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 (test_bit(TTY_IO_ERROR, &tty->flags))
  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) |
 263                                 (tty->termios.c_lflag & EXTPROC);
 264                 int old_flow = ((old_termios->c_iflag & IXON) &&
 265                                 (old_termios->c_cc[VSTOP] == '\023') &&
 266                                 (old_termios->c_cc[VSTART] == '\021'));
 267                 int new_flow = (I_IXON(tty) &&
 268                                 STOP_CHAR(tty) == '\023' &&
 269                                 START_CHAR(tty) == '\021');
 270                 if ((old_flow != new_flow) || extproc) {
 271                         spin_lock_irq(&tty->ctrl_lock);
 272                         if (old_flow != new_flow) {
 273                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 274                                 if (new_flow)
 275                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 276                                 else
 277                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 278                         }
 279                         if (extproc)
 280                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 281                         spin_unlock_irq(&tty->ctrl_lock);
 282                         wake_up_interruptible(&tty->link->read_wait);
 283                 }
 284         }
 285
 286         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 287         tty->termios.c_cflag |= (CS8 | CREAD);
 288 }
 289
 290 /**
 291  *      pty_do_resize           -       resize event
 292  *      @tty: tty being resized
 293  *      @ws: window size being set.
 294  *
 295  *      Update the termios variables and send the necessary signals to
 296  *      peform a terminal resize correctly
 297  */
 298
 299 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 300 {
 301         struct pid *pgrp, *rpgrp;
 302         struct tty_struct *pty = tty->link;
 303
 304         /* For a PTY we need to lock the tty side */
 305         mutex_lock(&tty->winsize_mutex);
 306         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 307                 goto done;
 308
 309         /* Signal the foreground process group of both ptys */
 310         pgrp = tty_get_pgrp(tty);
 311         rpgrp = tty_get_pgrp(pty);
 312
 313         if (pgrp)
 314                 kill_pgrp(pgrp, SIGWINCH, 1);
 315         if (rpgrp != pgrp && rpgrp)
 316                 kill_pgrp(rpgrp, SIGWINCH, 1);
 317
 318         put_pid(pgrp);
 319         put_pid(rpgrp);
 320
 321         tty->winsize = *ws;
 322         pty->winsize = *ws;     /* Never used so will go away soon */
 323 done:
 324         mutex_unlock(&tty->winsize_mutex);
 325         return 0;
 326 }
 327
 328 /**
 329  *      pty_start - start() handler
 330  *      pty_stop  - stop() handler
 331  *      @tty: tty being flow-controlled
 332  *
 333  *      Propagates the TIOCPKT status to the master pty.
 334  *
 335  *      NB: only the master pty can be in packet mode so only the slave
 336  *          needs start()/stop() handlers
 337  */
 338 static void pty_start(struct tty_struct *tty)
 339 {
 340         unsigned long flags;
 341
 342         if (tty->link && tty->link->packet) {
 343                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 344                 tty->ctrl_status &= ~TIOCPKT_STOP;
 345                 tty->ctrl_status |= TIOCPKT_START;
 346                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 347                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 348         }
 349 }
 350
 351 static void pty_stop(struct tty_struct *tty)
 352 {
 353         unsigned long flags;
 354
 355         if (tty->link && tty->link->packet) {
 356                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 357                 tty->ctrl_status &= ~TIOCPKT_START;
 358                 tty->ctrl_status |= TIOCPKT_STOP;
 359                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 360                 wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
 361         }
 362 }
 363
 364 /**
 365  *      pty_common_install              -       set up the pty pair
 366  *      @driver: the pty driver
 367  *      @tty: the tty being instantiated
 368  *      @legacy: true if this is BSD style
 369  *
 370  *      Perform the initial set up for the tty/pty pair. Called from the
 371  *      tty layer when the port is first opened.
 372  *
 373  *      Locking: the caller must hold the tty_mutex
 374  */
 375 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 376                 bool legacy)
 377 {
 378         struct tty_struct *o_tty;
 379         struct tty_port *ports[2];
 380         int idx = tty->index;
 381         int retval = -ENOMEM;
 382
 383         /* Opening the slave first has always returned -EIO */
 384         if (driver->subtype != PTY_TYPE_MASTER)
 385                 return -EIO;
 386
 387         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 388         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 389         if (!ports[0] || !ports[1])
 390                 goto err;
 391         if (!try_module_get(driver->other->owner)) {
 392                 /* This cannot in fact currently happen */
 393                 goto err;
 394         }
 395         o_tty = alloc_tty_struct(driver->other, idx);
 396         if (!o_tty)
 397                 goto err_put_module;
 398
 399         tty_set_lock_subclass(o_tty);
 400         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 401
 402         if (legacy) {
 403                 /* We always use new tty termios data so we can do this
 404                    the easy way .. */
 405                 retval = tty_init_termios(tty);
 406                 if (retval)
 407                         goto err_deinit_tty;
 408
 409                 retval = tty_init_termios(o_tty);
 410                 if (retval)
 411                         goto err_free_termios;
 412
 413                 driver->other->ttys[idx] = o_tty;
 414                 driver->ttys[idx] = tty;
 415         } else {
 416                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 417                 tty->termios = driver->init_termios;
 418                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 419                 o_tty->termios = driver->other->init_termios;
 420         }
 421
 422         /*
 423          * Everything allocated ... set up the o_tty structure.
 424          */
 425         tty_driver_kref_get(driver->other);
 426         /* Establish the links in both directions */
 427         tty->link   = o_tty;
 428         o_tty->link = tty;
 429         tty_port_init(ports[0]);
 430         tty_port_init(ports[1]);
 431         tty_buffer_set_limit(ports[0], 8192);
 432         tty_buffer_set_limit(ports[1], 8192);
 433         o_tty->port = ports[0];
 434         tty->port = ports[1];
 435         o_tty->port->itty = o_tty;
 436
 437         tty_buffer_set_lock_subclass(o_tty->port);
 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 /*
 500  * not really modular, but the easiest way to keep compat with existing
 501  * bootargs behaviour is to continue using module_param here.
 502  */
 503 module_param(legacy_count, int, 0);
 504
 505 /*
 506  * The master side of a pty can do TIOCSPTLCK and thus
 507  * has pty_bsd_ioctl.
 508  */
 509 static const struct tty_operations master_pty_ops_bsd = {
 510         .install = pty_install,
 511         .open = pty_open,
 512         .close = pty_close,
 513         .write = pty_write,
 514         .write_room = pty_write_room,
 515         .flush_buffer = pty_flush_buffer,
 516         .chars_in_buffer = pty_chars_in_buffer,
 517         .unthrottle = pty_unthrottle,
 518         .ioctl = pty_bsd_ioctl,
 519         .cleanup = pty_cleanup,
 520         .resize = pty_resize,
 521         .remove = pty_remove
 522 };
 523
 524 static const struct tty_operations slave_pty_ops_bsd = {
 525         .install = pty_install,
 526         .open = pty_open,
 527         .close = pty_close,
 528         .write = pty_write,
 529         .write_room = pty_write_room,
 530         .flush_buffer = pty_flush_buffer,
 531         .chars_in_buffer = pty_chars_in_buffer,
 532         .unthrottle = pty_unthrottle,
 533         .set_termios = pty_set_termios,
 534         .cleanup = pty_cleanup,
 535         .resize = pty_resize,
 536         .start = pty_start,
 537         .stop = pty_stop,
 538         .remove = pty_remove
 539 };
 540
 541 static void __init legacy_pty_init(void)
 542 {
 543         struct tty_driver *pty_driver, *pty_slave_driver;
 544
 545         if (legacy_count <= 0)
 546                 return;
 547
 548         pty_driver = tty_alloc_driver(legacy_count,
 549                         TTY_DRIVER_RESET_TERMIOS |
 550                         TTY_DRIVER_REAL_RAW |
 551                         TTY_DRIVER_DYNAMIC_ALLOC);
 552         if (IS_ERR(pty_driver))
 553                 panic("Couldn't allocate pty driver");
 554
 555         pty_slave_driver = tty_alloc_driver(legacy_count,
 556                         TTY_DRIVER_RESET_TERMIOS |
 557                         TTY_DRIVER_REAL_RAW |
 558                         TTY_DRIVER_DYNAMIC_ALLOC);
 559         if (IS_ERR(pty_slave_driver))
 560                 panic("Couldn't allocate pty slave driver");
 561
 562         pty_driver->driver_name = "pty_master";
 563         pty_driver->name = "pty";
 564         pty_driver->major = PTY_MASTER_MAJOR;
 565         pty_driver->minor_start = 0;
 566         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 567         pty_driver->subtype = PTY_TYPE_MASTER;
 568         pty_driver->init_termios = tty_std_termios;
 569         pty_driver->init_termios.c_iflag = 0;
 570         pty_driver->init_termios.c_oflag = 0;
 571         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 572         pty_driver->init_termios.c_lflag = 0;
 573         pty_driver->init_termios.c_ispeed = 38400;
 574         pty_driver->init_termios.c_ospeed = 38400;
 575         pty_driver->other = pty_slave_driver;
 576         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 577
 578         pty_slave_driver->driver_name = "pty_slave";
 579         pty_slave_driver->name = "ttyp";
 580         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 581         pty_slave_driver->minor_start = 0;
 582         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 583         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 584         pty_slave_driver->init_termios = tty_std_termios;
 585         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 586         pty_slave_driver->init_termios.c_ispeed = 38400;
 587         pty_slave_driver->init_termios.c_ospeed = 38400;
 588         pty_slave_driver->other = pty_driver;
 589         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 590
 591         if (tty_register_driver(pty_driver))
 592                 panic("Couldn't register pty driver");
 593         if (tty_register_driver(pty_slave_driver))
 594                 panic("Couldn't register pty slave driver");
 595 }
 596 #else
 597 static inline void legacy_pty_init(void) { }
 598 #endif
 599
 600 /* Unix98 devices */
 601 #ifdef CONFIG_UNIX98_PTYS
 602
 603 static struct cdev ptmx_cdev;
 604
 605 static int pty_unix98_ioctl(struct tty_struct *tty,
 606                             unsigned int cmd, unsigned long arg)
 607 {
 608         switch (cmd) {
 609         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 610                 return pty_set_lock(tty, (int __user *)arg);
 611         case TIOCGPTLCK: /* Get PT Lock status */
 612                 return pty_get_lock(tty, (int __user *)arg);
 613         case TIOCPKT: /* Set PT packet mode */
 614                 return pty_set_pktmode(tty, (int __user *)arg);
 615         case TIOCGPKT: /* Get PT packet mode */
 616                 return pty_get_pktmode(tty, (int __user *)arg);
 617         case TIOCGPTN: /* Get PT Number */
 618                 return put_user(tty->index, (unsigned int __user *)arg);
 619         case TIOCSIG:    /* Send signal to other side of pty */
 620                 return pty_signal(tty, (int) arg);
 621         }
 622
 623         return -ENOIOCTLCMD;
 624 }
 625
 626 /**
 627  *      ptm_unix98_lookup       -       find a pty master
 628  *      @driver: ptm driver
 629  *      @idx: tty index
 630  *
 631  *      Look up a pty master device. Called under the tty_mutex for now.
 632  *      This provides our locking.
 633  */
 634
 635 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 636                 struct inode *ptm_inode, int idx)
 637 {
 638         /* Master must be open via /dev/ptmx */
 639         return ERR_PTR(-EIO);
 640 }
 641
 642 /**
 643  *      pts_unix98_lookup       -       find a pty slave
 644  *      @driver: pts driver
 645  *      @idx: tty index
 646  *
 647  *      Look up a pty master device. Called under the tty_mutex for now.
 648  *      This provides our locking for the tty pointer.
 649  */
 650
 651 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 652                 struct inode *pts_inode, int idx)
 653 {
 654         struct tty_struct *tty;
 655
 656         mutex_lock(&devpts_mutex);
 657         tty = devpts_get_priv(pts_inode);
 658         mutex_unlock(&devpts_mutex);
 659         /* Master must be open before slave */
 660         if (!tty)
 661                 return ERR_PTR(-EIO);
 662         return tty;
 663 }
 664
 665 /* We have no need to install and remove our tty objects as devpts does all
 666    the work for us */
 667
 668 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 669 {
 670         return pty_common_install(driver, tty, false);
 671 }
 672
 673 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 674 {
 675 }
 676
 677 /* this is called once with whichever end is closed last */
 678 static void pty_unix98_shutdown(struct tty_struct *tty)
 679 {
 680         struct pts_fs_info *fsi;
 681
 682         if (tty->driver->subtype == PTY_TYPE_MASTER)
 683                 fsi = tty->driver_data;
 684         else
 685                 fsi = tty->link->driver_data;
 686         devpts_kill_index(fsi, tty->index);
 687         devpts_put_ref(fsi);
 688 }
 689
 690 static const struct tty_operations ptm_unix98_ops = {
 691         .lookup = ptm_unix98_lookup,
 692         .install = pty_unix98_install,
 693         .remove = pty_unix98_remove,
 694         .open = pty_open,
 695         .close = pty_close,
 696         .write = pty_write,
 697         .write_room = pty_write_room,
 698         .flush_buffer = pty_flush_buffer,
 699         .chars_in_buffer = pty_chars_in_buffer,
 700         .unthrottle = pty_unthrottle,
 701         .ioctl = pty_unix98_ioctl,
 702         .resize = pty_resize,
 703         .shutdown = pty_unix98_shutdown,
 704         .cleanup = pty_cleanup
 705 };
 706
 707 static const struct tty_operations pty_unix98_ops = {
 708         .lookup = pts_unix98_lookup,
 709         .install = pty_unix98_install,
 710         .remove = pty_unix98_remove,
 711         .open = pty_open,
 712         .close = pty_close,
 713         .write = pty_write,
 714         .write_room = pty_write_room,
 715         .flush_buffer = pty_flush_buffer,
 716         .chars_in_buffer = pty_chars_in_buffer,
 717         .unthrottle = pty_unthrottle,
 718         .set_termios = pty_set_termios,
 719         .start = pty_start,
 720         .stop = pty_stop,
 721         .shutdown = pty_unix98_shutdown,
 722         .cleanup = pty_cleanup,
 723 };
 724
 725 /**
 726  *      ptmx_open               -       open a unix 98 pty master
 727  *      @inode: inode of device file
 728  *      @filp: file pointer to tty
 729  *
 730  *      Allocate a unix98 pty master device from the ptmx driver.
 731  *
 732  *      Locking: tty_mutex protects the init_dev work. tty->count should
 733  *              protect the rest.
 734  *              allocated_ptys_lock handles the list of free pty numbers
 735  */
 736
 737 static int ptmx_open(struct inode *inode, struct file *filp)
 738 {
 739         struct pts_fs_info *fsi;
 740         struct tty_struct *tty;
 741         struct inode *slave_inode;
 742         int retval;
 743         int index;
 744
 745         nonseekable_open(inode, filp);
 746
 747         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 748         filp->f_mode |= FMODE_NONOTIFY;
 749
 750         retval = tty_alloc_file(filp);
 751         if (retval)
 752                 return retval;
 753
 754         fsi = devpts_get_ref(inode, filp);
 755         retval = -ENODEV;
 756         if (!fsi)
 757                 goto out_free_file;
 758
 759         /* find a device that is not in use. */
 760         mutex_lock(&devpts_mutex);
 761         index = devpts_new_index(fsi);
 762         mutex_unlock(&devpts_mutex);
 763
 764         retval = index;
 765         if (index < 0)
 766                 goto out_put_ref;
 767
 768
 769         mutex_lock(&tty_mutex);
 770         tty = tty_init_dev(ptm_driver, index);
 771         /* The tty returned here is locked so we can safely
 772            drop the mutex */
 773         mutex_unlock(&tty_mutex);
 774
 775         retval = PTR_ERR(tty);
 776         if (IS_ERR(tty))
 777                 goto out;
 778
 779         /*
 780          * From here on out, the tty is "live", and the index and
 781          * fsi will be killed/put by the tty_release()
 782          */
 783         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 784         tty->driver_data = fsi;
 785
 786         tty_add_file(tty, filp);
 787
 788         slave_inode = devpts_pty_new(fsi,
 789                         MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
 790                         tty->link);
 791         if (IS_ERR(slave_inode)) {
 792                 retval = PTR_ERR(slave_inode);
 793                 goto err_release;
 794         }
 795         tty->link->driver_data = slave_inode;
 796
 797         retval = ptm_driver->ops->open(tty, filp);
 798         if (retval)
 799                 goto err_release;
 800
 801         tty_debug_hangup(tty, "(tty count=%d)\n", tty->count);
 802
 803         tty_unlock(tty);
 804         return 0;
 805 err_release:
 806         tty_unlock(tty);
 807         // This will also put-ref the fsi
 808         tty_release(inode, filp);
 809         return retval;
 810 out:
 811         devpts_kill_index(fsi, index);
 812 out_put_ref:
 813         devpts_put_ref(fsi);
 814 out_free_file:
 815         tty_free_file(filp);
 816         return retval;
 817 }
 818
 819 static struct file_operations ptmx_fops;
 820
 821 static void __init unix98_pty_init(void)
 822 {
 823         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 824                         TTY_DRIVER_RESET_TERMIOS |
 825                         TTY_DRIVER_REAL_RAW |
 826                         TTY_DRIVER_DYNAMIC_DEV |
 827                         TTY_DRIVER_DEVPTS_MEM |
 828                         TTY_DRIVER_DYNAMIC_ALLOC);
 829         if (IS_ERR(ptm_driver))
 830                 panic("Couldn't allocate Unix98 ptm driver");
 831         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 832                         TTY_DRIVER_RESET_TERMIOS |
 833                         TTY_DRIVER_REAL_RAW |
 834                         TTY_DRIVER_DYNAMIC_DEV |
 835                         TTY_DRIVER_DEVPTS_MEM |
 836                         TTY_DRIVER_DYNAMIC_ALLOC);
 837         if (IS_ERR(pts_driver))
 838                 panic("Couldn't allocate Unix98 pts driver");
 839
 840         ptm_driver->driver_name = "pty_master";
 841         ptm_driver->name = "ptm";
 842         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 843         ptm_driver->minor_start = 0;
 844         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 845         ptm_driver->subtype = PTY_TYPE_MASTER;
 846         ptm_driver->init_termios = tty_std_termios;
 847         ptm_driver->init_termios.c_iflag = 0;
 848         ptm_driver->init_termios.c_oflag = 0;
 849         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 850         ptm_driver->init_termios.c_lflag = 0;
 851         ptm_driver->init_termios.c_ispeed = 38400;
 852         ptm_driver->init_termios.c_ospeed = 38400;
 853         ptm_driver->other = pts_driver;
 854         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 855
 856         pts_driver->driver_name = "pty_slave";
 857         pts_driver->name = "pts";
 858         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 859         pts_driver->minor_start = 0;
 860         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 861         pts_driver->subtype = PTY_TYPE_SLAVE;
 862         pts_driver->init_termios = tty_std_termios;
 863         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 864         pts_driver->init_termios.c_ispeed = 38400;
 865         pts_driver->init_termios.c_ospeed = 38400;
 866         pts_driver->other = ptm_driver;
 867         tty_set_operations(pts_driver, &pty_unix98_ops);
 868
 869         if (tty_register_driver(ptm_driver))
 870                 panic("Couldn't register Unix98 ptm driver");
 871         if (tty_register_driver(pts_driver))
 872                 panic("Couldn't register Unix98 pts driver");
 873
 874         /* Now create the /dev/ptmx special device */
 875         tty_default_fops(&ptmx_fops);
 876         ptmx_fops.open = ptmx_open;
 877
 878         cdev_init(&ptmx_cdev, &ptmx_fops);
 879         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 880             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 881                 panic("Couldn't register /dev/ptmx driver");
 882         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 883 }
 884
 885 #else
 886 static inline void unix98_pty_init(void) { }
 887 #endif
 888
 889 static int __init pty_init(void)
 890 {
 891         legacy_pty_init();
 892         unix98_pty_init();
 893         return 0;
 894 }
 895 device_initcall(pty_init);