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 32 #undef TTY_DEBUG_HANGUP 33 #ifdef TTY_DEBUG_HANGUP 34 # define tty_debug_hangup(tty, f, args...) tty_debug(tty, f, ##args) 35 #else 36 # define tty_debug_hangup(tty, f, args...) do {} while (0) 37 #endif 38 39 #ifdef CONFIG_UNIX98_PTYS 40 static struct tty_driver *ptm_driver; 41 static struct tty_driver *pts_driver; 42 static DEFINE_MUTEX(devpts_mutex); 43 #endif 44 45 static void pty_close(struct tty_struct *tty, struct file *filp) 46 { 47 BUG_ON(!tty); 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 set_bit(TTY_OTHER_CLOSED, &tty->flags); 70 #ifdef CONFIG_UNIX98_PTYS 71 if (tty->driver == ptm_driver) { 72 mutex_lock(&devpts_mutex); 73 if (tty->link->driver_data) 74 devpts_pty_kill(tty->link->driver_data); 75 mutex_unlock(&devpts_mutex); 76 } 77 #endif 78 tty_vhangup(tty->link); 79 } 80 } 81 82 /* 83 * The unthrottle routine is called by the line discipline to signal 84 * that it can receive more characters. For PTY's, the TTY_THROTTLED 85 * flag is always set, to force the line discipline to always call the 86 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE 87 * characters in the queue. This is necessary since each time this 88 * happens, we need to wake up any sleeping processes that could be 89 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent() 90 * for the pty buffer to be drained. 91 */ 92 static void pty_unthrottle(struct tty_struct *tty) 93 { 94 tty_wakeup(tty->link); 95 set_bit(TTY_THROTTLED, &tty->flags); 96 } 97 98 /** 99 * pty_write - write to a pty 100 * @tty: the tty we write from 101 * @buf: kernel buffer of data 102 * @count: bytes to write 103 * 104 * Our "hardware" write method. Data is coming from the ldisc which 105 * may be in a non sleeping state. We simply throw this at the other 106 * end of the link as if we were an IRQ handler receiving stuff for 107 * the other side of the pty/tty pair. 108 */ 109 110 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c) 111 { 112 struct tty_struct *to = tty->link; 113 114 if (tty->stopped) 115 return 0; 116 117 if (c > 0) { 118 /* Stuff the data into the input queue of the other end */ 119 c = tty_insert_flip_string(to->port, buf, c); 120 /* And shovel */ 121 if (c) 122 tty_flip_buffer_push(to->port); 123 } 124 return c; 125 } 126 127 /** 128 * pty_write_room - write space 129 * @tty: tty we are writing from 130 * 131 * Report how many bytes the ldisc can send into the queue for 132 * the other device. 133 */ 134 135 static int pty_write_room(struct tty_struct *tty) 136 { 137 if (tty->stopped) 138 return 0; 139 return tty_buffer_space_avail(tty->link->port); 140 } 141 142 /** 143 * pty_chars_in_buffer - characters currently in our tx queue 144 * @tty: our tty 145 * 146 * Report how much we have in the transmit queue. As everything is 147 * instantly at the other end this is easy to implement. 148 */ 149 150 static int pty_chars_in_buffer(struct tty_struct *tty) 151 { 152 return 0; 153 } 154 155 /* Set the lock flag on a pty */ 156 static int pty_set_lock(struct tty_struct *tty, int __user *arg) 157 { 158 int val; 159 if (get_user(val, arg)) 160 return -EFAULT; 161 if (val) 162 set_bit(TTY_PTY_LOCK, &tty->flags); 163 else 164 clear_bit(TTY_PTY_LOCK, &tty->flags); 165 return 0; 166 } 167 168 static int pty_get_lock(struct tty_struct *tty, int __user *arg) 169 { 170 int locked = test_bit(TTY_PTY_LOCK, &tty->flags); 171 return put_user(locked, arg); 172 } 173 174 /* Set the packet mode on a pty */ 175 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg) 176 { 177 int pktmode; 178 179 if (get_user(pktmode, arg)) 180 return -EFAULT; 181 182 spin_lock_irq(&tty->ctrl_lock); 183 if (pktmode) { 184 if (!tty->packet) { 185 tty->link->ctrl_status = 0; 186 smp_mb(); 187 tty->packet = 1; 188 } 189 } else 190 tty->packet = 0; 191 spin_unlock_irq(&tty->ctrl_lock); 192 193 return 0; 194 } 195 196 /* Get the packet mode of a pty */ 197 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg) 198 { 199 int pktmode = tty->packet; 200 return put_user(pktmode, arg); 201 } 202 203 /* Send a signal to the slave */ 204 static int pty_signal(struct tty_struct *tty, int sig) 205 { 206 struct pid *pgrp; 207 208 if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP) 209 return -EINVAL; 210 211 if (tty->link) { 212 pgrp = tty_get_pgrp(tty->link); 213 if (pgrp) 214 kill_pgrp(pgrp, sig, 1); 215 put_pid(pgrp); 216 } 217 return 0; 218 } 219 220 static void pty_flush_buffer(struct tty_struct *tty) 221 { 222 struct tty_struct *to = tty->link; 223 224 if (!to) 225 return; 226 227 tty_buffer_flush(to, NULL); 228 if (to->packet) { 229 spin_lock_irq(&tty->ctrl_lock); 230 tty->ctrl_status |= TIOCPKT_FLUSHWRITE; 231 wake_up_interruptible(&to->read_wait); 232 spin_unlock_irq(&tty->ctrl_lock); 233 } 234 } 235 236 static int pty_open(struct tty_struct *tty, struct file *filp) 237 { 238 if (!tty || !tty->link) 239 return -ENODEV; 240 241 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) 242 goto out; 243 if (test_bit(TTY_PTY_LOCK, &tty->link->flags)) 244 goto out; 245 if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1) 246 goto out; 247 248 clear_bit(TTY_IO_ERROR, &tty->flags); 249 clear_bit(TTY_OTHER_CLOSED, &tty->link->flags); 250 set_bit(TTY_THROTTLED, &tty->flags); 251 return 0; 252 253 out: 254 set_bit(TTY_IO_ERROR, &tty->flags); 255 return -EIO; 256 } 257 258 static void pty_set_termios(struct tty_struct *tty, 259 struct ktermios *old_termios) 260 { 261 /* See if packet mode change of state. */ 262 if (tty->link && tty->link->packet) { 263 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty); 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, EPOLLIN); 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, EPOLLIN); 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 tty_init_termios(tty); 406 tty_init_termios(o_tty); 407 408 driver->other->ttys[idx] = o_tty; 409 driver->ttys[idx] = tty; 410 } else { 411 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked)); 412 tty->termios = driver->init_termios; 413 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked)); 414 o_tty->termios = driver->other->init_termios; 415 } 416 417 /* 418 * Everything allocated ... set up the o_tty structure. 419 */ 420 tty_driver_kref_get(driver->other); 421 /* Establish the links in both directions */ 422 tty->link = o_tty; 423 o_tty->link = tty; 424 tty_port_init(ports[0]); 425 tty_port_init(ports[1]); 426 tty_buffer_set_limit(ports[0], 8192); 427 tty_buffer_set_limit(ports[1], 8192); 428 o_tty->port = ports[0]; 429 tty->port = ports[1]; 430 o_tty->port->itty = o_tty; 431 432 tty_buffer_set_lock_subclass(o_tty->port); 433 434 tty_driver_kref_get(driver); 435 tty->count++; 436 o_tty->count++; 437 return 0; 438 439 err_put_module: 440 module_put(driver->other->owner); 441 err: 442 kfree(ports[0]); 443 kfree(ports[1]); 444 return retval; 445 } 446 447 static void pty_cleanup(struct tty_struct *tty) 448 { 449 tty_port_put(tty->port); 450 } 451 452 /* Traditional BSD devices */ 453 #ifdef CONFIG_LEGACY_PTYS 454 455 static int pty_install(struct tty_driver *driver, struct tty_struct *tty) 456 { 457 return pty_common_install(driver, tty, true); 458 } 459 460 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty) 461 { 462 struct tty_struct *pair = tty->link; 463 driver->ttys[tty->index] = NULL; 464 if (pair) 465 pair->driver->ttys[pair->index] = NULL; 466 } 467 468 static int pty_bsd_ioctl(struct tty_struct *tty, 469 unsigned int cmd, unsigned long arg) 470 { 471 switch (cmd) { 472 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ 473 return pty_set_lock(tty, (int __user *) arg); 474 case TIOCGPTLCK: /* Get PT Lock status */ 475 return pty_get_lock(tty, (int __user *)arg); 476 case TIOCPKT: /* Set PT packet mode */ 477 return pty_set_pktmode(tty, (int __user *)arg); 478 case TIOCGPKT: /* Get PT packet mode */ 479 return pty_get_pktmode(tty, (int __user *)arg); 480 case TIOCSIG: /* Send signal to other side of pty */ 481 return pty_signal(tty, (int) arg); 482 case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */ 483 return -EINVAL; 484 } 485 return -ENOIOCTLCMD; 486 } 487 488 static long pty_bsd_compat_ioctl(struct tty_struct *tty, 489 unsigned int cmd, unsigned long arg) 490 { 491 /* 492 * PTY ioctls don't require any special translation between 32-bit and 493 * 64-bit userspace, they are already compatible. 494 */ 495 return pty_bsd_ioctl(tty, cmd, arg); 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 .compat_ioctl = pty_bsd_compat_ioctl, 520 .cleanup = pty_cleanup, 521 .resize = pty_resize, 522 .remove = pty_remove 523 }; 524 525 static const struct tty_operations slave_pty_ops_bsd = { 526 .install = pty_install, 527 .open = pty_open, 528 .close = pty_close, 529 .write = pty_write, 530 .write_room = pty_write_room, 531 .flush_buffer = pty_flush_buffer, 532 .chars_in_buffer = pty_chars_in_buffer, 533 .unthrottle = pty_unthrottle, 534 .set_termios = pty_set_termios, 535 .cleanup = pty_cleanup, 536 .resize = pty_resize, 537 .start = pty_start, 538 .stop = pty_stop, 539 .remove = pty_remove 540 }; 541 542 static void __init legacy_pty_init(void) 543 { 544 struct tty_driver *pty_driver, *pty_slave_driver; 545 546 if (legacy_count <= 0) 547 return; 548 549 pty_driver = tty_alloc_driver(legacy_count, 550 TTY_DRIVER_RESET_TERMIOS | 551 TTY_DRIVER_REAL_RAW | 552 TTY_DRIVER_DYNAMIC_ALLOC); 553 if (IS_ERR(pty_driver)) 554 panic("Couldn't allocate pty driver"); 555 556 pty_slave_driver = tty_alloc_driver(legacy_count, 557 TTY_DRIVER_RESET_TERMIOS | 558 TTY_DRIVER_REAL_RAW | 559 TTY_DRIVER_DYNAMIC_ALLOC); 560 if (IS_ERR(pty_slave_driver)) 561 panic("Couldn't allocate pty slave driver"); 562 563 pty_driver->driver_name = "pty_master"; 564 pty_driver->name = "pty"; 565 pty_driver->major = PTY_MASTER_MAJOR; 566 pty_driver->minor_start = 0; 567 pty_driver->type = TTY_DRIVER_TYPE_PTY; 568 pty_driver->subtype = PTY_TYPE_MASTER; 569 pty_driver->init_termios = tty_std_termios; 570 pty_driver->init_termios.c_iflag = 0; 571 pty_driver->init_termios.c_oflag = 0; 572 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 573 pty_driver->init_termios.c_lflag = 0; 574 pty_driver->init_termios.c_ispeed = 38400; 575 pty_driver->init_termios.c_ospeed = 38400; 576 pty_driver->other = pty_slave_driver; 577 tty_set_operations(pty_driver, &master_pty_ops_bsd); 578 579 pty_slave_driver->driver_name = "pty_slave"; 580 pty_slave_driver->name = "ttyp"; 581 pty_slave_driver->major = PTY_SLAVE_MAJOR; 582 pty_slave_driver->minor_start = 0; 583 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY; 584 pty_slave_driver->subtype = PTY_TYPE_SLAVE; 585 pty_slave_driver->init_termios = tty_std_termios; 586 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 587 pty_slave_driver->init_termios.c_ispeed = 38400; 588 pty_slave_driver->init_termios.c_ospeed = 38400; 589 pty_slave_driver->other = pty_driver; 590 tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd); 591 592 if (tty_register_driver(pty_driver)) 593 panic("Couldn't register pty driver"); 594 if (tty_register_driver(pty_slave_driver)) 595 panic("Couldn't register pty slave driver"); 596 } 597 #else 598 static inline void legacy_pty_init(void) { } 599 #endif 600 601 /* Unix98 devices */ 602 #ifdef CONFIG_UNIX98_PTYS 603 static struct cdev ptmx_cdev; 604 605 /** 606 * ptm_open_peer - open the peer of a pty 607 * @master: the open struct file of the ptmx device node 608 * @tty: the master of the pty being opened 609 * @flags: the flags for open 610 * 611 * Provide a race free way for userspace to open the slave end of a pty 612 * (where they have the master fd and cannot access or trust the mount 613 * namespace /dev/pts was mounted inside). 614 */ 615 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags) 616 { 617 int fd = -1; 618 struct file *filp; 619 int retval = -EINVAL; 620 struct path path; 621 622 if (tty->driver != ptm_driver) 623 return -EIO; 624 625 fd = get_unused_fd_flags(0); 626 if (fd < 0) { 627 retval = fd; 628 goto err; 629 } 630 631 /* Compute the slave's path */ 632 path.mnt = devpts_mntget(master, tty->driver_data); 633 if (IS_ERR(path.mnt)) { 634 retval = PTR_ERR(path.mnt); 635 goto err_put; 636 } 637 path.dentry = tty->link->driver_data; 638 639 filp = dentry_open(&path, flags, current_cred()); 640 mntput(path.mnt); 641 if (IS_ERR(filp)) { 642 retval = PTR_ERR(filp); 643 goto err_put; 644 } 645 646 fd_install(fd, filp); 647 return fd; 648 649 err_put: 650 put_unused_fd(fd); 651 err: 652 return retval; 653 } 654 655 static int pty_unix98_ioctl(struct tty_struct *tty, 656 unsigned int cmd, unsigned long arg) 657 { 658 switch (cmd) { 659 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ 660 return pty_set_lock(tty, (int __user *)arg); 661 case TIOCGPTLCK: /* Get PT Lock status */ 662 return pty_get_lock(tty, (int __user *)arg); 663 case TIOCPKT: /* Set PT packet mode */ 664 return pty_set_pktmode(tty, (int __user *)arg); 665 case TIOCGPKT: /* Get PT packet mode */ 666 return pty_get_pktmode(tty, (int __user *)arg); 667 case TIOCGPTN: /* Get PT Number */ 668 return put_user(tty->index, (unsigned int __user *)arg); 669 case TIOCSIG: /* Send signal to other side of pty */ 670 return pty_signal(tty, (int) arg); 671 } 672 673 return -ENOIOCTLCMD; 674 } 675 676 static long pty_unix98_compat_ioctl(struct tty_struct *tty, 677 unsigned int cmd, unsigned long arg) 678 { 679 /* 680 * PTY ioctls don't require any special translation between 32-bit and 681 * 64-bit userspace, they are already compatible. 682 */ 683 return pty_unix98_ioctl(tty, cmd, arg); 684 } 685 686 /** 687 * ptm_unix98_lookup - find a pty master 688 * @driver: ptm driver 689 * @idx: tty index 690 * 691 * Look up a pty master device. Called under the tty_mutex for now. 692 * This provides our locking. 693 */ 694 695 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver, 696 struct file *file, int idx) 697 { 698 /* Master must be open via /dev/ptmx */ 699 return ERR_PTR(-EIO); 700 } 701 702 /** 703 * pts_unix98_lookup - find a pty slave 704 * @driver: pts driver 705 * @idx: tty index 706 * 707 * Look up a pty master device. Called under the tty_mutex for now. 708 * This provides our locking for the tty pointer. 709 */ 710 711 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver, 712 struct file *file, int idx) 713 { 714 struct tty_struct *tty; 715 716 mutex_lock(&devpts_mutex); 717 tty = devpts_get_priv(file->f_path.dentry); 718 mutex_unlock(&devpts_mutex); 719 /* Master must be open before slave */ 720 if (!tty) 721 return ERR_PTR(-EIO); 722 return tty; 723 } 724 725 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty) 726 { 727 return pty_common_install(driver, tty, false); 728 } 729 730 /* this is called once with whichever end is closed last */ 731 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty) 732 { 733 struct pts_fs_info *fsi; 734 735 if (tty->driver->subtype == PTY_TYPE_MASTER) 736 fsi = tty->driver_data; 737 else 738 fsi = tty->link->driver_data; 739 740 if (fsi) { 741 devpts_kill_index(fsi, tty->index); 742 devpts_release(fsi); 743 } 744 } 745 746 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m) 747 { 748 seq_printf(m, "tty-index:\t%d\n", tty->index); 749 } 750 751 static const struct tty_operations ptm_unix98_ops = { 752 .lookup = ptm_unix98_lookup, 753 .install = pty_unix98_install, 754 .remove = pty_unix98_remove, 755 .open = pty_open, 756 .close = pty_close, 757 .write = pty_write, 758 .write_room = pty_write_room, 759 .flush_buffer = pty_flush_buffer, 760 .chars_in_buffer = pty_chars_in_buffer, 761 .unthrottle = pty_unthrottle, 762 .ioctl = pty_unix98_ioctl, 763 .compat_ioctl = pty_unix98_compat_ioctl, 764 .resize = pty_resize, 765 .cleanup = pty_cleanup, 766 .show_fdinfo = pty_show_fdinfo, 767 }; 768 769 static const struct tty_operations pty_unix98_ops = { 770 .lookup = pts_unix98_lookup, 771 .install = pty_unix98_install, 772 .remove = pty_unix98_remove, 773 .open = pty_open, 774 .close = pty_close, 775 .write = pty_write, 776 .write_room = pty_write_room, 777 .flush_buffer = pty_flush_buffer, 778 .chars_in_buffer = pty_chars_in_buffer, 779 .unthrottle = pty_unthrottle, 780 .set_termios = pty_set_termios, 781 .start = pty_start, 782 .stop = pty_stop, 783 .cleanup = pty_cleanup, 784 }; 785 786 /** 787 * ptmx_open - open a unix 98 pty master 788 * @inode: inode of device file 789 * @filp: file pointer to tty 790 * 791 * Allocate a unix98 pty master device from the ptmx driver. 792 * 793 * Locking: tty_mutex protects the init_dev work. tty->count should 794 * protect the rest. 795 * allocated_ptys_lock handles the list of free pty numbers 796 */ 797 798 static int ptmx_open(struct inode *inode, struct file *filp) 799 { 800 struct pts_fs_info *fsi; 801 struct tty_struct *tty; 802 struct dentry *dentry; 803 int retval; 804 int index; 805 806 nonseekable_open(inode, filp); 807 808 /* We refuse fsnotify events on ptmx, since it's a shared resource */ 809 filp->f_mode |= FMODE_NONOTIFY; 810 811 retval = tty_alloc_file(filp); 812 if (retval) 813 return retval; 814 815 fsi = devpts_acquire(filp); 816 if (IS_ERR(fsi)) { 817 retval = PTR_ERR(fsi); 818 goto out_free_file; 819 } 820 821 /* find a device that is not in use. */ 822 mutex_lock(&devpts_mutex); 823 index = devpts_new_index(fsi); 824 mutex_unlock(&devpts_mutex); 825 826 retval = index; 827 if (index < 0) 828 goto out_put_fsi; 829 830 831 mutex_lock(&tty_mutex); 832 tty = tty_init_dev(ptm_driver, index); 833 /* The tty returned here is locked so we can safely 834 drop the mutex */ 835 mutex_unlock(&tty_mutex); 836 837 retval = PTR_ERR(tty); 838 if (IS_ERR(tty)) 839 goto out; 840 841 /* 842 * From here on out, the tty is "live", and the index and 843 * fsi will be killed/put by the tty_release() 844 */ 845 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */ 846 tty->driver_data = fsi; 847 848 tty_add_file(tty, filp); 849 850 dentry = devpts_pty_new(fsi, index, tty->link); 851 if (IS_ERR(dentry)) { 852 retval = PTR_ERR(dentry); 853 goto err_release; 854 } 855 tty->link->driver_data = dentry; 856 857 retval = ptm_driver->ops->open(tty, filp); 858 if (retval) 859 goto err_release; 860 861 tty_debug_hangup(tty, "opening (count=%d)\n", tty->count); 862 863 tty_unlock(tty); 864 return 0; 865 err_release: 866 tty_unlock(tty); 867 // This will also put-ref the fsi 868 tty_release(inode, filp); 869 return retval; 870 out: 871 devpts_kill_index(fsi, index); 872 out_put_fsi: 873 devpts_release(fsi); 874 out_free_file: 875 tty_free_file(filp); 876 return retval; 877 } 878 879 static struct file_operations ptmx_fops __ro_after_init; 880 881 static void __init unix98_pty_init(void) 882 { 883 ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX, 884 TTY_DRIVER_RESET_TERMIOS | 885 TTY_DRIVER_REAL_RAW | 886 TTY_DRIVER_DYNAMIC_DEV | 887 TTY_DRIVER_DEVPTS_MEM | 888 TTY_DRIVER_DYNAMIC_ALLOC); 889 if (IS_ERR(ptm_driver)) 890 panic("Couldn't allocate Unix98 ptm driver"); 891 pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX, 892 TTY_DRIVER_RESET_TERMIOS | 893 TTY_DRIVER_REAL_RAW | 894 TTY_DRIVER_DYNAMIC_DEV | 895 TTY_DRIVER_DEVPTS_MEM | 896 TTY_DRIVER_DYNAMIC_ALLOC); 897 if (IS_ERR(pts_driver)) 898 panic("Couldn't allocate Unix98 pts driver"); 899 900 ptm_driver->driver_name = "pty_master"; 901 ptm_driver->name = "ptm"; 902 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR; 903 ptm_driver->minor_start = 0; 904 ptm_driver->type = TTY_DRIVER_TYPE_PTY; 905 ptm_driver->subtype = PTY_TYPE_MASTER; 906 ptm_driver->init_termios = tty_std_termios; 907 ptm_driver->init_termios.c_iflag = 0; 908 ptm_driver->init_termios.c_oflag = 0; 909 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 910 ptm_driver->init_termios.c_lflag = 0; 911 ptm_driver->init_termios.c_ispeed = 38400; 912 ptm_driver->init_termios.c_ospeed = 38400; 913 ptm_driver->other = pts_driver; 914 tty_set_operations(ptm_driver, &ptm_unix98_ops); 915 916 pts_driver->driver_name = "pty_slave"; 917 pts_driver->name = "pts"; 918 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR; 919 pts_driver->minor_start = 0; 920 pts_driver->type = TTY_DRIVER_TYPE_PTY; 921 pts_driver->subtype = PTY_TYPE_SLAVE; 922 pts_driver->init_termios = tty_std_termios; 923 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 924 pts_driver->init_termios.c_ispeed = 38400; 925 pts_driver->init_termios.c_ospeed = 38400; 926 pts_driver->other = ptm_driver; 927 tty_set_operations(pts_driver, &pty_unix98_ops); 928 929 if (tty_register_driver(ptm_driver)) 930 panic("Couldn't register Unix98 ptm driver"); 931 if (tty_register_driver(pts_driver)) 932 panic("Couldn't register Unix98 pts driver"); 933 934 /* Now create the /dev/ptmx special device */ 935 tty_default_fops(&ptmx_fops); 936 ptmx_fops.open = ptmx_open; 937 938 cdev_init(&ptmx_cdev, &ptmx_fops); 939 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) || 940 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0) 941 panic("Couldn't register /dev/ptmx driver"); 942 device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx"); 943 } 944 945 #else 946 static inline void unix98_pty_init(void) { } 947 #endif 948 949 static int __init pty_init(void) 950 { 951 legacy_pty_init(); 952 unix98_pty_init(); 953 return 0; 954 } 955 device_initcall(pty_init); 956