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