drivers/tty/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 #include <linux/module.h>
  52
  53
  54 /* number of characters left in xmit buffer before select has we have room */
  55 #define WAKEUP_CHARS 256
  56
  57 /*
  58  * This defines the low- and high-watermarks for throttling and
  59  * unthrottling the TTY driver.  These watermarks are used for
  60  * controlling the space in the read buffer.
  61  */
  62 #define TTY_THRESHOLD_THROTTLE          128 /* now based on remaining room */
  63 #define TTY_THRESHOLD_UNTHROTTLE        128
  64
  65 /*
  66  * Special byte codes used in the echo buffer to represent operations
  67  * or special handling of characters.  Bytes in the echo buffer that
  68  * are not part of such special blocks are treated as normal character
  69  * codes.
  70  */
  71 #define ECHO_OP_START 0xff
  72 #define ECHO_OP_MOVE_BACK_COL 0x80
  73 #define ECHO_OP_SET_CANON_COL 0x81
  74 #define ECHO_OP_ERASE_TAB 0x82
  75
  76 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
  77                                unsigned char __user *ptr)
  78 {
  79         tty_audit_add_data(tty, &x, 1);
  80         return put_user(x, ptr);
  81 }
  82
  83 /**
  84  *      n_tty_set__room -       receive space
  85  *      @tty: terminal
  86  *
  87  *      Called by the driver to find out how much data it is
  88  *      permitted to feed to the line discipline without any being lost
  89  *      and thus to manage flow control. Not serialized. Answers for the
  90  *      "instant".
  91  */
  92
  93 static void n_tty_set_room(struct tty_struct *tty)
  94 {
  95         /* tty->read_cnt is not read locked ? */
  96         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
  97         int old_left;
  98
  99         /*
 100          * If we are doing input canonicalization, and there are no
 101          * pending newlines, let characters through without limit, so
 102          * that erase characters will be handled.  Other excess
 103          * characters will be beeped.
 104          */
 105         if (left <= 0)
 106                 left = tty->icanon && !tty->canon_data;
 107         old_left = tty->receive_room;
 108         tty->receive_room = left;
 109
 110         /* Did this open up the receive buffer? We may need to flip */
 111         if (left && !old_left)
 112                 schedule_work(&tty->buf.work);
 113 }
 114
 115 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
 116 {
 117         if (tty->read_cnt < N_TTY_BUF_SIZE) {
 118                 tty->read_buf[tty->read_head] = c;
 119                 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
 120                 tty->read_cnt++;
 121         }
 122 }
 123
 124 /**
 125  *      put_tty_queue           -       add character to tty
 126  *      @c: character
 127  *      @tty: tty device
 128  *
 129  *      Add a character to the tty read_buf queue. This is done under the
 130  *      read_lock to serialize character addition and also to protect us
 131  *      against parallel reads or flushes
 132  */
 133
 134 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
 135 {
 136         unsigned long flags;
 137         /*
 138          *      The problem of stomping on the buffers ends here.
 139          *      Why didn't anyone see this one coming? --AJK
 140         */
 141         spin_lock_irqsave(&tty->read_lock, flags);
 142         put_tty_queue_nolock(c, tty);
 143         spin_unlock_irqrestore(&tty->read_lock, flags);
 144 }
 145
 146 /**
 147  *      check_unthrottle        -       allow new receive data
 148  *      @tty; tty device
 149  *
 150  *      Check whether to call the driver unthrottle functions
 151  *
 152  *      Can sleep, may be called under the atomic_read_lock mutex but
 153  *      this is not guaranteed.
 154  */
 155 static void check_unthrottle(struct tty_struct *tty)
 156 {
 157         if (tty->count)
 158                 tty_unthrottle(tty);
 159 }
 160
 161 /**
 162  *      reset_buffer_flags      -       reset buffer state
 163  *      @tty: terminal to reset
 164  *
 165  *      Reset the read buffer counters, clear the flags,
 166  *      and make sure the driver is unthrottled. Called
 167  *      from n_tty_open() and n_tty_flush_buffer().
 168  *
 169  *      Locking: tty_read_lock for read fields.
 170  */
 171
 172 static void reset_buffer_flags(struct tty_struct *tty)
 173 {
 174         unsigned long flags;
 175
 176         spin_lock_irqsave(&tty->read_lock, flags);
 177         tty->read_head = tty->read_tail = tty->read_cnt = 0;
 178         spin_unlock_irqrestore(&tty->read_lock, flags);
 179
 180         mutex_lock(&tty->echo_lock);
 181         tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
 182         mutex_unlock(&tty->echo_lock);
 183
 184         tty->canon_head = tty->canon_data = tty->erasing = 0;
 185         memset(&tty->read_flags, 0, sizeof tty->read_flags);
 186         n_tty_set_room(tty);
 187 }
 188
 189 /**
 190  *      n_tty_flush_buffer      -       clean input queue
 191  *      @tty:   terminal device
 192  *
 193  *      Flush the input buffer. Called when the line discipline is
 194  *      being closed, when the tty layer wants the buffer flushed (eg
 195  *      at hangup) or when the N_TTY line discipline internally has to
 196  *      clean the pending queue (for example some signals).
 197  *
 198  *      Locking: ctrl_lock, read_lock.
 199  */
 200
 201 static void n_tty_flush_buffer(struct tty_struct *tty)
 202 {
 203         unsigned long flags;
 204         /* clear everything and unthrottle the driver */
 205         reset_buffer_flags(tty);
 206
 207         if (!tty->link)
 208                 return;
 209
 210         spin_lock_irqsave(&tty->ctrl_lock, flags);
 211         if (tty->link->packet) {
 212                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
 213                 wake_up_interruptible(&tty->link->read_wait);
 214         }
 215         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 216 }
 217
 218 /**
 219  *      n_tty_chars_in_buffer   -       report available bytes
 220  *      @tty: tty device
 221  *
 222  *      Report the number of characters buffered to be delivered to user
 223  *      at this instant in time.
 224  *
 225  *      Locking: read_lock
 226  */
 227
 228 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
 229 {
 230         unsigned long flags;
 231         ssize_t n = 0;
 232
 233         spin_lock_irqsave(&tty->read_lock, flags);
 234         if (!tty->icanon) {
 235                 n = tty->read_cnt;
 236         } else if (tty->canon_data) {
 237                 n = (tty->canon_head > tty->read_tail) ?
 238                         tty->canon_head - tty->read_tail :
 239                         tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
 240         }
 241         spin_unlock_irqrestore(&tty->read_lock, flags);
 242         return n;
 243 }
 244
 245 /**
 246  *      is_utf8_continuation    -       utf8 multibyte check
 247  *      @c: byte to check
 248  *
 249  *      Returns true if the utf8 character 'c' is a multibyte continuation
 250  *      character. We use this to correctly compute the on screen size
 251  *      of the character when printing
 252  */
 253
 254 static inline int is_utf8_continuation(unsigned char c)
 255 {
 256         return (c & 0xc0) == 0x80;
 257 }
 258
 259 /**
 260  *      is_continuation         -       multibyte check
 261  *      @c: byte to check
 262  *
 263  *      Returns true if the utf8 character 'c' is a multibyte continuation
 264  *      character and the terminal is in unicode mode.
 265  */
 266
 267 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
 268 {
 269         return I_IUTF8(tty) && is_utf8_continuation(c);
 270 }
 271
 272 /**
 273  *      do_output_char                  -       output one character
 274  *      @c: character (or partial unicode symbol)
 275  *      @tty: terminal device
 276  *      @space: space available in tty driver write buffer
 277  *
 278  *      This is a helper function that handles one output character
 279  *      (including special characters like TAB, CR, LF, etc.),
 280  *      doing OPOST processing and putting the results in the
 281  *      tty driver's write buffer.
 282  *
 283  *      Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
 284  *      and NLDLY.  They simply aren't relevant in the world today.
 285  *      If you ever need them, add them here.
 286  *
 287  *      Returns the number of bytes of buffer space used or -1 if
 288  *      no space left.
 289  *
 290  *      Locking: should be called under the output_lock to protect
 291  *               the column state and space left in the buffer
 292  */
 293
 294 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
 295 {
 296         int     spaces;
 297
 298         if (!space)
 299                 return -1;
 300
 301         switch (c) {
 302         case '\n':
 303                 if (O_ONLRET(tty))
 304                         tty->column = 0;
 305                 if (O_ONLCR(tty)) {
 306                         if (space < 2)
 307                                 return -1;
 308                         tty->canon_column = tty->column = 0;
 309                         tty->ops->write(tty, "\r\n", 2);
 310                         return 2;
 311                 }
 312                 tty->canon_column = tty->column;
 313                 break;
 314         case '\r':
 315                 if (O_ONOCR(tty) && tty->column == 0)
 316                         return 0;
 317                 if (O_OCRNL(tty)) {
 318                         c = '\n';
 319                         if (O_ONLRET(tty))
 320                                 tty->canon_column = tty->column = 0;
 321                         break;
 322                 }
 323                 tty->canon_column = tty->column = 0;
 324                 break;
 325         case '\t':
 326                 spaces = 8 - (tty->column & 7);
 327                 if (O_TABDLY(tty) == XTABS) {
 328                         if (space < spaces)
 329                                 return -1;
 330                         tty->column += spaces;
 331                         tty->ops->write(tty, "        ", spaces);
 332                         return spaces;
 333                 }
 334                 tty->column += spaces;
 335                 break;
 336         case '\b':
 337                 if (tty->column > 0)
 338                         tty->column--;
 339                 break;
 340         default:
 341                 if (!iscntrl(c)) {
 342                         if (O_OLCUC(tty))
 343                                 c = toupper(c);
 344                         if (!is_continuation(c, tty))
 345                                 tty->column++;
 346                 }
 347                 break;
 348         }
 349
 350         tty_put_char(tty, c);
 351         return 1;
 352 }
 353
 354 /**
 355  *      process_output                  -       output post processor
 356  *      @c: character (or partial unicode symbol)
 357  *      @tty: terminal device
 358  *
 359  *      Output one character with OPOST processing.
 360  *      Returns -1 when the output device is full and the character
 361  *      must be retried.
 362  *
 363  *      Locking: output_lock to protect column state and space left
 364  *               (also, this is called from n_tty_write under the
 365  *                tty layer write lock)
 366  */
 367
 368 static int process_output(unsigned char c, struct tty_struct *tty)
 369 {
 370         int     space, retval;
 371
 372         mutex_lock(&tty->output_lock);
 373
 374         space = tty_write_room(tty);
 375         retval = do_output_char(c, tty, space);
 376
 377         mutex_unlock(&tty->output_lock);
 378         if (retval < 0)
 379                 return -1;
 380         else
 381                 return 0;
 382 }
 383
 384 /**
 385  *      process_output_block            -       block post processor
 386  *      @tty: terminal device
 387  *      @buf: character buffer
 388  *      @nr: number of bytes to output
 389  *
 390  *      Output a block of characters with OPOST processing.
 391  *      Returns the number of characters output.
 392  *
 393  *      This path is used to speed up block console writes, among other
 394  *      things when processing blocks of output data. It handles only
 395  *      the simple cases normally found and helps to generate blocks of
 396  *      symbols for the console driver and thus improve performance.
 397  *
 398  *      Locking: output_lock to protect column state and space left
 399  *               (also, this is called from n_tty_write under the
 400  *                tty layer write lock)
 401  */
 402
 403 static ssize_t process_output_block(struct tty_struct *tty,
 404                                     const unsigned char *buf, unsigned int nr)
 405 {
 406         int     space;
 407         int     i;
 408         const unsigned char *cp;
 409
 410         mutex_lock(&tty->output_lock);
 411
 412         space = tty_write_room(tty);
 413         if (!space) {
 414                 mutex_unlock(&tty->output_lock);
 415                 return 0;
 416         }
 417         if (nr > space)
 418                 nr = space;
 419
 420         for (i = 0, cp = buf; i < nr; i++, cp++) {
 421                 unsigned char c = *cp;
 422
 423                 switch (c) {
 424                 case '\n':
 425                         if (O_ONLRET(tty))
 426                                 tty->column = 0;
 427                         if (O_ONLCR(tty))
 428                                 goto break_out;
 429                         tty->canon_column = tty->column;
 430                         break;
 431                 case '\r':
 432                         if (O_ONOCR(tty) && tty->column == 0)
 433                                 goto break_out;
 434                         if (O_OCRNL(tty))
 435                                 goto break_out;
 436                         tty->canon_column = tty->column = 0;
 437                         break;
 438                 case '\t':
 439                         goto break_out;
 440                 case '\b':
 441                         if (tty->column > 0)
 442                                 tty->column--;
 443                         break;
 444                 default:
 445                         if (!iscntrl(c)) {
 446                                 if (O_OLCUC(tty))
 447                                         goto break_out;
 448                                 if (!is_continuation(c, tty))
 449                                         tty->column++;
 450                         }
 451                         break;
 452                 }
 453         }
 454 break_out:
 455         i = tty->ops->write(tty, buf, i);
 456
 457         mutex_unlock(&tty->output_lock);
 458         return i;
 459 }
 460
 461 /**
 462  *      process_echoes  -       write pending echo characters
 463  *      @tty: terminal device
 464  *
 465  *      Write previously buffered echo (and other ldisc-generated)
 466  *      characters to the tty.
 467  *
 468  *      Characters generated by the ldisc (including echoes) need to
 469  *      be buffered because the driver's write buffer can fill during
 470  *      heavy program output.  Echoing straight to the driver will
 471  *      often fail under these conditions, causing lost characters and
 472  *      resulting mismatches of ldisc state information.
 473  *
 474  *      Since the ldisc state must represent the characters actually sent
 475  *      to the driver at the time of the write, operations like certain
 476  *      changes in column state are also saved in the buffer and executed
 477  *      here.
 478  *
 479  *      A circular fifo buffer is used so that the most recent characters
 480  *      are prioritized.  Also, when control characters are echoed with a
 481  *      prefixed "^", the pair is treated atomically and thus not separated.
 482  *
 483  *      Locking: output_lock to protect column state and space left,
 484  *               echo_lock to protect the echo buffer
 485  */
 486
 487 static void process_echoes(struct tty_struct *tty)
 488 {
 489         int     space, nr;
 490         unsigned char c;
 491         unsigned char *cp, *buf_end;
 492
 493         if (!tty->echo_cnt)
 494                 return;
 495
 496         mutex_lock(&tty->output_lock);
 497         mutex_lock(&tty->echo_lock);
 498
 499         space = tty_write_room(tty);
 500
 501         buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
 502         cp = tty->echo_buf + tty->echo_pos;
 503         nr = tty->echo_cnt;
 504         while (nr > 0) {
 505                 c = *cp;
 506                 if (c == ECHO_OP_START) {
 507                         unsigned char op;
 508                         unsigned char *opp;
 509                         int no_space_left = 0;
 510
 511                         /*
 512                          * If the buffer byte is the start of a multi-byte
 513                          * operation, get the next byte, which is either the
 514                          * op code or a control character value.
 515                          */
 516                         opp = cp + 1;
 517                         if (opp == buf_end)
 518                                 opp -= N_TTY_BUF_SIZE;
 519                         op = *opp;
 520
 521                         switch (op) {
 522                                 unsigned int num_chars, num_bs;
 523
 524                         case ECHO_OP_ERASE_TAB:
 525                                 if (++opp == buf_end)
 526                                         opp -= N_TTY_BUF_SIZE;
 527                                 num_chars = *opp;
 528
 529                                 /*
 530                                  * Determine how many columns to go back
 531                                  * in order to erase the tab.
 532                                  * This depends on the number of columns
 533                                  * used by other characters within the tab
 534                                  * area.  If this (modulo 8) count is from
 535                                  * the start of input rather than from a
 536                                  * previous tab, we offset by canon column.
 537                                  * Otherwise, tab spacing is normal.
 538                                  */
 539                                 if (!(num_chars & 0x80))
 540                                         num_chars += tty->canon_column;
 541                                 num_bs = 8 - (num_chars & 7);
 542
 543                                 if (num_bs > space) {
 544                                         no_space_left = 1;
 545                                         break;
 546                                 }
 547                                 space -= num_bs;
 548                                 while (num_bs--) {
 549                                         tty_put_char(tty, '\b');
 550                                         if (tty->column > 0)
 551                                                 tty->column--;
 552                                 }
 553                                 cp += 3;
 554                                 nr -= 3;
 555                                 break;
 556
 557                         case ECHO_OP_SET_CANON_COL:
 558                                 tty->canon_column = tty->column;
 559                                 cp += 2;
 560                                 nr -= 2;
 561                                 break;
 562
 563                         case ECHO_OP_MOVE_BACK_COL:
 564                                 if (tty->column > 0)
 565                                         tty->column--;
 566                                 cp += 2;
 567                                 nr -= 2;
 568                                 break;
 569
 570                         case ECHO_OP_START:
 571                                 /* This is an escaped echo op start code */
 572                                 if (!space) {
 573                                         no_space_left = 1;
 574                                         break;
 575                                 }
 576                                 tty_put_char(tty, ECHO_OP_START);
 577                                 tty->column++;
 578                                 space--;
 579                                 cp += 2;
 580                                 nr -= 2;
 581                                 break;
 582
 583                         default:
 584                                 /*
 585                                  * If the op is not a special byte code,
 586                                  * it is a ctrl char tagged to be echoed
 587                                  * as "^X" (where X is the letter
 588                                  * representing the control char).
 589                                  * Note that we must ensure there is
 590                                  * enough space for the whole ctrl pair.
 591                                  *
 592                                  */
 593                                 if (space < 2) {
 594                                         no_space_left = 1;
 595                                         break;
 596                                 }
 597                                 tty_put_char(tty, '^');
 598                                 tty_put_char(tty, op ^ 0100);
 599                                 tty->column += 2;
 600                                 space -= 2;
 601                                 cp += 2;
 602                                 nr -= 2;
 603                         }
 604
 605                         if (no_space_left)
 606                                 break;
 607                 } else {
 608                         if (O_OPOST(tty) &&
 609                             !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
 610                                 int retval = do_output_char(c, tty, space);
 611                                 if (retval < 0)
 612                                         break;
 613                                 space -= retval;
 614                         } else {
 615                                 if (!space)
 616                                         break;
 617                                 tty_put_char(tty, c);
 618                                 space -= 1;
 619                         }
 620                         cp += 1;
 621                         nr -= 1;
 622                 }
 623
 624                 /* When end of circular buffer reached, wrap around */
 625                 if (cp >= buf_end)
 626                         cp -= N_TTY_BUF_SIZE;
 627         }
 628
 629         if (nr == 0) {
 630                 tty->echo_pos = 0;
 631                 tty->echo_cnt = 0;
 632                 tty->echo_overrun = 0;
 633         } else {
 634                 int num_processed = tty->echo_cnt - nr;
 635                 tty->echo_pos += num_processed;
 636                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
 637                 tty->echo_cnt = nr;
 638                 if (num_processed > 0)
 639                         tty->echo_overrun = 0;
 640         }
 641
 642         mutex_unlock(&tty->echo_lock);
 643         mutex_unlock(&tty->output_lock);
 644
 645         if (tty->ops->flush_chars)
 646                 tty->ops->flush_chars(tty);
 647 }
 648
 649 /**
 650  *      add_echo_byte   -       add a byte to the echo buffer
 651  *      @c: unicode byte to echo
 652  *      @tty: terminal device
 653  *
 654  *      Add a character or operation byte to the echo buffer.
 655  *
 656  *      Should be called under the echo lock to protect the echo buffer.
 657  */
 658
 659 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
 660 {
 661         int     new_byte_pos;
 662
 663         if (tty->echo_cnt == N_TTY_BUF_SIZE) {
 664                 /* Circular buffer is already at capacity */
 665                 new_byte_pos = tty->echo_pos;
 666
 667                 /*
 668                  * Since the buffer start position needs to be advanced,
 669                  * be sure to step by a whole operation byte group.
 670                  */
 671                 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
 672                         if (tty->echo_buf[(tty->echo_pos + 1) &
 673                                           (N_TTY_BUF_SIZE - 1)] ==
 674                                                 ECHO_OP_ERASE_TAB) {
 675                                 tty->echo_pos += 3;
 676                                 tty->echo_cnt -= 2;
 677                         } else {
 678                                 tty->echo_pos += 2;
 679                                 tty->echo_cnt -= 1;
 680                         }
 681                 } else {
 682                         tty->echo_pos++;
 683                 }
 684                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
 685
 686                 tty->echo_overrun = 1;
 687         } else {
 688                 new_byte_pos = tty->echo_pos + tty->echo_cnt;
 689                 new_byte_pos &= N_TTY_BUF_SIZE - 1;
 690                 tty->echo_cnt++;
 691         }
 692
 693         tty->echo_buf[new_byte_pos] = c;
 694 }
 695
 696 /**
 697  *      echo_move_back_col      -       add operation to move back a column
 698  *      @tty: terminal device
 699  *
 700  *      Add an operation to the echo buffer to move back one column.
 701  *
 702  *      Locking: echo_lock to protect the echo buffer
 703  */
 704
 705 static void echo_move_back_col(struct tty_struct *tty)
 706 {
 707         mutex_lock(&tty->echo_lock);
 708
 709         add_echo_byte(ECHO_OP_START, tty);
 710         add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
 711
 712         mutex_unlock(&tty->echo_lock);
 713 }
 714
 715 /**
 716  *      echo_set_canon_col      -       add operation to set the canon column
 717  *      @tty: terminal device
 718  *
 719  *      Add an operation to the echo buffer to set the canon column
 720  *      to the current column.
 721  *
 722  *      Locking: echo_lock to protect the echo buffer
 723  */
 724
 725 static void echo_set_canon_col(struct tty_struct *tty)
 726 {
 727         mutex_lock(&tty->echo_lock);
 728
 729         add_echo_byte(ECHO_OP_START, tty);
 730         add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
 731
 732         mutex_unlock(&tty->echo_lock);
 733 }
 734
 735 /**
 736  *      echo_erase_tab  -       add operation to erase a tab
 737  *      @num_chars: number of character columns already used
 738  *      @after_tab: true if num_chars starts after a previous tab
 739  *      @tty: terminal device
 740  *
 741  *      Add an operation to the echo buffer to erase a tab.
 742  *
 743  *      Called by the eraser function, which knows how many character
 744  *      columns have been used since either a previous tab or the start
 745  *      of input.  This information will be used later, along with
 746  *      canon column (if applicable), to go back the correct number
 747  *      of columns.
 748  *
 749  *      Locking: echo_lock to protect the echo buffer
 750  */
 751
 752 static void echo_erase_tab(unsigned int num_chars, int after_tab,
 753                            struct tty_struct *tty)
 754 {
 755         mutex_lock(&tty->echo_lock);
 756
 757         add_echo_byte(ECHO_OP_START, tty);
 758         add_echo_byte(ECHO_OP_ERASE_TAB, tty);
 759
 760         /* We only need to know this modulo 8 (tab spacing) */
 761         num_chars &= 7;
 762
 763         /* Set the high bit as a flag if num_chars is after a previous tab */
 764         if (after_tab)
 765                 num_chars |= 0x80;
 766
 767         add_echo_byte(num_chars, tty);
 768
 769         mutex_unlock(&tty->echo_lock);
 770 }
 771
 772 /**
 773  *      echo_char_raw   -       echo a character raw
 774  *      @c: unicode byte to echo
 775  *      @tty: terminal device
 776  *
 777  *      Echo user input back onto the screen. This must be called only when
 778  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
 779  *
 780  *      This variant does not treat control characters specially.
 781  *
 782  *      Locking: echo_lock to protect the echo buffer
 783  */
 784
 785 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
 786 {
 787         mutex_lock(&tty->echo_lock);
 788
 789         if (c == ECHO_OP_START) {
 790                 add_echo_byte(ECHO_OP_START, tty);
 791                 add_echo_byte(ECHO_OP_START, tty);
 792         } else {
 793                 add_echo_byte(c, tty);
 794         }
 795
 796         mutex_unlock(&tty->echo_lock);
 797 }
 798
 799 /**
 800  *      echo_char       -       echo a character
 801  *      @c: unicode byte to echo
 802  *      @tty: terminal device
 803  *
 804  *      Echo user input back onto the screen. This must be called only when
 805  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
 806  *
 807  *      This variant tags control characters to be echoed as "^X"
 808  *      (where X is the letter representing the control char).
 809  *
 810  *      Locking: echo_lock to protect the echo buffer
 811  */
 812
 813 static void echo_char(unsigned char c, struct tty_struct *tty)
 814 {
 815         mutex_lock(&tty->echo_lock);
 816
 817         if (c == ECHO_OP_START) {
 818                 add_echo_byte(ECHO_OP_START, tty);
 819                 add_echo_byte(ECHO_OP_START, tty);
 820         } else {
 821                 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
 822                         add_echo_byte(ECHO_OP_START, tty);
 823                 add_echo_byte(c, tty);
 824         }
 825
 826         mutex_unlock(&tty->echo_lock);
 827 }
 828
 829 /**
 830  *      finish_erasing          -       complete erase
 831  *      @tty: tty doing the erase
 832  */
 833
 834 static inline void finish_erasing(struct tty_struct *tty)
 835 {
 836         if (tty->erasing) {
 837                 echo_char_raw('/', tty);
 838                 tty->erasing = 0;
 839         }
 840 }
 841
 842 /**
 843  *      eraser          -       handle erase function
 844  *      @c: character input
 845  *      @tty: terminal device
 846  *
 847  *      Perform erase and necessary output when an erase character is
 848  *      present in the stream from the driver layer. Handles the complexities
 849  *      of UTF-8 multibyte symbols.
 850  *
 851  *      Locking: read_lock for tty buffers
 852  */
 853
 854 static void eraser(unsigned char c, struct tty_struct *tty)
 855 {
 856         enum { ERASE, WERASE, KILL } kill_type;
 857         int head, seen_alnums, cnt;
 858         unsigned long flags;
 859
 860         /* FIXME: locking needed ? */
 861         if (tty->read_head == tty->canon_head) {
 862                 /* process_output('\a', tty); */ /* what do you think? */
 863                 return;
 864         }
 865         if (c == ERASE_CHAR(tty))
 866                 kill_type = ERASE;
 867         else if (c == WERASE_CHAR(tty))
 868                 kill_type = WERASE;
 869         else {
 870                 if (!L_ECHO(tty)) {
 871                         spin_lock_irqsave(&tty->read_lock, flags);
 872                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 873                                           (N_TTY_BUF_SIZE - 1));
 874                         tty->read_head = tty->canon_head;
 875                         spin_unlock_irqrestore(&tty->read_lock, flags);
 876                         return;
 877                 }
 878                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
 879                         spin_lock_irqsave(&tty->read_lock, flags);
 880                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 881                                           (N_TTY_BUF_SIZE - 1));
 882                         tty->read_head = tty->canon_head;
 883                         spin_unlock_irqrestore(&tty->read_lock, flags);
 884                         finish_erasing(tty);
 885                         echo_char(KILL_CHAR(tty), tty);
 886                         /* Add a newline if ECHOK is on and ECHOKE is off. */
 887                         if (L_ECHOK(tty))
 888                                 echo_char_raw('\n', tty);
 889                         return;
 890                 }
 891                 kill_type = KILL;
 892         }
 893
 894         seen_alnums = 0;
 895         /* FIXME: Locking ?? */
 896         while (tty->read_head != tty->canon_head) {
 897                 head = tty->read_head;
 898
 899                 /* erase a single possibly multibyte character */
 900                 do {
 901                         head = (head - 1) & (N_TTY_BUF_SIZE-1);
 902                         c = tty->read_buf[head];
 903                 } while (is_continuation(c, tty) && head != tty->canon_head);
 904
 905                 /* do not partially erase */
 906                 if (is_continuation(c, tty))
 907                         break;
 908
 909                 if (kill_type == WERASE) {
 910                         /* Equivalent to BSD's ALTWERASE. */
 911                         if (isalnum(c) || c == '_')
 912                                 seen_alnums++;
 913                         else if (seen_alnums)
 914                                 break;
 915                 }
 916                 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
 917                 spin_lock_irqsave(&tty->read_lock, flags);
 918                 tty->read_head = head;
 919                 tty->read_cnt -= cnt;
 920                 spin_unlock_irqrestore(&tty->read_lock, flags);
 921                 if (L_ECHO(tty)) {
 922                         if (L_ECHOPRT(tty)) {
 923                                 if (!tty->erasing) {
 924                                         echo_char_raw('\\', tty);
 925                                         tty->erasing = 1;
 926                                 }
 927                                 /* if cnt > 1, output a multi-byte character */
 928                                 echo_char(c, tty);
 929                                 while (--cnt > 0) {
 930                                         head = (head+1) & (N_TTY_BUF_SIZE-1);
 931                                         echo_char_raw(tty->read_buf[head], tty);
 932                                         echo_move_back_col(tty);
 933                                 }
 934                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
 935                                 echo_char(ERASE_CHAR(tty), tty);
 936                         } else if (c == '\t') {
 937                                 unsigned int num_chars = 0;
 938                                 int after_tab = 0;
 939                                 unsigned long tail = tty->read_head;
 940
 941                                 /*
 942                                  * Count the columns used for characters
 943                                  * since the start of input or after a
 944                                  * previous tab.
 945                                  * This info is used to go back the correct
 946                                  * number of columns.
 947                                  */
 948                                 while (tail != tty->canon_head) {
 949                                         tail = (tail-1) & (N_TTY_BUF_SIZE-1);
 950                                         c = tty->read_buf[tail];
 951                                         if (c == '\t') {
 952                                                 after_tab = 1;
 953                                                 break;
 954                                         } else if (iscntrl(c)) {
 955                                                 if (L_ECHOCTL(tty))
 956                                                         num_chars += 2;
 957                                         } else if (!is_continuation(c, tty)) {
 958                                                 num_chars++;
 959                                         }
 960                                 }
 961                                 echo_erase_tab(num_chars, after_tab, tty);
 962                         } else {
 963                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
 964                                         echo_char_raw('\b', tty);
 965                                         echo_char_raw(' ', tty);
 966                                         echo_char_raw('\b', tty);
 967                                 }
 968                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
 969                                         echo_char_raw('\b', tty);
 970                                         echo_char_raw(' ', tty);
 971                                         echo_char_raw('\b', tty);
 972                                 }
 973                         }
 974                 }
 975                 if (kill_type == ERASE)
 976                         break;
 977         }
 978         if (tty->read_head == tty->canon_head && L_ECHO(tty))
 979                 finish_erasing(tty);
 980 }
 981
 982 /**
 983  *      isig            -       handle the ISIG optio
 984  *      @sig: signal
 985  *      @tty: terminal
 986  *      @flush: force flush
 987  *
 988  *      Called when a signal is being sent due to terminal input. This
 989  *      may caus terminal flushing to take place according to the termios
 990  *      settings and character used. Called from the driver receive_buf
 991  *      path so serialized.
 992  *
 993  *      Locking: ctrl_lock, read_lock (both via flush buffer)
 994  */
 995
 996 static inline void isig(int sig, struct tty_struct *tty, int flush)
 997 {
 998         if (tty->pgrp)
 999                 kill_pgrp(tty->pgrp, sig, 1);
1000         if (flush || !L_NOFLSH(tty)) {
1001                 n_tty_flush_buffer(tty);
1002                 tty_driver_flush_buffer(tty);
1003         }
1004 }
1005
1006 /**
1007  *      n_tty_receive_break     -       handle break
1008  *      @tty: terminal
1009  *
1010  *      An RS232 break event has been hit in the incoming bitstream. This
1011  *      can cause a variety of events depending upon the termios settings.
1012  *
1013  *      Called from the receive_buf path so single threaded.
1014  */
1015
1016 static inline void n_tty_receive_break(struct tty_struct *tty)
1017 {
1018         if (I_IGNBRK(tty))
1019                 return;
1020         if (I_BRKINT(tty)) {
1021                 isig(SIGINT, tty, 1);
1022                 return;
1023         }
1024         if (I_PARMRK(tty)) {
1025                 put_tty_queue('\377', tty);
1026                 put_tty_queue('\0', tty);
1027         }
1028         put_tty_queue('\0', tty);
1029         wake_up_interruptible(&tty->read_wait);
1030 }
1031
1032 /**
1033  *      n_tty_receive_overrun   -       handle overrun reporting
1034  *      @tty: terminal
1035  *
1036  *      Data arrived faster than we could process it. While the tty
1037  *      driver has flagged this the bits that were missed are gone
1038  *      forever.
1039  *
1040  *      Called from the receive_buf path so single threaded. Does not
1041  *      need locking as num_overrun and overrun_time are function
1042  *      private.
1043  */
1044
1045 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1046 {
1047         char buf[64];
1048
1049         tty->num_overrun++;
1050         if (time_before(tty->overrun_time, jiffies - HZ) ||
1051                         time_after(tty->overrun_time, jiffies)) {
1052                 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1053                         tty_name(tty, buf),
1054                         tty->num_overrun);
1055                 tty->overrun_time = jiffies;
1056                 tty->num_overrun = 0;
1057         }
1058 }
1059
1060 /**
1061  *      n_tty_receive_parity_error      -       error notifier
1062  *      @tty: terminal device
1063  *      @c: character
1064  *
1065  *      Process a parity error and queue the right data to indicate
1066  *      the error case if necessary. Locking as per n_tty_receive_buf.
1067  */
1068 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1069                                               unsigned char c)
1070 {
1071         if (I_IGNPAR(tty))
1072                 return;
1073         if (I_PARMRK(tty)) {
1074                 put_tty_queue('\377', tty);
1075                 put_tty_queue('\0', tty);
1076                 put_tty_queue(c, tty);
1077         } else  if (I_INPCK(tty))
1078                 put_tty_queue('\0', tty);
1079         else
1080                 put_tty_queue(c, tty);
1081         wake_up_interruptible(&tty->read_wait);
1082 }
1083
1084 /**
1085  *      n_tty_receive_char      -       perform processing
1086  *      @tty: terminal device
1087  *      @c: character
1088  *
1089  *      Process an individual character of input received from the driver.
1090  *      This is serialized with respect to itself by the rules for the
1091  *      driver above.
1092  */
1093
1094 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1095 {
1096         unsigned long flags;
1097         int parmrk;
1098
1099         if (tty->raw) {
1100                 put_tty_queue(c, tty);
1101                 return;
1102         }
1103
1104         if (I_ISTRIP(tty))
1105                 c &= 0x7f;
1106         if (I_IUCLC(tty) && L_IEXTEN(tty))
1107                 c = tolower(c);
1108
1109         if (L_EXTPROC(tty)) {
1110                 put_tty_queue(c, tty);
1111                 return;
1112         }
1113
1114         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1115             I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1116             c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1117                 start_tty(tty);
1118                 process_echoes(tty);
1119         }
1120
1121         if (tty->closing) {
1122                 if (I_IXON(tty)) {
1123                         if (c == START_CHAR(tty)) {
1124                                 start_tty(tty);
1125                                 process_echoes(tty);
1126                         } else if (c == STOP_CHAR(tty))
1127                                 stop_tty(tty);
1128                 }
1129                 return;
1130         }
1131
1132         /*
1133          * If the previous character was LNEXT, or we know that this
1134          * character is not one of the characters that we'll have to
1135          * handle specially, do shortcut processing to speed things
1136          * up.
1137          */
1138         if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1139                 tty->lnext = 0;
1140                 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1141                 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1142                         /* beep if no space */
1143                         if (L_ECHO(tty))
1144                                 process_output('\a', tty);
1145                         return;
1146                 }
1147                 if (L_ECHO(tty)) {
1148                         finish_erasing(tty);
1149                         /* Record the column of first canon char. */
1150                         if (tty->canon_head == tty->read_head)
1151                                 echo_set_canon_col(tty);
1152                         echo_char(c, tty);
1153                         process_echoes(tty);
1154                 }
1155                 if (parmrk)
1156                         put_tty_queue(c, tty);
1157                 put_tty_queue(c, tty);
1158                 return;
1159         }
1160
1161         if (I_IXON(tty)) {
1162                 if (c == START_CHAR(tty)) {
1163                         start_tty(tty);
1164                         process_echoes(tty);
1165                         return;
1166                 }
1167                 if (c == STOP_CHAR(tty)) {
1168                         stop_tty(tty);
1169                         return;
1170                 }
1171         }
1172
1173         if (L_ISIG(tty)) {
1174                 int signal;
1175                 signal = SIGINT;
1176                 if (c == INTR_CHAR(tty))
1177                         goto send_signal;
1178                 signal = SIGQUIT;
1179                 if (c == QUIT_CHAR(tty))
1180                         goto send_signal;
1181                 signal = SIGTSTP;
1182                 if (c == SUSP_CHAR(tty)) {
1183 send_signal:
1184                         /*
1185                          * Note that we do not use isig() here because we want
1186                          * the order to be:
1187                          * 1) flush, 2) echo, 3) signal
1188                          */
1189                         if (!L_NOFLSH(tty)) {
1190                                 n_tty_flush_buffer(tty);
1191                                 tty_driver_flush_buffer(tty);
1192                         }
1193                         if (I_IXON(tty))
1194                                 start_tty(tty);
1195                         if (L_ECHO(tty)) {
1196                                 echo_char(c, tty);
1197                                 process_echoes(tty);
1198                         }
1199                         if (tty->pgrp)
1200                                 kill_pgrp(tty->pgrp, signal, 1);
1201                         return;
1202                 }
1203         }
1204
1205         if (c == '\r') {
1206                 if (I_IGNCR(tty))
1207                         return;
1208                 if (I_ICRNL(tty))
1209                         c = '\n';
1210         } else if (c == '\n' && I_INLCR(tty))
1211                 c = '\r';
1212
1213         if (tty->icanon) {
1214                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1215                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1216                         eraser(c, tty);
1217                         process_echoes(tty);
1218                         return;
1219                 }
1220                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1221                         tty->lnext = 1;
1222                         if (L_ECHO(tty)) {
1223                                 finish_erasing(tty);
1224                                 if (L_ECHOCTL(tty)) {
1225                                         echo_char_raw('^', tty);
1226                                         echo_char_raw('\b', tty);
1227                                         process_echoes(tty);
1228                                 }
1229                         }
1230                         return;
1231                 }
1232                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1233                     L_IEXTEN(tty)) {
1234                         unsigned long tail = tty->canon_head;
1235
1236                         finish_erasing(tty);
1237                         echo_char(c, tty);
1238                         echo_char_raw('\n', tty);
1239                         while (tail != tty->read_head) {
1240                                 echo_char(tty->read_buf[tail], tty);
1241                                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1242                         }
1243                         process_echoes(tty);
1244                         return;
1245                 }
1246                 if (c == '\n') {
1247                         if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1248                                 if (L_ECHO(tty))
1249                                         process_output('\a', tty);
1250                                 return;
1251                         }
1252                         if (L_ECHO(tty) || L_ECHONL(tty)) {
1253                                 echo_char_raw('\n', tty);
1254                                 process_echoes(tty);
1255                         }
1256                         goto handle_newline;
1257                 }
1258                 if (c == EOF_CHAR(tty)) {
1259                         if (tty->read_cnt >= N_TTY_BUF_SIZE)
1260                                 return;
1261                         if (tty->canon_head != tty->read_head)
1262                                 set_bit(TTY_PUSH, &tty->flags);
1263                         c = __DISABLED_CHAR;
1264                         goto handle_newline;
1265                 }
1266                 if ((c == EOL_CHAR(tty)) ||
1267                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1268                         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1269                                  ? 1 : 0;
1270                         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1271                                 if (L_ECHO(tty))
1272                                         process_output('\a', tty);
1273                                 return;
1274                         }
1275                         /*
1276                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1277                          */
1278                         if (L_ECHO(tty)) {
1279                                 /* Record the column of first canon char. */
1280                                 if (tty->canon_head == tty->read_head)
1281                                         echo_set_canon_col(tty);
1282                                 echo_char(c, tty);
1283                                 process_echoes(tty);
1284                         }
1285                         /*
1286                          * XXX does PARMRK doubling happen for
1287                          * EOL_CHAR and EOL2_CHAR?
1288                          */
1289                         if (parmrk)
1290                                 put_tty_queue(c, tty);
1291
1292 handle_newline:
1293                         spin_lock_irqsave(&tty->read_lock, flags);
1294                         set_bit(tty->read_head, tty->read_flags);
1295                         put_tty_queue_nolock(c, tty);
1296                         tty->canon_head = tty->read_head;
1297                         tty->canon_data++;
1298                         spin_unlock_irqrestore(&tty->read_lock, flags);
1299                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1300                         if (waitqueue_active(&tty->read_wait))
1301                                 wake_up_interruptible(&tty->read_wait);
1302                         return;
1303                 }
1304         }
1305
1306         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1307         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1308                 /* beep if no space */
1309                 if (L_ECHO(tty))
1310                         process_output('\a', tty);
1311                 return;
1312         }
1313         if (L_ECHO(tty)) {
1314                 finish_erasing(tty);
1315                 if (c == '\n')
1316                         echo_char_raw('\n', tty);
1317                 else {
1318                         /* Record the column of first canon char. */
1319                         if (tty->canon_head == tty->read_head)
1320                                 echo_set_canon_col(tty);
1321                         echo_char(c, tty);
1322                 }
1323                 process_echoes(tty);
1324         }
1325
1326         if (parmrk)
1327                 put_tty_queue(c, tty);
1328
1329         put_tty_queue(c, tty);
1330 }
1331
1332
1333 /**
1334  *      n_tty_write_wakeup      -       asynchronous I/O notifier
1335  *      @tty: tty device
1336  *
1337  *      Required for the ptys, serial driver etc. since processes
1338  *      that attach themselves to the master and rely on ASYNC
1339  *      IO must be woken up
1340  */
1341
1342 static void n_tty_write_wakeup(struct tty_struct *tty)
1343 {
1344         if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1345                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1346 }
1347
1348 /**
1349  *      n_tty_receive_buf       -       data receive
1350  *      @tty: terminal device
1351  *      @cp: buffer
1352  *      @fp: flag buffer
1353  *      @count: characters
1354  *
1355  *      Called by the terminal driver when a block of characters has
1356  *      been received. This function must be called from soft contexts
1357  *      not from interrupt context. The driver is responsible for making
1358  *      calls one at a time and in order (or using flush_to_ldisc)
1359  */
1360
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                 L_EXTPROC(tty)) {
1423                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1424                 if (waitqueue_active(&tty->read_wait))
1425                         wake_up_interruptible(&tty->read_wait);
1426         }
1427
1428         /*
1429          * Check the remaining room for the input canonicalization
1430          * mode.  We don't want to throttle the driver if we're in
1431          * canonical mode and don't have a newline yet!
1432          */
1433         if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1434                 tty_throttle(tty);
1435 }
1436
1437 int is_ignored(int sig)
1438 {
1439         return (sigismember(&current->blocked, sig) ||
1440                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1441 }
1442
1443 /**
1444  *      n_tty_set_termios       -       termios data changed
1445  *      @tty: terminal
1446  *      @old: previous data
1447  *
1448  *      Called by the tty layer when the user changes termios flags so
1449  *      that the line discipline can plan ahead. This function cannot sleep
1450  *      and is protected from re-entry by the tty layer. The user is
1451  *      guaranteed that this function will not be re-entered or in progress
1452  *      when the ldisc is closed.
1453  *
1454  *      Locking: Caller holds tty->termios_mutex
1455  */
1456
1457 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1458 {
1459         int canon_change = 1;
1460         BUG_ON(!tty);
1461
1462         if (old)
1463                 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1464         if (canon_change) {
1465                 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1466                 tty->canon_head = tty->read_tail;
1467                 tty->canon_data = 0;
1468                 tty->erasing = 0;
1469         }
1470
1471         if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1472                 wake_up_interruptible(&tty->read_wait);
1473
1474         tty->icanon = (L_ICANON(tty) != 0);
1475         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1476                 tty->raw = 1;
1477                 tty->real_raw = 1;
1478                 n_tty_set_room(tty);
1479                 return;
1480         }
1481         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1482             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1483             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1484             I_PARMRK(tty)) {
1485                 memset(tty->process_char_map, 0, 256/8);
1486
1487                 if (I_IGNCR(tty) || I_ICRNL(tty))
1488                         set_bit('\r', tty->process_char_map);
1489                 if (I_INLCR(tty))
1490                         set_bit('\n', tty->process_char_map);
1491
1492                 if (L_ICANON(tty)) {
1493                         set_bit(ERASE_CHAR(tty), tty->process_char_map);
1494                         set_bit(KILL_CHAR(tty), tty->process_char_map);
1495                         set_bit(EOF_CHAR(tty), tty->process_char_map);
1496                         set_bit('\n', tty->process_char_map);
1497                         set_bit(EOL_CHAR(tty), tty->process_char_map);
1498                         if (L_IEXTEN(tty)) {
1499                                 set_bit(WERASE_CHAR(tty),
1500                                         tty->process_char_map);
1501                                 set_bit(LNEXT_CHAR(tty),
1502                                         tty->process_char_map);
1503                                 set_bit(EOL2_CHAR(tty),
1504                                         tty->process_char_map);
1505                                 if (L_ECHO(tty))
1506                                         set_bit(REPRINT_CHAR(tty),
1507                                                 tty->process_char_map);
1508                         }
1509                 }
1510                 if (I_IXON(tty)) {
1511                         set_bit(START_CHAR(tty), tty->process_char_map);
1512                         set_bit(STOP_CHAR(tty), tty->process_char_map);
1513                 }
1514                 if (L_ISIG(tty)) {
1515                         set_bit(INTR_CHAR(tty), tty->process_char_map);
1516                         set_bit(QUIT_CHAR(tty), tty->process_char_map);
1517                         set_bit(SUSP_CHAR(tty), tty->process_char_map);
1518                 }
1519                 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1520                 tty->raw = 0;
1521                 tty->real_raw = 0;
1522         } else {
1523                 tty->raw = 1;
1524                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1525                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1526                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1527                         tty->real_raw = 1;
1528                 else
1529                         tty->real_raw = 0;
1530         }
1531         n_tty_set_room(tty);
1532         /* The termios change make the tty ready for I/O */
1533         wake_up_interruptible(&tty->write_wait);
1534         wake_up_interruptible(&tty->read_wait);
1535 }
1536
1537 /**
1538  *      n_tty_close             -       close the ldisc for this tty
1539  *      @tty: device
1540  *
1541  *      Called from the terminal layer when this line discipline is
1542  *      being shut down, either because of a close or becsuse of a
1543  *      discipline change. The function will not be called while other
1544  *      ldisc methods are in progress.
1545  */
1546
1547 static void n_tty_close(struct tty_struct *tty)
1548 {
1549         n_tty_flush_buffer(tty);
1550         if (tty->read_buf) {
1551                 kfree(tty->read_buf);
1552                 tty->read_buf = NULL;
1553         }
1554         if (tty->echo_buf) {
1555                 kfree(tty->echo_buf);
1556                 tty->echo_buf = NULL;
1557         }
1558 }
1559
1560 /**
1561  *      n_tty_open              -       open an ldisc
1562  *      @tty: terminal to open
1563  *
1564  *      Called when this line discipline is being attached to the
1565  *      terminal device. Can sleep. Called serialized so that no
1566  *      other events will occur in parallel. No further open will occur
1567  *      until a close.
1568  */
1569
1570 static int n_tty_open(struct tty_struct *tty)
1571 {
1572         if (!tty)
1573                 return -EINVAL;
1574
1575         /* These are ugly. Currently a malloc failure here can panic */
1576         if (!tty->read_buf) {
1577                 tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1578                 if (!tty->read_buf)
1579                         return -ENOMEM;
1580         }
1581         if (!tty->echo_buf) {
1582                 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1583
1584                 if (!tty->echo_buf)
1585                         return -ENOMEM;
1586         }
1587         reset_buffer_flags(tty);
1588         tty_unthrottle(tty);
1589         tty->column = 0;
1590         n_tty_set_termios(tty, NULL);
1591         tty->minimum_to_wake = 1;
1592         tty->closing = 0;
1593         return 0;
1594 }
1595
1596 static inline int input_available_p(struct tty_struct *tty, int amt)
1597 {
1598         tty_flush_to_ldisc(tty);
1599         if (tty->icanon && !L_EXTPROC(tty)) {
1600                 if (tty->canon_data)
1601                         return 1;
1602         } else if (tty->read_cnt >= (amt ? amt : 1))
1603                 return 1;
1604
1605         return 0;
1606 }
1607
1608 /**
1609  *      copy_from_read_buf      -       copy read data directly
1610  *      @tty: terminal device
1611  *      @b: user data
1612  *      @nr: size of data
1613  *
1614  *      Helper function to speed up n_tty_read.  It is only called when
1615  *      ICANON is off; it copies characters straight from the tty queue to
1616  *      user space directly.  It can be profitably called twice; once to
1617  *      drain the space from the tail pointer to the (physical) end of the
1618  *      buffer, and once to drain the space from the (physical) beginning of
1619  *      the buffer to head pointer.
1620  *
1621  *      Called under the tty->atomic_read_lock sem
1622  *
1623  */
1624
1625 static int copy_from_read_buf(struct tty_struct *tty,
1626                                       unsigned char __user **b,
1627                                       size_t *nr)
1628
1629 {
1630         int retval;
1631         size_t n;
1632         unsigned long flags;
1633
1634         retval = 0;
1635         spin_lock_irqsave(&tty->read_lock, flags);
1636         n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1637         n = min(*nr, n);
1638         spin_unlock_irqrestore(&tty->read_lock, flags);
1639         if (n) {
1640                 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1641                 n -= retval;
1642                 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1643                 spin_lock_irqsave(&tty->read_lock, flags);
1644                 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1645                 tty->read_cnt -= n;
1646                 /* Turn single EOF into zero-length read */
1647                 if (L_EXTPROC(tty) && tty->icanon && n == 1) {
1648                         if (!tty->read_cnt && (*b)[n-1] == EOF_CHAR(tty))
1649                                 n--;
1650                 }
1651                 spin_unlock_irqrestore(&tty->read_lock, flags);
1652                 *b += n;
1653                 *nr -= n;
1654         }
1655         return retval;
1656 }
1657
1658 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1659                                                         size_t, loff_t *);
1660
1661 /**
1662  *      job_control             -       check job control
1663  *      @tty: tty
1664  *      @file: file handle
1665  *
1666  *      Perform job control management checks on this file/tty descriptor
1667  *      and if appropriate send any needed signals and return a negative
1668  *      error code if action should be taken.
1669  *
1670  *      FIXME:
1671  *      Locking: None - redirected write test is safe, testing
1672  *      current->signal should possibly lock current->sighand
1673  *      pgrp locking ?
1674  */
1675
1676 static int job_control(struct tty_struct *tty, struct file *file)
1677 {
1678         /* Job control check -- must be done at start and after
1679            every sleep (POSIX.1 7.1.1.4). */
1680         /* NOTE: not yet done after every sleep pending a thorough
1681            check of the logic of this change. -- jlc */
1682         /* don't stop on /dev/console */
1683         if (file->f_op->write != redirected_tty_write &&
1684             current->signal->tty == tty) {
1685                 if (!tty->pgrp)
1686                         printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1687                 else if (task_pgrp(current) != tty->pgrp) {
1688                         if (is_ignored(SIGTTIN) ||
1689                             is_current_pgrp_orphaned())
1690                                 return -EIO;
1691                         kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1692                         set_thread_flag(TIF_SIGPENDING);
1693                         return -ERESTARTSYS;
1694                 }
1695         }
1696         return 0;
1697 }
1698
1699
1700 /**
1701  *      n_tty_read              -       read function for tty
1702  *      @tty: tty device
1703  *      @file: file object
1704  *      @buf: userspace buffer pointer
1705  *      @nr: size of I/O
1706  *
1707  *      Perform reads for the line discipline. We are guaranteed that the
1708  *      line discipline will not be closed under us but we may get multiple
1709  *      parallel readers and must handle this ourselves. We may also get
1710  *      a hangup. Always called in user context, may sleep.
1711  *
1712  *      This code must be sure never to sleep through a hangup.
1713  */
1714
1715 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1716                          unsigned char __user *buf, size_t nr)
1717 {
1718         unsigned char __user *b = buf;
1719         DECLARE_WAITQUEUE(wait, current);
1720         int c;
1721         int minimum, time;
1722         ssize_t retval = 0;
1723         ssize_t size;
1724         long timeout;
1725         unsigned long flags;
1726         int packet;
1727
1728 do_it_again:
1729
1730         BUG_ON(!tty->read_buf);
1731
1732         c = job_control(tty, file);
1733         if (c < 0)
1734                 return c;
1735
1736         minimum = time = 0;
1737         timeout = MAX_SCHEDULE_TIMEOUT;
1738         if (!tty->icanon) {
1739                 time = (HZ / 10) * TIME_CHAR(tty);
1740                 minimum = MIN_CHAR(tty);
1741                 if (minimum) {
1742                         if (time)
1743                                 tty->minimum_to_wake = 1;
1744                         else if (!waitqueue_active(&tty->read_wait) ||
1745                                  (tty->minimum_to_wake > minimum))
1746                                 tty->minimum_to_wake = minimum;
1747                 } else {
1748                         timeout = 0;
1749                         if (time) {
1750                                 timeout = time;
1751                                 time = 0;
1752                         }
1753                         tty->minimum_to_wake = minimum = 1;
1754                 }
1755         }
1756
1757         /*
1758          *      Internal serialization of reads.
1759          */
1760         if (file->f_flags & O_NONBLOCK) {
1761                 if (!mutex_trylock(&tty->atomic_read_lock))
1762                         return -EAGAIN;
1763         } else {
1764                 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1765                         return -ERESTARTSYS;
1766         }
1767         packet = tty->packet;
1768
1769         add_wait_queue(&tty->read_wait, &wait);
1770         while (nr) {
1771                 /* First test for status change. */
1772                 if (packet && tty->link->ctrl_status) {
1773                         unsigned char cs;
1774                         if (b != buf)
1775                                 break;
1776                         spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1777                         cs = tty->link->ctrl_status;
1778                         tty->link->ctrl_status = 0;
1779                         spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1780                         if (tty_put_user(tty, cs, b++)) {
1781                                 retval = -EFAULT;
1782                                 b--;
1783                                 break;
1784                         }
1785                         nr--;
1786                         break;
1787                 }
1788                 /* This statement must be first before checking for input
1789                    so that any interrupt will set the state back to
1790                    TASK_RUNNING. */
1791                 set_current_state(TASK_INTERRUPTIBLE);
1792
1793                 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1794                     ((minimum - (b - buf)) >= 1))
1795                         tty->minimum_to_wake = (minimum - (b - buf));
1796
1797                 if (!input_available_p(tty, 0)) {
1798                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1799                                 retval = -EIO;
1800                                 break;
1801                         }
1802                         if (tty_hung_up_p(file))
1803                                 break;
1804                         if (!timeout)
1805                                 break;
1806                         if (file->f_flags & O_NONBLOCK) {
1807                                 retval = -EAGAIN;
1808                                 break;
1809                         }
1810                         if (signal_pending(current)) {
1811                                 retval = -ERESTARTSYS;
1812                                 break;
1813                         }
1814                         /* FIXME: does n_tty_set_room need locking ? */
1815                         n_tty_set_room(tty);
1816                         timeout = schedule_timeout(timeout);
1817                         BUG_ON(!tty->read_buf);
1818                         continue;
1819                 }
1820                 __set_current_state(TASK_RUNNING);
1821
1822                 /* Deal with packet mode. */
1823                 if (packet && b == buf) {
1824                         if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1825                                 retval = -EFAULT;
1826                                 b--;
1827                                 break;
1828                         }
1829                         nr--;
1830                 }
1831
1832                 if (tty->icanon && !L_EXTPROC(tty)) {
1833                         /* N.B. avoid overrun if nr == 0 */
1834                         while (nr && tty->read_cnt) {
1835                                 int eol;
1836
1837                                 eol = test_and_clear_bit(tty->read_tail,
1838                                                 tty->read_flags);
1839                                 c = tty->read_buf[tty->read_tail];
1840                                 spin_lock_irqsave(&tty->read_lock, flags);
1841                                 tty->read_tail = ((tty->read_tail+1) &
1842                                                   (N_TTY_BUF_SIZE-1));
1843                                 tty->read_cnt--;
1844                                 if (eol) {
1845                                         /* this test should be redundant:
1846                                          * we shouldn't be reading data if
1847                                          * canon_data is 0
1848                                          */
1849                                         if (--tty->canon_data < 0)
1850                                                 tty->canon_data = 0;
1851                                 }
1852                                 spin_unlock_irqrestore(&tty->read_lock, flags);
1853
1854                                 if (!eol || (c != __DISABLED_CHAR)) {
1855                                         if (tty_put_user(tty, c, b++)) {
1856                                                 retval = -EFAULT;
1857                                                 b--;
1858                                                 break;
1859                                         }
1860                                         nr--;
1861                                 }
1862                                 if (eol) {
1863                                         tty_audit_push(tty);
1864                                         break;
1865                                 }
1866                         }
1867                         if (retval)
1868                                 break;
1869                 } else {
1870                         int uncopied;
1871                         /* The copy function takes the read lock and handles
1872                            locking internally for this case */
1873                         uncopied = copy_from_read_buf(tty, &b, &nr);
1874                         uncopied += copy_from_read_buf(tty, &b, &nr);
1875                         if (uncopied) {
1876                                 retval = -EFAULT;
1877                                 break;
1878                         }
1879                 }
1880
1881                 /* If there is enough space in the read buffer now, let the
1882                  * low-level driver know. We use n_tty_chars_in_buffer() to
1883                  * check the buffer, as it now knows about canonical mode.
1884                  * Otherwise, if the driver is throttled and the line is
1885                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1886                  * we won't get any more characters.
1887                  */
1888                 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1889                         n_tty_set_room(tty);
1890                         check_unthrottle(tty);
1891                 }
1892
1893                 if (b - buf >= minimum)
1894                         break;
1895                 if (time)
1896                         timeout = time;
1897         }
1898         mutex_unlock(&tty->atomic_read_lock);
1899         remove_wait_queue(&tty->read_wait, &wait);
1900
1901         if (!waitqueue_active(&tty->read_wait))
1902                 tty->minimum_to_wake = minimum;
1903
1904         __set_current_state(TASK_RUNNING);
1905         size = b - buf;
1906         if (size) {
1907                 retval = size;
1908                 if (nr)
1909                         clear_bit(TTY_PUSH, &tty->flags);
1910         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1911                 goto do_it_again;
1912
1913         n_tty_set_room(tty);
1914         return retval;
1915 }
1916
1917 /**
1918  *      n_tty_write             -       write function for tty
1919  *      @tty: tty device
1920  *      @file: file object
1921  *      @buf: userspace buffer pointer
1922  *      @nr: size of I/O
1923  *
1924  *      Write function of the terminal device.  This is serialized with
1925  *      respect to other write callers but not to termios changes, reads
1926  *      and other such events.  Since the receive code will echo characters,
1927  *      thus calling driver write methods, the output_lock is used in
1928  *      the output processing functions called here as well as in the
1929  *      echo processing function to protect the column state and space
1930  *      left in the buffer.
1931  *
1932  *      This code must be sure never to sleep through a hangup.
1933  *
1934  *      Locking: output_lock to protect column state and space left
1935  *               (note that the process_output*() functions take this
1936  *                lock themselves)
1937  */
1938
1939 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1940                            const unsigned char *buf, size_t nr)
1941 {
1942         const unsigned char *b = buf;
1943         DECLARE_WAITQUEUE(wait, current);
1944         int c;
1945         ssize_t retval = 0;
1946
1947         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1948         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1949                 retval = tty_check_change(tty);
1950                 if (retval)
1951                         return retval;
1952         }
1953
1954         /* Write out any echoed characters that are still pending */
1955         process_echoes(tty);
1956
1957         add_wait_queue(&tty->write_wait, &wait);
1958         while (1) {
1959                 set_current_state(TASK_INTERRUPTIBLE);
1960                 if (signal_pending(current)) {
1961                         retval = -ERESTARTSYS;
1962                         break;
1963                 }
1964                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1965                         retval = -EIO;
1966                         break;
1967                 }
1968                 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1969                         while (nr > 0) {
1970                                 ssize_t num = process_output_block(tty, b, nr);
1971                                 if (num < 0) {
1972                                         if (num == -EAGAIN)
1973                                                 break;
1974                                         retval = num;
1975                                         goto break_out;
1976                                 }
1977                                 b += num;
1978                                 nr -= num;
1979                                 if (nr == 0)
1980                                         break;
1981                                 c = *b;
1982                                 if (process_output(c, tty) < 0)
1983                                         break;
1984                                 b++; nr--;
1985                         }
1986                         if (tty->ops->flush_chars)
1987                                 tty->ops->flush_chars(tty);
1988                 } else {
1989                         while (nr > 0) {
1990                                 c = tty->ops->write(tty, b, nr);
1991                                 if (c < 0) {
1992                                         retval = c;
1993                                         goto break_out;
1994                                 }
1995                                 if (!c)
1996                                         break;
1997                                 b += c;
1998                                 nr -= c;
1999                         }
2000                 }
2001                 if (!nr)
2002                         break;
2003                 if (file->f_flags & O_NONBLOCK) {
2004                         retval = -EAGAIN;
2005                         break;
2006                 }
2007                 schedule();
2008         }
2009 break_out:
2010         __set_current_state(TASK_RUNNING);
2011         remove_wait_queue(&tty->write_wait, &wait);
2012         if (b - buf != nr && tty->fasync)
2013                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2014         return (b - buf) ? b - buf : retval;
2015 }
2016
2017 /**
2018  *      n_tty_poll              -       poll method for N_TTY
2019  *      @tty: terminal device
2020  *      @file: file accessing it
2021  *      @wait: poll table
2022  *
2023  *      Called when the line discipline is asked to poll() for data or
2024  *      for special events. This code is not serialized with respect to
2025  *      other events save open/close.
2026  *
2027  *      This code must be sure never to sleep through a hangup.
2028  *      Called without the kernel lock held - fine
2029  */
2030
2031 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2032                                                         poll_table *wait)
2033 {
2034         unsigned int mask = 0;
2035
2036         poll_wait(file, &tty->read_wait, wait);
2037         poll_wait(file, &tty->write_wait, wait);
2038         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2039                 mask |= POLLIN | POLLRDNORM;
2040         if (tty->packet && tty->link->ctrl_status)
2041                 mask |= POLLPRI | POLLIN | POLLRDNORM;
2042         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2043                 mask |= POLLHUP;
2044         if (tty_hung_up_p(file))
2045                 mask |= POLLHUP;
2046         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2047                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2048                         tty->minimum_to_wake = MIN_CHAR(tty);
2049                 else
2050                         tty->minimum_to_wake = 1;
2051         }
2052         if (tty->ops->write && !tty_is_writelocked(tty) &&
2053                         tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2054                         tty_write_room(tty) > 0)
2055                 mask |= POLLOUT | POLLWRNORM;
2056         return mask;
2057 }
2058
2059 static unsigned long inq_canon(struct tty_struct *tty)
2060 {
2061         int nr, head, tail;
2062
2063         if (!tty->canon_data)
2064                 return 0;
2065         head = tty->canon_head;
2066         tail = tty->read_tail;
2067         nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2068         /* Skip EOF-chars.. */
2069         while (head != tail) {
2070                 if (test_bit(tail, tty->read_flags) &&
2071                     tty->read_buf[tail] == __DISABLED_CHAR)
2072                         nr--;
2073                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2074         }
2075         return nr;
2076 }
2077
2078 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2079                        unsigned int cmd, unsigned long arg)
2080 {
2081         int retval;
2082
2083         switch (cmd) {
2084         case TIOCOUTQ:
2085                 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2086         case TIOCINQ:
2087                 /* FIXME: Locking */
2088                 retval = tty->read_cnt;
2089                 if (L_ICANON(tty))
2090                         retval = inq_canon(tty);
2091                 return put_user(retval, (unsigned int __user *) arg);
2092         default:
2093                 return n_tty_ioctl_helper(tty, file, cmd, arg);
2094         }
2095 }
2096
2097 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2098         .magic           = TTY_LDISC_MAGIC,
2099         .name            = "n_tty",
2100         .open            = n_tty_open,
2101         .close           = n_tty_close,
2102         .flush_buffer    = n_tty_flush_buffer,
2103         .chars_in_buffer = n_tty_chars_in_buffer,
2104         .read            = n_tty_read,
2105         .write           = n_tty_write,
2106         .ioctl           = n_tty_ioctl,
2107         .set_termios     = n_tty_set_termios,
2108         .poll            = n_tty_poll,
2109         .receive_buf     = n_tty_receive_buf,
2110         .write_wakeup    = n_tty_write_wakeup
2111 };
2112
2113 /**
2114  *      n_tty_inherit_ops       -       inherit N_TTY methods
2115  *      @ops: struct tty_ldisc_ops where to save N_TTY methods
2116  *
2117  *      Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
2118  *      methods.
2119  */
2120
2121 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2122 {
2123         *ops = tty_ldisc_N_TTY;
2124         ops->owner = NULL;
2125         ops->refcount = ops->flags = 0;
2126 }
2127 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);