linux/drivers/tty/n_tty.c
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   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);
2130
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