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
  11 #include <linux/errno.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/tty.h>
  14 #include <linux/tty_flip.h>
  15 #include <linux/fcntl.h>
  16 #include <linux/sched.h>
  17 #include <linux/string.h>
  18 #include <linux/major.h>
  19 #include <linux/mm.h>
  20 #include <linux/init.h>
  21 #include <linux/device.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/bitops.h>
  24 #include <linux/devpts_fs.h>
  25 #include <linux/slab.h>
  26 #include <linux/mutex.h>
  27 #include <linux/poll.h>
  28
  29
  30 #ifdef CONFIG_UNIX98_PTYS
  31 static struct tty_driver *ptm_driver;
  32 static struct tty_driver *pts_driver;
  33 static DEFINE_MUTEX(devpts_mutex);
  34 #endif
  35
  36 static void pty_close(struct tty_struct *tty, struct file *filp)
  37 {
  38         BUG_ON(!tty);
  39         if (tty->driver->subtype == PTY_TYPE_MASTER)
  40                 WARN_ON(tty->count > 1);
  41         else {
  42                 if (test_bit(TTY_IO_ERROR, &tty->flags))
  43                         return;
  44                 if (tty->count > 2)
  45                         return;
  46         }
  47         set_bit(TTY_IO_ERROR, &tty->flags);
  48         wake_up_interruptible(&tty->read_wait);
  49         wake_up_interruptible(&tty->write_wait);
  50         spin_lock_irq(&tty->ctrl_lock);
  51         tty->packet = 0;
  52         spin_unlock_irq(&tty->ctrl_lock);
  53         /* Review - krefs on tty_link ?? */
  54         if (!tty->link)
  55                 return;
  56         tty_flush_to_ldisc(tty->link);
  57         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  58         wake_up_interruptible(&tty->link->read_wait);
  59         wake_up_interruptible(&tty->link->write_wait);
  60         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  61                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  62 #ifdef CONFIG_UNIX98_PTYS
  63                 if (tty->driver == ptm_driver) {
  64                         mutex_lock(&devpts_mutex);
  65                         if (tty->link->driver_data)
  66                                 devpts_pty_kill(tty->link->driver_data);
  67                         mutex_unlock(&devpts_mutex);
  68                 }
  69 #endif
  70                 tty_vhangup(tty->link);
  71         }
  72 }
  73
  74 /*
  75  * The unthrottle routine is called by the line discipline to signal
  76  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  77  * flag is always set, to force the line discipline to always call the
  78  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  79  * characters in the queue.  This is necessary since each time this
  80  * happens, we need to wake up any sleeping processes that could be
  81  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  82  * for the pty buffer to be drained.
  83  */
  84 static void pty_unthrottle(struct tty_struct *tty)
  85 {
  86         tty_wakeup(tty->link);
  87         set_bit(TTY_THROTTLED, &tty->flags);
  88 }
  89
  90 /**
  91  *      pty_space       -       report space left for writing
  92  *      @to: tty we are writing into
  93  *
  94  *      Limit the buffer space used by ptys to 8k.
  95  */
  96
  97 static int pty_space(struct tty_struct *to)
  98 {
  99         int n = tty_buffer_space_avail(to->port);
 100         return min(n, 8192);
 101 }
 102
 103 /**
 104  *      pty_write               -       write to a pty
 105  *      @tty: the tty we write from
 106  *      @buf: kernel buffer of data
 107  *      @count: bytes to write
 108  *
 109  *      Our "hardware" write method. Data is coming from the ldisc which
 110  *      may be in a non sleeping state. We simply throw this at the other
 111  *      end of the link as if we were an IRQ handler receiving stuff for
 112  *      the other side of the pty/tty pair.
 113  */
 114
 115 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 116 {
 117         struct tty_struct *to = tty->link;
 118
 119         if (tty->stopped)
 120                 return 0;
 121
 122         if (c > 0) {
 123                 /* Stuff the data into the input queue of the other end */
 124                 c = tty_insert_flip_string(to->port, buf, c);
 125                 /* And shovel */
 126                 if (c)
 127                         tty_flip_buffer_push(to->port);
 128         }
 129         return c;
 130 }
 131
 132 /**
 133  *      pty_write_room  -       write space
 134  *      @tty: tty we are writing from
 135  *
 136  *      Report how many bytes the ldisc can send into the queue for
 137  *      the other device.
 138  */
 139
 140 static int pty_write_room(struct tty_struct *tty)
 141 {
 142         if (tty->stopped)
 143                 return 0;
 144         return pty_space(tty->link);
 145 }
 146
 147 /**
 148  *      pty_chars_in_buffer     -       characters currently in our tx queue
 149  *      @tty: our tty
 150  *
 151  *      Report how much we have in the transmit queue. As everything is
 152  *      instantly at the other end this is easy to implement.
 153  */
 154
 155 static int pty_chars_in_buffer(struct tty_struct *tty)
 156 {
 157         return 0;
 158 }
 159
 160 /* Set the lock flag on a pty */
 161 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 162 {
 163         int val;
 164         if (get_user(val, arg))
 165                 return -EFAULT;
 166         if (val)
 167                 set_bit(TTY_PTY_LOCK, &tty->flags);
 168         else
 169                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 170         return 0;
 171 }
 172
 173 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 174 {
 175         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 176         return put_user(locked, arg);
 177 }
 178
 179 /* Set the packet mode on a pty */
 180 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 181 {
 182         int pktmode;
 183
 184         if (get_user(pktmode, arg))
 185                 return -EFAULT;
 186
 187         spin_lock_irq(&tty->ctrl_lock);
 188         if (pktmode) {
 189                 if (!tty->packet) {
 190                         tty->link->ctrl_status = 0;
 191                         smp_mb();
 192                         tty->packet = 1;
 193                 }
 194         } else
 195                 tty->packet = 0;
 196         spin_unlock_irq(&tty->ctrl_lock);
 197
 198         return 0;
 199 }
 200
 201 /* Get the packet mode of a pty */
 202 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 203 {
 204         int pktmode = tty->packet;
 205         return put_user(pktmode, arg);
 206 }
 207
 208 /* Send a signal to the slave */
 209 static int pty_signal(struct tty_struct *tty, int sig)
 210 {
 211         struct pid *pgrp;
 212
 213         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 214                 return -EINVAL;
 215
 216         if (tty->link) {
 217                 pgrp = tty_get_pgrp(tty->link);
 218                 if (pgrp)
 219                         kill_pgrp(pgrp, sig, 1);
 220                 put_pid(pgrp);
 221         }
 222         return 0;
 223 }
 224
 225 static void pty_flush_buffer(struct tty_struct *tty)
 226 {
 227         struct tty_struct *to = tty->link;
 228
 229         if (!to)
 230                 return;
 231         /* tty_buffer_flush(to); FIXME */
 232         if (to->packet) {
 233                 spin_lock_irq(&tty->ctrl_lock);
 234                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 235                 wake_up_interruptible(&to->read_wait);
 236                 spin_unlock_irq(&tty->ctrl_lock);
 237         }
 238 }
 239
 240 static int pty_open(struct tty_struct *tty, struct file *filp)
 241 {
 242         if (!tty || !tty->link)
 243                 return -ENODEV;
 244
 245         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 246                 goto out;
 247         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 248                 goto out;
 249         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 250                 goto out;
 251
 252         clear_bit(TTY_IO_ERROR, &tty->flags);
 253         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 254         set_bit(TTY_THROTTLED, &tty->flags);
 255         return 0;
 256
 257 out:
 258         set_bit(TTY_IO_ERROR, &tty->flags);
 259         return -EIO;
 260 }
 261
 262 static void pty_set_termios(struct tty_struct *tty,
 263                                         struct ktermios *old_termios)
 264 {
 265         /* See if packet mode change of state. */
 266         if (tty->link && tty->link->packet) {
 267                 int extproc = (old_termios->c_lflag & EXTPROC) |
 268                                 (tty->termios.c_lflag & EXTPROC);
 269                 int old_flow = ((old_termios->c_iflag & IXON) &&
 270                                 (old_termios->c_cc[VSTOP] == '\023') &&
 271                                 (old_termios->c_cc[VSTART] == '\021'));
 272                 int new_flow = (I_IXON(tty) &&
 273                                 STOP_CHAR(tty) == '\023' &&
 274                                 START_CHAR(tty) == '\021');
 275                 if ((old_flow != new_flow) || extproc) {
 276                         spin_lock_irq(&tty->ctrl_lock);
 277                         if (old_flow != new_flow) {
 278                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 279                                 if (new_flow)
 280                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 281                                 else
 282                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 283                         }
 284                         if (extproc)
 285                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 286                         spin_unlock_irq(&tty->ctrl_lock);
 287                         wake_up_interruptible(&tty->link->read_wait);
 288                 }
 289         }
 290
 291         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 292         tty->termios.c_cflag |= (CS8 | CREAD);
 293 }
 294
 295 /**
 296  *      pty_do_resize           -       resize event
 297  *      @tty: tty being resized
 298  *      @ws: window size being set.
 299  *
 300  *      Update the termios variables and send the necessary signals to
 301  *      peform a terminal resize correctly
 302  */
 303
 304 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 305 {
 306         struct pid *pgrp, *rpgrp;
 307         struct tty_struct *pty = tty->link;
 308
 309         /* For a PTY we need to lock the tty side */
 310         mutex_lock(&tty->winsize_mutex);
 311         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 312                 goto done;
 313
 314         /* Signal the foreground process group of both ptys */
 315         pgrp = tty_get_pgrp(tty);
 316         rpgrp = tty_get_pgrp(pty);
 317
 318         if (pgrp)
 319                 kill_pgrp(pgrp, SIGWINCH, 1);
 320         if (rpgrp != pgrp && rpgrp)
 321                 kill_pgrp(rpgrp, SIGWINCH, 1);
 322
 323         put_pid(pgrp);
 324         put_pid(rpgrp);
 325
 326         tty->winsize = *ws;
 327         pty->winsize = *ws;     /* Never used so will go away soon */
 328 done:
 329         mutex_unlock(&tty->winsize_mutex);
 330         return 0;
 331 }
 332
 333 /**
 334  *      pty_start - start() handler
 335  *      pty_stop  - stop() handler
 336  *      @tty: tty being flow-controlled
 337  *
 338  *      Propagates the TIOCPKT status to the master pty.
 339  *
 340  *      NB: only the master pty can be in packet mode so only the slave
 341  *          needs start()/stop() handlers
 342  */
 343 static void pty_start(struct tty_struct *tty)
 344 {
 345         unsigned long flags;
 346
 347         if (tty->link && tty->link->packet) {
 348                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 349                 tty->ctrl_status &= ~TIOCPKT_STOP;
 350                 tty->ctrl_status |= TIOCPKT_START;
 351                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 352                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 353         }
 354 }
 355
 356 static void pty_stop(struct tty_struct *tty)
 357 {
 358         unsigned long flags;
 359
 360         if (tty->link && tty->link->packet) {
 361                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 362                 tty->ctrl_status &= ~TIOCPKT_START;
 363                 tty->ctrl_status |= TIOCPKT_STOP;
 364                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 365                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 366         }
 367 }
 368
 369 /**
 370  *      pty_common_install              -       set up the pty pair
 371  *      @driver: the pty driver
 372  *      @tty: the tty being instantiated
 373  *      @legacy: true if this is BSD style
 374  *
 375  *      Perform the initial set up for the tty/pty pair. Called from the
 376  *      tty layer when the port is first opened.
 377  *
 378  *      Locking: the caller must hold the tty_mutex
 379  */
 380 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 381                 bool legacy)
 382 {
 383         struct tty_struct *o_tty;
 384         struct tty_port *ports[2];
 385         int idx = tty->index;
 386         int retval = -ENOMEM;
 387
 388         /* Opening the slave first has always returned -EIO */
 389         if (driver->subtype != PTY_TYPE_MASTER)
 390                 return -EIO;
 391
 392         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 393         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 394         if (!ports[0] || !ports[1])
 395                 goto err;
 396         if (!try_module_get(driver->other->owner)) {
 397                 /* This cannot in fact currently happen */
 398                 goto err;
 399         }
 400         o_tty = alloc_tty_struct(driver->other, idx);
 401         if (!o_tty)
 402                 goto err_put_module;
 403
 404         tty_set_lock_subclass(o_tty);
 405
 406         if (legacy) {
 407                 /* We always use new tty termios data so we can do this
 408                    the easy way .. */
 409                 retval = tty_init_termios(tty);
 410                 if (retval)
 411                         goto err_deinit_tty;
 412
 413                 retval = tty_init_termios(o_tty);
 414                 if (retval)
 415                         goto err_free_termios;
 416
 417                 driver->other->ttys[idx] = o_tty;
 418                 driver->ttys[idx] = tty;
 419         } else {
 420                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 421                 tty->termios = driver->init_termios;
 422                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 423                 o_tty->termios = driver->other->init_termios;
 424         }
 425
 426         /*
 427          * Everything allocated ... set up the o_tty structure.
 428          */
 429         tty_driver_kref_get(driver->other);
 430         /* Establish the links in both directions */
 431         tty->link   = o_tty;
 432         o_tty->link = tty;
 433         tty_port_init(ports[0]);
 434         tty_port_init(ports[1]);
 435         o_tty->port = ports[0];
 436         tty->port = ports[1];
 437         o_tty->port->itty = o_tty;
 438
 439         tty_driver_kref_get(driver);
 440         tty->count++;
 441         o_tty->count++;
 442         return 0;
 443 err_free_termios:
 444         if (legacy)
 445                 tty_free_termios(tty);
 446 err_deinit_tty:
 447         deinitialize_tty_struct(o_tty);
 448         free_tty_struct(o_tty);
 449 err_put_module:
 450         module_put(driver->other->owner);
 451 err:
 452         kfree(ports[0]);
 453         kfree(ports[1]);
 454         return retval;
 455 }
 456
 457 static void pty_cleanup(struct tty_struct *tty)
 458 {
 459         tty_port_put(tty->port);
 460 }
 461
 462 /* Traditional BSD devices */
 463 #ifdef CONFIG_LEGACY_PTYS
 464
 465 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 466 {
 467         return pty_common_install(driver, tty, true);
 468 }
 469
 470 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 471 {
 472         struct tty_struct *pair = tty->link;
 473         driver->ttys[tty->index] = NULL;
 474         if (pair)
 475                 pair->driver->ttys[pair->index] = NULL;
 476 }
 477
 478 static int pty_bsd_ioctl(struct tty_struct *tty,
 479                          unsigned int cmd, unsigned long arg)
 480 {
 481         switch (cmd) {
 482         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 483                 return pty_set_lock(tty, (int __user *) arg);
 484         case TIOCGPTLCK: /* Get PT Lock status */
 485                 return pty_get_lock(tty, (int __user *)arg);
 486         case TIOCPKT: /* Set PT packet mode */
 487                 return pty_set_pktmode(tty, (int __user *)arg);
 488         case TIOCGPKT: /* Get PT packet mode */
 489                 return pty_get_pktmode(tty, (int __user *)arg);
 490         case TIOCSIG:    /* Send signal to other side of pty */
 491                 return pty_signal(tty, (int) arg);
 492         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 493                 return -EINVAL;
 494         }
 495         return -ENOIOCTLCMD;
 496 }
 497
 498 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 499 module_param(legacy_count, int, 0);
 500
 501 /*
 502  * The master side of a pty can do TIOCSPTLCK and thus
 503  * has pty_bsd_ioctl.
 504  */
 505 static const struct tty_operations master_pty_ops_bsd = {
 506         .install = pty_install,
 507         .open = pty_open,
 508         .close = pty_close,
 509         .write = pty_write,
 510         .write_room = pty_write_room,
 511         .flush_buffer = pty_flush_buffer,
 512         .chars_in_buffer = pty_chars_in_buffer,
 513         .unthrottle = pty_unthrottle,
 514         .ioctl = pty_bsd_ioctl,
 515         .cleanup = pty_cleanup,
 516         .resize = pty_resize,
 517         .remove = pty_remove
 518 };
 519
 520 static const struct tty_operations slave_pty_ops_bsd = {
 521         .install = pty_install,
 522         .open = pty_open,
 523         .close = pty_close,
 524         .write = pty_write,
 525         .write_room = pty_write_room,
 526         .flush_buffer = pty_flush_buffer,
 527         .chars_in_buffer = pty_chars_in_buffer,
 528         .unthrottle = pty_unthrottle,
 529         .set_termios = pty_set_termios,
 530         .cleanup = pty_cleanup,
 531         .resize = pty_resize,
 532         .start = pty_start,
 533         .stop = pty_stop,
 534         .remove = pty_remove
 535 };
 536
 537 static void __init legacy_pty_init(void)
 538 {
 539         struct tty_driver *pty_driver, *pty_slave_driver;
 540
 541         if (legacy_count <= 0)
 542                 return;
 543
 544         pty_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_driver))
 549                 panic("Couldn't allocate pty driver");
 550
 551         pty_slave_driver = tty_alloc_driver(legacy_count,
 552                         TTY_DRIVER_RESET_TERMIOS |
 553                         TTY_DRIVER_REAL_RAW |
 554                         TTY_DRIVER_DYNAMIC_ALLOC);
 555         if (IS_ERR(pty_slave_driver))
 556                 panic("Couldn't allocate pty slave driver");
 557
 558         pty_driver->driver_name = "pty_master";
 559         pty_driver->name = "pty";
 560         pty_driver->major = PTY_MASTER_MAJOR;
 561         pty_driver->minor_start = 0;
 562         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 563         pty_driver->subtype = PTY_TYPE_MASTER;
 564         pty_driver->init_termios = tty_std_termios;
 565         pty_driver->init_termios.c_iflag = 0;
 566         pty_driver->init_termios.c_oflag = 0;
 567         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 568         pty_driver->init_termios.c_lflag = 0;
 569         pty_driver->init_termios.c_ispeed = 38400;
 570         pty_driver->init_termios.c_ospeed = 38400;
 571         pty_driver->other = pty_slave_driver;
 572         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 573
 574         pty_slave_driver->driver_name = "pty_slave";
 575         pty_slave_driver->name = "ttyp";
 576         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 577         pty_slave_driver->minor_start = 0;
 578         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 579         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 580         pty_slave_driver->init_termios = tty_std_termios;
 581         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 582         pty_slave_driver->init_termios.c_ispeed = 38400;
 583         pty_slave_driver->init_termios.c_ospeed = 38400;
 584         pty_slave_driver->other = pty_driver;
 585         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 586
 587         if (tty_register_driver(pty_driver))
 588                 panic("Couldn't register pty driver");
 589         if (tty_register_driver(pty_slave_driver))
 590                 panic("Couldn't register pty slave driver");
 591 }
 592 #else
 593 static inline void legacy_pty_init(void) { }
 594 #endif
 595
 596 /* Unix98 devices */
 597 #ifdef CONFIG_UNIX98_PTYS
 598
 599 static struct cdev ptmx_cdev;
 600
 601 static int pty_unix98_ioctl(struct tty_struct *tty,
 602                             unsigned int cmd, unsigned long arg)
 603 {
 604         switch (cmd) {
 605         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 606                 return pty_set_lock(tty, (int __user *)arg);
 607         case TIOCGPTLCK: /* Get PT Lock status */
 608                 return pty_get_lock(tty, (int __user *)arg);
 609         case TIOCPKT: /* Set PT packet mode */
 610                 return pty_set_pktmode(tty, (int __user *)arg);
 611         case TIOCGPKT: /* Get PT packet mode */
 612                 return pty_get_pktmode(tty, (int __user *)arg);
 613         case TIOCGPTN: /* Get PT Number */
 614                 return put_user(tty->index, (unsigned int __user *)arg);
 615         case TIOCSIG:    /* Send signal to other side of pty */
 616                 return pty_signal(tty, (int) arg);
 617         }
 618
 619         return -ENOIOCTLCMD;
 620 }
 621
 622 /**
 623  *      ptm_unix98_lookup       -       find a pty master
 624  *      @driver: ptm driver
 625  *      @idx: tty index
 626  *
 627  *      Look up a pty master device. Called under the tty_mutex for now.
 628  *      This provides our locking.
 629  */
 630
 631 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 632                 struct inode *ptm_inode, int idx)
 633 {
 634         /* Master must be open via /dev/ptmx */
 635         return ERR_PTR(-EIO);
 636 }
 637
 638 /**
 639  *      pts_unix98_lookup       -       find a pty slave
 640  *      @driver: pts driver
 641  *      @idx: tty index
 642  *
 643  *      Look up a pty master device. Called under the tty_mutex for now.
 644  *      This provides our locking for the tty pointer.
 645  */
 646
 647 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 648                 struct inode *pts_inode, int idx)
 649 {
 650         struct tty_struct *tty;
 651
 652         mutex_lock(&devpts_mutex);
 653         tty = devpts_get_priv(pts_inode);
 654         mutex_unlock(&devpts_mutex);
 655         /* Master must be open before slave */
 656         if (!tty)
 657                 return ERR_PTR(-EIO);
 658         return tty;
 659 }
 660
 661 /* We have no need to install and remove our tty objects as devpts does all
 662    the work for us */
 663
 664 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 665 {
 666         return pty_common_install(driver, tty, false);
 667 }
 668
 669 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 670 {
 671 }
 672
 673 /* this is called once with whichever end is closed last */
 674 static void pty_unix98_shutdown(struct tty_struct *tty)
 675 {
 676         devpts_kill_index(tty->driver_data, tty->index);
 677 }
 678
 679 static const struct tty_operations ptm_unix98_ops = {
 680         .lookup = ptm_unix98_lookup,
 681         .install = pty_unix98_install,
 682         .remove = pty_unix98_remove,
 683         .open = pty_open,
 684         .close = pty_close,
 685         .write = pty_write,
 686         .write_room = pty_write_room,
 687         .flush_buffer = pty_flush_buffer,
 688         .chars_in_buffer = pty_chars_in_buffer,
 689         .unthrottle = pty_unthrottle,
 690         .ioctl = pty_unix98_ioctl,
 691         .resize = pty_resize,
 692         .shutdown = pty_unix98_shutdown,
 693         .cleanup = pty_cleanup
 694 };
 695
 696 static const struct tty_operations pty_unix98_ops = {
 697         .lookup = pts_unix98_lookup,
 698         .install = pty_unix98_install,
 699         .remove = pty_unix98_remove,
 700         .open = pty_open,
 701         .close = pty_close,
 702         .write = pty_write,
 703         .write_room = pty_write_room,
 704         .flush_buffer = pty_flush_buffer,
 705         .chars_in_buffer = pty_chars_in_buffer,
 706         .unthrottle = pty_unthrottle,
 707         .set_termios = pty_set_termios,
 708         .start = pty_start,
 709         .stop = pty_stop,
 710         .shutdown = pty_unix98_shutdown,
 711         .cleanup = pty_cleanup,
 712 };
 713
 714 /**
 715  *      ptmx_open               -       open a unix 98 pty master
 716  *      @inode: inode of device file
 717  *      @filp: file pointer to tty
 718  *
 719  *      Allocate a unix98 pty master device from the ptmx driver.
 720  *
 721  *      Locking: tty_mutex protects the init_dev work. tty->count should
 722  *              protect the rest.
 723  *              allocated_ptys_lock handles the list of free pty numbers
 724  */
 725
 726 static int ptmx_open(struct inode *inode, struct file *filp)
 727 {
 728         struct tty_struct *tty;
 729         struct inode *slave_inode;
 730         int retval;
 731         int index;
 732
 733         nonseekable_open(inode, filp);
 734
 735         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 736         filp->f_mode |= FMODE_NONOTIFY;
 737
 738         retval = tty_alloc_file(filp);
 739         if (retval)
 740                 return retval;
 741
 742         /* find a device that is not in use. */
 743         mutex_lock(&devpts_mutex);
 744         index = devpts_new_index(inode);
 745         if (index < 0) {
 746                 retval = index;
 747                 mutex_unlock(&devpts_mutex);
 748                 goto err_file;
 749         }
 750
 751         mutex_unlock(&devpts_mutex);
 752
 753         mutex_lock(&tty_mutex);
 754         tty = tty_init_dev(ptm_driver, index);
 755
 756         if (IS_ERR(tty)) {
 757                 retval = PTR_ERR(tty);
 758                 goto out;
 759         }
 760
 761         /* The tty returned here is locked so we can safely
 762            drop the mutex */
 763         mutex_unlock(&tty_mutex);
 764
 765         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 766         tty->driver_data = inode;
 767
 768         tty_add_file(tty, filp);
 769
 770         slave_inode = devpts_pty_new(inode,
 771                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 772                         tty->link);
 773         if (IS_ERR(slave_inode)) {
 774                 retval = PTR_ERR(slave_inode);
 775                 goto err_release;
 776         }
 777         tty->link->driver_data = slave_inode;
 778
 779         retval = ptm_driver->ops->open(tty, filp);
 780         if (retval)
 781                 goto err_release;
 782
 783         tty_unlock(tty);
 784         return 0;
 785 err_release:
 786         tty_unlock(tty);
 787         tty_release(inode, filp);
 788         return retval;
 789 out:
 790         mutex_unlock(&tty_mutex);
 791         devpts_kill_index(inode, index);
 792 err_file:
 793         tty_free_file(filp);
 794         return retval;
 795 }
 796
 797 static struct file_operations ptmx_fops;
 798
 799 static void __init unix98_pty_init(void)
 800 {
 801         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 802                         TTY_DRIVER_RESET_TERMIOS |
 803                         TTY_DRIVER_REAL_RAW |
 804                         TTY_DRIVER_DYNAMIC_DEV |
 805                         TTY_DRIVER_DEVPTS_MEM |
 806                         TTY_DRIVER_DYNAMIC_ALLOC);
 807         if (IS_ERR(ptm_driver))
 808                 panic("Couldn't allocate Unix98 ptm driver");
 809         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 810                         TTY_DRIVER_RESET_TERMIOS |
 811                         TTY_DRIVER_REAL_RAW |
 812                         TTY_DRIVER_DYNAMIC_DEV |
 813                         TTY_DRIVER_DEVPTS_MEM |
 814                         TTY_DRIVER_DYNAMIC_ALLOC);
 815         if (IS_ERR(pts_driver))
 816                 panic("Couldn't allocate Unix98 pts driver");
 817
 818         ptm_driver->driver_name = "pty_master";
 819         ptm_driver->name = "ptm";
 820         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 821         ptm_driver->minor_start = 0;
 822         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 823         ptm_driver->subtype = PTY_TYPE_MASTER;
 824         ptm_driver->init_termios = tty_std_termios;
 825         ptm_driver->init_termios.c_iflag = 0;
 826         ptm_driver->init_termios.c_oflag = 0;
 827         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 828         ptm_driver->init_termios.c_lflag = 0;
 829         ptm_driver->init_termios.c_ispeed = 38400;
 830         ptm_driver->init_termios.c_ospeed = 38400;
 831         ptm_driver->other = pts_driver;
 832         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 833
 834         pts_driver->driver_name = "pty_slave";
 835         pts_driver->name = "pts";
 836         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 837         pts_driver->minor_start = 0;
 838         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 839         pts_driver->subtype = PTY_TYPE_SLAVE;
 840         pts_driver->init_termios = tty_std_termios;
 841         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 842         pts_driver->init_termios.c_ispeed = 38400;
 843         pts_driver->init_termios.c_ospeed = 38400;
 844         pts_driver->other = ptm_driver;
 845         tty_set_operations(pts_driver, &pty_unix98_ops);
 846
 847         if (tty_register_driver(ptm_driver))
 848                 panic("Couldn't register Unix98 ptm driver");
 849         if (tty_register_driver(pts_driver))
 850                 panic("Couldn't register Unix98 pts driver");
 851
 852         /* Now create the /dev/ptmx special device */
 853         tty_default_fops(&ptmx_fops);
 854         ptmx_fops.open = ptmx_open;
 855
 856         cdev_init(&ptmx_cdev, &ptmx_fops);
 857         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 858             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 859                 panic("Couldn't register /dev/ptmx driver");
 860         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 861 }
 862
 863 #else
 864 static inline void unix98_pty_init(void) { }
 865 #endif
 866
 867 static int __init pty_init(void)
 868 {
 869         legacy_pty_init();
 870         unix98_pty_init();
 871         return 0;
 872 }
 873 module_init(pty_init);