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 static void pty_cleanup(struct tty_struct *tty)
 452 {
 453         tty_port_put(tty->port);
 454 }
 455
 456 /* Traditional BSD devices */
 457 #ifdef CONFIG_LEGACY_PTYS
 458
 459 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 460 {
 461         return pty_common_install(driver, tty, true);
 462 }
 463
 464 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 465 {
 466         struct tty_struct *pair = tty->link;
 467         driver->ttys[tty->index] = NULL;
 468         if (pair)
 469                 pair->driver->ttys[pair->index] = NULL;
 470 }
 471
 472 static int pty_bsd_ioctl(struct tty_struct *tty,
 473                          unsigned int cmd, unsigned long arg)
 474 {
 475         switch (cmd) {
 476         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 477                 return pty_set_lock(tty, (int __user *) arg);
 478         case TIOCGPTLCK: /* Get PT Lock status */
 479                 return pty_get_lock(tty, (int __user *)arg);
 480         case TIOCPKT: /* Set PT packet mode */
 481                 return pty_set_pktmode(tty, (int __user *)arg);
 482         case TIOCGPKT: /* Get PT packet mode */
 483                 return pty_get_pktmode(tty, (int __user *)arg);
 484         case TIOCSIG:    /* Send signal to other side of pty */
 485                 return pty_signal(tty, (int) arg);
 486         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 487                 return -EINVAL;
 488         }
 489         return -ENOIOCTLCMD;
 490 }
 491
 492 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
 493                                  unsigned int cmd, unsigned long arg)
 494 {
 495         /*
 496          * PTY ioctls don't require any special translation between 32-bit and
 497          * 64-bit userspace, they are already compatible.
 498          */
 499         return pty_bsd_ioctl(tty, cmd, arg);
 500 }
 501
 502 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 503 /*
 504  * not really modular, but the easiest way to keep compat with existing
 505  * bootargs behaviour is to continue using module_param here.
 506  */
 507 module_param(legacy_count, int, 0);
 508
 509 /*
 510  * The master side of a pty can do TIOCSPTLCK and thus
 511  * has pty_bsd_ioctl.
 512  */
 513 static const struct tty_operations master_pty_ops_bsd = {
 514         .install = pty_install,
 515         .open = pty_open,
 516         .close = pty_close,
 517         .write = pty_write,
 518         .write_room = pty_write_room,
 519         .flush_buffer = pty_flush_buffer,
 520         .chars_in_buffer = pty_chars_in_buffer,
 521         .unthrottle = pty_unthrottle,
 522         .ioctl = pty_bsd_ioctl,
 523         .compat_ioctl = pty_bsd_compat_ioctl,
 524         .cleanup = pty_cleanup,
 525         .resize = pty_resize,
 526         .remove = pty_remove
 527 };
 528
 529 static const struct tty_operations slave_pty_ops_bsd = {
 530         .install = pty_install,
 531         .open = pty_open,
 532         .close = pty_close,
 533         .write = pty_write,
 534         .write_room = pty_write_room,
 535         .flush_buffer = pty_flush_buffer,
 536         .chars_in_buffer = pty_chars_in_buffer,
 537         .unthrottle = pty_unthrottle,
 538         .set_termios = pty_set_termios,
 539         .cleanup = pty_cleanup,
 540         .resize = pty_resize,
 541         .start = pty_start,
 542         .stop = pty_stop,
 543         .remove = pty_remove
 544 };
 545
 546 static void __init legacy_pty_init(void)
 547 {
 548         struct tty_driver *pty_driver, *pty_slave_driver;
 549
 550         if (legacy_count <= 0)
 551                 return;
 552
 553         pty_driver = tty_alloc_driver(legacy_count,
 554                         TTY_DRIVER_RESET_TERMIOS |
 555                         TTY_DRIVER_REAL_RAW |
 556                         TTY_DRIVER_DYNAMIC_ALLOC);
 557         if (IS_ERR(pty_driver))
 558                 panic("Couldn't allocate pty driver");
 559
 560         pty_slave_driver = tty_alloc_driver(legacy_count,
 561                         TTY_DRIVER_RESET_TERMIOS |
 562                         TTY_DRIVER_REAL_RAW |
 563                         TTY_DRIVER_DYNAMIC_ALLOC);
 564         if (IS_ERR(pty_slave_driver))
 565                 panic("Couldn't allocate pty slave driver");
 566
 567         pty_driver->driver_name = "pty_master";
 568         pty_driver->name = "pty";
 569         pty_driver->major = PTY_MASTER_MAJOR;
 570         pty_driver->minor_start = 0;
 571         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 572         pty_driver->subtype = PTY_TYPE_MASTER;
 573         pty_driver->init_termios = tty_std_termios;
 574         pty_driver->init_termios.c_iflag = 0;
 575         pty_driver->init_termios.c_oflag = 0;
 576         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 577         pty_driver->init_termios.c_lflag = 0;
 578         pty_driver->init_termios.c_ispeed = 38400;
 579         pty_driver->init_termios.c_ospeed = 38400;
 580         pty_driver->other = pty_slave_driver;
 581         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 582
 583         pty_slave_driver->driver_name = "pty_slave";
 584         pty_slave_driver->name = "ttyp";
 585         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 586         pty_slave_driver->minor_start = 0;
 587         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 588         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 589         pty_slave_driver->init_termios = tty_std_termios;
 590         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 591         pty_slave_driver->init_termios.c_ispeed = 38400;
 592         pty_slave_driver->init_termios.c_ospeed = 38400;
 593         pty_slave_driver->other = pty_driver;
 594         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 595
 596         if (tty_register_driver(pty_driver))
 597                 panic("Couldn't register pty driver");
 598         if (tty_register_driver(pty_slave_driver))
 599                 panic("Couldn't register pty slave driver");
 600 }
 601 #else
 602 static inline void legacy_pty_init(void) { }
 603 #endif
 604
 605 /* Unix98 devices */
 606 #ifdef CONFIG_UNIX98_PTYS
 607 static struct cdev ptmx_cdev;
 608
 609 /**
 610  *      pty_open_peer - open the peer of a pty
 611  *      @tty: the peer of the pty being opened
 612  *
 613  *      Open the cached dentry in tty->link, providing a safe way for userspace
 614  *      to get the slave end of a pty (where they have the master fd and cannot
 615  *      access or trust the mount namespace /dev/pts was mounted inside).
 616  */
 617 static struct file *pty_open_peer(struct tty_struct *tty, int flags)
 618 {
 619         if (tty->driver->subtype != PTY_TYPE_MASTER)
 620                 return ERR_PTR(-EIO);
 621         return dentry_open(tty->link->driver_data, flags, current_cred());
 622 }
 623
 624 static int pty_get_peer(struct tty_struct *tty, int flags)
 625 {
 626         int fd = -1;
 627         struct file *filp = NULL;
 628         int retval = -EINVAL;
 629
 630         fd = get_unused_fd_flags(0);
 631         if (fd < 0) {
 632                 retval = fd;
 633                 goto err;
 634         }
 635
 636         filp = pty_open_peer(tty, flags);
 637         if (IS_ERR(filp)) {
 638                 retval = PTR_ERR(filp);
 639                 goto err_put;
 640         }
 641
 642         fd_install(fd, filp);
 643         return fd;
 644
 645 err_put:
 646         put_unused_fd(fd);
 647 err:
 648         return retval;
 649 }
 650
 651 static int pty_unix98_ioctl(struct tty_struct *tty,
 652                             unsigned int cmd, unsigned long arg)
 653 {
 654         switch (cmd) {
 655         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 656                 return pty_set_lock(tty, (int __user *)arg);
 657         case TIOCGPTLCK: /* Get PT Lock status */
 658                 return pty_get_lock(tty, (int __user *)arg);
 659         case TIOCPKT: /* Set PT packet mode */
 660                 return pty_set_pktmode(tty, (int __user *)arg);
 661         case TIOCGPKT: /* Get PT packet mode */
 662                 return pty_get_pktmode(tty, (int __user *)arg);
 663         case TIOCGPTN: /* Get PT Number */
 664                 return put_user(tty->index, (unsigned int __user *)arg);
 665         case TIOCGPTPEER: /* Open the other end */
 666                 return pty_get_peer(tty, (int) arg);
 667         case TIOCSIG:    /* Send signal to other side of pty */
 668                 return pty_signal(tty, (int) arg);
 669         }
 670
 671         return -ENOIOCTLCMD;
 672 }
 673
 674 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
 675                                  unsigned int cmd, unsigned long arg)
 676 {
 677         /*
 678          * PTY ioctls don't require any special translation between 32-bit and
 679          * 64-bit userspace, they are already compatible.
 680          */
 681         return pty_unix98_ioctl(tty, cmd, arg);
 682 }
 683
 684 /**
 685  *      ptm_unix98_lookup       -       find a pty master
 686  *      @driver: ptm driver
 687  *      @idx: tty index
 688  *
 689  *      Look up a pty master device. Called under the tty_mutex for now.
 690  *      This provides our locking.
 691  */
 692
 693 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 694                 struct file *file, int idx)
 695 {
 696         /* Master must be open via /dev/ptmx */
 697         return ERR_PTR(-EIO);
 698 }
 699
 700 /**
 701  *      pts_unix98_lookup       -       find a pty slave
 702  *      @driver: pts driver
 703  *      @idx: tty index
 704  *
 705  *      Look up a pty master device. Called under the tty_mutex for now.
 706  *      This provides our locking for the tty pointer.
 707  */
 708
 709 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 710                 struct file *file, int idx)
 711 {
 712         struct tty_struct *tty;
 713
 714         mutex_lock(&devpts_mutex);
 715         tty = devpts_get_priv(file->f_path.dentry);
 716         mutex_unlock(&devpts_mutex);
 717         /* Master must be open before slave */
 718         if (!tty)
 719                 return ERR_PTR(-EIO);
 720         return tty;
 721 }
 722
 723 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 724 {
 725         return pty_common_install(driver, tty, false);
 726 }
 727
 728 /* this is called once with whichever end is closed last */
 729 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 730 {
 731         struct pts_fs_info *fsi;
 732
 733         if (tty->driver->subtype == PTY_TYPE_MASTER)
 734                 fsi = tty->driver_data;
 735         else
 736                 fsi = tty->link->driver_data;
 737
 738         if (fsi) {
 739                 devpts_kill_index(fsi, tty->index);
 740                 devpts_release(fsi);
 741         }
 742 }
 743
 744 static const struct tty_operations ptm_unix98_ops = {
 745         .lookup = ptm_unix98_lookup,
 746         .install = pty_unix98_install,
 747         .remove = pty_unix98_remove,
 748         .open = pty_open,
 749         .close = pty_close,
 750         .write = pty_write,
 751         .write_room = pty_write_room,
 752         .flush_buffer = pty_flush_buffer,
 753         .chars_in_buffer = pty_chars_in_buffer,
 754         .unthrottle = pty_unthrottle,
 755         .ioctl = pty_unix98_ioctl,
 756         .compat_ioctl = pty_unix98_compat_ioctl,
 757         .resize = pty_resize,
 758         .cleanup = pty_cleanup
 759 };
 760
 761 static const struct tty_operations pty_unix98_ops = {
 762         .lookup = pts_unix98_lookup,
 763         .install = pty_unix98_install,
 764         .remove = pty_unix98_remove,
 765         .open = pty_open,
 766         .close = pty_close,
 767         .write = pty_write,
 768         .write_room = pty_write_room,
 769         .flush_buffer = pty_flush_buffer,
 770         .chars_in_buffer = pty_chars_in_buffer,
 771         .unthrottle = pty_unthrottle,
 772         .set_termios = pty_set_termios,
 773         .start = pty_start,
 774         .stop = pty_stop,
 775         .cleanup = pty_cleanup,
 776 };
 777
 778 /**
 779  *      ptmx_open               -       open a unix 98 pty master
 780  *      @inode: inode of device file
 781  *      @filp: file pointer to tty
 782  *
 783  *      Allocate a unix98 pty master device from the ptmx driver.
 784  *
 785  *      Locking: tty_mutex protects the init_dev work. tty->count should
 786  *              protect the rest.
 787  *              allocated_ptys_lock handles the list of free pty numbers
 788  */
 789
 790 static int ptmx_open(struct inode *inode, struct file *filp)
 791 {
 792         struct pts_fs_info *fsi;
 793         struct tty_struct *tty;
 794         struct path *pts_path;
 795         struct dentry *dentry;
 796         struct vfsmount *mnt;
 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, &mnt);
 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 = 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         mntput(mnt);
 871         tty_unlock(tty);
 872         // This will also put-ref the fsi
 873         tty_release(inode, filp);
 874         return retval;
 875 out:
 876         devpts_kill_index(fsi, index);
 877 out_put_fsi:
 878         devpts_release(fsi);
 879         mntput(mnt);
 880 out_free_file:
 881         tty_free_file(filp);
 882         return retval;
 883 }
 884
 885 static struct file_operations ptmx_fops __ro_after_init;
 886
 887 static void __init unix98_pty_init(void)
 888 {
 889         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 890                         TTY_DRIVER_RESET_TERMIOS |
 891                         TTY_DRIVER_REAL_RAW |
 892                         TTY_DRIVER_DYNAMIC_DEV |
 893                         TTY_DRIVER_DEVPTS_MEM |
 894                         TTY_DRIVER_DYNAMIC_ALLOC);
 895         if (IS_ERR(ptm_driver))
 896                 panic("Couldn't allocate Unix98 ptm driver");
 897         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 898                         TTY_DRIVER_RESET_TERMIOS |
 899                         TTY_DRIVER_REAL_RAW |
 900                         TTY_DRIVER_DYNAMIC_DEV |
 901                         TTY_DRIVER_DEVPTS_MEM |
 902                         TTY_DRIVER_DYNAMIC_ALLOC);
 903         if (IS_ERR(pts_driver))
 904                 panic("Couldn't allocate Unix98 pts driver");
 905
 906         ptm_driver->driver_name = "pty_master";
 907         ptm_driver->name = "ptm";
 908         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 909         ptm_driver->minor_start = 0;
 910         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 911         ptm_driver->subtype = PTY_TYPE_MASTER;
 912         ptm_driver->init_termios = tty_std_termios;
 913         ptm_driver->init_termios.c_iflag = 0;
 914         ptm_driver->init_termios.c_oflag = 0;
 915         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 916         ptm_driver->init_termios.c_lflag = 0;
 917         ptm_driver->init_termios.c_ispeed = 38400;
 918         ptm_driver->init_termios.c_ospeed = 38400;
 919         ptm_driver->other = pts_driver;
 920         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 921
 922         pts_driver->driver_name = "pty_slave";
 923         pts_driver->name = "pts";
 924         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 925         pts_driver->minor_start = 0;
 926         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 927         pts_driver->subtype = PTY_TYPE_SLAVE;
 928         pts_driver->init_termios = tty_std_termios;
 929         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 930         pts_driver->init_termios.c_ispeed = 38400;
 931         pts_driver->init_termios.c_ospeed = 38400;
 932         pts_driver->other = ptm_driver;
 933         tty_set_operations(pts_driver, &pty_unix98_ops);
 934
 935         if (tty_register_driver(ptm_driver))
 936                 panic("Couldn't register Unix98 ptm driver");
 937         if (tty_register_driver(pts_driver))
 938                 panic("Couldn't register Unix98 pts driver");
 939
 940         /* Now create the /dev/ptmx special device */
 941         tty_default_fops(&ptmx_fops);
 942         ptmx_fops.open = ptmx_open;
 943
 944         cdev_init(&ptmx_cdev, &ptmx_fops);
 945         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 946             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 947                 panic("Couldn't register /dev/ptmx driver");
 948         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 949 }
 950
 951 #else
 952 static inline void unix98_pty_init(void) { }
 953 #endif
 954
 955 static int __init pty_init(void)
 956 {
 957         legacy_pty_init();
 958         unix98_pty_init();
 959         return 0;
 960 }
 961 device_initcall(pty_init);