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                                 devpts_pty_kill(tty->link->driver_data);
  74                         mutex_unlock(&devpts_mutex);
  75                 }
  76 #endif
  77                 tty_vhangup(tty->link);
  78         }
  79 }
  80
  81 /*
  82  * The unthrottle routine is called by the line discipline to signal
  83  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  84  * flag is always set, to force the line discipline to always call the
  85  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  86  * characters in the queue.  This is necessary since each time this
  87  * happens, we need to wake up any sleeping processes that could be
  88  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  89  * for the pty buffer to be drained.
  90  */
  91 static void pty_unthrottle(struct tty_struct *tty)
  92 {
  93         tty_wakeup(tty->link);
  94         set_bit(TTY_THROTTLED, &tty->flags);
  95 }
  96
  97 /**
  98  *      pty_write               -       write to a pty
  99  *      @tty: the tty we write from
 100  *      @buf: kernel buffer of data
 101  *      @count: bytes to write
 102  *
 103  *      Our "hardware" write method. Data is coming from the ldisc which
 104  *      may be in a non sleeping state. We simply throw this at the other
 105  *      end of the link as if we were an IRQ handler receiving stuff for
 106  *      the other side of the pty/tty pair.
 107  */
 108
 109 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 110 {
 111         struct tty_struct *to = tty->link;
 112
 113         if (tty->stopped)
 114                 return 0;
 115
 116         if (c > 0) {
 117                 /* Stuff the data into the input queue of the other end */
 118                 c = tty_insert_flip_string(to->port, buf, c);
 119                 /* And shovel */
 120                 if (c)
 121                         tty_flip_buffer_push(to->port);
 122         }
 123         return c;
 124 }
 125
 126 /**
 127  *      pty_write_room  -       write space
 128  *      @tty: tty we are writing from
 129  *
 130  *      Report how many bytes the ldisc can send into the queue for
 131  *      the other device.
 132  */
 133
 134 static int pty_write_room(struct tty_struct *tty)
 135 {
 136         if (tty->stopped)
 137                 return 0;
 138         return tty_buffer_space_avail(tty->link->port);
 139 }
 140
 141 /**
 142  *      pty_chars_in_buffer     -       characters currently in our tx queue
 143  *      @tty: our tty
 144  *
 145  *      Report how much we have in the transmit queue. As everything is
 146  *      instantly at the other end this is easy to implement.
 147  */
 148
 149 static int pty_chars_in_buffer(struct tty_struct *tty)
 150 {
 151         return 0;
 152 }
 153
 154 /* Set the lock flag on a pty */
 155 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 156 {
 157         int val;
 158         if (get_user(val, arg))
 159                 return -EFAULT;
 160         if (val)
 161                 set_bit(TTY_PTY_LOCK, &tty->flags);
 162         else
 163                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 164         return 0;
 165 }
 166
 167 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 168 {
 169         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 170         return put_user(locked, arg);
 171 }
 172
 173 /* Set the packet mode on a pty */
 174 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 175 {
 176         int pktmode;
 177
 178         if (get_user(pktmode, arg))
 179                 return -EFAULT;
 180
 181         spin_lock_irq(&tty->ctrl_lock);
 182         if (pktmode) {
 183                 if (!tty->packet) {
 184                         tty->link->ctrl_status = 0;
 185                         smp_mb();
 186                         tty->packet = 1;
 187                 }
 188         } else
 189                 tty->packet = 0;
 190         spin_unlock_irq(&tty->ctrl_lock);
 191
 192         return 0;
 193 }
 194
 195 /* Get the packet mode of a pty */
 196 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 197 {
 198         int pktmode = tty->packet;
 199         return put_user(pktmode, arg);
 200 }
 201
 202 /* Send a signal to the slave */
 203 static int pty_signal(struct tty_struct *tty, int sig)
 204 {
 205         struct pid *pgrp;
 206
 207         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 208                 return -EINVAL;
 209
 210         if (tty->link) {
 211                 pgrp = tty_get_pgrp(tty->link);
 212                 if (pgrp)
 213                         kill_pgrp(pgrp, sig, 1);
 214                 put_pid(pgrp);
 215         }
 216         return 0;
 217 }
 218
 219 static void pty_flush_buffer(struct tty_struct *tty)
 220 {
 221         struct tty_struct *to = tty->link;
 222
 223         if (!to)
 224                 return;
 225
 226         tty_buffer_flush(to, NULL);
 227         if (to->packet) {
 228                 spin_lock_irq(&tty->ctrl_lock);
 229                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 230                 wake_up_interruptible(&to->read_wait);
 231                 spin_unlock_irq(&tty->ctrl_lock);
 232         }
 233 }
 234
 235 static int pty_open(struct tty_struct *tty, struct file *filp)
 236 {
 237         if (!tty || !tty->link)
 238                 return -ENODEV;
 239
 240         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 241                 goto out;
 242         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 243                 goto out;
 244         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 245                 goto out;
 246
 247         clear_bit(TTY_IO_ERROR, &tty->flags);
 248         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 249         set_bit(TTY_THROTTLED, &tty->flags);
 250         return 0;
 251
 252 out:
 253         set_bit(TTY_IO_ERROR, &tty->flags);
 254         return -EIO;
 255 }
 256
 257 static void pty_set_termios(struct tty_struct *tty,
 258                                         struct ktermios *old_termios)
 259 {
 260         /* See if packet mode change of state. */
 261         if (tty->link && tty->link->packet) {
 262                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
 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                 tty_init_termios(tty);
 405                 tty_init_termios(o_tty);
 406
 407                 driver->other->ttys[idx] = o_tty;
 408                 driver->ttys[idx] = tty;
 409         } else {
 410                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 411                 tty->termios = driver->init_termios;
 412                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 413                 o_tty->termios = driver->other->init_termios;
 414         }
 415
 416         /*
 417          * Everything allocated ... set up the o_tty structure.
 418          */
 419         tty_driver_kref_get(driver->other);
 420         /* Establish the links in both directions */
 421         tty->link   = o_tty;
 422         o_tty->link = tty;
 423         tty_port_init(ports[0]);
 424         tty_port_init(ports[1]);
 425         tty_buffer_set_limit(ports[0], 8192);
 426         tty_buffer_set_limit(ports[1], 8192);
 427         o_tty->port = ports[0];
 428         tty->port = ports[1];
 429         o_tty->port->itty = o_tty;
 430
 431         tty_buffer_set_lock_subclass(o_tty->port);
 432
 433         tty_driver_kref_get(driver);
 434         tty->count++;
 435         o_tty->count++;
 436         return 0;
 437
 438 err_put_module:
 439         module_put(driver->other->owner);
 440 err:
 441         kfree(ports[0]);
 442         kfree(ports[1]);
 443         return retval;
 444 }
 445
 446 static void pty_cleanup(struct tty_struct *tty)
 447 {
 448         tty_port_put(tty->port);
 449 }
 450
 451 /* Traditional BSD devices */
 452 #ifdef CONFIG_LEGACY_PTYS
 453
 454 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 455 {
 456         return pty_common_install(driver, tty, true);
 457 }
 458
 459 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 460 {
 461         struct tty_struct *pair = tty->link;
 462         driver->ttys[tty->index] = NULL;
 463         if (pair)
 464                 pair->driver->ttys[pair->index] = NULL;
 465 }
 466
 467 static int pty_bsd_ioctl(struct tty_struct *tty,
 468                          unsigned int cmd, unsigned long arg)
 469 {
 470         switch (cmd) {
 471         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 472                 return pty_set_lock(tty, (int __user *) arg);
 473         case TIOCGPTLCK: /* Get PT Lock status */
 474                 return pty_get_lock(tty, (int __user *)arg);
 475         case TIOCPKT: /* Set PT packet mode */
 476                 return pty_set_pktmode(tty, (int __user *)arg);
 477         case TIOCGPKT: /* Get PT packet mode */
 478                 return pty_get_pktmode(tty, (int __user *)arg);
 479         case TIOCSIG:    /* Send signal to other side of pty */
 480                 return pty_signal(tty, (int) arg);
 481         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 482                 return -EINVAL;
 483         }
 484         return -ENOIOCTLCMD;
 485 }
 486
 487 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
 488                                  unsigned int cmd, unsigned long arg)
 489 {
 490         /*
 491          * PTY ioctls don't require any special translation between 32-bit and
 492          * 64-bit userspace, they are already compatible.
 493          */
 494         return pty_bsd_ioctl(tty, cmd, arg);
 495 }
 496
 497 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 498 /*
 499  * not really modular, but the easiest way to keep compat with existing
 500  * bootargs behaviour is to continue using module_param here.
 501  */
 502 module_param(legacy_count, int, 0);
 503
 504 /*
 505  * The master side of a pty can do TIOCSPTLCK and thus
 506  * has pty_bsd_ioctl.
 507  */
 508 static const struct tty_operations master_pty_ops_bsd = {
 509         .install = pty_install,
 510         .open = pty_open,
 511         .close = pty_close,
 512         .write = pty_write,
 513         .write_room = pty_write_room,
 514         .flush_buffer = pty_flush_buffer,
 515         .chars_in_buffer = pty_chars_in_buffer,
 516         .unthrottle = pty_unthrottle,
 517         .ioctl = pty_bsd_ioctl,
 518         .compat_ioctl = pty_bsd_compat_ioctl,
 519         .cleanup = pty_cleanup,
 520         .resize = pty_resize,
 521         .remove = pty_remove
 522 };
 523
 524 static const struct tty_operations slave_pty_ops_bsd = {
 525         .install = pty_install,
 526         .open = pty_open,
 527         .close = pty_close,
 528         .write = pty_write,
 529         .write_room = pty_write_room,
 530         .flush_buffer = pty_flush_buffer,
 531         .chars_in_buffer = pty_chars_in_buffer,
 532         .unthrottle = pty_unthrottle,
 533         .set_termios = pty_set_termios,
 534         .cleanup = pty_cleanup,
 535         .resize = pty_resize,
 536         .start = pty_start,
 537         .stop = pty_stop,
 538         .remove = pty_remove
 539 };
 540
 541 static void __init legacy_pty_init(void)
 542 {
 543         struct tty_driver *pty_driver, *pty_slave_driver;
 544
 545         if (legacy_count <= 0)
 546                 return;
 547
 548         pty_driver = tty_alloc_driver(legacy_count,
 549                         TTY_DRIVER_RESET_TERMIOS |
 550                         TTY_DRIVER_REAL_RAW |
 551                         TTY_DRIVER_DYNAMIC_ALLOC);
 552         if (IS_ERR(pty_driver))
 553                 panic("Couldn't allocate pty driver");
 554
 555         pty_slave_driver = tty_alloc_driver(legacy_count,
 556                         TTY_DRIVER_RESET_TERMIOS |
 557                         TTY_DRIVER_REAL_RAW |
 558                         TTY_DRIVER_DYNAMIC_ALLOC);
 559         if (IS_ERR(pty_slave_driver))
 560                 panic("Couldn't allocate pty slave driver");
 561
 562         pty_driver->driver_name = "pty_master";
 563         pty_driver->name = "pty";
 564         pty_driver->major = PTY_MASTER_MAJOR;
 565         pty_driver->minor_start = 0;
 566         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 567         pty_driver->subtype = PTY_TYPE_MASTER;
 568         pty_driver->init_termios = tty_std_termios;
 569         pty_driver->init_termios.c_iflag = 0;
 570         pty_driver->init_termios.c_oflag = 0;
 571         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 572         pty_driver->init_termios.c_lflag = 0;
 573         pty_driver->init_termios.c_ispeed = 38400;
 574         pty_driver->init_termios.c_ospeed = 38400;
 575         pty_driver->other = pty_slave_driver;
 576         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 577
 578         pty_slave_driver->driver_name = "pty_slave";
 579         pty_slave_driver->name = "ttyp";
 580         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 581         pty_slave_driver->minor_start = 0;
 582         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 583         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 584         pty_slave_driver->init_termios = tty_std_termios;
 585         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 586         pty_slave_driver->init_termios.c_ispeed = 38400;
 587         pty_slave_driver->init_termios.c_ospeed = 38400;
 588         pty_slave_driver->other = pty_driver;
 589         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 590
 591         if (tty_register_driver(pty_driver))
 592                 panic("Couldn't register pty driver");
 593         if (tty_register_driver(pty_slave_driver))
 594                 panic("Couldn't register pty slave driver");
 595 }
 596 #else
 597 static inline void legacy_pty_init(void) { }
 598 #endif
 599
 600 /* Unix98 devices */
 601 #ifdef CONFIG_UNIX98_PTYS
 602 static struct cdev ptmx_cdev;
 603
 604 /**
 605  *      ptm_open_peer - open the peer of a pty
 606  *      @master: the open struct file of the ptmx device node
 607  *      @tty: the master of the pty being opened
 608  *      @flags: the flags for open
 609  *
 610  *      Provide a race free way for userspace to open the slave end of a pty
 611  *      (where they have the master fd and cannot access or trust the mount
 612  *      namespace /dev/pts was mounted inside).
 613  */
 614 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
 615 {
 616         int fd = -1;
 617         struct file *filp;
 618         int retval = -EINVAL;
 619         struct path path;
 620
 621         if (tty->driver != ptm_driver)
 622                 return -EIO;
 623
 624         fd = get_unused_fd_flags(0);
 625         if (fd < 0) {
 626                 retval = fd;
 627                 goto err;
 628         }
 629
 630         /* Compute the slave's path */
 631         path.mnt = devpts_mntget(master, tty->driver_data);
 632         if (IS_ERR(path.mnt)) {
 633                 retval = PTR_ERR(path.mnt);
 634                 goto err_put;
 635         }
 636         path.dentry = tty->link->driver_data;
 637
 638         filp = dentry_open(&path, flags, current_cred());
 639         mntput(path.mnt);
 640         if (IS_ERR(filp)) {
 641                 retval = PTR_ERR(filp);
 642                 goto err_put;
 643         }
 644
 645         fd_install(fd, filp);
 646         return fd;
 647
 648 err_put:
 649         put_unused_fd(fd);
 650 err:
 651         return retval;
 652 }
 653
 654 static int pty_unix98_ioctl(struct tty_struct *tty,
 655                             unsigned int cmd, unsigned long arg)
 656 {
 657         switch (cmd) {
 658         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 659                 return pty_set_lock(tty, (int __user *)arg);
 660         case TIOCGPTLCK: /* Get PT Lock status */
 661                 return pty_get_lock(tty, (int __user *)arg);
 662         case TIOCPKT: /* Set PT packet mode */
 663                 return pty_set_pktmode(tty, (int __user *)arg);
 664         case TIOCGPKT: /* Get PT packet mode */
 665                 return pty_get_pktmode(tty, (int __user *)arg);
 666         case TIOCGPTN: /* Get PT Number */
 667                 return put_user(tty->index, (unsigned int __user *)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 void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
 746 {
 747         seq_printf(m, "tty-index:\t%d\n", tty->index);
 748 }
 749
 750 static const struct tty_operations ptm_unix98_ops = {
 751         .lookup = ptm_unix98_lookup,
 752         .install = pty_unix98_install,
 753         .remove = pty_unix98_remove,
 754         .open = pty_open,
 755         .close = pty_close,
 756         .write = pty_write,
 757         .write_room = pty_write_room,
 758         .flush_buffer = pty_flush_buffer,
 759         .chars_in_buffer = pty_chars_in_buffer,
 760         .unthrottle = pty_unthrottle,
 761         .ioctl = pty_unix98_ioctl,
 762         .compat_ioctl = pty_unix98_compat_ioctl,
 763         .resize = pty_resize,
 764         .cleanup = pty_cleanup,
 765         .show_fdinfo = pty_show_fdinfo,
 766 };
 767
 768 static const struct tty_operations pty_unix98_ops = {
 769         .lookup = pts_unix98_lookup,
 770         .install = pty_unix98_install,
 771         .remove = pty_unix98_remove,
 772         .open = pty_open,
 773         .close = pty_close,
 774         .write = pty_write,
 775         .write_room = pty_write_room,
 776         .flush_buffer = pty_flush_buffer,
 777         .chars_in_buffer = pty_chars_in_buffer,
 778         .unthrottle = pty_unthrottle,
 779         .set_termios = pty_set_termios,
 780         .start = pty_start,
 781         .stop = pty_stop,
 782         .cleanup = pty_cleanup,
 783 };
 784
 785 /**
 786  *      ptmx_open               -       open a unix 98 pty master
 787  *      @inode: inode of device file
 788  *      @filp: file pointer to tty
 789  *
 790  *      Allocate a unix98 pty master device from the ptmx driver.
 791  *
 792  *      Locking: tty_mutex protects the init_dev work. tty->count should
 793  *              protect the rest.
 794  *              allocated_ptys_lock handles the list of free pty numbers
 795  */
 796
 797 static int ptmx_open(struct inode *inode, struct file *filp)
 798 {
 799         struct pts_fs_info *fsi;
 800         struct tty_struct *tty;
 801         struct dentry *dentry;
 802         int retval;
 803         int index;
 804
 805         nonseekable_open(inode, filp);
 806
 807         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 808         filp->f_mode |= FMODE_NONOTIFY;
 809
 810         retval = tty_alloc_file(filp);
 811         if (retval)
 812                 return retval;
 813
 814         fsi = devpts_acquire(filp);
 815         if (IS_ERR(fsi)) {
 816                 retval = PTR_ERR(fsi);
 817                 goto out_free_file;
 818         }
 819
 820         /* find a device that is not in use. */
 821         mutex_lock(&devpts_mutex);
 822         index = devpts_new_index(fsi);
 823         mutex_unlock(&devpts_mutex);
 824
 825         retval = index;
 826         if (index < 0)
 827                 goto out_put_fsi;
 828
 829
 830         mutex_lock(&tty_mutex);
 831         tty = tty_init_dev(ptm_driver, index);
 832         /* The tty returned here is locked so we can safely
 833            drop the mutex */
 834         mutex_unlock(&tty_mutex);
 835
 836         retval = PTR_ERR(tty);
 837         if (IS_ERR(tty))
 838                 goto out;
 839
 840         /*
 841          * From here on out, the tty is "live", and the index and
 842          * fsi will be killed/put by the tty_release()
 843          */
 844         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 845         tty->driver_data = fsi;
 846
 847         tty_add_file(tty, filp);
 848
 849         dentry = devpts_pty_new(fsi, index, tty->link);
 850         if (IS_ERR(dentry)) {
 851                 retval = PTR_ERR(dentry);
 852                 goto err_release;
 853         }
 854         tty->link->driver_data = dentry;
 855
 856         retval = ptm_driver->ops->open(tty, filp);
 857         if (retval)
 858                 goto err_release;
 859
 860         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 861
 862         tty_unlock(tty);
 863         return 0;
 864 err_release:
 865         tty_unlock(tty);
 866         // This will also put-ref the fsi
 867         tty_release(inode, filp);
 868         return retval;
 869 out:
 870         devpts_kill_index(fsi, index);
 871 out_put_fsi:
 872         devpts_release(fsi);
 873 out_free_file:
 874         tty_free_file(filp);
 875         return retval;
 876 }
 877
 878 static struct file_operations ptmx_fops __ro_after_init;
 879
 880 static void __init unix98_pty_init(void)
 881 {
 882         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 883                         TTY_DRIVER_RESET_TERMIOS |
 884                         TTY_DRIVER_REAL_RAW |
 885                         TTY_DRIVER_DYNAMIC_DEV |
 886                         TTY_DRIVER_DEVPTS_MEM |
 887                         TTY_DRIVER_DYNAMIC_ALLOC);
 888         if (IS_ERR(ptm_driver))
 889                 panic("Couldn't allocate Unix98 ptm driver");
 890         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 891                         TTY_DRIVER_RESET_TERMIOS |
 892                         TTY_DRIVER_REAL_RAW |
 893                         TTY_DRIVER_DYNAMIC_DEV |
 894                         TTY_DRIVER_DEVPTS_MEM |
 895                         TTY_DRIVER_DYNAMIC_ALLOC);
 896         if (IS_ERR(pts_driver))
 897                 panic("Couldn't allocate Unix98 pts driver");
 898
 899         ptm_driver->driver_name = "pty_master";
 900         ptm_driver->name = "ptm";
 901         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 902         ptm_driver->minor_start = 0;
 903         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 904         ptm_driver->subtype = PTY_TYPE_MASTER;
 905         ptm_driver->init_termios = tty_std_termios;
 906         ptm_driver->init_termios.c_iflag = 0;
 907         ptm_driver->init_termios.c_oflag = 0;
 908         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 909         ptm_driver->init_termios.c_lflag = 0;
 910         ptm_driver->init_termios.c_ispeed = 38400;
 911         ptm_driver->init_termios.c_ospeed = 38400;
 912         ptm_driver->other = pts_driver;
 913         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 914
 915         pts_driver->driver_name = "pty_slave";
 916         pts_driver->name = "pts";
 917         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 918         pts_driver->minor_start = 0;
 919         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 920         pts_driver->subtype = PTY_TYPE_SLAVE;
 921         pts_driver->init_termios = tty_std_termios;
 922         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 923         pts_driver->init_termios.c_ispeed = 38400;
 924         pts_driver->init_termios.c_ospeed = 38400;
 925         pts_driver->other = ptm_driver;
 926         tty_set_operations(pts_driver, &pty_unix98_ops);
 927
 928         if (tty_register_driver(ptm_driver))
 929                 panic("Couldn't register Unix98 ptm driver");
 930         if (tty_register_driver(pts_driver))
 931                 panic("Couldn't register Unix98 pts driver");
 932
 933         /* Now create the /dev/ptmx special device */
 934         tty_default_fops(&ptmx_fops);
 935         ptmx_fops.open = ptmx_open;
 936
 937         cdev_init(&ptmx_cdev, &ptmx_fops);
 938         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 939             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 940                 panic("Couldn't register /dev/ptmx driver");
 941         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 942 }
 943
 944 #else
 945 static inline void unix98_pty_init(void) { }
 946 #endif
 947
 948 static int __init pty_init(void)
 949 {
 950         legacy_pty_init();
 951         unix98_pty_init();
 952         return 0;
 953 }
 954 device_initcall(pty_init);