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
  53
  54/* number of characters left in xmit buffer before select has we have room */
  55#define WAKEUP_CHARS 256
  56
  57/*
  58 * This defines the low- and high-watermarks for throttling and
  59 * unthrottling the TTY driver.  These watermarks are used for
  60 * controlling the space in the read buffer.
  61 */
  62#define TTY_THRESHOLD_THROTTLE		128 /* now based on remaining room */
  63#define TTY_THRESHOLD_UNTHROTTLE	128
  64
  65/*
  66 * Special byte codes used in the echo buffer to represent operations
  67 * or special handling of characters.  Bytes in the echo buffer that
  68 * are not part of such special blocks are treated as normal character
  69 * codes.
  70 */
  71#define ECHO_OP_START 0xff
  72#define ECHO_OP_MOVE_BACK_COL 0x80
  73#define ECHO_OP_SET_CANON_COL 0x81
  74#define ECHO_OP_ERASE_TAB 0x82
  75
  76static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
  77			       unsigned char __user *ptr)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  78{
  79	tty_audit_add_data(tty, &x, 1);
  80	return put_user(x, ptr);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  81}
  82
  83/**
  84 *	n_tty_set__room	-	receive space
  85 *	@tty: terminal
  86 *
  87 *	Called by the driver to find out how much data it is
  88 *	permitted to feed to the line discipline without any being lost
  89 *	and thus to manage flow control. Not serialized. Answers for the
  90 *	"instant".
 
 
  91 */
  92
  93static void n_tty_set_room(struct tty_struct *tty)
  94{
  95	/* tty->read_cnt is not read locked ? */
  96	int	left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
  97	int old_left;
  98
  99	/*
 100	 * If we are doing input canonicalization, and there are no
 101	 * pending newlines, let characters through without limit, so
 102	 * that erase characters will be handled.  Other excess
 103	 * characters will be beeped.
 104	 */
 105	if (left <= 0)
 106		left = tty->icanon && !tty->canon_data;
 107	old_left = tty->receive_room;
 108	tty->receive_room = left;
 109
 110	/* Did this open up the receive buffer? We may need to flip */
 111	if (left && !old_left)
 112		schedule_work(&tty->buf.work);
 113}
 114
 115static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
 116{
 117	if (tty->read_cnt < N_TTY_BUF_SIZE) {
 118		tty->read_buf[tty->read_head] = c;
 119		tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
 120		tty->read_cnt++;
 121	}
 122}
 123
 
 
 
 
 
 
 
 
 
 
 
 
 124/**
 125 *	put_tty_queue		-	add character to tty
 126 *	@c: character
 127 *	@tty: tty device
 128 *
 129 *	Add a character to the tty read_buf queue. This is done under the
 130 *	read_lock to serialize character addition and also to protect us
 131 *	against parallel reads or flushes
 132 */
 133
 134static void put_tty_queue(unsigned char c, struct tty_struct *tty)
 135{
 136	unsigned long flags;
 
 
 
 
 
 
 
 137	/*
 138	 *	The problem of stomping on the buffers ends here.
 139	 *	Why didn't anyone see this one coming? --AJK
 140	*/
 141	spin_lock_irqsave(&tty->read_lock, flags);
 142	put_tty_queue_nolock(c, tty);
 143	spin_unlock_irqrestore(&tty->read_lock, flags);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 144}
 145
 146/**
 147 *	check_unthrottle	-	allow new receive data
 148 *	@tty; tty device
 
 149 *
 150 *	Check whether to call the driver unthrottle functions
 151 *
 152 *	Can sleep, may be called under the atomic_read_lock mutex but
 153 *	this is not guaranteed.
 154 */
 155static void check_unthrottle(struct tty_struct *tty)
 
 156{
 157	if (tty->count)
 158		tty_unthrottle(tty);
 159}
 160
 161/**
 162 *	reset_buffer_flags	-	reset buffer state
 163 *	@tty: terminal to reset
 164 *
 165 *	Reset the read buffer counters, clear the flags,
 166 *	and make sure the driver is unthrottled. Called
 167 *	from n_tty_open() and n_tty_flush_buffer().
 168 *
 169 *	Locking: tty_read_lock for read fields.
 
 170 */
 171
 172static void reset_buffer_flags(struct tty_struct *tty)
 173{
 174	unsigned long flags;
 
 
 
 
 175
 176	spin_lock_irqsave(&tty->read_lock, flags);
 177	tty->read_head = tty->read_tail = tty->read_cnt = 0;
 178	spin_unlock_irqrestore(&tty->read_lock, flags);
 179
 180	mutex_lock(&tty->echo_lock);
 181	tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
 182	mutex_unlock(&tty->echo_lock);
 183
 184	tty->canon_head = tty->canon_data = tty->erasing = 0;
 185	memset(&tty->read_flags, 0, sizeof tty->read_flags);
 186	n_tty_set_room(tty);
 187}
 188
 189/**
 190 *	n_tty_flush_buffer	-	clean input queue
 191 *	@tty:	terminal device
 192 *
 193 *	Flush the input buffer. Called when the line discipline is
 194 *	being closed, when the tty layer wants the buffer flushed (eg
 195 *	at hangup) or when the N_TTY line discipline internally has to
 196 *	clean the pending queue (for example some signals).
 197 *
 198 *	Locking: ctrl_lock, read_lock.
 199 */
 200
 201static void n_tty_flush_buffer(struct tty_struct *tty)
 202{
 203	unsigned long flags;
 204	/* clear everything and unthrottle the driver */
 205	reset_buffer_flags(tty);
 206
 207	if (!tty->link)
 208		return;
 209
 210	spin_lock_irqsave(&tty->ctrl_lock, flags);
 211	if (tty->link->packet) {
 
 212		tty->ctrl_status |= TIOCPKT_FLUSHREAD;
 
 213		wake_up_interruptible(&tty->link->read_wait);
 214	}
 215	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 216}
 217
 218/**
 219 *	n_tty_chars_in_buffer	-	report available bytes
 220 *	@tty: tty device
 221 *
 222 *	Report the number of characters buffered to be delivered to user
 223 *	at this instant in time.
 
 224 *
 225 *	Locking: read_lock
 
 
 
 226 */
 227
 228static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
 229{
 230	unsigned long flags;
 231	ssize_t n = 0;
 232
 233	spin_lock_irqsave(&tty->read_lock, flags);
 234	if (!tty->icanon) {
 235		n = tty->read_cnt;
 236	} else if (tty->canon_data) {
 237		n = (tty->canon_head > tty->read_tail) ?
 238			tty->canon_head - tty->read_tail :
 239			tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
 240	}
 241	spin_unlock_irqrestore(&tty->read_lock, flags);
 242	return n;
 243}
 244
 245/**
 246 *	is_utf8_continuation	-	utf8 multibyte check
 247 *	@c: byte to check
 248 *
 249 *	Returns true if the utf8 character 'c' is a multibyte continuation
 250 *	character. We use this to correctly compute the on screen size
 251 *	of the character when printing
 252 */
 253
 254static inline int is_utf8_continuation(unsigned char c)
 255{
 256	return (c & 0xc0) == 0x80;
 257}
 258
 259/**
 260 *	is_continuation		-	multibyte check
 261 *	@c: byte to check
 262 *
 263 *	Returns true if the utf8 character 'c' is a multibyte continuation
 264 *	character and the terminal is in unicode mode.
 265 */
 266
 267static inline int is_continuation(unsigned char c, struct tty_struct *tty)
 268{
 269	return I_IUTF8(tty) && is_utf8_continuation(c);
 270}
 271
 272/**
 273 *	do_output_char			-	output one character
 274 *	@c: character (or partial unicode symbol)
 275 *	@tty: terminal device
 276 *	@space: space available in tty driver write buffer
 277 *
 278 *	This is a helper function that handles one output character
 279 *	(including special characters like TAB, CR, LF, etc.),
 280 *	doing OPOST processing and putting the results in the
 281 *	tty driver's write buffer.
 282 *
 283 *	Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
 284 *	and NLDLY.  They simply aren't relevant in the world today.
 285 *	If you ever need them, add them here.
 286 *
 287 *	Returns the number of bytes of buffer space used or -1 if
 288 *	no space left.
 289 *
 290 *	Locking: should be called under the output_lock to protect
 291 *		 the column state and space left in the buffer
 292 */
 293
 294static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
 295{
 
 296	int	spaces;
 297
 298	if (!space)
 299		return -1;
 300
 301	switch (c) {
 302	case '\n':
 303		if (O_ONLRET(tty))
 304			tty->column = 0;
 305		if (O_ONLCR(tty)) {
 306			if (space < 2)
 307				return -1;
 308			tty->canon_column = tty->column = 0;
 309			tty->ops->write(tty, "\r\n", 2);
 310			return 2;
 311		}
 312		tty->canon_column = tty->column;
 313		break;
 314	case '\r':
 315		if (O_ONOCR(tty) && tty->column == 0)
 316			return 0;
 317		if (O_OCRNL(tty)) {
 318			c = '\n';
 319			if (O_ONLRET(tty))
 320				tty->canon_column = tty->column = 0;
 321			break;
 322		}
 323		tty->canon_column = tty->column = 0;
 324		break;
 325	case '\t':
 326		spaces = 8 - (tty->column & 7);
 327		if (O_TABDLY(tty) == XTABS) {
 328			if (space < spaces)
 329				return -1;
 330			tty->column += spaces;
 331			tty->ops->write(tty, "        ", spaces);
 332			return spaces;
 333		}
 334		tty->column += spaces;
 335		break;
 336	case '\b':
 337		if (tty->column > 0)
 338			tty->column--;
 339		break;
 340	default:
 341		if (!iscntrl(c)) {
 342			if (O_OLCUC(tty))
 343				c = toupper(c);
 344			if (!is_continuation(c, tty))
 345				tty->column++;
 346		}
 347		break;
 348	}
 349
 350	tty_put_char(tty, c);
 351	return 1;
 352}
 353
 354/**
 355 *	process_output			-	output post processor
 356 *	@c: character (or partial unicode symbol)
 357 *	@tty: terminal device
 358 *
 359 *	Output one character with OPOST processing.
 360 *	Returns -1 when the output device is full and the character
 361 *	must be retried.
 362 *
 363 *	Locking: output_lock to protect column state and space left
 364 *		 (also, this is called from n_tty_write under the
 365 *		  tty layer write lock)
 366 */
 367
 368static int process_output(unsigned char c, struct tty_struct *tty)
 369{
 
 370	int	space, retval;
 371
 372	mutex_lock(&tty->output_lock);
 373
 374	space = tty_write_room(tty);
 375	retval = do_output_char(c, tty, space);
 376
 377	mutex_unlock(&tty->output_lock);
 378	if (retval < 0)
 379		return -1;
 380	else
 381		return 0;
 382}
 383
 384/**
 385 *	process_output_block		-	block post processor
 386 *	@tty: terminal device
 387 *	@buf: character buffer
 388 *	@nr: number of bytes to output
 389 *
 390 *	Output a block of characters with OPOST processing.
 391 *	Returns the number of characters output.
 392 *
 393 *	This path is used to speed up block console writes, among other
 394 *	things when processing blocks of output data. It handles only
 395 *	the simple cases normally found and helps to generate blocks of
 396 *	symbols for the console driver and thus improve performance.
 397 *
 398 *	Locking: output_lock to protect column state and space left
 399 *		 (also, this is called from n_tty_write under the
 400 *		  tty layer write lock)
 401 */
 402
 403static ssize_t process_output_block(struct tty_struct *tty,
 404				    const unsigned char *buf, unsigned int nr)
 405{
 
 406	int	space;
 407	int	i;
 408	const unsigned char *cp;
 409
 410	mutex_lock(&tty->output_lock);
 411
 412	space = tty_write_room(tty);
 413	if (!space) {
 414		mutex_unlock(&tty->output_lock);
 415		return 0;
 416	}
 417	if (nr > space)
 418		nr = space;
 419
 420	for (i = 0, cp = buf; i < nr; i++, cp++) {
 421		unsigned char c = *cp;
 422
 423		switch (c) {
 424		case '\n':
 425			if (O_ONLRET(tty))
 426				tty->column = 0;
 427			if (O_ONLCR(tty))
 428				goto break_out;
 429			tty->canon_column = tty->column;
 430			break;
 431		case '\r':
 432			if (O_ONOCR(tty) && tty->column == 0)
 433				goto break_out;
 434			if (O_OCRNL(tty))
 435				goto break_out;
 436			tty->canon_column = tty->column = 0;
 437			break;
 438		case '\t':
 439			goto break_out;
 440		case '\b':
 441			if (tty->column > 0)
 442				tty->column--;
 443			break;
 444		default:
 445			if (!iscntrl(c)) {
 446				if (O_OLCUC(tty))
 447					goto break_out;
 448				if (!is_continuation(c, tty))
 449					tty->column++;
 450			}
 451			break;
 452		}
 453	}
 454break_out:
 455	i = tty->ops->write(tty, buf, i);
 456
 457	mutex_unlock(&tty->output_lock);
 458	return i;
 459}
 460
 461/**
 462 *	process_echoes	-	write pending echo characters
 463 *	@tty: terminal device
 464 *
 465 *	Write previously buffered echo (and other ldisc-generated)
 466 *	characters to the tty.
 467 *
 468 *	Characters generated by the ldisc (including echoes) need to
 469 *	be buffered because the driver's write buffer can fill during
 470 *	heavy program output.  Echoing straight to the driver will
 471 *	often fail under these conditions, causing lost characters and
 472 *	resulting mismatches of ldisc state information.
 473 *
 474 *	Since the ldisc state must represent the characters actually sent
 475 *	to the driver at the time of the write, operations like certain
 476 *	changes in column state are also saved in the buffer and executed
 477 *	here.
 478 *
 479 *	A circular fifo buffer is used so that the most recent characters
 480 *	are prioritized.  Also, when control characters are echoed with a
 481 *	prefixed "^", the pair is treated atomically and thus not separated.
 482 *
 483 *	Locking: output_lock to protect column state and space left,
 484 *		 echo_lock to protect the echo buffer
 485 */
 486
 487static void process_echoes(struct tty_struct *tty)
 488{
 489	int	space, nr;
 
 
 490	unsigned char c;
 491	unsigned char *cp, *buf_end;
 492
 493	if (!tty->echo_cnt)
 494		return;
 495
 496	mutex_lock(&tty->output_lock);
 497	mutex_lock(&tty->echo_lock);
 498
 499	space = tty_write_room(tty);
 500
 501	buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
 502	cp = tty->echo_buf + tty->echo_pos;
 503	nr = tty->echo_cnt;
 504	while (nr > 0) {
 505		c = *cp;
 506		if (c == ECHO_OP_START) {
 507			unsigned char op;
 508			unsigned char *opp;
 509			int no_space_left = 0;
 510
 511			/*
 512			 * If the buffer byte is the start of a multi-byte
 513			 * operation, get the next byte, which is either the
 514			 * op code or a control character value.
 515			 */
 516			opp = cp + 1;
 517			if (opp == buf_end)
 518				opp -= N_TTY_BUF_SIZE;
 519			op = *opp;
 520
 521			switch (op) {
 522				unsigned int num_chars, num_bs;
 523
 524			case ECHO_OP_ERASE_TAB:
 525				if (++opp == buf_end)
 526					opp -= N_TTY_BUF_SIZE;
 527				num_chars = *opp;
 528
 529				/*
 530				 * Determine how many columns to go back
 531				 * in order to erase the tab.
 532				 * This depends on the number of columns
 533				 * used by other characters within the tab
 534				 * area.  If this (modulo 8) count is from
 535				 * the start of input rather than from a
 536				 * previous tab, we offset by canon column.
 537				 * Otherwise, tab spacing is normal.
 538				 */
 539				if (!(num_chars & 0x80))
 540					num_chars += tty->canon_column;
 541				num_bs = 8 - (num_chars & 7);
 542
 543				if (num_bs > space) {
 544					no_space_left = 1;
 545					break;
 546				}
 547				space -= num_bs;
 548				while (num_bs--) {
 549					tty_put_char(tty, '\b');
 550					if (tty->column > 0)
 551						tty->column--;
 552				}
 553				cp += 3;
 554				nr -= 3;
 555				break;
 556
 557			case ECHO_OP_SET_CANON_COL:
 558				tty->canon_column = tty->column;
 559				cp += 2;
 560				nr -= 2;
 561				break;
 562
 563			case ECHO_OP_MOVE_BACK_COL:
 564				if (tty->column > 0)
 565					tty->column--;
 566				cp += 2;
 567				nr -= 2;
 568				break;
 569
 570			case ECHO_OP_START:
 571				/* This is an escaped echo op start code */
 572				if (!space) {
 573					no_space_left = 1;
 574					break;
 575				}
 576				tty_put_char(tty, ECHO_OP_START);
 577				tty->column++;
 578				space--;
 579				cp += 2;
 580				nr -= 2;
 581				break;
 582
 583			default:
 584				/*
 585				 * If the op is not a special byte code,
 586				 * it is a ctrl char tagged to be echoed
 587				 * as "^X" (where X is the letter
 588				 * representing the control char).
 589				 * Note that we must ensure there is
 590				 * enough space for the whole ctrl pair.
 591				 *
 592				 */
 593				if (space < 2) {
 594					no_space_left = 1;
 595					break;
 596				}
 597				tty_put_char(tty, '^');
 598				tty_put_char(tty, op ^ 0100);
 599				tty->column += 2;
 600				space -= 2;
 601				cp += 2;
 602				nr -= 2;
 603			}
 604
 605			if (no_space_left)
 606				break;
 607		} else {
 608			if (O_OPOST(tty) &&
 609			    !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
 610				int retval = do_output_char(c, tty, space);
 611				if (retval < 0)
 612					break;
 613				space -= retval;
 614			} else {
 615				if (!space)
 616					break;
 617				tty_put_char(tty, c);
 618				space -= 1;
 619			}
 620			cp += 1;
 621			nr -= 1;
 622		}
 623
 624		/* When end of circular buffer reached, wrap around */
 625		if (cp >= buf_end)
 626			cp -= N_TTY_BUF_SIZE;
 627	}
 628
 629	if (nr == 0) {
 630		tty->echo_pos = 0;
 631		tty->echo_cnt = 0;
 632		tty->echo_overrun = 0;
 633	} else {
 634		int num_processed = tty->echo_cnt - nr;
 635		tty->echo_pos += num_processed;
 636		tty->echo_pos &= N_TTY_BUF_SIZE - 1;
 637		tty->echo_cnt = nr;
 638		if (num_processed > 0)
 639			tty->echo_overrun = 0;
 640	}
 641
 642	mutex_unlock(&tty->echo_lock);
 643	mutex_unlock(&tty->output_lock);
 
 
 
 
 
 
 
 
 
 
 
 644
 645	if (tty->ops->flush_chars)
 
 
 
 
 
 
 
 
 
 
 
 
 646		tty->ops->flush_chars(tty);
 647}
 648
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 649/**
 650 *	add_echo_byte	-	add a byte to the echo buffer
 651 *	@c: unicode byte to echo
 652 *	@tty: terminal device
 653 *
 654 *	Add a character or operation byte to the echo buffer.
 655 *
 656 *	Should be called under the echo lock to protect the echo buffer.
 657 */
 658
 659static void add_echo_byte(unsigned char c, struct tty_struct *tty)
 660{
 661	int	new_byte_pos;
 662
 663	if (tty->echo_cnt == N_TTY_BUF_SIZE) {
 664		/* Circular buffer is already at capacity */
 665		new_byte_pos = tty->echo_pos;
 666
 667		/*
 668		 * Since the buffer start position needs to be advanced,
 669		 * be sure to step by a whole operation byte group.
 670		 */
 671		if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
 672			if (tty->echo_buf[(tty->echo_pos + 1) &
 673					  (N_TTY_BUF_SIZE - 1)] ==
 674						ECHO_OP_ERASE_TAB) {
 675				tty->echo_pos += 3;
 676				tty->echo_cnt -= 2;
 677			} else {
 678				tty->echo_pos += 2;
 679				tty->echo_cnt -= 1;
 680			}
 681		} else {
 682			tty->echo_pos++;
 683		}
 684		tty->echo_pos &= N_TTY_BUF_SIZE - 1;
 685
 686		tty->echo_overrun = 1;
 687	} else {
 688		new_byte_pos = tty->echo_pos + tty->echo_cnt;
 689		new_byte_pos &= N_TTY_BUF_SIZE - 1;
 690		tty->echo_cnt++;
 691	}
 692
 693	tty->echo_buf[new_byte_pos] = c;
 694}
 695
 696/**
 697 *	echo_move_back_col	-	add operation to move back a column
 698 *	@tty: terminal device
 699 *
 700 *	Add an operation to the echo buffer to move back one column.
 701 *
 702 *	Locking: echo_lock to protect the echo buffer
 703 */
 704
 705static void echo_move_back_col(struct tty_struct *tty)
 706{
 707	mutex_lock(&tty->echo_lock);
 708
 709	add_echo_byte(ECHO_OP_START, tty);
 710	add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
 711
 712	mutex_unlock(&tty->echo_lock);
 713}
 714
 715/**
 716 *	echo_set_canon_col	-	add operation to set the canon column
 717 *	@tty: terminal device
 718 *
 719 *	Add an operation to the echo buffer to set the canon column
 720 *	to the current column.
 721 *
 722 *	Locking: echo_lock to protect the echo buffer
 723 */
 724
 725static void echo_set_canon_col(struct tty_struct *tty)
 726{
 727	mutex_lock(&tty->echo_lock);
 728
 729	add_echo_byte(ECHO_OP_START, tty);
 730	add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
 731
 732	mutex_unlock(&tty->echo_lock);
 733}
 734
 735/**
 736 *	echo_erase_tab	-	add operation to erase a tab
 737 *	@num_chars: number of character columns already used
 738 *	@after_tab: true if num_chars starts after a previous tab
 739 *	@tty: terminal device
 740 *
 741 *	Add an operation to the echo buffer to erase a tab.
 742 *
 743 *	Called by the eraser function, which knows how many character
 744 *	columns have been used since either a previous tab or the start
 745 *	of input.  This information will be used later, along with
 746 *	canon column (if applicable), to go back the correct number
 747 *	of columns.
 748 *
 749 *	Locking: echo_lock to protect the echo buffer
 750 */
 751
 752static void echo_erase_tab(unsigned int num_chars, int after_tab,
 753			   struct tty_struct *tty)
 754{
 755	mutex_lock(&tty->echo_lock);
 756
 757	add_echo_byte(ECHO_OP_START, tty);
 758	add_echo_byte(ECHO_OP_ERASE_TAB, tty);
 759
 760	/* We only need to know this modulo 8 (tab spacing) */
 761	num_chars &= 7;
 762
 763	/* Set the high bit as a flag if num_chars is after a previous tab */
 764	if (after_tab)
 765		num_chars |= 0x80;
 766
 767	add_echo_byte(num_chars, tty);
 768
 769	mutex_unlock(&tty->echo_lock);
 770}
 771
 772/**
 773 *	echo_char_raw	-	echo a character raw
 774 *	@c: unicode byte to echo
 775 *	@tty: terminal device
 776 *
 777 *	Echo user input back onto the screen. This must be called only when
 778 *	L_ECHO(tty) is true. Called from the driver receive_buf path.
 779 *
 780 *	This variant does not treat control characters specially.
 781 *
 782 *	Locking: echo_lock to protect the echo buffer
 783 */
 784
 785static void echo_char_raw(unsigned char c, struct tty_struct *tty)
 786{
 787	mutex_lock(&tty->echo_lock);
 788
 789	if (c == ECHO_OP_START) {
 790		add_echo_byte(ECHO_OP_START, tty);
 791		add_echo_byte(ECHO_OP_START, tty);
 792	} else {
 793		add_echo_byte(c, tty);
 794	}
 795
 796	mutex_unlock(&tty->echo_lock);
 797}
 798
 799/**
 800 *	echo_char	-	echo a character
 801 *	@c: unicode byte to echo
 802 *	@tty: terminal device
 803 *
 804 *	Echo user input back onto the screen. This must be called only when
 805 *	L_ECHO(tty) is true. Called from the driver receive_buf path.
 806 *
 807 *	This variant tags control characters to be echoed as "^X"
 808 *	(where X is the letter representing the control char).
 809 *
 810 *	Locking: echo_lock to protect the echo buffer
 811 */
 812
 813static void echo_char(unsigned char c, struct tty_struct *tty)
 814{
 815	mutex_lock(&tty->echo_lock);
 816
 817	if (c == ECHO_OP_START) {
 818		add_echo_byte(ECHO_OP_START, tty);
 819		add_echo_byte(ECHO_OP_START, tty);
 820	} else {
 821		if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
 822			add_echo_byte(ECHO_OP_START, tty);
 823		add_echo_byte(c, tty);
 824	}
 825
 826	mutex_unlock(&tty->echo_lock);
 827}
 828
 829/**
 830 *	finish_erasing		-	complete erase
 831 *	@tty: tty doing the erase
 832 */
 833
 834static inline void finish_erasing(struct tty_struct *tty)
 835{
 836	if (tty->erasing) {
 837		echo_char_raw('/', tty);
 838		tty->erasing = 0;
 839	}
 840}
 841
 842/**
 843 *	eraser		-	handle erase function
 844 *	@c: character input
 845 *	@tty: terminal device
 846 *
 847 *	Perform erase and necessary output when an erase character is
 848 *	present in the stream from the driver layer. Handles the complexities
 849 *	of UTF-8 multibyte symbols.
 850 *
 851 *	Locking: read_lock for tty buffers
 
 852 */
 853
 854static void eraser(unsigned char c, struct tty_struct *tty)
 855{
 
 856	enum { ERASE, WERASE, KILL } kill_type;
 857	int head, seen_alnums, cnt;
 858	unsigned long flags;
 
 859
 860	/* FIXME: locking needed ? */
 861	if (tty->read_head == tty->canon_head) {
 862		/* process_output('\a', tty); */ /* what do you think? */
 863		return;
 864	}
 865	if (c == ERASE_CHAR(tty))
 866		kill_type = ERASE;
 867	else if (c == WERASE_CHAR(tty))
 868		kill_type = WERASE;
 869	else {
 870		if (!L_ECHO(tty)) {
 871			spin_lock_irqsave(&tty->read_lock, flags);
 872			tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 873					  (N_TTY_BUF_SIZE - 1));
 874			tty->read_head = tty->canon_head;
 875			spin_unlock_irqrestore(&tty->read_lock, flags);
 876			return;
 877		}
 878		if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
 879			spin_lock_irqsave(&tty->read_lock, flags);
 880			tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 881					  (N_TTY_BUF_SIZE - 1));
 882			tty->read_head = tty->canon_head;
 883			spin_unlock_irqrestore(&tty->read_lock, flags);
 884			finish_erasing(tty);
 885			echo_char(KILL_CHAR(tty), tty);
 886			/* Add a newline if ECHOK is on and ECHOKE is off. */
 887			if (L_ECHOK(tty))
 888				echo_char_raw('\n', tty);
 889			return;
 890		}
 891		kill_type = KILL;
 892	}
 893
 894	seen_alnums = 0;
 895	/* FIXME: Locking ?? */
 896	while (tty->read_head != tty->canon_head) {
 897		head = tty->read_head;
 898
 899		/* erase a single possibly multibyte character */
 900		do {
 901			head = (head - 1) & (N_TTY_BUF_SIZE-1);
 902			c = tty->read_buf[head];
 903		} while (is_continuation(c, tty) && head != tty->canon_head);
 904
 905		/* do not partially erase */
 906		if (is_continuation(c, tty))
 907			break;
 908
 909		if (kill_type == WERASE) {
 910			/* Equivalent to BSD's ALTWERASE. */
 911			if (isalnum(c) || c == '_')
 912				seen_alnums++;
 913			else if (seen_alnums)
 914				break;
 915		}
 916		cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
 917		spin_lock_irqsave(&tty->read_lock, flags);
 918		tty->read_head = head;
 919		tty->read_cnt -= cnt;
 920		spin_unlock_irqrestore(&tty->read_lock, flags);
 921		if (L_ECHO(tty)) {
 922			if (L_ECHOPRT(tty)) {
 923				if (!tty->erasing) {
 924					echo_char_raw('\\', tty);
 925					tty->erasing = 1;
 926				}
 927				/* if cnt > 1, output a multi-byte character */
 928				echo_char(c, tty);
 929				while (--cnt > 0) {
 930					head = (head+1) & (N_TTY_BUF_SIZE-1);
 931					echo_char_raw(tty->read_buf[head], tty);
 932					echo_move_back_col(tty);
 933				}
 934			} else if (kill_type == ERASE && !L_ECHOE(tty)) {
 935				echo_char(ERASE_CHAR(tty), tty);
 936			} else if (c == '\t') {
 937				unsigned int num_chars = 0;
 938				int after_tab = 0;
 939				unsigned long tail = tty->read_head;
 940
 941				/*
 942				 * Count the columns used for characters
 943				 * since the start of input or after a
 944				 * previous tab.
 945				 * This info is used to go back the correct
 946				 * number of columns.
 947				 */
 948				while (tail != tty->canon_head) {
 949					tail = (tail-1) & (N_TTY_BUF_SIZE-1);
 950					c = tty->read_buf[tail];
 951					if (c == '\t') {
 952						after_tab = 1;
 953						break;
 954					} else if (iscntrl(c)) {
 955						if (L_ECHOCTL(tty))
 956							num_chars += 2;
 957					} else if (!is_continuation(c, tty)) {
 958						num_chars++;
 959					}
 960				}
 961				echo_erase_tab(num_chars, after_tab, tty);
 962			} else {
 963				if (iscntrl(c) && L_ECHOCTL(tty)) {
 964					echo_char_raw('\b', tty);
 965					echo_char_raw(' ', tty);
 966					echo_char_raw('\b', tty);
 967				}
 968				if (!iscntrl(c) || L_ECHOCTL(tty)) {
 969					echo_char_raw('\b', tty);
 970					echo_char_raw(' ', tty);
 971					echo_char_raw('\b', tty);
 972				}
 973			}
 974		}
 975		if (kill_type == ERASE)
 976			break;
 977	}
 978	if (tty->read_head == tty->canon_head && L_ECHO(tty))
 979		finish_erasing(tty);
 980}
 981
 982/**
 983 *	isig		-	handle the ISIG optio
 984 *	@sig: signal
 985 *	@tty: terminal
 986 *	@flush: force flush
 987 *
 988 *	Called when a signal is being sent due to terminal input. This
 989 *	may caus terminal flushing to take place according to the termios
 990 *	settings and character used. Called from the driver receive_buf
 991 *	path so serialized.
 
 
 992 *
 993 *	Locking: ctrl_lock, read_lock (both via flush buffer)
 994 */
 995
 996static inline void isig(int sig, struct tty_struct *tty, int flush)
 
 
 
 
 
 
 
 
 
 997{
 998	if (tty->pgrp)
 999		kill_pgrp(tty->pgrp, sig, 1);
1000	if (flush || !L_NOFLSH(tty)) {
1001		n_tty_flush_buffer(tty);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1002		tty_driver_flush_buffer(tty);
 
 
 
 
 
 
 
 
 
 
1003	}
1004}
1005
1006/**
1007 *	n_tty_receive_break	-	handle break
1008 *	@tty: terminal
1009 *
1010 *	An RS232 break event has been hit in the incoming bitstream. This
1011 *	can cause a variety of events depending upon the termios settings.
1012 *
1013 *	Called from the receive_buf path so single threaded.
 
 
 
1014 */
1015
1016static inline void n_tty_receive_break(struct tty_struct *tty)
1017{
 
 
1018	if (I_IGNBRK(tty))
1019		return;
1020	if (I_BRKINT(tty)) {
1021		isig(SIGINT, tty, 1);
1022		return;
1023	}
1024	if (I_PARMRK(tty)) {
1025		put_tty_queue('\377', tty);
1026		put_tty_queue('\0', tty);
1027	}
1028	put_tty_queue('\0', tty);
1029	wake_up_interruptible(&tty->read_wait);
1030}
1031
1032/**
1033 *	n_tty_receive_overrun	-	handle overrun reporting
1034 *	@tty: terminal
1035 *
1036 *	Data arrived faster than we could process it. While the tty
1037 *	driver has flagged this the bits that were missed are gone
1038 *	forever.
1039 *
1040 *	Called from the receive_buf path so single threaded. Does not
1041 *	need locking as num_overrun and overrun_time are function
1042 *	private.
1043 */
1044
1045static inline void n_tty_receive_overrun(struct tty_struct *tty)
1046{
1047	char buf[64];
1048
1049	tty->num_overrun++;
1050	if (time_before(tty->overrun_time, jiffies - HZ) ||
1051			time_after(tty->overrun_time, jiffies)) {
1052		printk(KERN_WARNING "%s: %d input overrun(s)\n",
1053			tty_name(tty, buf),
1054			tty->num_overrun);
1055		tty->overrun_time = jiffies;
1056		tty->num_overrun = 0;
1057	}
1058}
1059
1060/**
1061 *	n_tty_receive_parity_error	-	error notifier
1062 *	@tty: terminal device
1063 *	@c: character
1064 *
1065 *	Process a parity error and queue the right data to indicate
1066 *	the error case if necessary. Locking as per n_tty_receive_buf.
 
 
 
1067 */
1068static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1069					      unsigned char c)
1070{
1071	if (I_IGNPAR(tty))
1072		return;
1073	if (I_PARMRK(tty)) {
1074		put_tty_queue('\377', tty);
1075		put_tty_queue('\0', tty);
1076		put_tty_queue(c, tty);
1077	} else	if (I_INPCK(tty))
1078		put_tty_queue('\0', tty);
1079	else
1080		put_tty_queue(c, tty);
1081	wake_up_interruptible(&tty->read_wait);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1082}
1083
1084/**
1085 *	n_tty_receive_char	-	perform processing
1086 *	@tty: terminal device
1087 *	@c: character
1088 *
1089 *	Process an individual character of input received from the driver.
1090 *	This is serialized with respect to itself by the rules for the
1091 *	driver above.
 
 
 
 
 
 
1092 */
1093
1094static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 
1095{
1096	unsigned long flags;
1097	int parmrk;
1098
1099	if (tty->raw) {
1100		put_tty_queue(c, tty);
1101		return;
1102	}
1103
1104	if (I_ISTRIP(tty))
1105		c &= 0x7f;
1106	if (I_IUCLC(tty) && L_IEXTEN(tty))
1107		c = tolower(c);
1108
1109	if (L_EXTPROC(tty)) {
1110		put_tty_queue(c, tty);
1111		return;
1112	}
1113
1114	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1115	    I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1116	    c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1117		start_tty(tty);
1118		process_echoes(tty);
1119	}
1120
1121	if (tty->closing) {
1122		if (I_IXON(tty)) {
1123			if (c == START_CHAR(tty)) {
1124				start_tty(tty);
1125				process_echoes(tty);
1126			} else if (c == STOP_CHAR(tty))
1127				stop_tty(tty);
1128		}
1129		return;
1130	}
1131
1132	/*
1133	 * If the previous character was LNEXT, or we know that this
1134	 * character is not one of the characters that we'll have to
1135	 * handle specially, do shortcut processing to speed things
1136	 * up.
1137	 */
1138	if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1139		tty->lnext = 0;
1140		parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1141		if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1142			/* beep if no space */
1143			if (L_ECHO(tty))
1144				process_output('\a', tty);
1145			return;
1146		}
1147		if (L_ECHO(tty)) {
1148			finish_erasing(tty);
1149			/* Record the column of first canon char. */
1150			if (tty->canon_head == tty->read_head)
1151				echo_set_canon_col(tty);
1152			echo_char(c, tty);
1153			process_echoes(tty);
1154		}
1155		if (parmrk)
1156			put_tty_queue(c, tty);
1157		put_tty_queue(c, tty);
1158		return;
1159	}
1160
1161	if (I_IXON(tty)) {
1162		if (c == START_CHAR(tty)) {
1163			start_tty(tty);
1164			process_echoes(tty);
1165			return;
1166		}
1167		if (c == STOP_CHAR(tty)) {
1168			stop_tty(tty);
1169			return;
1170		}
1171	}
1172
1173	if (L_ISIG(tty)) {
1174		int signal;
1175		signal = SIGINT;
1176		if (c == INTR_CHAR(tty))
1177			goto send_signal;
1178		signal = SIGQUIT;
1179		if (c == QUIT_CHAR(tty))
1180			goto send_signal;
1181		signal = SIGTSTP;
1182		if (c == SUSP_CHAR(tty)) {
1183send_signal:
1184			/*
1185			 * Note that we do not use isig() here because we want
1186			 * the order to be:
1187			 * 1) flush, 2) echo, 3) signal
1188			 */
1189			if (!L_NOFLSH(tty)) {
1190				n_tty_flush_buffer(tty);
1191				tty_driver_flush_buffer(tty);
1192			}
1193			if (I_IXON(tty))
1194				start_tty(tty);
1195			if (L_ECHO(tty)) {
1196				echo_char(c, tty);
1197				process_echoes(tty);
1198			}
1199			if (tty->pgrp)
1200				kill_pgrp(tty->pgrp, signal, 1);
1201			return;
1202		}
1203	}
1204
 
 
 
 
 
1205	if (c == '\r') {
1206		if (I_IGNCR(tty))
1207			return;
1208		if (I_ICRNL(tty))
1209			c = '\n';
1210	} else if (c == '\n' && I_INLCR(tty))
1211		c = '\r';
1212
1213	if (tty->icanon) {
1214		if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1215		    (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1216			eraser(c, tty);
1217			process_echoes(tty);
1218			return;
1219		}
1220		if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1221			tty->lnext = 1;
1222			if (L_ECHO(tty)) {
1223				finish_erasing(tty);
1224				if (L_ECHOCTL(tty)) {
1225					echo_char_raw('^', tty);
1226					echo_char_raw('\b', tty);
1227					process_echoes(tty);
1228				}
1229			}
1230			return;
1231		}
1232		if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1233		    L_IEXTEN(tty)) {
1234			unsigned long tail = tty->canon_head;
1235
1236			finish_erasing(tty);
1237			echo_char(c, tty);
1238			echo_char_raw('\n', tty);
1239			while (tail != tty->read_head) {
1240				echo_char(tty->read_buf[tail], tty);
1241				tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1242			}
1243			process_echoes(tty);
1244			return;
1245		}
1246		if (c == '\n') {
1247			if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1248				if (L_ECHO(tty))
1249					process_output('\a', tty);
1250				return;
1251			}
1252			if (L_ECHO(tty) || L_ECHONL(tty)) {
1253				echo_char_raw('\n', tty);
1254				process_echoes(tty);
1255			}
1256			goto handle_newline;
1257		}
1258		if (c == EOF_CHAR(tty)) {
1259			if (tty->read_cnt >= N_TTY_BUF_SIZE)
1260				return;
1261			if (tty->canon_head != tty->read_head)
1262				set_bit(TTY_PUSH, &tty->flags);
1263			c = __DISABLED_CHAR;
1264			goto handle_newline;
1265		}
1266		if ((c == EOL_CHAR(tty)) ||
1267		    (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1268			parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1269				 ? 1 : 0;
1270			if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1271				if (L_ECHO(tty))
1272					process_output('\a', tty);
1273				return;
1274			}
1275			/*
1276			 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1277			 */
1278			if (L_ECHO(tty)) {
1279				/* Record the column of first canon char. */
1280				if (tty->canon_head == tty->read_head)
1281					echo_set_canon_col(tty);
1282				echo_char(c, tty);
1283				process_echoes(tty);
1284			}
1285			/*
1286			 * XXX does PARMRK doubling happen for
1287			 * EOL_CHAR and EOL2_CHAR?
1288			 */
1289			if (parmrk)
1290				put_tty_queue(c, tty);
1291
1292handle_newline:
1293			spin_lock_irqsave(&tty->read_lock, flags);
1294			set_bit(tty->read_head, tty->read_flags);
1295			put_tty_queue_nolock(c, tty);
1296			tty->canon_head = tty->read_head;
1297			tty->canon_data++;
1298			spin_unlock_irqrestore(&tty->read_lock, flags);
1299			kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1300			if (waitqueue_active(&tty->read_wait))
1301				wake_up_interruptible(&tty->read_wait);
1302			return;
1303		}
1304	}
1305
1306	parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1307	if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1308		/* beep if no space */
1309		if (L_ECHO(tty))
1310			process_output('\a', tty);
1311		return;
1312	}
1313	if (L_ECHO(tty)) {
1314		finish_erasing(tty);
1315		if (c == '\n')
1316			echo_char_raw('\n', tty);
1317		else {
1318			/* Record the column of first canon char. */
1319			if (tty->canon_head == tty->read_head)
1320				echo_set_canon_col(tty);
1321			echo_char(c, tty);
1322		}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1323		process_echoes(tty);
1324	}
 
 
 
 
 
 
 
 
 
 
 
 
 
1325
1326	if (parmrk)
1327		put_tty_queue(c, tty);
 
 
 
 
 
 
 
1328
1329	put_tty_queue(c, tty);
 
 
 
 
 
 
 
 
 
 
 
 
1330}
1331
 
 
 
 
 
 
1332
1333/**
1334 *	n_tty_write_wakeup	-	asynchronous I/O notifier
1335 *	@tty: tty device
1336 *
1337 *	Required for the ptys, serial driver etc. since processes
1338 *	that attach themselves to the master and rely on ASYNC
1339 *	IO must be woken up
1340 */
 
 
 
 
1341
1342static void n_tty_write_wakeup(struct tty_struct *tty)
 
1343{
1344	if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1345		kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
 
 
 
 
 
 
 
 
 
 
 
 
 
1346}
1347
1348/**
1349 *	n_tty_receive_buf	-	data receive
1350 *	@tty: terminal device
1351 *	@cp: buffer
1352 *	@fp: flag buffer
1353 *	@count: characters
1354 *
1355 *	Called by the terminal driver when a block of characters has
1356 *	been received. This function must be called from soft contexts
1357 *	not from interrupt context. The driver is responsible for making
1358 *	calls one at a time and in order (or using flush_to_ldisc)
1359 */
1360
1361static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1362			      char *fp, int count)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1363{
1364	const unsigned char *p;
1365	char *f, flags = TTY_NORMAL;
1366	int	i;
1367	char	buf[64];
1368	unsigned long cpuflags;
1369
1370	if (!tty->read_buf)
1371		return;
 
 
 
 
 
1372
1373	if (tty->real_raw) {
1374		spin_lock_irqsave(&tty->read_lock, cpuflags);
1375		i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1376			N_TTY_BUF_SIZE - tty->read_head);
1377		i = min(count, i);
1378		memcpy(tty->read_buf + tty->read_head, cp, i);
1379		tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1380		tty->read_cnt += i;
1381		cp += i;
1382		count -= i;
1383
1384		i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1385			N_TTY_BUF_SIZE - tty->read_head);
1386		i = min(count, i);
1387		memcpy(tty->read_buf + tty->read_head, cp, i);
1388		tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1389		tty->read_cnt += i;
1390		spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1391	} else {
1392		for (i = count, p = cp, f = fp; i; i--, p++) {
1393			if (f)
1394				flags = *f++;
1395			switch (flags) {
1396			case TTY_NORMAL:
1397				n_tty_receive_char(tty, *p);
1398				break;
1399			case TTY_BREAK:
1400				n_tty_receive_break(tty);
1401				break;
1402			case TTY_PARITY:
1403			case TTY_FRAME:
1404				n_tty_receive_parity_error(tty, *p);
1405				break;
1406			case TTY_OVERRUN:
1407				n_tty_receive_overrun(tty);
1408				break;
1409			default:
1410				printk(KERN_ERR "%s: unknown flag %d\n",
1411				       tty_name(tty, buf), flags);
1412				break;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1413			}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1414		}
 
 
 
 
 
 
 
1415		if (tty->ops->flush_chars)
1416			tty->ops->flush_chars(tty);
1417	}
1418
1419	n_tty_set_room(tty);
 
1420
1421	if ((!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) ||
1422		L_EXTPROC(tty)) {
 
 
1423		kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1424		if (waitqueue_active(&tty->read_wait))
1425			wake_up_interruptible(&tty->read_wait);
1426	}
 
1427
1428	/*
1429	 * Check the remaining room for the input canonicalization
1430	 * mode.  We don't want to throttle the driver if we're in
1431	 * canonical mode and don't have a newline yet!
1432	 */
1433	if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1434		tty_throttle(tty);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1435}
1436
1437int is_ignored(int sig)
 
1438{
1439	return (sigismember(&current->blocked, sig) ||
1440		current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1441}
1442
1443/**
1444 *	n_tty_set_termios	-	termios data changed
1445 *	@tty: terminal
1446 *	@old: previous data
1447 *
1448 *	Called by the tty layer when the user changes termios flags so
1449 *	that the line discipline can plan ahead. This function cannot sleep
1450 *	and is protected from re-entry by the tty layer. The user is
1451 *	guaranteed that this function will not be re-entered or in progress
1452 *	when the ldisc is closed.
1453 *
1454 *	Locking: Caller holds tty->termios_mutex
1455 */
1456
1457static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1458{
1459	int canon_change = 1;
1460	BUG_ON(!tty);
1461
1462	if (old)
1463		canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1464	if (canon_change) {
1465		memset(&tty->read_flags, 0, sizeof tty->read_flags);
1466		tty->canon_head = tty->read_tail;
1467		tty->canon_data = 0;
1468		tty->erasing = 0;
1469	}
1470
1471	if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1472		wake_up_interruptible(&tty->read_wait);
1473
1474	tty->icanon = (L_ICANON(tty) != 0);
1475	if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1476		tty->raw = 1;
1477		tty->real_raw = 1;
1478		n_tty_set_room(tty);
1479		return;
1480	}
 
 
 
1481	if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1482	    I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1483	    I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1484	    I_PARMRK(tty)) {
1485		memset(tty->process_char_map, 0, 256/8);
1486
1487		if (I_IGNCR(tty) || I_ICRNL(tty))
1488			set_bit('\r', tty->process_char_map);
1489		if (I_INLCR(tty))
1490			set_bit('\n', tty->process_char_map);
1491
1492		if (L_ICANON(tty)) {
1493			set_bit(ERASE_CHAR(tty), tty->process_char_map);
1494			set_bit(KILL_CHAR(tty), tty->process_char_map);
1495			set_bit(EOF_CHAR(tty), tty->process_char_map);
1496			set_bit('\n', tty->process_char_map);
1497			set_bit(EOL_CHAR(tty), tty->process_char_map);
1498			if (L_IEXTEN(tty)) {
1499				set_bit(WERASE_CHAR(tty),
1500					tty->process_char_map);
1501				set_bit(LNEXT_CHAR(tty),
1502					tty->process_char_map);
1503				set_bit(EOL2_CHAR(tty),
1504					tty->process_char_map);
1505				if (L_ECHO(tty))
1506					set_bit(REPRINT_CHAR(tty),
1507						tty->process_char_map);
1508			}
1509		}
1510		if (I_IXON(tty)) {
1511			set_bit(START_CHAR(tty), tty->process_char_map);
1512			set_bit(STOP_CHAR(tty), tty->process_char_map);
1513		}
1514		if (L_ISIG(tty)) {
1515			set_bit(INTR_CHAR(tty), tty->process_char_map);
1516			set_bit(QUIT_CHAR(tty), tty->process_char_map);
1517			set_bit(SUSP_CHAR(tty), tty->process_char_map);
1518		}
1519		clear_bit(__DISABLED_CHAR, tty->process_char_map);
1520		tty->raw = 0;
1521		tty->real_raw = 0;
1522	} else {
1523		tty->raw = 1;
1524		if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1525		    (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1526		    (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1527			tty->real_raw = 1;
1528		else
1529			tty->real_raw = 0;
 
 
 
 
 
 
 
 
1530	}
1531	n_tty_set_room(tty);
1532	/* The termios change make the tty ready for I/O */
1533	wake_up_interruptible(&tty->write_wait);
1534	wake_up_interruptible(&tty->read_wait);
1535}
1536
1537/**
1538 *	n_tty_close		-	close the ldisc for this tty
1539 *	@tty: device
1540 *
1541 *	Called from the terminal layer when this line discipline is
1542 *	being shut down, either because of a close or becsuse of a
1543 *	discipline change. The function will not be called while other
1544 *	ldisc methods are in progress.
1545 */
1546
1547static void n_tty_close(struct tty_struct *tty)
1548{
1549	n_tty_flush_buffer(tty);
1550	if (tty->read_buf) {
1551		kfree(tty->read_buf);
1552		tty->read_buf = NULL;
1553	}
1554	if (tty->echo_buf) {
1555		kfree(tty->echo_buf);
1556		tty->echo_buf = NULL;
1557	}
1558}
1559
1560/**
1561 *	n_tty_open		-	open an ldisc
1562 *	@tty: terminal to open
1563 *
1564 *	Called when this line discipline is being attached to the
1565 *	terminal device. Can sleep. Called serialized so that no
1566 *	other events will occur in parallel. No further open will occur
1567 *	until a close.
1568 */
1569
1570static int n_tty_open(struct tty_struct *tty)
1571{
1572	if (!tty)
1573		return -EINVAL;
1574
1575	/* These are ugly. Currently a malloc failure here can panic */
1576	if (!tty->read_buf) {
1577		tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1578		if (!tty->read_buf)
1579			return -ENOMEM;
1580	}
1581	if (!tty->echo_buf) {
1582		tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1583
1584		if (!tty->echo_buf)
1585			return -ENOMEM;
1586	}
1587	reset_buffer_flags(tty);
1588	tty_unthrottle(tty);
1589	tty->column = 0;
1590	n_tty_set_termios(tty, NULL);
1591	tty->minimum_to_wake = 1;
 
 
 
 
 
 
 
 
1592	tty->closing = 0;
 
 
 
 
 
1593	return 0;
 
 
1594}
1595
1596static inline int input_available_p(struct tty_struct *tty, int amt)
1597{
1598	tty_flush_to_ldisc(tty);
1599	if (tty->icanon && !L_EXTPROC(tty)) {
1600		if (tty->canon_data)
1601			return 1;
1602	} else if (tty->read_cnt >= (amt ? amt : 1))
1603		return 1;
1604
1605	return 0;
 
 
 
1606}
1607
1608/**
1609 *	copy_from_read_buf	-	copy read data directly
1610 *	@tty: terminal device
1611 *	@b: user data
1612 *	@nr: size of data
1613 *
1614 *	Helper function to speed up n_tty_read.  It is only called when
1615 *	ICANON is off; it copies characters straight from the tty queue to
1616 *	user space directly.  It can be profitably called twice; once to
1617 *	drain the space from the tail pointer to the (physical) end of the
1618 *	buffer, and once to drain the space from the (physical) beginning of
1619 *	the buffer to head pointer.
1620 *
1621 *	Called under the tty->atomic_read_lock sem
1622 *
 
 
 
1623 */
1624
1625static int copy_from_read_buf(struct tty_struct *tty,
1626				      unsigned char __user **b,
1627				      size_t *nr)
1628
1629{
 
1630	int retval;
1631	size_t n;
1632	unsigned long flags;
1633	bool is_eof;
 
 
1634
1635	retval = 0;
1636	spin_lock_irqsave(&tty->read_lock, flags);
1637	n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1638	n = min(*nr, n);
1639	spin_unlock_irqrestore(&tty->read_lock, flags);
1640	if (n) {
1641		retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
 
1642		n -= retval;
1643		is_eof = n == 1 &&
1644			tty->read_buf[tty->read_tail] == EOF_CHAR(tty);
1645		tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1646		spin_lock_irqsave(&tty->read_lock, flags);
1647		tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1648		tty->read_cnt -= n;
1649		/* Turn single EOF into zero-length read */
1650		if (L_EXTPROC(tty) && tty->icanon && is_eof && !tty->read_cnt)
 
1651			n = 0;
1652		spin_unlock_irqrestore(&tty->read_lock, flags);
1653		*b += n;
1654		*nr -= n;
1655	}
1656	return retval;
1657}
1658
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1659extern ssize_t redirected_tty_write(struct file *, const char __user *,
1660							size_t, loff_t *);
1661
1662/**
1663 *	job_control		-	check job control
1664 *	@tty: tty
1665 *	@file: file handle
1666 *
1667 *	Perform job control management checks on this file/tty descriptor
1668 *	and if appropriate send any needed signals and return a negative
1669 *	error code if action should be taken.
1670 *
1671 *	FIXME:
1672 *	Locking: None - redirected write test is safe, testing
1673 *	current->signal should possibly lock current->sighand
1674 *	pgrp locking ?
1675 */
1676
1677static int job_control(struct tty_struct *tty, struct file *file)
1678{
1679	/* Job control check -- must be done at start and after
1680	   every sleep (POSIX.1 7.1.1.4). */
1681	/* NOTE: not yet done after every sleep pending a thorough
1682	   check of the logic of this change. -- jlc */
1683	/* don't stop on /dev/console */
1684	if (file->f_op->write != redirected_tty_write &&
1685	    current->signal->tty == tty) {
1686		if (!tty->pgrp)
1687			printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1688		else if (task_pgrp(current) != tty->pgrp) {
1689			if (is_ignored(SIGTTIN) ||
1690			    is_current_pgrp_orphaned())
1691				return -EIO;
1692			kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1693			set_thread_flag(TIF_SIGPENDING);
1694			return -ERESTARTSYS;
1695		}
1696	}
1697	return 0;
1698}
1699
1700
1701/**
1702 *	n_tty_read		-	read function for tty
1703 *	@tty: tty device
1704 *	@file: file object
1705 *	@buf: userspace buffer pointer
1706 *	@nr: size of I/O
1707 *
1708 *	Perform reads for the line discipline. We are guaranteed that the
1709 *	line discipline will not be closed under us but we may get multiple
1710 *	parallel readers and must handle this ourselves. We may also get
1711 *	a hangup. Always called in user context, may sleep.
1712 *
1713 *	This code must be sure never to sleep through a hangup.
 
 
 
 
1714 */
1715
1716static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1717			 unsigned char __user *buf, size_t nr)
1718{
 
1719	unsigned char __user *b = buf;
1720	DECLARE_WAITQUEUE(wait, current);
1721	int c;
1722	int minimum, time;
1723	ssize_t retval = 0;
1724	ssize_t size;
1725	long timeout;
1726	unsigned long flags;
1727	int packet;
1728
1729do_it_again:
1730
1731	if (WARN_ON(!tty->read_buf))
1732		return -EAGAIN;
1733
1734	c = job_control(tty, file);
1735	if (c < 0)
1736		return c;
1737
1738	minimum = time = 0;
1739	timeout = MAX_SCHEDULE_TIMEOUT;
1740	if (!tty->icanon) {
1741		time = (HZ / 10) * TIME_CHAR(tty);
1742		minimum = MIN_CHAR(tty);
1743		if (minimum) {
1744			if (time)
1745				tty->minimum_to_wake = 1;
1746			else if (!waitqueue_active(&tty->read_wait) ||
1747				 (tty->minimum_to_wake > minimum))
1748				tty->minimum_to_wake = minimum;
1749		} else {
1750			timeout = 0;
1751			if (time) {
1752				timeout = time;
1753				time = 0;
1754			}
1755			tty->minimum_to_wake = minimum = 1;
1756		}
1757	}
1758
1759	/*
1760	 *	Internal serialization of reads.
1761	 */
1762	if (file->f_flags & O_NONBLOCK) {
1763		if (!mutex_trylock(&tty->atomic_read_lock))
1764			return -EAGAIN;
1765	} else {
1766		if (mutex_lock_interruptible(&tty->atomic_read_lock))
1767			return -ERESTARTSYS;
1768	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1769	packet = tty->packet;
 
1770
1771	add_wait_queue(&tty->read_wait, &wait);
1772	while (nr) {
1773		/* First test for status change. */
1774		if (packet && tty->link->ctrl_status) {
1775			unsigned char cs;
1776			if (b != buf)
1777				break;
1778			spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1779			cs = tty->link->ctrl_status;
1780			tty->link->ctrl_status = 0;
1781			spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1782			if (tty_put_user(tty, cs, b++)) {
1783				retval = -EFAULT;
1784				b--;
1785				break;
1786			}
 
1787			nr--;
1788			break;
1789		}
1790		/* This statement must be first before checking for input
1791		   so that any interrupt will set the state back to
1792		   TASK_RUNNING. */
1793		set_current_state(TASK_INTERRUPTIBLE);
1794
1795		if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1796		    ((minimum - (b - buf)) >= 1))
1797			tty->minimum_to_wake = (minimum - (b - buf));
1798
1799		if (!input_available_p(tty, 0)) {
1800			if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1801				retval = -EIO;
1802				break;
1803			}
1804			if (tty_hung_up_p(file))
1805				break;
1806			if (!timeout)
1807				break;
1808			if (file->f_flags & O_NONBLOCK) {
1809				retval = -EAGAIN;
1810				break;
1811			}
1812			if (signal_pending(current)) {
1813				retval = -ERESTARTSYS;
1814				break;
1815			}
1816			/* FIXME: does n_tty_set_room need locking ? */
1817			n_tty_set_room(tty);
1818			timeout = schedule_timeout(timeout);
1819			BUG_ON(!tty->read_buf);
1820			continue;
1821		}
1822		__set_current_state(TASK_RUNNING);
1823
1824		/* Deal with packet mode. */
1825		if (packet && b == buf) {
1826			if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1827				retval = -EFAULT;
1828				b--;
1829				break;
1830			}
1831			nr--;
1832		}
1833
1834		if (tty->icanon && !L_EXTPROC(tty)) {
1835			/* N.B. avoid overrun if nr == 0 */
1836			while (nr && tty->read_cnt) {
1837				int eol;
1838
1839				eol = test_and_clear_bit(tty->read_tail,
1840						tty->read_flags);
1841				c = tty->read_buf[tty->read_tail];
1842				spin_lock_irqsave(&tty->read_lock, flags);
1843				tty->read_tail = ((tty->read_tail+1) &
1844						  (N_TTY_BUF_SIZE-1));
1845				tty->read_cnt--;
1846				if (eol) {
1847					/* this test should be redundant:
1848					 * we shouldn't be reading data if
1849					 * canon_data is 0
1850					 */
1851					if (--tty->canon_data < 0)
1852						tty->canon_data = 0;
1853				}
1854				spin_unlock_irqrestore(&tty->read_lock, flags);
1855
1856				if (!eol || (c != __DISABLED_CHAR)) {
1857					if (tty_put_user(tty, c, b++)) {
1858						retval = -EFAULT;
1859						b--;
1860						break;
1861					}
1862					nr--;
 
 
 
 
1863				}
1864				if (eol) {
1865					tty_audit_push(tty);
1866					break;
1867				}
 
 
 
 
 
 
 
1868			}
 
 
 
 
1869			if (retval)
1870				break;
1871		} else {
1872			int uncopied;
1873			/* The copy function takes the read lock and handles
1874			   locking internally for this case */
 
 
 
 
 
 
 
 
 
1875			uncopied = copy_from_read_buf(tty, &b, &nr);
1876			uncopied += copy_from_read_buf(tty, &b, &nr);
1877			if (uncopied) {
1878				retval = -EFAULT;
1879				break;
1880			}
1881		}
1882
1883		/* If there is enough space in the read buffer now, let the
1884		 * low-level driver know. We use n_tty_chars_in_buffer() to
1885		 * check the buffer, as it now knows about canonical mode.
1886		 * Otherwise, if the driver is throttled and the line is
1887		 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1888		 * we won't get any more characters.
1889		 */
1890		if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1891			n_tty_set_room(tty);
1892			check_unthrottle(tty);
1893		}
1894
1895		if (b - buf >= minimum)
1896			break;
1897		if (time)
1898			timeout = time;
1899	}
1900	mutex_unlock(&tty->atomic_read_lock);
1901	remove_wait_queue(&tty->read_wait, &wait);
 
1902
1903	if (!waitqueue_active(&tty->read_wait))
1904		tty->minimum_to_wake = minimum;
1905
1906	__set_current_state(TASK_RUNNING);
1907	size = b - buf;
1908	if (size) {
1909		retval = size;
1910		if (nr)
1911			clear_bit(TTY_PUSH, &tty->flags);
1912	} else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1913		goto do_it_again;
1914
1915	n_tty_set_room(tty);
1916	return retval;
1917}
1918
1919/**
1920 *	n_tty_write		-	write function for tty
1921 *	@tty: tty device
1922 *	@file: file object
1923 *	@buf: userspace buffer pointer
1924 *	@nr: size of I/O
1925 *
1926 *	Write function of the terminal device.  This is serialized with
1927 *	respect to other write callers but not to termios changes, reads
1928 *	and other such events.  Since the receive code will echo characters,
1929 *	thus calling driver write methods, the output_lock is used in
1930 *	the output processing functions called here as well as in the
1931 *	echo processing function to protect the column state and space
1932 *	left in the buffer.
1933 *
1934 *	This code must be sure never to sleep through a hangup.
1935 *
1936 *	Locking: output_lock to protect column state and space left
1937 *		 (note that the process_output*() functions take this
1938 *		  lock themselves)
1939 */
1940
1941static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1942			   const unsigned char *buf, size_t nr)
1943{
1944	const unsigned char *b = buf;
1945	DECLARE_WAITQUEUE(wait, current);
1946	int c;
1947	ssize_t retval = 0;
1948
1949	/* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1950	if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1951		retval = tty_check_change(tty);
1952		if (retval)
1953			return retval;
1954	}
1955
 
 
1956	/* Write out any echoed characters that are still pending */
1957	process_echoes(tty);
1958
1959	add_wait_queue(&tty->write_wait, &wait);
1960	while (1) {
1961		set_current_state(TASK_INTERRUPTIBLE);
1962		if (signal_pending(current)) {
1963			retval = -ERESTARTSYS;
1964			break;
1965		}
1966		if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1967			retval = -EIO;
1968			break;
1969		}
1970		if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1971			while (nr > 0) {
1972				ssize_t num = process_output_block(tty, b, nr);
1973				if (num < 0) {
1974					if (num == -EAGAIN)
1975						break;
1976					retval = num;
1977					goto break_out;
1978				}
1979				b += num;
1980				nr -= num;
1981				if (nr == 0)
1982					break;
1983				c = *b;
1984				if (process_output(c, tty) < 0)
1985					break;
1986				b++; nr--;
1987			}
1988			if (tty->ops->flush_chars)
1989				tty->ops->flush_chars(tty);
1990		} else {
 
 
1991			while (nr > 0) {
 
1992				c = tty->ops->write(tty, b, nr);
 
1993				if (c < 0) {
1994					retval = c;
1995					goto break_out;
1996				}
1997				if (!c)
1998					break;
1999				b += c;
2000				nr -= c;
2001			}
2002		}
2003		if (!nr)
2004			break;
2005		if (file->f_flags & O_NONBLOCK) {
2006			retval = -EAGAIN;
2007			break;
2008		}
2009		schedule();
 
 
 
 
2010	}
2011break_out:
2012	__set_current_state(TASK_RUNNING);
2013	remove_wait_queue(&tty->write_wait, &wait);
2014	if (b - buf != nr && tty->fasync)
2015		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 
2016	return (b - buf) ? b - buf : retval;
2017}
2018
2019/**
2020 *	n_tty_poll		-	poll method for N_TTY
2021 *	@tty: terminal device
2022 *	@file: file accessing it
2023 *	@wait: poll table
2024 *
2025 *	Called when the line discipline is asked to poll() for data or
2026 *	for special events. This code is not serialized with respect to
2027 *	other events save open/close.
2028 *
2029 *	This code must be sure never to sleep through a hangup.
2030 *	Called without the kernel lock held - fine
2031 */
2032
2033static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2034							poll_table *wait)
2035{
2036	unsigned int mask = 0;
2037
2038	poll_wait(file, &tty->read_wait, wait);
2039	poll_wait(file, &tty->write_wait, wait);
2040	if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2041		mask |= POLLIN | POLLRDNORM;
 
 
 
 
 
2042	if (tty->packet && tty->link->ctrl_status)
2043		mask |= POLLPRI | POLLIN | POLLRDNORM;
2044	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2045		mask |= POLLHUP;
2046	if (tty_hung_up_p(file))
2047		mask |= POLLHUP;
2048	if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2049		if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2050			tty->minimum_to_wake = MIN_CHAR(tty);
2051		else
2052			tty->minimum_to_wake = 1;
2053	}
2054	if (tty->ops->write && !tty_is_writelocked(tty) &&
2055			tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2056			tty_write_room(tty) > 0)
2057		mask |= POLLOUT | POLLWRNORM;
2058	return mask;
2059}
2060
2061static unsigned long inq_canon(struct tty_struct *tty)
2062{
2063	int nr, head, tail;
2064
2065	if (!tty->canon_data)
2066		return 0;
2067	head = tty->canon_head;
2068	tail = tty->read_tail;
2069	nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2070	/* Skip EOF-chars.. */
2071	while (head != tail) {
2072		if (test_bit(tail, tty->read_flags) &&
2073		    tty->read_buf[tail] == __DISABLED_CHAR)
2074			nr--;
2075		tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2076	}
2077	return nr;
2078}
2079
2080static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2081		       unsigned int cmd, unsigned long arg)
2082{
 
2083	int retval;
2084
2085	switch (cmd) {
2086	case TIOCOUTQ:
2087		return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2088	case TIOCINQ:
2089		/* FIXME: Locking */
2090		retval = tty->read_cnt;
2091		if (L_ICANON(tty))
2092			retval = inq_canon(tty);
 
 
2093		return put_user(retval, (unsigned int __user *) arg);
2094	default:
2095		return n_tty_ioctl_helper(tty, file, cmd, arg);
2096	}
2097}
2098
2099struct tty_ldisc_ops tty_ldisc_N_TTY = {
2100	.magic           = TTY_LDISC_MAGIC,
2101	.name            = "n_tty",
2102	.open            = n_tty_open,
2103	.close           = n_tty_close,
2104	.flush_buffer    = n_tty_flush_buffer,
2105	.chars_in_buffer = n_tty_chars_in_buffer,
2106	.read            = n_tty_read,
2107	.write           = n_tty_write,
2108	.ioctl           = n_tty_ioctl,
2109	.set_termios     = n_tty_set_termios,
2110	.poll            = n_tty_poll,
2111	.receive_buf     = n_tty_receive_buf,
2112	.write_wakeup    = n_tty_write_wakeup
 
2113};
2114
2115/**
2116 *	n_tty_inherit_ops	-	inherit N_TTY methods
2117 *	@ops: struct tty_ldisc_ops where to save N_TTY methods
2118 *
2119 *	Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
2120 *	methods.
2121 */
2122
2123void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2124{
2125	*ops = tty_ldisc_N_TTY;
2126	ops->owner = NULL;
2127	ops->refcount = ops->flags = 0;
2128}
2129EXPORT_SYMBOL_GPL(n_tty_inherit_ops);