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         unsigned long flags;
 110
 111         if (tty->stopped)
 112                 return 0;
 113
 114         if (c > 0) {
 115                 spin_lock_irqsave(&to->port->lock, flags);
 116                 /* Stuff the data into the input queue of the other end */
 117                 c = tty_insert_flip_string(to->port, buf, c);
 118                 /* And shovel */
 119                 if (c)
 120                         tty_flip_buffer_push(to->port);
 121                 spin_unlock_irqrestore(&to->port->lock, flags);
 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 int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 488 /*
 489  * not really modular, but the easiest way to keep compat with existing
 490  * bootargs behaviour is to continue using module_param here.
 491  */
 492 module_param(legacy_count, int, 0);
 493
 494 /*
 495  * The master side of a pty can do TIOCSPTLCK and thus
 496  * has pty_bsd_ioctl.
 497  */
 498 static const struct tty_operations master_pty_ops_bsd = {
 499         .install = pty_install,
 500         .open = pty_open,
 501         .close = pty_close,
 502         .write = pty_write,
 503         .write_room = pty_write_room,
 504         .flush_buffer = pty_flush_buffer,
 505         .chars_in_buffer = pty_chars_in_buffer,
 506         .unthrottle = pty_unthrottle,
 507         .ioctl = pty_bsd_ioctl,
 508         .cleanup = pty_cleanup,
 509         .resize = pty_resize,
 510         .remove = pty_remove
 511 };
 512
 513 static const struct tty_operations slave_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         .set_termios = pty_set_termios,
 523         .cleanup = pty_cleanup,
 524         .resize = pty_resize,
 525         .start = pty_start,
 526         .stop = pty_stop,
 527         .remove = pty_remove
 528 };
 529
 530 static void __init legacy_pty_init(void)
 531 {
 532         struct tty_driver *pty_driver, *pty_slave_driver;
 533
 534         if (legacy_count <= 0)
 535                 return;
 536
 537         pty_driver = tty_alloc_driver(legacy_count,
 538                         TTY_DRIVER_RESET_TERMIOS |
 539                         TTY_DRIVER_REAL_RAW |
 540                         TTY_DRIVER_DYNAMIC_ALLOC);
 541         if (IS_ERR(pty_driver))
 542                 panic("Couldn't allocate pty driver");
 543
 544         pty_slave_driver = tty_alloc_driver(legacy_count,
 545                         TTY_DRIVER_RESET_TERMIOS |
 546                         TTY_DRIVER_REAL_RAW |
 547                         TTY_DRIVER_DYNAMIC_ALLOC);
 548         if (IS_ERR(pty_slave_driver))
 549                 panic("Couldn't allocate pty slave driver");
 550
 551         pty_driver->driver_name = "pty_master";
 552         pty_driver->name = "pty";
 553         pty_driver->major = PTY_MASTER_MAJOR;
 554         pty_driver->minor_start = 0;
 555         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 556         pty_driver->subtype = PTY_TYPE_MASTER;
 557         pty_driver->init_termios = tty_std_termios;
 558         pty_driver->init_termios.c_iflag = 0;
 559         pty_driver->init_termios.c_oflag = 0;
 560         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 561         pty_driver->init_termios.c_lflag = 0;
 562         pty_driver->init_termios.c_ispeed = 38400;
 563         pty_driver->init_termios.c_ospeed = 38400;
 564         pty_driver->other = pty_slave_driver;
 565         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 566
 567         pty_slave_driver->driver_name = "pty_slave";
 568         pty_slave_driver->name = "ttyp";
 569         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 570         pty_slave_driver->minor_start = 0;
 571         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 572         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 573         pty_slave_driver->init_termios = tty_std_termios;
 574         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 575         pty_slave_driver->init_termios.c_ispeed = 38400;
 576         pty_slave_driver->init_termios.c_ospeed = 38400;
 577         pty_slave_driver->other = pty_driver;
 578         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 579
 580         if (tty_register_driver(pty_driver))
 581                 panic("Couldn't register pty driver");
 582         if (tty_register_driver(pty_slave_driver))
 583                 panic("Couldn't register pty slave driver");
 584 }
 585 #else
 586 static inline void legacy_pty_init(void) { }
 587 #endif
 588
 589 /* Unix98 devices */
 590 #ifdef CONFIG_UNIX98_PTYS
 591
 592 static struct cdev ptmx_cdev;
 593
 594 static int pty_unix98_ioctl(struct tty_struct *tty,
 595                             unsigned int cmd, unsigned long arg)
 596 {
 597         switch (cmd) {
 598         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 599                 return pty_set_lock(tty, (int __user *)arg);
 600         case TIOCGPTLCK: /* Get PT Lock status */
 601                 return pty_get_lock(tty, (int __user *)arg);
 602         case TIOCPKT: /* Set PT packet mode */
 603                 return pty_set_pktmode(tty, (int __user *)arg);
 604         case TIOCGPKT: /* Get PT packet mode */
 605                 return pty_get_pktmode(tty, (int __user *)arg);
 606         case TIOCGPTN: /* Get PT Number */
 607                 return put_user(tty->index, (unsigned int __user *)arg);
 608         case TIOCSIG:    /* Send signal to other side of pty */
 609                 return pty_signal(tty, (int) arg);
 610         }
 611
 612         return -ENOIOCTLCMD;
 613 }
 614
 615 /**
 616  *      ptm_unix98_lookup       -       find a pty master
 617  *      @driver: ptm driver
 618  *      @idx: tty index
 619  *
 620  *      Look up a pty master device. Called under the tty_mutex for now.
 621  *      This provides our locking.
 622  */
 623
 624 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 625                 struct file *file, int idx)
 626 {
 627         /* Master must be open via /dev/ptmx */
 628         return ERR_PTR(-EIO);
 629 }
 630
 631 /**
 632  *      pts_unix98_lookup       -       find a pty slave
 633  *      @driver: pts driver
 634  *      @idx: tty index
 635  *
 636  *      Look up a pty master device. Called under the tty_mutex for now.
 637  *      This provides our locking for the tty pointer.
 638  */
 639
 640 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 641                 struct file *file, int idx)
 642 {
 643         struct tty_struct *tty;
 644
 645         mutex_lock(&devpts_mutex);
 646         tty = devpts_get_priv(file->f_path.dentry);
 647         mutex_unlock(&devpts_mutex);
 648         /* Master must be open before slave */
 649         if (!tty)
 650                 return ERR_PTR(-EIO);
 651         return tty;
 652 }
 653
 654 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 655 {
 656         return pty_common_install(driver, tty, false);
 657 }
 658
 659 /* this is called once with whichever end is closed last */
 660 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 661 {
 662         struct pts_fs_info *fsi;
 663
 664         if (tty->driver->subtype == PTY_TYPE_MASTER)
 665                 fsi = tty->driver_data;
 666         else
 667                 fsi = tty->link->driver_data;
 668
 669         if (fsi) {
 670                 devpts_kill_index(fsi, tty->index);
 671                 devpts_release(fsi);
 672         }
 673 }
 674
 675 static const struct tty_operations ptm_unix98_ops = {
 676         .lookup = ptm_unix98_lookup,
 677         .install = pty_unix98_install,
 678         .remove = pty_unix98_remove,
 679         .open = pty_open,
 680         .close = pty_close,
 681         .write = pty_write,
 682         .write_room = pty_write_room,
 683         .flush_buffer = pty_flush_buffer,
 684         .chars_in_buffer = pty_chars_in_buffer,
 685         .unthrottle = pty_unthrottle,
 686         .ioctl = pty_unix98_ioctl,
 687         .resize = pty_resize,
 688         .cleanup = pty_cleanup
 689 };
 690
 691 static const struct tty_operations pty_unix98_ops = {
 692         .lookup = pts_unix98_lookup,
 693         .install = pty_unix98_install,
 694         .remove = pty_unix98_remove,
 695         .open = pty_open,
 696         .close = pty_close,
 697         .write = pty_write,
 698         .write_room = pty_write_room,
 699         .flush_buffer = pty_flush_buffer,
 700         .chars_in_buffer = pty_chars_in_buffer,
 701         .unthrottle = pty_unthrottle,
 702         .set_termios = pty_set_termios,
 703         .start = pty_start,
 704         .stop = pty_stop,
 705         .cleanup = pty_cleanup,
 706 };
 707
 708 /**
 709  *      ptmx_open               -       open a unix 98 pty master
 710  *      @inode: inode of device file
 711  *      @filp: file pointer to tty
 712  *
 713  *      Allocate a unix98 pty master device from the ptmx driver.
 714  *
 715  *      Locking: tty_mutex protects the init_dev work. tty->count should
 716  *              protect the rest.
 717  *              allocated_ptys_lock handles the list of free pty numbers
 718  */
 719
 720 static int ptmx_open(struct inode *inode, struct file *filp)
 721 {
 722         struct pts_fs_info *fsi;
 723         struct tty_struct *tty;
 724         struct dentry *dentry;
 725         int retval;
 726         int index;
 727
 728         nonseekable_open(inode, filp);
 729
 730         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 731         filp->f_mode |= FMODE_NONOTIFY;
 732
 733         retval = tty_alloc_file(filp);
 734         if (retval)
 735                 return retval;
 736
 737         fsi = devpts_acquire(filp);
 738         if (IS_ERR(fsi)) {
 739                 retval = PTR_ERR(fsi);
 740                 goto out_free_file;
 741         }
 742
 743         /* find a device that is not in use. */
 744         mutex_lock(&devpts_mutex);
 745         index = devpts_new_index(fsi);
 746         mutex_unlock(&devpts_mutex);
 747
 748         retval = index;
 749         if (index < 0)
 750                 goto out_put_fsi;
 751
 752
 753         mutex_lock(&tty_mutex);
 754         tty = tty_init_dev(ptm_driver, index);
 755         /* The tty returned here is locked so we can safely
 756            drop the mutex */
 757         mutex_unlock(&tty_mutex);
 758
 759         retval = PTR_ERR(tty);
 760         if (IS_ERR(tty))
 761                 goto out;
 762
 763         /*
 764          * From here on out, the tty is "live", and the index and
 765          * fsi will be killed/put by the tty_release()
 766          */
 767         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 768         tty->driver_data = fsi;
 769
 770         tty_add_file(tty, filp);
 771
 772         dentry = devpts_pty_new(fsi, index, tty->link);
 773         if (IS_ERR(dentry)) {
 774                 retval = PTR_ERR(dentry);
 775                 goto err_release;
 776         }
 777         tty->link->driver_data = dentry;
 778
 779         retval = ptm_driver->ops->open(tty, filp);
 780         if (retval)
 781                 goto err_release;
 782
 783         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 784
 785         tty_unlock(tty);
 786         return 0;
 787 err_release:
 788         tty_unlock(tty);
 789         // This will also put-ref the fsi
 790         tty_release(inode, filp);
 791         return retval;
 792 out:
 793         devpts_kill_index(fsi, index);
 794 out_put_fsi:
 795         devpts_release(fsi);
 796 out_free_file:
 797         tty_free_file(filp);
 798         return retval;
 799 }
 800
 801 static struct file_operations ptmx_fops __ro_after_init;
 802
 803 static void __init unix98_pty_init(void)
 804 {
 805         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 806                         TTY_DRIVER_RESET_TERMIOS |
 807                         TTY_DRIVER_REAL_RAW |
 808                         TTY_DRIVER_DYNAMIC_DEV |
 809                         TTY_DRIVER_DEVPTS_MEM |
 810                         TTY_DRIVER_DYNAMIC_ALLOC);
 811         if (IS_ERR(ptm_driver))
 812                 panic("Couldn't allocate Unix98 ptm driver");
 813         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 814                         TTY_DRIVER_RESET_TERMIOS |
 815                         TTY_DRIVER_REAL_RAW |
 816                         TTY_DRIVER_DYNAMIC_DEV |
 817                         TTY_DRIVER_DEVPTS_MEM |
 818                         TTY_DRIVER_DYNAMIC_ALLOC);
 819         if (IS_ERR(pts_driver))
 820                 panic("Couldn't allocate Unix98 pts driver");
 821
 822         ptm_driver->driver_name = "pty_master";
 823         ptm_driver->name = "ptm";
 824         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 825         ptm_driver->minor_start = 0;
 826         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 827         ptm_driver->subtype = PTY_TYPE_MASTER;
 828         ptm_driver->init_termios = tty_std_termios;
 829         ptm_driver->init_termios.c_iflag = 0;
 830         ptm_driver->init_termios.c_oflag = 0;
 831         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 832         ptm_driver->init_termios.c_lflag = 0;
 833         ptm_driver->init_termios.c_ispeed = 38400;
 834         ptm_driver->init_termios.c_ospeed = 38400;
 835         ptm_driver->other = pts_driver;
 836         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 837
 838         pts_driver->driver_name = "pty_slave";
 839         pts_driver->name = "pts";
 840         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 841         pts_driver->minor_start = 0;
 842         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 843         pts_driver->subtype = PTY_TYPE_SLAVE;
 844         pts_driver->init_termios = tty_std_termios;
 845         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 846         pts_driver->init_termios.c_ispeed = 38400;
 847         pts_driver->init_termios.c_ospeed = 38400;
 848         pts_driver->other = ptm_driver;
 849         tty_set_operations(pts_driver, &pty_unix98_ops);
 850
 851         if (tty_register_driver(ptm_driver))
 852                 panic("Couldn't register Unix98 ptm driver");
 853         if (tty_register_driver(pts_driver))
 854                 panic("Couldn't register Unix98 pts driver");
 855
 856         /* Now create the /dev/ptmx special device */
 857         tty_default_fops(&ptmx_fops);
 858         ptmx_fops.open = ptmx_open;
 859
 860         cdev_init(&ptmx_cdev, &ptmx_fops);
 861         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 862             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 863                 panic("Couldn't register /dev/ptmx driver");
 864         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 865 }
 866
 867 #else
 868 static inline void unix98_pty_init(void) { }
 869 #endif
 870
 871 static int __init pty_init(void)
 872 {
 873         legacy_pty_init();
 874         unix98_pty_init();
 875         return 0;
 876 }
 877 device_initcall(pty_init);