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