1// SPDX-License-Identifier: GPL-1.0+
   2/*
   3 * n_tty.c --- implements the N_TTY line discipline.
   4 *
   5 * This code used to be in tty_io.c, but things are getting hairy
   6 * enough that it made sense to split things off.  (The N_TTY
   7 * processing has changed so much that it's hardly recognizable,
   8 * anyway...)
   9 *
  10 * Note that the open routine for N_TTY is guaranteed never to return
  11 * an error.  This is because Linux will fall back to setting a line
  12 * to N_TTY if it can not switch to any other line discipline.
  13 *
  14 * Written by Theodore Ts'o, Copyright 1994.
  15 *
  16 * This file also contains code originally written by Linus Torvalds,
  17 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
  18 *
 
 
 
  19 * Reduced memory usage for older ARM systems  - Russell King.
  20 *
  21 * 2000/01/20   Fixed SMP locking on put_tty_queue using bits of
  22 *		the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
  23 *		who actually finally proved there really was a race.
  24 *
  25 * 2002/03/18   Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
  26 *		waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
  27 *		Also fixed a bug in BLOCKING mode where n_tty_write returns
  28 *		EAGAIN
  29 */
  30
  31#include <linux/types.h>
  32#include <linux/major.h>
  33#include <linux/errno.h>
  34#include <linux/signal.h>
  35#include <linux/fcntl.h>
  36#include <linux/sched.h>
  37#include <linux/interrupt.h>
  38#include <linux/tty.h>
  39#include <linux/timer.h>
  40#include <linux/ctype.h>
  41#include <linux/mm.h>
  42#include <linux/string.h>
  43#include <linux/slab.h>
  44#include <linux/poll.h>
  45#include <linux/bitops.h>
  46#include <linux/audit.h>
  47#include <linux/file.h>
  48#include <linux/uaccess.h>
  49#include <linux/module.h>
  50#include <linux/ratelimit.h>
  51#include <linux/vmalloc.h>
  52
  53/*
  54 * Until this number of characters is queued in the xmit buffer, select will
  55 * return "we have room for writes".
  56 */
  57#define WAKEUP_CHARS 256
  58
  59/*
  60 * This defines the low- and high-watermarks for throttling and
  61 * unthrottling the TTY driver.  These watermarks are used for
  62 * controlling the space in the read buffer.
  63 */
  64#define TTY_THRESHOLD_THROTTLE		128 /* now based on remaining room */
  65#define TTY_THRESHOLD_UNTHROTTLE	128
  66
  67/*
  68 * Special byte codes used in the echo buffer to represent operations
  69 * or special handling of characters.  Bytes in the echo buffer that
  70 * are not part of such special blocks are treated as normal character
  71 * codes.
  72 */
  73#define ECHO_OP_START 0xff
  74#define ECHO_OP_MOVE_BACK_COL 0x80
  75#define ECHO_OP_SET_CANON_COL 0x81
  76#define ECHO_OP_ERASE_TAB 0x82
  77
  78#define ECHO_COMMIT_WATERMARK	256
  79#define ECHO_BLOCK		256
  80#define ECHO_DISCARD_WATERMARK	N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
  81
  82
  83#undef N_TTY_TRACE
  84#ifdef N_TTY_TRACE
  85# define n_tty_trace(f, args...)	trace_printk(f, ##args)
  86#else
  87# define n_tty_trace(f, args...)	no_printk(f, ##args)
  88#endif
  89
  90struct n_tty_data {
  91	/* producer-published */
  92	size_t read_head;
  93	size_t commit_head;
  94	size_t canon_head;
  95	size_t echo_head;
  96	size_t echo_commit;
  97	size_t echo_mark;
  98	DECLARE_BITMAP(char_map, 256);
  99
 100	/* private to n_tty_receive_overrun (single-threaded) */
 101	unsigned long overrun_time;
 102	int num_overrun;
 103
 104	/* non-atomic */
 105	bool no_room;
 106
 107	/* must hold exclusive termios_rwsem to reset these */
 108	unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
 109	unsigned char push:1;
 110
 111	/* shared by producer and consumer */
 112	char read_buf[N_TTY_BUF_SIZE];
 113	DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
 114	unsigned char echo_buf[N_TTY_BUF_SIZE];
 115
 116	/* consumer-published */
 117	size_t read_tail;
 118	size_t line_start;
 119
 120	/* protected by output lock */
 121	unsigned int column;
 122	unsigned int canon_column;
 123	size_t echo_tail;
 124
 125	struct mutex atomic_read_lock;
 126	struct mutex output_lock;
 127};
 128
 129#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
 130
 131static inline size_t read_cnt(struct n_tty_data *ldata)
 132{
 133	return ldata->read_head - ldata->read_tail;
 134}
 135
 136static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
 137{
 138	return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
 139}
 140
 141static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
 142{
 143	return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
 144}
 145
 146static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
 147{
 148	smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
 149	return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
 150}
 151
 152static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
 153{
 154	return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
 155}
 156
 157/* If we are not echoing the data, perhaps this is a secret so erase it */
 158static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
 159{
 160	bool icanon = !!L_ICANON(tty);
 161	bool no_echo = !L_ECHO(tty);
 162
 163	if (icanon && no_echo)
 164		memset(buffer, 0x00, size);
 165}
 166
 167static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
 168			    size_t tail, size_t n)
 169{
 170	struct n_tty_data *ldata = tty->disc_data;
 171	size_t size = N_TTY_BUF_SIZE - tail;
 172	void *from = read_buf_addr(ldata, tail);
 173	int uncopied;
 174
 175	if (n > size) {
 176		tty_audit_add_data(tty, from, size);
 177		uncopied = copy_to_user(to, from, size);
 178		zero_buffer(tty, from, size - uncopied);
 179		if (uncopied)
 180			return uncopied;
 181		to += size;
 182		n -= size;
 183		from = ldata->read_buf;
 184	}
 185
 186	tty_audit_add_data(tty, from, n);
 187	uncopied = copy_to_user(to, from, n);
 188	zero_buffer(tty, from, n - uncopied);
 189	return uncopied;
 190}
 191
 192/**
 193 *	n_tty_kick_worker - start input worker (if required)
 194 *	@tty: terminal
 195 *
 196 *	Re-schedules the flip buffer work if it may have stopped
 197 *
 198 *	Caller holds exclusive termios_rwsem
 199 *	   or
 200 *	n_tty_read()/consumer path:
 201 *		holds non-exclusive termios_rwsem
 202 */
 203
 204static void n_tty_kick_worker(struct tty_struct *tty)
 205{
 206	struct n_tty_data *ldata = tty->disc_data;
 207
 208	/* Did the input worker stop? Restart it */
 209	if (unlikely(ldata->no_room)) {
 210		ldata->no_room = 0;
 211
 212		WARN_RATELIMIT(tty->port->itty == NULL,
 213				"scheduling with invalid itty\n");
 214		/* see if ldisc has been killed - if so, this means that
 215		 * even though the ldisc has been halted and ->buf.work
 216		 * cancelled, ->buf.work is about to be rescheduled
 217		 */
 218		WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
 219			       "scheduling buffer work for halted ldisc\n");
 220		tty_buffer_restart_work(tty->port);
 221	}
 222}
 223
 224static ssize_t chars_in_buffer(struct tty_struct *tty)
 225{
 226	struct n_tty_data *ldata = tty->disc_data;
 227	ssize_t n = 0;
 228
 229	if (!ldata->icanon)
 230		n = ldata->commit_head - ldata->read_tail;
 231	else
 232		n = ldata->canon_head - ldata->read_tail;
 233	return n;
 234}
 235
 236/**
 237 *	n_tty_write_wakeup	-	asynchronous I/O notifier
 238 *	@tty: tty device
 239 *
 240 *	Required for the ptys, serial driver etc. since processes
 241 *	that attach themselves to the master and rely on ASYNC
 242 *	IO must be woken up
 243 */
 244
 245static void n_tty_write_wakeup(struct tty_struct *tty)
 246{
 247	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 248	kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
 249}
 250
 251static void n_tty_check_throttle(struct tty_struct *tty)
 252{
 253	struct n_tty_data *ldata = tty->disc_data;
 254
 255	/*
 256	 * Check the remaining room for the input canonicalization
 257	 * mode.  We don't want to throttle the driver if we're in
 258	 * canonical mode and don't have a newline yet!
 259	 */
 260	if (ldata->icanon && ldata->canon_head == ldata->read_tail)
 261		return;
 262
 263	while (1) {
 264		int throttled;
 265		tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
 266		if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
 267			break;
 268		throttled = tty_throttle_safe(tty);
 269		if (!throttled)
 270			break;
 271	}
 272	__tty_set_flow_change(tty, 0);
 273}
 274
 275static void n_tty_check_unthrottle(struct tty_struct *tty)
 276{
 277	if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
 278		if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
 279			return;
 280		n_tty_kick_worker(tty);
 281		tty_wakeup(tty->link);
 282		return;
 283	}
 284
 285	/* If there is enough space in the read buffer now, let the
 286	 * low-level driver know. We use chars_in_buffer() to
 287	 * check the buffer, as it now knows about canonical mode.
 288	 * Otherwise, if the driver is throttled and the line is
 289	 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
 290	 * we won't get any more characters.
 291	 */
 292
 293	while (1) {
 294		int unthrottled;
 295		tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
 296		if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
 297			break;
 298		n_tty_kick_worker(tty);
 299		unthrottled = tty_unthrottle_safe(tty);
 300		if (!unthrottled)
 301			break;
 302	}
 303	__tty_set_flow_change(tty, 0);
 304}
 305
 306/**
 307 *	put_tty_queue		-	add character to tty
 308 *	@c: character
 309 *	@ldata: n_tty data
 310 *
 311 *	Add a character to the tty read_buf queue.
 312 *
 313 *	n_tty_receive_buf()/producer path:
 314 *		caller holds non-exclusive termios_rwsem
 315 */
 316
 317static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
 318{
 319	*read_buf_addr(ldata, ldata->read_head) = c;
 320	ldata->read_head++;
 321}
 322
 323/**
 324 *	reset_buffer_flags	-	reset buffer state
 325 *	@tty: terminal to reset
 326 *
 327 *	Reset the read buffer counters and clear the flags.
 328 *	Called from n_tty_open() and n_tty_flush_buffer().
 329 *
 330 *	Locking: caller holds exclusive termios_rwsem
 331 *		 (or locking is not required)
 332 */
 333
 334static void reset_buffer_flags(struct n_tty_data *ldata)
 335{
 336	ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
 
 337	ldata->commit_head = 0;
 
 338	ldata->line_start = 0;
 339
 340	ldata->erasing = 0;
 341	bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
 342	ldata->push = 0;
 343}
 344
 345static void n_tty_packet_mode_flush(struct tty_struct *tty)
 346{
 347	unsigned long flags;
 348
 349	if (tty->link->packet) {
 350		spin_lock_irqsave(&tty->ctrl_lock, flags);
 351		tty->ctrl_status |= TIOCPKT_FLUSHREAD;
 352		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 353		wake_up_interruptible(&tty->link->read_wait);
 354	}
 355}
 356
 357/**
 358 *	n_tty_flush_buffer	-	clean input queue
 359 *	@tty:	terminal device
 360 *
 361 *	Flush the input buffer. Called when the tty layer wants the
 362 *	buffer flushed (eg at hangup) or when the N_TTY line discipline
 363 *	internally has to clean the pending queue (for example some signals).
 364 *
 365 *	Holds termios_rwsem to exclude producer/consumer while
 366 *	buffer indices are reset.
 367 *
 368 *	Locking: ctrl_lock, exclusive termios_rwsem
 369 */
 370
 371static void n_tty_flush_buffer(struct tty_struct *tty)
 372{
 373	down_write(&tty->termios_rwsem);
 374	reset_buffer_flags(tty->disc_data);
 375	n_tty_kick_worker(tty);
 376
 377	if (tty->link)
 378		n_tty_packet_mode_flush(tty);
 379	up_write(&tty->termios_rwsem);
 380}
 381
 382/**
 383 *	is_utf8_continuation	-	utf8 multibyte check
 384 *	@c: byte to check
 385 *
 386 *	Returns true if the utf8 character 'c' is a multibyte continuation
 387 *	character. We use this to correctly compute the on screen size
 388 *	of the character when printing
 389 */
 390
 391static inline int is_utf8_continuation(unsigned char c)
 392{
 393	return (c & 0xc0) == 0x80;
 394}
 395
 396/**
 397 *	is_continuation		-	multibyte check
 398 *	@c: byte to check
 399 *
 400 *	Returns true if the utf8 character 'c' is a multibyte continuation
 401 *	character and the terminal is in unicode mode.
 402 */
 403
 404static inline int is_continuation(unsigned char c, struct tty_struct *tty)
 405{
 406	return I_IUTF8(tty) && is_utf8_continuation(c);
 407}
 408
 409/**
 410 *	do_output_char			-	output one character
 411 *	@c: character (or partial unicode symbol)
 412 *	@tty: terminal device
 413 *	@space: space available in tty driver write buffer
 414 *
 415 *	This is a helper function that handles one output character
 416 *	(including special characters like TAB, CR, LF, etc.),
 417 *	doing OPOST processing and putting the results in the
 418 *	tty driver's write buffer.
 419 *
 420 *	Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
 421 *	and NLDLY.  They simply aren't relevant in the world today.
 422 *	If you ever need them, add them here.
 423 *
 424 *	Returns the number of bytes of buffer space used or -1 if
 425 *	no space left.
 426 *
 427 *	Locking: should be called under the output_lock to protect
 428 *		 the column state and space left in the buffer
 429 */
 430
 431static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
 432{
 433	struct n_tty_data *ldata = tty->disc_data;
 434	int	spaces;
 435
 436	if (!space)
 437		return -1;
 438
 439	switch (c) {
 440	case '\n':
 441		if (O_ONLRET(tty))
 442			ldata->column = 0;
 443		if (O_ONLCR(tty)) {
 444			if (space < 2)
 445				return -1;
 446			ldata->canon_column = ldata->column = 0;
 447			tty->ops->write(tty, "\r\n", 2);
 448			return 2;
 449		}
 450		ldata->canon_column = ldata->column;
 451		break;
 452	case '\r':
 453		if (O_ONOCR(tty) && ldata->column == 0)
 454			return 0;
 455		if (O_OCRNL(tty)) {
 456			c = '\n';
 457			if (O_ONLRET(tty))
 458				ldata->canon_column = ldata->column = 0;
 459			break;
 460		}
 461		ldata->canon_column = ldata->column = 0;
 462		break;
 463	case '\t':
 464		spaces = 8 - (ldata->column & 7);
 465		if (O_TABDLY(tty) == XTABS) {
 466			if (space < spaces)
 467				return -1;
 468			ldata->column += spaces;
 469			tty->ops->write(tty, "        ", spaces);
 470			return spaces;
 471		}
 472		ldata->column += spaces;
 473		break;
 474	case '\b':
 475		if (ldata->column > 0)
 476			ldata->column--;
 477		break;
 478	default:
 479		if (!iscntrl(c)) {
 480			if (O_OLCUC(tty))
 481				c = toupper(c);
 482			if (!is_continuation(c, tty))
 483				ldata->column++;
 484		}
 485		break;
 486	}
 487
 488	tty_put_char(tty, c);
 489	return 1;
 490}
 491
 492/**
 493 *	process_output			-	output post processor
 494 *	@c: character (or partial unicode symbol)
 495 *	@tty: terminal device
 496 *
 497 *	Output one character with OPOST processing.
 498 *	Returns -1 when the output device is full and the character
 499 *	must be retried.
 500 *
 501 *	Locking: output_lock to protect column state and space left
 502 *		 (also, this is called from n_tty_write under the
 503 *		  tty layer write lock)
 504 */
 505
 506static int process_output(unsigned char c, struct tty_struct *tty)
 507{
 508	struct n_tty_data *ldata = tty->disc_data;
 509	int	space, retval;
 510
 511	mutex_lock(&ldata->output_lock);
 512
 513	space = tty_write_room(tty);
 514	retval = do_output_char(c, tty, space);
 515
 516	mutex_unlock(&ldata->output_lock);
 517	if (retval < 0)
 518		return -1;
 519	else
 520		return 0;
 521}
 522
 523/**
 524 *	process_output_block		-	block post processor
 525 *	@tty: terminal device
 526 *	@buf: character buffer
 527 *	@nr: number of bytes to output
 528 *
 529 *	Output a block of characters with OPOST processing.
 530 *	Returns the number of characters output.
 531 *
 532 *	This path is used to speed up block console writes, among other
 533 *	things when processing blocks of output data. It handles only
 534 *	the simple cases normally found and helps to generate blocks of
 535 *	symbols for the console driver and thus improve performance.
 536 *
 537 *	Locking: output_lock to protect column state and space left
 538 *		 (also, this is called from n_tty_write under the
 539 *		  tty layer write lock)
 540 */
 541
 542static ssize_t process_output_block(struct tty_struct *tty,
 543				    const unsigned char *buf, unsigned int nr)
 544{
 545	struct n_tty_data *ldata = tty->disc_data;
 546	int	space;
 547	int	i;
 548	const unsigned char *cp;
 549
 550	mutex_lock(&ldata->output_lock);
 551
 552	space = tty_write_room(tty);
 553	if (space <= 0) {
 554		mutex_unlock(&ldata->output_lock);
 555		return space;
 556	}
 557	if (nr > space)
 558		nr = space;
 559
 560	for (i = 0, cp = buf; i < nr; i++, cp++) {
 561		unsigned char c = *cp;
 562
 563		switch (c) {
 564		case '\n':
 565			if (O_ONLRET(tty))
 566				ldata->column = 0;
 567			if (O_ONLCR(tty))
 568				goto break_out;
 569			ldata->canon_column = ldata->column;
 570			break;
 571		case '\r':
 572			if (O_ONOCR(tty) && ldata->column == 0)
 573				goto break_out;
 574			if (O_OCRNL(tty))
 575				goto break_out;
 576			ldata->canon_column = ldata->column = 0;
 577			break;
 578		case '\t':
 579			goto break_out;
 580		case '\b':
 581			if (ldata->column > 0)
 582				ldata->column--;
 583			break;
 584		default:
 585			if (!iscntrl(c)) {
 586				if (O_OLCUC(tty))
 587					goto break_out;
 588				if (!is_continuation(c, tty))
 589					ldata->column++;
 590			}
 591			break;
 592		}
 593	}
 594break_out:
 595	i = tty->ops->write(tty, buf, i);
 596
 597	mutex_unlock(&ldata->output_lock);
 598	return i;
 599}
 600
 601/**
 602 *	process_echoes	-	write pending echo characters
 603 *	@tty: terminal device
 604 *
 605 *	Write previously buffered echo (and other ldisc-generated)
 606 *	characters to the tty.
 607 *
 608 *	Characters generated by the ldisc (including echoes) need to
 609 *	be buffered because the driver's write buffer can fill during
 610 *	heavy program output.  Echoing straight to the driver will
 611 *	often fail under these conditions, causing lost characters and
 612 *	resulting mismatches of ldisc state information.
 613 *
 614 *	Since the ldisc state must represent the characters actually sent
 615 *	to the driver at the time of the write, operations like certain
 616 *	changes in column state are also saved in the buffer and executed
 617 *	here.
 618 *
 619 *	A circular fifo buffer is used so that the most recent characters
 620 *	are prioritized.  Also, when control characters are echoed with a
 621 *	prefixed "^", the pair is treated atomically and thus not separated.
 622 *
 623 *	Locking: callers must hold output_lock
 624 */
 625
 626static size_t __process_echoes(struct tty_struct *tty)
 627{
 628	struct n_tty_data *ldata = tty->disc_data;
 629	int	space, old_space;
 630	size_t tail;
 631	unsigned char c;
 632
 633	old_space = space = tty_write_room(tty);
 634
 635	tail = ldata->echo_tail;
 636	while (MASK(ldata->echo_commit) != MASK(tail)) {
 637		c = echo_buf(ldata, tail);
 638		if (c == ECHO_OP_START) {
 639			unsigned char op;
 640			int no_space_left = 0;
 641
 642			/*
 643			 * Since add_echo_byte() is called without holding
 644			 * output_lock, we might see only portion of multi-byte
 645			 * operation.
 646			 */
 647			if (MASK(ldata->echo_commit) == MASK(tail + 1))
 648				goto not_yet_stored;
 649			/*
 650			 * If the buffer byte is the start of a multi-byte
 651			 * operation, get the next byte, which is either the
 652			 * op code or a control character value.
 653			 */
 654			op = echo_buf(ldata, tail + 1);
 655
 656			switch (op) {
 657			case ECHO_OP_ERASE_TAB: {
 658				unsigned int num_chars, num_bs;
 659
 660				if (MASK(ldata->echo_commit) == MASK(tail + 2))
 661					goto not_yet_stored;
 662				num_chars = echo_buf(ldata, tail + 2);
 663
 664				/*
 665				 * Determine how many columns to go back
 666				 * in order to erase the tab.
 667				 * This depends on the number of columns
 668				 * used by other characters within the tab
 669				 * area.  If this (modulo 8) count is from
 670				 * the start of input rather than from a
 671				 * previous tab, we offset by canon column.
 672				 * Otherwise, tab spacing is normal.
 673				 */
 674				if (!(num_chars & 0x80))
 675					num_chars += ldata->canon_column;
 676				num_bs = 8 - (num_chars & 7);
 677
 678				if (num_bs > space) {
 679					no_space_left = 1;
 680					break;
 681				}
 682				space -= num_bs;
 683				while (num_bs--) {
 684					tty_put_char(tty, '\b');
 685					if (ldata->column > 0)
 686						ldata->column--;
 687				}
 688				tail += 3;
 689				break;
 690			}
 691			case ECHO_OP_SET_CANON_COL:
 692				ldata->canon_column = ldata->column;
 693				tail += 2;
 694				break;
 695
 696			case ECHO_OP_MOVE_BACK_COL:
 697				if (ldata->column > 0)
 698					ldata->column--;
 699				tail += 2;
 700				break;
 701
 702			case ECHO_OP_START:
 703				/* This is an escaped echo op start code */
 704				if (!space) {
 705					no_space_left = 1;
 706					break;
 707				}
 708				tty_put_char(tty, ECHO_OP_START);
 709				ldata->column++;
 710				space--;
 711				tail += 2;
 712				break;
 713
 714			default:
 715				/*
 716				 * If the op is not a special byte code,
 717				 * it is a ctrl char tagged to be echoed
 718				 * as "^X" (where X is the letter
 719				 * representing the control char).
 720				 * Note that we must ensure there is
 721				 * enough space for the whole ctrl pair.
 722				 *
 723				 */
 724				if (space < 2) {
 725					no_space_left = 1;
 726					break;
 727				}
 728				tty_put_char(tty, '^');
 729				tty_put_char(tty, op ^ 0100);
 730				ldata->column += 2;
 731				space -= 2;
 732				tail += 2;
 733			}
 734
 735			if (no_space_left)
 736				break;
 737		} else {
 738			if (O_OPOST(tty)) {
 739				int retval = do_output_char(c, tty, space);
 740				if (retval < 0)
 741					break;
 742				space -= retval;
 743			} else {
 744				if (!space)
 745					break;
 746				tty_put_char(tty, c);
 747				space -= 1;
 748			}
 749			tail += 1;
 750		}
 751	}
 752
 753	/* If the echo buffer is nearly full (so that the possibility exists
 754	 * of echo overrun before the next commit), then discard enough
 755	 * data at the tail to prevent a subsequent overrun */
 756	while (ldata->echo_commit > tail &&
 757	       ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
 758		if (echo_buf(ldata, tail) == ECHO_OP_START) {
 759			if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
 760				tail += 3;
 761			else
 762				tail += 2;
 763		} else
 764			tail++;
 765	}
 766
 767 not_yet_stored:
 768	ldata->echo_tail = tail;
 769	return old_space - space;
 770}
 771
 772static void commit_echoes(struct tty_struct *tty)
 773{
 774	struct n_tty_data *ldata = tty->disc_data;
 775	size_t nr, old, echoed;
 776	size_t head;
 777
 778	mutex_lock(&ldata->output_lock);
 779	head = ldata->echo_head;
 780	ldata->echo_mark = head;
 781	old = ldata->echo_commit - ldata->echo_tail;
 782
 783	/* Process committed echoes if the accumulated # of bytes
 784	 * is over the threshold (and try again each time another
 785	 * block is accumulated) */
 786	nr = head - ldata->echo_tail;
 787	if (nr < ECHO_COMMIT_WATERMARK ||
 788	    (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
 789		mutex_unlock(&ldata->output_lock);
 790		return;
 791	}
 792
 
 793	ldata->echo_commit = head;
 794	echoed = __process_echoes(tty);
 795	mutex_unlock(&ldata->output_lock);
 796
 797	if (echoed && tty->ops->flush_chars)
 798		tty->ops->flush_chars(tty);
 799}
 800
 801static void process_echoes(struct tty_struct *tty)
 802{
 803	struct n_tty_data *ldata = tty->disc_data;
 804	size_t echoed;
 805
 806	if (ldata->echo_mark == ldata->echo_tail)
 807		return;
 808
 809	mutex_lock(&ldata->output_lock);
 810	ldata->echo_commit = ldata->echo_mark;
 811	echoed = __process_echoes(tty);
 812	mutex_unlock(&ldata->output_lock);
 813
 814	if (echoed && tty->ops->flush_chars)
 815		tty->ops->flush_chars(tty);
 816}
 817
 818/* NB: echo_mark and echo_head should be equivalent here */
 819static void flush_echoes(struct tty_struct *tty)
 820{
 821	struct n_tty_data *ldata = tty->disc_data;
 822
 823	if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
 824	    ldata->echo_commit == ldata->echo_head)
 825		return;
 826
 827	mutex_lock(&ldata->output_lock);
 828	ldata->echo_commit = ldata->echo_head;
 829	__process_echoes(tty);
 830	mutex_unlock(&ldata->output_lock);
 831}
 832
 833/**
 834 *	add_echo_byte	-	add a byte to the echo buffer
 835 *	@c: unicode byte to echo
 836 *	@ldata: n_tty data
 837 *
 838 *	Add a character or operation byte to the echo buffer.
 839 */
 840
 841static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
 842{
 843	*echo_buf_addr(ldata, ldata->echo_head) = c;
 844	smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
 845	ldata->echo_head++;
 846}
 847
 848/**
 849 *	echo_move_back_col	-	add operation to move back a column
 850 *	@ldata: n_tty data
 851 *
 852 *	Add an operation to the echo buffer to move back one column.
 853 */
 854
 855static void echo_move_back_col(struct n_tty_data *ldata)
 856{
 857	add_echo_byte(ECHO_OP_START, ldata);
 858	add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
 859}
 860
 861/**
 862 *	echo_set_canon_col	-	add operation to set the canon column
 863 *	@ldata: n_tty data
 864 *
 865 *	Add an operation to the echo buffer to set the canon column
 866 *	to the current column.
 867 */
 868
 869static void echo_set_canon_col(struct n_tty_data *ldata)
 870{
 871	add_echo_byte(ECHO_OP_START, ldata);
 872	add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
 873}
 874
 875/**
 876 *	echo_erase_tab	-	add operation to erase a tab
 877 *	@num_chars: number of character columns already used
 878 *	@after_tab: true if num_chars starts after a previous tab
 879 *	@ldata: n_tty data
 880 *
 881 *	Add an operation to the echo buffer to erase a tab.
 882 *
 883 *	Called by the eraser function, which knows how many character
 884 *	columns have been used since either a previous tab or the start
 885 *	of input.  This information will be used later, along with
 886 *	canon column (if applicable), to go back the correct number
 887 *	of columns.
 888 */
 889
 890static void echo_erase_tab(unsigned int num_chars, int after_tab,
 891			   struct n_tty_data *ldata)
 892{
 893	add_echo_byte(ECHO_OP_START, ldata);
 894	add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
 895
 896	/* We only need to know this modulo 8 (tab spacing) */
 897	num_chars &= 7;
 898
 899	/* Set the high bit as a flag if num_chars is after a previous tab */
 900	if (after_tab)
 901		num_chars |= 0x80;
 902
 903	add_echo_byte(num_chars, ldata);
 904}
 905
 906/**
 907 *	echo_char_raw	-	echo a character raw
 908 *	@c: unicode byte to echo
 909 *	@tty: terminal device
 910 *
 911 *	Echo user input back onto the screen. This must be called only when
 912 *	L_ECHO(tty) is true. Called from the driver receive_buf path.
 913 *
 914 *	This variant does not treat control characters specially.
 915 */
 916
 917static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
 918{
 919	if (c == ECHO_OP_START) {
 920		add_echo_byte(ECHO_OP_START, ldata);
 921		add_echo_byte(ECHO_OP_START, ldata);
 922	} else {
 923		add_echo_byte(c, ldata);
 924	}
 925}
 926
 927/**
 928 *	echo_char	-	echo a character
 929 *	@c: unicode byte to echo
 930 *	@tty: terminal device
 931 *
 932 *	Echo user input back onto the screen. This must be called only when
 933 *	L_ECHO(tty) is true. Called from the driver receive_buf path.
 934 *
 935 *	This variant tags control characters to be echoed as "^X"
 936 *	(where X is the letter representing the control char).
 937 */
 938
 939static void echo_char(unsigned char c, struct tty_struct *tty)
 940{
 941	struct n_tty_data *ldata = tty->disc_data;
 942
 943	if (c == ECHO_OP_START) {
 944		add_echo_byte(ECHO_OP_START, ldata);
 945		add_echo_byte(ECHO_OP_START, ldata);
 946	} else {
 947		if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
 948			add_echo_byte(ECHO_OP_START, ldata);
 949		add_echo_byte(c, ldata);
 950	}
 951}
 952
 953/**
 954 *	finish_erasing		-	complete erase
 955 *	@ldata: n_tty data
 956 */
 957
 958static inline void finish_erasing(struct n_tty_data *ldata)
 959{
 960	if (ldata->erasing) {
 961		echo_char_raw('/', ldata);
 962		ldata->erasing = 0;
 963	}
 964}
 965
 966/**
 967 *	eraser		-	handle erase function
 968 *	@c: character input
 969 *	@tty: terminal device
 970 *
 971 *	Perform erase and necessary output when an erase character is
 972 *	present in the stream from the driver layer. Handles the complexities
 973 *	of UTF-8 multibyte symbols.
 974 *
 975 *	n_tty_receive_buf()/producer path:
 976 *		caller holds non-exclusive termios_rwsem
 977 */
 978
 979static void eraser(unsigned char c, struct tty_struct *tty)
 980{
 981	struct n_tty_data *ldata = tty->disc_data;
 982	enum { ERASE, WERASE, KILL } kill_type;
 983	size_t head;
 984	size_t cnt;
 985	int seen_alnums;
 986
 987	if (ldata->read_head == ldata->canon_head) {
 988		/* process_output('\a', tty); */ /* what do you think? */
 989		return;
 990	}
 991	if (c == ERASE_CHAR(tty))
 992		kill_type = ERASE;
 993	else if (c == WERASE_CHAR(tty))
 994		kill_type = WERASE;
 995	else {
 996		if (!L_ECHO(tty)) {
 997			ldata->read_head = ldata->canon_head;
 998			return;
 999		}
1000		if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1001			ldata->read_head = ldata->canon_head;
1002			finish_erasing(ldata);
1003			echo_char(KILL_CHAR(tty), tty);
1004			/* Add a newline if ECHOK is on and ECHOKE is off. */
1005			if (L_ECHOK(tty))
1006				echo_char_raw('\n', ldata);
1007			return;
1008		}
1009		kill_type = KILL;
1010	}
1011
1012	seen_alnums = 0;
1013	while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
1014		head = ldata->read_head;
1015
1016		/* erase a single possibly multibyte character */
1017		do {
1018			head--;
1019			c = read_buf(ldata, head);
1020		} while (is_continuation(c, tty) &&
1021			 MASK(head) != MASK(ldata->canon_head));
1022
1023		/* do not partially erase */
1024		if (is_continuation(c, tty))
1025			break;
1026
1027		if (kill_type == WERASE) {
1028			/* Equivalent to BSD's ALTWERASE. */
1029			if (isalnum(c) || c == '_')
1030				seen_alnums++;
1031			else if (seen_alnums)
1032				break;
1033		}
1034		cnt = ldata->read_head - head;
1035		ldata->read_head = head;
1036		if (L_ECHO(tty)) {
1037			if (L_ECHOPRT(tty)) {
1038				if (!ldata->erasing) {
1039					echo_char_raw('\\', ldata);
1040					ldata->erasing = 1;
1041				}
1042				/* if cnt > 1, output a multi-byte character */
1043				echo_char(c, tty);
1044				while (--cnt > 0) {
1045					head++;
1046					echo_char_raw(read_buf(ldata, head), ldata);
1047					echo_move_back_col(ldata);
1048				}
1049			} else if (kill_type == ERASE && !L_ECHOE(tty)) {
1050				echo_char(ERASE_CHAR(tty), tty);
1051			} else if (c == '\t') {
1052				unsigned int num_chars = 0;
1053				int after_tab = 0;
1054				size_t tail = ldata->read_head;
1055
1056				/*
1057				 * Count the columns used for characters
1058				 * since the start of input or after a
1059				 * previous tab.
1060				 * This info is used to go back the correct
1061				 * number of columns.
1062				 */
1063				while (MASK(tail) != MASK(ldata->canon_head)) {
1064					tail--;
1065					c = read_buf(ldata, tail);
1066					if (c == '\t') {
1067						after_tab = 1;
1068						break;
1069					} else if (iscntrl(c)) {
1070						if (L_ECHOCTL(tty))
1071							num_chars += 2;
1072					} else if (!is_continuation(c, tty)) {
1073						num_chars++;
1074					}
1075				}
1076				echo_erase_tab(num_chars, after_tab, ldata);
1077			} else {
1078				if (iscntrl(c) && L_ECHOCTL(tty)) {
1079					echo_char_raw('\b', ldata);
1080					echo_char_raw(' ', ldata);
1081					echo_char_raw('\b', ldata);
1082				}
1083				if (!iscntrl(c) || L_ECHOCTL(tty)) {
1084					echo_char_raw('\b', ldata);
1085					echo_char_raw(' ', ldata);
1086					echo_char_raw('\b', ldata);
1087				}
1088			}
1089		}
1090		if (kill_type == ERASE)
1091			break;
1092	}
1093	if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1094		finish_erasing(ldata);
1095}
1096
1097/**
1098 *	isig		-	handle the ISIG optio
1099 *	@sig: signal
1100 *	@tty: terminal
1101 *
1102 *	Called when a signal is being sent due to terminal input.
1103 *	Called from the driver receive_buf path so serialized.
1104 *
1105 *	Performs input and output flush if !NOFLSH. In this context, the echo
1106 *	buffer is 'output'. The signal is processed first to alert any current
1107 *	readers or writers to discontinue and exit their i/o loops.
1108 *
1109 *	Locking: ctrl_lock
1110 */
1111
1112static void __isig(int sig, struct tty_struct *tty)
1113{
1114	struct pid *tty_pgrp = tty_get_pgrp(tty);
1115	if (tty_pgrp) {
1116		kill_pgrp(tty_pgrp, sig, 1);
1117		put_pid(tty_pgrp);
1118	}
1119}
1120
1121static void isig(int sig, struct tty_struct *tty)
1122{
1123	struct n_tty_data *ldata = tty->disc_data;
1124
1125	if (L_NOFLSH(tty)) {
1126		/* signal only */
1127		__isig(sig, tty);
1128
1129	} else { /* signal and flush */
1130		up_read(&tty->termios_rwsem);
1131		down_write(&tty->termios_rwsem);
1132
1133		__isig(sig, tty);
1134
1135		/* clear echo buffer */
1136		mutex_lock(&ldata->output_lock);
1137		ldata->echo_head = ldata->echo_tail = 0;
1138		ldata->echo_mark = ldata->echo_commit = 0;
1139		mutex_unlock(&ldata->output_lock);
1140
1141		/* clear output buffer */
1142		tty_driver_flush_buffer(tty);
1143
1144		/* clear input buffer */
1145		reset_buffer_flags(tty->disc_data);
1146
1147		/* notify pty master of flush */
1148		if (tty->link)
1149			n_tty_packet_mode_flush(tty);
1150
1151		up_write(&tty->termios_rwsem);
1152		down_read(&tty->termios_rwsem);
1153	}
1154}
1155
1156/**
1157 *	n_tty_receive_break	-	handle break
1158 *	@tty: terminal
1159 *
1160 *	An RS232 break event has been hit in the incoming bitstream. This
1161 *	can cause a variety of events depending upon the termios settings.
1162 *
1163 *	n_tty_receive_buf()/producer path:
1164 *		caller holds non-exclusive termios_rwsem
1165 *
1166 *	Note: may get exclusive termios_rwsem if flushing input buffer
1167 */
1168
1169static void n_tty_receive_break(struct tty_struct *tty)
1170{
1171	struct n_tty_data *ldata = tty->disc_data;
1172
1173	if (I_IGNBRK(tty))
1174		return;
1175	if (I_BRKINT(tty)) {
1176		isig(SIGINT, tty);
1177		return;
1178	}
1179	if (I_PARMRK(tty)) {
1180		put_tty_queue('\377', ldata);
1181		put_tty_queue('\0', ldata);
1182	}
1183	put_tty_queue('\0', ldata);
1184}
1185
1186/**
1187 *	n_tty_receive_overrun	-	handle overrun reporting
1188 *	@tty: terminal
1189 *
1190 *	Data arrived faster than we could process it. While the tty
1191 *	driver has flagged this the bits that were missed are gone
1192 *	forever.
1193 *
1194 *	Called from the receive_buf path so single threaded. Does not
1195 *	need locking as num_overrun and overrun_time are function
1196 *	private.
1197 */
1198
1199static void n_tty_receive_overrun(struct tty_struct *tty)
1200{
1201	struct n_tty_data *ldata = tty->disc_data;
1202
1203	ldata->num_overrun++;
1204	if (time_after(jiffies, ldata->overrun_time + HZ) ||
1205			time_after(ldata->overrun_time, jiffies)) {
1206		tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1207		ldata->overrun_time = jiffies;
1208		ldata->num_overrun = 0;
1209	}
1210}
1211
1212/**
1213 *	n_tty_receive_parity_error	-	error notifier
1214 *	@tty: terminal device
1215 *	@c: character
1216 *
1217 *	Process a parity error and queue the right data to indicate
1218 *	the error case if necessary.
1219 *
1220 *	n_tty_receive_buf()/producer path:
1221 *		caller holds non-exclusive termios_rwsem
1222 */
1223static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1224{
1225	struct n_tty_data *ldata = tty->disc_data;
1226
1227	if (I_INPCK(tty)) {
1228		if (I_IGNPAR(tty))
1229			return;
1230		if (I_PARMRK(tty)) {
1231			put_tty_queue('\377', ldata);
1232			put_tty_queue('\0', ldata);
1233			put_tty_queue(c, ldata);
1234		} else
1235			put_tty_queue('\0', ldata);
1236	} else
1237		put_tty_queue(c, ldata);
1238}
1239
1240static void
1241n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1242{
1243	isig(signal, tty);
1244	if (I_IXON(tty))
1245		start_tty(tty);
1246	if (L_ECHO(tty)) {
1247		echo_char(c, tty);
1248		commit_echoes(tty);
1249	} else
1250		process_echoes(tty);
1251	return;
1252}
1253
1254/**
1255 *	n_tty_receive_char	-	perform processing
1256 *	@tty: terminal device
1257 *	@c: character
1258 *
1259 *	Process an individual character of input received from the driver.
1260 *	This is serialized with respect to itself by the rules for the
1261 *	driver above.
1262 *
1263 *	n_tty_receive_buf()/producer path:
1264 *		caller holds non-exclusive termios_rwsem
1265 *		publishes canon_head if canonical mode is active
1266 *
1267 *	Returns 1 if LNEXT was received, else returns 0
1268 */
1269
1270static int
1271n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1272{
1273	struct n_tty_data *ldata = tty->disc_data;
1274
1275	if (I_IXON(tty)) {
1276		if (c == START_CHAR(tty)) {
1277			start_tty(tty);
1278			process_echoes(tty);
1279			return 0;
1280		}
1281		if (c == STOP_CHAR(tty)) {
1282			stop_tty(tty);
1283			return 0;
1284		}
1285	}
1286
1287	if (L_ISIG(tty)) {
1288		if (c == INTR_CHAR(tty)) {
1289			n_tty_receive_signal_char(tty, SIGINT, c);
1290			return 0;
1291		} else if (c == QUIT_CHAR(tty)) {
1292			n_tty_receive_signal_char(tty, SIGQUIT, c);
1293			return 0;
1294		} else if (c == SUSP_CHAR(tty)) {
1295			n_tty_receive_signal_char(tty, SIGTSTP, c);
1296			return 0;
1297		}
1298	}
1299
1300	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1301		start_tty(tty);
1302		process_echoes(tty);
1303	}
1304
1305	if (c == '\r') {
1306		if (I_IGNCR(tty))
1307			return 0;
1308		if (I_ICRNL(tty))
1309			c = '\n';
1310	} else if (c == '\n' && I_INLCR(tty))
1311		c = '\r';
1312
1313	if (ldata->icanon) {
1314		if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1315		    (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1316			eraser(c, tty);
1317			commit_echoes(tty);
1318			return 0;
1319		}
1320		if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1321			ldata->lnext = 1;
1322			if (L_ECHO(tty)) {
1323				finish_erasing(ldata);
1324				if (L_ECHOCTL(tty)) {
1325					echo_char_raw('^', ldata);
1326					echo_char_raw('\b', ldata);
1327					commit_echoes(tty);
1328				}
1329			}
1330			return 1;
1331		}
1332		if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1333			size_t tail = ldata->canon_head;
1334
1335			finish_erasing(ldata);
1336			echo_char(c, tty);
1337			echo_char_raw('\n', ldata);
1338			while (MASK(tail) != MASK(ldata->read_head)) {
1339				echo_char(read_buf(ldata, tail), tty);
1340				tail++;
1341			}
1342			commit_echoes(tty);
1343			return 0;
1344		}
1345		if (c == '\n') {
1346			if (L_ECHO(tty) || L_ECHONL(tty)) {
1347				echo_char_raw('\n', ldata);
1348				commit_echoes(tty);
1349			}
1350			goto handle_newline;
1351		}
1352		if (c == EOF_CHAR(tty)) {
1353			c = __DISABLED_CHAR;
1354			goto handle_newline;
1355		}
1356		if ((c == EOL_CHAR(tty)) ||
1357		    (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1358			/*
1359			 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1360			 */
1361			if (L_ECHO(tty)) {
1362				/* Record the column of first canon char. */
1363				if (ldata->canon_head == ldata->read_head)
1364					echo_set_canon_col(ldata);
1365				echo_char(c, tty);
1366				commit_echoes(tty);
1367			}
1368			/*
1369			 * XXX does PARMRK doubling happen for
1370			 * EOL_CHAR and EOL2_CHAR?
1371			 */
1372			if (c == (unsigned char) '\377' && I_PARMRK(tty))
1373				put_tty_queue(c, ldata);
1374
1375handle_newline:
1376			set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1377			put_tty_queue(c, ldata);
1378			smp_store_release(&ldata->canon_head, ldata->read_head);
1379			kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1380			wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1381			return 0;
1382		}
1383	}
1384
1385	if (L_ECHO(tty)) {
1386		finish_erasing(ldata);
1387		if (c == '\n')
1388			echo_char_raw('\n', ldata);
1389		else {
1390			/* Record the column of first canon char. */
1391			if (ldata->canon_head == ldata->read_head)
1392				echo_set_canon_col(ldata);
1393			echo_char(c, tty);
1394		}
1395		commit_echoes(tty);
1396	}
1397
1398	/* PARMRK doubling check */
1399	if (c == (unsigned char) '\377' && I_PARMRK(tty))
1400		put_tty_queue(c, ldata);
1401
1402	put_tty_queue(c, ldata);
1403	return 0;
1404}
1405
1406static inline void
1407n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1408{
1409	struct n_tty_data *ldata = tty->disc_data;
1410
1411	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1412		start_tty(tty);
1413		process_echoes(tty);
1414	}
1415	if (L_ECHO(tty)) {
1416		finish_erasing(ldata);
1417		/* Record the column of first canon char. */
1418		if (ldata->canon_head == ldata->read_head)
1419			echo_set_canon_col(ldata);
1420		echo_char(c, tty);
1421		commit_echoes(tty);
1422	}
1423	/* PARMRK doubling check */
1424	if (c == (unsigned char) '\377' && I_PARMRK(tty))
1425		put_tty_queue(c, ldata);
1426	put_tty_queue(c, ldata);
1427}
1428
1429static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1430{
1431	n_tty_receive_char_inline(tty, c);
1432}
1433
1434static inline void
1435n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1436{
1437	struct n_tty_data *ldata = tty->disc_data;
1438
1439	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1440		start_tty(tty);
1441		process_echoes(tty);
1442	}
1443	if (L_ECHO(tty)) {
1444		finish_erasing(ldata);
1445		/* Record the column of first canon char. */
1446		if (ldata->canon_head == ldata->read_head)
1447			echo_set_canon_col(ldata);
1448		echo_char(c, tty);
1449		commit_echoes(tty);
1450	}
1451	put_tty_queue(c, ldata);
1452}
1453
1454static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1455{
1456	if (I_ISTRIP(tty))
1457		c &= 0x7f;
1458	if (I_IUCLC(tty) && L_IEXTEN(tty))
1459		c = tolower(c);
1460
1461	if (I_IXON(tty)) {
1462		if (c == STOP_CHAR(tty))
1463			stop_tty(tty);
1464		else if (c == START_CHAR(tty) ||
1465			 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1466			  c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1467			  c != SUSP_CHAR(tty))) {
1468			start_tty(tty);
1469			process_echoes(tty);
1470		}
1471	}
1472}
1473
1474static void
1475n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1476{
1477	switch (flag) {
1478	case TTY_BREAK:
1479		n_tty_receive_break(tty);
1480		break;
1481	case TTY_PARITY:
1482	case TTY_FRAME:
1483		n_tty_receive_parity_error(tty, c);
1484		break;
1485	case TTY_OVERRUN:
1486		n_tty_receive_overrun(tty);
1487		break;
1488	default:
1489		tty_err(tty, "unknown flag %d\n", flag);
1490		break;
1491	}
1492}
1493
1494static void
1495n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1496{
1497	struct n_tty_data *ldata = tty->disc_data;
1498
1499	ldata->lnext = 0;
1500	if (likely(flag == TTY_NORMAL)) {
1501		if (I_ISTRIP(tty))
1502			c &= 0x7f;
1503		if (I_IUCLC(tty) && L_IEXTEN(tty))
1504			c = tolower(c);
1505		n_tty_receive_char(tty, c);
1506	} else
1507		n_tty_receive_char_flagged(tty, c, flag);
1508}
1509
1510static void
1511n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1512			   char *fp, int count)
1513{
1514	struct n_tty_data *ldata = tty->disc_data;
1515	size_t n, head;
1516
1517	head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1518	n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1519	memcpy(read_buf_addr(ldata, head), cp, n);
1520	ldata->read_head += n;
1521	cp += n;
1522	count -= n;
1523
1524	head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1525	n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1526	memcpy(read_buf_addr(ldata, head), cp, n);
1527	ldata->read_head += n;
1528}
1529
1530static void
1531n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1532		      char *fp, int count)
1533{
1534	struct n_tty_data *ldata = tty->disc_data;
1535	char flag = TTY_NORMAL;
1536
1537	while (count--) {
1538		if (fp)
1539			flag = *fp++;
1540		if (likely(flag == TTY_NORMAL))
1541			put_tty_queue(*cp++, ldata);
1542		else
1543			n_tty_receive_char_flagged(tty, *cp++, flag);
1544	}
1545}
1546
1547static void
1548n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1549			  char *fp, int count)
1550{
1551	char flag = TTY_NORMAL;
1552
1553	while (count--) {
1554		if (fp)
1555			flag = *fp++;
1556		if (likely(flag == TTY_NORMAL))
1557			n_tty_receive_char_closing(tty, *cp++);
1558	}
1559}
1560
1561static void
1562n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1563			  char *fp, int count)
1564{
1565	struct n_tty_data *ldata = tty->disc_data;
1566	char flag = TTY_NORMAL;
1567
1568	while (count--) {
1569		if (fp)
1570			flag = *fp++;
1571		if (likely(flag == TTY_NORMAL)) {
1572			unsigned char c = *cp++;
1573
1574			if (I_ISTRIP(tty))
1575				c &= 0x7f;
1576			if (I_IUCLC(tty) && L_IEXTEN(tty))
1577				c = tolower(c);
1578			if (L_EXTPROC(tty)) {
1579				put_tty_queue(c, ldata);
1580				continue;
1581			}
1582			if (!test_bit(c, ldata->char_map))
1583				n_tty_receive_char_inline(tty, c);
1584			else if (n_tty_receive_char_special(tty, c) && count) {
1585				if (fp)
1586					flag = *fp++;
1587				n_tty_receive_char_lnext(tty, *cp++, flag);
1588				count--;
1589			}
1590		} else
1591			n_tty_receive_char_flagged(tty, *cp++, flag);
1592	}
1593}
1594
1595static void
1596n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1597		       char *fp, int count)
1598{
1599	struct n_tty_data *ldata = tty->disc_data;
1600	char flag = TTY_NORMAL;
1601
1602	while (count--) {
1603		if (fp)
1604			flag = *fp++;
1605		if (likely(flag == TTY_NORMAL)) {
1606			unsigned char c = *cp++;
1607
1608			if (!test_bit(c, ldata->char_map))
1609				n_tty_receive_char_fast(tty, c);
1610			else if (n_tty_receive_char_special(tty, c) && count) {
1611				if (fp)
1612					flag = *fp++;
1613				n_tty_receive_char_lnext(tty, *cp++, flag);
1614				count--;
1615			}
1616		} else
1617			n_tty_receive_char_flagged(tty, *cp++, flag);
1618	}
1619}
1620
1621static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1622			  char *fp, int count)
1623{
1624	struct n_tty_data *ldata = tty->disc_data;
1625	bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1626
1627	if (ldata->real_raw)
1628		n_tty_receive_buf_real_raw(tty, cp, fp, count);
1629	else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1630		n_tty_receive_buf_raw(tty, cp, fp, count);
1631	else if (tty->closing && !L_EXTPROC(tty))
1632		n_tty_receive_buf_closing(tty, cp, fp, count);
1633	else {
1634		if (ldata->lnext) {
1635			char flag = TTY_NORMAL;
1636
1637			if (fp)
1638				flag = *fp++;
1639			n_tty_receive_char_lnext(tty, *cp++, flag);
1640			count--;
1641		}
1642
1643		if (!preops && !I_PARMRK(tty))
1644			n_tty_receive_buf_fast(tty, cp, fp, count);
1645		else
1646			n_tty_receive_buf_standard(tty, cp, fp, count);
1647
1648		flush_echoes(tty);
1649		if (tty->ops->flush_chars)
1650			tty->ops->flush_chars(tty);
1651	}
1652
1653	if (ldata->icanon && !L_EXTPROC(tty))
1654		return;
1655
1656	/* publish read_head to consumer */
1657	smp_store_release(&ldata->commit_head, ldata->read_head);
1658
1659	if (read_cnt(ldata)) {
1660		kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1661		wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1662	}
1663}
1664
1665/**
1666 *	n_tty_receive_buf_common	-	process input
1667 *	@tty: device to receive input
1668 *	@cp: input chars
1669 *	@fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1670 *	@count: number of input chars in @cp
1671 *
1672 *	Called by the terminal driver when a block of characters has
1673 *	been received. This function must be called from soft contexts
1674 *	not from interrupt context. The driver is responsible for making
1675 *	calls one at a time and in order (or using flush_to_ldisc)
1676 *
1677 *	Returns the # of input chars from @cp which were processed.
1678 *
1679 *	In canonical mode, the maximum line length is 4096 chars (including
1680 *	the line termination char); lines longer than 4096 chars are
1681 *	truncated. After 4095 chars, input data is still processed but
1682 *	not stored. Overflow processing ensures the tty can always
1683 *	receive more input until at least one line can be read.
1684 *
1685 *	In non-canonical mode, the read buffer will only accept 4095 chars;
1686 *	this provides the necessary space for a newline char if the input
1687 *	mode is switched to canonical.
1688 *
1689 *	Note it is possible for the read buffer to _contain_ 4096 chars
1690 *	in non-canonical mode: the read buffer could already contain the
1691 *	maximum canon line of 4096 chars when the mode is switched to
1692 *	non-canonical.
1693 *
1694 *	n_tty_receive_buf()/producer path:
1695 *		claims non-exclusive termios_rwsem
1696 *		publishes commit_head or canon_head
1697 */
1698static int
1699n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1700			 char *fp, int count, int flow)
1701{
1702	struct n_tty_data *ldata = tty->disc_data;
1703	int room, n, rcvd = 0, overflow;
1704
1705	down_read(&tty->termios_rwsem);
1706
1707	do {
1708		/*
1709		 * When PARMRK is set, each input char may take up to 3 chars
1710		 * in the read buf; reduce the buffer space avail by 3x
1711		 *
1712		 * If we are doing input canonicalization, and there are no
1713		 * pending newlines, let characters through without limit, so
1714		 * that erase characters will be handled.  Other excess
1715		 * characters will be beeped.
1716		 *
1717		 * paired with store in *_copy_from_read_buf() -- guarantees
1718		 * the consumer has loaded the data in read_buf up to the new
1719		 * read_tail (so this producer will not overwrite unread data)
1720		 */
1721		size_t tail = smp_load_acquire(&ldata->read_tail);
1722
1723		room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1724		if (I_PARMRK(tty))
1725			room = (room + 2) / 3;
1726		room--;
1727		if (room <= 0) {
1728			overflow = ldata->icanon && ldata->canon_head == tail;
1729			if (overflow && room < 0)
1730				ldata->read_head--;
1731			room = overflow;
1732			ldata->no_room = flow && !room;
1733		} else
1734			overflow = 0;
1735
1736		n = min(count, room);
1737		if (!n)
1738			break;
1739
1740		/* ignore parity errors if handling overflow */
1741		if (!overflow || !fp || *fp != TTY_PARITY)
1742			__receive_buf(tty, cp, fp, n);
1743
1744		cp += n;
1745		if (fp)
1746			fp += n;
1747		count -= n;
1748		rcvd += n;
1749	} while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1750
1751	tty->receive_room = room;
1752
1753	/* Unthrottle if handling overflow on pty */
1754	if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1755		if (overflow) {
1756			tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1757			tty_unthrottle_safe(tty);
1758			__tty_set_flow_change(tty, 0);
1759		}
1760	} else
1761		n_tty_check_throttle(tty);
1762
1763	up_read(&tty->termios_rwsem);
1764
1765	return rcvd;
1766}
1767
1768static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1769			      char *fp, int count)
1770{
1771	n_tty_receive_buf_common(tty, cp, fp, count, 0);
1772}
1773
1774static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1775			      char *fp, int count)
1776{
1777	return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1778}
1779
1780/**
1781 *	n_tty_set_termios	-	termios data changed
1782 *	@tty: terminal
1783 *	@old: previous data
1784 *
1785 *	Called by the tty layer when the user changes termios flags so
1786 *	that the line discipline can plan ahead. This function cannot sleep
1787 *	and is protected from re-entry by the tty layer. The user is
1788 *	guaranteed that this function will not be re-entered or in progress
1789 *	when the ldisc is closed.
1790 *
1791 *	Locking: Caller holds tty->termios_rwsem
1792 */
1793
1794static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1795{
1796	struct n_tty_data *ldata = tty->disc_data;
1797
1798	if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1799		bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1800		ldata->line_start = ldata->read_tail;
1801		if (!L_ICANON(tty) || !read_cnt(ldata)) {
1802			ldata->canon_head = ldata->read_tail;
1803			ldata->push = 0;
1804		} else {
1805			set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1806				ldata->read_flags);
1807			ldata->canon_head = ldata->read_head;
1808			ldata->push = 1;
1809		}
1810		ldata->commit_head = ldata->read_head;
1811		ldata->erasing = 0;
1812		ldata->lnext = 0;
1813	}
1814
1815	ldata->icanon = (L_ICANON(tty) != 0);
1816
1817	if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1818	    I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1819	    I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1820	    I_PARMRK(tty)) {
1821		bitmap_zero(ldata->char_map, 256);
1822
1823		if (I_IGNCR(tty) || I_ICRNL(tty))
1824			set_bit('\r', ldata->char_map);
1825		if (I_INLCR(tty))
1826			set_bit('\n', ldata->char_map);
1827
1828		if (L_ICANON(tty)) {
1829			set_bit(ERASE_CHAR(tty), ldata->char_map);
1830			set_bit(KILL_CHAR(tty), ldata->char_map);
1831			set_bit(EOF_CHAR(tty), ldata->char_map);
1832			set_bit('\n', ldata->char_map);
1833			set_bit(EOL_CHAR(tty), ldata->char_map);
1834			if (L_IEXTEN(tty)) {
1835				set_bit(WERASE_CHAR(tty), ldata->char_map);
1836				set_bit(LNEXT_CHAR(tty), ldata->char_map);
1837				set_bit(EOL2_CHAR(tty), ldata->char_map);
1838				if (L_ECHO(tty))
1839					set_bit(REPRINT_CHAR(tty),
1840						ldata->char_map);
1841			}
1842		}
1843		if (I_IXON(tty)) {
1844			set_bit(START_CHAR(tty), ldata->char_map);
1845			set_bit(STOP_CHAR(tty), ldata->char_map);
1846		}
1847		if (L_ISIG(tty)) {
1848			set_bit(INTR_CHAR(tty), ldata->char_map);
1849			set_bit(QUIT_CHAR(tty), ldata->char_map);
1850			set_bit(SUSP_CHAR(tty), ldata->char_map);
1851		}
1852		clear_bit(__DISABLED_CHAR, ldata->char_map);
1853		ldata->raw = 0;
1854		ldata->real_raw = 0;
1855	} else {
1856		ldata->raw = 1;
1857		if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1858		    (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1859		    (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1860			ldata->real_raw = 1;
1861		else
1862			ldata->real_raw = 0;
1863	}
1864	/*
1865	 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1866	 * been stopped by STOP_CHAR(tty) before it.
1867	 */
1868	if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1869		start_tty(tty);
1870		process_echoes(tty);
1871	}
1872
1873	/* The termios change make the tty ready for I/O */
1874	wake_up_interruptible(&tty->write_wait);
1875	wake_up_interruptible(&tty->read_wait);
1876}
1877
1878/**
1879 *	n_tty_close		-	close the ldisc for this tty
1880 *	@tty: device
1881 *
1882 *	Called from the terminal layer when this line discipline is
1883 *	being shut down, either because of a close or becsuse of a
1884 *	discipline change. The function will not be called while other
1885 *	ldisc methods are in progress.
1886 */
1887
1888static void n_tty_close(struct tty_struct *tty)
1889{
1890	struct n_tty_data *ldata = tty->disc_data;
1891
1892	if (tty->link)
1893		n_tty_packet_mode_flush(tty);
1894
1895	vfree(ldata);
1896	tty->disc_data = NULL;
1897}
1898
1899/**
1900 *	n_tty_open		-	open an ldisc
1901 *	@tty: terminal to open
1902 *
1903 *	Called when this line discipline is being attached to the
1904 *	terminal device. Can sleep. Called serialized so that no
1905 *	other events will occur in parallel. No further open will occur
1906 *	until a close.
1907 */
1908
1909static int n_tty_open(struct tty_struct *tty)
1910{
1911	struct n_tty_data *ldata;
1912
1913	/* Currently a malloc failure here can panic */
1914	ldata = vzalloc(sizeof(*ldata));
1915	if (!ldata)
1916		return -ENOMEM;
1917
1918	ldata->overrun_time = jiffies;
1919	mutex_init(&ldata->atomic_read_lock);
1920	mutex_init(&ldata->output_lock);
1921
1922	tty->disc_data = ldata;
 
 
 
 
 
 
1923	tty->closing = 0;
1924	/* indicate buffer work may resume */
1925	clear_bit(TTY_LDISC_HALTED, &tty->flags);
1926	n_tty_set_termios(tty, NULL);
1927	tty_unthrottle(tty);
 
1928	return 0;
 
 
1929}
1930
1931static inline int input_available_p(struct tty_struct *tty, int poll)
1932{
1933	struct n_tty_data *ldata = tty->disc_data;
1934	int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1935
1936	if (ldata->icanon && !L_EXTPROC(tty))
1937		return ldata->canon_head != ldata->read_tail;
1938	else
1939		return ldata->commit_head - ldata->read_tail >= amt;
1940}
1941
 
 
 
 
 
 
 
 
 
 
 
 
1942/**
1943 *	copy_from_read_buf	-	copy read data directly
1944 *	@tty: terminal device
1945 *	@b: user data
1946 *	@nr: size of data
1947 *
1948 *	Helper function to speed up n_tty_read.  It is only called when
1949 *	ICANON is off; it copies characters straight from the tty queue to
1950 *	user space directly.  It can be profitably called twice; once to
1951 *	drain the space from the tail pointer to the (physical) end of the
1952 *	buffer, and once to drain the space from the (physical) beginning of
1953 *	the buffer to head pointer.
1954 *
1955 *	Called under the ldata->atomic_read_lock sem
1956 *
1957 *	n_tty_read()/consumer path:
1958 *		caller holds non-exclusive termios_rwsem
1959 *		read_tail published
1960 */
1961
1962static int copy_from_read_buf(struct tty_struct *tty,
1963				      unsigned char __user **b,
1964				      size_t *nr)
1965
1966{
1967	struct n_tty_data *ldata = tty->disc_data;
1968	int retval;
1969	size_t n;
1970	bool is_eof;
1971	size_t head = smp_load_acquire(&ldata->commit_head);
1972	size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1973
1974	retval = 0;
1975	n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1976	n = min(*nr, n);
1977	if (n) {
1978		unsigned char *from = read_buf_addr(ldata, tail);
1979		retval = copy_to_user(*b, from, n);
1980		n -= retval;
1981		is_eof = n == 1 && *from == EOF_CHAR(tty);
1982		tty_audit_add_data(tty, from, n);
1983		zero_buffer(tty, from, n);
1984		smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1985		/* Turn single EOF into zero-length read */
1986		if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1987		    (head == ldata->read_tail))
1988			n = 0;
1989		*b += n;
1990		*nr -= n;
1991	}
1992	return retval;
1993}
1994
1995/**
1996 *	canon_copy_from_read_buf	-	copy read data in canonical mode
1997 *	@tty: terminal device
1998 *	@b: user data
1999 *	@nr: size of data
2000 *
2001 *	Helper function for n_tty_read.  It is only called when ICANON is on;
2002 *	it copies one line of input up to and including the line-delimiting
2003 *	character into the user-space buffer.
2004 *
2005 *	NB: When termios is changed from non-canonical to canonical mode and
2006 *	the read buffer contains data, n_tty_set_termios() simulates an EOF
2007 *	push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2008 *	This causes data already processed as input to be immediately available
2009 *	as input although a newline has not been received.
2010 *
2011 *	Called under the atomic_read_lock mutex
2012 *
2013 *	n_tty_read()/consumer path:
2014 *		caller holds non-exclusive termios_rwsem
2015 *		read_tail published
2016 */
2017
2018static int canon_copy_from_read_buf(struct tty_struct *tty,
2019				    unsigned char __user **b,
2020				    size_t *nr)
2021{
2022	struct n_tty_data *ldata = tty->disc_data;
2023	size_t n, size, more, c;
2024	size_t eol;
2025	size_t tail;
2026	int ret, found = 0;
2027
2028	/* N.B. avoid overrun if nr == 0 */
2029	if (!*nr)
2030		return 0;
2031
2032	n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2033
2034	tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2035	size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2036
2037	n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2038		    __func__, *nr, tail, n, size);
2039
2040	eol = find_next_bit(ldata->read_flags, size, tail);
2041	more = n - (size - tail);
2042	if (eol == N_TTY_BUF_SIZE && more) {
2043		/* scan wrapped without finding set bit */
2044		eol = find_next_bit(ldata->read_flags, more, 0);
2045		found = eol != more;
2046	} else
2047		found = eol != size;
2048
2049	n = eol - tail;
2050	if (n > N_TTY_BUF_SIZE)
2051		n += N_TTY_BUF_SIZE;
2052	c = n + found;
2053
2054	if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
2055		c = min(*nr, c);
2056		n = c;
2057	}
2058
2059	n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2060		    __func__, eol, found, n, c, tail, more);
2061
2062	ret = tty_copy_to_user(tty, *b, tail, n);
2063	if (ret)
2064		return -EFAULT;
2065	*b += n;
2066	*nr -= n;
2067
2068	if (found)
2069		clear_bit(eol, ldata->read_flags);
2070	smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2071
2072	if (found) {
2073		if (!ldata->push)
2074			ldata->line_start = ldata->read_tail;
2075		else
2076			ldata->push = 0;
2077		tty_audit_push();
2078	}
2079	return 0;
2080}
2081
2082extern ssize_t redirected_tty_write(struct file *, const char __user *,
2083							size_t, loff_t *);
2084
2085/**
2086 *	job_control		-	check job control
2087 *	@tty: tty
2088 *	@file: file handle
2089 *
2090 *	Perform job control management checks on this file/tty descriptor
2091 *	and if appropriate send any needed signals and return a negative
2092 *	error code if action should be taken.
2093 *
2094 *	Locking: redirected write test is safe
2095 *		 current->signal->tty check is safe
2096 *		 ctrl_lock to safely reference tty->pgrp
2097 */
2098
2099static int job_control(struct tty_struct *tty, struct file *file)
2100{
2101	/* Job control check -- must be done at start and after
2102	   every sleep (POSIX.1 7.1.1.4). */
2103	/* NOTE: not yet done after every sleep pending a thorough
2104	   check of the logic of this change. -- jlc */
2105	/* don't stop on /dev/console */
2106	if (file->f_op->write == redirected_tty_write)
2107		return 0;
2108
2109	return __tty_check_change(tty, SIGTTIN);
2110}
2111
2112
2113/**
2114 *	n_tty_read		-	read function for tty
2115 *	@tty: tty device
2116 *	@file: file object
2117 *	@buf: userspace buffer pointer
2118 *	@nr: size of I/O
2119 *
2120 *	Perform reads for the line discipline. We are guaranteed that the
2121 *	line discipline will not be closed under us but we may get multiple
2122 *	parallel readers and must handle this ourselves. We may also get
2123 *	a hangup. Always called in user context, may sleep.
2124 *
2125 *	This code must be sure never to sleep through a hangup.
2126 *
2127 *	n_tty_read()/consumer path:
2128 *		claims non-exclusive termios_rwsem
2129 *		publishes read_tail
2130 */
2131
2132static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2133			 unsigned char __user *buf, size_t nr)
2134{
2135	struct n_tty_data *ldata = tty->disc_data;
2136	unsigned char __user *b = buf;
2137	DEFINE_WAIT_FUNC(wait, woken_wake_function);
2138	int c;
2139	int minimum, time;
2140	ssize_t retval = 0;
2141	long timeout;
2142	int packet;
2143	size_t tail;
2144
2145	c = job_control(tty, file);
2146	if (c < 0)
2147		return c;
2148
2149	/*
2150	 *	Internal serialization of reads.
2151	 */
2152	if (file->f_flags & O_NONBLOCK) {
2153		if (!mutex_trylock(&ldata->atomic_read_lock))
2154			return -EAGAIN;
2155	} else {
2156		if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2157			return -ERESTARTSYS;
2158	}
2159
2160	down_read(&tty->termios_rwsem);
2161
2162	minimum = time = 0;
2163	timeout = MAX_SCHEDULE_TIMEOUT;
2164	if (!ldata->icanon) {
2165		minimum = MIN_CHAR(tty);
2166		if (minimum) {
2167			time = (HZ / 10) * TIME_CHAR(tty);
2168		} else {
2169			timeout = (HZ / 10) * TIME_CHAR(tty);
2170			minimum = 1;
2171		}
2172	}
2173
2174	packet = tty->packet;
2175	tail = ldata->read_tail;
2176
2177	add_wait_queue(&tty->read_wait, &wait);
2178	while (nr) {
2179		/* First test for status change. */
2180		if (packet && tty->link->ctrl_status) {
2181			unsigned char cs;
2182			if (b != buf)
2183				break;
2184			spin_lock_irq(&tty->link->ctrl_lock);
2185			cs = tty->link->ctrl_status;
2186			tty->link->ctrl_status = 0;
2187			spin_unlock_irq(&tty->link->ctrl_lock);
2188			if (put_user(cs, b)) {
2189				retval = -EFAULT;
2190				break;
2191			}
2192			b++;
2193			nr--;
2194			break;
2195		}
2196
 
 
2197		if (!input_available_p(tty, 0)) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2198			up_read(&tty->termios_rwsem);
2199			tty_buffer_flush_work(tty->port);
2200			down_read(&tty->termios_rwsem);
2201			if (!input_available_p(tty, 0)) {
2202				if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2203					retval = -EIO;
2204					break;
2205				}
2206				if (tty_hung_up_p(file))
2207					break;
2208				/*
2209				 * Abort readers for ttys which never actually
2210				 * get hung up.  See __tty_hangup().
2211				 */
2212				if (test_bit(TTY_HUPPING, &tty->flags))
2213					break;
2214				if (!timeout)
2215					break;
2216				if (tty_io_nonblock(tty, file)) {
2217					retval = -EAGAIN;
2218					break;
2219				}
2220				if (signal_pending(current)) {
2221					retval = -ERESTARTSYS;
2222					break;
2223				}
2224				up_read(&tty->termios_rwsem);
2225
2226				timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2227						timeout);
2228
2229				down_read(&tty->termios_rwsem);
2230				continue;
2231			}
2232		}
2233
2234		if (ldata->icanon && !L_EXTPROC(tty)) {
2235			retval = canon_copy_from_read_buf(tty, &b, &nr);
2236			if (retval)
2237				break;
2238		} else {
2239			int uncopied;
2240
2241			/* Deal with packet mode. */
2242			if (packet && b == buf) {
2243				if (put_user(TIOCPKT_DATA, b)) {
2244					retval = -EFAULT;
2245					break;
2246				}
2247				b++;
2248				nr--;
2249			}
2250
2251			uncopied = copy_from_read_buf(tty, &b, &nr);
2252			uncopied += copy_from_read_buf(tty, &b, &nr);
2253			if (uncopied) {
2254				retval = -EFAULT;
2255				break;
2256			}
2257		}
2258
2259		n_tty_check_unthrottle(tty);
2260
2261		if (b - buf >= minimum)
2262			break;
2263		if (time)
2264			timeout = time;
2265	}
2266	if (tail != ldata->read_tail)
2267		n_tty_kick_worker(tty);
2268	up_read(&tty->termios_rwsem);
2269
2270	remove_wait_queue(&tty->read_wait, &wait);
2271	mutex_unlock(&ldata->atomic_read_lock);
2272
2273	if (b - buf)
2274		retval = b - buf;
2275
2276	return retval;
2277}
2278
2279/**
2280 *	n_tty_write		-	write function for tty
2281 *	@tty: tty device
2282 *	@file: file object
2283 *	@buf: userspace buffer pointer
2284 *	@nr: size of I/O
2285 *
2286 *	Write function of the terminal device.  This is serialized with
2287 *	respect to other write callers but not to termios changes, reads
2288 *	and other such events.  Since the receive code will echo characters,
2289 *	thus calling driver write methods, the output_lock is used in
2290 *	the output processing functions called here as well as in the
2291 *	echo processing function to protect the column state and space
2292 *	left in the buffer.
2293 *
2294 *	This code must be sure never to sleep through a hangup.
2295 *
2296 *	Locking: output_lock to protect column state and space left
2297 *		 (note that the process_output*() functions take this
2298 *		  lock themselves)
2299 */
2300
2301static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2302			   const unsigned char *buf, size_t nr)
2303{
2304	const unsigned char *b = buf;
2305	DEFINE_WAIT_FUNC(wait, woken_wake_function);
2306	int c;
2307	ssize_t retval = 0;
2308
2309	/* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2310	if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2311		retval = tty_check_change(tty);
2312		if (retval)
2313			return retval;
2314	}
2315
2316	down_read(&tty->termios_rwsem);
2317
2318	/* Write out any echoed characters that are still pending */
2319	process_echoes(tty);
2320
2321	add_wait_queue(&tty->write_wait, &wait);
2322	while (1) {
2323		if (signal_pending(current)) {
2324			retval = -ERESTARTSYS;
2325			break;
2326		}
2327		if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2328			retval = -EIO;
2329			break;
2330		}
2331		if (O_OPOST(tty)) {
2332			while (nr > 0) {
2333				ssize_t num = process_output_block(tty, b, nr);
2334				if (num < 0) {
2335					if (num == -EAGAIN)
2336						break;
2337					retval = num;
2338					goto break_out;
2339				}
2340				b += num;
2341				nr -= num;
2342				if (nr == 0)
2343					break;
2344				c = *b;
2345				if (process_output(c, tty) < 0)
2346					break;
2347				b++; nr--;
2348			}
2349			if (tty->ops->flush_chars)
2350				tty->ops->flush_chars(tty);
2351		} else {
2352			struct n_tty_data *ldata = tty->disc_data;
2353
2354			while (nr > 0) {
2355				mutex_lock(&ldata->output_lock);
2356				c = tty->ops->write(tty, b, nr);
2357				mutex_unlock(&ldata->output_lock);
2358				if (c < 0) {
2359					retval = c;
2360					goto break_out;
2361				}
2362				if (!c)
2363					break;
2364				b += c;
2365				nr -= c;
2366			}
2367		}
2368		if (!nr)
2369			break;
2370		if (tty_io_nonblock(tty, file)) {
2371			retval = -EAGAIN;
2372			break;
2373		}
2374		up_read(&tty->termios_rwsem);
2375
2376		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2377
2378		down_read(&tty->termios_rwsem);
2379	}
2380break_out:
2381	remove_wait_queue(&tty->write_wait, &wait);
2382	if (nr && tty->fasync)
2383		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2384	up_read(&tty->termios_rwsem);
2385	return (b - buf) ? b - buf : retval;
2386}
2387
2388/**
2389 *	n_tty_poll		-	poll method for N_TTY
2390 *	@tty: terminal device
2391 *	@file: file accessing it
2392 *	@wait: poll table
2393 *
2394 *	Called when the line discipline is asked to poll() for data or
2395 *	for special events. This code is not serialized with respect to
2396 *	other events save open/close.
2397 *
2398 *	This code must be sure never to sleep through a hangup.
2399 *	Called without the kernel lock held - fine
2400 */
2401
2402static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2403							poll_table *wait)
2404{
2405	__poll_t mask = 0;
2406
2407	poll_wait(file, &tty->read_wait, wait);
2408	poll_wait(file, &tty->write_wait, wait);
 
 
2409	if (input_available_p(tty, 1))
2410		mask |= EPOLLIN | EPOLLRDNORM;
2411	else {
2412		tty_buffer_flush_work(tty->port);
2413		if (input_available_p(tty, 1))
2414			mask |= EPOLLIN | EPOLLRDNORM;
2415	}
2416	if (tty->packet && tty->link->ctrl_status)
2417		mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2418	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2419		mask |= EPOLLHUP;
2420	if (tty_hung_up_p(file))
2421		mask |= EPOLLHUP;
2422	if (tty->ops->write && !tty_is_writelocked(tty) &&
2423			tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2424			tty_write_room(tty) > 0)
2425		mask |= EPOLLOUT | EPOLLWRNORM;
2426	return mask;
2427}
2428
2429static unsigned long inq_canon(struct n_tty_data *ldata)
2430{
2431	size_t nr, head, tail;
2432
2433	if (ldata->canon_head == ldata->read_tail)
2434		return 0;
2435	head = ldata->canon_head;
2436	tail = ldata->read_tail;
2437	nr = head - tail;
2438	/* Skip EOF-chars.. */
2439	while (MASK(head) != MASK(tail)) {
2440		if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2441		    read_buf(ldata, tail) == __DISABLED_CHAR)
2442			nr--;
2443		tail++;
2444	}
2445	return nr;
2446}
2447
2448static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2449		       unsigned int cmd, unsigned long arg)
2450{
2451	struct n_tty_data *ldata = tty->disc_data;
2452	int retval;
2453
2454	switch (cmd) {
2455	case TIOCOUTQ:
2456		return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2457	case TIOCINQ:
2458		down_write(&tty->termios_rwsem);
2459		if (L_ICANON(tty) && !L_EXTPROC(tty))
2460			retval = inq_canon(ldata);
2461		else
2462			retval = read_cnt(ldata);
2463		up_write(&tty->termios_rwsem);
2464		return put_user(retval, (unsigned int __user *) arg);
2465	default:
2466		return n_tty_ioctl_helper(tty, file, cmd, arg);
2467	}
2468}
2469
2470static struct tty_ldisc_ops n_tty_ops = {
2471	.magic           = TTY_LDISC_MAGIC,
2472	.name            = "n_tty",
2473	.open            = n_tty_open,
2474	.close           = n_tty_close,
2475	.flush_buffer    = n_tty_flush_buffer,
2476	.read            = n_tty_read,
2477	.write           = n_tty_write,
2478	.ioctl           = n_tty_ioctl,
2479	.set_termios     = n_tty_set_termios,
2480	.poll            = n_tty_poll,
2481	.receive_buf     = n_tty_receive_buf,
2482	.write_wakeup    = n_tty_write_wakeup,
2483	.receive_buf2	 = n_tty_receive_buf2,
2484};
2485
2486/**
2487 *	n_tty_inherit_ops	-	inherit N_TTY methods
2488 *	@ops: struct tty_ldisc_ops where to save N_TTY methods
2489 *
2490 *	Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2491 */
2492
2493void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2494{
2495	*ops = n_tty_ops;
2496	ops->owner = NULL;
2497	ops->refcount = ops->flags = 0;
2498}
2499EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2500
2501void __init n_tty_init(void)
2502{
2503	tty_register_ldisc(N_TTY, &n_tty_ops);
2504}