drivers/char/n_tty.c

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