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 #undef TTY_DEBUG_HANGUP
  30 #ifdef TTY_DEBUG_HANGUP
  31 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
  32 #else
  33 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
  34 #endif
  35
  36 #ifdef CONFIG_UNIX98_PTYS
  37 static struct tty_driver *ptm_driver;
  38 static struct tty_driver *pts_driver;
  39 static DEFINE_MUTEX(devpts_mutex);
  40 #endif
  41
  42 static void pty_close(struct tty_struct *tty, struct file *filp)
  43 {
  44         BUG_ON(!tty);
  45         if (tty->driver->subtype == PTY_TYPE_MASTER)
  46                 WARN_ON(tty->count > 1);
  47         else {
  48                 if (test_bit(TTY_IO_ERROR, &tty->flags))
  49                         return;
  50                 if (tty->count > 2)
  51                         return;
  52         }
  53         set_bit(TTY_IO_ERROR, &tty->flags);
  54         wake_up_interruptible(&tty->read_wait);
  55         wake_up_interruptible(&tty->write_wait);
  56         spin_lock_irq(&tty->ctrl_lock);
  57         tty->packet = 0;
  58         spin_unlock_irq(&tty->ctrl_lock);
  59         /* Review - krefs on tty_link ?? */
  60         if (!tty->link)
  61                 return;
  62         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  63         tty_flip_buffer_push(tty->link->port);
  64         wake_up_interruptible(&tty->link->write_wait);
  65         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  66                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  67 #ifdef CONFIG_UNIX98_PTYS
  68                 if (tty->driver == ptm_driver) {
  69                         mutex_lock(&devpts_mutex);
  70                         if (tty->link->driver_data)
  71                                 devpts_pty_kill(tty->link->driver_data);
  72                         mutex_unlock(&devpts_mutex);
  73                 }
  74 #endif
  75                 tty_vhangup(tty->link);
  76         }
  77 }
  78
  79 /*
  80  * The unthrottle routine is called by the line discipline to signal
  81  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  82  * flag is always set, to force the line discipline to always call the
  83  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  84  * characters in the queue.  This is necessary since each time this
  85  * happens, we need to wake up any sleeping processes that could be
  86  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  87  * for the pty buffer to be drained.
  88  */
  89 static void pty_unthrottle(struct tty_struct *tty)
  90 {
  91         tty_wakeup(tty->link);
  92         set_bit(TTY_THROTTLED, &tty->flags);
  93 }
  94
  95 /**
  96  *      pty_write               -       write to a pty
  97  *      @tty: the tty we write from
  98  *      @buf: kernel buffer of data
  99  *      @count: bytes to write
 100  *
 101  *      Our "hardware" write method. Data is coming from the ldisc which
 102  *      may be in a non sleeping state. We simply throw this at the other
 103  *      end of the link as if we were an IRQ handler receiving stuff for
 104  *      the other side of the pty/tty pair.
 105  */
 106
 107 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 108 {
 109         struct tty_struct *to = tty->link;
 110
 111         if (tty->stopped)
 112                 return 0;
 113
 114         if (c > 0) {
 115                 /* Stuff the data into the input queue of the other end */
 116                 c = tty_insert_flip_string(to->port, buf, c);
 117                 /* And shovel */
 118                 if (c)
 119                         tty_flip_buffer_push(to->port);
 120         }
 121         return c;
 122 }
 123
 124 /**
 125  *      pty_write_room  -       write space
 126  *      @tty: tty we are writing from
 127  *
 128  *      Report how many bytes the ldisc can send into the queue for
 129  *      the other device.
 130  */
 131
 132 static int pty_write_room(struct tty_struct *tty)
 133 {
 134         if (tty->stopped)
 135                 return 0;
 136         return tty_buffer_space_avail(tty->link->port);
 137 }
 138
 139 /**
 140  *      pty_chars_in_buffer     -       characters currently in our tx queue
 141  *      @tty: our tty
 142  *
 143  *      Report how much we have in the transmit queue. As everything is
 144  *      instantly at the other end this is easy to implement.
 145  */
 146
 147 static int pty_chars_in_buffer(struct tty_struct *tty)
 148 {
 149         return 0;
 150 }
 151
 152 /* Set the lock flag on a pty */
 153 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 154 {
 155         int val;
 156         if (get_user(val, arg))
 157                 return -EFAULT;
 158         if (val)
 159                 set_bit(TTY_PTY_LOCK, &tty->flags);
 160         else
 161                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 162         return 0;
 163 }
 164
 165 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 166 {
 167         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 168         return put_user(locked, arg);
 169 }
 170
 171 /* Set the packet mode on a pty */
 172 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 173 {
 174         int pktmode;
 175
 176         if (get_user(pktmode, arg))
 177                 return -EFAULT;
 178
 179         spin_lock_irq(&tty->ctrl_lock);
 180         if (pktmode) {
 181                 if (!tty->packet) {
 182                         tty->link->ctrl_status = 0;
 183                         smp_mb();
 184                         tty->packet = 1;
 185                 }
 186         } else
 187                 tty->packet = 0;
 188         spin_unlock_irq(&tty->ctrl_lock);
 189
 190         return 0;
 191 }
 192
 193 /* Get the packet mode of a pty */
 194 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 195 {
 196         int pktmode = tty->packet;
 197         return put_user(pktmode, arg);
 198 }
 199
 200 /* Send a signal to the slave */
 201 static int pty_signal(struct tty_struct *tty, int sig)
 202 {
 203         struct pid *pgrp;
 204
 205         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 206                 return -EINVAL;
 207
 208         if (tty->link) {
 209                 pgrp = tty_get_pgrp(tty->link);
 210                 if (pgrp)
 211                         kill_pgrp(pgrp, sig, 1);
 212                 put_pid(pgrp);
 213         }
 214         return 0;
 215 }
 216
 217 static void pty_flush_buffer(struct tty_struct *tty)
 218 {
 219         struct tty_struct *to = tty->link;
 220         struct tty_ldisc *ld;
 221
 222         if (!to)
 223                 return;
 224
 225         ld = tty_ldisc_ref(to);
 226         tty_buffer_flush(to, ld);
 227         if (ld)
 228                 tty_ldisc_deref(ld);
 229
 230         if (to->packet) {
 231                 spin_lock_irq(&tty->ctrl_lock);
 232                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 233                 wake_up_interruptible(&to->read_wait);
 234                 spin_unlock_irq(&tty->ctrl_lock);
 235         }
 236 }
 237
 238 static int pty_open(struct tty_struct *tty, struct file *filp)
 239 {
 240         if (!tty || !tty->link)
 241                 return -ENODEV;
 242
 243         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 244                 goto out;
 245         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 246                 goto out;
 247         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 248                 goto out;
 249
 250         clear_bit(TTY_IO_ERROR, &tty->flags);
 251         /* TTY_OTHER_CLOSED must be cleared before TTY_OTHER_DONE */
 252         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 253         clear_bit(TTY_OTHER_DONE, &tty->link->flags);
 254         set_bit(TTY_THROTTLED, &tty->flags);
 255         return 0;
 256
 257 out:
 258         set_bit(TTY_IO_ERROR, &tty->flags);
 259         return -EIO;
 260 }
 261
 262 static void pty_set_termios(struct tty_struct *tty,
 263                                         struct ktermios *old_termios)
 264 {
 265         /* See if packet mode change of state. */
 266         if (tty->link && tty->link->packet) {
 267                 int extproc = (old_termios->c_lflag & EXTPROC) |
 268                                 (tty->termios.c_lflag & EXTPROC);
 269                 int old_flow = ((old_termios->c_iflag & IXON) &&
 270                                 (old_termios->c_cc[VSTOP] == '\023') &&
 271                                 (old_termios->c_cc[VSTART] == '\021'));
 272                 int new_flow = (I_IXON(tty) &&
 273                                 STOP_CHAR(tty) == '\023' &&
 274                                 START_CHAR(tty) == '\021');
 275                 if ((old_flow != new_flow) || extproc) {
 276                         spin_lock_irq(&tty->ctrl_lock);
 277                         if (old_flow != new_flow) {
 278                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 279                                 if (new_flow)
 280                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 281                                 else
 282                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 283                         }
 284                         if (extproc)
 285                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 286                         spin_unlock_irq(&tty->ctrl_lock);
 287                         wake_up_interruptible(&tty->link->read_wait);
 288                 }
 289         }
 290
 291         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 292         tty->termios.c_cflag |= (CS8 | CREAD);
 293 }
 294
 295 /**
 296  *      pty_do_resize           -       resize event
 297  *      @tty: tty being resized
 298  *      @ws: window size being set.
 299  *
 300  *      Update the termios variables and send the necessary signals to
 301  *      peform a terminal resize correctly
 302  */
 303
 304 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 305 {
 306         struct pid *pgrp, *rpgrp;
 307         struct tty_struct *pty = tty->link;
 308
 309         /* For a PTY we need to lock the tty side */
 310         mutex_lock(&tty->winsize_mutex);
 311         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 312                 goto done;
 313
 314         /* Signal the foreground process group of both ptys */
 315         pgrp = tty_get_pgrp(tty);
 316         rpgrp = tty_get_pgrp(pty);
 317
 318         if (pgrp)
 319                 kill_pgrp(pgrp, SIGWINCH, 1);
 320         if (rpgrp != pgrp && rpgrp)
 321                 kill_pgrp(rpgrp, SIGWINCH, 1);
 322
 323         put_pid(pgrp);
 324         put_pid(rpgrp);
 325
 326         tty->winsize = *ws;
 327         pty->winsize = *ws;     /* Never used so will go away soon */
 328 done:
 329         mutex_unlock(&tty->winsize_mutex);
 330         return 0;
 331 }
 332
 333 /**
 334  *      pty_start - start() handler
 335  *      pty_stop  - stop() handler
 336  *      @tty: tty being flow-controlled
 337  *
 338  *      Propagates the TIOCPKT status to the master pty.
 339  *
 340  *      NB: only the master pty can be in packet mode so only the slave
 341  *          needs start()/stop() handlers
 342  */
 343 static void pty_start(struct tty_struct *tty)
 344 {
 345         unsigned long flags;
 346
 347         if (tty->link && tty->link->packet) {
 348                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 349                 tty->ctrl_status &= ~TIOCPKT_STOP;
 350                 tty->ctrl_status |= TIOCPKT_START;
 351                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 352                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 353         }
 354 }
 355
 356 static void pty_stop(struct tty_struct *tty)
 357 {
 358         unsigned long flags;
 359
 360         if (tty->link && tty->link->packet) {
 361                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 362                 tty->ctrl_status &= ~TIOCPKT_START;
 363                 tty->ctrl_status |= TIOCPKT_STOP;
 364                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 365                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 366         }
 367 }
 368
 369 /**
 370  *      pty_common_install              -       set up the pty pair
 371  *      @driver: the pty driver
 372  *      @tty: the tty being instantiated
 373  *      @legacy: true if this is BSD style
 374  *
 375  *      Perform the initial set up for the tty/pty pair. Called from the
 376  *      tty layer when the port is first opened.
 377  *
 378  *      Locking: the caller must hold the tty_mutex
 379  */
 380 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 381                 bool legacy)
 382 {
 383         struct tty_struct *o_tty;
 384         struct tty_port *ports[2];
 385         int idx = tty->index;
 386         int retval = -ENOMEM;
 387
 388         /* Opening the slave first has always returned -EIO */
 389         if (driver->subtype != PTY_TYPE_MASTER)
 390                 return -EIO;
 391
 392         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 393         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 394         if (!ports[0] || !ports[1])
 395                 goto err;
 396         if (!try_module_get(driver->other->owner)) {
 397                 /* This cannot in fact currently happen */
 398                 goto err;
 399         }
 400         o_tty = alloc_tty_struct(driver->other, idx);
 401         if (!o_tty)
 402                 goto err_put_module;
 403
 404         tty_set_lock_subclass(o_tty);
 405         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 406
 407         if (legacy) {
 408                 /* We always use new tty termios data so we can do this
 409                    the easy way .. */
 410                 retval = tty_init_termios(tty);
 411                 if (retval)
 412                         goto err_deinit_tty;
 413
 414                 retval = tty_init_termios(o_tty);
 415                 if (retval)
 416                         goto err_free_termios;
 417
 418                 driver->other->ttys[idx] = o_tty;
 419                 driver->ttys[idx] = tty;
 420         } else {
 421                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 422                 tty->termios = driver->init_termios;
 423                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 424                 o_tty->termios = driver->other->init_termios;
 425         }
 426
 427         /*
 428          * Everything allocated ... set up the o_tty structure.
 429          */
 430         tty_driver_kref_get(driver->other);
 431         /* Establish the links in both directions */
 432         tty->link   = o_tty;
 433         o_tty->link = tty;
 434         tty_port_init(ports[0]);
 435         tty_port_init(ports[1]);
 436         tty_buffer_set_limit(ports[0], 8192);
 437         tty_buffer_set_limit(ports[1], 8192);
 438         o_tty->port = ports[0];
 439         tty->port = ports[1];
 440         o_tty->port->itty = o_tty;
 441
 442         tty_buffer_set_lock_subclass(o_tty->port);
 443
 444         tty_driver_kref_get(driver);
 445         tty->count++;
 446         o_tty->count++;
 447         return 0;
 448 err_free_termios:
 449         if (legacy)
 450                 tty_free_termios(tty);
 451 err_deinit_tty:
 452         deinitialize_tty_struct(o_tty);
 453         free_tty_struct(o_tty);
 454 err_put_module:
 455         module_put(driver->other->owner);
 456 err:
 457         kfree(ports[0]);
 458         kfree(ports[1]);
 459         return retval;
 460 }
 461
 462 static void pty_cleanup(struct tty_struct *tty)
 463 {
 464         tty_port_put(tty->port);
 465 }
 466
 467 /* Traditional BSD devices */
 468 #ifdef CONFIG_LEGACY_PTYS
 469
 470 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 471 {
 472         return pty_common_install(driver, tty, true);
 473 }
 474
 475 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 476 {
 477         struct tty_struct *pair = tty->link;
 478         driver->ttys[tty->index] = NULL;
 479         if (pair)
 480                 pair->driver->ttys[pair->index] = NULL;
 481 }
 482
 483 static int pty_bsd_ioctl(struct tty_struct *tty,
 484                          unsigned int cmd, unsigned long arg)
 485 {
 486         switch (cmd) {
 487         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 488                 return pty_set_lock(tty, (int __user *) arg);
 489         case TIOCGPTLCK: /* Get PT Lock status */
 490                 return pty_get_lock(tty, (int __user *)arg);
 491         case TIOCPKT: /* Set PT packet mode */
 492                 return pty_set_pktmode(tty, (int __user *)arg);
 493         case TIOCGPKT: /* Get PT packet mode */
 494                 return pty_get_pktmode(tty, (int __user *)arg);
 495         case TIOCSIG:    /* Send signal to other side of pty */
 496                 return pty_signal(tty, (int) arg);
 497         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 498                 return -EINVAL;
 499         }
 500         return -ENOIOCTLCMD;
 501 }
 502
 503 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 504 module_param(legacy_count, int, 0);
 505
 506 /*
 507  * The master side of a pty can do TIOCSPTLCK and thus
 508  * has pty_bsd_ioctl.
 509  */
 510 static const struct tty_operations master_pty_ops_bsd = {
 511         .install = pty_install,
 512         .open = pty_open,
 513         .close = pty_close,
 514         .write = pty_write,
 515         .write_room = pty_write_room,
 516         .flush_buffer = pty_flush_buffer,
 517         .chars_in_buffer = pty_chars_in_buffer,
 518         .unthrottle = pty_unthrottle,
 519         .ioctl = pty_bsd_ioctl,
 520         .cleanup = pty_cleanup,
 521         .resize = pty_resize,
 522         .remove = pty_remove
 523 };
 524
 525 static const struct tty_operations slave_pty_ops_bsd = {
 526         .install = pty_install,
 527         .open = pty_open,
 528         .close = pty_close,
 529         .write = pty_write,
 530         .write_room = pty_write_room,
 531         .flush_buffer = pty_flush_buffer,
 532         .chars_in_buffer = pty_chars_in_buffer,
 533         .unthrottle = pty_unthrottle,
 534         .set_termios = pty_set_termios,
 535         .cleanup = pty_cleanup,
 536         .resize = pty_resize,
 537         .start = pty_start,
 538         .stop = pty_stop,
 539         .remove = pty_remove
 540 };
 541
 542 static void __init legacy_pty_init(void)
 543 {
 544         struct tty_driver *pty_driver, *pty_slave_driver;
 545
 546         if (legacy_count <= 0)
 547                 return;
 548
 549         pty_driver = tty_alloc_driver(legacy_count,
 550                         TTY_DRIVER_RESET_TERMIOS |
 551                         TTY_DRIVER_REAL_RAW |
 552                         TTY_DRIVER_DYNAMIC_ALLOC);
 553         if (IS_ERR(pty_driver))
 554                 panic("Couldn't allocate pty driver");
 555
 556         pty_slave_driver = tty_alloc_driver(legacy_count,
 557                         TTY_DRIVER_RESET_TERMIOS |
 558                         TTY_DRIVER_REAL_RAW |
 559                         TTY_DRIVER_DYNAMIC_ALLOC);
 560         if (IS_ERR(pty_slave_driver))
 561                 panic("Couldn't allocate pty slave driver");
 562
 563         pty_driver->driver_name = "pty_master";
 564         pty_driver->name = "pty";
 565         pty_driver->major = PTY_MASTER_MAJOR;
 566         pty_driver->minor_start = 0;
 567         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 568         pty_driver->subtype = PTY_TYPE_MASTER;
 569         pty_driver->init_termios = tty_std_termios;
 570         pty_driver->init_termios.c_iflag = 0;
 571         pty_driver->init_termios.c_oflag = 0;
 572         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 573         pty_driver->init_termios.c_lflag = 0;
 574         pty_driver->init_termios.c_ispeed = 38400;
 575         pty_driver->init_termios.c_ospeed = 38400;
 576         pty_driver->other = pty_slave_driver;
 577         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 578
 579         pty_slave_driver->driver_name = "pty_slave";
 580         pty_slave_driver->name = "ttyp";
 581         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 582         pty_slave_driver->minor_start = 0;
 583         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 584         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 585         pty_slave_driver->init_termios = tty_std_termios;
 586         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 587         pty_slave_driver->init_termios.c_ispeed = 38400;
 588         pty_slave_driver->init_termios.c_ospeed = 38400;
 589         pty_slave_driver->other = pty_driver;
 590         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 591
 592         if (tty_register_driver(pty_driver))
 593                 panic("Couldn't register pty driver");
 594         if (tty_register_driver(pty_slave_driver))
 595                 panic("Couldn't register pty slave driver");
 596 }
 597 #else
 598 static inline void legacy_pty_init(void) { }
 599 #endif
 600
 601 /* Unix98 devices */
 602 #ifdef CONFIG_UNIX98_PTYS
 603
 604 static struct cdev ptmx_cdev;
 605
 606 static int pty_unix98_ioctl(struct tty_struct *tty,
 607                             unsigned int cmd, unsigned long arg)
 608 {
 609         switch (cmd) {
 610         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 611                 return pty_set_lock(tty, (int __user *)arg);
 612         case TIOCGPTLCK: /* Get PT Lock status */
 613                 return pty_get_lock(tty, (int __user *)arg);
 614         case TIOCPKT: /* Set PT packet mode */
 615                 return pty_set_pktmode(tty, (int __user *)arg);
 616         case TIOCGPKT: /* Get PT packet mode */
 617                 return pty_get_pktmode(tty, (int __user *)arg);
 618         case TIOCGPTN: /* Get PT Number */
 619                 return put_user(tty->index, (unsigned int __user *)arg);
 620         case TIOCSIG:    /* Send signal to other side of pty */
 621                 return pty_signal(tty, (int) arg);
 622         }
 623
 624         return -ENOIOCTLCMD;
 625 }
 626
 627 /**
 628  *      ptm_unix98_lookup       -       find a pty master
 629  *      @driver: ptm driver
 630  *      @idx: tty index
 631  *
 632  *      Look up a pty master device. Called under the tty_mutex for now.
 633  *      This provides our locking.
 634  */
 635
 636 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 637                 struct inode *ptm_inode, int idx)
 638 {
 639         /* Master must be open via /dev/ptmx */
 640         return ERR_PTR(-EIO);
 641 }
 642
 643 /**
 644  *      pts_unix98_lookup       -       find a pty slave
 645  *      @driver: pts driver
 646  *      @idx: tty index
 647  *
 648  *      Look up a pty master device. Called under the tty_mutex for now.
 649  *      This provides our locking for the tty pointer.
 650  */
 651
 652 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 653                 struct inode *pts_inode, int idx)
 654 {
 655         struct tty_struct *tty;
 656
 657         mutex_lock(&devpts_mutex);
 658         tty = devpts_get_priv(pts_inode);
 659         mutex_unlock(&devpts_mutex);
 660         /* Master must be open before slave */
 661         if (!tty)
 662                 return ERR_PTR(-EIO);
 663         return tty;
 664 }
 665
 666 /* We have no need to install and remove our tty objects as devpts does all
 667    the work for us */
 668
 669 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 670 {
 671         return pty_common_install(driver, tty, false);
 672 }
 673
 674 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 675 {
 676 }
 677
 678 /* this is called once with whichever end is closed last */
 679 static void pty_unix98_shutdown(struct tty_struct *tty)
 680 {
 681         devpts_kill_index(tty->driver_data, tty->index);
 682 }
 683
 684 static const struct tty_operations ptm_unix98_ops = {
 685         .lookup = ptm_unix98_lookup,
 686         .install = pty_unix98_install,
 687         .remove = pty_unix98_remove,
 688         .open = pty_open,
 689         .close = pty_close,
 690         .write = pty_write,
 691         .write_room = pty_write_room,
 692         .flush_buffer = pty_flush_buffer,
 693         .chars_in_buffer = pty_chars_in_buffer,
 694         .unthrottle = pty_unthrottle,
 695         .ioctl = pty_unix98_ioctl,
 696         .resize = pty_resize,
 697         .shutdown = pty_unix98_shutdown,
 698         .cleanup = pty_cleanup
 699 };
 700
 701 static const struct tty_operations pty_unix98_ops = {
 702         .lookup = pts_unix98_lookup,
 703         .install = pty_unix98_install,
 704         .remove = pty_unix98_remove,
 705         .open = pty_open,
 706         .close = pty_close,
 707         .write = pty_write,
 708         .write_room = pty_write_room,
 709         .flush_buffer = pty_flush_buffer,
 710         .chars_in_buffer = pty_chars_in_buffer,
 711         .unthrottle = pty_unthrottle,
 712         .set_termios = pty_set_termios,
 713         .start = pty_start,
 714         .stop = pty_stop,
 715         .shutdown = pty_unix98_shutdown,
 716         .cleanup = pty_cleanup,
 717 };
 718
 719 /**
 720  *      ptmx_open               -       open a unix 98 pty master
 721  *      @inode: inode of device file
 722  *      @filp: file pointer to tty
 723  *
 724  *      Allocate a unix98 pty master device from the ptmx driver.
 725  *
 726  *      Locking: tty_mutex protects the init_dev work. tty->count should
 727  *              protect the rest.
 728  *              allocated_ptys_lock handles the list of free pty numbers
 729  */
 730
 731 static int ptmx_open(struct inode *inode, struct file *filp)
 732 {
 733         struct tty_struct *tty;
 734         struct inode *slave_inode;
 735         int retval;
 736         int index;
 737
 738         nonseekable_open(inode, filp);
 739
 740         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 741         filp->f_mode |= FMODE_NONOTIFY;
 742
 743         retval = tty_alloc_file(filp);
 744         if (retval)
 745                 return retval;
 746
 747         /* find a device that is not in use. */
 748         mutex_lock(&devpts_mutex);
 749         index = devpts_new_index(inode);
 750         if (index < 0) {
 751                 retval = index;
 752                 mutex_unlock(&devpts_mutex);
 753                 goto err_file;
 754         }
 755
 756         mutex_unlock(&devpts_mutex);
 757
 758         mutex_lock(&tty_mutex);
 759         tty = tty_init_dev(ptm_driver, index);
 760
 761         if (IS_ERR(tty)) {
 762                 retval = PTR_ERR(tty);
 763                 goto out;
 764         }
 765
 766         /* The tty returned here is locked so we can safely
 767            drop the mutex */
 768         mutex_unlock(&tty_mutex);
 769
 770         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 771         tty->driver_data = inode;
 772
 773         tty_add_file(tty, filp);
 774
 775         slave_inode = devpts_pty_new(inode,
 776                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 777                         tty->link);
 778         if (IS_ERR(slave_inode)) {
 779                 retval = PTR_ERR(slave_inode);
 780                 goto err_release;
 781         }
 782         tty->link->driver_data = slave_inode;
 783
 784         retval = ptm_driver->ops->open(tty, filp);
 785         if (retval)
 786                 goto err_release;
 787
 788         tty_debug_hangup(tty, "(tty count=%d)\n", tty->count);
 789
 790         tty_unlock(tty);
 791         return 0;
 792 err_release:
 793         tty_unlock(tty);
 794         tty_release(inode, filp);
 795         return retval;
 796 out:
 797         mutex_unlock(&tty_mutex);
 798         devpts_kill_index(inode, index);
 799 err_file:
 800         tty_free_file(filp);
 801         return retval;
 802 }
 803
 804 static struct file_operations ptmx_fops;
 805
 806 static void __init unix98_pty_init(void)
 807 {
 808         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 809                         TTY_DRIVER_RESET_TERMIOS |
 810                         TTY_DRIVER_REAL_RAW |
 811                         TTY_DRIVER_DYNAMIC_DEV |
 812                         TTY_DRIVER_DEVPTS_MEM |
 813                         TTY_DRIVER_DYNAMIC_ALLOC);
 814         if (IS_ERR(ptm_driver))
 815                 panic("Couldn't allocate Unix98 ptm driver");
 816         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 817                         TTY_DRIVER_RESET_TERMIOS |
 818                         TTY_DRIVER_REAL_RAW |
 819                         TTY_DRIVER_DYNAMIC_DEV |
 820                         TTY_DRIVER_DEVPTS_MEM |
 821                         TTY_DRIVER_DYNAMIC_ALLOC);
 822         if (IS_ERR(pts_driver))
 823                 panic("Couldn't allocate Unix98 pts driver");
 824
 825         ptm_driver->driver_name = "pty_master";
 826         ptm_driver->name = "ptm";
 827         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 828         ptm_driver->minor_start = 0;
 829         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 830         ptm_driver->subtype = PTY_TYPE_MASTER;
 831         ptm_driver->init_termios = tty_std_termios;
 832         ptm_driver->init_termios.c_iflag = 0;
 833         ptm_driver->init_termios.c_oflag = 0;
 834         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 835         ptm_driver->init_termios.c_lflag = 0;
 836         ptm_driver->init_termios.c_ispeed = 38400;
 837         ptm_driver->init_termios.c_ospeed = 38400;
 838         ptm_driver->other = pts_driver;
 839         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 840
 841         pts_driver->driver_name = "pty_slave";
 842         pts_driver->name = "pts";
 843         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 844         pts_driver->minor_start = 0;
 845         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 846         pts_driver->subtype = PTY_TYPE_SLAVE;
 847         pts_driver->init_termios = tty_std_termios;
 848         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 849         pts_driver->init_termios.c_ispeed = 38400;
 850         pts_driver->init_termios.c_ospeed = 38400;
 851         pts_driver->other = ptm_driver;
 852         tty_set_operations(pts_driver, &pty_unix98_ops);
 853
 854         if (tty_register_driver(ptm_driver))
 855                 panic("Couldn't register Unix98 ptm driver");
 856         if (tty_register_driver(pts_driver))
 857                 panic("Couldn't register Unix98 pts driver");
 858
 859         /* Now create the /dev/ptmx special device */
 860         tty_default_fops(&ptmx_fops);
 861         ptmx_fops.open = ptmx_open;
 862
 863         cdev_init(&ptmx_cdev, &ptmx_fops);
 864         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 865             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 866                 panic("Couldn't register /dev/ptmx driver");
 867         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 868 }
 869
 870 #else
 871 static inline void unix98_pty_init(void) { }
 872 #endif
 873
 874 static int __init pty_init(void)
 875 {
 876         legacy_pty_init();
 877         unix98_pty_init();
 878         return 0;
 879 }
 880 module_init(pty_init);