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
  33 #undef TTY_DEBUG_HANGUP
  34 #ifdef TTY_DEBUG_HANGUP
  35 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
  36 #else
  37 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
  38 #endif
  39
  40 #ifdef CONFIG_UNIX98_PTYS
  41 static struct tty_driver *ptm_driver;
  42 static struct tty_driver *pts_driver;
  43 static DEFINE_MUTEX(devpts_mutex);
  44 #endif
  45
  46 static void pty_close(struct tty_struct *tty, struct file *filp)
  47 {
  48         if (tty->driver->subtype == PTY_TYPE_MASTER)
  49                 WARN_ON(tty->count > 1);
  50         else {
  51                 if (tty_io_error(tty))
  52                         return;
  53                 if (tty->count > 2)
  54                         return;
  55         }
  56         set_bit(TTY_IO_ERROR, &tty->flags);
  57         wake_up_interruptible(&tty->read_wait);
  58         wake_up_interruptible(&tty->write_wait);
  59         spin_lock_irq(&tty->ctrl_lock);
  60         tty->packet = 0;
  61         spin_unlock_irq(&tty->ctrl_lock);
  62         /* Review - krefs on tty_link ?? */
  63         if (!tty->link)
  64                 return;
  65         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  66         wake_up_interruptible(&tty->link->read_wait);
  67         wake_up_interruptible(&tty->link->write_wait);
  68         if (tty->driver->subtype == PTY_TYPE_MASTER) {
  69                 struct file *f;
  70
  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
  80                 /*
  81                  * This hack is required because a program can open a
  82                  * pty and redirect a console to it, but if the pty is
  83                  * closed and the console is not released, then the
  84                  * slave side will never close.  So release the
  85                  * redirect when the master closes.
  86                  */
  87                 f = tty_release_redirect(tty->link);
  88                 if (f)
  89                         fput(f);
  90         }
  91 }
  92
  93 /*
  94  * The unthrottle routine is called by the line discipline to signal
  95  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
  96  * flag is always set, to force the line discipline to always call the
  97  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
  98  * characters in the queue.  This is necessary since each time this
  99  * happens, we need to wake up any sleeping processes that could be
 100  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
 101  * for the pty buffer to be drained.
 102  */
 103 static void pty_unthrottle(struct tty_struct *tty)
 104 {
 105         tty_wakeup(tty->link);
 106         set_bit(TTY_THROTTLED, &tty->flags);
 107 }
 108
 109 /**
 110  *      pty_write               -       write to a pty
 111  *      @tty: the tty we write from
 112  *      @buf: kernel buffer of data
 113  *      @c: bytes to write
 114  *
 115  *      Our "hardware" write method. Data is coming from the ldisc which
 116  *      may be in a non sleeping state. We simply throw this at the other
 117  *      end of the link as if we were an IRQ handler receiving stuff for
 118  *      the other side of the pty/tty pair.
 119  */
 120
 121 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 122 {
 123         struct tty_struct *to = tty->link;
 124         unsigned long flags;
 125
 126         if (tty->stopped)
 127                 return 0;
 128
 129         if (c > 0) {
 130                 spin_lock_irqsave(&to->port->lock, flags);
 131                 /* Stuff the data into the input queue of the other end */
 132                 c = tty_insert_flip_string(to->port, buf, c);
 133                 spin_unlock_irqrestore(&to->port->lock, flags);
 134                 /* And shovel */
 135                 if (c)
 136                         tty_flip_buffer_push(to->port);
 137         }
 138         return c;
 139 }
 140
 141 /**
 142  *      pty_write_room  -       write space
 143  *      @tty: tty we are writing from
 144  *
 145  *      Report how many bytes the ldisc can send into the queue for
 146  *      the other device.
 147  */
 148
 149 static int pty_write_room(struct tty_struct *tty)
 150 {
 151         if (tty->stopped)
 152                 return 0;
 153         return tty_buffer_space_avail(tty->link->port);
 154 }
 155
 156 /**
 157  *      pty_chars_in_buffer     -       characters currently in our tx queue
 158  *      @tty: our tty
 159  *
 160  *      Report how much we have in the transmit queue. As everything is
 161  *      instantly at the other end this is easy to implement.
 162  */
 163
 164 static int pty_chars_in_buffer(struct tty_struct *tty)
 165 {
 166         return 0;
 167 }
 168
 169 /* Set the lock flag on a pty */
 170 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 171 {
 172         int val;
 173         if (get_user(val, arg))
 174                 return -EFAULT;
 175         if (val)
 176                 set_bit(TTY_PTY_LOCK, &tty->flags);
 177         else
 178                 clear_bit(TTY_PTY_LOCK, &tty->flags);
 179         return 0;
 180 }
 181
 182 static int pty_get_lock(struct tty_struct *tty, int __user *arg)
 183 {
 184         int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
 185         return put_user(locked, arg);
 186 }
 187
 188 /* Set the packet mode on a pty */
 189 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
 190 {
 191         int pktmode;
 192
 193         if (get_user(pktmode, arg))
 194                 return -EFAULT;
 195
 196         spin_lock_irq(&tty->ctrl_lock);
 197         if (pktmode) {
 198                 if (!tty->packet) {
 199                         tty->link->ctrl_status = 0;
 200                         smp_mb();
 201                         tty->packet = 1;
 202                 }
 203         } else
 204                 tty->packet = 0;
 205         spin_unlock_irq(&tty->ctrl_lock);
 206
 207         return 0;
 208 }
 209
 210 /* Get the packet mode of a pty */
 211 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
 212 {
 213         int pktmode = tty->packet;
 214         return put_user(pktmode, arg);
 215 }
 216
 217 /* Send a signal to the slave */
 218 static int pty_signal(struct tty_struct *tty, int sig)
 219 {
 220         struct pid *pgrp;
 221
 222         if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
 223                 return -EINVAL;
 224
 225         if (tty->link) {
 226                 pgrp = tty_get_pgrp(tty->link);
 227                 if (pgrp)
 228                         kill_pgrp(pgrp, sig, 1);
 229                 put_pid(pgrp);
 230         }
 231         return 0;
 232 }
 233
 234 static void pty_flush_buffer(struct tty_struct *tty)
 235 {
 236         struct tty_struct *to = tty->link;
 237
 238         if (!to)
 239                 return;
 240
 241         tty_buffer_flush(to, NULL);
 242         if (to->packet) {
 243                 spin_lock_irq(&tty->ctrl_lock);
 244                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
 245                 wake_up_interruptible(&to->read_wait);
 246                 spin_unlock_irq(&tty->ctrl_lock);
 247         }
 248 }
 249
 250 static int pty_open(struct tty_struct *tty, struct file *filp)
 251 {
 252         if (!tty || !tty->link)
 253                 return -ENODEV;
 254
 255         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 256                 goto out;
 257         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
 258                 goto out;
 259         if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
 260                 goto out;
 261
 262         clear_bit(TTY_IO_ERROR, &tty->flags);
 263         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 264         set_bit(TTY_THROTTLED, &tty->flags);
 265         return 0;
 266
 267 out:
 268         set_bit(TTY_IO_ERROR, &tty->flags);
 269         return -EIO;
 270 }
 271
 272 static void pty_set_termios(struct tty_struct *tty,
 273                                         struct ktermios *old_termios)
 274 {
 275         /* See if packet mode change of state. */
 276         if (tty->link && tty->link->packet) {
 277                 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
 278                 int old_flow = ((old_termios->c_iflag & IXON) &&
 279                                 (old_termios->c_cc[VSTOP] == '\023') &&
 280                                 (old_termios->c_cc[VSTART] == '\021'));
 281                 int new_flow = (I_IXON(tty) &&
 282                                 STOP_CHAR(tty) == '\023' &&
 283                                 START_CHAR(tty) == '\021');
 284                 if ((old_flow != new_flow) || extproc) {
 285                         spin_lock_irq(&tty->ctrl_lock);
 286                         if (old_flow != new_flow) {
 287                                 tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
 288                                 if (new_flow)
 289                                         tty->ctrl_status |= TIOCPKT_DOSTOP;
 290                                 else
 291                                         tty->ctrl_status |= TIOCPKT_NOSTOP;
 292                         }
 293                         if (extproc)
 294                                 tty->ctrl_status |= TIOCPKT_IOCTL;
 295                         spin_unlock_irq(&tty->ctrl_lock);
 296                         wake_up_interruptible(&tty->link->read_wait);
 297                 }
 298         }
 299
 300         tty->termios.c_cflag &= ~(CSIZE | PARENB);
 301         tty->termios.c_cflag |= (CS8 | CREAD);
 302 }
 303
 304 /**
 305  *      pty_do_resize           -       resize event
 306  *      @tty: tty being resized
 307  *      @ws: window size being set.
 308  *
 309  *      Update the termios variables and send the necessary signals to
 310  *      peform a terminal resize correctly
 311  */
 312
 313 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 314 {
 315         struct pid *pgrp, *rpgrp;
 316         struct tty_struct *pty = tty->link;
 317
 318         /* For a PTY we need to lock the tty side */
 319         mutex_lock(&tty->winsize_mutex);
 320         if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 321                 goto done;
 322
 323         /* Signal the foreground process group of both ptys */
 324         pgrp = tty_get_pgrp(tty);
 325         rpgrp = tty_get_pgrp(pty);
 326
 327         if (pgrp)
 328                 kill_pgrp(pgrp, SIGWINCH, 1);
 329         if (rpgrp != pgrp && rpgrp)
 330                 kill_pgrp(rpgrp, SIGWINCH, 1);
 331
 332         put_pid(pgrp);
 333         put_pid(rpgrp);
 334
 335         tty->winsize = *ws;
 336         pty->winsize = *ws;     /* Never used so will go away soon */
 337 done:
 338         mutex_unlock(&tty->winsize_mutex);
 339         return 0;
 340 }
 341
 342 /**
 343  *      pty_start - start() handler
 344  *      pty_stop  - stop() handler
 345  *      @tty: tty being flow-controlled
 346  *
 347  *      Propagates the TIOCPKT status to the master pty.
 348  *
 349  *      NB: only the master pty can be in packet mode so only the slave
 350  *          needs start()/stop() handlers
 351  */
 352 static void pty_start(struct tty_struct *tty)
 353 {
 354         unsigned long flags;
 355
 356         if (tty->link && tty->link->packet) {
 357                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 358                 tty->ctrl_status &= ~TIOCPKT_STOP;
 359                 tty->ctrl_status |= TIOCPKT_START;
 360                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 361                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 362         }
 363 }
 364
 365 static void pty_stop(struct tty_struct *tty)
 366 {
 367         unsigned long flags;
 368
 369         if (tty->link && tty->link->packet) {
 370                 spin_lock_irqsave(&tty->ctrl_lock, flags);
 371                 tty->ctrl_status &= ~TIOCPKT_START;
 372                 tty->ctrl_status |= TIOCPKT_STOP;
 373                 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 374                 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
 375         }
 376 }
 377
 378 /**
 379  *      pty_common_install              -       set up the pty pair
 380  *      @driver: the pty driver
 381  *      @tty: the tty being instantiated
 382  *      @legacy: true if this is BSD style
 383  *
 384  *      Perform the initial set up for the tty/pty pair. Called from the
 385  *      tty layer when the port is first opened.
 386  *
 387  *      Locking: the caller must hold the tty_mutex
 388  */
 389 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 390                 bool legacy)
 391 {
 392         struct tty_struct *o_tty;
 393         struct tty_port *ports[2];
 394         int idx = tty->index;
 395         int retval = -ENOMEM;
 396
 397         /* Opening the slave first has always returned -EIO */
 398         if (driver->subtype != PTY_TYPE_MASTER)
 399                 return -EIO;
 400
 401         ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
 402         ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
 403         if (!ports[0] || !ports[1])
 404                 goto err;
 405         if (!try_module_get(driver->other->owner)) {
 406                 /* This cannot in fact currently happen */
 407                 goto err;
 408         }
 409         o_tty = alloc_tty_struct(driver->other, idx);
 410         if (!o_tty)
 411                 goto err_put_module;
 412
 413         tty_set_lock_subclass(o_tty);
 414         lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
 415
 416         if (legacy) {
 417                 /* We always use new tty termios data so we can do this
 418                    the easy way .. */
 419                 tty_init_termios(tty);
 420                 tty_init_termios(o_tty);
 421
 422                 driver->other->ttys[idx] = o_tty;
 423                 driver->ttys[idx] = tty;
 424         } else {
 425                 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
 426                 tty->termios = driver->init_termios;
 427                 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
 428                 o_tty->termios = driver->other->init_termios;
 429         }
 430
 431         /*
 432          * Everything allocated ... set up the o_tty structure.
 433          */
 434         tty_driver_kref_get(driver->other);
 435         /* Establish the links in both directions */
 436         tty->link   = o_tty;
 437         o_tty->link = tty;
 438         tty_port_init(ports[0]);
 439         tty_port_init(ports[1]);
 440         tty_buffer_set_limit(ports[0], 8192);
 441         tty_buffer_set_limit(ports[1], 8192);
 442         o_tty->port = ports[0];
 443         tty->port = ports[1];
 444         o_tty->port->itty = o_tty;
 445
 446         tty_buffer_set_lock_subclass(o_tty->port);
 447
 448         tty_driver_kref_get(driver);
 449         tty->count++;
 450         o_tty->count++;
 451         return 0;
 452
 453 err_put_module:
 454         module_put(driver->other->owner);
 455 err:
 456         kfree(ports[0]);
 457         kfree(ports[1]);
 458         return retval;
 459 }
 460
 461 static void pty_cleanup(struct tty_struct *tty)
 462 {
 463         tty_port_put(tty->port);
 464 }
 465
 466 /* Traditional BSD devices */
 467 #ifdef CONFIG_LEGACY_PTYS
 468
 469 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
 470 {
 471         return pty_common_install(driver, tty, true);
 472 }
 473
 474 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
 475 {
 476         struct tty_struct *pair = tty->link;
 477         driver->ttys[tty->index] = NULL;
 478         if (pair)
 479                 pair->driver->ttys[pair->index] = NULL;
 480 }
 481
 482 static int pty_bsd_ioctl(struct tty_struct *tty,
 483                          unsigned int cmd, unsigned long arg)
 484 {
 485         switch (cmd) {
 486         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 487                 return pty_set_lock(tty, (int __user *) arg);
 488         case TIOCGPTLCK: /* Get PT Lock status */
 489                 return pty_get_lock(tty, (int __user *)arg);
 490         case TIOCPKT: /* Set PT packet mode */
 491                 return pty_set_pktmode(tty, (int __user *)arg);
 492         case TIOCGPKT: /* Get PT packet mode */
 493                 return pty_get_pktmode(tty, (int __user *)arg);
 494         case TIOCSIG:    /* Send signal to other side of pty */
 495                 return pty_signal(tty, (int) arg);
 496         case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
 497                 return -EINVAL;
 498         }
 499         return -ENOIOCTLCMD;
 500 }
 501
 502 #ifdef CONFIG_COMPAT
 503 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
 504                                  unsigned int cmd, unsigned long arg)
 505 {
 506         /*
 507          * PTY ioctls don't require any special translation between 32-bit and
 508          * 64-bit userspace, they are already compatible.
 509          */
 510         return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
 511 }
 512 #else
 513 #define pty_bsd_compat_ioctl NULL
 514 #endif
 515
 516 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
 517 /*
 518  * not really modular, but the easiest way to keep compat with existing
 519  * bootargs behaviour is to continue using module_param here.
 520  */
 521 module_param(legacy_count, int, 0);
 522
 523 /*
 524  * The master side of a pty can do TIOCSPTLCK and thus
 525  * has pty_bsd_ioctl.
 526  */
 527 static const struct tty_operations master_pty_ops_bsd = {
 528         .install = pty_install,
 529         .open = pty_open,
 530         .close = pty_close,
 531         .write = pty_write,
 532         .write_room = pty_write_room,
 533         .flush_buffer = pty_flush_buffer,
 534         .chars_in_buffer = pty_chars_in_buffer,
 535         .unthrottle = pty_unthrottle,
 536         .ioctl = pty_bsd_ioctl,
 537         .compat_ioctl = pty_bsd_compat_ioctl,
 538         .cleanup = pty_cleanup,
 539         .resize = pty_resize,
 540         .remove = pty_remove
 541 };
 542
 543 static const struct tty_operations slave_pty_ops_bsd = {
 544         .install = pty_install,
 545         .open = pty_open,
 546         .close = pty_close,
 547         .write = pty_write,
 548         .write_room = pty_write_room,
 549         .flush_buffer = pty_flush_buffer,
 550         .chars_in_buffer = pty_chars_in_buffer,
 551         .unthrottle = pty_unthrottle,
 552         .set_termios = pty_set_termios,
 553         .cleanup = pty_cleanup,
 554         .resize = pty_resize,
 555         .start = pty_start,
 556         .stop = pty_stop,
 557         .remove = pty_remove
 558 };
 559
 560 static void __init legacy_pty_init(void)
 561 {
 562         struct tty_driver *pty_driver, *pty_slave_driver;
 563
 564         if (legacy_count <= 0)
 565                 return;
 566
 567         pty_driver = tty_alloc_driver(legacy_count,
 568                         TTY_DRIVER_RESET_TERMIOS |
 569                         TTY_DRIVER_REAL_RAW |
 570                         TTY_DRIVER_DYNAMIC_ALLOC);
 571         if (IS_ERR(pty_driver))
 572                 panic("Couldn't allocate pty driver");
 573
 574         pty_slave_driver = tty_alloc_driver(legacy_count,
 575                         TTY_DRIVER_RESET_TERMIOS |
 576                         TTY_DRIVER_REAL_RAW |
 577                         TTY_DRIVER_DYNAMIC_ALLOC);
 578         if (IS_ERR(pty_slave_driver))
 579                 panic("Couldn't allocate pty slave driver");
 580
 581         pty_driver->driver_name = "pty_master";
 582         pty_driver->name = "pty";
 583         pty_driver->major = PTY_MASTER_MAJOR;
 584         pty_driver->minor_start = 0;
 585         pty_driver->type = TTY_DRIVER_TYPE_PTY;
 586         pty_driver->subtype = PTY_TYPE_MASTER;
 587         pty_driver->init_termios = tty_std_termios;
 588         pty_driver->init_termios.c_iflag = 0;
 589         pty_driver->init_termios.c_oflag = 0;
 590         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 591         pty_driver->init_termios.c_lflag = 0;
 592         pty_driver->init_termios.c_ispeed = 38400;
 593         pty_driver->init_termios.c_ospeed = 38400;
 594         pty_driver->other = pty_slave_driver;
 595         tty_set_operations(pty_driver, &master_pty_ops_bsd);
 596
 597         pty_slave_driver->driver_name = "pty_slave";
 598         pty_slave_driver->name = "ttyp";
 599         pty_slave_driver->major = PTY_SLAVE_MAJOR;
 600         pty_slave_driver->minor_start = 0;
 601         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
 602         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
 603         pty_slave_driver->init_termios = tty_std_termios;
 604         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 605         pty_slave_driver->init_termios.c_ispeed = 38400;
 606         pty_slave_driver->init_termios.c_ospeed = 38400;
 607         pty_slave_driver->other = pty_driver;
 608         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 609
 610         if (tty_register_driver(pty_driver))
 611                 panic("Couldn't register pty driver");
 612         if (tty_register_driver(pty_slave_driver))
 613                 panic("Couldn't register pty slave driver");
 614 }
 615 #else
 616 static inline void legacy_pty_init(void) { }
 617 #endif
 618
 619 /* Unix98 devices */
 620 #ifdef CONFIG_UNIX98_PTYS
 621 static struct cdev ptmx_cdev;
 622
 623 /**
 624  *      ptm_open_peer - open the peer of a pty
 625  *      @master: the open struct file of the ptmx device node
 626  *      @tty: the master of the pty being opened
 627  *      @flags: the flags for open
 628  *
 629  *      Provide a race free way for userspace to open the slave end of a pty
 630  *      (where they have the master fd and cannot access or trust the mount
 631  *      namespace /dev/pts was mounted inside).
 632  */
 633 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
 634 {
 635         int fd = -1;
 636         struct file *filp;
 637         int retval = -EINVAL;
 638         struct path path;
 639
 640         if (tty->driver != ptm_driver)
 641                 return -EIO;
 642
 643         fd = get_unused_fd_flags(flags);
 644         if (fd < 0) {
 645                 retval = fd;
 646                 goto err;
 647         }
 648
 649         /* Compute the slave's path */
 650         path.mnt = devpts_mntget(master, tty->driver_data);
 651         if (IS_ERR(path.mnt)) {
 652                 retval = PTR_ERR(path.mnt);
 653                 goto err_put;
 654         }
 655         path.dentry = tty->link->driver_data;
 656
 657         filp = dentry_open(&path, flags, current_cred());
 658         mntput(path.mnt);
 659         if (IS_ERR(filp)) {
 660                 retval = PTR_ERR(filp);
 661                 goto err_put;
 662         }
 663
 664         fd_install(fd, filp);
 665         return fd;
 666
 667 err_put:
 668         put_unused_fd(fd);
 669 err:
 670         return retval;
 671 }
 672
 673 static int pty_unix98_ioctl(struct tty_struct *tty,
 674                             unsigned int cmd, unsigned long arg)
 675 {
 676         switch (cmd) {
 677         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
 678                 return pty_set_lock(tty, (int __user *)arg);
 679         case TIOCGPTLCK: /* Get PT Lock status */
 680                 return pty_get_lock(tty, (int __user *)arg);
 681         case TIOCPKT: /* Set PT packet mode */
 682                 return pty_set_pktmode(tty, (int __user *)arg);
 683         case TIOCGPKT: /* Get PT packet mode */
 684                 return pty_get_pktmode(tty, (int __user *)arg);
 685         case TIOCGPTN: /* Get PT Number */
 686                 return put_user(tty->index, (unsigned int __user *)arg);
 687         case TIOCSIG:    /* Send signal to other side of pty */
 688                 return pty_signal(tty, (int) arg);
 689         }
 690
 691         return -ENOIOCTLCMD;
 692 }
 693
 694 #ifdef CONFIG_COMPAT
 695 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
 696                                  unsigned int cmd, unsigned long arg)
 697 {
 698         /*
 699          * PTY ioctls don't require any special translation between 32-bit and
 700          * 64-bit userspace, they are already compatible.
 701          */
 702         return pty_unix98_ioctl(tty, cmd,
 703                 cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg));
 704 }
 705 #else
 706 #define pty_unix98_compat_ioctl NULL
 707 #endif
 708
 709 /**
 710  *      ptm_unix98_lookup       -       find a pty master
 711  *      @driver: ptm driver
 712  *      @file: unused
 713  *      @idx: tty index
 714  *
 715  *      Look up a pty master device. Called under the tty_mutex for now.
 716  *      This provides our locking.
 717  */
 718
 719 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
 720                 struct file *file, int idx)
 721 {
 722         /* Master must be open via /dev/ptmx */
 723         return ERR_PTR(-EIO);
 724 }
 725
 726 /**
 727  *      pts_unix98_lookup       -       find a pty slave
 728  *      @driver: pts driver
 729  *      @file: file pointer to tty
 730  *      @idx: tty index
 731  *
 732  *      Look up a pty master device. Called under the tty_mutex for now.
 733  *      This provides our locking for the tty pointer.
 734  */
 735
 736 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
 737                 struct file *file, int idx)
 738 {
 739         struct tty_struct *tty;
 740
 741         mutex_lock(&devpts_mutex);
 742         tty = devpts_get_priv(file->f_path.dentry);
 743         mutex_unlock(&devpts_mutex);
 744         /* Master must be open before slave */
 745         if (!tty)
 746                 return ERR_PTR(-EIO);
 747         return tty;
 748 }
 749
 750 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
 751 {
 752         return pty_common_install(driver, tty, false);
 753 }
 754
 755 /* this is called once with whichever end is closed last */
 756 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 757 {
 758         struct pts_fs_info *fsi;
 759
 760         if (tty->driver->subtype == PTY_TYPE_MASTER)
 761                 fsi = tty->driver_data;
 762         else
 763                 fsi = tty->link->driver_data;
 764
 765         if (fsi) {
 766                 devpts_kill_index(fsi, tty->index);
 767                 devpts_release(fsi);
 768         }
 769 }
 770
 771 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
 772 {
 773         seq_printf(m, "tty-index:\t%d\n", tty->index);
 774 }
 775
 776 static const struct tty_operations ptm_unix98_ops = {
 777         .lookup = ptm_unix98_lookup,
 778         .install = pty_unix98_install,
 779         .remove = pty_unix98_remove,
 780         .open = pty_open,
 781         .close = pty_close,
 782         .write = pty_write,
 783         .write_room = pty_write_room,
 784         .flush_buffer = pty_flush_buffer,
 785         .chars_in_buffer = pty_chars_in_buffer,
 786         .unthrottle = pty_unthrottle,
 787         .ioctl = pty_unix98_ioctl,
 788         .compat_ioctl = pty_unix98_compat_ioctl,
 789         .resize = pty_resize,
 790         .cleanup = pty_cleanup,
 791         .show_fdinfo = pty_show_fdinfo,
 792 };
 793
 794 static const struct tty_operations pty_unix98_ops = {
 795         .lookup = pts_unix98_lookup,
 796         .install = pty_unix98_install,
 797         .remove = pty_unix98_remove,
 798         .open = pty_open,
 799         .close = pty_close,
 800         .write = pty_write,
 801         .write_room = pty_write_room,
 802         .flush_buffer = pty_flush_buffer,
 803         .chars_in_buffer = pty_chars_in_buffer,
 804         .unthrottle = pty_unthrottle,
 805         .set_termios = pty_set_termios,
 806         .start = pty_start,
 807         .stop = pty_stop,
 808         .cleanup = pty_cleanup,
 809 };
 810
 811 /**
 812  *      ptmx_open               -       open a unix 98 pty master
 813  *      @inode: inode of device file
 814  *      @filp: file pointer to tty
 815  *
 816  *      Allocate a unix98 pty master device from the ptmx driver.
 817  *
 818  *      Locking: tty_mutex protects the init_dev work. tty->count should
 819  *              protect the rest.
 820  *              allocated_ptys_lock handles the list of free pty numbers
 821  */
 822
 823 static int ptmx_open(struct inode *inode, struct file *filp)
 824 {
 825         struct pts_fs_info *fsi;
 826         struct tty_struct *tty;
 827         struct dentry *dentry;
 828         int retval;
 829         int index;
 830
 831         nonseekable_open(inode, filp);
 832
 833         /* We refuse fsnotify events on ptmx, since it's a shared resource */
 834         filp->f_mode |= FMODE_NONOTIFY;
 835
 836         retval = tty_alloc_file(filp);
 837         if (retval)
 838                 return retval;
 839
 840         fsi = devpts_acquire(filp);
 841         if (IS_ERR(fsi)) {
 842                 retval = PTR_ERR(fsi);
 843                 goto out_free_file;
 844         }
 845
 846         /* find a device that is not in use. */
 847         mutex_lock(&devpts_mutex);
 848         index = devpts_new_index(fsi);
 849         mutex_unlock(&devpts_mutex);
 850
 851         retval = index;
 852         if (index < 0)
 853                 goto out_put_fsi;
 854
 855
 856         mutex_lock(&tty_mutex);
 857         tty = tty_init_dev(ptm_driver, index);
 858         /* The tty returned here is locked so we can safely
 859            drop the mutex */
 860         mutex_unlock(&tty_mutex);
 861
 862         retval = PTR_ERR(tty);
 863         if (IS_ERR(tty))
 864                 goto out;
 865
 866         /*
 867          * From here on out, the tty is "live", and the index and
 868          * fsi will be killed/put by the tty_release()
 869          */
 870         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 871         tty->driver_data = fsi;
 872
 873         tty_add_file(tty, filp);
 874
 875         dentry = devpts_pty_new(fsi, index, tty->link);
 876         if (IS_ERR(dentry)) {
 877                 retval = PTR_ERR(dentry);
 878                 goto err_release;
 879         }
 880         tty->link->driver_data = dentry;
 881
 882         retval = ptm_driver->ops->open(tty, filp);
 883         if (retval)
 884                 goto err_release;
 885
 886         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
 887
 888         tty_unlock(tty);
 889         return 0;
 890 err_release:
 891         tty_unlock(tty);
 892         // This will also put-ref the fsi
 893         tty_release(inode, filp);
 894         return retval;
 895 out:
 896         devpts_kill_index(fsi, index);
 897 out_put_fsi:
 898         devpts_release(fsi);
 899 out_free_file:
 900         tty_free_file(filp);
 901         return retval;
 902 }
 903
 904 static struct file_operations ptmx_fops __ro_after_init;
 905
 906 static void __init unix98_pty_init(void)
 907 {
 908         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 909                         TTY_DRIVER_RESET_TERMIOS |
 910                         TTY_DRIVER_REAL_RAW |
 911                         TTY_DRIVER_DYNAMIC_DEV |
 912                         TTY_DRIVER_DEVPTS_MEM |
 913                         TTY_DRIVER_DYNAMIC_ALLOC);
 914         if (IS_ERR(ptm_driver))
 915                 panic("Couldn't allocate Unix98 ptm driver");
 916         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 917                         TTY_DRIVER_RESET_TERMIOS |
 918                         TTY_DRIVER_REAL_RAW |
 919                         TTY_DRIVER_DYNAMIC_DEV |
 920                         TTY_DRIVER_DEVPTS_MEM |
 921                         TTY_DRIVER_DYNAMIC_ALLOC);
 922         if (IS_ERR(pts_driver))
 923                 panic("Couldn't allocate Unix98 pts driver");
 924
 925         ptm_driver->driver_name = "pty_master";
 926         ptm_driver->name = "ptm";
 927         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
 928         ptm_driver->minor_start = 0;
 929         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
 930         ptm_driver->subtype = PTY_TYPE_MASTER;
 931         ptm_driver->init_termios = tty_std_termios;
 932         ptm_driver->init_termios.c_iflag = 0;
 933         ptm_driver->init_termios.c_oflag = 0;
 934         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 935         ptm_driver->init_termios.c_lflag = 0;
 936         ptm_driver->init_termios.c_ispeed = 38400;
 937         ptm_driver->init_termios.c_ospeed = 38400;
 938         ptm_driver->other = pts_driver;
 939         tty_set_operations(ptm_driver, &ptm_unix98_ops);
 940
 941         pts_driver->driver_name = "pty_slave";
 942         pts_driver->name = "pts";
 943         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
 944         pts_driver->minor_start = 0;
 945         pts_driver->type = TTY_DRIVER_TYPE_PTY;
 946         pts_driver->subtype = PTY_TYPE_SLAVE;
 947         pts_driver->init_termios = tty_std_termios;
 948         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 949         pts_driver->init_termios.c_ispeed = 38400;
 950         pts_driver->init_termios.c_ospeed = 38400;
 951         pts_driver->other = ptm_driver;
 952         tty_set_operations(pts_driver, &pty_unix98_ops);
 953
 954         if (tty_register_driver(ptm_driver))
 955                 panic("Couldn't register Unix98 ptm driver");
 956         if (tty_register_driver(pts_driver))
 957                 panic("Couldn't register Unix98 pts driver");
 958
 959         /* Now create the /dev/ptmx special device */
 960         tty_default_fops(&ptmx_fops);
 961         ptmx_fops.open = ptmx_open;
 962
 963         cdev_init(&ptmx_cdev, &ptmx_fops);
 964         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
 965             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
 966                 panic("Couldn't register /dev/ptmx driver");
 967         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 968 }
 969
 970 #else
 971 static inline void unix98_pty_init(void) { }
 972 #endif
 973
 974 static int __init pty_init(void)
 975 {
 976         legacy_pty_init();
 977         unix98_pty_init();
 978         return 0;
 979 }
 980 device_initcall(pty_init);