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 <[email protected]>, 14-Jan-1998
   6  *
   7  */
   8
   9 #include <linux/module.h>
  10
  11 #include <linux/errno.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/tty.h>
  14 #include <linux/tty_flip.h>
  15 #include <linux/fcntl.h>
  16 #include <linux/sched.h>
  17 #include <linux/string.h>
  18 #include <linux/major.h>
  19 #include <linux/mm.h>
  20 #include <linux/init.h>
  21 #include <linux/device.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/bitops.h>
  24 #include <linux/devpts_fs.h>
  25 #include <linux/slab.h>
  26 #include <linux/mutex.h>
  27 #include <linux/poll.h>
  28
  29
  30 #ifdef CONFIG_UNIX98_PTYS
  31 static struct tty_driver *ptm_driver;
  32 static struct tty_driver *pts_driver;
  33 static DEFINE_MUTEX(devpts_mutex);
  34 #endif
  35
  36 static void pty_close(struct tty_struct *tty, struct file *filp)
  37 {
  38         BUG_ON(!tty);
  39         if (tty->driver->subtype == PTY_TYPE_MASTER)
  40                 WARN_ON(tty->count > 1);
  41         else {
  42                 if (test_bit(TTY_IO_ERROR, &tty->flags))
  43                         return;
  44                 if (tty->count > 2)
  45                         return;
  46         }
  47         set_bit(TTY_IO_ERROR, &tty->flags);
  48         wake_up_interruptible(&tty->read_wait);
  49         wake_up_interruptible(&tty->write_wait);
  50         spin_lock_irq(&tty->ctrl_lock);
  51         tty->packet = 0;
  52         spin_unlock_irq(&tty->ctrl_lock);
  53         /* Review - krefs on tty_link ?? */
  54         if (!tty->link)
  55                 return;
  56         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  57         tty_flip_buffer_push(tty->link->port);
  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                         mutex_lock(&devpts_mutex);
  64                         if (tty->link->driver_data)
  65                                 devpts_pty_kill(tty->link->driver_data);
  66                         mutex_unlock(&devpts_mutex);
  67                 }
  68 #endif
  69                 tty_vhangup(tty->link);
  70         }
  71 }
  72
  73 /*
  74  * The unthrottle routine is called by the line discipline to signal
  75  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  76  * flag is always set, to force the line discipline to always call the
  77  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  78  * characters in the queue.  This is necessary since each time this
  79  * happens, we need to wake up any sleeping processes that could be
  80  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  81  * for the pty buffer to be drained.
  82  */
  83 static void pty_unthrottle(struct tty_struct *tty)
  84 {
  85         tty_wakeup(tty->link);
  86         set_bit(TTY_THROTTLED, &tty->flags);
  87 }
  88
  89 /**
  90  *      pty_write               -       write to a pty
  91  *      @tty: the tty we write from
  92  *      @buf: kernel buffer of data
  93  *      @count: bytes to write
  94  *
  95  *      Our "hardware" write method. Data is coming from the ldisc which
  96  *      may be in a non sleeping state. We simply throw this at the other
  97  *      end of the link as if we were an IRQ handler receiving stuff for
  98  *      the other side of the pty/tty pair.
  99  */
 100
 101 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 102 {
 103         struct tty_struct *to = tty->link;
 104
 105         if (tty->stopped)
 106                 return 0;
 107
 108         if (c > 0) {
 109                 /* Stuff the data into the input queue of the other end */
 110                 c = tty_insert_flip_string(to->port, buf, c);
 111                 /* And shovel */
 112                 if (c)
 113                         tty_flip_buffer_push(to->port);
 114         }
 115         return c;
 116 }
 117
 118 /**
 119  *      pty_write_room  -       write space
 120  *      @tty: tty we are writing from
 121  *
 122  *      Report how many bytes the ldisc can send into the queue for
 123  *      the other device.
 124  */
 125
 126 static int pty_write_room(struct tty_struct *tty)
 127 {
 128         if (tty->stopped)
 129                 return 0;
 130         return tty_buffer_space_avail(tty->link->port);
 131 }
 132
 133 /**
 134  *      pty_chars_in_buffer     -       characters currently in our tx queue
 135  *      @tty: our tty
 136  *
 137  *      Report how much we have in the transmit queue. As everything is
 138  *      instantly at the other end this is easy to implement.
 139  */
 140
 141 static int pty_chars_in_buffer(struct tty_struct *tty)
 142 {
 143         return 0;
 144 }
 145
 146 /* Set the lock flag on a pty */
 147 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 148 {
 149         int val;
 150         if (get_user(val, arg))
 151                 return -EFAULT;
 152         if (val)
 153                 set_bit(TTY_PTY_LOCK, &tty->flags);
 154         else
 155                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 156         return 0;
 157 }
 158
 159 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 160 {
 161         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 162         return put_user(locked, arg);
 163 }
 164
 165 /* Set the packet mode on a pty */
 166 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 167 {
 168         int pktmode;
 169
 170         if (get_user(pktmode, arg))
 171                 return -EFAULT;
 172
 173         spin_lock_irq(&tty->ctrl_lock);
 174         if (pktmode) {
 175                 if (!tty->packet) {
 176                         tty->link->ctrl_status = 0;
 177                         smp_mb();
 178                         tty->packet = 1;
 179                 }
 180         } else
 181                 tty->packet = 0;
 182         spin_unlock_irq(&tty->ctrl_lock);
 183
 184         return 0;
 185 }
 186
 187 /* Get the packet mode of a pty */
 188 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 189 {
 190         int pktmode = tty->packet;
 191         return put_user(pktmode, arg);
 192 }
 193
 194 /* Send a signal to the slave */
 195 static int pty_signal(struct tty_struct *tty, int sig)
 196 {
 197         struct pid *pgrp;
 198
 199         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 200                 return -EINVAL;
 201
 202         if (tty->link) {
 203                 pgrp = tty_get_pgrp(tty->link);
 204                 if (pgrp)
 205                         kill_pgrp(pgrp, sig, 1);
 206                 put_pid(pgrp);
 207         }
 208         return 0;
 209 }
 210
 211 static void pty_flush_buffer(struct tty_struct *tty)
 212 {
 213         struct tty_struct *to = tty->link;
 214         struct tty_ldisc *ld;
 215
 216         if (!to)
 217                 return;
 218
 219         ld = tty_ldisc_ref(to);
 220         tty_buffer_flush(to, ld);
 221         if (ld)
 222                 tty_ldisc_deref(ld);
 223
 224         if (to->packet) {
 225                 spin_lock_irq(&tty->ctrl_lock);
 226                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 227                 wake_up_interruptible(&to->read_wait);
 228                 spin_unlock_irq(&tty->ctrl_lock);
 229         }
 230 }
 231
 232 static int pty_open(struct tty_struct *tty, struct file *filp)
 233 {
 234         if (!tty || !tty->link)
 235                 return -ENODEV;
 236
 237         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 238                 goto out;
 239         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 240                 goto out;
 241         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 242                 goto out;
 243
 244         clear_bit(TTY_IO_ERROR, &tty->flags);
 245         /* TTY_OTHER_CLOSED must be cleared before TTY_OTHER_DONE */
 246         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 247         clear_bit(TTY_OTHER_DONE, &tty->link->flags);
 248         set_bit(TTY_THROTTLED, &tty->flags);
 249         return 0;
 250
 251 out:
 252         set_bit(TTY_IO_ERROR, &tty->flags);
 253         return -EIO;
 254 }
 255
 256 static void pty_set_termios(struct tty_struct *tty,
 257                                         struct ktermios *old_termios)
 258 {
 259         /* See if packet mode change of state. */
 260         if (tty->link && tty->link->packet) {
 261                 int extproc = (old_termios->c_lflag & EXTPROC) |
 262                                 (tty->termios.c_lflag & EXTPROC);
 263                 int old_flow = ((old_termios->c_iflag & IXON) &&
 264                                 (old_termios->c_cc[VSTOP] == '\023') &&
 265                                 (old_termios->c_cc[VSTART] == '\021'));
 266                 int new_flow = (I_IXON(tty) &&
 267                                 STOP_CHAR(tty) == '\023' &&
 268                                 START_CHAR(tty) == '\021');
 269                 if ((old_flow != new_flow) || extproc) {
 270                         spin_lock_irq(&tty->ctrl_lock);
 271                         if (old_flow != new_flow) {
 272                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 273                                 if (new_flow)
 274                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 275                                 else
 276                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 277                         }
 278                         if (extproc)
 279                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 280                         spin_unlock_irq(&tty->ctrl_lock);
 281                         wake_up_interruptible(&tty->link->read_wait);
 282                 }
 283         }
 284
 285         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 286         tty->termios.c_cflag |= (CS8 | CREAD);
 287 }
 288
 289 /**
 290  *      pty_do_resize           -       resize event
 291  *      @tty: tty being resized
 292  *      @ws: window size being set.
 293  *
 294  *      Update the termios variables and send the necessary signals to
 295  *      peform a terminal resize correctly
 296  */
 297
 298 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 299 {
 300         struct pid *pgrp, *rpgrp;
 301         struct tty_struct *pty = tty->link;
 302
 303         /* For a PTY we need to lock the tty side */
 304         mutex_lock(&tty->winsize_mutex);
 305         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 306                 goto done;
 307
 308         /* Signal the foreground process group of both ptys */
 309         pgrp = tty_get_pgrp(tty);
 310         rpgrp = tty_get_pgrp(pty);
 311
 312         if (pgrp)
 313                 kill_pgrp(pgrp, SIGWINCH, 1);
 314         if (rpgrp != pgrp && rpgrp)
 315                 kill_pgrp(rpgrp, SIGWINCH, 1);
 316
 317         put_pid(pgrp);
 318         put_pid(rpgrp);
 319
 320         tty->winsize = *ws;
 321         pty->winsize = *ws;     /* Never used so will go away soon */
 322 done:
 323         mutex_unlock(&tty->winsize_mutex);
 324         return 0;
 325 }
 326
 327 /**
 328  *      pty_start - start() handler
 329  *      pty_stop  - stop() handler
 330  *      @tty: tty being flow-controlled
 331  *
 332  *      Propagates the TIOCPKT status to the master pty.
 333  *
 334  *      NB: only the master pty can be in packet mode so only the slave
 335  *          needs start()/stop() handlers
 336  */
 337 static void pty_start(struct tty_struct *tty)
 338 {
 339         unsigned long flags;
 340
 341         if (tty->link && tty->link->packet) {
 342                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 343                 tty->ctrl_status &= ~TIOCPKT_STOP;
 344                 tty->ctrl_status |= TIOCPKT_START;
 345                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 346                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 347         }
 348 }
 349
 350 static void pty_stop(struct tty_struct *tty)
 351 {
 352         unsigned long flags;
 353
 354         if (tty->link && tty->link->packet) {
 355                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 356                 tty->ctrl_status &= ~TIOCPKT_START;
 357                 tty->ctrl_status |= TIOCPKT_STOP;
 358                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 359                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 360         }
 361 }
 362
 363 /**
 364  *      pty_common_install              -       set up the pty pair
 365  *      @driver: the pty driver
 366  *      @tty: the tty being instantiated
 367  *      @legacy: true if this is BSD style
 368  *
 369  *      Perform the initial set up for the tty/pty pair. Called from the
 370  *      tty layer when the port is first opened.
 371  *
 372  *      Locking: the caller must hold the tty_mutex
 373  */
 374 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 375                 bool legacy)
 376 {
 377         struct tty_struct *o_tty;
 378         struct tty_port *ports[2];
 379         int idx = tty->index;
 380         int retval = -ENOMEM;
 381
 382         /* Opening the slave first has always returned -EIO */
 383         if (driver->subtype != PTY_TYPE_MASTER)
 384                 return -EIO;
 385
 386         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 387         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 388         if (!ports[0] || !ports[1])
 389                 goto err;
 390         if (!try_module_get(driver->other->owner)) {
 391                 /* This cannot in fact currently happen */
 392                 goto err;
 393         }
 394         o_tty = alloc_tty_struct(driver->other, idx);
 395         if (!o_tty)
 396                 goto err_put_module;
 397
 398         tty_set_lock_subclass(o_tty);
 399         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 400
 401         if (legacy) {
 402                 /* We always use new tty termios data so we can do this
 403                    the easy way .. */
 404                 retval = tty_init_termios(tty);
 405                 if (retval)
 406                         goto err_deinit_tty;
 407
 408                 retval = tty_init_termios(o_tty);
 409                 if (retval)
 410                         goto err_free_termios;
 411
 412                 driver->other->ttys[idx] = o_tty;
 413                 driver->ttys[idx] = tty;
 414         } else {
 415                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 416                 tty->termios = driver->init_termios;
 417                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 418                 o_tty->termios = driver->other->init_termios;
 419         }
 420
 421         /*
 422          * Everything allocated ... set up the o_tty structure.
 423          */
 424         tty_driver_kref_get(driver->other);
 425         /* Establish the links in both directions */
 426         tty->link   = o_tty;
 427         o_tty->link = tty;
 428         tty_port_init(ports[0]);
 429         tty_port_init(ports[1]);
 430         tty_buffer_set_limit(ports[0], 8192);
 431         tty_buffer_set_limit(ports[1], 8192);
 432         o_tty->port = ports[0];
 433         tty->port = ports[1];
 434         o_tty->port->itty = o_tty;
 435
 436         tty_buffer_set_lock_subclass(o_tty->port);
 437
 438         tty_driver_kref_get(driver);
 439         tty->count++;
 440         o_tty->count++;
 441         return 0;
 442 err_free_termios:
 443         if (legacy)
 444                 tty_free_termios(tty);
 445 err_deinit_tty:
 446         deinitialize_tty_struct(o_tty);
 447         free_tty_struct(o_tty);
 448 err_put_module:
 449         module_put(driver->other->owner);
 450 err:
 451         kfree(ports[0]);
 452         kfree(ports[1]);
 453         return retval;
 454 }
 455
 456 static void pty_cleanup(struct tty_struct *tty)
 457 {
 458         tty_port_put(tty->port);
 459 }
 460
 461 /* Traditional BSD devices */
 462 #ifdef CONFIG_LEGACY_PTYS
 463
 464 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 465 {
 466         return pty_common_install(driver, tty, true);
 467 }
 468
 469 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 470 {
 471         struct tty_struct *pair = tty->link;
 472         driver->ttys[tty->index] = NULL;
 473         if (pair)
 474                 pair->driver->ttys[pair->index] = NULL;
 475 }
 476
 477 static int pty_bsd_ioctl(struct tty_struct *tty,
 478                          unsigned int cmd, unsigned long arg)
 479 {
 480         switch (cmd) {
 481         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 482                 return pty_set_lock(tty, (int __user *) arg);
 483         case TIOCGPTLCK: /* Get PT Lock status */
 484                 return pty_get_lock(tty, (int __user *)arg);
 485         case TIOCPKT: /* Set PT packet mode */
 486                 return pty_set_pktmode(tty, (int __user *)arg);
 487         case TIOCGPKT: /* Get PT packet mode */
 488                 return pty_get_pktmode(tty, (int __user *)arg);
 489         case TIOCSIG:    /* Send signal to other side of pty */
 490                 return pty_signal(tty, (int) arg);
 491         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 492                 return -EINVAL;
 493         }
 494         return -ENOIOCTLCMD;
 495 }
 496
 497 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 498 module_param(legacy_count, int, 0);
 499
 500 /*
 501  * The master side of a pty can do TIOCSPTLCK and thus
 502  * has pty_bsd_ioctl.
 503  */
 504 static const struct tty_operations master_pty_ops_bsd = {
 505         .install = pty_install,
 506         .open = pty_open,
 507         .close = pty_close,
 508         .write = pty_write,
 509         .write_room = pty_write_room,
 510         .flush_buffer = pty_flush_buffer,
 511         .chars_in_buffer = pty_chars_in_buffer,
 512         .unthrottle = pty_unthrottle,
 513         .ioctl = pty_bsd_ioctl,
 514         .cleanup = pty_cleanup,
 515         .resize = pty_resize,
 516         .remove = pty_remove
 517 };
 518
 519 static const struct tty_operations slave_pty_ops_bsd = {
 520         .install = pty_install,
 521         .open = pty_open,
 522         .close = pty_close,
 523         .write = pty_write,
 524         .write_room = pty_write_room,
 525         .flush_buffer = pty_flush_buffer,
 526         .chars_in_buffer = pty_chars_in_buffer,
 527         .unthrottle = pty_unthrottle,
 528         .set_termios = pty_set_termios,
 529         .cleanup = pty_cleanup,
 530         .resize = pty_resize,
 531         .start = pty_start,
 532         .stop = pty_stop,
 533         .remove = pty_remove
 534 };
 535
 536 static void __init legacy_pty_init(void)
 537 {
 538         struct tty_driver *pty_driver, *pty_slave_driver;
 539
 540         if (legacy_count <= 0)
 541                 return;
 542
 543         pty_driver = tty_alloc_driver(legacy_count,
 544                         TTY_DRIVER_RESET_TERMIOS |
 545                         TTY_DRIVER_REAL_RAW |
 546                         TTY_DRIVER_DYNAMIC_ALLOC);
 547         if (IS_ERR(pty_driver))
 548                 panic("Couldn't allocate pty driver");
 549
 550         pty_slave_driver = tty_alloc_driver(legacy_count,
 551                         TTY_DRIVER_RESET_TERMIOS |
 552                         TTY_DRIVER_REAL_RAW |
 553                         TTY_DRIVER_DYNAMIC_ALLOC);
 554         if (IS_ERR(pty_slave_driver))
 555                 panic("Couldn't allocate pty slave driver");
 556
 557         pty_driver->driver_name = "pty_master";
 558         pty_driver->name = "pty";
 559         pty_driver->major = PTY_MASTER_MAJOR;
 560         pty_driver->minor_start = 0;
 561         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 562         pty_driver->subtype = PTY_TYPE_MASTER;
 563         pty_driver->init_termios = tty_std_termios;
 564         pty_driver->init_termios.c_iflag = 0;
 565         pty_driver->init_termios.c_oflag = 0;
 566         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 567         pty_driver->init_termios.c_lflag = 0;
 568         pty_driver->init_termios.c_ispeed = 38400;
 569         pty_driver->init_termios.c_ospeed = 38400;
 570         pty_driver->other = pty_slave_driver;
 571         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 572
 573         pty_slave_driver->driver_name = "pty_slave";
 574         pty_slave_driver->name = "ttyp";
 575         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 576         pty_slave_driver->minor_start = 0;
 577         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 578         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 579         pty_slave_driver->init_termios = tty_std_termios;
 580         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 581         pty_slave_driver->init_termios.c_ispeed = 38400;
 582         pty_slave_driver->init_termios.c_ospeed = 38400;
 583         pty_slave_driver->other = pty_driver;
 584         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 585
 586         if (tty_register_driver(pty_driver))
 587                 panic("Couldn't register pty driver");
 588         if (tty_register_driver(pty_slave_driver))
 589                 panic("Couldn't register pty slave driver");
 590 }
 591 #else
 592 static inline void legacy_pty_init(void) { }
 593 #endif
 594
 595 /* Unix98 devices */
 596 #ifdef CONFIG_UNIX98_PTYS
 597
 598 static struct cdev ptmx_cdev;
 599
 600 static int pty_unix98_ioctl(struct tty_struct *tty,
 601                             unsigned int cmd, unsigned long arg)
 602 {
 603         switch (cmd) {
 604         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 605                 return pty_set_lock(tty, (int __user *)arg);
 606         case TIOCGPTLCK: /* Get PT Lock status */
 607                 return pty_get_lock(tty, (int __user *)arg);
 608         case TIOCPKT: /* Set PT packet mode */
 609                 return pty_set_pktmode(tty, (int __user *)arg);
 610         case TIOCGPKT: /* Get PT packet mode */
 611                 return pty_get_pktmode(tty, (int __user *)arg);
 612         case TIOCGPTN: /* Get PT Number */
 613                 return put_user(tty->index, (unsigned int __user *)arg);
 614         case TIOCSIG:    /* Send signal to other side of pty */
 615                 return pty_signal(tty, (int) arg);
 616         }
 617
 618         return -ENOIOCTLCMD;
 619 }
 620
 621 /**
 622  *      ptm_unix98_lookup       -       find a pty master
 623  *      @driver: ptm driver
 624  *      @idx: tty index
 625  *
 626  *      Look up a pty master device. Called under the tty_mutex for now.
 627  *      This provides our locking.
 628  */
 629
 630 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 631                 struct inode *ptm_inode, int idx)
 632 {
 633         /* Master must be open via /dev/ptmx */
 634         return ERR_PTR(-EIO);
 635 }
 636
 637 /**
 638  *      pts_unix98_lookup       -       find a pty slave
 639  *      @driver: pts driver
 640  *      @idx: tty index
 641  *
 642  *      Look up a pty master device. Called under the tty_mutex for now.
 643  *      This provides our locking for the tty pointer.
 644  */
 645
 646 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 647                 struct inode *pts_inode, int idx)
 648 {
 649         struct tty_struct *tty;
 650
 651         mutex_lock(&devpts_mutex);
 652         tty = devpts_get_priv(pts_inode);
 653         mutex_unlock(&devpts_mutex);
 654         /* Master must be open before slave */
 655         if (!tty)
 656                 return ERR_PTR(-EIO);
 657         return tty;
 658 }
 659
 660 /* We have no need to install and remove our tty objects as devpts does all
 661    the work for us */
 662
 663 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 664 {
 665         return pty_common_install(driver, tty, false);
 666 }
 667
 668 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 669 {
 670 }
 671
 672 /* this is called once with whichever end is closed last */
 673 static void pty_unix98_shutdown(struct tty_struct *tty)
 674 {
 675         devpts_kill_index(tty->driver_data, tty->index);
 676 }
 677
 678 static const struct tty_operations ptm_unix98_ops = {
 679         .lookup = ptm_unix98_lookup,
 680         .install = pty_unix98_install,
 681         .remove = pty_unix98_remove,
 682         .open = pty_open,
 683         .close = pty_close,
 684         .write = pty_write,
 685         .write_room = pty_write_room,
 686         .flush_buffer = pty_flush_buffer,
 687         .chars_in_buffer = pty_chars_in_buffer,
 688         .unthrottle = pty_unthrottle,
 689         .ioctl = pty_unix98_ioctl,
 690         .resize = pty_resize,
 691         .shutdown = pty_unix98_shutdown,
 692         .cleanup = pty_cleanup
 693 };
 694
 695 static const struct tty_operations pty_unix98_ops = {
 696         .lookup = pts_unix98_lookup,
 697         .install = pty_unix98_install,
 698         .remove = pty_unix98_remove,
 699         .open = pty_open,
 700         .close = pty_close,
 701         .write = pty_write,
 702         .write_room = pty_write_room,
 703         .flush_buffer = pty_flush_buffer,
 704         .chars_in_buffer = pty_chars_in_buffer,
 705         .unthrottle = pty_unthrottle,
 706         .set_termios = pty_set_termios,
 707         .start = pty_start,
 708         .stop = pty_stop,
 709         .shutdown = pty_unix98_shutdown,
 710         .cleanup = pty_cleanup,
 711 };
 712
 713 /**
 714  *      ptmx_open               -       open a unix 98 pty master
 715  *      @inode: inode of device file
 716  *      @filp: file pointer to tty
 717  *
 718  *      Allocate a unix98 pty master device from the ptmx driver.
 719  *
 720  *      Locking: tty_mutex protects the init_dev work. tty->count should
 721  *              protect the rest.
 722  *              allocated_ptys_lock handles the list of free pty numbers
 723  */
 724
 725 static int ptmx_open(struct inode *inode, struct file *filp)
 726 {
 727         struct tty_struct *tty;
 728         struct inode *slave_inode;
 729         int retval;
 730         int index;
 731
 732         nonseekable_open(inode, filp);
 733
 734         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 735         filp->f_mode |= FMODE_NONOTIFY;
 736
 737         retval = tty_alloc_file(filp);
 738         if (retval)
 739                 return retval;
 740
 741         /* find a device that is not in use. */
 742         mutex_lock(&devpts_mutex);
 743         index = devpts_new_index(inode);
 744         if (index < 0) {
 745                 retval = index;
 746                 mutex_unlock(&devpts_mutex);
 747                 goto err_file;
 748         }
 749
 750         mutex_unlock(&devpts_mutex);
 751
 752         mutex_lock(&tty_mutex);
 753         tty = tty_init_dev(ptm_driver, index);
 754
 755         if (IS_ERR(tty)) {
 756                 retval = PTR_ERR(tty);
 757                 goto out;
 758         }
 759
 760         /* The tty returned here is locked so we can safely
 761            drop the mutex */
 762         mutex_unlock(&tty_mutex);
 763
 764         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 765         tty->driver_data = inode;
 766
 767         tty_add_file(tty, filp);
 768
 769         slave_inode = devpts_pty_new(inode,
 770                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 771                         tty->link);
 772         if (IS_ERR(slave_inode)) {
 773                 retval = PTR_ERR(slave_inode);
 774                 goto err_release;
 775         }
 776         tty->link->driver_data = slave_inode;
 777
 778         retval = ptm_driver->ops->open(tty, filp);
 779         if (retval)
 780                 goto err_release;
 781
 782         tty_unlock(tty);
 783         return 0;
 784 err_release:
 785         tty_unlock(tty);
 786         tty_release(inode, filp);
 787         return retval;
 788 out:
 789         mutex_unlock(&tty_mutex);
 790         devpts_kill_index(inode, index);
 791 err_file:
 792         tty_free_file(filp);
 793         return retval;
 794 }
 795
 796 static struct file_operations ptmx_fops;
 797
 798 static void __init unix98_pty_init(void)
 799 {
 800         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 801                         TTY_DRIVER_RESET_TERMIOS |
 802                         TTY_DRIVER_REAL_RAW |
 803                         TTY_DRIVER_DYNAMIC_DEV |
 804                         TTY_DRIVER_DEVPTS_MEM |
 805                         TTY_DRIVER_DYNAMIC_ALLOC);
 806         if (IS_ERR(ptm_driver))
 807                 panic("Couldn't allocate Unix98 ptm driver");
 808         pts_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(pts_driver))
 815                 panic("Couldn't allocate Unix98 pts driver");
 816
 817         ptm_driver->driver_name = "pty_master";
 818         ptm_driver->name = "ptm";
 819         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 820         ptm_driver->minor_start = 0;
 821         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 822         ptm_driver->subtype = PTY_TYPE_MASTER;
 823         ptm_driver->init_termios = tty_std_termios;
 824         ptm_driver->init_termios.c_iflag = 0;
 825         ptm_driver->init_termios.c_oflag = 0;
 826         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 827         ptm_driver->init_termios.c_lflag = 0;
 828         ptm_driver->init_termios.c_ispeed = 38400;
 829         ptm_driver->init_termios.c_ospeed = 38400;
 830         ptm_driver->other = pts_driver;
 831         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 832
 833         pts_driver->driver_name = "pty_slave";
 834         pts_driver->name = "pts";
 835         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 836         pts_driver->minor_start = 0;
 837         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 838         pts_driver->subtype = PTY_TYPE_SLAVE;
 839         pts_driver->init_termios = tty_std_termios;
 840         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 841         pts_driver->init_termios.c_ispeed = 38400;
 842         pts_driver->init_termios.c_ospeed = 38400;
 843         pts_driver->other = ptm_driver;
 844         tty_set_operations(pts_driver, &pty_unix98_ops);
 845
 846         if (tty_register_driver(ptm_driver))
 847                 panic("Couldn't register Unix98 ptm driver");
 848         if (tty_register_driver(pts_driver))
 849                 panic("Couldn't register Unix98 pts driver");
 850
 851         /* Now create the /dev/ptmx special device */
 852         tty_default_fops(&ptmx_fops);
 853         ptmx_fops.open = ptmx_open;
 854
 855         cdev_init(&ptmx_cdev, &ptmx_fops);
 856         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 857             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 858                 panic("Couldn't register /dev/ptmx driver");
 859         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 860 }
 861
 862 #else
 863 static inline void unix98_pty_init(void) { }
 864 #endif
 865
 866 static int __init pty_init(void)
 867 {
 868         legacy_pty_init();
 869         unix98_pty_init();
 870         return 0;
 871 }
 872 module_init(pty_init);