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