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
  28
  29 #ifdef CONFIG_UNIX98_PTYS
  30 static struct tty_driver *ptm_driver;
  31 static struct tty_driver *pts_driver;
  32 static DEFINE_MUTEX(devpts_mutex);
  33 #endif
  34
  35 static void pty_close(struct tty_struct *tty, struct file *filp)
  36 {
  37         BUG_ON(!tty);
  38         if (tty->driver->subtype == PTY_TYPE_MASTER)
  39                 WARN_ON(tty->count > 1);
  40         else {
  41                 if (tty->count > 2)
  42                         return;
  43         }
  44         wake_up_interruptible(&tty->read_wait);
  45         wake_up_interruptible(&tty->write_wait);
  46         tty->packet = 0;
  47         /* Review - krefs on tty_link ?? */
  48         if (!tty->link)
  49                 return;
  50         tty->link->packet = 0;
  51         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  52         wake_up_interruptible(&tty->link->read_wait);
  53         wake_up_interruptible(&tty->link->write_wait);
  54         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  55                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  56 #ifdef CONFIG_UNIX98_PTYS
  57                 if (tty->driver == ptm_driver) {
  58                         mutex_lock(&devpts_mutex);
  59                         devpts_pty_kill(tty->link->driver_data);
  60                         mutex_unlock(&devpts_mutex);
  61                 }
  62 #endif
  63                 tty_unlock(tty);
  64                 tty_vhangup(tty->link);
  65                 tty_lock(tty);
  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         tty_wakeup(tty->link);
  82         set_bit(TTY_THROTTLED, &tty->flags);
  83 }
  84
  85 /**
  86  *      pty_space       -       report space left for writing
  87  *      @to: tty we are writing into
  88  *
  89  *      The tty buffers allow 64K but we sneak a peak and clip at 8K this
  90  *      allows a lot of overspill room for echo and other fun messes to
  91  *      be handled properly
  92  */
  93
  94 static int pty_space(struct tty_struct *to)
  95 {
  96         int n = 8192 - to->port->buf.memory_used;
  97         if (n < 0)
  98                 return 0;
  99         return n;
 100 }
 101
 102 /**
 103  *      pty_write               -       write to a pty
 104  *      @tty: the tty we write from
 105  *      @buf: kernel buffer of data
 106  *      @count: bytes to write
 107  *
 108  *      Our "hardware" write method. Data is coming from the ldisc which
 109  *      may be in a non sleeping state. We simply throw this at the other
 110  *      end of the link as if we were an IRQ handler receiving stuff for
 111  *      the other side of the pty/tty pair.
 112  */
 113
 114 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 115 {
 116         struct tty_struct *to = tty->link;
 117
 118         if (tty->stopped)
 119                 return 0;
 120
 121         if (c > 0) {
 122                 /* Stuff the data into the input queue of the other end */
 123                 c = tty_insert_flip_string(to->port, buf, c);
 124                 /* And shovel */
 125                 if (c) {
 126                         tty_flip_buffer_push(to->port);
 127                         tty_wakeup(tty);
 128                 }
 129         }
 130         return c;
 131 }
 132
 133 /**
 134  *      pty_write_room  -       write space
 135  *      @tty: tty we are writing from
 136  *
 137  *      Report how many bytes the ldisc can send into the queue for
 138  *      the other device.
 139  */
 140
 141 static int pty_write_room(struct tty_struct *tty)
 142 {
 143         if (tty->stopped)
 144                 return 0;
 145         return pty_space(tty->link);
 146 }
 147
 148 /**
 149  *      pty_chars_in_buffer     -       characters currently in our tx queue
 150  *      @tty: our tty
 151  *
 152  *      Report how much we have in the transmit queue. As everything is
 153  *      instantly at the other end this is easy to implement.
 154  */
 155
 156 static int pty_chars_in_buffer(struct tty_struct *tty)
 157 {
 158         return 0;
 159 }
 160
 161 /* Set the lock flag on a pty */
 162 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 163 {
 164         int val;
 165         if (get_user(val, arg))
 166                 return -EFAULT;
 167         if (val)
 168                 set_bit(TTY_PTY_LOCK, &tty->flags);
 169         else
 170                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 171         return 0;
 172 }
 173
 174 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 175 {
 176         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 177         return put_user(locked, arg);
 178 }
 179
 180 /* Set the packet mode on a pty */
 181 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 182 {
 183         unsigned long flags;
 184         int pktmode;
 185
 186         if (get_user(pktmode, arg))
 187                 return -EFAULT;
 188
 189         spin_lock_irqsave(&tty->ctrl_lock, flags);
 190         if (pktmode) {
 191                 if (!tty->packet) {
 192                         tty->packet = 1;
 193                         tty->link->ctrl_status = 0;
 194                 }
 195         } else
 196                 tty->packet = 0;
 197         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 198
 199         return 0;
 200 }
 201
 202 /* Get the packet mode of a pty */
 203 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 204 {
 205         int pktmode = tty->packet;
 206         return put_user(pktmode, arg);
 207 }
 208
 209 /* Send a signal to the slave */
 210 static int pty_signal(struct tty_struct *tty, int sig)
 211 {
 212         unsigned long flags;
 213         struct pid *pgrp;
 214
 215         if (tty->link) {
 216                 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
 217                 pgrp = get_pid(tty->link->pgrp);
 218                 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
 219
 220                 kill_pgrp(pgrp, sig, 1);
 221                 put_pid(pgrp);
 222         }
 223         return 0;
 224 }
 225
 226 static void pty_flush_buffer(struct tty_struct *tty)
 227 {
 228         struct tty_struct *to = tty->link;
 229         unsigned long flags;
 230
 231         if (!to)
 232                 return;
 233         /* tty_buffer_flush(to); FIXME */
 234         if (to->packet) {
 235                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 236                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 237                 wake_up_interruptible(&to->read_wait);
 238                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 239         }
 240 }
 241
 242 static int pty_open(struct tty_struct *tty, struct file *filp)
 243 {
 244         int     retval = -ENODEV;
 245
 246         if (!tty || !tty->link)
 247                 goto out;
 248
 249         retval = -EIO;
 250         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 251                 goto out;
 252         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 253                 goto out;
 254         if (tty->link->count != 1)
 255                 goto out;
 256
 257         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 258         set_bit(TTY_THROTTLED, &tty->flags);
 259         retval = 0;
 260 out:
 261         return retval;
 262 }
 263
 264 static void pty_set_termios(struct tty_struct *tty,
 265                                         struct ktermios *old_termios)
 266 {
 267         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 268         tty->termios.c_cflag |= (CS8 | CREAD);
 269 }
 270
 271 /**
 272  *      pty_do_resize           -       resize event
 273  *      @tty: tty being resized
 274  *      @ws: window size being set.
 275  *
 276  *      Update the termios variables and send the necessary signals to
 277  *      peform a terminal resize correctly
 278  */
 279
 280 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 281 {
 282         struct pid *pgrp, *rpgrp;
 283         unsigned long flags;
 284         struct tty_struct *pty = tty->link;
 285
 286         /* For a PTY we need to lock the tty side */
 287         mutex_lock(&tty->termios_mutex);
 288         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 289                 goto done;
 290
 291         /* Get the PID values and reference them so we can
 292            avoid holding the tty ctrl lock while sending signals.
 293            We need to lock these individually however. */
 294
 295         spin_lock_irqsave(&tty->ctrl_lock, flags);
 296         pgrp = get_pid(tty->pgrp);
 297         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 298
 299         spin_lock_irqsave(&pty->ctrl_lock, flags);
 300         rpgrp = get_pid(pty->pgrp);
 301         spin_unlock_irqrestore(&pty->ctrl_lock, flags);
 302
 303         if (pgrp)
 304                 kill_pgrp(pgrp, SIGWINCH, 1);
 305         if (rpgrp != pgrp && rpgrp)
 306                 kill_pgrp(rpgrp, SIGWINCH, 1);
 307
 308         put_pid(pgrp);
 309         put_pid(rpgrp);
 310
 311         tty->winsize = *ws;
 312         pty->winsize = *ws;     /* Never used so will go away soon */
 313 done:
 314         mutex_unlock(&tty->termios_mutex);
 315         return 0;
 316 }
 317
 318 /**
 319  *      pty_common_install              -       set up the pty pair
 320  *      @driver: the pty driver
 321  *      @tty: the tty being instantiated
 322  *      @bool: legacy, true if this is BSD style
 323  *
 324  *      Perform the initial set up for the tty/pty pair. Called from the
 325  *      tty layer when the port is first opened.
 326  *
 327  *      Locking: the caller must hold the tty_mutex
 328  */
 329 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 330                 bool legacy)
 331 {
 332         struct tty_struct *o_tty;
 333         struct tty_port *ports[2];
 334         int idx = tty->index;
 335         int retval = -ENOMEM;
 336
 337         o_tty = alloc_tty_struct();
 338         if (!o_tty)
 339                 goto err;
 340         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 341         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 342         if (!ports[0] || !ports[1])
 343                 goto err_free_tty;
 344         if (!try_module_get(driver->other->owner)) {
 345                 /* This cannot in fact currently happen */
 346                 goto err_free_tty;
 347         }
 348         initialize_tty_struct(o_tty, driver->other, idx);
 349
 350         if (legacy) {
 351                 /* We always use new tty termios data so we can do this
 352                    the easy way .. */
 353                 retval = tty_init_termios(tty);
 354                 if (retval)
 355                         goto err_deinit_tty;
 356
 357                 retval = tty_init_termios(o_tty);
 358                 if (retval)
 359                         goto err_free_termios;
 360
 361                 driver->other->ttys[idx] = o_tty;
 362                 driver->ttys[idx] = tty;
 363         } else {
 364                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 365                 tty->termios = driver->init_termios;
 366                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 367                 o_tty->termios = driver->other->init_termios;
 368         }
 369
 370         /*
 371          * Everything allocated ... set up the o_tty structure.
 372          */
 373         tty_driver_kref_get(driver->other);
 374         if (driver->subtype == PTY_TYPE_MASTER)
 375                 o_tty->count++;
 376         /* Establish the links in both directions */
 377         tty->link   = o_tty;
 378         o_tty->link = tty;
 379         tty_port_init(ports[0]);
 380         tty_port_init(ports[1]);
 381         o_tty->port = ports[0];
 382         tty->port = ports[1];
 383         o_tty->port->itty = o_tty;
 384
 385         tty_driver_kref_get(driver);
 386         tty->count++;
 387         return 0;
 388 err_free_termios:
 389         if (legacy)
 390                 tty_free_termios(tty);
 391 err_deinit_tty:
 392         deinitialize_tty_struct(o_tty);
 393         module_put(o_tty->driver->owner);
 394 err_free_tty:
 395         kfree(ports[0]);
 396         kfree(ports[1]);
 397         free_tty_struct(o_tty);
 398 err:
 399         return retval;
 400 }
 401
 402 /* this is called once with whichever end is closed last */
 403 static void pty_unix98_shutdown(struct tty_struct *tty)
 404 {
 405         devpts_kill_index(tty->driver_data, tty->index);
 406 }
 407
 408 static void pty_cleanup(struct tty_struct *tty)
 409 {
 410         tty->port->itty = NULL;
 411         tty_port_put(tty->port);
 412 }
 413
 414 /* Traditional BSD devices */
 415 #ifdef CONFIG_LEGACY_PTYS
 416
 417 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 418 {
 419         return pty_common_install(driver, tty, true);
 420 }
 421
 422 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 423 {
 424         struct tty_struct *pair = tty->link;
 425         driver->ttys[tty->index] = NULL;
 426         if (pair)
 427                 pair->driver->ttys[pair->index] = NULL;
 428 }
 429
 430 static int pty_bsd_ioctl(struct tty_struct *tty,
 431                          unsigned int cmd, unsigned long arg)
 432 {
 433         switch (cmd) {
 434         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 435                 return pty_set_lock(tty, (int __user *) arg);
 436         case TIOCGPTLCK: /* Get PT Lock status */
 437                 return pty_get_lock(tty, (int __user *)arg);
 438         case TIOCPKT: /* Set PT packet mode */
 439                 return pty_set_pktmode(tty, (int __user *)arg);
 440         case TIOCGPKT: /* Get PT packet mode */
 441                 return pty_get_pktmode(tty, (int __user *)arg);
 442         case TIOCSIG:    /* Send signal to other side of pty */
 443                 return pty_signal(tty, (int) arg);
 444         }
 445         return -ENOIOCTLCMD;
 446 }
 447
 448 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 449 module_param(legacy_count, int, 0);
 450
 451 /*
 452  * The master side of a pty can do TIOCSPTLCK and thus
 453  * has pty_bsd_ioctl.
 454  */
 455 static const struct tty_operations master_pty_ops_bsd = {
 456         .install = pty_install,
 457         .open = pty_open,
 458         .close = pty_close,
 459         .write = pty_write,
 460         .write_room = pty_write_room,
 461         .flush_buffer = pty_flush_buffer,
 462         .chars_in_buffer = pty_chars_in_buffer,
 463         .unthrottle = pty_unthrottle,
 464         .set_termios = pty_set_termios,
 465         .ioctl = pty_bsd_ioctl,
 466         .cleanup = pty_cleanup,
 467         .resize = pty_resize,
 468         .remove = pty_remove
 469 };
 470
 471 static const struct tty_operations slave_pty_ops_bsd = {
 472         .install = pty_install,
 473         .open = pty_open,
 474         .close = pty_close,
 475         .write = pty_write,
 476         .write_room = pty_write_room,
 477         .flush_buffer = pty_flush_buffer,
 478         .chars_in_buffer = pty_chars_in_buffer,
 479         .unthrottle = pty_unthrottle,
 480         .set_termios = pty_set_termios,
 481         .cleanup = pty_cleanup,
 482         .resize = pty_resize,
 483         .remove = pty_remove
 484 };
 485
 486 static void __init legacy_pty_init(void)
 487 {
 488         struct tty_driver *pty_driver, *pty_slave_driver;
 489
 490         if (legacy_count <= 0)
 491                 return;
 492
 493         pty_driver = tty_alloc_driver(legacy_count,
 494                         TTY_DRIVER_RESET_TERMIOS |
 495                         TTY_DRIVER_REAL_RAW |
 496                         TTY_DRIVER_DYNAMIC_ALLOC);
 497         if (IS_ERR(pty_driver))
 498                 panic("Couldn't allocate pty driver");
 499
 500         pty_slave_driver = tty_alloc_driver(legacy_count,
 501                         TTY_DRIVER_RESET_TERMIOS |
 502                         TTY_DRIVER_REAL_RAW |
 503                         TTY_DRIVER_DYNAMIC_ALLOC);
 504         if (IS_ERR(pty_slave_driver))
 505                 panic("Couldn't allocate pty slave driver");
 506
 507         pty_driver->driver_name = "pty_master";
 508         pty_driver->name = "pty";
 509         pty_driver->major = PTY_MASTER_MAJOR;
 510         pty_driver->minor_start = 0;
 511         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 512         pty_driver->subtype = PTY_TYPE_MASTER;
 513         pty_driver->init_termios = tty_std_termios;
 514         pty_driver->init_termios.c_iflag = 0;
 515         pty_driver->init_termios.c_oflag = 0;
 516         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 517         pty_driver->init_termios.c_lflag = 0;
 518         pty_driver->init_termios.c_ispeed = 38400;
 519         pty_driver->init_termios.c_ospeed = 38400;
 520         pty_driver->other = pty_slave_driver;
 521         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 522
 523         pty_slave_driver->driver_name = "pty_slave";
 524         pty_slave_driver->name = "ttyp";
 525         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 526         pty_slave_driver->minor_start = 0;
 527         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 528         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 529         pty_slave_driver->init_termios = tty_std_termios;
 530         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 531         pty_slave_driver->init_termios.c_ispeed = 38400;
 532         pty_slave_driver->init_termios.c_ospeed = 38400;
 533         pty_slave_driver->other = pty_driver;
 534         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 535
 536         if (tty_register_driver(pty_driver))
 537                 panic("Couldn't register pty driver");
 538         if (tty_register_driver(pty_slave_driver))
 539                 panic("Couldn't register pty slave driver");
 540 }
 541 #else
 542 static inline void legacy_pty_init(void) { }
 543 #endif
 544
 545 /* Unix98 devices */
 546 #ifdef CONFIG_UNIX98_PTYS
 547
 548 static struct cdev ptmx_cdev;
 549
 550 static int pty_unix98_ioctl(struct tty_struct *tty,
 551                             unsigned int cmd, unsigned long arg)
 552 {
 553         switch (cmd) {
 554         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 555                 return pty_set_lock(tty, (int __user *)arg);
 556         case TIOCGPTLCK: /* Get PT Lock status */
 557                 return pty_get_lock(tty, (int __user *)arg);
 558         case TIOCPKT: /* Set PT packet mode */
 559                 return pty_set_pktmode(tty, (int __user *)arg);
 560         case TIOCGPKT: /* Get PT packet mode */
 561                 return pty_get_pktmode(tty, (int __user *)arg);
 562         case TIOCGPTN: /* Get PT Number */
 563                 return put_user(tty->index, (unsigned int __user *)arg);
 564         case TIOCSIG:    /* Send signal to other side of pty */
 565                 return pty_signal(tty, (int) arg);
 566         }
 567
 568         return -ENOIOCTLCMD;
 569 }
 570
 571 /**
 572  *      ptm_unix98_lookup       -       find a pty master
 573  *      @driver: ptm driver
 574  *      @idx: tty index
 575  *
 576  *      Look up a pty master device. Called under the tty_mutex for now.
 577  *      This provides our locking.
 578  */
 579
 580 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 581                 struct inode *ptm_inode, int idx)
 582 {
 583         /* Master must be open via /dev/ptmx */
 584         return ERR_PTR(-EIO);
 585 }
 586
 587 /**
 588  *      pts_unix98_lookup       -       find a pty slave
 589  *      @driver: pts driver
 590  *      @idx: tty index
 591  *
 592  *      Look up a pty master device. Called under the tty_mutex for now.
 593  *      This provides our locking for the tty pointer.
 594  */
 595
 596 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 597                 struct inode *pts_inode, int idx)
 598 {
 599         struct tty_struct *tty;
 600
 601         mutex_lock(&devpts_mutex);
 602         tty = devpts_get_priv(pts_inode);
 603         mutex_unlock(&devpts_mutex);
 604         /* Master must be open before slave */
 605         if (!tty)
 606                 return ERR_PTR(-EIO);
 607         return tty;
 608 }
 609
 610 /* We have no need to install and remove our tty objects as devpts does all
 611    the work for us */
 612
 613 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 614 {
 615         return pty_common_install(driver, tty, false);
 616 }
 617
 618 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 619 {
 620 }
 621
 622 static const struct tty_operations ptm_unix98_ops = {
 623         .lookup = ptm_unix98_lookup,
 624         .install = pty_unix98_install,
 625         .remove = pty_unix98_remove,
 626         .open = pty_open,
 627         .close = pty_close,
 628         .write = pty_write,
 629         .write_room = pty_write_room,
 630         .flush_buffer = pty_flush_buffer,
 631         .chars_in_buffer = pty_chars_in_buffer,
 632         .unthrottle = pty_unthrottle,
 633         .set_termios = pty_set_termios,
 634         .ioctl = pty_unix98_ioctl,
 635         .resize = pty_resize,
 636         .shutdown = pty_unix98_shutdown,
 637         .cleanup = pty_cleanup
 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         .cleanup = pty_cleanup,
 654 };
 655
 656 /**
 657  *      ptmx_open               -       open a unix 98 pty master
 658  *      @inode: inode of device file
 659  *      @filp: file pointer to tty
 660  *
 661  *      Allocate a unix98 pty master device from the ptmx driver.
 662  *
 663  *      Locking: tty_mutex protects the init_dev work. tty->count should
 664  *              protect the rest.
 665  *              allocated_ptys_lock handles the list of free pty numbers
 666  */
 667
 668 static int ptmx_open(struct inode *inode, struct file *filp)
 669 {
 670         struct tty_struct *tty;
 671         struct inode *slave_inode;
 672         int retval;
 673         int index;
 674
 675         nonseekable_open(inode, filp);
 676
 677         retval = tty_alloc_file(filp);
 678         if (retval)
 679                 return retval;
 680
 681         /* find a device that is not in use. */
 682         mutex_lock(&devpts_mutex);
 683         index = devpts_new_index(inode);
 684         if (index < 0) {
 685                 retval = index;
 686                 mutex_unlock(&devpts_mutex);
 687                 goto err_file;
 688         }
 689
 690         mutex_unlock(&devpts_mutex);
 691
 692         mutex_lock(&tty_mutex);
 693         tty = tty_init_dev(ptm_driver, index);
 694
 695         if (IS_ERR(tty)) {
 696                 retval = PTR_ERR(tty);
 697                 goto out;
 698         }
 699
 700         /* The tty returned here is locked so we can safely
 701            drop the mutex */
 702         mutex_unlock(&tty_mutex);
 703
 704         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 705
 706         tty_add_file(tty, filp);
 707
 708         slave_inode = devpts_pty_new(inode,
 709                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 710                         tty->link);
 711         if (IS_ERR(slave_inode)) {
 712                 retval = PTR_ERR(slave_inode);
 713                 goto err_release;
 714         }
 715
 716         retval = ptm_driver->ops->open(tty, filp);
 717         if (retval)
 718                 goto err_release;
 719
 720         tty_unlock(tty);
 721         tty->driver_data = inode;
 722         tty->link->driver_data = slave_inode;
 723         return 0;
 724 err_release:
 725         tty_unlock(tty);
 726         tty_release(inode, filp);
 727         return retval;
 728 out:
 729         mutex_unlock(&tty_mutex);
 730         devpts_kill_index(inode, index);
 731 err_file:
 732         tty_free_file(filp);
 733         return retval;
 734 }
 735
 736 static struct file_operations ptmx_fops;
 737
 738 static void __init unix98_pty_init(void)
 739 {
 740         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 741                         TTY_DRIVER_RESET_TERMIOS |
 742                         TTY_DRIVER_REAL_RAW |
 743                         TTY_DRIVER_DYNAMIC_DEV |
 744                         TTY_DRIVER_DEVPTS_MEM |
 745                         TTY_DRIVER_DYNAMIC_ALLOC);
 746         if (IS_ERR(ptm_driver))
 747                 panic("Couldn't allocate Unix98 ptm driver");
 748         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 749                         TTY_DRIVER_RESET_TERMIOS |
 750                         TTY_DRIVER_REAL_RAW |
 751                         TTY_DRIVER_DYNAMIC_DEV |
 752                         TTY_DRIVER_DEVPTS_MEM |
 753                         TTY_DRIVER_DYNAMIC_ALLOC);
 754         if (IS_ERR(pts_driver))
 755                 panic("Couldn't allocate Unix98 pts driver");
 756
 757         ptm_driver->driver_name = "pty_master";
 758         ptm_driver->name = "ptm";
 759         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 760         ptm_driver->minor_start = 0;
 761         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 762         ptm_driver->subtype = PTY_TYPE_MASTER;
 763         ptm_driver->init_termios = tty_std_termios;
 764         ptm_driver->init_termios.c_iflag = 0;
 765         ptm_driver->init_termios.c_oflag = 0;
 766         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 767         ptm_driver->init_termios.c_lflag = 0;
 768         ptm_driver->init_termios.c_ispeed = 38400;
 769         ptm_driver->init_termios.c_ospeed = 38400;
 770         ptm_driver->other = pts_driver;
 771         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 772
 773         pts_driver->driver_name = "pty_slave";
 774         pts_driver->name = "pts";
 775         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 776         pts_driver->minor_start = 0;
 777         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 778         pts_driver->subtype = PTY_TYPE_SLAVE;
 779         pts_driver->init_termios = tty_std_termios;
 780         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 781         pts_driver->init_termios.c_ispeed = 38400;
 782         pts_driver->init_termios.c_ospeed = 38400;
 783         pts_driver->other = ptm_driver;
 784         tty_set_operations(pts_driver, &pty_unix98_ops);
 785
 786         if (tty_register_driver(ptm_driver))
 787                 panic("Couldn't register Unix98 ptm driver");
 788         if (tty_register_driver(pts_driver))
 789                 panic("Couldn't register Unix98 pts driver");
 790
 791         /* Now create the /dev/ptmx special device */
 792         tty_default_fops(&ptmx_fops);
 793         ptmx_fops.open = ptmx_open;
 794
 795         cdev_init(&ptmx_cdev, &ptmx_fops);
 796         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 797             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 798                 panic("Couldn't register /dev/ptmx driver");
 799         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 800 }
 801
 802 #else
 803 static inline void unix98_pty_init(void) { }
 804 #endif
 805
 806 static int __init pty_init(void)
 807 {
 808         legacy_pty_init();
 809         unix98_pty_init();
 810         return 0;
 811 }
 812 module_init(pty_init);