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