tty_io.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  Copyright (C) 1991, 1992  Linus Torvalds
   4 */
   5
   6/*
   7 * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
   8 * or rs-channels. It also implements echoing, cooked mode etc.
   9 *
  10 * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
  11 *
  12 * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
  13 * tty_struct and tty_queue structures.  Previously there was an array
  14 * of 256 tty_struct's which was statically allocated, and the
  15 * tty_queue structures were allocated at boot time.  Both are now
  16 * dynamically allocated only when the tty is open.
  17 *
  18 * Also restructured routines so that there is more of a separation
  19 * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
  20 * the low-level tty routines (serial.c, pty.c, console.c).  This
  21 * makes for cleaner and more compact code.  -TYT, 9/17/92
  22 *
  23 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
  24 * which can be dynamically activated and de-activated by the line
  25 * discipline handling modules (like SLIP).
  26 *
  27 * NOTE: pay no attention to the line discipline code (yet); its
  28 * interface is still subject to change in this version...
  29 * -- TYT, 1/31/92
  30 *
  31 * Added functionality to the OPOST tty handling.  No delays, but all
  32 * other bits should be there.
  33 *	-- Nick Holloway <alfie@dcs.warwick.ac.uk>, 27th May 1993.
  34 *
  35 * Rewrote canonical mode and added more termios flags.
  36 *	-- julian@uhunix.uhcc.hawaii.edu (J. Cowley), 13Jan94
  37 *
  38 * Reorganized FASYNC support so mouse code can share it.
  39 *	-- ctm@ardi.com, 9Sep95
  40 *
  41 * New TIOCLINUX variants added.
  42 *	-- mj@k332.feld.cvut.cz, 19-Nov-95
  43 *
  44 * Restrict vt switching via ioctl()
  45 *      -- grif@cs.ucr.edu, 5-Dec-95
  46 *
  47 * Move console and virtual terminal code to more appropriate files,
  48 * implement CONFIG_VT and generalize console device interface.
  49 *	-- Marko Kohtala <Marko.Kohtala@hut.fi>, March 97
  50 *
  51 * Rewrote tty_init_dev and tty_release_dev to eliminate races.
  52 *	-- Bill Hawes <whawes@star.net>, June 97
  53 *
  54 * Added devfs support.
  55 *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 13-Jan-1998
  56 *
  57 * Added support for a Unix98-style ptmx device.
  58 *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
  59 *
  60 * Reduced memory usage for older ARM systems
  61 *      -- Russell King <rmk@arm.linux.org.uk>
  62 *
  63 * Move do_SAK() into process context.  Less stack use in devfs functions.
  64 * alloc_tty_struct() always uses kmalloc()
  65 *			 -- Andrew Morton <andrewm@uow.edu.eu> 17Mar01
  66 */
  67
  68#include <linux/types.h>
  69#include <linux/major.h>
  70#include <linux/errno.h>
  71#include <linux/signal.h>
  72#include <linux/fcntl.h>
  73#include <linux/sched/signal.h>
  74#include <linux/sched/task.h>
  75#include <linux/interrupt.h>
  76#include <linux/tty.h>
  77#include <linux/tty_driver.h>
  78#include <linux/tty_flip.h>
  79#include <linux/devpts_fs.h>
  80#include <linux/file.h>
  81#include <linux/fdtable.h>
  82#include <linux/console.h>
  83#include <linux/timer.h>
  84#include <linux/ctype.h>
  85#include <linux/kd.h>
  86#include <linux/mm.h>
  87#include <linux/string.h>
  88#include <linux/slab.h>
  89#include <linux/poll.h>
  90#include <linux/ppp-ioctl.h>
  91#include <linux/proc_fs.h>
  92#include <linux/init.h>
  93#include <linux/module.h>
  94#include <linux/device.h>
  95#include <linux/wait.h>
  96#include <linux/bitops.h>
  97#include <linux/delay.h>
  98#include <linux/seq_file.h>
  99#include <linux/serial.h>
 100#include <linux/ratelimit.h>
 101#include <linux/compat.h>
 102#include <linux/uaccess.h>
 103#include <linux/termios_internal.h>
 104#include <linux/fs.h>
 105
 106#include <linux/kbd_kern.h>
 107#include <linux/vt_kern.h>
 108#include <linux/selection.h>
 109
 110#include <linux/kmod.h>
 111#include <linux/nsproxy.h>
 112#include "tty.h"
 113
 114#undef TTY_DEBUG_HANGUP
 115#ifdef TTY_DEBUG_HANGUP
 116# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)
 117#else
 118# define tty_debug_hangup(tty, f, args...)	do { } while (0)
 119#endif
 120
 121#define TTY_PARANOIA_CHECK 1
 122#define CHECK_TTY_COUNT 1
 123
 124struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
 125	.c_iflag = ICRNL | IXON,
 126	.c_oflag = OPOST | ONLCR,
 127	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
 128	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
 129		   ECHOCTL | ECHOKE | IEXTEN,
 130	.c_cc = INIT_C_CC,
 131	.c_ispeed = 38400,
 132	.c_ospeed = 38400,
 133	/* .c_line = N_TTY, */
 134};
 135EXPORT_SYMBOL(tty_std_termios);
 136
 137/* This list gets poked at by procfs and various bits of boot up code. This
 138 * could do with some rationalisation such as pulling the tty proc function
 139 * into this file.
 140 */
 141
 142LIST_HEAD(tty_drivers);			/* linked list of tty drivers */
 143
 144/* Mutex to protect creating and releasing a tty */
 145DEFINE_MUTEX(tty_mutex);
 146
 147static ssize_t tty_read(struct kiocb *, struct iov_iter *);
 148static ssize_t tty_write(struct kiocb *, struct iov_iter *);
 149static __poll_t tty_poll(struct file *, poll_table *);
 150static int tty_open(struct inode *, struct file *);
 151#ifdef CONFIG_COMPAT
 152static long tty_compat_ioctl(struct file *file, unsigned int cmd,
 153				unsigned long arg);
 154#else
 155#define tty_compat_ioctl NULL
 156#endif
 157static int __tty_fasync(int fd, struct file *filp, int on);
 158static int tty_fasync(int fd, struct file *filp, int on);
 159static void release_tty(struct tty_struct *tty, int idx);
 160
 161/**
 162 * free_tty_struct - free a disused tty
 163 * @tty: tty struct to free
 164 *
 165 * Free the write buffers, tty queue and tty memory itself.
 166 *
 167 * Locking: none. Must be called after tty is definitely unused
 168 */
 169static void free_tty_struct(struct tty_struct *tty)
 170{
 171	tty_ldisc_deinit(tty);
 172	put_device(tty->dev);
 173	kvfree(tty->write_buf);
 174	kfree(tty);
 175}
 176
 177static inline struct tty_struct *file_tty(struct file *file)
 178{
 179	return ((struct tty_file_private *)file->private_data)->tty;
 180}
 181
 182int tty_alloc_file(struct file *file)
 183{
 184	struct tty_file_private *priv;
 185
 186	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
 187	if (!priv)
 188		return -ENOMEM;
 189
 190	file->private_data = priv;
 191
 192	return 0;
 193}
 194
 195/* Associate a new file with the tty structure */
 196void tty_add_file(struct tty_struct *tty, struct file *file)
 197{
 198	struct tty_file_private *priv = file->private_data;
 199
 200	priv->tty = tty;
 201	priv->file = file;
 202
 203	spin_lock(&tty->files_lock);
 204	list_add(&priv->list, &tty->tty_files);
 205	spin_unlock(&tty->files_lock);
 206}
 207
 208/**
 209 * tty_free_file - free file->private_data
 210 * @file: to free private_data of
 211 *
 212 * This shall be used only for fail path handling when tty_add_file was not
 213 * called yet.
 214 */
 215void tty_free_file(struct file *file)
 216{
 217	struct tty_file_private *priv = file->private_data;
 218
 219	file->private_data = NULL;
 220	kfree(priv);
 221}
 222
 223/* Delete file from its tty */
 224static void tty_del_file(struct file *file)
 225{
 226	struct tty_file_private *priv = file->private_data;
 227	struct tty_struct *tty = priv->tty;
 228
 229	spin_lock(&tty->files_lock);
 230	list_del(&priv->list);
 231	spin_unlock(&tty->files_lock);
 232	tty_free_file(file);
 233}
 234
 235/**
 236 * tty_name - return tty naming
 237 * @tty: tty structure
 238 *
 239 * Convert a tty structure into a name. The name reflects the kernel naming
 240 * policy and if udev is in use may not reflect user space
 241 *
 242 * Locking: none
 243 */
 244const char *tty_name(const struct tty_struct *tty)
 245{
 246	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
 247		return "NULL tty";
 248	return tty->name;
 249}
 250EXPORT_SYMBOL(tty_name);
 251
 252const char *tty_driver_name(const struct tty_struct *tty)
 253{
 254	if (!tty || !tty->driver)
 255		return "";
 256	return tty->driver->name;
 257}
 258
 259static int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
 260			      const char *routine)
 261{
 262#ifdef TTY_PARANOIA_CHECK
 263	if (!tty) {
 264		pr_warn("(%d:%d): %s: NULL tty\n",
 265			imajor(inode), iminor(inode), routine);
 266		return 1;
 267	}
 268#endif
 269	return 0;
 270}
 271
 272/* Caller must hold tty_lock */
 273static void check_tty_count(struct tty_struct *tty, const char *routine)
 274{
 275#ifdef CHECK_TTY_COUNT
 276	struct list_head *p;
 277	int count = 0, kopen_count = 0;
 278
 279	scoped_guard(spinlock, &tty->files_lock)
 280		list_for_each(p, &tty->tty_files)
 281			count++;
 282
 283	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
 284	    tty->driver->subtype == PTY_TYPE_SLAVE &&
 285	    tty->link && tty->link->count)
 286		count++;
 287	if (tty_port_kopened(tty->port))
 288		kopen_count++;
 289	if (tty->count != (count + kopen_count)) {
 290		tty_warn(tty, "%s: tty->count(%d) != (#fd's(%d) + #kopen's(%d))\n",
 291			 routine, tty->count, count, kopen_count);
 292	}
 293#endif
 294}
 295
 296/**
 297 * get_tty_driver - find device of a tty
 298 * @device: device identifier
 299 * @index: returns the index of the tty
 300 *
 301 * This routine returns a tty driver structure, given a device number and also
 302 * passes back the index number.
 303 *
 304 * Locking: caller must hold tty_mutex
 305 */
 306static struct tty_driver *get_tty_driver(dev_t device, int *index)
 307{
 308	struct tty_driver *p;
 309
 310	list_for_each_entry(p, &tty_drivers, tty_drivers) {
 311		dev_t base = MKDEV(p->major, p->minor_start);
 312
 313		if (device < base || device >= base + p->num)
 314			continue;
 315		*index = device - base;
 316		return tty_driver_kref_get(p);
 317	}
 318	return NULL;
 319}
 320
 321/**
 322 * tty_dev_name_to_number - return dev_t for device name
 323 * @name: user space name of device under /dev
 324 * @number: pointer to dev_t that this function will populate
 325 *
 326 * This function converts device names like ttyS0 or ttyUSB1 into dev_t like
 327 * (4, 64) or (188, 1). If no corresponding driver is registered then the
 328 * function returns -%ENODEV.
 329 *
 330 * Locking: this acquires tty_mutex to protect the tty_drivers list from
 331 *	being modified while we are traversing it, and makes sure to
 332 *	release it before exiting.
 333 */
 334int tty_dev_name_to_number(const char *name, dev_t *number)
 335{
 336	struct tty_driver *p;
 337	int ret;
 338	int index, prefix_length = 0;
 339	const char *str;
 340
 341	for (str = name; *str && !isdigit(*str); str++)
 342		;
 343
 344	if (!*str)
 345		return -EINVAL;
 346
 347	ret = kstrtoint(str, 10, &index);
 348	if (ret)
 349		return ret;
 350
 351	prefix_length = str - name;
 352
 353	guard(mutex)(&tty_mutex);
 354
 355	list_for_each_entry(p, &tty_drivers, tty_drivers)
 356		if (prefix_length == strlen(p->name) && strncmp(name,
 357					p->name, prefix_length) == 0) {
 358			if (index < p->num) {
 359				*number = MKDEV(p->major, p->minor_start + index);
 360				return 0;
 361			}
 362		}
 363
 364	return -ENODEV;
 365}
 366EXPORT_SYMBOL_GPL(tty_dev_name_to_number);
 367
 368#ifdef CONFIG_CONSOLE_POLL
 369
 370/**
 371 * tty_find_polling_driver - find device of a polled tty
 372 * @name: name string to match
 373 * @line: pointer to resulting tty line nr
 374 *
 375 * This routine returns a tty driver structure, given a name and the condition
 376 * that the tty driver is capable of polled operation.
 377 */
 378struct tty_driver *tty_find_polling_driver(char *name, int *line)
 379{
 380	struct tty_driver *p;
 381	int tty_line = 0;
 382	int len;
 383	char *str, *stp;
 384
 385	for (str = name; *str; str++)
 386		if ((*str >= '0' && *str <= '9') || *str == ',')
 387			break;
 388	if (!*str)
 389		return NULL;
 390
 391	len = str - name;
 392	tty_line = simple_strtoul(str, &str, 10);
 393
 394	guard(mutex)(&tty_mutex);
 395
 396	/* Search through the tty devices to look for a match */
 397	list_for_each_entry(p, &tty_drivers, tty_drivers) {
 398		if (!len || strncmp(name, p->name, len) != 0)
 399			continue;
 400		stp = str;
 401		if (*stp == ',')
 402			stp++;
 403		if (*stp == '\0')
 404			stp = NULL;
 405
 406		if (tty_line >= 0 && tty_line < p->num && p->ops &&
 407		    p->ops->poll_init && !p->ops->poll_init(p, tty_line, stp)) {
 408			*line = tty_line;
 409			return tty_driver_kref_get(p);
 410		}
 411	}
 412
 413	return NULL;
 414}
 415EXPORT_SYMBOL_GPL(tty_find_polling_driver);
 416#endif
 417
 418static ssize_t hung_up_tty_read(struct kiocb *iocb, struct iov_iter *to)
 419{
 420	return 0;
 421}
 422
 423static ssize_t hung_up_tty_write(struct kiocb *iocb, struct iov_iter *from)
 424{
 425	return -EIO;
 426}
 427
 428/* No kernel lock held - none needed ;) */
 429static __poll_t hung_up_tty_poll(struct file *filp, poll_table *wait)
 430{
 431	return EPOLLIN | EPOLLOUT | EPOLLERR | EPOLLHUP | EPOLLRDNORM | EPOLLWRNORM;
 432}
 433
 434static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
 435		unsigned long arg)
 436{
 437	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
 438}
 439
 440static long hung_up_tty_compat_ioctl(struct file *file,
 441				     unsigned int cmd, unsigned long arg)
 442{
 443	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
 444}
 445
 446static int hung_up_tty_fasync(int fd, struct file *file, int on)
 447{
 448	return -ENOTTY;
 449}
 450
 451static void tty_show_fdinfo(struct seq_file *m, struct file *file)
 452{
 453	struct tty_struct *tty = file_tty(file);
 454
 455	if (tty && tty->ops && tty->ops->show_fdinfo)
 456		tty->ops->show_fdinfo(tty, m);
 457}
 458
 459static const struct file_operations tty_fops = {
 460	.read_iter	= tty_read,
 461	.write_iter	= tty_write,
 462	.splice_read	= copy_splice_read,
 463	.splice_write	= iter_file_splice_write,
 464	.poll		= tty_poll,
 465	.unlocked_ioctl	= tty_ioctl,
 466	.compat_ioctl	= tty_compat_ioctl,
 467	.open		= tty_open,
 468	.release	= tty_release,
 469	.fasync		= tty_fasync,
 470	.show_fdinfo	= tty_show_fdinfo,
 471};
 472
 473static const struct file_operations console_fops = {
 474	.read_iter	= tty_read,
 475	.write_iter	= redirected_tty_write,
 476	.splice_read	= copy_splice_read,
 477	.splice_write	= iter_file_splice_write,
 478	.poll		= tty_poll,
 479	.unlocked_ioctl	= tty_ioctl,
 480	.compat_ioctl	= tty_compat_ioctl,
 481	.open		= tty_open,
 482	.release	= tty_release,
 483	.fasync		= tty_fasync,
 484};
 485
 486static const struct file_operations hung_up_tty_fops = {
 487	.read_iter	= hung_up_tty_read,
 488	.write_iter	= hung_up_tty_write,
 489	.poll		= hung_up_tty_poll,
 490	.unlocked_ioctl	= hung_up_tty_ioctl,
 491	.compat_ioctl	= hung_up_tty_compat_ioctl,
 492	.release	= tty_release,
 493	.fasync		= hung_up_tty_fasync,
 494};
 495
 496static DEFINE_SPINLOCK(redirect_lock);
 497static struct file *redirect;
 498
 499/**
 500 * tty_wakeup - request more data
 501 * @tty: terminal
 502 *
 503 * Internal and external helper for wakeups of tty. This function informs the
 504 * line discipline if present that the driver is ready to receive more output
 505 * data.
 506 */
 507void tty_wakeup(struct tty_struct *tty)
 508{
 509	struct tty_ldisc *ld;
 510
 511	if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
 512		ld = tty_ldisc_ref(tty);
 513		if (ld) {
 514			if (ld->ops->write_wakeup)
 515				ld->ops->write_wakeup(tty);
 516			tty_ldisc_deref(ld);
 517		}
 518	}
 519	wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
 520}
 521EXPORT_SYMBOL_GPL(tty_wakeup);
 522
 523/**
 524 * tty_release_redirect - Release a redirect on a pty if present
 525 * @tty: tty device
 526 *
 527 * This is available to the pty code so if the master closes, if the slave is a
 528 * redirect it can release the redirect.
 529 */
 530static struct file *tty_release_redirect(struct tty_struct *tty)
 531{
 532	guard(spinlock)(&redirect_lock);
 533
 534	if (redirect && file_tty(redirect) == tty) {
 535		struct file *f = redirect;
 536		redirect = NULL;
 537		return f;
 538	}
 539
 540	return NULL;
 541}
 542
 543/**
 544 * __tty_hangup - actual handler for hangup events
 545 * @tty: tty device
 546 * @exit_session: if non-zero, signal all foreground group processes
 547 *
 548 * This can be called by a "kworker" kernel thread. That is process synchronous
 549 * but doesn't hold any locks, so we need to make sure we have the appropriate
 550 * locks for what we're doing.
 551 *
 552 * The hangup event clears any pending redirections onto the hung up device. It
 553 * ensures future writes will error and it does the needed line discipline
 554 * hangup and signal delivery. The tty object itself remains intact.
 555 *
 556 * Locking:
 557 *  * BTM
 558 *
 559 *   * redirect lock for undoing redirection
 560 *   * file list lock for manipulating list of ttys
 561 *   * tty_ldiscs_lock from called functions
 562 *   * termios_rwsem resetting termios data
 563 *   * tasklist_lock to walk task list for hangup event
 564 *
 565 *    * ->siglock to protect ->signal/->sighand
 566 *
 567 */
 568static void __tty_hangup(struct tty_struct *tty, int exit_session)
 569{
 570	struct file *cons_filp = NULL;
 571	struct file *filp, *f;
 572	struct tty_file_private *priv;
 573	int    closecount = 0, n;
 574	int refs;
 575
 576	if (!tty)
 577		return;
 578
 579	f = tty_release_redirect(tty);
 580
 581	tty_lock(tty);
 582
 583	if (test_bit(TTY_HUPPED, &tty->flags)) {
 584		tty_unlock(tty);
 585		return;
 586	}
 587
 588	/*
 589	 * Some console devices aren't actually hung up for technical and
 590	 * historical reasons, which can lead to indefinite interruptible
 591	 * sleep in n_tty_read().  The following explicitly tells
 592	 * n_tty_read() to abort readers.
 593	 */
 594	set_bit(TTY_HUPPING, &tty->flags);
 595
 596	/* inuse_filps is protected by the single tty lock,
 597	 * this really needs to change if we want to flush the
 598	 * workqueue with the lock held.
 599	 */
 600	check_tty_count(tty, "tty_hangup");
 601
 602	spin_lock(&tty->files_lock);
 603	/* This breaks for file handles being sent over AF_UNIX sockets ? */
 604	list_for_each_entry(priv, &tty->tty_files, list) {
 605		filp = priv->file;
 606		if (filp->f_op->write_iter == redirected_tty_write)
 607			cons_filp = filp;
 608		if (filp->f_op->write_iter != tty_write)
 609			continue;
 610		closecount++;
 611		__tty_fasync(-1, filp, 0);	/* can't block */
 612		filp->f_op = &hung_up_tty_fops;
 613	}
 614	spin_unlock(&tty->files_lock);
 615
 616	refs = tty_signal_session_leader(tty, exit_session);
 617	/* Account for the p->signal references we killed */
 618	while (refs--)
 619		tty_kref_put(tty);
 620
 621	tty_ldisc_hangup(tty, cons_filp != NULL);
 622
 623	spin_lock_irq(&tty->ctrl.lock);
 624	clear_bit(TTY_THROTTLED, &tty->flags);
 625	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 626	put_pid(tty->ctrl.session);
 627	put_pid(tty->ctrl.pgrp);
 628	tty->ctrl.session = NULL;
 629	tty->ctrl.pgrp = NULL;
 630	tty->ctrl.pktstatus = 0;
 631	spin_unlock_irq(&tty->ctrl.lock);
 632
 633	/*
 634	 * If one of the devices matches a console pointer, we
 635	 * cannot just call hangup() because that will cause
 636	 * tty->count and state->count to go out of sync.
 637	 * So we just call close() the right number of times.
 638	 */
 639	if (cons_filp) {
 640		if (tty->ops->close)
 641			for (n = 0; n < closecount; n++)
 642				tty->ops->close(tty, cons_filp);
 643	} else if (tty->ops->hangup)
 644		tty->ops->hangup(tty);
 645	/*
 646	 * We don't want to have driver/ldisc interactions beyond the ones
 647	 * we did here. The driver layer expects no calls after ->hangup()
 648	 * from the ldisc side, which is now guaranteed.
 649	 */
 650	set_bit(TTY_HUPPED, &tty->flags);
 651	clear_bit(TTY_HUPPING, &tty->flags);
 652	tty_unlock(tty);
 653
 654	if (f)
 655		fput(f);
 656}
 657
 658static void do_tty_hangup(struct work_struct *work)
 659{
 660	struct tty_struct *tty =
 661		container_of(work, struct tty_struct, hangup_work);
 662
 663	__tty_hangup(tty, 0);
 664}
 665
 666/**
 667 * tty_hangup - trigger a hangup event
 668 * @tty: tty to hangup
 669 *
 670 * A carrier loss (virtual or otherwise) has occurred on @tty. Schedule a
 671 * hangup sequence to run after this event.
 672 */
 673void tty_hangup(struct tty_struct *tty)
 674{
 675	tty_debug_hangup(tty, "hangup\n");
 676	schedule_work(&tty->hangup_work);
 677}
 678EXPORT_SYMBOL(tty_hangup);
 679
 680/**
 681 * tty_vhangup - process vhangup
 682 * @tty: tty to hangup
 683 *
 684 * The user has asked via system call for the terminal to be hung up. We do
 685 * this synchronously so that when the syscall returns the process is complete.
 686 * That guarantee is necessary for security reasons.
 687 */
 688void tty_vhangup(struct tty_struct *tty)
 689{
 690	tty_debug_hangup(tty, "vhangup\n");
 691	__tty_hangup(tty, 0);
 692}
 693EXPORT_SYMBOL(tty_vhangup);
 694
 695
 696/**
 697 * tty_vhangup_self - process vhangup for own ctty
 698 *
 699 * Perform a vhangup on the current controlling tty
 700 */
 701void tty_vhangup_self(void)
 702{
 703	struct tty_struct *tty;
 704
 705	tty = get_current_tty();
 706	if (tty) {
 707		tty_vhangup(tty);
 708		tty_kref_put(tty);
 709	}
 710}
 711
 712/**
 713 * tty_vhangup_session - hangup session leader exit
 714 * @tty: tty to hangup
 715 *
 716 * The session leader is exiting and hanging up its controlling terminal.
 717 * Every process in the foreground process group is signalled %SIGHUP.
 718 *
 719 * We do this synchronously so that when the syscall returns the process is
 720 * complete. That guarantee is necessary for security reasons.
 721 */
 722void tty_vhangup_session(struct tty_struct *tty)
 723{
 724	tty_debug_hangup(tty, "session hangup\n");
 725	__tty_hangup(tty, 1);
 726}
 727
 728/**
 729 * tty_hung_up_p - was tty hung up
 730 * @filp: file pointer of tty
 731 *
 732 * Return: true if the tty has been subject to a vhangup or a carrier loss
 733 */
 734int tty_hung_up_p(struct file *filp)
 735{
 736	return (filp && filp->f_op == &hung_up_tty_fops);
 737}
 738EXPORT_SYMBOL(tty_hung_up_p);
 739
 740void __stop_tty(struct tty_struct *tty)
 741{
 742	if (tty->flow.stopped)
 743		return;
 744	tty->flow.stopped = true;
 745	if (tty->ops->stop)
 746		tty->ops->stop(tty);
 747}
 748
 749/**
 750 * stop_tty - propagate flow control
 751 * @tty: tty to stop
 752 *
 753 * Perform flow control to the driver. May be called on an already stopped
 754 * device and will not re-call the &tty_driver->stop() method.
 755 *
 756 * This functionality is used by both the line disciplines for halting incoming
 757 * flow and by the driver. It may therefore be called from any context, may be
 758 * under the tty %atomic_write_lock but not always.
 759 *
 760 * Locking:
 761 *	flow.lock
 762 */
 763void stop_tty(struct tty_struct *tty)
 764{
 765	guard(spinlock_irqsave)(&tty->flow.lock);
 766	__stop_tty(tty);
 767}
 768EXPORT_SYMBOL(stop_tty);
 769
 770void __start_tty(struct tty_struct *tty)
 771{
 772	if (!tty->flow.stopped || tty->flow.tco_stopped)
 773		return;
 774	tty->flow.stopped = false;
 775	if (tty->ops->start)
 776		tty->ops->start(tty);
 777	tty_wakeup(tty);
 778}
 779
 780/**
 781 * start_tty - propagate flow control
 782 * @tty: tty to start
 783 *
 784 * Start a tty that has been stopped if at all possible. If @tty was previously
 785 * stopped and is now being started, the &tty_driver->start() method is invoked
 786 * and the line discipline woken.
 787 *
 788 * Locking:
 789 *	flow.lock
 790 */
 791void start_tty(struct tty_struct *tty)
 792{
 793	guard(spinlock_irqsave)(&tty->flow.lock);
 794	__start_tty(tty);
 795}
 796EXPORT_SYMBOL(start_tty);
 797
 798static void tty_update_time(struct tty_struct *tty, bool mtime)
 799{
 800	time64_t sec = ktime_get_real_seconds();
 801	struct tty_file_private *priv;
 802
 803	guard(spinlock)(&tty->files_lock);
 804
 805	list_for_each_entry(priv, &tty->tty_files, list) {
 806		struct inode *inode = file_inode(priv->file);
 807		struct timespec64 time = mtime ? inode_get_mtime(inode) : inode_get_atime(inode);
 808
 809		/*
 810		 * We only care if the two values differ in anything other than the
 811		 * lower three bits (i.e every 8 seconds).  If so, then we can update
 812		 * the time of the tty device, otherwise it could be construded as a
 813		 * security leak to let userspace know the exact timing of the tty.
 814		 */
 815		if ((sec ^ time.tv_sec) & ~7) {
 816			if (mtime)
 817				inode_set_mtime(inode, sec, 0);
 818			else
 819				inode_set_atime(inode, sec, 0);
 820		}
 821	}
 822}
 823
 824/*
 825 * Iterate on the ldisc ->read() function until we've gotten all
 826 * the data the ldisc has for us.
 827 *
 828 * The "cookie" is something that the ldisc read function can fill
 829 * in to let us know that there is more data to be had.
 830 *
 831 * We promise to continue to call the ldisc until it stops returning
 832 * data or clears the cookie. The cookie may be something that the
 833 * ldisc maintains state for and needs to free.
 834 */
 835static ssize_t iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty,
 836				struct file *file, struct iov_iter *to)
 837{
 838	void *cookie = NULL;
 839	unsigned long offset = 0;
 840	ssize_t retval = 0;
 841	size_t copied, count = iov_iter_count(to);
 842	u8 kernel_buf[64];
 843
 844	do {
 845		ssize_t size = min(count, sizeof(kernel_buf));
 846
 847		size = ld->ops->read(tty, file, kernel_buf, size, &cookie, offset);
 848		if (!size)
 849			break;
 850
 851		if (size < 0) {
 852			/* Did we have an earlier error (ie -EFAULT)? */
 853			if (retval)
 854				break;
 855			retval = size;
 856
 857			/*
 858			 * -EOVERFLOW means we didn't have enough space
 859			 * for a whole packet, and we shouldn't return
 860			 * a partial result.
 861			 */
 862			if (retval == -EOVERFLOW)
 863				offset = 0;
 864			break;
 865		}
 866
 867		copied = copy_to_iter(kernel_buf, size, to);
 868		offset += copied;
 869		count -= copied;
 870
 871		/*
 872		 * If the user copy failed, we still need to do another ->read()
 873		 * call if we had a cookie to let the ldisc clear up.
 874		 *
 875		 * But make sure size is zeroed.
 876		 */
 877		if (unlikely(copied != size)) {
 878			count = 0;
 879			retval = -EFAULT;
 880		}
 881	} while (cookie);
 882
 883	/* We always clear tty buffer in case they contained passwords */
 884	memzero_explicit(kernel_buf, sizeof(kernel_buf));
 885	return offset ? offset : retval;
 886}
 887
 888
 889/**
 890 * tty_read - read method for tty device files
 891 * @iocb: kernel I/O control block
 892 * @to: destination for the data read
 893 *
 894 * Perform the read system call function on this terminal device. Checks
 895 * for hung up devices before calling the line discipline method.
 896 *
 897 * Locking:
 898 *	Locks the line discipline internally while needed. Multiple read calls
 899 *	may be outstanding in parallel.
 900 */
 901static ssize_t tty_read(struct kiocb *iocb, struct iov_iter *to)
 902{
 903	struct file *file = iocb->ki_filp;
 904	struct inode *inode = file_inode(file);
 905	struct tty_struct *tty = file_tty(file);
 906	struct tty_ldisc *ld;
 907	ssize_t ret;
 908
 909	if (tty_paranoia_check(tty, inode, "tty_read"))
 910		return -EIO;
 911	if (!tty || tty_io_error(tty))
 912		return -EIO;
 913
 914	/* We want to wait for the line discipline to sort out in this
 915	 * situation.
 916	 */
 917	ld = tty_ldisc_ref_wait(tty);
 918	if (!ld)
 919		return hung_up_tty_read(iocb, to);
 920	ret = -EIO;
 921	if (ld->ops->read)
 922		ret = iterate_tty_read(ld, tty, file, to);
 923	tty_ldisc_deref(ld);
 924
 925	if (ret > 0)
 926		tty_update_time(tty, false);
 927
 928	return ret;
 929}
 930
 931void tty_write_unlock(struct tty_struct *tty)
 932{
 933	mutex_unlock(&tty->atomic_write_lock);
 934	wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT);
 935}
 936
 937int tty_write_lock(struct tty_struct *tty, bool ndelay)
 938{
 939	if (!mutex_trylock(&tty->atomic_write_lock)) {
 940		if (ndelay)
 941			return -EAGAIN;
 942		if (mutex_lock_interruptible(&tty->atomic_write_lock))
 943			return -ERESTARTSYS;
 944	}
 945	return 0;
 946}
 947
 948/*
 949 * Split writes up in sane blocksizes to avoid
 950 * denial-of-service type attacks
 951 */
 952static ssize_t iterate_tty_write(struct tty_ldisc *ld, struct tty_struct *tty,
 953				 struct file *file, struct iov_iter *from)
 954{
 955	size_t chunk, count = iov_iter_count(from);
 956	ssize_t ret, written = 0;
 957
 958	ret = tty_write_lock(tty, file->f_flags & O_NDELAY);
 959	if (ret < 0)
 960		return ret;
 961
 962	/*
 963	 * We chunk up writes into a temporary buffer. This
 964	 * simplifies low-level drivers immensely, since they
 965	 * don't have locking issues and user mode accesses.
 966	 *
 967	 * But if TTY_NO_WRITE_SPLIT is set, we should use a
 968	 * big chunk-size..
 969	 *
 970	 * The default chunk-size is 2kB, because the NTTY
 971	 * layer has problems with bigger chunks. It will
 972	 * claim to be able to handle more characters than
 973	 * it actually does.
 974	 */
 975	chunk = 2048;
 976	if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
 977		chunk = 65536;
 978	if (count < chunk)
 979		chunk = count;
 980
 981	/* write_buf/write_cnt is protected by the atomic_write_lock mutex */
 982	if (tty->write_cnt < chunk) {
 983		u8 *buf_chunk;
 984
 985		if (chunk < 1024)
 986			chunk = 1024;
 987
 988		buf_chunk = kvmalloc(chunk, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
 989		if (!buf_chunk) {
 990			ret = -ENOMEM;
 991			goto out;
 992		}
 993		kvfree(tty->write_buf);
 994		tty->write_cnt = chunk;
 995		tty->write_buf = buf_chunk;
 996	}
 997
 998	/* Do the write .. */
 999	for (;;) {
1000		size_t size = min(chunk, count);
1001
1002		ret = -EFAULT;
1003		if (copy_from_iter(tty->write_buf, size, from) != size)
1004			break;
1005
1006		ret = ld->ops->write(tty, file, tty->write_buf, size);
1007		if (ret <= 0)
1008			break;
1009
1010		written += ret;
1011		if (ret > size)
1012			break;
1013
1014		/* FIXME! Have Al check this! */
1015		if (ret != size)
1016			iov_iter_revert(from, size-ret);
1017
1018		count -= ret;
1019		if (!count)
1020			break;
1021		ret = -ERESTARTSYS;
1022		if (signal_pending(current))
1023			break;
1024		cond_resched();
1025	}
1026	if (written) {
1027		tty_update_time(tty, true);
1028		ret = written;
1029	}
1030out:
1031	tty_write_unlock(tty);
1032	return ret;
1033}
1034
1035#ifdef CONFIG_PRINT_QUOTA_WARNING
1036/**
1037 * tty_write_message - write a message to a certain tty, not just the console.
1038 * @tty: the destination tty_struct
1039 * @msg: the message to write
1040 *
1041 * This is used for messages that need to be redirected to a specific tty. We
1042 * don't put it into the syslog queue right now maybe in the future if really
1043 * needed.
1044 *
1045 * We must still hold the BTM and test the CLOSING flag for the moment.
1046 *
1047 * This function is DEPRECATED, do not use in new code.
1048 */
1049void tty_write_message(struct tty_struct *tty, char *msg)
1050{
1051	if (tty) {
1052		mutex_lock(&tty->atomic_write_lock);
1053		tty_lock(tty);
1054		if (tty->ops->write && tty->count > 0)
1055			tty->ops->write(tty, msg, strlen(msg));
1056		tty_unlock(tty);
1057		tty_write_unlock(tty);
1058	}
1059}
1060#endif
1061
1062static ssize_t file_tty_write(struct file *file, struct kiocb *iocb, struct iov_iter *from)
1063{
1064	struct tty_struct *tty = file_tty(file);
1065	struct tty_ldisc *ld;
1066	ssize_t ret;
1067
1068	if (tty_paranoia_check(tty, file_inode(file), "tty_write"))
1069		return -EIO;
1070	if (!tty || !tty->ops->write ||	tty_io_error(tty))
1071		return -EIO;
1072	/* Short term debug to catch buggy drivers */
1073	if (tty->ops->write_room == NULL)
1074		tty_err(tty, "missing write_room method\n");
1075	ld = tty_ldisc_ref_wait(tty);
1076	if (!ld)
1077		return hung_up_tty_write(iocb, from);
1078	if (!ld->ops->write)
1079		ret = -EIO;
1080	else
1081		ret = iterate_tty_write(ld, tty, file, from);
1082	tty_ldisc_deref(ld);
1083	return ret;
1084}
1085
1086/**
1087 * tty_write - write method for tty device file
1088 * @iocb: kernel I/O control block
1089 * @from: iov_iter with data to write
1090 *
1091 * Write data to a tty device via the line discipline.
1092 *
1093 * Locking:
1094 *	Locks the line discipline as required
1095 *	Writes to the tty driver are serialized by the atomic_write_lock
1096 *	and are then processed in chunks to the device. The line
1097 *	discipline write method will not be invoked in parallel for
1098 *	each device.
1099 */
1100static ssize_t tty_write(struct kiocb *iocb, struct iov_iter *from)
1101{
1102	return file_tty_write(iocb->ki_filp, iocb, from);
1103}
1104
1105ssize_t redirected_tty_write(struct kiocb *iocb, struct iov_iter *iter)
1106{
1107	struct file *p = NULL;
1108
1109	spin_lock(&redirect_lock);
1110	if (redirect)
1111		p = get_file(redirect);
1112	spin_unlock(&redirect_lock);
1113
1114	/*
1115	 * We know the redirected tty is just another tty, we can
1116	 * call file_tty_write() directly with that file pointer.
1117	 */
1118	if (p) {
1119		ssize_t res;
1120
1121		res = file_tty_write(p, iocb, iter);
1122		fput(p);
1123		return res;
1124	}
1125	return tty_write(iocb, iter);
1126}
1127
1128/**
1129 * tty_send_xchar - send priority character
1130 * @tty: the tty to send to
1131 * @ch: xchar to send
1132 *
1133 * Send a high priority character to the tty even if stopped.
1134 *
1135 * Locking: none for xchar method, write ordering for write method.
1136 */
1137int tty_send_xchar(struct tty_struct *tty, u8 ch)
1138{
1139	bool was_stopped = tty->flow.stopped;
1140
1141	if (tty->ops->send_xchar) {
1142		down_read(&tty->termios_rwsem);
1143		tty->ops->send_xchar(tty, ch);
1144		up_read(&tty->termios_rwsem);
1145		return 0;
1146	}
1147
1148	if (tty_write_lock(tty, false) < 0)
1149		return -ERESTARTSYS;
1150
1151	down_read(&tty->termios_rwsem);
1152	if (was_stopped)
1153		start_tty(tty);
1154	tty->ops->write(tty, &ch, 1);
1155	if (was_stopped)
1156		stop_tty(tty);
1157	up_read(&tty->termios_rwsem);
1158	tty_write_unlock(tty);
1159	return 0;
1160}
1161
1162/**
1163 * pty_line_name - generate name for a pty
1164 * @driver: the tty driver in use
1165 * @index: the minor number
1166 * @p: output buffer of at least 6 bytes
1167 *
1168 * Generate a name from a @driver reference and write it to the output buffer
1169 * @p.
1170 *
1171 * Locking: None
1172 */
1173static void pty_line_name(struct tty_driver *driver, int index, char *p)
1174{
1175	static const char ptychar[] = "pqrstuvwxyzabcde";
1176	int i = index + driver->name_base;
1177	/* ->name is initialized to "ttyp", but "tty" is expected */
1178	sprintf(p, "%s%c%x",
1179		driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
1180		ptychar[i >> 4 & 0xf], i & 0xf);
1181}
1182
1183/**
1184 * tty_line_name - generate name for a tty
1185 * @driver: the tty driver in use
1186 * @index: the minor number
1187 * @p: output buffer of at least 7 bytes
1188 *
1189 * Generate a name from a @driver reference and write it to the output buffer
1190 * @p.
1191 *
1192 * Locking: None
1193 */
1194static ssize_t tty_line_name(struct tty_driver *driver, int index, char *p)
1195{
1196	if (driver->flags & TTY_DRIVER_UNNUMBERED_NODE)
1197		return sprintf(p, "%s", driver->name);
1198	else
1199		return sprintf(p, "%s%d", driver->name,
1200			       index + driver->name_base);
1201}
1202
1203/**
1204 * tty_driver_lookup_tty() - find an existing tty, if any
1205 * @driver: the driver for the tty
1206 * @file: file object
1207 * @idx: the minor number
1208 *
1209 * Return: the tty, if found. If not found, return %NULL or ERR_PTR() if the
1210 * driver lookup() method returns an error.
1211 *
1212 * Locking: tty_mutex must be held. If the tty is found, bump the tty kref.
1213 */
1214static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver,
1215		struct file *file, int idx)
1216{
1217	struct tty_struct *tty;
1218
1219	if (driver->ops->lookup) {
1220		if (!file)
1221			tty = ERR_PTR(-EIO);
1222		else
1223			tty = driver->ops->lookup(driver, file, idx);
1224	} else {
1225		if (idx >= driver->num)
1226			return ERR_PTR(-EINVAL);
1227		tty = driver->ttys[idx];
1228	}
1229	if (!IS_ERR(tty))
1230		tty_kref_get(tty);
1231	return tty;
1232}
1233
1234/**
1235 * tty_init_termios - helper for termios setup
1236 * @tty: the tty to set up
1237 *
1238 * Initialise the termios structure for this tty. This runs under the
1239 * %tty_mutex currently so we can be relaxed about ordering.
1240 */
1241void tty_init_termios(struct tty_struct *tty)
1242{
1243	struct ktermios *tp;
1244	int idx = tty->index;
1245
1246	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
1247		tty->termios = tty->driver->init_termios;
1248	else {
1249		/* Check for lazy saved data */
1250		tp = tty->driver->termios[idx];
1251		if (tp != NULL) {
1252			tty->termios = *tp;
1253			tty->termios.c_line  = tty->driver->init_termios.c_line;
1254		} else
1255			tty->termios = tty->driver->init_termios;
1256	}
1257	/* Compatibility until drivers always set this */
1258	tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
1259	tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
1260}
1261EXPORT_SYMBOL_GPL(tty_init_termios);
1262
1263/**
1264 * tty_standard_install - usual tty->ops->install
1265 * @driver: the driver for the tty
1266 * @tty: the tty
1267 *
1268 * If the @driver overrides @tty->ops->install, it still can call this function
1269 * to perform the standard install operations.
1270 */
1271int tty_standard_install(struct tty_driver *driver, struct tty_struct *tty)
1272{
1273	tty_init_termios(tty);
1274	tty_driver_kref_get(driver);
1275	tty->count++;
1276	driver->ttys[tty->index] = tty;
1277	return 0;
1278}
1279EXPORT_SYMBOL_GPL(tty_standard_install);
1280
1281/**
1282 * tty_driver_install_tty() - install a tty entry in the driver
1283 * @driver: the driver for the tty
1284 * @tty: the tty
1285 *
1286 * Install a tty object into the driver tables. The @tty->index field will be
1287 * set by the time this is called. This method is responsible for ensuring any
1288 * need additional structures are allocated and configured.
1289 *
1290 * Locking: tty_mutex for now
1291 */
1292static int tty_driver_install_tty(struct tty_driver *driver,
1293						struct tty_struct *tty)
1294{
1295	return driver->ops->install ? driver->ops->install(driver, tty) :
1296		tty_standard_install(driver, tty);
1297}
1298
1299/**
1300 * tty_driver_remove_tty() - remove a tty from the driver tables
1301 * @driver: the driver for the tty
1302 * @tty: tty to remove
1303 *
1304 * Remove a tty object from the driver tables. The tty->index field will be set
1305 * by the time this is called.
1306 *
1307 * Locking: tty_mutex for now
1308 */
1309static void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty)
1310{
1311	if (driver->ops->remove)
1312		driver->ops->remove(driver, tty);
1313	else
1314		driver->ttys[tty->index] = NULL;
1315}
1316
1317/**
1318 * tty_reopen() - fast re-open of an open tty
1319 * @tty: the tty to open
1320 *
1321 * Re-opens on master ptys are not allowed and return -%EIO.
1322 *
1323 * Locking: Caller must hold tty_lock
1324 * Return: 0 on success, -errno on error.
1325 */
1326static int tty_reopen(struct tty_struct *tty)
1327{
1328	struct tty_driver *driver = tty->driver;
1329	struct tty_ldisc *ld;
1330	int retval = 0;
1331
1332	if (driver->type == TTY_DRIVER_TYPE_PTY &&
1333	    driver->subtype == PTY_TYPE_MASTER)
1334		return -EIO;
1335
1336	if (!tty->count)
1337		return -EAGAIN;
1338
1339	if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
1340		return -EBUSY;
1341
1342	ld = tty_ldisc_ref_wait(tty);
1343	if (ld) {
1344		tty_ldisc_deref(ld);
1345	} else {
1346		retval = tty_ldisc_lock(tty, 5 * HZ);
1347		if (retval)
1348			return retval;
1349
1350		if (!tty->ldisc)
1351			retval = tty_ldisc_reinit(tty, tty->termios.c_line);
1352		tty_ldisc_unlock(tty);
1353	}
1354
1355	if (retval == 0)
1356		tty->count++;
1357
1358	return retval;
1359}
1360
1361/**
1362 * tty_init_dev - initialise a tty device
1363 * @driver: tty driver we are opening a device on
1364 * @idx: device index
1365 *
1366 * Prepare a tty device. This may not be a "new" clean device but could also be
1367 * an active device. The pty drivers require special handling because of this.
1368 *
1369 * Locking:
1370 *	The function is called under the tty_mutex, which protects us from the
1371 *	tty struct or driver itself going away.
1372 *
1373 * On exit the tty device has the line discipline attached and a reference
1374 * count of 1. If a pair was created for pty/tty use and the other was a pty
1375 * master then it too has a reference count of 1.
1376 *
1377 * WSH 06/09/97: Rewritten to remove races and properly clean up after a failed
1378 * open. The new code protects the open with a mutex, so it's really quite
1379 * straightforward. The mutex locking can probably be relaxed for the (most
1380 * common) case of reopening a tty.
1381 *
1382 * Return: new tty structure
1383 */
1384struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
1385{
1386	struct tty_struct *tty;
1387	int retval;
1388
1389	/*
1390	 * First time open is complex, especially for PTY devices.
1391	 * This code guarantees that either everything succeeds and the
1392	 * TTY is ready for operation, or else the table slots are vacated
1393	 * and the allocated memory released.  (Except that the termios
1394	 * may be retained.)
1395	 */
1396
1397	if (!try_module_get(driver->owner))
1398		return ERR_PTR(-ENODEV);
1399
1400	tty = alloc_tty_struct(driver, idx);
1401	if (!tty) {
1402		retval = -ENOMEM;
1403		goto err_module_put;
1404	}
1405
1406	tty_lock(tty);
1407	retval = tty_driver_install_tty(driver, tty);
1408	if (retval < 0)
1409		goto err_free_tty;
1410
1411	if (!tty->port)
1412		tty->port = driver->ports[idx];
1413
1414	if (WARN_RATELIMIT(!tty->port,
1415			"%s: %s driver does not set tty->port. This would crash the kernel. Fix the driver!\n",
1416			__func__, tty->driver->name)) {
1417		retval = -EINVAL;
1418		goto err_release_lock;
1419	}
1420
1421	retval = tty_ldisc_lock(tty, 5 * HZ);
1422	if (retval)
1423		goto err_release_lock;
1424	tty->port->itty = tty;
1425
1426	/*
1427	 * Structures all installed ... call the ldisc open routines.
1428	 * If we fail here just call release_tty to clean up.  No need
1429	 * to decrement the use counts, as release_tty doesn't care.
1430	 */
1431	retval = tty_ldisc_setup(tty, tty->link);
1432	if (retval)
1433		goto err_release_tty;
1434	tty_ldisc_unlock(tty);
1435	/* Return the tty locked so that it cannot vanish under the caller */
1436	return tty;
1437
1438err_free_tty:
1439	tty_unlock(tty);
1440	free_tty_struct(tty);
1441err_module_put:
1442	module_put(driver->owner);
1443	return ERR_PTR(retval);
1444
1445	/* call the tty release_tty routine to clean out this slot */
1446err_release_tty:
1447	tty_ldisc_unlock(tty);
1448	tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
1449			     retval, idx);
1450err_release_lock:
1451	tty_unlock(tty);
1452	release_tty(tty, idx);
1453	return ERR_PTR(retval);
1454}
1455
1456/**
1457 * tty_save_termios() - save tty termios data in driver table
1458 * @tty: tty whose termios data to save
1459 *
1460 * Locking: Caller guarantees serialisation with tty_init_termios().
1461 */
1462void tty_save_termios(struct tty_struct *tty)
1463{
1464	struct ktermios *tp;
1465	int idx = tty->index;
1466
1467	/* If the port is going to reset then it has no termios to save */
1468	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
1469		return;
1470
1471	/* Stash the termios data */
1472	tp = tty->driver->termios[idx];
1473	if (tp == NULL) {
1474		tp = kmalloc(sizeof(*tp), GFP_KERNEL);
1475		if (tp == NULL)
1476			return;
1477		tty->driver->termios[idx] = tp;
1478	}
1479	*tp = tty->termios;
1480}
1481EXPORT_SYMBOL_GPL(tty_save_termios);
1482
1483/**
1484 * tty_flush_works - flush all works of a tty/pty pair
1485 * @tty: tty device to flush works for (or either end of a pty pair)
1486 *
1487 * Sync flush all works belonging to @tty (and the 'other' tty).
1488 */
1489static void tty_flush_works(struct tty_struct *tty)
1490{
1491	flush_work(&tty->SAK_work);
1492	flush_work(&tty->hangup_work);
1493	if (tty->link) {
1494		flush_work(&tty->link->SAK_work);
1495		flush_work(&tty->link->hangup_work);
1496	}
1497}
1498
1499/**
1500 * release_one_tty - release tty structure memory
1501 * @work: work of tty we are obliterating
1502 *
1503 * Releases memory associated with a tty structure, and clears out the
1504 * driver table slots. This function is called when a device is no longer
1505 * in use. It also gets called when setup of a device fails.
1506 *
1507 * Locking:
1508 *	takes the file list lock internally when working on the list of ttys
1509 *	that the driver keeps.
1510 *
1511 * This method gets called from a work queue so that the driver private
1512 * cleanup ops can sleep (needed for USB at least)
1513 */
1514static void release_one_tty(struct work_struct *work)
1515{
1516	struct tty_struct *tty =
1517		container_of(work, struct tty_struct, hangup_work);
1518	struct tty_driver *driver = tty->driver;
1519	struct module *owner = driver->owner;
1520
1521	if (tty->ops->cleanup)
1522		tty->ops->cleanup(tty);
1523
1524	tty_driver_kref_put(driver);
1525	module_put(owner);
1526
1527	spin_lock(&tty->files_lock);
1528	list_del_init(&tty->tty_files);
1529	spin_unlock(&tty->files_lock);
1530
1531	put_pid(tty->ctrl.pgrp);
1532	put_pid(tty->ctrl.session);
1533	free_tty_struct(tty);
1534}
1535
1536static void queue_release_one_tty(struct kref *kref)
1537{
1538	struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
1539
1540	/* The hangup queue is now free so we can reuse it rather than
1541	 *  waste a chunk of memory for each port.
1542	 */
1543	INIT_WORK(&tty->hangup_work, release_one_tty);
1544	schedule_work(&tty->hangup_work);
1545}
1546
1547/**
1548 * tty_kref_put - release a tty kref
1549 * @tty: tty device
1550 *
1551 * Release a reference to the @tty device and if need be let the kref layer
1552 * destruct the object for us.
1553 */
1554void tty_kref_put(struct tty_struct *tty)
1555{
1556	if (tty)
1557		kref_put(&tty->kref, queue_release_one_tty);
1558}
1559EXPORT_SYMBOL(tty_kref_put);
1560
1561/**
1562 * release_tty - release tty structure memory
1563 * @tty: tty device release
1564 * @idx: index of the tty device release
1565 *
1566 * Release both @tty and a possible linked partner (think pty pair),
1567 * and decrement the refcount of the backing module.
1568 *
1569 * Locking:
1570 *	tty_mutex
1571 *	takes the file list lock internally when working on the list of ttys
1572 *	that the driver keeps.
1573 */
1574static void release_tty(struct tty_struct *tty, int idx)
1575{
1576	/* This should always be true but check for the moment */
1577	WARN_ON(tty->index != idx);
1578	WARN_ON(!mutex_is_locked(&tty_mutex));
1579	if (tty->ops->shutdown)
1580		tty->ops->shutdown(tty);
1581	tty_save_termios(tty);
1582	tty_driver_remove_tty(tty->driver, tty);
1583	if (tty->port)
1584		tty->port->itty = NULL;
1585	if (tty->link)
1586		tty->link->port->itty = NULL;
1587	if (tty->port)
1588		tty_buffer_cancel_work(tty->port);
1589	if (tty->link)
1590		tty_buffer_cancel_work(tty->link->port);
1591
1592	tty_kref_put(tty->link);
1593	tty_kref_put(tty);
1594}
1595
1596/**
1597 * tty_release_checks - check a tty before real release
1598 * @tty: tty to check
1599 * @idx: index of the tty
1600 *
1601 * Performs some paranoid checking before true release of the @tty. This is a
1602 * no-op unless %TTY_PARANOIA_CHECK is defined.
1603 */
1604static int tty_release_checks(struct tty_struct *tty, int idx)
1605{
1606#ifdef TTY_PARANOIA_CHECK
1607	if (idx < 0 || idx >= tty->driver->num) {
1608		tty_debug(tty, "bad idx %d\n", idx);
1609		return -1;
1610	}
1611
1612	/* not much to check for devpts */
1613	if (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)
1614		return 0;
1615
1616	if (tty != tty->driver->ttys[idx]) {
1617		tty_debug(tty, "bad driver table[%d] = %p\n",
1618			  idx, tty->driver->ttys[idx]);
1619		return -1;
1620	}
1621	if (tty->driver->other) {
1622		struct tty_struct *o_tty = tty->link;
1623
1624		if (o_tty != tty->driver->other->ttys[idx]) {
1625			tty_debug(tty, "bad other table[%d] = %p\n",
1626				  idx, tty->driver->other->ttys[idx]);
1627			return -1;
1628		}
1629		if (o_tty->link != tty) {
1630			tty_debug(tty, "bad link = %p\n", o_tty->link);
1631			return -1;
1632		}
1633	}
1634#endif
1635	return 0;
1636}
1637
1638/**
1639 * tty_kclose - closes tty opened by tty_kopen
1640 * @tty: tty device
1641 *
1642 * Performs the final steps to release and free a tty device. It is the same as
1643 * tty_release_struct() except that it also resets %TTY_PORT_KOPENED flag on
1644 * @tty->port.
1645 */
1646void tty_kclose(struct tty_struct *tty)
1647{
1648	/*
1649	 * Ask the line discipline code to release its structures
1650	 */
1651	tty_ldisc_release(tty);
1652
1653	/* Wait for pending work before tty destruction commences */
1654	tty_flush_works(tty);
1655
1656	tty_debug_hangup(tty, "freeing structure\n");
1657	/*
1658	 * The release_tty function takes care of the details of clearing
1659	 * the slots and preserving the termios structure.
1660	 */
1661	mutex_lock(&tty_mutex);
1662	tty_port_set_kopened(tty->port, 0);
1663	release_tty(tty, tty->index);
1664	mutex_unlock(&tty_mutex);
1665}
1666EXPORT_SYMBOL_GPL(tty_kclose);
1667
1668/**
1669 * tty_release_struct - release a tty struct
1670 * @tty: tty device
1671 * @idx: index of the tty
1672 *
1673 * Performs the final steps to release and free a tty device. It is roughly the
1674 * reverse of tty_init_dev().
1675 */
1676void tty_release_struct(struct tty_struct *tty, int idx)
1677{
1678	/*
1679	 * Ask the line discipline code to release its structures
1680	 */
1681	tty_ldisc_release(tty);
1682
1683	/* Wait for pending work before tty destruction commmences */
1684	tty_flush_works(tty);
1685
1686	tty_debug_hangup(tty, "freeing structure\n");
1687	/*
1688	 * The release_tty function takes care of the details of clearing
1689	 * the slots and preserving the termios structure.
1690	 */
1691	mutex_lock(&tty_mutex);
1692	release_tty(tty, idx);
1693	mutex_unlock(&tty_mutex);
1694}
1695EXPORT_SYMBOL_GPL(tty_release_struct);
1696
1697/**
1698 * tty_release - vfs callback for close
1699 * @inode: inode of tty
1700 * @filp: file pointer for handle to tty
1701 *
1702 * Called the last time each file handle is closed that references this tty.
1703 * There may however be several such references.
1704 *
1705 * Locking:
1706 *	Takes BKL. See tty_release_dev().
1707 *
1708 * Even releasing the tty structures is a tricky business. We have to be very
1709 * careful that the structures are all released at the same time, as interrupts
1710 * might otherwise get the wrong pointers.
1711 *
1712 * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
1713 * lead to double frees or releasing memory still in use.
1714 */
1715int tty_release(struct inode *inode, struct file *filp)
1716{
1717	struct tty_struct *tty = file_tty(filp);
1718	struct tty_struct *o_tty = NULL;
1719	int	do_sleep, final;
1720	int	idx;
1721	long	timeout = 0;
1722	int	once = 1;
1723
1724	if (tty_paranoia_check(tty, inode, __func__))
1725		return 0;
1726
1727	tty_lock(tty);
1728	check_tty_count(tty, __func__);
1729
1730	__tty_fasync(-1, filp, 0);
1731
1732	idx = tty->index;
1733	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
1734	    tty->driver->subtype == PTY_TYPE_MASTER)
1735		o_tty = tty->link;
1736
1737	if (tty_release_checks(tty, idx)) {
1738		tty_unlock(tty);
1739		return 0;
1740	}
1741
1742	tty_debug_hangup(tty, "releasing (count=%d)\n", tty->count);
1743
1744	if (tty->ops->close)
1745		tty->ops->close(tty, filp);
1746
1747	/* If tty is pty master, lock the slave pty (stable lock order) */
1748	tty_lock_slave(o_tty);
1749
1750	/*
1751	 * Sanity check: if tty->count is going to zero, there shouldn't be
1752	 * any waiters on tty->read_wait or tty->write_wait.  We test the
1753	 * wait queues and kick everyone out _before_ actually starting to
1754	 * close.  This ensures that we won't block while releasing the tty
1755	 * structure.
1756	 *
1757	 * The test for the o_tty closing is necessary, since the master and
1758	 * slave sides may close in any order.  If the slave side closes out
1759	 * first, its count will be one, since the master side holds an open.
1760	 * Thus this test wouldn't be triggered at the time the slave closed,
1761	 * so we do it now.
1762	 */
1763	while (1) {
1764		do_sleep = 0;
1765
1766		if (tty->count <= 1) {
1767			if (waitqueue_active(&tty->read_wait)) {
1768				wake_up_poll(&tty->read_wait, EPOLLIN);
1769				do_sleep++;
1770			}
1771			if (waitqueue_active(&tty->write_wait)) {
1772				wake_up_poll(&tty->write_wait, EPOLLOUT);
1773				do_sleep++;
1774			}
1775		}
1776		if (o_tty && o_tty->count <= 1) {
1777			if (waitqueue_active(&o_tty->read_wait)) {
1778				wake_up_poll(&o_tty->read_wait, EPOLLIN);
1779				do_sleep++;
1780			}
1781			if (waitqueue_active(&o_tty->write_wait)) {
1782				wake_up_poll(&o_tty->write_wait, EPOLLOUT);
1783				do_sleep++;
1784			}
1785		}
1786		if (!do_sleep)
1787			break;
1788
1789		if (once) {
1790			once = 0;
1791			tty_warn(tty, "read/write wait queue active!\n");
1792		}
1793		schedule_timeout_killable(timeout);
1794		if (timeout < 120 * HZ)
1795			timeout = 2 * timeout + 1;
1796		else
1797			timeout = MAX_SCHEDULE_TIMEOUT;
1798	}
1799
1800	if (o_tty) {
1801		if (--o_tty->count < 0) {
1802			tty_warn(tty, "bad slave count (%d)\n", o_tty->count);
1803			o_tty->count = 0;
1804		}
1805	}
1806	if (--tty->count < 0) {
1807		tty_warn(tty, "bad tty->count (%d)\n", tty->count);
1808		tty->count = 0;
1809	}
1810
1811	/*
1812	 * We've decremented tty->count, so we need to remove this file
1813	 * descriptor off the tty->tty_files list; this serves two
1814	 * purposes:
1815	 *  - check_tty_count sees the correct number of file descriptors
1816	 *    associated with this tty.
1817	 *  - do_tty_hangup no longer sees this file descriptor as
1818	 *    something that needs to be handled for hangups.
1819	 */
1820	tty_del_file(filp);
1821
1822	/*
1823	 * Perform some housekeeping before deciding whether to return.
1824	 *
1825	 * If _either_ side is closing, make sure there aren't any
1826	 * processes that still think tty or o_tty is their controlling
1827	 * tty.
1828	 */
1829	if (!tty->count) {
1830		read_lock(&tasklist_lock);
1831		session_clear_tty(tty->ctrl.session);
1832		if (o_tty)
1833			session_clear_tty(o_tty->ctrl.session);
1834		read_unlock(&tasklist_lock);
1835	}
1836
1837	/* check whether both sides are closing ... */
1838	final = !tty->count && !(o_tty && o_tty->count);
1839
1840	tty_unlock_slave(o_tty);
1841	tty_unlock(tty);
1842
1843	/* At this point, the tty->count == 0 should ensure a dead tty
1844	 * cannot be re-opened by a racing opener.
1845	 */
1846
1847	if (!final)
1848		return 0;
1849
1850	tty_debug_hangup(tty, "final close\n");
1851
1852	tty_release_struct(tty, idx);
1853	return 0;
1854}
1855
1856/**
1857 * tty_open_current_tty - get locked tty of current task
1858 * @device: device number
1859 * @filp: file pointer to tty
1860 * @return: locked tty of the current task iff @device is /dev/tty
1861 *
1862 * Performs a re-open of the current task's controlling tty.
1863 *
1864 * We cannot return driver and index like for the other nodes because devpts
1865 * will not work then. It expects inodes to be from devpts FS.
1866 */
1867static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
1868{
1869	struct tty_struct *tty;
1870	int retval;
1871
1872	if (device != MKDEV(TTYAUX_MAJOR, 0))
1873		return NULL;
1874
1875	tty = get_current_tty();
1876	if (!tty)
1877		return ERR_PTR(-ENXIO);
1878
1879	filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
1880	/* noctty = 1; */
1881	tty_lock(tty);
1882	tty_kref_put(tty);	/* safe to drop the kref now */
1883
1884	retval = tty_reopen(tty);
1885	if (retval < 0) {
1886		tty_unlock(tty);
1887		tty = ERR_PTR(retval);
1888	}
1889	return tty;
1890}
1891
1892/**
1893 * tty_lookup_driver - lookup a tty driver for a given device file
1894 * @device: device number
1895 * @filp: file pointer to tty
1896 * @index: index for the device in the @return driver
1897 *
1898 * If returned value is not erroneous, the caller is responsible to decrement
1899 * the refcount by tty_driver_kref_put().
1900 *
1901 * Locking: %tty_mutex protects get_tty_driver()
1902 *
1903 * Return: driver for this inode (with increased refcount)
1904 */
1905static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
1906		int *index)
1907{
1908	struct tty_driver *driver = NULL;
1909
1910	switch (device) {
1911#ifdef CONFIG_VT
1912	case MKDEV(TTY_MAJOR, 0): {
1913		extern struct tty_driver *console_driver;
1914
1915		driver = tty_driver_kref_get(console_driver);
1916		*index = fg_console;
1917		break;
1918	}
1919#endif
1920	case MKDEV(TTYAUX_MAJOR, 1): {
1921		struct tty_driver *console_driver = console_device(index);
1922
1923		if (console_driver) {
1924			driver = tty_driver_kref_get(console_driver);
1925			if (driver && filp) {
1926				/* Don't let /dev/console block */
1927				filp->f_flags |= O_NONBLOCK;
1928				break;
1929			}
1930		}
1931		if (driver)
1932			tty_driver_kref_put(driver);
1933		return ERR_PTR(-ENODEV);
1934	}
1935	default:
1936		driver = get_tty_driver(device, index);
1937		if (!driver)
1938			return ERR_PTR(-ENODEV);
1939		break;
1940	}
1941	return driver;
1942}
1943
1944static struct tty_struct *tty_kopen(dev_t device, int shared)
1945{
1946	struct tty_struct *tty;
1947	struct tty_driver *driver;
1948	int index = -1;
1949
1950	mutex_lock(&tty_mutex);
1951	driver = tty_lookup_driver(device, NULL, &index);
1952	if (IS_ERR(driver)) {
1953		mutex_unlock(&tty_mutex);
1954		return ERR_CAST(driver);
1955	}
1956
1957	/* check whether we're reopening an existing tty */
1958	tty = tty_driver_lookup_tty(driver, NULL, index);
1959	if (IS_ERR(tty) || shared)
1960		goto out;
1961
1962	if (tty) {
1963		/* drop kref from tty_driver_lookup_tty() */
1964		tty_kref_put(tty);
1965		tty = ERR_PTR(-EBUSY);
1966	} else { /* tty_init_dev returns tty with the tty_lock held */
1967		tty = tty_init_dev(driver, index);
1968		if (IS_ERR(tty))
1969			goto out;
1970		tty_port_set_kopened(tty->port, 1);
1971	}
1972out:
1973	mutex_unlock(&tty_mutex);
1974	tty_driver_kref_put(driver);
1975	return tty;
1976}
1977
1978/**
1979 * tty_kopen_exclusive - open a tty device for kernel
1980 * @device: dev_t of device to open
1981 *
1982 * Opens tty exclusively for kernel. Performs the driver lookup, makes sure
1983 * it's not already opened and performs the first-time tty initialization.
1984 *
1985 * Claims the global %tty_mutex to serialize:
1986 *  * concurrent first-time tty initialization
1987 *  * concurrent tty driver removal w/ lookup
1988 *  * concurrent tty removal from driver table
1989 *
1990 * Return: the locked initialized &tty_struct
1991 */
1992struct tty_struct *tty_kopen_exclusive(dev_t device)
1993{
1994	return tty_kopen(device, 0);
1995}
1996EXPORT_SYMBOL_GPL(tty_kopen_exclusive);
1997
1998/**
1999 * tty_kopen_shared - open a tty device for shared in-kernel use
2000 * @device: dev_t of device to open
2001 *
2002 * Opens an already existing tty for in-kernel use. Compared to
2003 * tty_kopen_exclusive() above it doesn't ensure to be the only user.
2004 *
2005 * Locking: identical to tty_kopen() above.
2006 */
2007struct tty_struct *tty_kopen_shared(dev_t device)
2008{
2009	return tty_kopen(device, 1);
2010}
2011EXPORT_SYMBOL_GPL(tty_kopen_shared);
2012
2013/**
2014 * tty_open_by_driver - open a tty device
2015 * @device: dev_t of device to open
2016 * @filp: file pointer to tty
2017 *
2018 * Performs the driver lookup, checks for a reopen, or otherwise performs the
2019 * first-time tty initialization.
2020 *
2021 *
2022 * Claims the global tty_mutex to serialize:
2023 *  * concurrent first-time tty initialization
2024 *  * concurrent tty driver removal w/ lookup
2025 *  * concurrent tty removal from driver table
2026 *
2027 * Return: the locked initialized or re-opened &tty_struct
2028 */
2029static struct tty_struct *tty_open_by_driver(dev_t device,
2030					     struct file *filp)
2031{
2032	struct tty_struct *tty;
2033	struct tty_driver *driver = NULL;
2034	int index = -1;
2035	int retval;
2036
2037	mutex_lock(&tty_mutex);
2038	driver = tty_lookup_driver(device, filp, &index);
2039	if (IS_ERR(driver)) {
2040		mutex_unlock(&tty_mutex);
2041		return ERR_CAST(driver);
2042	}
2043
2044	/* check whether we're reopening an existing tty */
2045	tty = tty_driver_lookup_tty(driver, filp, index);
2046	if (IS_ERR(tty)) {
2047		mutex_unlock(&tty_mutex);
2048		goto out;
2049	}
2050
2051	if (tty) {
2052		if (tty_port_kopened(tty->port)) {
2053			tty_kref_put(tty);
2054			mutex_unlock(&tty_mutex);
2055			tty = ERR_PTR(-EBUSY);
2056			goto out;
2057		}
2058		mutex_unlock(&tty_mutex);
2059		retval = tty_lock_interruptible(tty);
2060		tty_kref_put(tty);  /* drop kref from tty_driver_lookup_tty() */
2061		if (retval) {
2062			if (retval == -EINTR)
2063				retval = -ERESTARTSYS;
2064			tty = ERR_PTR(retval);
2065			goto out;
2066		}
2067		retval = tty_reopen(tty);
2068		if (retval < 0) {
2069			tty_unlock(tty);
2070			tty = ERR_PTR(retval);
2071		}
2072	} else { /* Returns with the tty_lock held for now */
2073		tty = tty_init_dev(driver, index);
2074		mutex_unlock(&tty_mutex);
2075	}
2076out:
2077	tty_driver_kref_put(driver);
2078	return tty;
2079}
2080
2081/**
2082 * tty_open - open a tty device
2083 * @inode: inode of device file
2084 * @filp: file pointer to tty
2085 *
2086 * tty_open() and tty_release() keep up the tty count that contains the number
2087 * of opens done on a tty. We cannot use the inode-count, as different inodes
2088 * might point to the same tty.
2089 *
2090 * Open-counting is needed for pty masters, as well as for keeping track of
2091 * serial lines: DTR is dropped when the last close happens.
2092 * (This is not done solely through tty->count, now.  - Ted 1/27/92)
2093 *
2094 * The termios state of a pty is reset on the first open so that settings don't
2095 * persist across reuse.
2096 *
2097 * Locking:
2098 *  * %tty_mutex protects tty, tty_lookup_driver() and tty_init_dev().
2099 *  * @tty->count should protect the rest.
2100 *  * ->siglock protects ->signal/->sighand
2101 *
2102 * Note: the tty_unlock/lock cases without a ref are only safe due to %tty_mutex
2103 */
2104static int tty_open(struct inode *inode, struct file *filp)
2105{
2106	struct tty_struct *tty;
2107	int noctty, retval;
2108	dev_t device = inode->i_rdev;
2109	unsigned saved_flags = filp->f_flags;
2110
2111	nonseekable_open(inode, filp);
2112
2113retry_open:
2114	retval = tty_alloc_file(filp);
2115	if (retval)
2116		return -ENOMEM;
2117
2118	tty = tty_open_current_tty(device, filp);
2119	if (!tty)
2120		tty = tty_open_by_driver(device, filp);
2121
2122	if (IS_ERR(tty)) {
2123		tty_free_file(filp);
2124		retval = PTR_ERR(tty);
2125		if (retval != -EAGAIN || signal_pending(current))
2126			return retval;
2127		schedule();
2128		goto retry_open;
2129	}
2130
2131	tty_add_file(tty, filp);
2132
2133	check_tty_count(tty, __func__);
2134	tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
2135
2136	if (tty->ops->open)
2137		retval = tty->ops->open(tty, filp);
2138	else
2139		retval = -ENODEV;
2140	filp->f_flags = saved_flags;
2141
2142	if (retval) {
2143		tty_debug_hangup(tty, "open error %d, releasing\n", retval);
2144
2145		tty_unlock(tty); /* need to call tty_release without BTM */
2146		tty_release(inode, filp);
2147		if (retval != -ERESTARTSYS)
2148			return retval;
2149
2150		if (signal_pending(current))
2151			return retval;
2152
2153		schedule();
2154		/*
2155		 * Need to reset f_op in case a hangup happened.
2156		 */
2157		if (tty_hung_up_p(filp))
2158			filp->f_op = &tty_fops;
2159		goto retry_open;
2160	}
2161	clear_bit(TTY_HUPPED, &tty->flags);
2162
2163	noctty = (filp->f_flags & O_NOCTTY) ||
2164		 (IS_ENABLED(CONFIG_VT) && device == MKDEV(TTY_MAJOR, 0)) ||
2165		 device == MKDEV(TTYAUX_MAJOR, 1) ||
2166		 (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
2167		  tty->driver->subtype == PTY_TYPE_MASTER);
2168	if (!noctty)
2169		tty_open_proc_set_tty(filp, tty);
2170	tty_unlock(tty);
2171	return 0;
2172}
2173
2174
2175/**
2176 * tty_poll - check tty status
2177 * @filp: file being polled
2178 * @wait: poll wait structures to update
2179 *
2180 * Call the line discipline polling method to obtain the poll status of the
2181 * device.
2182 *
2183 * Locking: locks called line discipline but ldisc poll method may be
2184 * re-entered freely by other callers.
2185 */
2186static __poll_t tty_poll(struct file *filp, poll_table *wait)
2187{
2188	struct tty_struct *tty = file_tty(filp);
2189	struct tty_ldisc *ld;
2190	__poll_t ret = 0;
2191
2192	if (tty_paranoia_check(tty, file_inode(filp), "tty_poll"))
2193		return 0;
2194
2195	ld = tty_ldisc_ref_wait(tty);
2196	if (!ld)
2197		return hung_up_tty_poll(filp, wait);
2198	if (ld->ops->poll)
2199		ret = ld->ops->poll(tty, filp, wait);
2200	tty_ldisc_deref(ld);
2201	return ret;
2202}
2203
2204static int __tty_fasync(int fd, struct file *filp, int on)
2205{
2206	struct tty_struct *tty = file_tty(filp);
2207	unsigned long flags;
2208	int retval = 0;
2209
2210	if (tty_paranoia_check(tty, file_inode(filp), "tty_fasync"))
2211		goto out;
2212
2213	if (on) {
2214		retval = file_f_owner_allocate(filp);
2215		if (retval)
2216			goto out;
2217	}
2218
2219	retval = fasync_helper(fd, filp, on, &tty->fasync);
2220	if (retval <= 0)
2221		goto out;
2222
2223	if (on) {
2224		enum pid_type type;
2225		struct pid *pid;
2226
2227		spin_lock_irqsave(&tty->ctrl.lock, flags);
2228		if (tty->ctrl.pgrp) {
2229			pid = tty->ctrl.pgrp;
2230			type = PIDTYPE_PGID;
2231		} else {
2232			pid = task_pid(current);
2233			type = PIDTYPE_TGID;
2234		}
2235		get_pid(pid);
2236		spin_unlock_irqrestore(&tty->ctrl.lock, flags);
2237		__f_setown(filp, pid, type, 0);
2238		put_pid(pid);
2239		retval = 0;
2240	}
2241out:
2242	return retval;
2243}
2244
2245static int tty_fasync(int fd, struct file *filp, int on)
2246{
2247	struct tty_struct *tty = file_tty(filp);
2248	int retval = -ENOTTY;
2249
2250	tty_lock(tty);
2251	if (!tty_hung_up_p(filp))
2252		retval = __tty_fasync(fd, filp, on);
2253	tty_unlock(tty);
2254
2255	return retval;
2256}
2257
2258static bool tty_legacy_tiocsti __read_mostly = IS_ENABLED(CONFIG_LEGACY_TIOCSTI);
2259/**
2260 * tiocsti - fake input character
2261 * @tty: tty to fake input into
2262 * @p: pointer to character
2263 *
2264 * Fake input to a tty device. Does the necessary locking and input management.
2265 *
2266 * FIXME: does not honour flow control ??
2267 *
2268 * Locking:
2269 *  * Called functions take tty_ldiscs_lock
2270 *  * current->signal->tty check is safe without locks
2271 */
2272static int tiocsti(struct tty_struct *tty, u8 __user *p)
2273{
2274	struct tty_ldisc *ld;
2275	u8 ch;
2276
2277	if (!tty_legacy_tiocsti && !capable(CAP_SYS_ADMIN))
2278		return -EIO;
2279
2280	if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
2281		return -EPERM;
2282	if (get_user(ch, p))
2283		return -EFAULT;
2284	tty_audit_tiocsti(tty, ch);
2285	ld = tty_ldisc_ref_wait(tty);
2286	if (!ld)
2287		return -EIO;
2288	tty_buffer_lock_exclusive(tty->port);
2289	if (ld->ops->receive_buf)
2290		ld->ops->receive_buf(tty, &ch, NULL, 1);
2291	tty_buffer_unlock_exclusive(tty->port);
2292	tty_ldisc_deref(ld);
2293	return 0;
2294}
2295
2296/**
2297 * tiocgwinsz - implement window query ioctl
2298 * @tty: tty
2299 * @arg: user buffer for result
2300 *
2301 * Copies the kernel idea of the window size into the user buffer.
2302 *
2303 * Locking: @tty->winsize_mutex is taken to ensure the winsize data is
2304 * consistent.
2305 */
2306static int tiocgwinsz(struct tty_struct *tty, struct winsize __user *arg)
2307{
2308	guard(mutex)(&tty->winsize_mutex);
2309
2310	if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
2311		return -EFAULT;
2312
2313	return 0;
2314}
2315
2316/**
2317 * tty_do_resize - resize event
2318 * @tty: tty being resized
2319 * @ws: new dimensions
2320 *
2321 * Update the termios variables and send the necessary signals to peform a
2322 * terminal resize correctly.
2323 */
2324int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
2325{
2326	struct pid *pgrp;
2327
2328	guard(mutex)(&tty->winsize_mutex);
2329
2330	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
2331		return 0;
2332
2333	/* Signal the foreground process group */
2334	pgrp = tty_get_pgrp(tty);
2335	if (pgrp)
2336		kill_pgrp(pgrp, SIGWINCH, 1);
2337	put_pid(pgrp);
2338
2339	tty->winsize = *ws;
2340
2341	return 0;
2342}
2343EXPORT_SYMBOL(tty_do_resize);
2344
2345/**
2346 * tiocswinsz - implement window size set ioctl
2347 * @tty: tty side of tty
2348 * @arg: user buffer for result
2349 *
2350 * Copies the user idea of the window size to the kernel. Traditionally this is
2351 * just advisory information but for the Linux console it actually has driver
2352 * level meaning and triggers a VC resize.
2353 *
2354 * Locking:
2355 *	Driver dependent. The default do_resize method takes the tty termios
2356 *	mutex and ctrl.lock. The console takes its own lock then calls into the
2357 *	default method.
2358 */
2359static int tiocswinsz(struct tty_struct *tty, struct winsize __user *arg)
2360{
2361	struct winsize tmp_ws;
2362
2363	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
2364		return -EFAULT;
2365
2366	if (tty->ops->resize)
2367		return tty->ops->resize(tty, &tmp_ws);
2368	else
2369		return tty_do_resize(tty, &tmp_ws);
2370}
2371
2372/**
2373 * tioccons - allow admin to move logical console
2374 * @file: the file to become console
2375 *
2376 * Allow the administrator to move the redirected console device.
2377 *
2378 * Locking: uses redirect_lock to guard the redirect information
2379 */
2380static int tioccons(struct file *file)
2381{
2382	if (!capable(CAP_SYS_ADMIN))
2383		return -EPERM;
2384	if (file->f_op->write_iter == redirected_tty_write) {
2385		struct file *f;
2386
2387		spin_lock(&redirect_lock);
2388		f = redirect;
2389		redirect = NULL;
2390		spin_unlock(&redirect_lock);
2391		if (f)
2392			fput(f);
2393		return 0;
2394	}
2395	if (file->f_op->write_iter != tty_write)
2396		return -ENOTTY;
2397	if (!(file->f_mode & FMODE_WRITE))
2398		return -EBADF;
2399	if (!(file->f_mode & FMODE_CAN_WRITE))
2400		return -EINVAL;
2401
2402	guard(spinlock)(&redirect_lock);
2403
2404	if (redirect)
2405		return -EBUSY;
2406
2407	redirect = get_file(file);
2408
2409	return 0;
2410}
2411
2412/**
2413 * tiocsetd - set line discipline
2414 * @tty: tty device
2415 * @p: pointer to user data
2416 *
2417 * Set the line discipline according to user request.
2418 *
2419 * Locking: see tty_set_ldisc(), this function is just a helper
2420 */
2421static int tiocsetd(struct tty_struct *tty, int __user *p)
2422{
2423	int disc;
2424	int ret;
2425
2426	if (get_user(disc, p))
2427		return -EFAULT;
2428
2429	ret = tty_set_ldisc(tty, disc);
2430
2431	return ret;
2432}
2433
2434/**
2435 * tiocgetd - get line discipline
2436 * @tty: tty device
2437 * @p: pointer to user data
2438 *
2439 * Retrieves the line discipline id directly from the ldisc.
2440 *
2441 * Locking: waits for ldisc reference (in case the line discipline is changing
2442 * or the @tty is being hungup)
2443 */
2444static int tiocgetd(struct tty_struct *tty, int __user *p)
2445{
2446	struct tty_ldisc *ld;
2447	int ret;
2448
2449	ld = tty_ldisc_ref_wait(tty);
2450	if (!ld)
2451		return -EIO;
2452	ret = put_user(ld->ops->num, p);
2453	tty_ldisc_deref(ld);
2454	return ret;
2455}
2456
2457/**
2458 * send_break - performed time break
2459 * @tty: device to break on
2460 * @duration: timeout in mS
2461 *
2462 * Perform a timed break on hardware that lacks its own driver level timed
2463 * break functionality.
2464 *
2465 * Locking:
2466 *	@tty->atomic_write_lock serializes
2467 */
2468static int send_break(struct tty_struct *tty, unsigned int duration)
2469{
2470	int retval;
2471
2472	if (tty->ops->break_ctl == NULL)
2473		return 0;
2474
2475	if (tty->driver->flags & TTY_DRIVER_HARDWARE_BREAK)
2476		return tty->ops->break_ctl(tty, duration);
2477
2478	/* Do the work ourselves */
2479	if (tty_write_lock(tty, false) < 0)
2480		return -EINTR;
2481
2482	retval = tty->ops->break_ctl(tty, -1);
2483	if (!retval) {
2484		msleep_interruptible(duration);
2485		retval = tty->ops->break_ctl(tty, 0);
2486	} else if (retval == -EOPNOTSUPP) {
2487		/* some drivers can tell only dynamically */
2488		retval = 0;
2489	}
2490	tty_write_unlock(tty);
2491
2492	if (signal_pending(current))
2493		retval = -EINTR;
2494
2495	return retval;
2496}
2497
2498/**
2499 * tty_get_tiocm - get tiocm status register
2500 * @tty: tty device
2501 *
2502 * Obtain the modem status bits from the tty driver if the feature
2503 * is supported.
2504 */
2505int tty_get_tiocm(struct tty_struct *tty)
2506{
2507	int retval = -ENOTTY;
2508
2509	if (tty->ops->tiocmget)
2510		retval = tty->ops->tiocmget(tty);
2511
2512	return retval;
2513}
2514EXPORT_SYMBOL_GPL(tty_get_tiocm);
2515
2516/**
2517 * tty_tiocmget - get modem status
2518 * @tty: tty device
2519 * @p: pointer to result
2520 *
2521 * Obtain the modem status bits from the tty driver if the feature is
2522 * supported. Return -%ENOTTY if it is not available.
2523 *
2524 * Locking: none (up to the driver)
2525 */
2526static int tty_tiocmget(struct tty_struct *tty, int __user *p)
2527{
2528	int retval;
2529
2530	retval = tty_get_tiocm(tty);
2531	if (retval >= 0)
2532		retval = put_user(retval, p);
2533
2534	return retval;
2535}
2536
2537/**
2538 * tty_tiocmset - set modem status
2539 * @tty: tty device
2540 * @cmd: command - clear bits, set bits or set all
2541 * @p: pointer to desired bits
2542 *
2543 * Set the modem status bits from the tty driver if the feature
2544 * is supported. Return -%ENOTTY if it is not available.
2545 *
2546 * Locking: none (up to the driver)
2547 */
2548static int tty_tiocmset(struct tty_struct *tty, unsigned int cmd,
2549	     unsigned __user *p)
2550{
2551	int retval;
2552	unsigned int set, clear, val;
2553
2554	if (tty->ops->tiocmset == NULL)
2555		return -ENOTTY;
2556
2557	retval = get_user(val, p);
2558	if (retval)
2559		return retval;
2560	set = clear = 0;
2561	switch (cmd) {
2562	case TIOCMBIS:
2563		set = val;
2564		break;
2565	case TIOCMBIC:
2566		clear = val;
2567		break;
2568	case TIOCMSET:
2569		set = val;
2570		clear = ~val;
2571		break;
2572	}
2573	set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
2574	clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
2575	return tty->ops->tiocmset(tty, set, clear);
2576}
2577
2578/**
2579 * tty_get_icount - get tty statistics
2580 * @tty: tty device
2581 * @icount: output parameter
2582 *
2583 * Gets a copy of the @tty's icount statistics.
2584 *
2585 * Locking: none (up to the driver)
2586 */
2587int tty_get_icount(struct tty_struct *tty,
2588		   struct serial_icounter_struct *icount)
2589{
2590	memset(icount, 0, sizeof(*icount));
2591
2592	if (tty->ops->get_icount)
2593		return tty->ops->get_icount(tty, icount);
2594	else
2595		return -ENOTTY;
2596}
2597EXPORT_SYMBOL_GPL(tty_get_icount);
2598
2599static int tty_tiocgicount(struct tty_struct *tty, void __user *arg)
2600{
2601	struct serial_icounter_struct icount;
2602	int retval;
2603
2604	retval = tty_get_icount(tty, &icount);
2605	if (retval != 0)
2606		return retval;
2607
2608	if (copy_to_user(arg, &icount, sizeof(icount)))
2609		return -EFAULT;
2610	return 0;
2611}
2612
2613static int tty_set_serial(struct tty_struct *tty, struct serial_struct *ss)
2614{
2615	int flags;
2616
2617	flags = ss->flags & ASYNC_DEPRECATED;
2618
2619	if (flags)
2620		pr_warn_ratelimited("%s: '%s' is using deprecated serial flags (with no effect): %.8x\n",
2621				__func__, current->comm, flags);
2622
2623	if (!tty->ops->set_serial)
2624		return -ENOTTY;
2625
2626	return tty->ops->set_serial(tty, ss);
2627}
2628
2629static int tty_tiocsserial(struct tty_struct *tty, struct serial_struct __user *ss)
2630{
2631	struct serial_struct v;
2632
2633	if (copy_from_user(&v, ss, sizeof(*ss)))
2634		return -EFAULT;
2635
2636	return tty_set_serial(tty, &v);
2637}
2638
2639static int tty_tiocgserial(struct tty_struct *tty, struct serial_struct __user *ss)
2640{
2641	struct serial_struct v;
2642	int err;
2643
2644	memset(&v, 0, sizeof(v));
2645	if (!tty->ops->get_serial)
2646		return -ENOTTY;
2647	err = tty->ops->get_serial(tty, &v);
2648	if (!err && copy_to_user(ss, &v, sizeof(v)))
2649		err = -EFAULT;
2650	return err;
2651}
2652
2653/*
2654 * if pty, return the slave side (real_tty)
2655 * otherwise, return self
2656 */
2657static struct tty_struct *tty_pair_get_tty(struct tty_struct *tty)
2658{
2659	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
2660	    tty->driver->subtype == PTY_TYPE_MASTER)
2661		tty = tty->link;
2662	return tty;
2663}
2664
2665/*
2666 * Split this up, as gcc can choke on it otherwise..
2667 */
2668long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
2669{
2670	struct tty_struct *tty = file_tty(file);
2671	struct tty_struct *real_tty;
2672	void __user *p = (void __user *)arg;
2673	int retval;
2674	struct tty_ldisc *ld;
2675
2676	if (tty_paranoia_check(tty, file_inode(file), "tty_ioctl"))
2677		return -EINVAL;
2678
2679	real_tty = tty_pair_get_tty(tty);
2680
2681	/*
2682	 * Factor out some common prep work
2683	 */
2684	switch (cmd) {
2685	case TIOCSETD:
2686	case TIOCSBRK:
2687	case TIOCCBRK:
2688	case TCSBRK:
2689	case TCSBRKP:
2690		retval = tty_check_change(tty);
2691		if (retval)
2692			return retval;
2693		if (cmd != TIOCCBRK) {
2694			tty_wait_until_sent(tty, 0);
2695			if (signal_pending(current))
2696				return -EINTR;
2697		}
2698		break;
2699	}
2700
2701	/*
2702	 *	Now do the stuff.
2703	 */
2704	switch (cmd) {
2705	case TIOCSTI:
2706		return tiocsti(tty, p);
2707	case TIOCGWINSZ:
2708		return tiocgwinsz(real_tty, p);
2709	case TIOCSWINSZ:
2710		return tiocswinsz(real_tty, p);
2711	case TIOCCONS:
2712		return real_tty != tty ? -EINVAL : tioccons(file);
2713	case TIOCEXCL:
2714		set_bit(TTY_EXCLUSIVE, &tty->flags);
2715		return 0;
2716	case TIOCNXCL:
2717		clear_bit(TTY_EXCLUSIVE, &tty->flags);
2718		return 0;
2719	case TIOCGEXCL:
2720	{
2721		int excl = test_bit(TTY_EXCLUSIVE, &tty->flags);
2722
2723		return put_user(excl, (int __user *)p);
2724	}
2725	case TIOCGETD:
2726		return tiocgetd(tty, p);
2727	case TIOCSETD:
2728		return tiocsetd(tty, p);
2729	case TIOCVHANGUP:
2730		if (!capable(CAP_SYS_ADMIN))
2731			return -EPERM;
2732		tty_vhangup(tty);
2733		return 0;
2734	case TIOCGDEV:
2735	{
2736		unsigned int ret = new_encode_dev(tty_devnum(real_tty));
2737
2738		return put_user(ret, (unsigned int __user *)p);
2739	}
2740	/*
2741	 * Break handling
2742	 */
2743	case TIOCSBRK:	/* Turn break on, unconditionally */
2744		if (tty->ops->break_ctl)
2745			return tty->ops->break_ctl(tty, -1);
2746		return 0;
2747	case TIOCCBRK:	/* Turn break off, unconditionally */
2748		if (tty->ops->break_ctl)
2749			return tty->ops->break_ctl(tty, 0);
2750		return 0;
2751	case TCSBRK:   /* SVID version: non-zero arg --> no break */
2752		/* non-zero arg means wait for all output data
2753		 * to be sent (performed above) but don't send break.
2754		 * This is used by the tcdrain() termios function.
2755		 */
2756		if (!arg)
2757			return send_break(tty, 250);
2758		return 0;
2759	case TCSBRKP:	/* support for POSIX tcsendbreak() */
2760		return send_break(tty, arg ? arg*100 : 250);
2761
2762	case TIOCMGET:
2763		return tty_tiocmget(tty, p);
2764	case TIOCMSET:
2765	case TIOCMBIC:
2766	case TIOCMBIS:
2767		return tty_tiocmset(tty, cmd, p);
2768	case TIOCGICOUNT:
2769		return tty_tiocgicount(tty, p);
2770	case TCFLSH:
2771		switch (arg) {
2772		case TCIFLUSH:
2773		case TCIOFLUSH:
2774		/* flush tty buffer and allow ldisc to process ioctl */
2775			tty_buffer_flush(tty, NULL);
2776			break;
2777		}
2778		break;
2779	case TIOCSSERIAL:
2780		return tty_tiocsserial(tty, p);
2781	case TIOCGSERIAL:
2782		return tty_tiocgserial(tty, p);
2783	case TIOCGPTPEER:
2784		/* Special because the struct file is needed */
2785		return ptm_open_peer(file, tty, (int)arg);
2786	default:
2787		retval = tty_jobctrl_ioctl(tty, real_tty, file, cmd, arg);
2788		if (retval != -ENOIOCTLCMD)
2789			return retval;
2790	}
2791	if (tty->ops->ioctl) {
2792		retval = tty->ops->ioctl(tty, cmd, arg);
2793		if (retval != -ENOIOCTLCMD)
2794			return retval;
2795	}
2796	ld = tty_ldisc_ref_wait(tty);
2797	if (!ld)
2798		return hung_up_tty_ioctl(file, cmd, arg);
2799	retval = -EINVAL;
2800	if (ld->ops->ioctl) {
2801		retval = ld->ops->ioctl(tty, cmd, arg);
2802		if (retval == -ENOIOCTLCMD)
2803			retval = -ENOTTY;
2804	}
2805	tty_ldisc_deref(ld);
2806	return retval;
2807}
2808
2809#ifdef CONFIG_COMPAT
2810
2811struct serial_struct32 {
2812	compat_int_t    type;
2813	compat_int_t    line;
2814	compat_uint_t   port;
2815	compat_int_t    irq;
2816	compat_int_t    flags;
2817	compat_int_t    xmit_fifo_size;
2818	compat_int_t    custom_divisor;
2819	compat_int_t    baud_base;
2820	unsigned short  close_delay;
2821	char    io_type;
2822	char    reserved_char;
2823	compat_int_t    hub6;
2824	unsigned short  closing_wait; /* time to wait before closing */
2825	unsigned short  closing_wait2; /* no longer used... */
2826	compat_uint_t   iomem_base;
2827	unsigned short  iomem_reg_shift;
2828	unsigned int    port_high;
2829	/* compat_ulong_t  iomap_base FIXME */
2830	compat_int_t    reserved;
2831};
2832
2833static int compat_tty_tiocsserial(struct tty_struct *tty,
2834		struct serial_struct32 __user *ss)
2835{
2836	struct serial_struct32 v32;
2837	struct serial_struct v;
2838
2839	if (copy_from_user(&v32, ss, sizeof(*ss)))
2840		return -EFAULT;
2841
2842	memcpy(&v, &v32, offsetof(struct serial_struct32, iomem_base));
2843	v.iomem_base = compat_ptr(v32.iomem_base);
2844	v.iomem_reg_shift = v32.iomem_reg_shift;
2845	v.port_high = v32.port_high;
2846	v.iomap_base = 0;
2847
2848	return tty_set_serial(tty, &v);
2849}
2850
2851static int compat_tty_tiocgserial(struct tty_struct *tty,
2852			struct serial_struct32 __user *ss)
2853{
2854	struct serial_struct32 v32;
2855	struct serial_struct v;
2856	int err;
2857
2858	memset(&v, 0, sizeof(v));
2859	memset(&v32, 0, sizeof(v32));
2860
2861	if (!tty->ops->get_serial)
2862		return -ENOTTY;
2863	err = tty->ops->get_serial(tty, &v);
2864	if (!err) {
2865		memcpy(&v32, &v, offsetof(struct serial_struct32, iomem_base));
2866		v32.iomem_base = (unsigned long)v.iomem_base >> 32 ?
2867			0xfffffff : ptr_to_compat(v.iomem_base);
2868		v32.iomem_reg_shift = v.iomem_reg_shift;
2869		v32.port_high = v.port_high;
2870		if (copy_to_user(ss, &v32, sizeof(v32)))
2871			err = -EFAULT;
2872	}
2873	return err;
2874}
2875static long tty_compat_ioctl(struct file *file, unsigned int cmd,
2876				unsigned long arg)
2877{
2878	struct tty_struct *tty = file_tty(file);
2879	struct tty_ldisc *ld;
2880	int retval = -ENOIOCTLCMD;
2881
2882	switch (cmd) {
2883	case TIOCOUTQ:
2884	case TIOCSTI:
2885	case TIOCGWINSZ:
2886	case TIOCSWINSZ:
2887	case TIOCGEXCL:
2888	case TIOCGETD:
2889	case TIOCSETD:
2890	case TIOCGDEV:
2891	case TIOCMGET:
2892	case TIOCMSET:
2893	case TIOCMBIC:
2894	case TIOCMBIS:
2895	case TIOCGICOUNT:
2896	case TIOCGPGRP:
2897	case TIOCSPGRP:
2898	case TIOCGSID:
2899	case TIOCSERGETLSR:
2900	case TIOCGRS485:
2901	case TIOCSRS485:
2902#ifdef TIOCGETP
2903	case TIOCGETP:
2904	case TIOCSETP:
2905	case TIOCSETN:
2906#endif
2907#ifdef TIOCGETC
2908	case TIOCGETC:
2909	case TIOCSETC:
2910#endif
2911#ifdef TIOCGLTC
2912	case TIOCGLTC:
2913	case TIOCSLTC:
2914#endif
2915	case TCSETSF:
2916	case TCSETSW:
2917	case TCSETS:
2918	case TCGETS:
2919#ifdef TCGETS2
2920	case TCGETS2:
2921	case TCSETSF2:
2922	case TCSETSW2:
2923	case TCSETS2:
2924#endif
2925	case TCGETA:
2926	case TCSETAF:
2927	case TCSETAW:
2928	case TCSETA:
2929	case TIOCGLCKTRMIOS:
2930	case TIOCSLCKTRMIOS:
2931#ifdef TCGETX
2932	case TCGETX:
2933	case TCSETX:
2934	case TCSETXW:
2935	case TCSETXF:
2936#endif
2937	case TIOCGSOFTCAR:
2938	case TIOCSSOFTCAR:
2939
2940	case PPPIOCGCHAN:
2941	case PPPIOCGUNIT:
2942		return tty_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
2943	case TIOCCONS:
2944	case TIOCEXCL:
2945	case TIOCNXCL:
2946	case TIOCVHANGUP:
2947	case TIOCSBRK:
2948	case TIOCCBRK:
2949	case TCSBRK:
2950	case TCSBRKP:
2951	case TCFLSH:
2952	case TIOCGPTPEER:
2953	case TIOCNOTTY:
2954	case TIOCSCTTY:
2955	case TCXONC:
2956	case TIOCMIWAIT:
2957	case TIOCSERCONFIG:
2958		return tty_ioctl(file, cmd, arg);
2959	}
2960
2961	if (tty_paranoia_check(tty, file_inode(file), "tty_ioctl"))
2962		return -EINVAL;
2963
2964	switch (cmd) {
2965	case TIOCSSERIAL:
2966		return compat_tty_tiocsserial(tty, compat_ptr(arg));
2967	case TIOCGSERIAL:
2968		return compat_tty_tiocgserial(tty, compat_ptr(arg));
2969	}
2970	if (tty->ops->compat_ioctl) {
2971		retval = tty->ops->compat_ioctl(tty, cmd, arg);
2972		if (retval != -ENOIOCTLCMD)
2973			return retval;
2974	}
2975
2976	ld = tty_ldisc_ref_wait(tty);
2977	if (!ld)
2978		return hung_up_tty_compat_ioctl(file, cmd, arg);
2979	if (ld->ops->compat_ioctl)
2980		retval = ld->ops->compat_ioctl(tty, cmd, arg);
2981	if (retval == -ENOIOCTLCMD && ld->ops->ioctl)
2982		retval = ld->ops->ioctl(tty, (unsigned long)compat_ptr(cmd),
2983				arg);
2984	tty_ldisc_deref(ld);
2985
2986	return retval;
2987}
2988#endif
2989
2990static int this_tty(const void *t, struct file *file, unsigned fd)
2991{
2992	if (likely(file->f_op->read_iter != tty_read))
2993		return 0;
2994	return file_tty(file) != t ? 0 : fd + 1;
2995}
2996
2997/*
2998 * This implements the "Secure Attention Key" ---  the idea is to
2999 * prevent trojan horses by killing all processes associated with this
3000 * tty when the user hits the "Secure Attention Key".  Required for
3001 * super-paranoid applications --- see the Orange Book for more details.
3002 *
3003 * This code could be nicer; ideally it should send a HUP, wait a few
3004 * seconds, then send a INT, and then a KILL signal.  But you then
3005 * have to coordinate with the init process, since all processes associated
3006 * with the current tty must be dead before the new getty is allowed
3007 * to spawn.
3008 *
3009 * Now, if it would be correct ;-/ The current code has a nasty hole -
3010 * it doesn't catch files in flight. We may send the descriptor to ourselves
3011 * via AF_UNIX socket, close it and later fetch from socket. FIXME.
3012 *
3013 * Nasty bug: do_SAK is being called in interrupt context.  This can
3014 * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
3015 */
3016void __do_SAK(struct tty_struct *tty)
3017{
3018	struct task_struct *g, *p;
3019	struct pid *session;
3020	int i;
3021
3022	scoped_guard(spinlock_irqsave, &tty->ctrl.lock)
3023		session = get_pid(tty->ctrl.session);
3024
3025	tty_ldisc_flush(tty);
3026
3027	tty_driver_flush_buffer(tty);
3028
3029	read_lock(&tasklist_lock);
3030	/* Kill the entire session */
3031	do_each_pid_task(session, PIDTYPE_SID, p) {
3032		tty_notice(tty, "SAK: killed process %d (%s): by session\n",
3033			   task_pid_nr(p), p->comm);
3034		group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID);
3035	} while_each_pid_task(session, PIDTYPE_SID, p);
3036
3037	/* Now kill any processes that happen to have the tty open */
3038	for_each_process_thread(g, p) {
3039		if (p->signal->tty == tty) {
3040			tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n",
3041				   task_pid_nr(p), p->comm);
3042			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3043					PIDTYPE_SID);
3044			continue;
3045		}
3046		guard(task_lock)(p);
3047		i = iterate_fd(p->files, 0, this_tty, tty);
3048		if (i != 0) {
3049			tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n",
3050				   task_pid_nr(p), p->comm, i - 1);
3051			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3052					PIDTYPE_SID);
3053		}
3054	}
3055	read_unlock(&tasklist_lock);
3056	put_pid(session);
3057}
3058
3059static void do_SAK_work(struct work_struct *work)
3060{
3061	struct tty_struct *tty =
3062		container_of(work, struct tty_struct, SAK_work);
3063	__do_SAK(tty);
3064}
3065
3066/*
3067 * The tq handling here is a little racy - tty->SAK_work may already be queued.
3068 * Fortunately we don't need to worry, because if ->SAK_work is already queued,
3069 * the values which we write to it will be identical to the values which it
3070 * already has. --akpm
3071 */
3072void do_SAK(struct tty_struct *tty)
3073{
3074	if (!tty)
3075		return;
3076	schedule_work(&tty->SAK_work);
3077}
3078EXPORT_SYMBOL(do_SAK);
3079
3080/* Must put_device() after it's unused! */
3081static struct device *tty_get_device(struct tty_struct *tty)
3082{
3083	dev_t devt = tty_devnum(tty);
3084
3085	return class_find_device_by_devt(&tty_class, devt);
3086}
3087
3088
3089/**
3090 * alloc_tty_struct - allocate a new tty
3091 * @driver: driver which will handle the returned tty
3092 * @idx: minor of the tty
3093 *
3094 * This subroutine allocates and initializes a tty structure.
3095 *
3096 * Locking: none - @tty in question is not exposed at this point
3097 */
3098struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
3099{
3100	struct tty_struct *tty;
3101
3102	tty = kzalloc(sizeof(*tty), GFP_KERNEL_ACCOUNT);
3103	if (!tty)
3104		return NULL;
3105
3106	kref_init(&tty->kref);
3107	if (tty_ldisc_init(tty)) {
3108		kfree(tty);
3109		return NULL;
3110	}
3111	tty->ctrl.session = NULL;
3112	tty->ctrl.pgrp = NULL;
3113	mutex_init(&tty->legacy_mutex);
3114	mutex_init(&tty->throttle_mutex);
3115	init_rwsem(&tty->termios_rwsem);
3116	mutex_init(&tty->winsize_mutex);
3117	init_ldsem(&tty->ldisc_sem);
3118	init_waitqueue_head(&tty->write_wait);
3119	init_waitqueue_head(&tty->read_wait);
3120	INIT_WORK(&tty->hangup_work, do_tty_hangup);
3121	mutex_init(&tty->atomic_write_lock);
3122	spin_lock_init(&tty->ctrl.lock);
3123	spin_lock_init(&tty->flow.lock);
3124	spin_lock_init(&tty->files_lock);
3125	INIT_LIST_HEAD(&tty->tty_files);
3126	INIT_WORK(&tty->SAK_work, do_SAK_work);
3127
3128	tty->driver = driver;
3129	tty->ops = driver->ops;
3130	tty->index = idx;
3131	tty_line_name(driver, idx, tty->name);
3132	tty->dev = tty_get_device(tty);
3133
3134	return tty;
3135}
3136
3137/**
3138 * tty_put_char - write one character to a tty
3139 * @tty: tty
3140 * @ch: character to write
3141 *
3142 * Write one byte to the @tty using the provided @tty->ops->put_char() method
3143 * if present.
3144 *
3145 * Note: the specific put_char operation in the driver layer may go
3146 * away soon. Don't call it directly, use this method
3147 *
3148 * Return: the number of characters successfully output.
3149 */
3150int tty_put_char(struct tty_struct *tty, u8 ch)
3151{
3152	if (tty->ops->put_char)
3153		return tty->ops->put_char(tty, ch);
3154	return tty->ops->write(tty, &ch, 1);
3155}
3156EXPORT_SYMBOL_GPL(tty_put_char);
3157
3158static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
3159		unsigned int index, unsigned int count)
3160{
3161	int err;
3162
3163	/* init here, since reused cdevs cause crashes */
3164	driver->cdevs[index] = cdev_alloc();
3165	if (!driver->cdevs[index])
3166		return -ENOMEM;
3167	driver->cdevs[index]->ops = &tty_fops;
3168	driver->cdevs[index]->owner = driver->owner;
3169	err = cdev_add(driver->cdevs[index], dev, count);
3170	if (err)
3171		kobject_put(&driver->cdevs[index]->kobj);
3172	return err;
3173}
3174
3175/**
3176 * tty_register_device - register a tty device
3177 * @driver: the tty driver that describes the tty device
3178 * @index: the index in the tty driver for this tty device
3179 * @device: a struct device that is associated with this tty device.
3180 *	This field is optional, if there is no known struct device
3181 *	for this tty device it can be set to NULL safely.
3182 *
3183 * This call is required to be made to register an individual tty device
3184 * if the tty driver's flags have the %TTY_DRIVER_DYNAMIC_DEV bit set.  If
3185 * that bit is not set, this function should not be called by a tty
3186 * driver.
3187 *
3188 * Locking: ??
3189 *
3190 * Return: A pointer to the struct device for this tty device (or
3191 * ERR_PTR(-EFOO) on error).
3192 */
3193struct device *tty_register_device(struct tty_driver *driver, unsigned index,
3194				   struct device *device)
3195{
3196	return tty_register_device_attr(driver, index, device, NULL, NULL);
3197}
3198EXPORT_SYMBOL(tty_register_device);
3199
3200static void tty_device_create_release(struct device *dev)
3201{
3202	dev_dbg(dev, "releasing...\n");
3203	kfree(dev);
3204}
3205
3206/**
3207 * tty_register_device_attr - register a tty device
3208 * @driver: the tty driver that describes the tty device
3209 * @index: the index in the tty driver for this tty device
3210 * @device: a struct device that is associated with this tty device.
3211 *	This field is optional, if there is no known struct device
3212 *	for this tty device it can be set to %NULL safely.
3213 * @drvdata: Driver data to be set to device.
3214 * @attr_grp: Attribute group to be set on device.
3215 *
3216 * This call is required to be made to register an individual tty device if the
3217 * tty driver's flags have the %TTY_DRIVER_DYNAMIC_DEV bit set. If that bit is
3218 * not set, this function should not be called by a tty driver.
3219 *
3220 * Locking: ??
3221 *
3222 * Return: A pointer to the struct device for this tty device (or
3223 * ERR_PTR(-EFOO) on error).
3224 */
3225struct device *tty_register_device_attr(struct tty_driver *driver,
3226				   unsigned index, struct device *device,
3227				   void *drvdata,
3228				   const struct attribute_group **attr_grp)
3229{
3230	char name[64];
3231	dev_t devt = MKDEV(driver->major, driver->minor_start) + index;
3232	struct ktermios *tp;
3233	struct device *dev;
3234	int retval;
3235
3236	if (index >= driver->num) {
3237		pr_err("%s: Attempt to register invalid tty line number (%d)\n",
3238		       driver->name, index);
3239		return ERR_PTR(-EINVAL);
3240	}
3241
3242	if (driver->type == TTY_DRIVER_TYPE_PTY)
3243		pty_line_name(driver, index, name);
3244	else
3245		tty_line_name(driver, index, name);
3246
3247	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
3248	if (!dev)
3249		return ERR_PTR(-ENOMEM);
3250
3251	dev->devt = devt;
3252	dev->class = &tty_class;
3253	dev->parent = device;
3254	dev->release = tty_device_create_release;
3255	dev_set_name(dev, "%s", name);
3256	dev->groups = attr_grp;
3257	dev_set_drvdata(dev, drvdata);
3258
3259	dev_set_uevent_suppress(dev, 1);
3260
3261	retval = device_register(dev);
3262	if (retval)
3263		goto err_put;
3264
3265	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
3266		/*
3267		 * Free any saved termios data so that the termios state is
3268		 * reset when reusing a minor number.
3269		 */
3270		tp = driver->termios[index];
3271		if (tp) {
3272			driver->termios[index] = NULL;
3273			kfree(tp);
3274		}
3275
3276		retval = tty_cdev_add(driver, devt, index, 1);
3277		if (retval)
3278			goto err_del;
3279	}
3280
3281	dev_set_uevent_suppress(dev, 0);
3282	kobject_uevent(&dev->kobj, KOBJ_ADD);
3283
3284	return dev;
3285
3286err_del:
3287	device_del(dev);
3288err_put:
3289	put_device(dev);
3290
3291	return ERR_PTR(retval);
3292}
3293EXPORT_SYMBOL_GPL(tty_register_device_attr);
3294
3295/**
3296 * tty_unregister_device - unregister a tty device
3297 * @driver: the tty driver that describes the tty device
3298 * @index: the index in the tty driver for this tty device
3299 *
3300 * If a tty device is registered with a call to tty_register_device() then
3301 * this function must be called when the tty device is gone.
3302 *
3303 * Locking: ??
3304 */
3305void tty_unregister_device(struct tty_driver *driver, unsigned index)
3306{
3307	device_destroy(&tty_class, MKDEV(driver->major, driver->minor_start) + index);
3308	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
3309		cdev_del(driver->cdevs[index]);
3310		driver->cdevs[index] = NULL;
3311	}
3312}
3313EXPORT_SYMBOL(tty_unregister_device);
3314
3315/**
3316 * __tty_alloc_driver - allocate tty driver
3317 * @lines: count of lines this driver can handle at most
3318 * @owner: module which is responsible for this driver
3319 * @flags: some of enum tty_driver_flag, will be set in driver->flags
3320 *
3321 * This should not be called directly, tty_alloc_driver() should be used
3322 * instead.
3323 *
3324 * Returns: struct tty_driver or a PTR-encoded error (use IS_ERR() and friends).
3325 */
3326struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner,
3327		unsigned long flags)
3328{
3329	struct tty_driver *driver;
3330	unsigned int cdevs = 1;
3331	int err;
3332
3333	if (!lines || (flags & TTY_DRIVER_UNNUMBERED_NODE && lines > 1))
3334		return ERR_PTR(-EINVAL);
3335
3336	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
3337	if (!driver)
3338		return ERR_PTR(-ENOMEM);
3339
3340	kref_init(&driver->kref);
3341	driver->num = lines;
3342	driver->owner = owner;
3343	driver->flags = flags;
3344
3345	if (!(flags & TTY_DRIVER_DEVPTS_MEM)) {
3346		driver->ttys = kcalloc(lines, sizeof(*driver->ttys),
3347				GFP_KERNEL);
3348		driver->termios = kcalloc(lines, sizeof(*driver->termios),
3349				GFP_KERNEL);
3350		if (!driver->ttys || !driver->termios) {
3351			err = -ENOMEM;
3352			goto err_free_all;
3353		}
3354	}
3355
3356	if (!(flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
3357		driver->ports = kcalloc(lines, sizeof(*driver->ports),
3358				GFP_KERNEL);
3359		if (!driver->ports) {
3360			err = -ENOMEM;
3361			goto err_free_all;
3362		}
3363		cdevs = lines;
3364	}
3365
3366	driver->cdevs = kcalloc(cdevs, sizeof(*driver->cdevs), GFP_KERNEL);
3367	if (!driver->cdevs) {
3368		err = -ENOMEM;
3369		goto err_free_all;
3370	}
3371
3372	return driver;
3373err_free_all:
3374	kfree(driver->ports);
3375	kfree(driver->ttys);
3376	kfree(driver->termios);
3377	kfree(driver->cdevs);
3378	kfree(driver);
3379	return ERR_PTR(err);
3380}
3381EXPORT_SYMBOL(__tty_alloc_driver);
3382
3383static void destruct_tty_driver(struct kref *kref)
3384{
3385	struct tty_driver *driver = container_of(kref, struct tty_driver, kref);
3386	int i;
3387	struct ktermios *tp;
3388
3389	if (driver->flags & TTY_DRIVER_INSTALLED) {
3390		for (i = 0; i < driver->num; i++) {
3391			tp = driver->termios[i];
3392			if (tp) {
3393				driver->termios[i] = NULL;
3394				kfree(tp);
3395			}
3396			if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV))
3397				tty_unregister_device(driver, i);
3398		}
3399		proc_tty_unregister_driver(driver);
3400		if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)
3401			cdev_del(driver->cdevs[0]);
3402	}
3403	kfree(driver->cdevs);
3404	kfree(driver->ports);
3405	kfree(driver->termios);
3406	kfree(driver->ttys);
3407	kfree(driver);
3408}
3409
3410/**
3411 * tty_driver_kref_put - drop a reference to a tty driver
3412 * @driver: driver of which to drop the reference
3413 *
3414 * The final put will destroy and free up the driver.
3415 */
3416void tty_driver_kref_put(struct tty_driver *driver)
3417{
3418	kref_put(&driver->kref, destruct_tty_driver);
3419}
3420EXPORT_SYMBOL(tty_driver_kref_put);
3421
3422/**
3423 * tty_register_driver - register a tty driver
3424 * @driver: driver to register
3425 *
3426 * Called by a tty driver to register itself.
3427 */
3428int tty_register_driver(struct tty_driver *driver)
3429{
3430	int error;
3431	int i;
3432	dev_t dev;
3433	struct device *d;
3434
3435	if (!driver->major) {
3436		error = alloc_chrdev_region(&dev, driver->minor_start,
3437						driver->num, driver->name);
3438		if (!error) {
3439			driver->major = MAJOR(dev);
3440			driver->minor_start = MINOR(dev);
3441		}
3442	} else {
3443		dev = MKDEV(driver->major, driver->minor_start);
3444		error = register_chrdev_region(dev, driver->num, driver->name);
3445	}
3446	if (error < 0)
3447		goto err;
3448
3449	if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC) {
3450		error = tty_cdev_add(driver, dev, 0, driver->num);
3451		if (error)
3452			goto err_unreg_char;
3453	}
3454
3455	scoped_guard(mutex, &tty_mutex)
3456		list_add(&driver->tty_drivers, &tty_drivers);
3457
3458	if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {
3459		for (i = 0; i < driver->num; i++) {
3460			d = tty_register_device(driver, i, NULL);
3461			if (IS_ERR(d)) {
3462				error = PTR_ERR(d);
3463				goto err_unreg_devs;
3464			}
3465		}
3466	}
3467	proc_tty_register_driver(driver);
3468	driver->flags |= TTY_DRIVER_INSTALLED;
3469	return 0;
3470
3471err_unreg_devs:
3472	for (i--; i >= 0; i--)
3473		tty_unregister_device(driver, i);
3474
3475	scoped_guard(mutex, &tty_mutex)
3476		list_del(&driver->tty_drivers);
3477
3478err_unreg_char:
3479	unregister_chrdev_region(dev, driver->num);
3480err:
3481	return error;
3482}
3483EXPORT_SYMBOL(tty_register_driver);
3484
3485/**
3486 * tty_unregister_driver - unregister a tty driver
3487 * @driver: driver to unregister
3488 *
3489 * Called by a tty driver to unregister itself.
3490 */
3491void tty_unregister_driver(struct tty_driver *driver)
3492{
3493	unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
3494				driver->num);
3495	scoped_guard(mutex, &tty_mutex)
3496		list_del(&driver->tty_drivers);
3497}
3498EXPORT_SYMBOL(tty_unregister_driver);
3499
3500dev_t tty_devnum(struct tty_struct *tty)
3501{
3502	return MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
3503}
3504EXPORT_SYMBOL(tty_devnum);
3505
3506void tty_default_fops(struct file_operations *fops)
3507{
3508	*fops = tty_fops;
3509}
3510
3511static char *tty_devnode(const struct device *dev, umode_t *mode)
3512{
3513	if (!mode)
3514		return NULL;
3515	if (dev->devt == MKDEV(TTYAUX_MAJOR, 0) ||
3516	    dev->devt == MKDEV(TTYAUX_MAJOR, 2))
3517		*mode = 0666;
3518	return NULL;
3519}
3520
3521const struct class tty_class = {
3522	.name		= "tty",
3523	.devnode	= tty_devnode,
3524};
3525
3526static int __init tty_class_init(void)
3527{
3528	return class_register(&tty_class);
3529}
3530
3531postcore_initcall(tty_class_init);
3532
3533/* 3/2004 jmc: why do these devices exist? */
3534static struct cdev tty_cdev, console_cdev;
3535
3536static ssize_t show_cons_active(struct device *dev,
3537				struct device_attribute *attr, char *buf)
3538{
3539	struct console *cs[16];
3540	int i = 0;
3541	struct console *c;
3542	ssize_t count = 0;
3543
3544	/*
3545	 * Hold the console_list_lock to guarantee that no consoles are
3546	 * unregistered until all console processing is complete.
3547	 * This also allows safe traversal of the console list and
3548	 * race-free reading of @flags.
3549	 */
3550	console_list_lock();
3551
3552	for_each_console(c) {
3553		if (!c->device)
3554			continue;
3555		if (!(c->flags & CON_NBCON) && !c->write)
3556			continue;
3557		if ((c->flags & CON_ENABLED) == 0)
3558			continue;
3559		cs[i++] = c;
3560		if (i >= ARRAY_SIZE(cs))
3561			break;
3562	}
3563
3564	/*
3565	 * Take console_lock to serialize device() callback with
3566	 * other console operations. For example, fg_console is
3567	 * modified under console_lock when switching vt.
3568	 */
3569	console_lock();
3570	while (i--) {
3571		int index = cs[i]->index;
3572		struct tty_driver *drv = cs[i]->device(cs[i], &index);
3573
3574		/* don't resolve tty0 as some programs depend on it */
3575		if (drv && (cs[i]->index > 0 || drv->major != TTY_MAJOR))
3576			count += tty_line_name(drv, index, buf + count);
3577		else
3578			count += sprintf(buf + count, "%s%d",
3579					 cs[i]->name, cs[i]->index);
3580
3581		count += sprintf(buf + count, "%c", i ? ' ':'\n');
3582	}
3583	console_unlock();
3584
3585	console_list_unlock();
3586
3587	return count;
3588}
3589static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);
3590
3591static struct attribute *cons_dev_attrs[] = {
3592	&dev_attr_active.attr,
3593	NULL
3594};
3595
3596ATTRIBUTE_GROUPS(cons_dev);
3597
3598static struct device *consdev;
3599
3600void console_sysfs_notify(void)
3601{
3602	if (consdev)
3603		sysfs_notify(&consdev->kobj, NULL, "active");
3604}
3605
3606static const struct ctl_table tty_table[] = {
3607	{
3608		.procname	= "legacy_tiocsti",
3609		.data		= &tty_legacy_tiocsti,
3610		.maxlen		= sizeof(tty_legacy_tiocsti),
3611		.mode		= 0644,
3612		.proc_handler	= proc_dobool,
3613	},
3614	{
3615		.procname	= "ldisc_autoload",
3616		.data		= &tty_ldisc_autoload,
3617		.maxlen		= sizeof(tty_ldisc_autoload),
3618		.mode		= 0644,
3619		.proc_handler	= proc_dointvec_minmax,
3620		.extra1		= SYSCTL_ZERO,
3621		.extra2		= SYSCTL_ONE,
3622	},
3623};
3624
3625/*
3626 * Ok, now we can initialize the rest of the tty devices and can count
3627 * on memory allocations, interrupts etc..
3628 */
3629int __init tty_init(void)
3630{
3631	register_sysctl_init("dev/tty", tty_table);
3632	cdev_init(&tty_cdev, &tty_fops);
3633	if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
3634	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
3635		panic("Couldn't register /dev/tty driver\n");
3636	device_create(&tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, "tty");
3637
3638	cdev_init(&console_cdev, &console_fops);
3639	if (cdev_add(&console_cdev, MKDEV(TTYAUX_MAJOR, 1), 1) ||
3640	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 1), 1, "/dev/console") < 0)
3641		panic("Couldn't register /dev/console driver\n");
3642	consdev = device_create_with_groups(&tty_class, NULL,
3643					    MKDEV(TTYAUX_MAJOR, 1), NULL,
3644					    cons_dev_groups, "console");
3645	if (IS_ERR(consdev))
3646		consdev = NULL;
3647
3648#ifdef CONFIG_VT
3649	vty_init(&console_fops);
3650#endif
3651	return 0;
3652}