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 ssize_t pty_write(struct tty_struct *tty, const u8 *buf, size_t c) 112 { 113 struct tty_struct *to = tty->link; 114 115 if (tty->flow.stopped || !c) 116 return 0; 117 118 return tty_insert_flip_string_and_push_buffer(to->port, buf, c); 119 } 120 121 /** 122 * pty_write_room - write space 123 * @tty: tty we are writing from 124 * 125 * Report how many bytes the ldisc can send into the queue for 126 * the other device. 127 */ 128 129 static unsigned int pty_write_room(struct tty_struct *tty) 130 { 131 if (tty->flow.stopped) 132 return 0; 133 return tty_buffer_space_avail(tty->link->port); 134 } 135 136 /* Set the lock flag on a pty */ 137 static int pty_set_lock(struct tty_struct *tty, int __user *arg) 138 { 139 int val; 140 141 if (get_user(val, arg)) 142 return -EFAULT; 143 if (val) 144 set_bit(TTY_PTY_LOCK, &tty->flags); 145 else 146 clear_bit(TTY_PTY_LOCK, &tty->flags); 147 return 0; 148 } 149 150 static int pty_get_lock(struct tty_struct *tty, int __user *arg) 151 { 152 int locked = test_bit(TTY_PTY_LOCK, &tty->flags); 153 154 return put_user(locked, arg); 155 } 156 157 /* Set the packet mode on a pty */ 158 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg) 159 { 160 int pktmode; 161 162 if (get_user(pktmode, arg)) 163 return -EFAULT; 164 165 spin_lock_irq(&tty->ctrl.lock); 166 if (pktmode) { 167 if (!tty->ctrl.packet) { 168 tty->link->ctrl.pktstatus = 0; 169 smp_mb(); 170 tty->ctrl.packet = true; 171 } 172 } else 173 tty->ctrl.packet = false; 174 spin_unlock_irq(&tty->ctrl.lock); 175 176 return 0; 177 } 178 179 /* Get the packet mode of a pty */ 180 static int pty_get_pktmode(struct tty_struct *tty, int __user *arg) 181 { 182 int pktmode = tty->ctrl.packet; 183 184 return put_user(pktmode, arg); 185 } 186 187 /* Send a signal to the slave */ 188 static int pty_signal(struct tty_struct *tty, int sig) 189 { 190 struct pid *pgrp; 191 192 if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP) 193 return -EINVAL; 194 195 if (tty->link) { 196 pgrp = tty_get_pgrp(tty->link); 197 if (pgrp) 198 kill_pgrp(pgrp, sig, 1); 199 put_pid(pgrp); 200 } 201 return 0; 202 } 203 204 static void pty_flush_buffer(struct tty_struct *tty) 205 { 206 struct tty_struct *to = tty->link; 207 208 if (!to) 209 return; 210 211 tty_buffer_flush(to, NULL); 212 if (to->ctrl.packet) { 213 spin_lock_irq(&tty->ctrl.lock); 214 tty->ctrl.pktstatus |= TIOCPKT_FLUSHWRITE; 215 wake_up_interruptible(&to->read_wait); 216 spin_unlock_irq(&tty->ctrl.lock); 217 } 218 } 219 220 static int pty_open(struct tty_struct *tty, struct file *filp) 221 { 222 if (!tty || !tty->link) 223 return -ENODEV; 224 225 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) 226 goto out; 227 if (test_bit(TTY_PTY_LOCK, &tty->link->flags)) 228 goto out; 229 if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1) 230 goto out; 231 232 clear_bit(TTY_IO_ERROR, &tty->flags); 233 clear_bit(TTY_OTHER_CLOSED, &tty->link->flags); 234 set_bit(TTY_THROTTLED, &tty->flags); 235 return 0; 236 237 out: 238 set_bit(TTY_IO_ERROR, &tty->flags); 239 return -EIO; 240 } 241 242 static void pty_set_termios(struct tty_struct *tty, 243 const struct ktermios *old_termios) 244 { 245 /* See if packet mode change of state. */ 246 if (tty->link && tty->link->ctrl.packet) { 247 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty); 248 int old_flow = ((old_termios->c_iflag & IXON) && 249 (old_termios->c_cc[VSTOP] == '\023') && 250 (old_termios->c_cc[VSTART] == '\021')); 251 int new_flow = (I_IXON(tty) && 252 STOP_CHAR(tty) == '\023' && 253 START_CHAR(tty) == '\021'); 254 if ((old_flow != new_flow) || extproc) { 255 spin_lock_irq(&tty->ctrl.lock); 256 if (old_flow != new_flow) { 257 tty->ctrl.pktstatus &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP); 258 if (new_flow) 259 tty->ctrl.pktstatus |= TIOCPKT_DOSTOP; 260 else 261 tty->ctrl.pktstatus |= TIOCPKT_NOSTOP; 262 } 263 if (extproc) 264 tty->ctrl.pktstatus |= TIOCPKT_IOCTL; 265 spin_unlock_irq(&tty->ctrl.lock); 266 wake_up_interruptible(&tty->link->read_wait); 267 } 268 } 269 270 tty->termios.c_cflag &= ~(CSIZE | PARENB); 271 tty->termios.c_cflag |= (CS8 | CREAD); 272 } 273 274 /** 275 * pty_resize - resize event 276 * @tty: tty being resized 277 * @ws: window size being set. 278 * 279 * Update the termios variables and send the necessary signals to 280 * peform a terminal resize correctly 281 */ 282 283 static int pty_resize(struct tty_struct *tty, struct winsize *ws) 284 { 285 struct pid *pgrp, *rpgrp; 286 struct tty_struct *pty = tty->link; 287 288 /* For a PTY we need to lock the tty side */ 289 mutex_lock(&tty->winsize_mutex); 290 if (!memcmp(ws, &tty->winsize, sizeof(*ws))) 291 goto done; 292 293 /* Signal the foreground process group of both ptys */ 294 pgrp = tty_get_pgrp(tty); 295 rpgrp = tty_get_pgrp(pty); 296 297 if (pgrp) 298 kill_pgrp(pgrp, SIGWINCH, 1); 299 if (rpgrp != pgrp && rpgrp) 300 kill_pgrp(rpgrp, SIGWINCH, 1); 301 302 put_pid(pgrp); 303 put_pid(rpgrp); 304 305 tty->winsize = *ws; 306 pty->winsize = *ws; /* Never used so will go away soon */ 307 done: 308 mutex_unlock(&tty->winsize_mutex); 309 return 0; 310 } 311 312 /** 313 * pty_start - start() handler 314 * pty_stop - stop() handler 315 * @tty: tty being flow-controlled 316 * 317 * Propagates the TIOCPKT status to the master pty. 318 * 319 * NB: only the master pty can be in packet mode so only the slave 320 * needs start()/stop() handlers 321 */ 322 static void pty_start(struct tty_struct *tty) 323 { 324 unsigned long flags; 325 326 if (tty->link && tty->link->ctrl.packet) { 327 spin_lock_irqsave(&tty->ctrl.lock, flags); 328 tty->ctrl.pktstatus &= ~TIOCPKT_STOP; 329 tty->ctrl.pktstatus |= TIOCPKT_START; 330 spin_unlock_irqrestore(&tty->ctrl.lock, flags); 331 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN); 332 } 333 } 334 335 static void pty_stop(struct tty_struct *tty) 336 { 337 unsigned long flags; 338 339 if (tty->link && tty->link->ctrl.packet) { 340 spin_lock_irqsave(&tty->ctrl.lock, flags); 341 tty->ctrl.pktstatus &= ~TIOCPKT_START; 342 tty->ctrl.pktstatus |= TIOCPKT_STOP; 343 spin_unlock_irqrestore(&tty->ctrl.lock, flags); 344 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN); 345 } 346 } 347 348 /** 349 * pty_common_install - set up the pty pair 350 * @driver: the pty driver 351 * @tty: the tty being instantiated 352 * @legacy: true if this is BSD style 353 * 354 * Perform the initial set up for the tty/pty pair. Called from the 355 * tty layer when the port is first opened. 356 * 357 * Locking: the caller must hold the tty_mutex 358 */ 359 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty, 360 bool legacy) 361 { 362 struct tty_struct *o_tty; 363 struct tty_port *ports[2]; 364 int idx = tty->index; 365 int retval = -ENOMEM; 366 367 /* Opening the slave first has always returned -EIO */ 368 if (driver->subtype != PTY_TYPE_MASTER) 369 return -EIO; 370 371 ports[0] = kmalloc(sizeof **ports, GFP_KERNEL); 372 ports[1] = kmalloc(sizeof **ports, GFP_KERNEL); 373 if (!ports[0] || !ports[1]) 374 goto err; 375 if (!try_module_get(driver->other->owner)) { 376 /* This cannot in fact currently happen */ 377 goto err; 378 } 379 o_tty = alloc_tty_struct(driver->other, idx); 380 if (!o_tty) 381 goto err_put_module; 382 383 tty_set_lock_subclass(o_tty); 384 lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE); 385 386 if (legacy) { 387 /* We always use new tty termios data so we can do this 388 the easy way .. */ 389 tty_init_termios(tty); 390 tty_init_termios(o_tty); 391 392 driver->other->ttys[idx] = o_tty; 393 driver->ttys[idx] = tty; 394 } else { 395 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked)); 396 tty->termios = driver->init_termios; 397 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked)); 398 o_tty->termios = driver->other->init_termios; 399 } 400 401 /* 402 * Everything allocated ... set up the o_tty structure. 403 */ 404 tty_driver_kref_get(driver->other); 405 /* Establish the links in both directions */ 406 tty->link = o_tty; 407 o_tty->link = tty; 408 tty_port_init(ports[0]); 409 tty_port_init(ports[1]); 410 tty_buffer_set_limit(ports[0], 8192); 411 tty_buffer_set_limit(ports[1], 8192); 412 o_tty->port = ports[0]; 413 tty->port = ports[1]; 414 o_tty->port->itty = o_tty; 415 416 tty_buffer_set_lock_subclass(o_tty->port); 417 418 tty_driver_kref_get(driver); 419 tty->count++; 420 o_tty->count++; 421 return 0; 422 423 err_put_module: 424 module_put(driver->other->owner); 425 err: 426 kfree(ports[0]); 427 kfree(ports[1]); 428 return retval; 429 } 430 431 static void pty_cleanup(struct tty_struct *tty) 432 { 433 tty_port_put(tty->port); 434 } 435 436 /* Traditional BSD devices */ 437 #ifdef CONFIG_LEGACY_PTYS 438 439 static int pty_install(struct tty_driver *driver, struct tty_struct *tty) 440 { 441 return pty_common_install(driver, tty, true); 442 } 443 444 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty) 445 { 446 struct tty_struct *pair = tty->link; 447 448 driver->ttys[tty->index] = NULL; 449 if (pair) 450 pair->driver->ttys[pair->index] = NULL; 451 } 452 453 static int pty_bsd_ioctl(struct tty_struct *tty, 454 unsigned int cmd, unsigned long arg) 455 { 456 switch (cmd) { 457 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ 458 return pty_set_lock(tty, (int __user *) arg); 459 case TIOCGPTLCK: /* Get PT Lock status */ 460 return pty_get_lock(tty, (int __user *)arg); 461 case TIOCPKT: /* Set PT packet mode */ 462 return pty_set_pktmode(tty, (int __user *)arg); 463 case TIOCGPKT: /* Get PT packet mode */ 464 return pty_get_pktmode(tty, (int __user *)arg); 465 case TIOCSIG: /* Send signal to other side of pty */ 466 return pty_signal(tty, (int) arg); 467 case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */ 468 return -EINVAL; 469 } 470 return -ENOIOCTLCMD; 471 } 472 473 #ifdef CONFIG_COMPAT 474 static long pty_bsd_compat_ioctl(struct tty_struct *tty, 475 unsigned int cmd, unsigned long arg) 476 { 477 /* 478 * PTY ioctls don't require any special translation between 32-bit and 479 * 64-bit userspace, they are already compatible. 480 */ 481 return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg)); 482 } 483 #else 484 #define pty_bsd_compat_ioctl NULL 485 #endif 486 487 static int legacy_count = CONFIG_LEGACY_PTY_COUNT; 488 /* 489 * not really modular, but the easiest way to keep compat with existing 490 * bootargs behaviour is to continue using module_param here. 491 */ 492 module_param(legacy_count, int, 0); 493 494 /* 495 * The master side of a pty can do TIOCSPTLCK and thus 496 * has pty_bsd_ioctl. 497 */ 498 static const struct tty_operations master_pty_ops_bsd = { 499 .install = pty_install, 500 .open = pty_open, 501 .close = pty_close, 502 .write = pty_write, 503 .write_room = pty_write_room, 504 .flush_buffer = pty_flush_buffer, 505 .unthrottle = pty_unthrottle, 506 .ioctl = pty_bsd_ioctl, 507 .compat_ioctl = pty_bsd_compat_ioctl, 508 .cleanup = pty_cleanup, 509 .resize = pty_resize, 510 .remove = pty_remove 511 }; 512 513 static const struct tty_operations slave_pty_ops_bsd = { 514 .install = pty_install, 515 .open = pty_open, 516 .close = pty_close, 517 .write = pty_write, 518 .write_room = pty_write_room, 519 .flush_buffer = pty_flush_buffer, 520 .unthrottle = pty_unthrottle, 521 .set_termios = pty_set_termios, 522 .cleanup = pty_cleanup, 523 .resize = pty_resize, 524 .start = pty_start, 525 .stop = pty_stop, 526 .remove = pty_remove 527 }; 528 529 static void __init legacy_pty_init(void) 530 { 531 struct tty_driver *pty_driver, *pty_slave_driver; 532 533 if (legacy_count <= 0) 534 return; 535 536 pty_driver = tty_alloc_driver(legacy_count, 537 TTY_DRIVER_RESET_TERMIOS | 538 TTY_DRIVER_REAL_RAW | 539 TTY_DRIVER_DYNAMIC_ALLOC); 540 if (IS_ERR(pty_driver)) 541 panic("Couldn't allocate pty driver"); 542 543 pty_slave_driver = tty_alloc_driver(legacy_count, 544 TTY_DRIVER_RESET_TERMIOS | 545 TTY_DRIVER_REAL_RAW | 546 TTY_DRIVER_DYNAMIC_ALLOC); 547 if (IS_ERR(pty_slave_driver)) 548 panic("Couldn't allocate pty slave driver"); 549 550 pty_driver->driver_name = "pty_master"; 551 pty_driver->name = "pty"; 552 pty_driver->major = PTY_MASTER_MAJOR; 553 pty_driver->minor_start = 0; 554 pty_driver->type = TTY_DRIVER_TYPE_PTY; 555 pty_driver->subtype = PTY_TYPE_MASTER; 556 pty_driver->init_termios = tty_std_termios; 557 pty_driver->init_termios.c_iflag = 0; 558 pty_driver->init_termios.c_oflag = 0; 559 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 560 pty_driver->init_termios.c_lflag = 0; 561 pty_driver->init_termios.c_ispeed = 38400; 562 pty_driver->init_termios.c_ospeed = 38400; 563 pty_driver->other = pty_slave_driver; 564 tty_set_operations(pty_driver, &master_pty_ops_bsd); 565 566 pty_slave_driver->driver_name = "pty_slave"; 567 pty_slave_driver->name = "ttyp"; 568 pty_slave_driver->major = PTY_SLAVE_MAJOR; 569 pty_slave_driver->minor_start = 0; 570 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY; 571 pty_slave_driver->subtype = PTY_TYPE_SLAVE; 572 pty_slave_driver->init_termios = tty_std_termios; 573 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 574 pty_slave_driver->init_termios.c_ispeed = 38400; 575 pty_slave_driver->init_termios.c_ospeed = 38400; 576 pty_slave_driver->other = pty_driver; 577 tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd); 578 579 if (tty_register_driver(pty_driver)) 580 panic("Couldn't register pty driver"); 581 if (tty_register_driver(pty_slave_driver)) 582 panic("Couldn't register pty slave driver"); 583 } 584 #else 585 static inline void legacy_pty_init(void) { } 586 #endif 587 588 /* Unix98 devices */ 589 #ifdef CONFIG_UNIX98_PTYS 590 static struct cdev ptmx_cdev; 591 592 /** 593 * ptm_open_peer - open the peer of a pty 594 * @master: the open struct file of the ptmx device node 595 * @tty: the master of the pty being opened 596 * @flags: the flags for open 597 * 598 * Provide a race free way for userspace to open the slave end of a pty 599 * (where they have the master fd and cannot access or trust the mount 600 * namespace /dev/pts was mounted inside). 601 */ 602 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags) 603 { 604 int fd; 605 struct file *filp; 606 int retval = -EINVAL; 607 struct path path; 608 609 if (tty->driver != ptm_driver) 610 return -EIO; 611 612 fd = get_unused_fd_flags(flags); 613 if (fd < 0) { 614 retval = fd; 615 goto err; 616 } 617 618 /* Compute the slave's path */ 619 path.mnt = devpts_mntget(master, tty->driver_data); 620 if (IS_ERR(path.mnt)) { 621 retval = PTR_ERR(path.mnt); 622 goto err_put; 623 } 624 path.dentry = tty->link->driver_data; 625 626 filp = dentry_open(&path, flags, current_cred()); 627 mntput(path.mnt); 628 if (IS_ERR(filp)) { 629 retval = PTR_ERR(filp); 630 goto err_put; 631 } 632 633 fd_install(fd, filp); 634 return fd; 635 636 err_put: 637 put_unused_fd(fd); 638 err: 639 return retval; 640 } 641 642 static int pty_unix98_ioctl(struct tty_struct *tty, 643 unsigned int cmd, unsigned long arg) 644 { 645 switch (cmd) { 646 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ 647 return pty_set_lock(tty, (int __user *)arg); 648 case TIOCGPTLCK: /* Get PT Lock status */ 649 return pty_get_lock(tty, (int __user *)arg); 650 case TIOCPKT: /* Set PT packet mode */ 651 return pty_set_pktmode(tty, (int __user *)arg); 652 case TIOCGPKT: /* Get PT packet mode */ 653 return pty_get_pktmode(tty, (int __user *)arg); 654 case TIOCGPTN: /* Get PT Number */ 655 return put_user(tty->index, (unsigned int __user *)arg); 656 case TIOCSIG: /* Send signal to other side of pty */ 657 return pty_signal(tty, (int) arg); 658 } 659 660 return -ENOIOCTLCMD; 661 } 662 663 #ifdef CONFIG_COMPAT 664 static long pty_unix98_compat_ioctl(struct tty_struct *tty, 665 unsigned int cmd, unsigned long arg) 666 { 667 /* 668 * PTY ioctls don't require any special translation between 32-bit and 669 * 64-bit userspace, they are already compatible. 670 */ 671 return pty_unix98_ioctl(tty, cmd, 672 cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg)); 673 } 674 #else 675 #define pty_unix98_compat_ioctl NULL 676 #endif 677 678 /** 679 * ptm_unix98_lookup - find a pty master 680 * @driver: ptm driver 681 * @file: unused 682 * @idx: tty index 683 * 684 * Look up a pty master device. Called under the tty_mutex for now. 685 * This provides our locking. 686 */ 687 688 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver, 689 struct file *file, int idx) 690 { 691 /* Master must be open via /dev/ptmx */ 692 return ERR_PTR(-EIO); 693 } 694 695 /** 696 * pts_unix98_lookup - find a pty slave 697 * @driver: pts driver 698 * @file: file pointer to tty 699 * @idx: tty index 700 * 701 * Look up a pty master device. Called under the tty_mutex for now. 702 * This provides our locking for the tty pointer. 703 */ 704 705 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver, 706 struct file *file, int idx) 707 { 708 struct tty_struct *tty; 709 710 mutex_lock(&devpts_mutex); 711 tty = devpts_get_priv(file->f_path.dentry); 712 mutex_unlock(&devpts_mutex); 713 /* Master must be open before slave */ 714 if (!tty) 715 return ERR_PTR(-EIO); 716 return tty; 717 } 718 719 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty) 720 { 721 return pty_common_install(driver, tty, false); 722 } 723 724 /* this is called once with whichever end is closed last */ 725 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty) 726 { 727 struct pts_fs_info *fsi; 728 729 if (tty->driver->subtype == PTY_TYPE_MASTER) 730 fsi = tty->driver_data; 731 else 732 fsi = tty->link->driver_data; 733 734 if (fsi) { 735 devpts_kill_index(fsi, tty->index); 736 devpts_release(fsi); 737 } 738 } 739 740 static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m) 741 { 742 seq_printf(m, "tty-index:\t%d\n", tty->index); 743 } 744 745 static const struct tty_operations ptm_unix98_ops = { 746 .lookup = ptm_unix98_lookup, 747 .install = pty_unix98_install, 748 .remove = pty_unix98_remove, 749 .open = pty_open, 750 .close = pty_close, 751 .write = pty_write, 752 .write_room = pty_write_room, 753 .flush_buffer = pty_flush_buffer, 754 .unthrottle = pty_unthrottle, 755 .ioctl = pty_unix98_ioctl, 756 .compat_ioctl = pty_unix98_compat_ioctl, 757 .resize = pty_resize, 758 .cleanup = pty_cleanup, 759 .show_fdinfo = pty_show_fdinfo, 760 }; 761 762 static const struct tty_operations pty_unix98_ops = { 763 .lookup = pts_unix98_lookup, 764 .install = pty_unix98_install, 765 .remove = pty_unix98_remove, 766 .open = pty_open, 767 .close = pty_close, 768 .write = pty_write, 769 .write_room = pty_write_room, 770 .flush_buffer = pty_flush_buffer, 771 .unthrottle = pty_unthrottle, 772 .set_termios = pty_set_termios, 773 .start = pty_start, 774 .stop = pty_stop, 775 .cleanup = pty_cleanup, 776 }; 777 778 /** 779 * ptmx_open - open a unix 98 pty master 780 * @inode: inode of device file 781 * @filp: file pointer to tty 782 * 783 * Allocate a unix98 pty master device from the ptmx driver. 784 * 785 * Locking: tty_mutex protects the init_dev work. tty->count should 786 * protect the rest. 787 * allocated_ptys_lock handles the list of free pty numbers 788 */ 789 790 static int ptmx_open(struct inode *inode, struct file *filp) 791 { 792 struct pts_fs_info *fsi; 793 struct tty_struct *tty; 794 struct dentry *dentry; 795 int retval; 796 int index; 797 798 nonseekable_open(inode, filp); 799 800 /* We refuse fsnotify events on ptmx, since it's a shared resource */ 801 filp->f_mode |= FMODE_NONOTIFY; 802 803 retval = tty_alloc_file(filp); 804 if (retval) 805 return retval; 806 807 fsi = devpts_acquire(filp); 808 if (IS_ERR(fsi)) { 809 retval = PTR_ERR(fsi); 810 goto out_free_file; 811 } 812 813 /* find a device that is not in use. */ 814 mutex_lock(&devpts_mutex); 815 index = devpts_new_index(fsi); 816 mutex_unlock(&devpts_mutex); 817 818 retval = index; 819 if (index < 0) 820 goto out_put_fsi; 821 822 823 mutex_lock(&tty_mutex); 824 tty = tty_init_dev(ptm_driver, index); 825 /* The tty returned here is locked so we can safely 826 drop the mutex */ 827 mutex_unlock(&tty_mutex); 828 829 retval = PTR_ERR(tty); 830 if (IS_ERR(tty)) 831 goto out; 832 833 /* 834 * From here on out, the tty is "live", and the index and 835 * fsi will be killed/put by the tty_release() 836 */ 837 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */ 838 tty->driver_data = fsi; 839 840 tty_add_file(tty, filp); 841 842 dentry = devpts_pty_new(fsi, index, tty->link); 843 if (IS_ERR(dentry)) { 844 retval = PTR_ERR(dentry); 845 goto err_release; 846 } 847 tty->link->driver_data = dentry; 848 849 retval = ptm_driver->ops->open(tty, filp); 850 if (retval) 851 goto err_release; 852 853 tty_debug_hangup(tty, "opening (count=%d)\n", tty->count); 854 855 tty_unlock(tty); 856 return 0; 857 err_release: 858 tty_unlock(tty); 859 // This will also put-ref the fsi 860 tty_release(inode, filp); 861 return retval; 862 out: 863 devpts_kill_index(fsi, index); 864 out_put_fsi: 865 devpts_release(fsi); 866 out_free_file: 867 tty_free_file(filp); 868 return retval; 869 } 870 871 static struct file_operations ptmx_fops __ro_after_init; 872 873 static void __init unix98_pty_init(void) 874 { 875 ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX, 876 TTY_DRIVER_RESET_TERMIOS | 877 TTY_DRIVER_REAL_RAW | 878 TTY_DRIVER_DYNAMIC_DEV | 879 TTY_DRIVER_DEVPTS_MEM | 880 TTY_DRIVER_DYNAMIC_ALLOC); 881 if (IS_ERR(ptm_driver)) 882 panic("Couldn't allocate Unix98 ptm driver"); 883 pts_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(pts_driver)) 890 panic("Couldn't allocate Unix98 pts driver"); 891 892 ptm_driver->driver_name = "pty_master"; 893 ptm_driver->name = "ptm"; 894 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR; 895 ptm_driver->minor_start = 0; 896 ptm_driver->type = TTY_DRIVER_TYPE_PTY; 897 ptm_driver->subtype = PTY_TYPE_MASTER; 898 ptm_driver->init_termios = tty_std_termios; 899 ptm_driver->init_termios.c_iflag = 0; 900 ptm_driver->init_termios.c_oflag = 0; 901 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 902 ptm_driver->init_termios.c_lflag = 0; 903 ptm_driver->init_termios.c_ispeed = 38400; 904 ptm_driver->init_termios.c_ospeed = 38400; 905 ptm_driver->other = pts_driver; 906 tty_set_operations(ptm_driver, &ptm_unix98_ops); 907 908 pts_driver->driver_name = "pty_slave"; 909 pts_driver->name = "pts"; 910 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR; 911 pts_driver->minor_start = 0; 912 pts_driver->type = TTY_DRIVER_TYPE_PTY; 913 pts_driver->subtype = PTY_TYPE_SLAVE; 914 pts_driver->init_termios = tty_std_termios; 915 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; 916 pts_driver->init_termios.c_ispeed = 38400; 917 pts_driver->init_termios.c_ospeed = 38400; 918 pts_driver->other = ptm_driver; 919 tty_set_operations(pts_driver, &pty_unix98_ops); 920 921 if (tty_register_driver(ptm_driver)) 922 panic("Couldn't register Unix98 ptm driver"); 923 if (tty_register_driver(pts_driver)) 924 panic("Couldn't register Unix98 pts driver"); 925 926 /* Now create the /dev/ptmx special device */ 927 tty_default_fops(&ptmx_fops); 928 ptmx_fops.open = ptmx_open; 929 930 cdev_init(&ptmx_cdev, &ptmx_fops); 931 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) || 932 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0) 933 panic("Couldn't register /dev/ptmx driver"); 934 device_create(&tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx"); 935 } 936 937 #else 938 static inline void unix98_pty_init(void) { } 939 #endif 940 941 static int __init pty_init(void) 942 { 943 legacy_pty_init(); 944 unix98_pty_init(); 945 return 0; 946 } 947 device_initcall(pty_init); 948