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 #include <linux/errno.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/tty.h>
  13 #include <linux/tty_flip.h>
  14 #include <linux/fcntl.h>
  15 #include <linux/sched/signal.h>
  16 #include <linux/string.h>
  17 #include <linux/major.h>
  18 #include <linux/mm.h>
  19 #include <linux/init.h>
  20 #include <linux/device.h>
  21 #include <linux/uaccess.h>
  22 #include <linux/bitops.h>
  23 #include <linux/devpts_fs.h>
  24 #include <linux/slab.h>
  25 #include <linux/mutex.h>
  26 #include <linux/poll.h>
  27 #include <linux/mount.h>
  28 #include <linux/file.h>
  29 #include <linux/ioctl.h>
  30
  31 #undef TTY_DEBUG_HANGUP
  32 #ifdef TTY_DEBUG_HANGUP
  33 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
  34 #else
  35 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
  36 #endif
  37
  38 #ifdef CONFIG_UNIX98_PTYS
  39 static struct tty_driver *ptm_driver;
  40 static struct tty_driver *pts_driver;
  41 static DEFINE_MUTEX(devpts_mutex);
  42 #endif
  43
  44 static void pty_close(struct tty_struct *tty, struct file *filp)
  45 {
  46         BUG_ON(!tty);
  47         if (tty->driver->subtype == PTY_TYPE_MASTER)
  48                 WARN_ON(tty->count > 1);
  49         else {
  50                 if (tty_io_error(tty))
  51                         return;
  52                 if (tty->count > 2)
  53                         return;
  54         }
  55         set_bit(TTY_IO_ERROR, &tty->flags);
  56         wake_up_interruptible(&tty->read_wait);
  57         wake_up_interruptible(&tty->write_wait);
  58         spin_lock_irq(&tty->ctrl_lock);
  59         tty->packet = 0;
  60         spin_unlock_irq(&tty->ctrl_lock);
  61         /* Review - krefs on tty_link ?? */
  62         if (!tty->link)
  63                 return;
  64         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  65         wake_up_interruptible(&tty->link->read_wait);
  66         wake_up_interruptible(&tty->link->write_wait);
  67         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  68                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  69 #ifdef CONFIG_UNIX98_PTYS
  70                 if (tty->driver == ptm_driver) {
  71                         mutex_lock(&devpts_mutex);
  72                         if (tty->link->driver_data) {
  73                                 struct path *path = tty->link->driver_data;
  74
  75                                 devpts_pty_kill(path->dentry);
  76                                 path_put(path);
  77                                 kfree(path);
  78                         }
  79                         mutex_unlock(&devpts_mutex);
  80                 }
  81 #endif
  82                 tty_vhangup(tty->link);
  83         }
  84 }
  85
  86 /*
  87  * The unthrottle routine is called by the line discipline to signal
  88  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  89  * flag is always set, to force the line discipline to always call the
  90  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  91  * characters in the queue.  This is necessary since each time this
  92  * happens, we need to wake up any sleeping processes that could be
  93  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  94  * for the pty buffer to be drained.
  95  */
  96 static void pty_unthrottle(struct tty_struct *tty)
  97 {
  98         tty_wakeup(tty->link);
  99         set_bit(TTY_THROTTLED, &tty->flags);
 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         }
 128         return c;
 129 }
 130
 131 /**
 132  *      pty_write_room  -       write space
 133  *      @tty: tty we are writing from
 134  *
 135  *      Report how many bytes the ldisc can send into the queue for
 136  *      the other device.
 137  */
 138
 139 static int pty_write_room(struct tty_struct *tty)
 140 {
 141         if (tty->stopped)
 142                 return 0;
 143         return tty_buffer_space_avail(tty->link->port);
 144 }
 145
 146 /**
 147  *      pty_chars_in_buffer     -       characters currently in our tx queue
 148  *      @tty: our tty
 149  *
 150  *      Report how much we have in the transmit queue. As everything is
 151  *      instantly at the other end this is easy to implement.
 152  */
 153
 154 static int pty_chars_in_buffer(struct tty_struct *tty)
 155 {
 156         return 0;
 157 }
 158
 159 /* Set the lock flag on a pty */
 160 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 161 {
 162         int val;
 163         if (get_user(val, arg))
 164                 return -EFAULT;
 165         if (val)
 166                 set_bit(TTY_PTY_LOCK, &tty->flags);
 167         else
 168                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 169         return 0;
 170 }
 171
 172 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 173 {
 174         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 175         return put_user(locked, arg);
 176 }
 177
 178 /* Set the packet mode on a pty */
 179 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 180 {
 181         int pktmode;
 182
 183         if (get_user(pktmode, arg))
 184                 return -EFAULT;
 185
 186         spin_lock_irq(&tty->ctrl_lock);
 187         if (pktmode) {
 188                 if (!tty->packet) {
 189                         tty->link->ctrl_status = 0;
 190                         smp_mb();
 191                         tty->packet = 1;
 192                 }
 193         } else
 194                 tty->packet = 0;
 195         spin_unlock_irq(&tty->ctrl_lock);
 196
 197         return 0;
 198 }
 199
 200 /* Get the packet mode of a pty */
 201 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 202 {
 203         int pktmode = tty->packet;
 204         return put_user(pktmode, arg);
 205 }
 206
 207 /* Send a signal to the slave */
 208 static int pty_signal(struct tty_struct *tty, int sig)
 209 {
 210         struct pid *pgrp;
 211
 212         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 213                 return -EINVAL;
 214
 215         if (tty->link) {
 216                 pgrp = tty_get_pgrp(tty->link);
 217                 if (pgrp)
 218                         kill_pgrp(pgrp, sig, 1);
 219                 put_pid(pgrp);
 220         }
 221         return 0;
 222 }
 223
 224 static void pty_flush_buffer(struct tty_struct *tty)
 225 {
 226         struct tty_struct *to = tty->link;
 227
 228         if (!to)
 229                 return;
 230
 231         tty_buffer_flush(to, NULL);
 232         if (to->packet) {
 233                 spin_lock_irq(&tty->ctrl_lock);
 234                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 235                 wake_up_interruptible(&to->read_wait);
 236                 spin_unlock_irq(&tty->ctrl_lock);
 237         }
 238 }
 239
 240 static int pty_open(struct tty_struct *tty, struct file *filp)
 241 {
 242         if (!tty || !tty->link)
 243                 return -ENODEV;
 244
 245         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 246                 goto out;
 247         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 248                 goto out;
 249         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 250                 goto out;
 251
 252         clear_bit(TTY_IO_ERROR, &tty->flags);
 253         clear_bit(TTY_OTHER_CLOSED, &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) | L_EXTPROC(tty);
 268                 int old_flow = ((old_termios->c_iflag & IXON) &&
 269                                 (old_termios->c_cc[VSTOP] == '\023') &&
 270                                 (old_termios->c_cc[VSTART] == '\021'));
 271                 int new_flow = (I_IXON(tty) &&
 272                                 STOP_CHAR(tty) == '\023' &&
 273                                 START_CHAR(tty) == '\021');
 274                 if ((old_flow != new_flow) || extproc) {
 275                         spin_lock_irq(&tty->ctrl_lock);
 276                         if (old_flow != new_flow) {
 277                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 278                                 if (new_flow)
 279                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 280                                 else
 281                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 282                         }
 283                         if (extproc)
 284                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 285                         spin_unlock_irq(&tty->ctrl_lock);
 286                         wake_up_interruptible(&tty->link->read_wait);
 287                 }
 288         }
 289
 290         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 291         tty->termios.c_cflag |= (CS8 | CREAD);
 292 }
 293
 294 /**
 295  *      pty_do_resize           -       resize event
 296  *      @tty: tty being resized
 297  *      @ws: window size being set.
 298  *
 299  *      Update the termios variables and send the necessary signals to
 300  *      peform a terminal resize correctly
 301  */
 302
 303 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 304 {
 305         struct pid *pgrp, *rpgrp;
 306         struct tty_struct *pty = tty->link;
 307
 308         /* For a PTY we need to lock the tty side */
 309         mutex_lock(&tty->winsize_mutex);
 310         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 311                 goto done;
 312
 313         /* Signal the foreground process group of both ptys */
 314         pgrp = tty_get_pgrp(tty);
 315         rpgrp = tty_get_pgrp(pty);
 316
 317         if (pgrp)
 318                 kill_pgrp(pgrp, SIGWINCH, 1);
 319         if (rpgrp != pgrp && rpgrp)
 320                 kill_pgrp(rpgrp, SIGWINCH, 1);
 321
 322         put_pid(pgrp);
 323         put_pid(rpgrp);
 324
 325         tty->winsize = *ws;
 326         pty->winsize = *ws;     /* Never used so will go away soon */
 327 done:
 328         mutex_unlock(&tty->winsize_mutex);
 329         return 0;
 330 }
 331
 332 /**
 333  *      pty_start - start() handler
 334  *      pty_stop  - stop() handler
 335  *      @tty: tty being flow-controlled
 336  *
 337  *      Propagates the TIOCPKT status to the master pty.
 338  *
 339  *      NB: only the master pty can be in packet mode so only the slave
 340  *          needs start()/stop() handlers
 341  */
 342 static void pty_start(struct tty_struct *tty)
 343 {
 344         unsigned long flags;
 345
 346         if (tty->link && tty->link->packet) {
 347                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 348                 tty->ctrl_status &= ~TIOCPKT_STOP;
 349                 tty->ctrl_status |= TIOCPKT_START;
 350                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 351                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 352         }
 353 }
 354
 355 static void pty_stop(struct tty_struct *tty)
 356 {
 357         unsigned long flags;
 358
 359         if (tty->link && tty->link->packet) {
 360                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 361                 tty->ctrl_status &= ~TIOCPKT_START;
 362                 tty->ctrl_status |= TIOCPKT_STOP;
 363                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 364                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 365         }
 366 }
 367
 368 /**
 369  *      pty_common_install              -       set up the pty pair
 370  *      @driver: the pty driver
 371  *      @tty: the tty being instantiated
 372  *      @legacy: true if this is BSD style
 373  *
 374  *      Perform the initial set up for the tty/pty pair. Called from the
 375  *      tty layer when the port is first opened.
 376  *
 377  *      Locking: the caller must hold the tty_mutex
 378  */
 379 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 380                 bool legacy)
 381 {
 382         struct tty_struct *o_tty;
 383         struct tty_port *ports[2];
 384         int idx = tty->index;
 385         int retval = -ENOMEM;
 386
 387         /* Opening the slave first has always returned -EIO */
 388         if (driver->subtype != PTY_TYPE_MASTER)
 389                 return -EIO;
 390
 391         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 392         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 393         if (!ports[0] || !ports[1])
 394                 goto err;
 395         if (!try_module_get(driver->other->owner)) {
 396                 /* This cannot in fact currently happen */
 397                 goto err;
 398         }
 399         o_tty = alloc_tty_struct(driver->other, idx);
 400         if (!o_tty)
 401                 goto err_put_module;
 402
 403         tty_set_lock_subclass(o_tty);
 404         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 405
 406         if (legacy) {
 407                 /* We always use new tty termios data so we can do this
 408                    the easy way .. */
 409                 tty_init_termios(tty);
 410                 tty_init_termios(o_tty);
 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
 443 err_put_module:
 444         module_put(driver->other->owner);
 445 err:
 446         kfree(ports[0]);
 447         kfree(ports[1]);
 448         return retval;
 449 }
 450
 451 /**
 452  *      pty_open_peer - open the peer of a pty
 453  *      @tty: the peer of the pty being opened
 454  *
 455  *      Open the cached dentry in tty->link, providing a safe way for userspace
 456  *      to get the slave end of a pty (where they have the master fd and cannot
 457  *      access or trust the mount namespace /dev/pts was mounted inside).
 458  */
 459 static struct file *pty_open_peer(struct tty_struct *tty, int flags)
 460 {
 461         if (tty->driver->subtype != PTY_TYPE_MASTER)
 462                 return ERR_PTR(-EIO);
 463         return dentry_open(tty->link->driver_data, flags, current_cred());
 464 }
 465
 466 static int pty_get_peer(struct tty_struct *tty, int flags)
 467 {
 468         int fd = -1;
 469         struct file *filp = NULL;
 470         int retval = -EINVAL;
 471
 472         fd = get_unused_fd_flags(0);
 473         if (fd < 0) {
 474                 retval = fd;
 475                 goto err;
 476         }
 477
 478         filp = pty_open_peer(tty, flags);
 479         if (IS_ERR(filp)) {
 480                 retval = PTR_ERR(filp);
 481                 goto err_put;
 482         }
 483
 484         fd_install(fd, filp);
 485         return fd;
 486
 487 err_put:
 488         put_unused_fd(fd);
 489 err:
 490         return retval;
 491 }
 492
 493 static void pty_cleanup(struct tty_struct *tty)
 494 {
 495         tty_port_put(tty->port);
 496 }
 497
 498 /* Traditional BSD devices */
 499 #ifdef CONFIG_LEGACY_PTYS
 500
 501 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 502 {
 503         return pty_common_install(driver, tty, true);
 504 }
 505
 506 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 507 {
 508         struct tty_struct *pair = tty->link;
 509         driver->ttys[tty->index] = NULL;
 510         if (pair)
 511                 pair->driver->ttys[pair->index] = NULL;
 512 }
 513
 514 static int pty_bsd_ioctl(struct tty_struct *tty,
 515                          unsigned int cmd, unsigned long arg)
 516 {
 517         switch (cmd) {
 518         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 519                 return pty_set_lock(tty, (int __user *) arg);
 520         case TIOCGPTLCK: /* Get PT Lock status */
 521                 return pty_get_lock(tty, (int __user *)arg);
 522         case TIOCPKT: /* Set PT packet mode */
 523                 return pty_set_pktmode(tty, (int __user *)arg);
 524         case TIOCGPKT: /* Get PT packet mode */
 525                 return pty_get_pktmode(tty, (int __user *)arg);
 526         case TIOCSIG:    /* Send signal to other side of pty */
 527                 return pty_signal(tty, (int) arg);
 528         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 529                 return -EINVAL;
 530         }
 531         return -ENOIOCTLCMD;
 532 }
 533
 534 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
 535                                  unsigned int cmd, unsigned long arg)
 536 {
 537         /*
 538          * PTY ioctls don't require any special translation between 32-bit and
 539          * 64-bit userspace, they are already compatible.
 540          */
 541         return pty_bsd_ioctl(tty, cmd, arg);
 542 }
 543
 544 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 545 /*
 546  * not really modular, but the easiest way to keep compat with existing
 547  * bootargs behaviour is to continue using module_param here.
 548  */
 549 module_param(legacy_count, int, 0);
 550
 551 /*
 552  * The master side of a pty can do TIOCSPTLCK and thus
 553  * has pty_bsd_ioctl.
 554  */
 555 static const struct tty_operations master_pty_ops_bsd = {
 556         .install = pty_install,
 557         .open = pty_open,
 558         .close = pty_close,
 559         .write = pty_write,
 560         .write_room = pty_write_room,
 561         .flush_buffer = pty_flush_buffer,
 562         .chars_in_buffer = pty_chars_in_buffer,
 563         .unthrottle = pty_unthrottle,
 564         .ioctl = pty_bsd_ioctl,
 565         .compat_ioctl = pty_bsd_compat_ioctl,
 566         .cleanup = pty_cleanup,
 567         .resize = pty_resize,
 568         .remove = pty_remove
 569 };
 570
 571 static const struct tty_operations slave_pty_ops_bsd = {
 572         .install = pty_install,
 573         .open = pty_open,
 574         .close = pty_close,
 575         .write = pty_write,
 576         .write_room = pty_write_room,
 577         .flush_buffer = pty_flush_buffer,
 578         .chars_in_buffer = pty_chars_in_buffer,
 579         .unthrottle = pty_unthrottle,
 580         .set_termios = pty_set_termios,
 581         .cleanup = pty_cleanup,
 582         .resize = pty_resize,
 583         .start = pty_start,
 584         .stop = pty_stop,
 585         .remove = pty_remove
 586 };
 587
 588 static void __init legacy_pty_init(void)
 589 {
 590         struct tty_driver *pty_driver, *pty_slave_driver;
 591
 592         if (legacy_count <= 0)
 593                 return;
 594
 595         pty_driver = tty_alloc_driver(legacy_count,
 596                         TTY_DRIVER_RESET_TERMIOS |
 597                         TTY_DRIVER_REAL_RAW |
 598                         TTY_DRIVER_DYNAMIC_ALLOC);
 599         if (IS_ERR(pty_driver))
 600                 panic("Couldn't allocate pty driver");
 601
 602         pty_slave_driver = tty_alloc_driver(legacy_count,
 603                         TTY_DRIVER_RESET_TERMIOS |
 604                         TTY_DRIVER_REAL_RAW |
 605                         TTY_DRIVER_DYNAMIC_ALLOC);
 606         if (IS_ERR(pty_slave_driver))
 607                 panic("Couldn't allocate pty slave driver");
 608
 609         pty_driver->driver_name = "pty_master";
 610         pty_driver->name = "pty";
 611         pty_driver->major = PTY_MASTER_MAJOR;
 612         pty_driver->minor_start = 0;
 613         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 614         pty_driver->subtype = PTY_TYPE_MASTER;
 615         pty_driver->init_termios = tty_std_termios;
 616         pty_driver->init_termios.c_iflag = 0;
 617         pty_driver->init_termios.c_oflag = 0;
 618         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 619         pty_driver->init_termios.c_lflag = 0;
 620         pty_driver->init_termios.c_ispeed = 38400;
 621         pty_driver->init_termios.c_ospeed = 38400;
 622         pty_driver->other = pty_slave_driver;
 623         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 624
 625         pty_slave_driver->driver_name = "pty_slave";
 626         pty_slave_driver->name = "ttyp";
 627         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 628         pty_slave_driver->minor_start = 0;
 629         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 630         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 631         pty_slave_driver->init_termios = tty_std_termios;
 632         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 633         pty_slave_driver->init_termios.c_ispeed = 38400;
 634         pty_slave_driver->init_termios.c_ospeed = 38400;
 635         pty_slave_driver->other = pty_driver;
 636         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 637
 638         if (tty_register_driver(pty_driver))
 639                 panic("Couldn't register pty driver");
 640         if (tty_register_driver(pty_slave_driver))
 641                 panic("Couldn't register pty slave driver");
 642 }
 643 #else
 644 static inline void legacy_pty_init(void) { }
 645 #endif
 646
 647 /* Unix98 devices */
 648 #ifdef CONFIG_UNIX98_PTYS
 649
 650 static struct cdev ptmx_cdev;
 651
 652 static int pty_unix98_ioctl(struct tty_struct *tty,
 653                             unsigned int cmd, unsigned long arg)
 654 {
 655         switch (cmd) {
 656         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 657                 return pty_set_lock(tty, (int __user *)arg);
 658         case TIOCGPTLCK: /* Get PT Lock status */
 659                 return pty_get_lock(tty, (int __user *)arg);
 660         case TIOCPKT: /* Set PT packet mode */
 661                 return pty_set_pktmode(tty, (int __user *)arg);
 662         case TIOCGPKT: /* Get PT packet mode */
 663                 return pty_get_pktmode(tty, (int __user *)arg);
 664         case TIOCGPTN: /* Get PT Number */
 665                 return put_user(tty->index, (unsigned int __user *)arg);
 666         case TIOCGPTPEER: /* Open the other end */
 667                 return pty_get_peer(tty, (int) arg);
 668         case TIOCSIG:    /* Send signal to other side of pty */
 669                 return pty_signal(tty, (int) arg);
 670         }
 671
 672         return -ENOIOCTLCMD;
 673 }
 674
 675 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
 676                                  unsigned int cmd, unsigned long arg)
 677 {
 678         /*
 679          * PTY ioctls don't require any special translation between 32-bit and
 680          * 64-bit userspace, they are already compatible.
 681          */
 682         return pty_unix98_ioctl(tty, cmd, arg);
 683 }
 684
 685 /**
 686  *      ptm_unix98_lookup       -       find a pty master
 687  *      @driver: ptm driver
 688  *      @idx: tty index
 689  *
 690  *      Look up a pty master device. Called under the tty_mutex for now.
 691  *      This provides our locking.
 692  */
 693
 694 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 695                 struct file *file, int idx)
 696 {
 697         /* Master must be open via /dev/ptmx */
 698         return ERR_PTR(-EIO);
 699 }
 700
 701 /**
 702  *      pts_unix98_lookup       -       find a pty slave
 703  *      @driver: pts driver
 704  *      @idx: tty index
 705  *
 706  *      Look up a pty master device. Called under the tty_mutex for now.
 707  *      This provides our locking for the tty pointer.
 708  */
 709
 710 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 711                 struct file *file, int idx)
 712 {
 713         struct tty_struct *tty;
 714
 715         mutex_lock(&devpts_mutex);
 716         tty = devpts_get_priv(file->f_path.dentry);
 717         mutex_unlock(&devpts_mutex);
 718         /* Master must be open before slave */
 719         if (!tty)
 720                 return ERR_PTR(-EIO);
 721         return tty;
 722 }
 723
 724 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 725 {
 726         return pty_common_install(driver, tty, false);
 727 }
 728
 729 /* this is called once with whichever end is closed last */
 730 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 731 {
 732         struct pts_fs_info *fsi;
 733
 734         if (tty->driver->subtype == PTY_TYPE_MASTER)
 735                 fsi = tty->driver_data;
 736         else
 737                 fsi = tty->link->driver_data;
 738
 739         if (fsi) {
 740                 devpts_kill_index(fsi, tty->index);
 741                 devpts_release(fsi);
 742         }
 743 }
 744
 745 static const struct tty_operations ptm_unix98_ops = {
 746         .lookup = ptm_unix98_lookup,
 747         .install = pty_unix98_install,
 748         .remove = pty_unix98_remove,
 749         .open = pty_open,
 750         .close = pty_close,
 751         .write = pty_write,
 752         .write_room = pty_write_room,
 753         .flush_buffer = pty_flush_buffer,
 754         .chars_in_buffer = pty_chars_in_buffer,
 755         .unthrottle = pty_unthrottle,
 756         .ioctl = pty_unix98_ioctl,
 757         .compat_ioctl = pty_unix98_compat_ioctl,
 758         .resize = pty_resize,
 759         .cleanup = pty_cleanup
 760 };
 761
 762 static const struct tty_operations pty_unix98_ops = {
 763         .lookup = pts_unix98_lookup,
 764         .install = pty_unix98_install,
 765         .remove = pty_unix98_remove,
 766         .open = pty_open,
 767         .close = pty_close,
 768         .write = pty_write,
 769         .write_room = pty_write_room,
 770         .flush_buffer = pty_flush_buffer,
 771         .chars_in_buffer = pty_chars_in_buffer,
 772         .unthrottle = pty_unthrottle,
 773         .set_termios = pty_set_termios,
 774         .start = pty_start,
 775         .stop = pty_stop,
 776         .cleanup = pty_cleanup,
 777 };
 778
 779 /**
 780  *      ptmx_open               -       open a unix 98 pty master
 781  *      @inode: inode of device file
 782  *      @filp: file pointer to tty
 783  *
 784  *      Allocate a unix98 pty master device from the ptmx driver.
 785  *
 786  *      Locking: tty_mutex protects the init_dev work. tty->count should
 787  *              protect the rest.
 788  *              allocated_ptys_lock handles the list of free pty numbers
 789  */
 790
 791 static int ptmx_open(struct inode *inode, struct file *filp)
 792 {
 793         struct pts_fs_info *fsi;
 794         struct tty_struct *tty;
 795         struct path *pts_path;
 796         struct dentry *dentry;
 797         int retval;
 798         int index;
 799
 800         nonseekable_open(inode, filp);
 801
 802         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 803         filp->f_mode |= FMODE_NONOTIFY;
 804
 805         retval = tty_alloc_file(filp);
 806         if (retval)
 807                 return retval;
 808
 809         fsi = devpts_acquire(filp);
 810         if (IS_ERR(fsi)) {
 811                 retval = PTR_ERR(fsi);
 812                 goto out_free_file;
 813         }
 814
 815         /* find a device that is not in use. */
 816         mutex_lock(&devpts_mutex);
 817         index = devpts_new_index(fsi);
 818         mutex_unlock(&devpts_mutex);
 819
 820         retval = index;
 821         if (index < 0)
 822                 goto out_put_fsi;
 823
 824
 825         mutex_lock(&tty_mutex);
 826         tty = tty_init_dev(ptm_driver, index);
 827         /* The tty returned here is locked so we can safely
 828            drop the mutex */
 829         mutex_unlock(&tty_mutex);
 830
 831         retval = PTR_ERR(tty);
 832         if (IS_ERR(tty))
 833                 goto out;
 834
 835         /*
 836          * From here on out, the tty is "live", and the index and
 837          * fsi will be killed/put by the tty_release()
 838          */
 839         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 840         tty->driver_data = fsi;
 841
 842         tty_add_file(tty, filp);
 843
 844         dentry = devpts_pty_new(fsi, index, tty->link);
 845         if (IS_ERR(dentry)) {
 846                 retval = PTR_ERR(dentry);
 847                 goto err_release;
 848         }
 849         /* We need to cache a fake path for TIOCGPTPEER. */
 850         pts_path = kmalloc(sizeof(struct path), GFP_KERNEL);
 851         if (!pts_path)
 852                 goto err_release;
 853         pts_path->mnt = filp->f_path.mnt;
 854         pts_path->dentry = dentry;
 855         path_get(pts_path);
 856         tty->link->driver_data = pts_path;
 857
 858         retval = ptm_driver->ops->open(tty, filp);
 859         if (retval)
 860                 goto err_path_put;
 861
 862         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 863
 864         tty_unlock(tty);
 865         return 0;
 866 err_path_put:
 867         path_put(pts_path);
 868         kfree(pts_path);
 869 err_release:
 870         tty_unlock(tty);
 871         // This will also put-ref the fsi
 872         tty_release(inode, filp);
 873         return retval;
 874 out:
 875         devpts_kill_index(fsi, index);
 876 out_put_fsi:
 877         devpts_release(fsi);
 878 out_free_file:
 879         tty_free_file(filp);
 880         return retval;
 881 }
 882
 883 static struct file_operations ptmx_fops __ro_after_init;
 884
 885 static void __init unix98_pty_init(void)
 886 {
 887         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 888                         TTY_DRIVER_RESET_TERMIOS |
 889                         TTY_DRIVER_REAL_RAW |
 890                         TTY_DRIVER_DYNAMIC_DEV |
 891                         TTY_DRIVER_DEVPTS_MEM |
 892                         TTY_DRIVER_DYNAMIC_ALLOC);
 893         if (IS_ERR(ptm_driver))
 894                 panic("Couldn't allocate Unix98 ptm driver");
 895         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 896                         TTY_DRIVER_RESET_TERMIOS |
 897                         TTY_DRIVER_REAL_RAW |
 898                         TTY_DRIVER_DYNAMIC_DEV |
 899                         TTY_DRIVER_DEVPTS_MEM |
 900                         TTY_DRIVER_DYNAMIC_ALLOC);
 901         if (IS_ERR(pts_driver))
 902                 panic("Couldn't allocate Unix98 pts driver");
 903
 904         ptm_driver->driver_name = "pty_master";
 905         ptm_driver->name = "ptm";
 906         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 907         ptm_driver->minor_start = 0;
 908         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 909         ptm_driver->subtype = PTY_TYPE_MASTER;
 910         ptm_driver->init_termios = tty_std_termios;
 911         ptm_driver->init_termios.c_iflag = 0;
 912         ptm_driver->init_termios.c_oflag = 0;
 913         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 914         ptm_driver->init_termios.c_lflag = 0;
 915         ptm_driver->init_termios.c_ispeed = 38400;
 916         ptm_driver->init_termios.c_ospeed = 38400;
 917         ptm_driver->other = pts_driver;
 918         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 919
 920         pts_driver->driver_name = "pty_slave";
 921         pts_driver->name = "pts";
 922         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 923         pts_driver->minor_start = 0;
 924         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 925         pts_driver->subtype = PTY_TYPE_SLAVE;
 926         pts_driver->init_termios = tty_std_termios;
 927         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 928         pts_driver->init_termios.c_ispeed = 38400;
 929         pts_driver->init_termios.c_ospeed = 38400;
 930         pts_driver->other = ptm_driver;
 931         tty_set_operations(pts_driver, &pty_unix98_ops);
 932
 933         if (tty_register_driver(ptm_driver))
 934                 panic("Couldn't register Unix98 ptm driver");
 935         if (tty_register_driver(pts_driver))
 936                 panic("Couldn't register Unix98 pts driver");
 937
 938         /* Now create the /dev/ptmx special device */
 939         tty_default_fops(&ptmx_fops);
 940         ptmx_fops.open = ptmx_open;
 941
 942         cdev_init(&ptmx_cdev, &ptmx_fops);
 943         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 944             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 945                 panic("Couldn't register /dev/ptmx driver");
 946         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 947 }
 948
 949 #else
 950 static inline void unix98_pty_init(void) { }
 951 #endif
 952
 953 static int __init pty_init(void)
 954 {
 955         legacy_pty_init();
 956         unix98_pty_init();
 957         return 0;
 958 }
 959 device_initcall(pty_init);