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