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)
 111                 return 0;
 112
 113         if (c > 0) {
 114                 /* Stuff the data into the input queue of the other end */
 115                 c = tty_insert_flip_string(to->port, buf, c);
 116                 /* And shovel */
 117                 if (c)
 118                         tty_flip_buffer_push(to->port);
 119         }
 120         return c;
 121 }
 122
 123 /**
 124  *      pty_write_room  -       write space
 125  *      @tty: tty we are writing from
 126  *
 127  *      Report how many bytes the ldisc can send into the queue for
 128  *      the other device.
 129  */
 130
 131 static int pty_write_room(struct tty_struct *tty)
 132 {
 133         if (tty->stopped)
 134                 return 0;
 135         return tty_buffer_space_avail(tty->link->port);
 136 }
 137
 138 /**
 139  *      pty_chars_in_buffer     -       characters currently in our tx queue
 140  *      @tty: our tty
 141  *
 142  *      Report how much we have in the transmit queue. As everything is
 143  *      instantly at the other end this is easy to implement.
 144  */
 145
 146 static int pty_chars_in_buffer(struct tty_struct *tty)
 147 {
 148         return 0;
 149 }
 150
 151 /* Set the lock flag on a pty */
 152 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 153 {
 154         int val;
 155         if (get_user(val, arg))
 156                 return -EFAULT;
 157         if (val)
 158                 set_bit(TTY_PTY_LOCK, &tty->flags);
 159         else
 160                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 161         return 0;
 162 }
 163
 164 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 165 {
 166         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 167         return put_user(locked, arg);
 168 }
 169
 170 /* Set the packet mode on a pty */
 171 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 172 {
 173         int pktmode;
 174
 175         if (get_user(pktmode, arg))
 176                 return -EFAULT;
 177
 178         spin_lock_irq(&tty->ctrl_lock);
 179         if (pktmode) {
 180                 if (!tty->packet) {
 181                         tty->link->ctrl_status = 0;
 182                         smp_mb();
 183                         tty->packet = 1;
 184                 }
 185         } else
 186                 tty->packet = 0;
 187         spin_unlock_irq(&tty->ctrl_lock);
 188
 189         return 0;
 190 }
 191
 192 /* Get the packet mode of a pty */
 193 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 194 {
 195         int pktmode = tty->packet;
 196         return put_user(pktmode, arg);
 197 }
 198
 199 /* Send a signal to the slave */
 200 static int pty_signal(struct tty_struct *tty, int sig)
 201 {
 202         struct pid *pgrp;
 203
 204         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 205                 return -EINVAL;
 206
 207         if (tty->link) {
 208                 pgrp = tty_get_pgrp(tty->link);
 209                 if (pgrp)
 210                         kill_pgrp(pgrp, sig, 1);
 211                 put_pid(pgrp);
 212         }
 213         return 0;
 214 }
 215
 216 static void pty_flush_buffer(struct tty_struct *tty)
 217 {
 218         struct tty_struct *to = tty->link;
 219         struct tty_ldisc *ld;
 220
 221         if (!to)
 222                 return;
 223
 224         ld = tty_ldisc_ref(to);
 225         tty_buffer_flush(to, ld);
 226         if (ld)
 227                 tty_ldisc_deref(ld);
 228
 229         if (to->packet) {
 230                 spin_lock_irq(&tty->ctrl_lock);
 231                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 232                 wake_up_interruptible(&to->read_wait);
 233                 spin_unlock_irq(&tty->ctrl_lock);
 234         }
 235 }
 236
 237 static int pty_open(struct tty_struct *tty, struct file *filp)
 238 {
 239         if (!tty || !tty->link)
 240                 return -ENODEV;
 241
 242         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 243                 goto out;
 244         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 245                 goto out;
 246         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 247                 goto out;
 248
 249         clear_bit(TTY_IO_ERROR, &tty->flags);
 250         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 251         set_bit(TTY_THROTTLED, &tty->flags);
 252         return 0;
 253
 254 out:
 255         set_bit(TTY_IO_ERROR, &tty->flags);
 256         return -EIO;
 257 }
 258
 259 static void pty_set_termios(struct tty_struct *tty,
 260                                         struct ktermios *old_termios)
 261 {
 262         /* See if packet mode change of state. */
 263         if (tty->link && tty->link->packet) {
 264                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
 265                 int old_flow = ((old_termios->c_iflag & IXON) &&
 266                                 (old_termios->c_cc[VSTOP] == '\023') &&
 267                                 (old_termios->c_cc[VSTART] == '\021'));
 268                 int new_flow = (I_IXON(tty) &&
 269                                 STOP_CHAR(tty) == '\023' &&
 270                                 START_CHAR(tty) == '\021');
 271                 if ((old_flow != new_flow) || extproc) {
 272                         spin_lock_irq(&tty->ctrl_lock);
 273                         if (old_flow != new_flow) {
 274                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 275                                 if (new_flow)
 276                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 277                                 else
 278                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 279                         }
 280                         if (extproc)
 281                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 282                         spin_unlock_irq(&tty->ctrl_lock);
 283                         wake_up_interruptible(&tty->link->read_wait);
 284                 }
 285         }
 286
 287         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 288         tty->termios.c_cflag |= (CS8 | CREAD);
 289 }
 290
 291 /**
 292  *      pty_do_resize           -       resize event
 293  *      @tty: tty being resized
 294  *      @ws: window size being set.
 295  *
 296  *      Update the termios variables and send the necessary signals to
 297  *      peform a terminal resize correctly
 298  */
 299
 300 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 301 {
 302         struct pid *pgrp, *rpgrp;
 303         struct tty_struct *pty = tty->link;
 304
 305         /* For a PTY we need to lock the tty side */
 306         mutex_lock(&tty->winsize_mutex);
 307         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 308                 goto done;
 309
 310         /* Signal the foreground process group of both ptys */
 311         pgrp = tty_get_pgrp(tty);
 312         rpgrp = tty_get_pgrp(pty);
 313
 314         if (pgrp)
 315                 kill_pgrp(pgrp, SIGWINCH, 1);
 316         if (rpgrp != pgrp && rpgrp)
 317                 kill_pgrp(rpgrp, SIGWINCH, 1);
 318
 319         put_pid(pgrp);
 320         put_pid(rpgrp);
 321
 322         tty->winsize = *ws;
 323         pty->winsize = *ws;     /* Never used so will go away soon */
 324 done:
 325         mutex_unlock(&tty->winsize_mutex);
 326         return 0;
 327 }
 328
 329 /**
 330  *      pty_start - start() handler
 331  *      pty_stop  - stop() handler
 332  *      @tty: tty being flow-controlled
 333  *
 334  *      Propagates the TIOCPKT status to the master pty.
 335  *
 336  *      NB: only the master pty can be in packet mode so only the slave
 337  *          needs start()/stop() handlers
 338  */
 339 static void pty_start(struct tty_struct *tty)
 340 {
 341         unsigned long flags;
 342
 343         if (tty->link && tty->link->packet) {
 344                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 345                 tty->ctrl_status &= ~TIOCPKT_STOP;
 346                 tty->ctrl_status |= TIOCPKT_START;
 347                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 348                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 349         }
 350 }
 351
 352 static void pty_stop(struct tty_struct *tty)
 353 {
 354         unsigned long flags;
 355
 356         if (tty->link && tty->link->packet) {
 357                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 358                 tty->ctrl_status &= ~TIOCPKT_START;
 359                 tty->ctrl_status |= TIOCPKT_STOP;
 360                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 361                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 362         }
 363 }
 364
 365 /**
 366  *      pty_common_install              -       set up the pty pair
 367  *      @driver: the pty driver
 368  *      @tty: the tty being instantiated
 369  *      @legacy: true if this is BSD style
 370  *
 371  *      Perform the initial set up for the tty/pty pair. Called from the
 372  *      tty layer when the port is first opened.
 373  *
 374  *      Locking: the caller must hold the tty_mutex
 375  */
 376 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 377                 bool legacy)
 378 {
 379         struct tty_struct *o_tty;
 380         struct tty_port *ports[2];
 381         int idx = tty->index;
 382         int retval = -ENOMEM;
 383
 384         /* Opening the slave first has always returned -EIO */
 385         if (driver->subtype != PTY_TYPE_MASTER)
 386                 return -EIO;
 387
 388         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 389         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 390         if (!ports[0] || !ports[1])
 391                 goto err;
 392         if (!try_module_get(driver->other->owner)) {
 393                 /* This cannot in fact currently happen */
 394                 goto err;
 395         }
 396         o_tty = alloc_tty_struct(driver->other, idx);
 397         if (!o_tty)
 398                 goto err_put_module;
 399
 400         tty_set_lock_subclass(o_tty);
 401         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 402
 403         if (legacy) {
 404                 /* We always use new tty termios data so we can do this
 405                    the easy way .. */
 406                 tty_init_termios(tty);
 407                 tty_init_termios(o_tty);
 408
 409                 driver->other->ttys[idx] = o_tty;
 410                 driver->ttys[idx] = tty;
 411         } else {
 412                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 413                 tty->termios = driver->init_termios;
 414                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 415                 o_tty->termios = driver->other->init_termios;
 416         }
 417
 418         /*
 419          * Everything allocated ... set up the o_tty structure.
 420          */
 421         tty_driver_kref_get(driver->other);
 422         /* Establish the links in both directions */
 423         tty->link   = o_tty;
 424         o_tty->link = tty;
 425         tty_port_init(ports[0]);
 426         tty_port_init(ports[1]);
 427         tty_buffer_set_limit(ports[0], 8192);
 428         tty_buffer_set_limit(ports[1], 8192);
 429         o_tty->port = ports[0];
 430         tty->port = ports[1];
 431         o_tty->port->itty = o_tty;
 432
 433         tty_buffer_set_lock_subclass(o_tty->port);
 434
 435         tty_driver_kref_get(driver);
 436         tty->count++;
 437         o_tty->count++;
 438         return 0;
 439
 440 err_put_module:
 441         module_put(driver->other->owner);
 442 err:
 443         kfree(ports[0]);
 444         kfree(ports[1]);
 445         return retval;
 446 }
 447
 448 static void pty_cleanup(struct tty_struct *tty)
 449 {
 450         tty_port_put(tty->port);
 451 }
 452
 453 /* Traditional BSD devices */
 454 #ifdef CONFIG_LEGACY_PTYS
 455
 456 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 457 {
 458         return pty_common_install(driver, tty, true);
 459 }
 460
 461 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 462 {
 463         struct tty_struct *pair = tty->link;
 464         driver->ttys[tty->index] = NULL;
 465         if (pair)
 466                 pair->driver->ttys[pair->index] = NULL;
 467 }
 468
 469 static int pty_bsd_ioctl(struct tty_struct *tty,
 470                          unsigned int cmd, unsigned long arg)
 471 {
 472         switch (cmd) {
 473         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 474                 return pty_set_lock(tty, (int __user *) arg);
 475         case TIOCGPTLCK: /* Get PT Lock status */
 476                 return pty_get_lock(tty, (int __user *)arg);
 477         case TIOCPKT: /* Set PT packet mode */
 478                 return pty_set_pktmode(tty, (int __user *)arg);
 479         case TIOCGPKT: /* Get PT packet mode */
 480                 return pty_get_pktmode(tty, (int __user *)arg);
 481         case TIOCSIG:    /* Send signal to other side of pty */
 482                 return pty_signal(tty, (int) arg);
 483         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 484                 return -EINVAL;
 485         }
 486         return -ENOIOCTLCMD;
 487 }
 488
 489 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 490 /*
 491  * not really modular, but the easiest way to keep compat with existing
 492  * bootargs behaviour is to continue using module_param here.
 493  */
 494 module_param(legacy_count, int, 0);
 495
 496 /*
 497  * The master side of a pty can do TIOCSPTLCK and thus
 498  * has pty_bsd_ioctl.
 499  */
 500 static const struct tty_operations master_pty_ops_bsd = {
 501         .install = pty_install,
 502         .open = pty_open,
 503         .close = pty_close,
 504         .write = pty_write,
 505         .write_room = pty_write_room,
 506         .flush_buffer = pty_flush_buffer,
 507         .chars_in_buffer = pty_chars_in_buffer,
 508         .unthrottle = pty_unthrottle,
 509         .ioctl = pty_bsd_ioctl,
 510         .cleanup = pty_cleanup,
 511         .resize = pty_resize,
 512         .remove = pty_remove
 513 };
 514
 515 static const struct tty_operations slave_pty_ops_bsd = {
 516         .install = pty_install,
 517         .open = pty_open,
 518         .close = pty_close,
 519         .write = pty_write,
 520         .write_room = pty_write_room,
 521         .flush_buffer = pty_flush_buffer,
 522         .chars_in_buffer = pty_chars_in_buffer,
 523         .unthrottle = pty_unthrottle,
 524         .set_termios = pty_set_termios,
 525         .cleanup = pty_cleanup,
 526         .resize = pty_resize,
 527         .start = pty_start,
 528         .stop = pty_stop,
 529         .remove = pty_remove
 530 };
 531
 532 static void __init legacy_pty_init(void)
 533 {
 534         struct tty_driver *pty_driver, *pty_slave_driver;
 535
 536         if (legacy_count <= 0)
 537                 return;
 538
 539         pty_driver = tty_alloc_driver(legacy_count,
 540                         TTY_DRIVER_RESET_TERMIOS |
 541                         TTY_DRIVER_REAL_RAW |
 542                         TTY_DRIVER_DYNAMIC_ALLOC);
 543         if (IS_ERR(pty_driver))
 544                 panic("Couldn't allocate pty driver");
 545
 546         pty_slave_driver = tty_alloc_driver(legacy_count,
 547                         TTY_DRIVER_RESET_TERMIOS |
 548                         TTY_DRIVER_REAL_RAW |
 549                         TTY_DRIVER_DYNAMIC_ALLOC);
 550         if (IS_ERR(pty_slave_driver))
 551                 panic("Couldn't allocate pty slave driver");
 552
 553         pty_driver->driver_name = "pty_master";
 554         pty_driver->name = "pty";
 555         pty_driver->major = PTY_MASTER_MAJOR;
 556         pty_driver->minor_start = 0;
 557         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 558         pty_driver->subtype = PTY_TYPE_MASTER;
 559         pty_driver->init_termios = tty_std_termios;
 560         pty_driver->init_termios.c_iflag = 0;
 561         pty_driver->init_termios.c_oflag = 0;
 562         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 563         pty_driver->init_termios.c_lflag = 0;
 564         pty_driver->init_termios.c_ispeed = 38400;
 565         pty_driver->init_termios.c_ospeed = 38400;
 566         pty_driver->other = pty_slave_driver;
 567         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 568
 569         pty_slave_driver->driver_name = "pty_slave";
 570         pty_slave_driver->name = "ttyp";
 571         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 572         pty_slave_driver->minor_start = 0;
 573         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 574         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 575         pty_slave_driver->init_termios = tty_std_termios;
 576         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 577         pty_slave_driver->init_termios.c_ispeed = 38400;
 578         pty_slave_driver->init_termios.c_ospeed = 38400;
 579         pty_slave_driver->other = pty_driver;
 580         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 581
 582         if (tty_register_driver(pty_driver))
 583                 panic("Couldn't register pty driver");
 584         if (tty_register_driver(pty_slave_driver))
 585                 panic("Couldn't register pty slave driver");
 586 }
 587 #else
 588 static inline void legacy_pty_init(void) { }
 589 #endif
 590
 591 /* Unix98 devices */
 592 #ifdef CONFIG_UNIX98_PTYS
 593
 594 static struct cdev ptmx_cdev;
 595
 596 static int pty_unix98_ioctl(struct tty_struct *tty,
 597                             unsigned int cmd, unsigned long arg)
 598 {
 599         switch (cmd) {
 600         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 601                 return pty_set_lock(tty, (int __user *)arg);
 602         case TIOCGPTLCK: /* Get PT Lock status */
 603                 return pty_get_lock(tty, (int __user *)arg);
 604         case TIOCPKT: /* Set PT packet mode */
 605                 return pty_set_pktmode(tty, (int __user *)arg);
 606         case TIOCGPKT: /* Get PT packet mode */
 607                 return pty_get_pktmode(tty, (int __user *)arg);
 608         case TIOCGPTN: /* Get PT Number */
 609                 return put_user(tty->index, (unsigned int __user *)arg);
 610         case TIOCSIG:    /* Send signal to other side of pty */
 611                 return pty_signal(tty, (int) arg);
 612         }
 613
 614         return -ENOIOCTLCMD;
 615 }
 616
 617 /**
 618  *      ptm_unix98_lookup       -       find a pty master
 619  *      @driver: ptm driver
 620  *      @idx: tty index
 621  *
 622  *      Look up a pty master device. Called under the tty_mutex for now.
 623  *      This provides our locking.
 624  */
 625
 626 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 627                 struct file *file, int idx)
 628 {
 629         /* Master must be open via /dev/ptmx */
 630         return ERR_PTR(-EIO);
 631 }
 632
 633 /**
 634  *      pts_unix98_lookup       -       find a pty slave
 635  *      @driver: pts driver
 636  *      @idx: tty index
 637  *
 638  *      Look up a pty master device. Called under the tty_mutex for now.
 639  *      This provides our locking for the tty pointer.
 640  */
 641
 642 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 643                 struct file *file, int idx)
 644 {
 645         struct tty_struct *tty;
 646
 647         mutex_lock(&devpts_mutex);
 648         tty = devpts_get_priv(file->f_path.dentry);
 649         mutex_unlock(&devpts_mutex);
 650         /* Master must be open before slave */
 651         if (!tty)
 652                 return ERR_PTR(-EIO);
 653         return tty;
 654 }
 655
 656 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 657 {
 658         return pty_common_install(driver, tty, false);
 659 }
 660
 661 /* this is called once with whichever end is closed last */
 662 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 663 {
 664         struct pts_fs_info *fsi;
 665
 666         if (tty->driver->subtype == PTY_TYPE_MASTER)
 667                 fsi = tty->driver_data;
 668         else
 669                 fsi = tty->link->driver_data;
 670
 671         if (fsi) {
 672                 devpts_kill_index(fsi, tty->index);
 673                 devpts_release(fsi);
 674         }
 675 }
 676
 677 static const struct tty_operations ptm_unix98_ops = {
 678         .lookup = ptm_unix98_lookup,
 679         .install = pty_unix98_install,
 680         .remove = pty_unix98_remove,
 681         .open = pty_open,
 682         .close = pty_close,
 683         .write = pty_write,
 684         .write_room = pty_write_room,
 685         .flush_buffer = pty_flush_buffer,
 686         .chars_in_buffer = pty_chars_in_buffer,
 687         .unthrottle = pty_unthrottle,
 688         .ioctl = pty_unix98_ioctl,
 689         .resize = pty_resize,
 690         .cleanup = pty_cleanup
 691 };
 692
 693 static const struct tty_operations pty_unix98_ops = {
 694         .lookup = pts_unix98_lookup,
 695         .install = pty_unix98_install,
 696         .remove = pty_unix98_remove,
 697         .open = pty_open,
 698         .close = pty_close,
 699         .write = pty_write,
 700         .write_room = pty_write_room,
 701         .flush_buffer = pty_flush_buffer,
 702         .chars_in_buffer = pty_chars_in_buffer,
 703         .unthrottle = pty_unthrottle,
 704         .set_termios = pty_set_termios,
 705         .start = pty_start,
 706         .stop = pty_stop,
 707         .cleanup = pty_cleanup,
 708 };
 709
 710 /**
 711  *      ptmx_open               -       open a unix 98 pty master
 712  *      @inode: inode of device file
 713  *      @filp: file pointer to tty
 714  *
 715  *      Allocate a unix98 pty master device from the ptmx driver.
 716  *
 717  *      Locking: tty_mutex protects the init_dev work. tty->count should
 718  *              protect the rest.
 719  *              allocated_ptys_lock handles the list of free pty numbers
 720  */
 721
 722 static int ptmx_open(struct inode *inode, struct file *filp)
 723 {
 724         struct pts_fs_info *fsi;
 725         struct tty_struct *tty;
 726         struct dentry *dentry;
 727         int retval;
 728         int index;
 729
 730         nonseekable_open(inode, filp);
 731
 732         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 733         filp->f_mode |= FMODE_NONOTIFY;
 734
 735         retval = tty_alloc_file(filp);
 736         if (retval)
 737                 return retval;
 738
 739         fsi = devpts_acquire(filp);
 740         if (IS_ERR(fsi)) {
 741                 retval = PTR_ERR(fsi);
 742                 goto out_free_file;
 743         }
 744
 745         /* find a device that is not in use. */
 746         mutex_lock(&devpts_mutex);
 747         index = devpts_new_index(fsi);
 748         mutex_unlock(&devpts_mutex);
 749
 750         retval = index;
 751         if (index < 0)
 752                 goto out_put_fsi;
 753
 754
 755         mutex_lock(&tty_mutex);
 756         tty = tty_init_dev(ptm_driver, index);
 757         /* The tty returned here is locked so we can safely
 758            drop the mutex */
 759         mutex_unlock(&tty_mutex);
 760
 761         retval = PTR_ERR(tty);
 762         if (IS_ERR(tty))
 763                 goto out;
 764
 765         /*
 766          * From here on out, the tty is "live", and the index and
 767          * fsi will be killed/put by the tty_release()
 768          */
 769         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 770         tty->driver_data = fsi;
 771
 772         tty_add_file(tty, filp);
 773
 774         dentry = devpts_pty_new(fsi, index, tty->link);
 775         if (IS_ERR(dentry)) {
 776                 retval = PTR_ERR(dentry);
 777                 goto err_release;
 778         }
 779         tty->link->driver_data = dentry;
 780
 781         retval = ptm_driver->ops->open(tty, filp);
 782         if (retval)
 783                 goto err_release;
 784
 785         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 786
 787         tty_unlock(tty);
 788         return 0;
 789 err_release:
 790         tty_unlock(tty);
 791         // This will also put-ref the fsi
 792         tty_release(inode, filp);
 793         return retval;
 794 out:
 795         devpts_kill_index(fsi, index);
 796 out_put_fsi:
 797         devpts_release(fsi);
 798 out_free_file:
 799         tty_free_file(filp);
 800         return retval;
 801 }
 802
 803 static struct file_operations ptmx_fops __ro_after_init;
 804
 805 static void __init unix98_pty_init(void)
 806 {
 807         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 808                         TTY_DRIVER_RESET_TERMIOS |
 809                         TTY_DRIVER_REAL_RAW |
 810                         TTY_DRIVER_DYNAMIC_DEV |
 811                         TTY_DRIVER_DEVPTS_MEM |
 812                         TTY_DRIVER_DYNAMIC_ALLOC);
 813         if (IS_ERR(ptm_driver))
 814                 panic("Couldn't allocate Unix98 ptm driver");
 815         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 816                         TTY_DRIVER_RESET_TERMIOS |
 817                         TTY_DRIVER_REAL_RAW |
 818                         TTY_DRIVER_DYNAMIC_DEV |
 819                         TTY_DRIVER_DEVPTS_MEM |
 820                         TTY_DRIVER_DYNAMIC_ALLOC);
 821         if (IS_ERR(pts_driver))
 822                 panic("Couldn't allocate Unix98 pts driver");
 823
 824         ptm_driver->driver_name = "pty_master";
 825         ptm_driver->name = "ptm";
 826         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 827         ptm_driver->minor_start = 0;
 828         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 829         ptm_driver->subtype = PTY_TYPE_MASTER;
 830         ptm_driver->init_termios = tty_std_termios;
 831         ptm_driver->init_termios.c_iflag = 0;
 832         ptm_driver->init_termios.c_oflag = 0;
 833         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 834         ptm_driver->init_termios.c_lflag = 0;
 835         ptm_driver->init_termios.c_ispeed = 38400;
 836         ptm_driver->init_termios.c_ospeed = 38400;
 837         ptm_driver->other = pts_driver;
 838         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 839
 840         pts_driver->driver_name = "pty_slave";
 841         pts_driver->name = "pts";
 842         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 843         pts_driver->minor_start = 0;
 844         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 845         pts_driver->subtype = PTY_TYPE_SLAVE;
 846         pts_driver->init_termios = tty_std_termios;
 847         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 848         pts_driver->init_termios.c_ispeed = 38400;
 849         pts_driver->init_termios.c_ospeed = 38400;
 850         pts_driver->other = ptm_driver;
 851         tty_set_operations(pts_driver, &pty_unix98_ops);
 852
 853         if (tty_register_driver(ptm_driver))
 854                 panic("Couldn't register Unix98 ptm driver");
 855         if (tty_register_driver(pts_driver))
 856                 panic("Couldn't register Unix98 pts driver");
 857
 858         /* Now create the /dev/ptmx special device */
 859         tty_default_fops(&ptmx_fops);
 860         ptmx_fops.open = ptmx_open;
 861
 862         cdev_init(&ptmx_cdev, &ptmx_fops);
 863         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 864             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 865                 panic("Couldn't register /dev/ptmx driver");
 866         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 867 }
 868
 869 #else
 870 static inline void unix98_pty_init(void) { }
 871 #endif
 872
 873 static int __init pty_init(void)
 874 {
 875         legacy_pty_init();
 876         unix98_pty_init();
 877         return 0;
 878 }
 879 device_initcall(pty_init);