpts_fs.h>
  30
  31 #include <asm/system.h>
  32
  33 #ifdef CONFIG_UNIX98_PTYS
  34 static struct tty_driver *ptm_driver;
  35 static struct tty_driver *pts_driver;
  36 #endif
  37
  38 static void pty_close(struct tty_struct *tty, struct file *filp)
  39 {
  40         BUG_ON(!tty);
  41         if (tty->driver->subtype == PTY_TYPE_MASTER)
  42                 WARN_ON(tty->count > 1);
  43         else {
  44                 if (tty->count > 2)
  45                         return;
  46         }
  47         wake_up_interruptible(&tty->read_wait);
  48         wake_up_interruptible(&tty->write_wait);
  49         tty->packet = 0;
  50         if (!tty->link)
  51                 return;
  52         tty->link->packet = 0;
  53         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  54         wake_up_interruptible(&tty->link->read_wait);
  55         wake_up_interruptible(&tty->link->write_wait);
  56         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  57                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  58 #ifdef CONFIG_UNIX98_PTYS
  59                 if (tty->driver == ptm_driver)
  60                         devpts_pty_kill(tty->link);
  61 #endif
  62                 tty_vhangup(tty->link);
  63         }
  64 }
  65
  66 /*
  67  * The unthrottle routine is called by the line discipline to signal
  68  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  69  * flag is always set, to force the line discipline to always call the
  70  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  71  * characters in the queue.  This is necessary since each time this
  72  * happens, we need to wake up any sleeping processes that could be
  73  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  74  * for the pty buffer to be drained.
  75  */
  76 static void pty_unthrottle(struct tty_struct *tty)
  77 {
  78         struct tty_struct *o_tty = tty->link;
  79
  80         if (!o_tty)
  81                 return;
  82
  83         tty_wakeup(o_tty);
  84         set_bit(TTY_THROTTLED, &tty->flags);
  85 }
  86
  87 /*
  88  * WSH 05/24/97: modified to
  89  *   (1) use space in tty->flip instead of a shared temp buffer
  90  *       The flip buffers aren't being used for a pty, so there's lots
  91  *       of space available.  The buffer is protected by a per-pty
  92  *       semaphore that should almost never come under contention.
  93  *   (2) avoid redundant copying for cases where count >> receive_room
  94  * N.B. Calls from user space may now return an error code instead of
  95  * a count.
  96  *
  97  * FIXME: Our pty_write method is called with our ldisc lock held but
  98  * not our partners. We can't just wait on the other one blindly without
  99  * risking deadlocks. At some point when everything has settled down we need
 100  * to look into making pty_write at least able to sleep over an ldisc change.
 101  *
 102  * The return on no ldisc is a bit counter intuitive but the logic works
 103  * like this. During an ldisc change the other end will flush its buffers. We
 104  * thus return the full length which is identical to the case where we had
 105  * proper locking and happened to queue the bytes just before the flush during
 106  * the ldisc change.
 107  */
 108 static int pty_write(struct tty_struct *tty, const unsigned char *buf,
 109                                                                 int count)
 110 {
 111         struct tty_struct *to = tty->link;
 112         struct tty_ldisc *ld;
 113         int c = count;
 114
 115         if (!to || tty->stopped)
 116                 return 0;
 117         ld = tty_ldisc_ref(to);
 118
 119         if (ld) {
 120                 c = to->receive_room;
 121                 if (c > count)
 122                         c = count;
 123                 ld->ops->receive_buf(to, buf, NULL, c);
 124                 tty_ldisc_deref(ld);
 125         }
 126         return c;
 127 }
 128
 129 static int pty_write_room(struct tty_struct *tty)
 130 {
 131         struct tty_struct *to = tty->link;
 132
 133         if (!to || tty->stopped)
 134                 return 0;
 135
 136         return to->receive_room;
 137 }
 138
 139 /*
 140  *      WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior
 141  *      The chars_in_buffer() value is used by the ldisc select() function
 142  *      to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
 143  *      The pty driver chars_in_buffer() Master/Slave must behave differently:
 144  *
 145  *      The Master side needs to allow typed-ahead commands to accumulate
 146  *      while being canonicalized, so we report "our buffer" as empty until
 147  *      some threshold is reached, and then report the count. (Any count >
 148  *      WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock
 149  *      the count returned must be 0 if no canonical data is available to be
 150  *      read. (The N_TTY ldisc.chars_in_buffer now knows this.)
 151  *
 152  *      The Slave side passes all characters in raw mode to the Master side's
 153  *      buffer where they can be read immediately, so in this case we can
 154  *      return the true count in the buffer.
 155  */
 156 static int pty_chars_in_buffer(struct tty_struct *tty)
 157 {
 158         struct tty_struct *to = tty->link;
 159         struct tty_ldisc *ld;
 160         int count = 0;
 161
 162         /* We should get the line discipline lock for "tty->link" */
 163         if (!to)
 164                 return 0;
 165         /* We cannot take a sleeping reference here without deadlocking with
 166            an ldisc change - but it doesn't really matter */
 167         ld = tty_ldisc_ref(to);
 168         if (ld == NULL)
 169                 return 0;
 170
 171         /* The ldisc must report 0 if no characters available to be read */
 172         if (ld->ops->chars_in_buffer)
 173                 count = ld->ops->chars_in_buffer(to);
 174
 175         tty_ldisc_deref(ld);
 176
 177         if (tty->driver->subtype == PTY_TYPE_SLAVE)
 178                 return count;
 179
 180         /* Master side driver ... if the other side's read buffer is less than
 181          * half full, return 0 to allow writers to proceed; otherwise return
 182          * the count.  This leaves a comfortable margin to avoid overflow,
 183          * and still allows half a buffer's worth of typed-ahead commands.
 184          */
 185         return (count < N_TTY_BUF_SIZE/2) ? 0 : count;
 186 }
 187
 188 /* Set the lock flag on a pty */
 189 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 190 {
 191         int val;
 192         if (get_user(val, arg))
 193                 return -EFAULT;
 194         if (val)
 195                 set_bit(TTY_PTY_LOCK, &tty->flags);
 196         else
 197                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 198         return 0;
 199 }
 200
 201 static void pty_flush_buffer(struct tty_struct *tty)
 202 {
 203         struct tty_struct *to = tty->link;
 204         unsigned long flags;
 205         struct tty_ldisc *ld;
 206
 207         if (!to)
 208                 return;
 209         ld = tty_ldisc_ref(to);
 210
 211         /* The other end is changing discipline */
 212         if (!ld)
 213                 return;
 214
 215         if (ld->ops->flush_buffer)
 216                 to->ldisc->ops->flush_buffer(to);
 217         tty_ldisc_deref(ld);
 218
 219         if (to->packet) {
 220                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 221                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 222                 wake_up_interruptible(&to->read_wait);
 223                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 224         }
 225 }
 226
 227 static int pty_open(struct tty_struct *tty, struct file *filp)
 228 {
 229         int     retval = -ENODEV;
 230
 231         if (!tty || !tty->link)
 232                 goto out;
 233
 234         retval = -EIO;
 235         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 236                 goto out;
 237         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 238                 goto out;
 239         if (tty->link->count != 1)
 240                 goto out;
 241
 242         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 243         set_bit(TTY_THROTTLED, &tty->flags);
 244         retval = 0;
 245 out:
 246         return retval;
 247 }
 248
 249 static void pty_set_termios(struct tty_struct *tty,
 250                                         struct ktermios *old_termios)
 251 {
 252         tty->termios->c_cflag &= ~(CSIZE | PARENB);
 253         tty->termios->c_cflag |= (CS8 | CREAD);
 254 }
 255
 256 /**
 257  *      pty_do_resize           -       resize event
 258  *      @tty: tty being resized
 259  *      @ws: window size being set.
 260  *
 261  *      Update the termios variables and send the neccessary signals to
 262  *      peform a terminal resize correctly
 263  */
 264
 265 int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 266 {
 267         struct pid *pgrp, *rpgrp;
 268         unsigned long flags;
 269         struct tty_struct *pty = tty->link;
 270
 271         /* For a PTY we need to lock the tty side */
 272         mutex_lock(&tty->termios_mutex);
 273         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 274                 goto done;
 275
 276         /* Get the PID values and reference them so we can
 277            avoid holding the tty ctrl lock while sending signals.
 278            We need to lock these individually however. */
 279
 280         spin_lock_irqsave(&tty->ctrl_lock, flags);
 281         pgrp = get_pid(tty->pgrp);
 282         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 283
 284         spin_lock_irqsave(&pty->ctrl_lock, flags);
 285         rpgrp = get_pid(pty->pgrp);
 286         spin_unlock_irqrestore(&pty->ctrl_lock, flags);
 287
 288         if (pgrp)
 289                 kill_pgrp(pgrp, SIGWINCH, 1);
 290         if (rpgrp != pgrp && rpgrp)
 291                 kill_pgrp(rpgrp, SIGWINCH, 1);
 292
 293         put_pid(pgrp);
 294         put_pid(rpgrp);
 295
 296         tty->winsize = *ws;
 297         pty->winsize = *ws;     /* Never used so will go away soon */
 298 done:
 299         mutex_unlock(&tty->termios_mutex);
 300         return 0;
 301 }
 302
 303 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 304 {
 305         struct tty_struct *o_tty;
 306         int idx = tty->index;
 307         int retval;
 308
 309         o_tty = alloc_tty_struct();
 310         if (!o_tty)
 311                 return -ENOMEM;
 312         if (!try_module_get(driver->other->owner)) {
 313                 /* This cannot in fact currently happen */
 314                 free_tty_struct(o_tty);
 315                 return -ENOMEM;
 316         }
 317         initialize_tty_struct(o_tty, driver->other, idx);
 318
 319         /* We always use new tty termios data so we can do this
 320            the easy way .. */
 321         retval = tty_init_termios(tty);
 322         if (retval)
 323                 goto free_mem_out;
 324
 325         retval = tty_init_termios(o_tty);
 326         if (retval) {
 327                 tty_free_termios(tty);
 328                 goto free_mem_out;
 329         }
 330
 331         /*
 332          * Everything allocated ... set up the o_tty structure.
 333          */
 334         driver->other->ttys[idx] = o_tty;
 335         tty_driver_kref_get(driver->other);
 336         if (driver->subtype == PTY_TYPE_MASTER)
 337                 o_tty->count++;
 338         /* Establish the links in both directions */
 339         tty->link   = o_tty;
 340         o_tty->link = tty;
 341
 342         tty_driver_kref_get(driver);
 343         tty->count++;
 344         driver->ttys[idx] = tty;
 345         return 0;
 346 free_mem_out:
 347         module_put(o_tty->driver->owner);
 348         free_tty_struct(o_tty);
 349         return -ENOMEM;
 350 }
 351
 352
 353 static const struct tty_operations pty_ops = {
 354         .install = pty_install,
 355         .open = pty_open,
 356         .close = pty_close,
 357         .write = pty_write,
 358         .write_room = pty_write_room,
 359         .flush_buffer = pty_flush_buffer,
 360         .chars_in_buffer = pty_chars_in_buffer,
 361         .unthrottle = pty_unthrottle,
 362         .set_termios = pty_set_termios,
 363         .resize = pty_resize
 364 };
 365
 366 /* Traditional BSD devices */
 367 #ifdef CONFIG_LEGACY_PTYS
 368 static struct tty_driver *pty_driver, *pty_slave_driver;
 369
 370 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
 371                          unsigned int cmd, unsigned long arg)
 372 {
 373         switch (cmd) {
 374         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 375                 return pty_set_lock(tty, (int __user *) arg);
 376         }
 377         return -ENOIOCTLCMD;
 378 }
 379
 380 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 381 module_param(legacy_count, int, 0);
 382
 383 static const struct tty_operations pty_ops_bsd = {
 384         .open = pty_open,
 385         .close = pty_close,
 386         .write = pty_write,
 387         .write_room = pty_write_room,
 388         .flush_buffer = pty_flush_buffer,
 389         .chars_in_buffer = pty_chars_in_buffer,
 390         .unthrottle = pty_unthrottle,
 391         .set_termios = pty_set_termios,
 392         .ioctl = pty_bsd_ioctl,
 393         .resize = pty_resize
 394 };
 395
 396 static void __init legacy_pty_init(void)
 397 {
 398         if (legacy_count <= 0)
 399                 return;
 400
 401         pty_driver = alloc_tty_driver(legacy_count);
 402         if (!pty_driver)
 403                 panic("Couldn't allocate pty driver");
 404
 405         pty_slave_driver = alloc_tty_driver(legacy_count);
 406         if (!pty_slave_driver)
 407                 panic("Couldn't allocate pty slave driver");
 408
 409         pty_driver->owner = THIS_MODULE;
 410         pty_driver->driver_name = "pty_master";
 411         pty_driver->name = "pty";
 412         pty_driver->major = PTY_MASTER_MAJOR;
 413         pty_driver->minor_start = 0;
 414         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 415         pty_driver->subtype = PTY_TYPE_MASTER;
 416         pty_driver->init_termios = tty_std_termios;
 417         pty_driver->init_termios.c_iflag = 0;
 418         pty_driver->init_termios.c_oflag = 0;
 419         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 420         pty_driver->init_termios.c_lflag = 0;
 421         pty_driver->init_termios.c_ispeed = 38400;
 422         pty_driver->init_termios.c_ospeed = 38400;
 423         pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
 424         pty_driver->other = pty_slave_driver;
 425         tty_set_operations(pty_driver, &pty_ops);
 426
 427         pty_slave_driver->owner = THIS_MODULE;
 428         pty_slave_driver->driver_name = "pty_slave";
 429         pty_slave_driver->name = "ttyp";
 430         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 431         pty_slave_driver->minor_start = 0;
 432         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 433         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 434         pty_slave_driver->init_termios = tty_std_termios;
 435         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 436         pty_slave_driver->init_termios.c_ispeed = 38400;
 437         pty_slave_driver->init_termios.c_ospeed = 38400;
 438         pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
 439                                         TTY_DRIVER_REAL_RAW;
 440         pty_slave_driver->other = pty_driver;
 441         tty_set_operations(pty_slave_driver, &pty_ops);
 442
 443         if (tty_register_driver(pty_driver))
 444                 panic("Couldn't register pty driver");
 445         if (tty_register_driver(pty_slave_driver))
 446                 panic("Couldn't register pty slave driver");
 447 }
 448 #else
 449 static inline void legacy_pty_init(void) { }
 450 #endif
 451
 452 /* Unix98 devices */
 453 #ifdef CONFIG_UNIX98_PTYS
 454 /*
 455  * sysctl support for setting limits on the number of Unix98 ptys allocated.
 456  * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
 457  */
 458 int pty_limit = NR_UNIX98_PTY_DEFAULT;
 459 static int pty_limit_min;
 460 static int pty_limit_max = NR_UNIX98_PTY_MAX;
 461 static int pty_count;
 462
 463 static struct cdev ptmx_cdev;
 464
 465 static struct ctl_table pty_table[] = {
 466         {
 467                 .ctl_name       = PTY_MAX,
 468                 .procname       = "max",
 469                 .maxlen         = sizeof(int),
 470                 .mode           = 0644,
 471                 .data           = &pty_limit,
 472                 .proc_handler   = &proc_dointvec_minmax,
 473                 .strategy       = &sysctl_intvec,
 474                 .extra1         = &pty_limit_min,
 475                 .extra2         = &pty_limit_max,
 476         }, {
 477                 .ctl_name       = PTY_NR,
 478                 .procname       = "nr",
 479                 .maxlen         = sizeof(int),
 480                 .mode           = 0444,
 481                 .data           = &pty_count,
 482                 .proc_handler   = &proc_dointvec,
 483         }, {
 484                 .ctl_name       = 0
 485         }
 486 };
 487
 488 static struct ctl_table pty_kern_table[] = {
 489         {
 490                 .ctl_name       = KERN_PTY,
 491                 .procname       = "pty",
 492                 .mode           = 0555,
 493                 .child          = pty_table,
 494         },
 495         {}
 496 };
 497
 498 static struct ctl_table pty_root_table[] = {
 499         {
 500                 .ctl_name       = CTL_KERN,
 501                 .procname       = "kernel",
 502                 .mode           = 0555,
 503                 .child          = pty_kern_table,
 504         },
 505         {}
 506 };
 507
 508
 509 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
 510                             unsigned int cmd, unsigned long arg)
 511 {
 512         switch (cmd) {
 513         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 514                 return pty_set_lock(tty, (int __user *)arg);
 515         case TIOCGPTN: /* Get PT Number */
 516                 return put_user(tty->index, (unsigned int __user *)arg);
 517         }
 518
 519         return -ENOIOCTLCMD;
 520 }
 521
 522 /**
 523  *      ptm_unix98_lookup       -       find a pty master
 524  *      @driver: ptm driver
 525  *      @idx: tty index
 526  *
 527  *      Look up a pty master device. Called under the tty_mutex for now.
 528  *      This provides our locking.
 529  */
 530
 531 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 532                 struct inode *ptm_inode, int idx)
 533 {
 534         struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
 535         if (tty)
 536                 tty = tty->link;
 537         return tty;
 538 }
 539
 540 /**
 541  *      pts_unix98_lookup       -       find a pty slave
 542  *      @driver: pts driver
 543  *      @idx: tty index
 544  *
 545  *      Look up a pty master device. Called under the tty_mutex for now.
 546  *      This provides our locking.
 547  */
 548
 549 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 550                 struct inode *pts_inode, int idx)
 551 {
 552         struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
 553         /* Master must be open before slave */
 554         if (!tty)
 555                 return ERR_PTR(-EIO);
 556         return tty;
 557 }
 558
 559 static void pty_unix98_shutdown(struct tty_struct *tty)
 560 {
 561         /* We have our own method as we don't use the tty index */
 562         kfree(tty->termios);
 563 }
 564
 565 /* We have no need to install and remove our tty objects as devpts does all
 566    the work for us */
 567
 568 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 569 {
 570         struct tty_struct *o_tty;
 571         int idx = tty->index;
 572
 573         o_tty = alloc_tty_struct();
 574         if (!o_tty)
 575                 return -ENOMEM;
 576         if (!try_module_get(driver->other->owner)) {
 577                 /* This cannot in fact currently happen */
 578                 free_tty_struct(o_tty);
 579                 return -ENOMEM;
 580         }
 581         initialize_tty_struct(o_tty, driver->other, idx);
 582
 583         tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
 584         if (tty->termios == NULL)
 585                 goto free_mem_out;
 586         *tty->termios = driver->init_termios;
 587         tty->termios_locked = tty->termios + 1;
 588
 589         o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
 590         if (o_tty->termios == NULL)
 591                 goto free_mem_out;
 592         *o_tty->termios = driver->other->init_termios;
 593         o_tty->termios_locked = o_tty->termios + 1;
 594
 595         tty_driver_kref_get(driver->other);
 596         if (driver->subtype == PTY_TYPE_MASTER)
 597                 o_tty->count++;
 598         /* Establish the links in both directions */
 599         tty->link   = o_tty;
 600         o_tty->link = tty;
 601         /*
 602          * All structures have been allocated, so now we install them.
 603          * Failures after this point use release_tty to clean up, so
 604          * there's no need to null out the local pointers.
 605          */
 606         tty_driver_kref_get(driver);
 607         tty->count++;
 608         pty_count++;
 609         return 0;
 610 free_mem_out:
 611         kfree(o_tty->termios);
 612         module_put(o_tty->driver->owner);
 613         free_tty_struct(o_tty);
 614         kfree(tty->termios);
 615         return -ENOMEM;
 616 }
 617
 618 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 619 {
 620         pty_count--;
 621 }
 622
 623 static const struct tty_operations ptm_unix98_ops = {
 624         .lookup = ptm_unix98_lookup,
 625         .install = pty_unix98_install,
 626         .remove = pty_unix98_remove,
 627         .open = pty_open,
 628         .close = pty_close,
 629         .write = pty_write,
 630         .write_room = pty_write_room,
 631         .flush_buffer = pty_flush_buffer,
 632         .chars_in_buffer = pty_chars_in_buffer,
 633         .unthrottle = pty_unthrottle,
 634         .set_termios = pty_set_termios,
 635         .ioctl = pty_unix98_ioctl,
 636         .shutdown = pty_unix98_shutdown,
 637         .resize = pty_resize
 638 };
 639
 640 static const struct tty_operations pty_unix98_ops = {
 641         .lookup = pts_unix98_lookup,
 642         .install = pty_unix98_install,
 643         .remove = pty_unix98_remove,
 644         .open = pty_open,
 645         .close = pty_close,
 646         .write = pty_write,
 647         .write_room = pty_write_room,
 648         .flush_buffer = pty_flush_buffer,
 649         .chars_in_buffer = pty_chars_in_buffer,
 650         .unthrottle = pty_unthrottle,
 651         .set_termios = pty_set_termios,
 652         .shutdown = pty_unix98_shutdown
 653 };
 654
 655 /**
 656  *      ptmx_open               -       open a unix 98 pty master
 657  *      @inode: inode of device file
 658  *      @filp: file pointer to tty
 659  *
 660  *      Allocate a unix98 pty master device from the ptmx driver.
 661  *
 662  *      Locking: tty_mutex protects the init_dev work. tty->count should
 663  *              protect the rest.
 664  *              allocated_ptys_lock handles the list of free pty numbers
 665  */
 666
 667 static int __ptmx_open(struct inode *inode, struct file *filp)
 668 {
 669         struct tty_struct *tty;
 670         int retval;
 671         int index;
 672
 673         nonseekable_open(inode, filp);
 674
 675         /* find a device that is not in use. */
 676         index = devpts_new_index(inode);
 677         if (index < 0)
 678                 return index;
 679
 680         mutex_lock(&tty_mutex);
 681         tty = tty_init_dev(ptm_driver, index, 1);
 682         mutex_unlock(&tty_mutex);
 683
 684         if (IS_ERR(tty)) {
 685                 retval = PTR_ERR(tty);
 686                 goto out;
 687         }
 688
 689         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 690         filp->private_data = tty;
 691         file_move(filp, &tty->tty_files);
 692
 693         retval = devpts_pty_new(inode, tty->link);
 694         if (retval)
 695                 goto out1;
 696
 697         retval = ptm_driver->ops->open(tty, filp);
 698         if (!retval)
 699                 return 0;
 700 out1:
 701         tty_release_dev(filp);
 702         return retval;
 703 out:
 704         devpts_kill_index(inode, index);
 705         return retval;
 706 }
 707
 708 static int ptmx_open(struct inode *inode, struct file *filp)
 709 {
 710         int ret;
 711
 712         lock_kernel();
 713         ret = __ptmx_open(inode, filp);
 714         unlock_kernel();
 715         return ret;
 716 }
 717
 718 static struct file_operations ptmx_fops;
 719
 720 static void __init unix98_pty_init(void)
 721 {
 722         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 723         if (!ptm_driver)
 724                 panic("Couldn't allocate Unix98 ptm driver");
 725         pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
 726         if (!pts_driver)
 727                 panic("Couldn't allocate Unix98 pts driver");
 728
 729         ptm_driver->owner = THIS_MODULE;
 730         ptm_driver->driver_name = "pty_master";
 731         ptm_driver->name = "ptm";
 732         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 733         ptm_driver->minor_start = 0;
 734         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 735         ptm_driver->subtype = PTY_TYPE_MASTER;
 736         ptm_driver->init_termios = tty_std_termios;
 737         ptm_driver->init_termios.c_iflag = 0;
 738         ptm_driver->init_termios.c_oflag = 0;
 739         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 740         ptm_driver->init_termios.c_lflag = 0;
 741         ptm_driver->init_termios.c_ispeed = 38400;
 742         ptm_driver->init_termios.c_ospeed = 38400;
 743         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 744                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 745         ptm_driver->other = pts_driver;
 746         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 747
 748         pts_driver->owner = THIS_MODULE;
 749         pts_driver->driver_name = "pty_slave";
 750         pts_driver->name = "pts";
 751         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 752         pts_driver->minor_start = 0;
 753         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 754         pts_driver->subtype = PTY_TYPE_SLAVE;
 755         pts_driver->init_termios = tty_std_termios;
 756         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 757         pts_driver->init_termios.c_ispeed = 38400;
 758         pts_driver->init_termios.c_ospeed = 38400;
 759         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
 760                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 761         pts_driver->other = ptm_driver;
 762         tty_set_operations(pts_driver, &pty_unix98_ops);
 763
 764         if (tty_register_driver(ptm_driver))
 765                 panic("Couldn't register Unix98 ptm driver");
 766         if (tty_register_driver(pts_driver))
 767                 panic("Couldn't register Unix98 pts driver");
 768
 769         register_sysctl_table(pty_root_table);
 770
 771         /* Now create the /dev/ptmx special device */
 772         tty_default_fops(&ptmx_fops);
 773         ptmx_fops.open = ptmx_open;
 774
 775         cdev_init(&ptmx_cdev, &ptmx_fops);
 776         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 777             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 778                 panic("Couldn't register /dev/ptmx driver\n");
 779         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 780 }
 781
 782 #else
 783 static inline void unix98_pty_init(void) { }
 784 #endif
 785
 786 static int __init pty_init(void)
 787 {
 788         legacy_pty_init();
 789         unix98_pty_init();
 790         return 0;
 791 }
 792 module_init(pty_init);