drivers/tty/pty.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *
   5  *  Added support for a Unix98-style ptmx device.
   6  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
   7  *
   8  */
   9
  10 #include <linux/module.h>
  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/signal.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 #include <linux/mount.h>
  29 #include <linux/file.h>
  30 #include <linux/ioctl.h>
  31 #include <linux/compat.h>
  32 #include "tty.h"
  33
  34 #undef TTY_DEBUG_HANGUP
  35 #ifdef TTY_DEBUG_HANGUP
  36 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
  37 #else
  38 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
  39 #endif
  40
  41 #ifdef CONFIG_UNIX98_PTYS
  42 static struct tty_driver *ptm_driver;
  43 static struct tty_driver *pts_driver;
  44 static DEFINE_MUTEX(devpts_mutex);
  45 #endif
  46
  47 static void pty_close(struct tty_struct *tty, struct file *filp)
  48 {
  49         if (tty->driver->subtype == PTY_TYPE_MASTER)
  50                 WARN_ON(tty->count > 1);
  51         else {
  52                 if (tty_io_error(tty))
  53                         return;
  54                 if (tty->count > 2)
  55                         return;
  56         }
  57         set_bit(TTY_IO_ERROR, &tty->flags);
  58         wake_up_interruptible(&tty->read_wait);
  59         wake_up_interruptible(&tty->write_wait);
  60         spin_lock_irq(&tty->ctrl.lock);
  61         tty->ctrl.packet = false;
  62         spin_unlock_irq(&tty->ctrl.lock);
  63         /* Review - krefs on tty_link ?? */
  64         if (!tty->link)
  65                 return;
  66         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  67         wake_up_interruptible(&tty->link->read_wait);
  68         wake_up_interruptible(&tty->link->write_wait);
  69         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  70                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
  71 #ifdef CONFIG_UNIX98_PTYS
  72                 if (tty->driver == ptm_driver) {
  73                         mutex_lock(&devpts_mutex);
  74                         if (tty->link->driver_data)
  75                                 devpts_pty_kill(tty->link->driver_data);
  76                         mutex_unlock(&devpts_mutex);
  77                 }
  78 #endif
  79                 tty_vhangup(tty->link);
  80         }
  81 }
  82
  83 /*
  84  * The unthrottle routine is called by the line discipline to signal
  85  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  86  * flag is always set, to force the line discipline to always call the
  87  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  88  * characters in the queue.  This is necessary since each time this
  89  * happens, we need to wake up any sleeping processes that could be
  90  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
  91  * for the pty buffer to be drained.
  92  */
  93 static void pty_unthrottle(struct tty_struct *tty)
  94 {
  95         tty_wakeup(tty->link);
  96         set_bit(TTY_THROTTLED, &tty->flags);
  97 }
  98
  99 /**
 100  *      pty_write               -       write to a pty
 101  *      @tty: the tty we write from
 102  *      @buf: kernel buffer of data
 103  *      @c: bytes to write
 104  *
 105  *      Our "hardware" write method. Data is coming from the ldisc which
 106  *      may be in a non sleeping state. We simply throw this at the other
 107  *      end of the link as if we were an IRQ handler receiving stuff for
 108  *      the other side of the pty/tty pair.
 109  */
 110
 111 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 112 {
 113         struct tty_struct *to = tty->link;
 114         unsigned long flags;
 115
 116         if (tty->flow.stopped)
 117                 return 0;
 118
 119         if (c > 0) {
 120                 spin_lock_irqsave(&to->port->lock, flags);
 121                 /* Stuff the data into the input queue of the other end */
 122                 c = tty_insert_flip_string(to->port, buf, c);
 123                 spin_unlock_irqrestore(&to->port->lock, flags);
 124                 /* And shovel */
 125                 if (c)
 126                         tty_flip_buffer_push(to->port);
 127         }
 128         return c;
 129 }
 130
 131 /**
 132  *      pty_write_room  -       write space
 133  *      @tty: tty we are writing from
 134  *
 135  *      Report how many bytes the ldisc can send into the queue for
 136  *      the other device.
 137  */
 138
 139 static unsigned int pty_write_room(struct tty_struct *tty)
 140 {
 141         if (tty->flow.stopped)
 142                 return 0;
 143         return tty_buffer_space_avail(tty->link->port);
 144 }
 145
 146 /**
 147  *      pty_chars_in_buffer     -       characters currently in our tx queue
 148  *      @tty: our tty
 149  *
 150  *      Report how much we have in the transmit queue. As everything is
 151  *      instantly at the other end this is easy to implement.
 152  */
 153
 154 static int pty_chars_in_buffer(struct tty_struct *tty)
 155 {
 156         return 0;
 157 }
 158
 159 /* Set the lock flag on a pty */
 160 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 161 {
 162         int val;
 163
 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
 177         return put_user(locked, arg);
 178 }
 179
 180 /* Set the packet mode on a pty */
 181 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 182 {
 183         int pktmode;
 184
 185         if (get_user(pktmode, arg))
 186                 return -EFAULT;
 187
 188         spin_lock_irq(&tty->ctrl.lock);
 189         if (pktmode) {
 190                 if (!tty->ctrl.packet) {
 191                         tty->link->ctrl.pktstatus = 0;
 192                         smp_mb();
 193                         tty->ctrl.packet = true;
 194                 }
 195         } else
 196                 tty->ctrl.packet = false;
 197         spin_unlock_irq(&tty->ctrl.lock);
 198
 199         return 0;
 200 }
 201
 202 /* Get the packet mode of a pty */
 203 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 204 {
 205         int pktmode = tty->ctrl.packet;
 206
 207         return put_user(pktmode, arg);
 208 }
 209
 210 /* Send a signal to the slave */
 211 static int pty_signal(struct tty_struct *tty, int sig)
 212 {
 213         struct pid *pgrp;
 214
 215         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 216                 return -EINVAL;
 217
 218         if (tty->link) {
 219                 pgrp = tty_get_pgrp(tty->link);
 220                 if (pgrp)
 221                         kill_pgrp(pgrp, sig, 1);
 222                 put_pid(pgrp);
 223         }
 224         return 0;
 225 }
 226
 227 static void pty_flush_buffer(struct tty_struct *tty)
 228 {
 229         struct tty_struct *to = tty->link;
 230
 231         if (!to)
 232                 return;
 233
 234         tty_buffer_flush(to, NULL);
 235         if (to->ctrl.packet) {
 236                 spin_lock_irq(&tty->ctrl.lock);
 237                 tty->ctrl.pktstatus |= TIOCPKT_FLUSHWRITE;
 238                 wake_up_interruptible(&to->read_wait);
 239                 spin_unlock_irq(&tty->ctrl.lock);
 240         }
 241 }
 242
 243 static int pty_open(struct tty_struct *tty, struct file *filp)
 244 {
 245         if (!tty || !tty->link)
 246                 return -ENODEV;
 247
 248         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 249                 goto out;
 250         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 251                 goto out;
 252         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 253                 goto out;
 254
 255         clear_bit(TTY_IO_ERROR, &tty->flags);
 256         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 257         set_bit(TTY_THROTTLED, &tty->flags);
 258         return 0;
 259
 260 out:
 261         set_bit(TTY_IO_ERROR, &tty->flags);
 262         return -EIO;
 263 }
 264
 265 static void pty_set_termios(struct tty_struct *tty,
 266                                         struct ktermios *old_termios)
 267 {
 268         /* See if packet mode change of state. */
 269         if (tty->link && tty->link->ctrl.packet) {
 270                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
 271                 int old_flow = ((old_termios->c_iflag & IXON) &&
 272                                 (old_termios->c_cc[VSTOP] == '\023') &&
 273                                 (old_termios->c_cc[VSTART] == '\021'));
 274                 int new_flow = (I_IXON(tty) &&
 275                                 STOP_CHAR(tty) == '\023' &&
 276                                 START_CHAR(tty) == '\021');
 277                 if ((old_flow != new_flow) || extproc) {
 278                         spin_lock_irq(&tty->ctrl.lock);
 279                         if (old_flow != new_flow) {
 280                                 tty->ctrl.pktstatus &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 281                                 if (new_flow)
 282                                         tty->ctrl.pktstatus |= TIOCPKT_DOSTOP;
 283                                 else
 284                                         tty->ctrl.pktstatus |= TIOCPKT_NOSTOP;
 285                         }
 286                         if (extproc)
 287                                 tty->ctrl.pktstatus |= TIOCPKT_IOCTL;
 288                         spin_unlock_irq(&tty->ctrl.lock);
 289                         wake_up_interruptible(&tty->link->read_wait);
 290                 }
 291         }
 292
 293         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 294         tty->termios.c_cflag |= (CS8 | CREAD);
 295 }
 296
 297 /**
 298  *      pty_do_resize           -       resize event
 299  *      @tty: tty being resized
 300  *      @ws: window size being set.
 301  *
 302  *      Update the termios variables and send the necessary signals to
 303  *      peform a terminal resize correctly
 304  */
 305
 306 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 307 {
 308         struct pid *pgrp, *rpgrp;
 309         struct tty_struct *pty = tty->link;
 310
 311         /* For a PTY we need to lock the tty side */
 312         mutex_lock(&tty->winsize_mutex);
 313         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 314                 goto done;
 315
 316         /* Signal the foreground process group of both ptys */
 317         pgrp = tty_get_pgrp(tty);
 318         rpgrp = tty_get_pgrp(pty);
 319
 320         if (pgrp)
 321                 kill_pgrp(pgrp, SIGWINCH, 1);
 322         if (rpgrp != pgrp && rpgrp)
 323                 kill_pgrp(rpgrp, SIGWINCH, 1);
 324
 325         put_pid(pgrp);
 326         put_pid(rpgrp);
 327
 328         tty->winsize = *ws;
 329         pty->winsize = *ws;     /* Never used so will go away soon */
 330 done:
 331         mutex_unlock(&tty->winsize_mutex);
 332         return 0;
 333 }
 334
 335 /**
 336  *      pty_start - start() handler
 337  *      pty_stop  - stop() handler
 338  *      @tty: tty being flow-controlled
 339  *
 340  *      Propagates the TIOCPKT status to the master pty.
 341  *
 342  *      NB: only the master pty can be in packet mode so only the slave
 343  *          needs start()/stop() handlers
 344  */
 345 static void pty_start(struct tty_struct *tty)
 346 {
 347         unsigned long flags;
 348
 349         if (tty->link && tty->link->ctrl.packet) {
 350                 spin_lock_irqsave(&tty->ctrl.lock, flags);
 351                 tty->ctrl.pktstatus &= ~TIOCPKT_STOP;
 352                 tty->ctrl.pktstatus |= TIOCPKT_START;
 353                 spin_unlock_irqrestore(&tty->ctrl.lock, flags);
 354                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 355         }
 356 }
 357
 358 static void pty_stop(struct tty_struct *tty)
 359 {
 360         unsigned long flags;
 361
 362         if (tty->link && tty->link->ctrl.packet) {
 363                 spin_lock_irqsave(&tty->ctrl.lock, flags);
 364                 tty->ctrl.pktstatus &= ~TIOCPKT_START;
 365                 tty->ctrl.pktstatus |= TIOCPKT_STOP;
 366                 spin_unlock_irqrestore(&tty->ctrl.lock, flags);
 367                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 368         }
 369 }
 370
 371 /**
 372  *      pty_common_install              -       set up the pty pair
 373  *      @driver: the pty driver
 374  *      @tty: the tty being instantiated
 375  *      @legacy: true if this is BSD style
 376  *
 377  *      Perform the initial set up for the tty/pty pair. Called from the
 378  *      tty layer when the port is first opened.
 379  *
 380  *      Locking: the caller must hold the tty_mutex
 381  */
 382 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 383                 bool legacy)
 384 {
 385         struct tty_struct *o_tty;
 386         struct tty_port *ports[2];
 387         int idx = tty->index;
 388         int retval = -ENOMEM;
 389
 390         /* Opening the slave first has always returned -EIO */
 391         if (driver->subtype != PTY_TYPE_MASTER)
 392                 return -EIO;
 393
 394         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 395         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 396         if (!ports[0] || !ports[1])
 397                 goto err;
 398         if (!try_module_get(driver->other->owner)) {
 399                 /* This cannot in fact currently happen */
 400                 goto err;
 401         }
 402         o_tty = alloc_tty_struct(driver->other, idx);
 403         if (!o_tty)
 404                 goto err_put_module;
 405
 406         tty_set_lock_subclass(o_tty);
 407         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 408
 409         if (legacy) {
 410                 /* We always use new tty termios data so we can do this
 411                    the easy way .. */
 412                 tty_init_termios(tty);
 413                 tty_init_termios(o_tty);
 414
 415                 driver->other->ttys[idx] = o_tty;
 416                 driver->ttys[idx] = tty;
 417         } else {
 418                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 419                 tty->termios = driver->init_termios;
 420                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 421                 o_tty->termios = driver->other->init_termios;
 422         }
 423
 424         /*
 425          * Everything allocated ... set up the o_tty structure.
 426          */
 427         tty_driver_kref_get(driver->other);
 428         /* Establish the links in both directions */
 429         tty->link   = o_tty;
 430         o_tty->link = tty;
 431         tty_port_init(ports[0]);
 432         tty_port_init(ports[1]);
 433         tty_buffer_set_limit(ports[0], 8192);
 434         tty_buffer_set_limit(ports[1], 8192);
 435         o_tty->port = ports[0];
 436         tty->port = ports[1];
 437         o_tty->port->itty = o_tty;
 438
 439         tty_buffer_set_lock_subclass(o_tty->port);
 440
 441         tty_driver_kref_get(driver);
 442         tty->count++;
 443         o_tty->count++;
 444         return 0;
 445
 446 err_put_module:
 447         module_put(driver->other->owner);
 448 err:
 449         kfree(ports[0]);
 450         kfree(ports[1]);
 451         return retval;
 452 }
 453
 454 static void pty_cleanup(struct tty_struct *tty)
 455 {
 456         tty_port_put(tty->port);
 457 }
 458
 459 /* Traditional BSD devices */
 460 #ifdef CONFIG_LEGACY_PTYS
 461
 462 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 463 {
 464         return pty_common_install(driver, tty, true);
 465 }
 466
 467 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 468 {
 469         struct tty_struct *pair = tty->link;
 470
 471         driver->ttys[tty->index] = NULL;
 472         if (pair)
 473                 pair->driver->ttys[pair->index] = NULL;
 474 }
 475
 476 static int pty_bsd_ioctl(struct tty_struct *tty,
 477                          unsigned int cmd, unsigned long arg)
 478 {
 479         switch (cmd) {
 480         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 481                 return pty_set_lock(tty, (int __user *) arg);
 482         case TIOCGPTLCK: /* Get PT Lock status */
 483                 return pty_get_lock(tty, (int __user *)arg);
 484         case TIOCPKT: /* Set PT packet mode */
 485                 return pty_set_pktmode(tty, (int __user *)arg);
 486         case TIOCGPKT: /* Get PT packet mode */
 487                 return pty_get_pktmode(tty, (int __user *)arg);
 488         case TIOCSIG:    /* Send signal to other side of pty */
 489                 return pty_signal(tty, (int) arg);
 490         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 491                 return -EINVAL;
 492         }
 493         return -ENOIOCTLCMD;
 494 }
 495
 496 #ifdef CONFIG_COMPAT
 497 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
 498                                  unsigned int cmd, unsigned long arg)
 499 {
 500         /*
 501          * PTY ioctls don't require any special translation between 32-bit and
 502          * 64-bit userspace, they are already compatible.
 503          */
 504         return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
 505 }
 506 #else
 507 #define pty_bsd_compat_ioctl NULL
 508 #endif
 509
 510 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 511 /*
 512  * not really modular, but the easiest way to keep compat with existing
 513  * bootargs behaviour is to continue using module_param here.
 514  */
 515 module_param(legacy_count, int, 0);
 516
 517 /*
 518  * The master side of a pty can do TIOCSPTLCK and thus
 519  * has pty_bsd_ioctl.
 520  */
 521 static const struct tty_operations master_pty_ops_bsd = {
 522         .install = pty_install,
 523         .open = pty_open,
 524         .close = pty_close,
 525         .write = pty_write,
 526         .write_room = pty_write_room,
 527         .flush_buffer = pty_flush_buffer,
 528         .chars_in_buffer = pty_chars_in_buffer,
 529         .unthrottle = pty_unthrottle,
 530         .ioctl = pty_bsd_ioctl,
 531         .compat_ioctl = pty_bsd_compat_ioctl,
 532         .cleanup = pty_cleanup,
 533         .resize = pty_resize,
 534         .remove = pty_remove
 535 };
 536
 537 static const struct tty_operations slave_pty_ops_bsd = {
 538         .install = pty_install,
 539         .open = pty_open,
 540         .close = pty_close,
 541         .write = pty_write,
 542         .write_room = pty_write_room,
 543         .flush_buffer = pty_flush_buffer,
 544         .chars_in_buffer = pty_chars_in_buffer,
 545         .unthrottle = pty_unthrottle,
 546         .set_termios = pty_set_termios,
 547         .cleanup = pty_cleanup,
 548         .resize = pty_resize,
 549         .start = pty_start,
 550         .stop = pty_stop,
 551         .remove = pty_remove
 552 };
 553
 554 static void __init legacy_pty_init(void)
 555 {
 556         struct tty_driver *pty_driver, *pty_slave_driver;
 557
 558         if (legacy_count <= 0)
 559                 return;
 560
 561         pty_driver = tty_alloc_driver(legacy_count,
 562                         TTY_DRIVER_RESET_TERMIOS |
 563                         TTY_DRIVER_REAL_RAW |
 564                         TTY_DRIVER_DYNAMIC_ALLOC);
 565         if (IS_ERR(pty_driver))
 566                 panic("Couldn't allocate pty driver");
 567
 568         pty_slave_driver = tty_alloc_driver(legacy_count,
 569                         TTY_DRIVER_RESET_TERMIOS |
 570                         TTY_DRIVER_REAL_RAW |
 571                         TTY_DRIVER_DYNAMIC_ALLOC);
 572         if (IS_ERR(pty_slave_driver))
 573                 panic("Couldn't allocate pty slave driver");
 574
 575         pty_driver->driver_name = "pty_master";
 576         pty_driver->name = "pty";
 577         pty_driver->major = PTY_MASTER_MAJOR;
 578         pty_driver->minor_start = 0;
 579         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 580         pty_driver->subtype = PTY_TYPE_MASTER;
 581         pty_driver->init_termios = tty_std_termios;
 582         pty_driver->init_termios.c_iflag = 0;
 583         pty_driver->init_termios.c_oflag = 0;
 584         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 585         pty_driver->init_termios.c_lflag = 0;
 586         pty_driver->init_termios.c_ispeed = 38400;
 587         pty_driver->init_termios.c_ospeed = 38400;
 588         pty_driver->other = pty_slave_driver;
 589         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 590
 591         pty_slave_driver->driver_name = "pty_slave";
 592         pty_slave_driver->name = "ttyp";
 593         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 594         pty_slave_driver->minor_start = 0;
 595         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 596         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 597         pty_slave_driver->init_termios = tty_std_termios;
 598         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 599         pty_slave_driver->init_termios.c_ispeed = 38400;
 600         pty_slave_driver->init_termios.c_ospeed = 38400;
 601         pty_slave_driver->other = pty_driver;
 602         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 603
 604         if (tty_register_driver(pty_driver))
 605                 panic("Couldn't register pty driver");
 606         if (tty_register_driver(pty_slave_driver))
 607                 panic("Couldn't register pty slave driver");
 608 }
 609 #else
 610 static inline void legacy_pty_init(void) { }
 611 #endif
 612
 613 /* Unix98 devices */
 614 #ifdef CONFIG_UNIX98_PTYS
 615 static struct cdev ptmx_cdev;
 616
 617 /**
 618  *      ptm_open_peer - open the peer of a pty
 619  *      @master: the open struct file of the ptmx device node
 620  *      @tty: the master of the pty being opened
 621  *      @flags: the flags for open
 622  *
 623  *      Provide a race free way for userspace to open the slave end of a pty
 624  *      (where they have the master fd and cannot access or trust the mount
 625  *      namespace /dev/pts was mounted inside).
 626  */
 627 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
 628 {
 629         int fd = -1;
 630         struct file *filp;
 631         int retval = -EINVAL;
 632         struct path path;
 633
 634         if (tty->driver != ptm_driver)
 635                 return -EIO;
 636
 637         fd = get_unused_fd_flags(flags);
 638         if (fd < 0) {
 639                 retval = fd;
 640                 goto err;
 641         }
 642
 643         /* Compute the slave's path */
 644         path.mnt = devpts_mntget(master, tty->driver_data);
 645         if (IS_ERR(path.mnt)) {
 646                 retval = PTR_ERR(path.mnt);
 647                 goto err_put;
 648         }
 649         path.dentry = tty->link->driver_data;
 650
 651         filp = dentry_open(&path, flags, current_cred());
 652         mntput(path.mnt);
 653         if (IS_ERR(filp)) {
 654                 retval = PTR_ERR(filp);
 655                 goto err_put;
 656         }
 657
 658         fd_install(fd, filp);
 659         return fd;
 660
 661 err_put:
 662         put_unused_fd(fd);
 663 err:
 664         return retval;
 665 }
 666
 667 static int pty_unix98_ioctl(struct tty_struct *tty,
 668                             unsigned int cmd, unsigned long arg)
 669 {
 670         switch (cmd) {
 671         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 672                 return pty_set_lock(tty, (int __user *)arg);
 673         case TIOCGPTLCK: /* Get PT Lock status */
 674                 return pty_get_lock(tty, (int __user *)arg);
 675         case TIOCPKT: /* Set PT packet mode */
 676                 return pty_set_pktmode(tty, (int __user *)arg);
 677         case TIOCGPKT: /* Get PT packet mode */
 678                 return pty_get_pktmode(tty, (int __user *)arg);
 679         case TIOCGPTN: /* Get PT Number */
 680                 return put_user(tty->index, (unsigned int __user *)arg);
 681         case TIOCSIG:    /* Send signal to other side of pty */
 682                 return pty_signal(tty, (int) arg);
 683         }
 684
 685         return -ENOIOCTLCMD;
 686 }
 687
 688 #ifdef CONFIG_COMPAT
 689 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
 690                                  unsigned int cmd, unsigned long arg)
 691 {
 692         /*
 693          * PTY ioctls don't require any special translation between 32-bit and
 694          * 64-bit userspace, they are already compatible.
 695          */
 696         return pty_unix98_ioctl(tty, cmd,
 697                 cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg));
 698 }
 699 #else
 700 #define pty_unix98_compat_ioctl NULL
 701 #endif
 702
 703 /**
 704  *      ptm_unix98_lookup       -       find a pty master
 705  *      @driver: ptm driver
 706  *      @file: unused
 707  *      @idx: tty index
 708  *
 709  *      Look up a pty master device. Called under the tty_mutex for now.
 710  *      This provides our locking.
 711  */
 712
 713 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 714                 struct file *file, int idx)
 715 {
 716         /* Master must be open via /dev/ptmx */
 717         return ERR_PTR(-EIO);
 718 }
 719
 720 /**
 721  *      pts_unix98_lookup       -       find a pty slave
 722  *      @driver: pts driver
 723  *      @file: file pointer to tty
 724  *      @idx: tty index
 725  *
 726  *      Look up a pty master device. Called under the tty_mutex for now.
 727  *      This provides our locking for the tty pointer.
 728  */
 729
 730 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 731                 struct file *file, int idx)
 732 {
 733         struct tty_struct *tty;
 734
 735         mutex_lock(&devpts_mutex);
 736         tty = devpts_get_priv(file->f_path.dentry);
 737         mutex_unlock(&devpts_mutex);
 738         /* Master must be open before slave */
 739         if (!tty)
 740                 return ERR_PTR(-EIO);
 741         return tty;
 742 }
 743
 744 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 745 {
 746         return pty_common_install(driver, tty, false);
 747 }
 748
 749 /* this is called once with whichever end is closed last */
 750 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 751 {
 752         struct pts_fs_info *fsi;
 753
 754         if (tty->driver->subtype == PTY_TYPE_MASTER)
 755                 fsi = tty->driver_data;
 756         else
 757                 fsi = tty->link->driver_data;
 758
 759         if (fsi) {
 760                 devpts_kill_index(fsi, tty->index);
 761                 devpts_release(fsi);
 762         }
 763 }
 764
 765 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
 766 {
 767         seq_printf(m, "tty-index:\t%d\n", tty->index);
 768 }
 769
 770 static const struct tty_operations ptm_unix98_ops = {
 771         .lookup = ptm_unix98_lookup,
 772         .install = pty_unix98_install,
 773         .remove = pty_unix98_remove,
 774         .open = pty_open,
 775         .close = pty_close,
 776         .write = pty_write,
 777         .write_room = pty_write_room,
 778         .flush_buffer = pty_flush_buffer,
 779         .chars_in_buffer = pty_chars_in_buffer,
 780         .unthrottle = pty_unthrottle,
 781         .ioctl = pty_unix98_ioctl,
 782         .compat_ioctl = pty_unix98_compat_ioctl,
 783         .resize = pty_resize,
 784         .cleanup = pty_cleanup,
 785         .show_fdinfo = pty_show_fdinfo,
 786 };
 787
 788 static const struct tty_operations pty_unix98_ops = {
 789         .lookup = pts_unix98_lookup,
 790         .install = pty_unix98_install,
 791         .remove = pty_unix98_remove,
 792         .open = pty_open,
 793         .close = pty_close,
 794         .write = pty_write,
 795         .write_room = pty_write_room,
 796         .flush_buffer = pty_flush_buffer,
 797         .chars_in_buffer = pty_chars_in_buffer,
 798         .unthrottle = pty_unthrottle,
 799         .set_termios = pty_set_termios,
 800         .start = pty_start,
 801         .stop = pty_stop,
 802         .cleanup = pty_cleanup,
 803 };
 804
 805 /**
 806  *      ptmx_open               -       open a unix 98 pty master
 807  *      @inode: inode of device file
 808  *      @filp: file pointer to tty
 809  *
 810  *      Allocate a unix98 pty master device from the ptmx driver.
 811  *
 812  *      Locking: tty_mutex protects the init_dev work. tty->count should
 813  *              protect the rest.
 814  *              allocated_ptys_lock handles the list of free pty numbers
 815  */
 816
 817 static int ptmx_open(struct inode *inode, struct file *filp)
 818 {
 819         struct pts_fs_info *fsi;
 820         struct tty_struct *tty;
 821         struct dentry *dentry;
 822         int retval;
 823         int index;
 824
 825         nonseekable_open(inode, filp);
 826
 827         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 828         filp->f_mode |= FMODE_NONOTIFY;
 829
 830         retval = tty_alloc_file(filp);
 831         if (retval)
 832                 return retval;
 833
 834         fsi = devpts_acquire(filp);
 835         if (IS_ERR(fsi)) {
 836                 retval = PTR_ERR(fsi);
 837                 goto out_free_file;
 838         }
 839
 840         /* find a device that is not in use. */
 841         mutex_lock(&devpts_mutex);
 842         index = devpts_new_index(fsi);
 843         mutex_unlock(&devpts_mutex);
 844
 845         retval = index;
 846         if (index < 0)
 847                 goto out_put_fsi;
 848
 849
 850         mutex_lock(&tty_mutex);
 851         tty = tty_init_dev(ptm_driver, index);
 852         /* The tty returned here is locked so we can safely
 853            drop the mutex */
 854         mutex_unlock(&tty_mutex);
 855
 856         retval = PTR_ERR(tty);
 857         if (IS_ERR(tty))
 858                 goto out;
 859
 860         /*
 861          * From here on out, the tty is "live", and the index and
 862          * fsi will be killed/put by the tty_release()
 863          */
 864         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 865         tty->driver_data = fsi;
 866
 867         tty_add_file(tty, filp);
 868
 869         dentry = devpts_pty_new(fsi, index, tty->link);
 870         if (IS_ERR(dentry)) {
 871                 retval = PTR_ERR(dentry);
 872                 goto err_release;
 873         }
 874         tty->link->driver_data = dentry;
 875
 876         retval = ptm_driver->ops->open(tty, filp);
 877         if (retval)
 878                 goto err_release;
 879
 880         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 881
 882         tty_unlock(tty);
 883         return 0;
 884 err_release:
 885         tty_unlock(tty);
 886         // This will also put-ref the fsi
 887         tty_release(inode, filp);
 888         return retval;
 889 out:
 890         devpts_kill_index(fsi, index);
 891 out_put_fsi:
 892         devpts_release(fsi);
 893 out_free_file:
 894         tty_free_file(filp);
 895         return retval;
 896 }
 897
 898 static struct file_operations ptmx_fops __ro_after_init;
 899
 900 static void __init unix98_pty_init(void)
 901 {
 902         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 903                         TTY_DRIVER_RESET_TERMIOS |
 904                         TTY_DRIVER_REAL_RAW |
 905                         TTY_DRIVER_DYNAMIC_DEV |
 906                         TTY_DRIVER_DEVPTS_MEM |
 907                         TTY_DRIVER_DYNAMIC_ALLOC);
 908         if (IS_ERR(ptm_driver))
 909                 panic("Couldn't allocate Unix98 ptm driver");
 910         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 911                         TTY_DRIVER_RESET_TERMIOS |
 912                         TTY_DRIVER_REAL_RAW |
 913                         TTY_DRIVER_DYNAMIC_DEV |
 914                         TTY_DRIVER_DEVPTS_MEM |
 915                         TTY_DRIVER_DYNAMIC_ALLOC);
 916         if (IS_ERR(pts_driver))
 917                 panic("Couldn't allocate Unix98 pts driver");
 918
 919         ptm_driver->driver_name = "pty_master";
 920         ptm_driver->name = "ptm";
 921         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 922         ptm_driver->minor_start = 0;
 923         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 924         ptm_driver->subtype = PTY_TYPE_MASTER;
 925         ptm_driver->init_termios = tty_std_termios;
 926         ptm_driver->init_termios.c_iflag = 0;
 927         ptm_driver->init_termios.c_oflag = 0;
 928         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 929         ptm_driver->init_termios.c_lflag = 0;
 930         ptm_driver->init_termios.c_ispeed = 38400;
 931         ptm_driver->init_termios.c_ospeed = 38400;
 932         ptm_driver->other = pts_driver;
 933         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 934
 935         pts_driver->driver_name = "pty_slave";
 936         pts_driver->name = "pts";
 937         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 938         pts_driver->minor_start = 0;
 939         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 940         pts_driver->subtype = PTY_TYPE_SLAVE;
 941         pts_driver->init_termios = tty_std_termios;
 942         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 943         pts_driver->init_termios.c_ispeed = 38400;
 944         pts_driver->init_termios.c_ospeed = 38400;
 945         pts_driver->other = ptm_driver;
 946         tty_set_operations(pts_driver, &pty_unix98_ops);
 947
 948         if (tty_register_driver(ptm_driver))
 949                 panic("Couldn't register Unix98 ptm driver");
 950         if (tty_register_driver(pts_driver))
 951                 panic("Couldn't register Unix98 pts driver");
 952
 953         /* Now create the /dev/ptmx special device */
 954         tty_default_fops(&ptmx_fops);
 955         ptmx_fops.open = ptmx_open;
 956
 957         cdev_init(&ptmx_cdev, &ptmx_fops);
 958         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 959             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 960                 panic("Couldn't register /dev/ptmx driver");
 961         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 962 }
 963
 964 #else
 965 static inline void unix98_pty_init(void) { }
 966 #endif
 967
 968 static int __init pty_init(void)
 969 {
 970         legacy_pty_init();
 971         unix98_pty_init();
 972         return 0;
 973 }
 974 device_initcall(pty_init);