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