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 #include <linux/ratelimit.h>
  53
  54
  55 /* number of characters left in xmit buffer before select has we have room */
  56 #define WAKEUP_CHARS 256
  57
  58 /*
  59  * This defines the low- and high-watermarks for throttling and
  60  * unthrottling the TTY driver.  These watermarks are used for
  61  * controlling the space in the read buffer.
  62  */
  63 #define TTY_THRESHOLD_THROTTLE          128 /* now based on remaining room */
  64 #define TTY_THRESHOLD_UNTHROTTLE        128
  65
  66 /*
  67  * Special byte codes used in the echo buffer to represent operations
  68  * or special handling of characters.  Bytes in the echo buffer that
  69  * are not part of such special blocks are treated as normal character
  70  * codes.
  71  */
  72 #define ECHO_OP_START 0xff
  73 #define ECHO_OP_MOVE_BACK_COL 0x80
  74 #define ECHO_OP_SET_CANON_COL 0x81
  75 #define ECHO_OP_ERASE_TAB 0x82
  76
  77 #define ECHO_COMMIT_WATERMARK   256
  78 #define ECHO_BLOCK              256
  79 #define ECHO_DISCARD_WATERMARK  N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
  80
  81
  82 #undef N_TTY_TRACE
  83 #ifdef N_TTY_TRACE
  84 # define n_tty_trace(f, args...)        trace_printk(f, ##args)
  85 #else
  86 # define n_tty_trace(f, args...)
  87 #endif
  88
  89 struct n_tty_data {
  90         /* producer-published */
  91         size_t read_head;
  92         size_t canon_head;
  93         size_t echo_head;
  94         size_t echo_commit;
  95         DECLARE_BITMAP(process_char_map, 256);
  96
  97         /* private to n_tty_receive_overrun (single-threaded) */
  98         unsigned long overrun_time;
  99         int num_overrun;
 100
 101         /* non-atomic */
 102         bool no_room;
 103
 104         /* must hold exclusive termios_rwsem to reset these */
 105         unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
 106
 107         /* shared by producer and consumer */
 108         char read_buf[N_TTY_BUF_SIZE];
 109         DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
 110         unsigned char echo_buf[N_TTY_BUF_SIZE];
 111
 112         int minimum_to_wake;
 113
 114         /* consumer-published */
 115         size_t read_tail;
 116         size_t line_start;
 117
 118         /* protected by output lock */
 119         unsigned int column;
 120         unsigned int canon_column;
 121         size_t echo_tail;
 122
 123         struct mutex atomic_read_lock;
 124         struct mutex output_lock;
 125 };
 126
 127 static inline size_t read_cnt(struct n_tty_data *ldata)
 128 {
 129         return ldata->read_head - ldata->read_tail;
 130 }
 131
 132 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
 133 {
 134         return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
 135 }
 136
 137 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
 138 {
 139         return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
 140 }
 141
 142 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
 143 {
 144         return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
 145 }
 146
 147 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
 148 {
 149         return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
 150 }
 151
 152 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
 153                                unsigned char __user *ptr)
 154 {
 155         struct n_tty_data *ldata = tty->disc_data;
 156
 157         tty_audit_add_data(tty, &x, 1, ldata->icanon);
 158         return put_user(x, ptr);
 159 }
 160
 161 static int receive_room(struct tty_struct *tty)
 162 {
 163         struct n_tty_data *ldata = tty->disc_data;
 164         int left;
 165
 166         if (I_PARMRK(tty)) {
 167                 /* Multiply read_cnt by 3, since each byte might take up to
 168                  * three times as many spaces when PARMRK is set (depending on
 169                  * its flags, e.g. parity error). */
 170                 left = N_TTY_BUF_SIZE - read_cnt(ldata) * 3 - 1;
 171         } else
 172                 left = N_TTY_BUF_SIZE - read_cnt(ldata) - 1;
 173
 174         /*
 175          * If we are doing input canonicalization, and there are no
 176          * pending newlines, let characters through without limit, so
 177          * that erase characters will be handled.  Other excess
 178          * characters will be beeped.
 179          */
 180         if (left <= 0)
 181                 left = ldata->icanon && ldata->canon_head == ldata->read_tail;
 182
 183         return left;
 184 }
 185
 186 /**
 187  *      n_tty_set_room  -       receive space
 188  *      @tty: terminal
 189  *
 190  *      Re-schedules the flip buffer work if space just became available.
 191  *
 192  *      Caller holds exclusive termios_rwsem
 193  *         or
 194  *      n_tty_read()/consumer path:
 195  *              holds non-exclusive termios_rwsem
 196  */
 197
 198 static void n_tty_set_room(struct tty_struct *tty)
 199 {
 200         struct n_tty_data *ldata = tty->disc_data;
 201
 202         /* Did this open up the receive buffer? We may need to flip */
 203         if (unlikely(ldata->no_room) && receive_room(tty)) {
 204                 ldata->no_room = 0;
 205
 206                 WARN_RATELIMIT(tty->port->itty == NULL,
 207                                 "scheduling with invalid itty\n");
 208                 /* see if ldisc has been killed - if so, this means that
 209                  * even though the ldisc has been halted and ->buf.work
 210                  * cancelled, ->buf.work is about to be rescheduled
 211                  */
 212                 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
 213                                "scheduling buffer work for halted ldisc\n");
 214                 queue_work(system_unbound_wq, &tty->port->buf.work);
 215         }
 216 }
 217
 218 static ssize_t chars_in_buffer(struct tty_struct *tty)
 219 {
 220         struct n_tty_data *ldata = tty->disc_data;
 221         ssize_t n = 0;
 222
 223         if (!ldata->icanon)
 224                 n = read_cnt(ldata);
 225         else
 226                 n = ldata->canon_head - ldata->read_tail;
 227         return n;
 228 }
 229
 230 /**
 231  *      n_tty_write_wakeup      -       asynchronous I/O notifier
 232  *      @tty: tty device
 233  *
 234  *      Required for the ptys, serial driver etc. since processes
 235  *      that attach themselves to the master and rely on ASYNC
 236  *      IO must be woken up
 237  */
 238
 239 static void n_tty_write_wakeup(struct tty_struct *tty)
 240 {
 241         if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
 242                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
 243 }
 244
 245 static inline void n_tty_check_throttle(struct tty_struct *tty)
 246 {
 247         if (tty->driver->type == TTY_DRIVER_TYPE_PTY)
 248                 return;
 249         /*
 250          * Check the remaining room for the input canonicalization
 251          * mode.  We don't want to throttle the driver if we're in
 252          * canonical mode and don't have a newline yet!
 253          */
 254         while (1) {
 255                 int throttled;
 256                 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
 257                 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
 258                         break;
 259                 throttled = tty_throttle_safe(tty);
 260                 if (!throttled)
 261                         break;
 262         }
 263         __tty_set_flow_change(tty, 0);
 264 }
 265
 266 static inline void n_tty_check_unthrottle(struct tty_struct *tty)
 267 {
 268         if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
 269             tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
 270                 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
 271                         return;
 272                 if (!tty->count)
 273                         return;
 274                 n_tty_set_room(tty);
 275                 n_tty_write_wakeup(tty->link);
 276                 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
 277                 return;
 278         }
 279
 280         /* If there is enough space in the read buffer now, let the
 281          * low-level driver know. We use chars_in_buffer() to
 282          * check the buffer, as it now knows about canonical mode.
 283          * Otherwise, if the driver is throttled and the line is
 284          * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
 285          * we won't get any more characters.
 286          */
 287
 288         while (1) {
 289                 int unthrottled;
 290                 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
 291                 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
 292                         break;
 293                 if (!tty->count)
 294                         break;
 295                 n_tty_set_room(tty);
 296                 unthrottled = tty_unthrottle_safe(tty);
 297                 if (!unthrottled)
 298                         break;
 299         }
 300         __tty_set_flow_change(tty, 0);
 301 }
 302
 303 /**
 304  *      put_tty_queue           -       add character to tty
 305  *      @c: character
 306  *      @ldata: n_tty data
 307  *
 308  *      Add a character to the tty read_buf queue.
 309  *
 310  *      n_tty_receive_buf()/producer path:
 311  *              caller holds non-exclusive termios_rwsem
 312  *              modifies read_head
 313  *
 314  *      read_head is only considered 'published' if canonical mode is
 315  *      not active.
 316  */
 317
 318 static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
 319 {
 320         if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
 321                 *read_buf_addr(ldata, ldata->read_head) = c;
 322                 ldata->read_head++;
 323         }
 324 }
 325
 326 /**
 327  *      reset_buffer_flags      -       reset buffer state
 328  *      @tty: terminal to reset
 329  *
 330  *      Reset the read buffer counters and clear the flags.
 331  *      Called from n_tty_open() and n_tty_flush_buffer().
 332  *
 333  *      Locking: caller holds exclusive termios_rwsem
 334  *               (or locking is not required)
 335  */
 336
 337 static void reset_buffer_flags(struct n_tty_data *ldata)
 338 {
 339         ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
 340         ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
 341         ldata->line_start = 0;
 342
 343         ldata->erasing = 0;
 344         bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
 345 }
 346
 347 static void n_tty_packet_mode_flush(struct tty_struct *tty)
 348 {
 349         unsigned long flags;
 350
 351         spin_lock_irqsave(&tty->ctrl_lock, flags);
 352         if (tty->link->packet) {
 353                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
 354                 wake_up_interruptible(&tty->link->read_wait);
 355         }
 356         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 357 }
 358
 359 /**
 360  *      n_tty_flush_buffer      -       clean input queue
 361  *      @tty:   terminal device
 362  *
 363  *      Flush the input buffer. Called when the tty layer wants the
 364  *      buffer flushed (eg at hangup) or when the N_TTY line discipline
 365  *      internally has to clean the pending queue (for example some signals).
 366  *
 367  *      Holds termios_rwsem to exclude producer/consumer while
 368  *      buffer indices are reset.
 369  *
 370  *      Locking: ctrl_lock, exclusive termios_rwsem
 371  */
 372
 373 static void n_tty_flush_buffer(struct tty_struct *tty)
 374 {
 375         down_write(&tty->termios_rwsem);
 376         reset_buffer_flags(tty->disc_data);
 377         n_tty_set_room(tty);
 378
 379         if (tty->link)
 380                 n_tty_packet_mode_flush(tty);
 381         up_write(&tty->termios_rwsem);
 382 }
 383
 384 /**
 385  *      n_tty_chars_in_buffer   -       report available bytes
 386  *      @tty: tty device
 387  *
 388  *      Report the number of characters buffered to be delivered to user
 389  *      at this instant in time.
 390  *
 391  *      Locking: exclusive termios_rwsem
 392  */
 393
 394 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
 395 {
 396         ssize_t n;
 397
 398         WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
 399
 400         down_write(&tty->termios_rwsem);
 401         n = chars_in_buffer(tty);
 402         up_write(&tty->termios_rwsem);
 403         return n;
 404 }
 405
 406 /**
 407  *      is_utf8_continuation    -       utf8 multibyte check
 408  *      @c: byte to check
 409  *
 410  *      Returns true if the utf8 character 'c' is a multibyte continuation
 411  *      character. We use this to correctly compute the on screen size
 412  *      of the character when printing
 413  */
 414
 415 static inline int is_utf8_continuation(unsigned char c)
 416 {
 417         return (c & 0xc0) == 0x80;
 418 }
 419
 420 /**
 421  *      is_continuation         -       multibyte check
 422  *      @c: byte to check
 423  *
 424  *      Returns true if the utf8 character 'c' is a multibyte continuation
 425  *      character and the terminal is in unicode mode.
 426  */
 427
 428 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
 429 {
 430         return I_IUTF8(tty) && is_utf8_continuation(c);
 431 }
 432
 433 /**
 434  *      do_output_char                  -       output one character
 435  *      @c: character (or partial unicode symbol)
 436  *      @tty: terminal device
 437  *      @space: space available in tty driver write buffer
 438  *
 439  *      This is a helper function that handles one output character
 440  *      (including special characters like TAB, CR, LF, etc.),
 441  *      doing OPOST processing and putting the results in the
 442  *      tty driver's write buffer.
 443  *
 444  *      Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
 445  *      and NLDLY.  They simply aren't relevant in the world today.
 446  *      If you ever need them, add them here.
 447  *
 448  *      Returns the number of bytes of buffer space used or -1 if
 449  *      no space left.
 450  *
 451  *      Locking: should be called under the output_lock to protect
 452  *               the column state and space left in the buffer
 453  */
 454
 455 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
 456 {
 457         struct n_tty_data *ldata = tty->disc_data;
 458         int     spaces;
 459
 460         if (!space)
 461                 return -1;
 462
 463         switch (c) {
 464         case '\n':
 465                 if (O_ONLRET(tty))
 466                         ldata->column = 0;
 467                 if (O_ONLCR(tty)) {
 468                         if (space < 2)
 469                                 return -1;
 470                         ldata->canon_column = ldata->column = 0;
 471                         tty->ops->write(tty, "\r\n", 2);
 472                         return 2;
 473                 }
 474                 ldata->canon_column = ldata->column;
 475                 break;
 476         case '\r':
 477                 if (O_ONOCR(tty) && ldata->column == 0)
 478                         return 0;
 479                 if (O_OCRNL(tty)) {
 480                         c = '\n';
 481                         if (O_ONLRET(tty))
 482                                 ldata->canon_column = ldata->column = 0;
 483                         break;
 484                 }
 485                 ldata->canon_column = ldata->column = 0;
 486                 break;
 487         case '\t':
 488                 spaces = 8 - (ldata->column & 7);
 489                 if (O_TABDLY(tty) == XTABS) {
 490                         if (space < spaces)
 491                                 return -1;
 492                         ldata->column += spaces;
 493                         tty->ops->write(tty, "        ", spaces);
 494                         return spaces;
 495                 }
 496                 ldata->column += spaces;
 497                 break;
 498         case '\b':
 499                 if (ldata->column > 0)
 500                         ldata->column--;
 501                 break;
 502         default:
 503                 if (!iscntrl(c)) {
 504                         if (O_OLCUC(tty))
 505                                 c = toupper(c);
 506                         if (!is_continuation(c, tty))
 507                                 ldata->column++;
 508                 }
 509                 break;
 510         }
 511
 512         tty_put_char(tty, c);
 513         return 1;
 514 }
 515
 516 /**
 517  *      process_output                  -       output post processor
 518  *      @c: character (or partial unicode symbol)
 519  *      @tty: terminal device
 520  *
 521  *      Output one character with OPOST processing.
 522  *      Returns -1 when the output device is full and the character
 523  *      must be retried.
 524  *
 525  *      Locking: output_lock to protect column state and space left
 526  *               (also, this is called from n_tty_write under the
 527  *                tty layer write lock)
 528  */
 529
 530 static int process_output(unsigned char c, struct tty_struct *tty)
 531 {
 532         struct n_tty_data *ldata = tty->disc_data;
 533         int     space, retval;
 534
 535         mutex_lock(&ldata->output_lock);
 536
 537         space = tty_write_room(tty);
 538         retval = do_output_char(c, tty, space);
 539
 540         mutex_unlock(&ldata->output_lock);
 541         if (retval < 0)
 542                 return -1;
 543         else
 544                 return 0;
 545 }
 546
 547 /**
 548  *      process_output_block            -       block post processor
 549  *      @tty: terminal device
 550  *      @buf: character buffer
 551  *      @nr: number of bytes to output
 552  *
 553  *      Output a block of characters with OPOST processing.
 554  *      Returns the number of characters output.
 555  *
 556  *      This path is used to speed up block console writes, among other
 557  *      things when processing blocks of output data. It handles only
 558  *      the simple cases normally found and helps to generate blocks of
 559  *      symbols for the console driver and thus improve performance.
 560  *
 561  *      Locking: output_lock to protect column state and space left
 562  *               (also, this is called from n_tty_write under the
 563  *                tty layer write lock)
 564  */
 565
 566 static ssize_t process_output_block(struct tty_struct *tty,
 567                                     const unsigned char *buf, unsigned int nr)
 568 {
 569         struct n_tty_data *ldata = tty->disc_data;
 570         int     space;
 571         int     i;
 572         const unsigned char *cp;
 573
 574         mutex_lock(&ldata->output_lock);
 575
 576         space = tty_write_room(tty);
 577         if (!space) {
 578                 mutex_unlock(&ldata->output_lock);
 579                 return 0;
 580         }
 581         if (nr > space)
 582                 nr = space;
 583
 584         for (i = 0, cp = buf; i < nr; i++, cp++) {
 585                 unsigned char c = *cp;
 586
 587                 switch (c) {
 588                 case '\n':
 589                         if (O_ONLRET(tty))
 590                                 ldata->column = 0;
 591                         if (O_ONLCR(tty))
 592                                 goto break_out;
 593                         ldata->canon_column = ldata->column;
 594                         break;
 595                 case '\r':
 596                         if (O_ONOCR(tty) && ldata->column == 0)
 597                                 goto break_out;
 598                         if (O_OCRNL(tty))
 599                                 goto break_out;
 600                         ldata->canon_column = ldata->column = 0;
 601                         break;
 602                 case '\t':
 603                         goto break_out;
 604                 case '\b':
 605                         if (ldata->column > 0)
 606                                 ldata->column--;
 607                         break;
 608                 default:
 609                         if (!iscntrl(c)) {
 610                                 if (O_OLCUC(tty))
 611                                         goto break_out;
 612                                 if (!is_continuation(c, tty))
 613                                         ldata->column++;
 614                         }
 615                         break;
 616                 }
 617         }
 618 break_out:
 619         i = tty->ops->write(tty, buf, i);
 620
 621         mutex_unlock(&ldata->output_lock);
 622         return i;
 623 }
 624
 625 /**
 626  *      process_echoes  -       write pending echo characters
 627  *      @tty: terminal device
 628  *
 629  *      Write previously buffered echo (and other ldisc-generated)
 630  *      characters to the tty.
 631  *
 632  *      Characters generated by the ldisc (including echoes) need to
 633  *      be buffered because the driver's write buffer can fill during
 634  *      heavy program output.  Echoing straight to the driver will
 635  *      often fail under these conditions, causing lost characters and
 636  *      resulting mismatches of ldisc state information.
 637  *
 638  *      Since the ldisc state must represent the characters actually sent
 639  *      to the driver at the time of the write, operations like certain
 640  *      changes in column state are also saved in the buffer and executed
 641  *      here.
 642  *
 643  *      A circular fifo buffer is used so that the most recent characters
 644  *      are prioritized.  Also, when control characters are echoed with a
 645  *      prefixed "^", the pair is treated atomically and thus not separated.
 646  *
 647  *      Locking: callers must hold output_lock
 648  */
 649
 650 static size_t __process_echoes(struct tty_struct *tty)
 651 {
 652         struct n_tty_data *ldata = tty->disc_data;
 653         int     space, old_space;
 654         size_t tail;
 655         unsigned char c;
 656
 657         old_space = space = tty_write_room(tty);
 658
 659         tail = ldata->echo_tail;
 660         while (ldata->echo_commit != tail) {
 661                 c = echo_buf(ldata, tail);
 662                 if (c == ECHO_OP_START) {
 663                         unsigned char op;
 664                         int no_space_left = 0;
 665
 666                         /*
 667                          * If the buffer byte is the start of a multi-byte
 668                          * operation, get the next byte, which is either the
 669                          * op code or a control character value.
 670                          */
 671                         op = echo_buf(ldata, tail + 1);
 672
 673                         switch (op) {
 674                                 unsigned int num_chars, num_bs;
 675
 676                         case ECHO_OP_ERASE_TAB:
 677                                 num_chars = echo_buf(ldata, tail + 2);
 678
 679                                 /*
 680                                  * Determine how many columns to go back
 681                                  * in order to erase the tab.
 682                                  * This depends on the number of columns
 683                                  * used by other characters within the tab
 684                                  * area.  If this (modulo 8) count is from
 685                                  * the start of input rather than from a
 686                                  * previous tab, we offset by canon column.
 687                                  * Otherwise, tab spacing is normal.
 688                                  */
 689                                 if (!(num_chars & 0x80))
 690                                         num_chars += ldata->canon_column;
 691                                 num_bs = 8 - (num_chars & 7);
 692
 693                                 if (num_bs > space) {
 694                                         no_space_left = 1;
 695                                         break;
 696                                 }
 697                                 space -= num_bs;
 698                                 while (num_bs--) {
 699                                         tty_put_char(tty, '\b');
 700                                         if (ldata->column > 0)
 701                                                 ldata->column--;
 702                                 }
 703                                 tail += 3;
 704                                 break;
 705
 706                         case ECHO_OP_SET_CANON_COL:
 707                                 ldata->canon_column = ldata->column;
 708                                 tail += 2;
 709                                 break;
 710
 711                         case ECHO_OP_MOVE_BACK_COL:
 712                                 if (ldata->column > 0)
 713                                         ldata->column--;
 714                                 tail += 2;
 715                                 break;
 716
 717                         case ECHO_OP_START:
 718                                 /* This is an escaped echo op start code */
 719                                 if (!space) {
 720                                         no_space_left = 1;
 721                                         break;
 722                                 }
 723                                 tty_put_char(tty, ECHO_OP_START);
 724                                 ldata->column++;
 725                                 space--;
 726                                 tail += 2;
 727                                 break;
 728
 729                         default:
 730                                 /*
 731                                  * If the op is not a special byte code,
 732                                  * it is a ctrl char tagged to be echoed
 733                                  * as "^X" (where X is the letter
 734                                  * representing the control char).
 735                                  * Note that we must ensure there is
 736                                  * enough space for the whole ctrl pair.
 737                                  *
 738                                  */
 739                                 if (space < 2) {
 740                                         no_space_left = 1;
 741                                         break;
 742                                 }
 743                                 tty_put_char(tty, '^');
 744                                 tty_put_char(tty, op ^ 0100);
 745                                 ldata->column += 2;
 746                                 space -= 2;
 747                                 tail += 2;
 748                         }
 749
 750                         if (no_space_left)
 751                                 break;
 752                 } else {
 753                         if (O_OPOST(tty)) {
 754                                 int retval = do_output_char(c, tty, space);
 755                                 if (retval < 0)
 756                                         break;
 757                                 space -= retval;
 758                         } else {
 759                                 if (!space)
 760                                         break;
 761                                 tty_put_char(tty, c);
 762                                 space -= 1;
 763                         }
 764                         tail += 1;
 765                 }
 766         }
 767
 768         /* If the echo buffer is nearly full (so that the possibility exists
 769          * of echo overrun before the next commit), then discard enough
 770          * data at the tail to prevent a subsequent overrun */
 771         while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
 772                 if (echo_buf(ldata, tail == ECHO_OP_START)) {
 773                         if (echo_buf(ldata, tail) == ECHO_OP_ERASE_TAB)
 774                                 tail += 3;
 775                         else
 776                                 tail += 2;
 777                 } else
 778                         tail++;
 779         }
 780
 781         ldata->echo_tail = tail;
 782         return old_space - space;
 783 }
 784
 785 static void commit_echoes(struct tty_struct *tty)
 786 {
 787         struct n_tty_data *ldata = tty->disc_data;
 788         size_t nr, old, echoed;
 789         size_t head;
 790
 791         head = ldata->echo_head;
 792         old = ldata->echo_commit - ldata->echo_tail;
 793
 794         /* Process committed echoes if the accumulated # of bytes
 795          * is over the threshold (and try again each time another
 796          * block is accumulated) */
 797         nr = head - ldata->echo_tail;
 798         if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
 799                 return;
 800
 801         mutex_lock(&ldata->output_lock);
 802         ldata->echo_commit = head;
 803         echoed = __process_echoes(tty);
 804         mutex_unlock(&ldata->output_lock);
 805
 806         if (echoed && tty->ops->flush_chars)
 807                 tty->ops->flush_chars(tty);
 808 }
 809
 810 static void process_echoes(struct tty_struct *tty)
 811 {
 812         struct n_tty_data *ldata = tty->disc_data;
 813         size_t echoed;
 814
 815         if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_tail)
 816                 return;
 817
 818         mutex_lock(&ldata->output_lock);
 819         echoed = __process_echoes(tty);
 820         mutex_unlock(&ldata->output_lock);
 821
 822         if (echoed && tty->ops->flush_chars)
 823                 tty->ops->flush_chars(tty);
 824 }
 825
 826 static void flush_echoes(struct tty_struct *tty)
 827 {
 828         struct n_tty_data *ldata = tty->disc_data;
 829
 830         if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_head)
 831                 return;
 832
 833         mutex_lock(&ldata->output_lock);
 834         ldata->echo_commit = ldata->echo_head;
 835         __process_echoes(tty);
 836         mutex_unlock(&ldata->output_lock);
 837 }
 838
 839 /**
 840  *      add_echo_byte   -       add a byte to the echo buffer
 841  *      @c: unicode byte to echo
 842  *      @ldata: n_tty data
 843  *
 844  *      Add a character or operation byte to the echo buffer.
 845  */
 846
 847 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
 848 {
 849         *echo_buf_addr(ldata, ldata->echo_head++) = c;
 850 }
 851
 852 /**
 853  *      echo_move_back_col      -       add operation to move back a column
 854  *      @ldata: n_tty data
 855  *
 856  *      Add an operation to the echo buffer to move back one column.
 857  */
 858
 859 static void echo_move_back_col(struct n_tty_data *ldata)
 860 {
 861         add_echo_byte(ECHO_OP_START, ldata);
 862         add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
 863 }
 864
 865 /**
 866  *      echo_set_canon_col      -       add operation to set the canon column
 867  *      @ldata: n_tty data
 868  *
 869  *      Add an operation to the echo buffer to set the canon column
 870  *      to the current column.
 871  */
 872
 873 static void echo_set_canon_col(struct n_tty_data *ldata)
 874 {
 875         add_echo_byte(ECHO_OP_START, ldata);
 876         add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
 877 }
 878
 879 /**
 880  *      echo_erase_tab  -       add operation to erase a tab
 881  *      @num_chars: number of character columns already used
 882  *      @after_tab: true if num_chars starts after a previous tab
 883  *      @ldata: n_tty data
 884  *
 885  *      Add an operation to the echo buffer to erase a tab.
 886  *
 887  *      Called by the eraser function, which knows how many character
 888  *      columns have been used since either a previous tab or the start
 889  *      of input.  This information will be used later, along with
 890  *      canon column (if applicable), to go back the correct number
 891  *      of columns.
 892  */
 893
 894 static void echo_erase_tab(unsigned int num_chars, int after_tab,
 895                            struct n_tty_data *ldata)
 896 {
 897         add_echo_byte(ECHO_OP_START, ldata);
 898         add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
 899
 900         /* We only need to know this modulo 8 (tab spacing) */
 901         num_chars &= 7;
 902
 903         /* Set the high bit as a flag if num_chars is after a previous tab */
 904         if (after_tab)
 905                 num_chars |= 0x80;
 906
 907         add_echo_byte(num_chars, ldata);
 908 }
 909
 910 /**
 911  *      echo_char_raw   -       echo a character raw
 912  *      @c: unicode byte to echo
 913  *      @tty: terminal device
 914  *
 915  *      Echo user input back onto the screen. This must be called only when
 916  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
 917  *
 918  *      This variant does not treat control characters specially.
 919  */
 920
 921 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
 922 {
 923         if (c == ECHO_OP_START) {
 924                 add_echo_byte(ECHO_OP_START, ldata);
 925                 add_echo_byte(ECHO_OP_START, ldata);
 926         } else {
 927                 add_echo_byte(c, ldata);
 928         }
 929 }
 930
 931 /**
 932  *      echo_char       -       echo a character
 933  *      @c: unicode byte to echo
 934  *      @tty: terminal device
 935  *
 936  *      Echo user input back onto the screen. This must be called only when
 937  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
 938  *
 939  *      This variant tags control characters to be echoed as "^X"
 940  *      (where X is the letter representing the control char).
 941  */
 942
 943 static void echo_char(unsigned char c, struct tty_struct *tty)
 944 {
 945         struct n_tty_data *ldata = tty->disc_data;
 946
 947         if (c == ECHO_OP_START) {
 948                 add_echo_byte(ECHO_OP_START, ldata);
 949                 add_echo_byte(ECHO_OP_START, ldata);
 950         } else {
 951                 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
 952                         add_echo_byte(ECHO_OP_START, ldata);
 953                 add_echo_byte(c, ldata);
 954         }
 955 }
 956
 957 /**
 958  *      finish_erasing          -       complete erase
 959  *      @ldata: n_tty data
 960  */
 961
 962 static inline void finish_erasing(struct n_tty_data *ldata)
 963 {
 964         if (ldata->erasing) {
 965                 echo_char_raw('/', ldata);
 966                 ldata->erasing = 0;
 967         }
 968 }
 969
 970 /**
 971  *      eraser          -       handle erase function
 972  *      @c: character input
 973  *      @tty: terminal device
 974  *
 975  *      Perform erase and necessary output when an erase character is
 976  *      present in the stream from the driver layer. Handles the complexities
 977  *      of UTF-8 multibyte symbols.
 978  *
 979  *      n_tty_receive_buf()/producer path:
 980  *              caller holds non-exclusive termios_rwsem
 981  *              modifies read_head
 982  *
 983  *      Modifying the read_head is not considered a publish in this context
 984  *      because canonical mode is active -- only canon_head publishes
 985  */
 986
 987 static void eraser(unsigned char c, struct tty_struct *tty)
 988 {
 989         struct n_tty_data *ldata = tty->disc_data;
 990         enum { ERASE, WERASE, KILL } kill_type;
 991         size_t head;
 992         size_t cnt;
 993         int seen_alnums;
 994
 995         if (ldata->read_head == ldata->canon_head) {
 996                 /* process_output('\a', tty); */ /* what do you think? */
 997                 return;
 998         }
 999         if (c == ERASE_CHAR(tty))
1000                 kill_type = ERASE;
1001         else if (c == WERASE_CHAR(tty))
1002                 kill_type = WERASE;
1003         else {
1004                 if (!L_ECHO(tty)) {
1005                         ldata->read_head = ldata->canon_head;
1006                         return;
1007                 }
1008                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1009                         ldata->read_head = ldata->canon_head;
1010                         finish_erasing(ldata);
1011                         echo_char(KILL_CHAR(tty), tty);
1012                         /* Add a newline if ECHOK is on and ECHOKE is off. */
1013                         if (L_ECHOK(tty))
1014                                 echo_char_raw('\n', ldata);
1015                         return;
1016                 }
1017                 kill_type = KILL;
1018         }
1019
1020         seen_alnums = 0;
1021         while (ldata->read_head != ldata->canon_head) {
1022                 head = ldata->read_head;
1023
1024                 /* erase a single possibly multibyte character */
1025                 do {
1026                         head--;
1027                         c = read_buf(ldata, head);
1028                 } while (is_continuation(c, tty) && head != ldata->canon_head);
1029
1030                 /* do not partially erase */
1031                 if (is_continuation(c, tty))
1032                         break;
1033
1034                 if (kill_type == WERASE) {
1035                         /* Equivalent to BSD's ALTWERASE. */
1036                         if (isalnum(c) || c == '_')
1037                                 seen_alnums++;
1038                         else if (seen_alnums)
1039                                 break;
1040                 }
1041                 cnt = ldata->read_head - head;
1042                 ldata->read_head = head;
1043                 if (L_ECHO(tty)) {
1044                         if (L_ECHOPRT(tty)) {
1045                                 if (!ldata->erasing) {
1046                                         echo_char_raw('\\', ldata);
1047                                         ldata->erasing = 1;
1048                                 }
1049                                 /* if cnt > 1, output a multi-byte character */
1050                                 echo_char(c, tty);
1051                                 while (--cnt > 0) {
1052                                         head++;
1053                                         echo_char_raw(read_buf(ldata, head), ldata);
1054                                         echo_move_back_col(ldata);
1055                                 }
1056                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1057                                 echo_char(ERASE_CHAR(tty), tty);
1058                         } else if (c == '\t') {
1059                                 unsigned int num_chars = 0;
1060                                 int after_tab = 0;
1061                                 size_t tail = ldata->read_head;
1062
1063                                 /*
1064                                  * Count the columns used for characters
1065                                  * since the start of input or after a
1066                                  * previous tab.
1067                                  * This info is used to go back the correct
1068                                  * number of columns.
1069                                  */
1070                                 while (tail != ldata->canon_head) {
1071                                         tail--;
1072                                         c = read_buf(ldata, tail);
1073                                         if (c == '\t') {
1074                                                 after_tab = 1;
1075                                                 break;
1076                                         } else if (iscntrl(c)) {
1077                                                 if (L_ECHOCTL(tty))
1078                                                         num_chars += 2;
1079                                         } else if (!is_continuation(c, tty)) {
1080                                                 num_chars++;
1081                                         }
1082                                 }
1083                                 echo_erase_tab(num_chars, after_tab, ldata);
1084                         } else {
1085                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
1086                                         echo_char_raw('\b', ldata);
1087                                         echo_char_raw(' ', ldata);
1088                                         echo_char_raw('\b', ldata);
1089                                 }
1090                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1091                                         echo_char_raw('\b', ldata);
1092                                         echo_char_raw(' ', ldata);
1093                                         echo_char_raw('\b', ldata);
1094                                 }
1095                         }
1096                 }
1097                 if (kill_type == ERASE)
1098                         break;
1099         }
1100         if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1101                 finish_erasing(ldata);
1102 }
1103
1104 /**
1105  *      isig            -       handle the ISIG optio
1106  *      @sig: signal
1107  *      @tty: terminal
1108  *
1109  *      Called when a signal is being sent due to terminal input.
1110  *      Called from the driver receive_buf path so serialized.
1111  *
1112  *      Locking: ctrl_lock
1113  */
1114
1115 static inline void isig(int sig, struct tty_struct *tty)
1116 {
1117         struct pid *tty_pgrp = tty_get_pgrp(tty);
1118         if (tty_pgrp) {
1119                 kill_pgrp(tty_pgrp, sig, 1);
1120                 put_pid(tty_pgrp);
1121         }
1122 }
1123
1124 /**
1125  *      n_tty_receive_break     -       handle break
1126  *      @tty: terminal
1127  *
1128  *      An RS232 break event has been hit in the incoming bitstream. This
1129  *      can cause a variety of events depending upon the termios settings.
1130  *
1131  *      n_tty_receive_buf()/producer path:
1132  *              caller holds non-exclusive termios_rwsem
1133  *              publishes read_head via put_tty_queue()
1134  *
1135  *      Note: may get exclusive termios_rwsem if flushing input buffer
1136  */
1137
1138 static inline void n_tty_receive_break(struct tty_struct *tty)
1139 {
1140         struct n_tty_data *ldata = tty->disc_data;
1141
1142         if (I_IGNBRK(tty))
1143                 return;
1144         if (I_BRKINT(tty)) {
1145                 isig(SIGINT, tty);
1146                 if (!L_NOFLSH(tty)) {
1147                         /* flushing needs exclusive termios_rwsem */
1148                         up_read(&tty->termios_rwsem);
1149                         n_tty_flush_buffer(tty);
1150                         tty_driver_flush_buffer(tty);
1151                         down_read(&tty->termios_rwsem);
1152                 }
1153                 return;
1154         }
1155         if (I_PARMRK(tty)) {
1156                 put_tty_queue('\377', ldata);
1157                 put_tty_queue('\0', ldata);
1158         }
1159         put_tty_queue('\0', ldata);
1160         wake_up_interruptible(&tty->read_wait);
1161 }
1162
1163 /**
1164  *      n_tty_receive_overrun   -       handle overrun reporting
1165  *      @tty: terminal
1166  *
1167  *      Data arrived faster than we could process it. While the tty
1168  *      driver has flagged this the bits that were missed are gone
1169  *      forever.
1170  *
1171  *      Called from the receive_buf path so single threaded. Does not
1172  *      need locking as num_overrun and overrun_time are function
1173  *      private.
1174  */
1175
1176 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1177 {
1178         struct n_tty_data *ldata = tty->disc_data;
1179         char buf[64];
1180
1181         ldata->num_overrun++;
1182         if (time_after(jiffies, ldata->overrun_time + HZ) ||
1183                         time_after(ldata->overrun_time, jiffies)) {
1184                 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1185                         tty_name(tty, buf),
1186                         ldata->num_overrun);
1187                 ldata->overrun_time = jiffies;
1188                 ldata->num_overrun = 0;
1189         }
1190 }
1191
1192 /**
1193  *      n_tty_receive_parity_error      -       error notifier
1194  *      @tty: terminal device
1195  *      @c: character
1196  *
1197  *      Process a parity error and queue the right data to indicate
1198  *      the error case if necessary.
1199  *
1200  *      n_tty_receive_buf()/producer path:
1201  *              caller holds non-exclusive termios_rwsem
1202  *              publishes read_head via put_tty_queue()
1203  */
1204 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1205                                               unsigned char c)
1206 {
1207         struct n_tty_data *ldata = tty->disc_data;
1208
1209         if (I_IGNPAR(tty))
1210                 return;
1211         if (I_PARMRK(tty)) {
1212                 put_tty_queue('\377', ldata);
1213                 put_tty_queue('\0', ldata);
1214                 put_tty_queue(c, ldata);
1215         } else  if (I_INPCK(tty))
1216                 put_tty_queue('\0', ldata);
1217         else
1218                 put_tty_queue(c, ldata);
1219         wake_up_interruptible(&tty->read_wait);
1220 }
1221
1222 /**
1223  *      n_tty_receive_char      -       perform processing
1224  *      @tty: terminal device
1225  *      @c: character
1226  *
1227  *      Process an individual character of input received from the driver.
1228  *      This is serialized with respect to itself by the rules for the
1229  *      driver above.
1230  *
1231  *      n_tty_receive_buf()/producer path:
1232  *              caller holds non-exclusive termios_rwsem
1233  *              publishes canon_head if canonical mode is active
1234  *              otherwise, publishes read_head via put_tty_queue()
1235  */
1236
1237 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1238 {
1239         struct n_tty_data *ldata = tty->disc_data;
1240         int parmrk;
1241
1242         if (ldata->raw) {
1243                 put_tty_queue(c, ldata);
1244                 return;
1245         }
1246
1247         if (I_ISTRIP(tty))
1248                 c &= 0x7f;
1249         if (I_IUCLC(tty) && L_IEXTEN(tty))
1250                 c = tolower(c);
1251
1252         if (L_EXTPROC(tty)) {
1253                 put_tty_queue(c, ldata);
1254                 return;
1255         }
1256
1257         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1258             I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1259             c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1260                 start_tty(tty);
1261                 process_echoes(tty);
1262         }
1263
1264         if (tty->closing) {
1265                 if (I_IXON(tty)) {
1266                         if (c == START_CHAR(tty)) {
1267                                 start_tty(tty);
1268                                 process_echoes(tty);
1269                         } else if (c == STOP_CHAR(tty))
1270                                 stop_tty(tty);
1271                 }
1272                 return;
1273         }
1274
1275         /*
1276          * If the previous character was LNEXT, or we know that this
1277          * character is not one of the characters that we'll have to
1278          * handle specially, do shortcut processing to speed things
1279          * up.
1280          */
1281         if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1282                 ldata->lnext = 0;
1283                 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1284                 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1285                         /* beep if no space */
1286                         if (L_ECHO(tty))
1287                                 process_output('\a', tty);
1288                         return;
1289                 }
1290                 if (L_ECHO(tty)) {
1291                         finish_erasing(ldata);
1292                         /* Record the column of first canon char. */
1293                         if (ldata->canon_head == ldata->read_head)
1294                                 echo_set_canon_col(ldata);
1295                         echo_char(c, tty);
1296                         commit_echoes(tty);
1297                 }
1298                 if (parmrk)
1299                         put_tty_queue(c, ldata);
1300                 put_tty_queue(c, ldata);
1301                 return;
1302         }
1303
1304         if (I_IXON(tty)) {
1305                 if (c == START_CHAR(tty)) {
1306                         start_tty(tty);
1307                         commit_echoes(tty);
1308                         return;
1309                 }
1310                 if (c == STOP_CHAR(tty)) {
1311                         stop_tty(tty);
1312                         return;
1313                 }
1314         }
1315
1316         if (L_ISIG(tty)) {
1317                 int signal;
1318                 signal = SIGINT;
1319                 if (c == INTR_CHAR(tty))
1320                         goto send_signal;
1321                 signal = SIGQUIT;
1322                 if (c == QUIT_CHAR(tty))
1323                         goto send_signal;
1324                 signal = SIGTSTP;
1325                 if (c == SUSP_CHAR(tty)) {
1326 send_signal:
1327                         if (!L_NOFLSH(tty)) {
1328                                 /* flushing needs exclusive termios_rwsem */
1329                                 up_read(&tty->termios_rwsem);
1330                                 n_tty_flush_buffer(tty);
1331                                 tty_driver_flush_buffer(tty);
1332                                 down_read(&tty->termios_rwsem);
1333                         }
1334                         if (I_IXON(tty))
1335                                 start_tty(tty);
1336                         if (L_ECHO(tty)) {
1337                                 echo_char(c, tty);
1338                                 commit_echoes(tty);
1339                         }
1340                         isig(signal, tty);
1341                         return;
1342                 }
1343         }
1344
1345         if (c == '\r') {
1346                 if (I_IGNCR(tty))
1347                         return;
1348                 if (I_ICRNL(tty))
1349                         c = '\n';
1350         } else if (c == '\n' && I_INLCR(tty))
1351                 c = '\r';
1352
1353         if (ldata->icanon) {
1354                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1355                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1356                         eraser(c, tty);
1357                         commit_echoes(tty);
1358                         return;
1359                 }
1360                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1361                         ldata->lnext = 1;
1362                         if (L_ECHO(tty)) {
1363                                 finish_erasing(ldata);
1364                                 if (L_ECHOCTL(tty)) {
1365                                         echo_char_raw('^', ldata);
1366                                         echo_char_raw('\b', ldata);
1367                                         commit_echoes(tty);
1368                                 }
1369                         }
1370                         return;
1371                 }
1372                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1373                     L_IEXTEN(tty)) {
1374                         size_t tail = ldata->canon_head;
1375
1376                         finish_erasing(ldata);
1377                         echo_char(c, tty);
1378                         echo_char_raw('\n', ldata);
1379                         while (tail != ldata->read_head) {
1380                                 echo_char(read_buf(ldata, tail), tty);
1381                                 tail++;
1382                         }
1383                         commit_echoes(tty);
1384                         return;
1385                 }
1386                 if (c == '\n') {
1387                         if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
1388                                 if (L_ECHO(tty))
1389                                         process_output('\a', tty);
1390                                 return;
1391                         }
1392                         if (L_ECHO(tty) || L_ECHONL(tty)) {
1393                                 echo_char_raw('\n', ldata);
1394                                 commit_echoes(tty);
1395                         }
1396                         goto handle_newline;
1397                 }
1398                 if (c == EOF_CHAR(tty)) {
1399                         if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
1400                                 return;
1401                         c = __DISABLED_CHAR;
1402                         goto handle_newline;
1403                 }
1404                 if ((c == EOL_CHAR(tty)) ||
1405                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1406                         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1407                                  ? 1 : 0;
1408                         if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
1409                                 if (L_ECHO(tty))
1410                                         process_output('\a', tty);
1411                                 return;
1412                         }
1413                         /*
1414                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1415                          */
1416                         if (L_ECHO(tty)) {
1417                                 /* Record the column of first canon char. */
1418                                 if (ldata->canon_head == ldata->read_head)
1419                                         echo_set_canon_col(ldata);
1420                                 echo_char(c, tty);
1421                                 commit_echoes(tty);
1422                         }
1423                         /*
1424                          * XXX does PARMRK doubling happen for
1425                          * EOL_CHAR and EOL2_CHAR?
1426                          */
1427                         if (parmrk)
1428                                 put_tty_queue(c, ldata);
1429
1430 handle_newline:
1431                         set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1432                         put_tty_queue(c, ldata);
1433                         ldata->canon_head = ldata->read_head;
1434                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1435                         if (waitqueue_active(&tty->read_wait))
1436                                 wake_up_interruptible(&tty->read_wait);
1437                         return;
1438                 }
1439         }
1440
1441         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1442         if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1443                 /* beep if no space */
1444                 if (L_ECHO(tty))
1445                         process_output('\a', tty);
1446                 return;
1447         }
1448         if (L_ECHO(tty)) {
1449                 finish_erasing(ldata);
1450                 if (c == '\n')
1451                         echo_char_raw('\n', ldata);
1452                 else {
1453                         /* Record the column of first canon char. */
1454                         if (ldata->canon_head == ldata->read_head)
1455                                 echo_set_canon_col(ldata);
1456                         echo_char(c, tty);
1457                 }
1458                 commit_echoes(tty);
1459         }
1460
1461         if (parmrk)
1462                 put_tty_queue(c, ldata);
1463
1464         put_tty_queue(c, ldata);
1465 }
1466
1467 /**
1468  *      n_tty_receive_buf       -       data receive
1469  *      @tty: terminal device
1470  *      @cp: buffer
1471  *      @fp: flag buffer
1472  *      @count: characters
1473  *
1474  *      Called by the terminal driver when a block of characters has
1475  *      been received. This function must be called from soft contexts
1476  *      not from interrupt context. The driver is responsible for making
1477  *      calls one at a time and in order (or using flush_to_ldisc)
1478  *
1479  *      n_tty_receive_buf()/producer path:
1480  *              claims non-exclusive termios_rwsem
1481  *              publishes read_head and canon_head
1482  */
1483
1484 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1485                           char *fp, int count)
1486 {
1487         struct n_tty_data *ldata = tty->disc_data;
1488         char    flags = TTY_NORMAL;
1489         char    buf[64];
1490
1491         if (ldata->real_raw) {
1492                 size_t n, head;
1493
1494                 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1495                 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1496                 n = min_t(size_t, count, n);
1497                 memcpy(read_buf_addr(ldata, head), cp, n);
1498                 ldata->read_head += n;
1499                 cp += n;
1500                 count -= n;
1501
1502                 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1503                 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1504                 n = min_t(size_t, count, n);
1505                 memcpy(read_buf_addr(ldata, head), cp, n);
1506                 ldata->read_head += n;
1507         } else {
1508                 int i;
1509
1510                 for (i = count; i; i--, cp++) {
1511                         if (fp)
1512                                 flags = *fp++;
1513                         switch (flags) {
1514                         case TTY_NORMAL:
1515                                 n_tty_receive_char(tty, *cp);
1516                                 break;
1517                         case TTY_BREAK:
1518                                 n_tty_receive_break(tty);
1519                                 break;
1520                         case TTY_PARITY:
1521                         case TTY_FRAME:
1522                                 n_tty_receive_parity_error(tty, *cp);
1523                                 break;
1524                         case TTY_OVERRUN:
1525                                 n_tty_receive_overrun(tty);
1526                                 break;
1527                         default:
1528                                 printk(KERN_ERR "%s: unknown flag %d\n",
1529                                        tty_name(tty, buf), flags);
1530                                 break;
1531                         }
1532                 }
1533
1534                 flush_echoes(tty);
1535                 if (tty->ops->flush_chars)
1536                         tty->ops->flush_chars(tty);
1537         }
1538
1539         if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1540                 L_EXTPROC(tty)) {
1541                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1542                 if (waitqueue_active(&tty->read_wait))
1543                         wake_up_interruptible(&tty->read_wait);
1544         }
1545
1546         n_tty_check_throttle(tty);
1547 }
1548
1549 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1550                               char *fp, int count)
1551 {
1552         down_read(&tty->termios_rwsem);
1553         __receive_buf(tty, cp, fp, count);
1554         up_read(&tty->termios_rwsem);
1555 }
1556
1557 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1558                               char *fp, int count)
1559 {
1560         struct n_tty_data *ldata = tty->disc_data;
1561         int room;
1562
1563         down_read(&tty->termios_rwsem);
1564
1565         tty->receive_room = room = receive_room(tty);
1566         if (!room)
1567                 ldata->no_room = 1;
1568         count = min(count, room);
1569         if (count)
1570                 __receive_buf(tty, cp, fp, count);
1571
1572         up_read(&tty->termios_rwsem);
1573
1574         return count;
1575 }
1576
1577 int is_ignored(int sig)
1578 {
1579         return (sigismember(&current->blocked, sig) ||
1580                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1581 }
1582
1583 /**
1584  *      n_tty_set_termios       -       termios data changed
1585  *      @tty: terminal
1586  *      @old: previous data
1587  *
1588  *      Called by the tty layer when the user changes termios flags so
1589  *      that the line discipline can plan ahead. This function cannot sleep
1590  *      and is protected from re-entry by the tty layer. The user is
1591  *      guaranteed that this function will not be re-entered or in progress
1592  *      when the ldisc is closed.
1593  *
1594  *      Locking: Caller holds tty->termios_rwsem
1595  */
1596
1597 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1598 {
1599         struct n_tty_data *ldata = tty->disc_data;
1600         int canon_change = 1;
1601
1602         if (old)
1603                 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1604         if (canon_change) {
1605                 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1606                 ldata->line_start = 0;
1607                 ldata->canon_head = ldata->read_tail;
1608                 ldata->erasing = 0;
1609                 ldata->lnext = 0;
1610         }
1611
1612         if (canon_change && !L_ICANON(tty) && read_cnt(ldata))
1613                 wake_up_interruptible(&tty->read_wait);
1614
1615         ldata->icanon = (L_ICANON(tty) != 0);
1616
1617         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1618             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1619             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1620             I_PARMRK(tty)) {
1621                 bitmap_zero(ldata->process_char_map, 256);
1622
1623                 if (I_IGNCR(tty) || I_ICRNL(tty))
1624                         set_bit('\r', ldata->process_char_map);
1625                 if (I_INLCR(tty))
1626                         set_bit('\n', ldata->process_char_map);
1627
1628                 if (L_ICANON(tty)) {
1629                         set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1630                         set_bit(KILL_CHAR(tty), ldata->process_char_map);
1631                         set_bit(EOF_CHAR(tty), ldata->process_char_map);
1632                         set_bit('\n', ldata->process_char_map);
1633                         set_bit(EOL_CHAR(tty), ldata->process_char_map);
1634                         if (L_IEXTEN(tty)) {
1635                                 set_bit(WERASE_CHAR(tty),
1636                                         ldata->process_char_map);
1637                                 set_bit(LNEXT_CHAR(tty),
1638                                         ldata->process_char_map);
1639                                 set_bit(EOL2_CHAR(tty),
1640                                         ldata->process_char_map);
1641                                 if (L_ECHO(tty))
1642                                         set_bit(REPRINT_CHAR(tty),
1643                                                 ldata->process_char_map);
1644                         }
1645                 }
1646                 if (I_IXON(tty)) {
1647                         set_bit(START_CHAR(tty), ldata->process_char_map);
1648                         set_bit(STOP_CHAR(tty), ldata->process_char_map);
1649                 }
1650                 if (L_ISIG(tty)) {
1651                         set_bit(INTR_CHAR(tty), ldata->process_char_map);
1652                         set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1653                         set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1654                 }
1655                 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1656                 ldata->raw = 0;
1657                 ldata->real_raw = 0;
1658         } else {
1659                 ldata->raw = 1;
1660                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1661                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1662                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1663                         ldata->real_raw = 1;
1664                 else
1665                         ldata->real_raw = 0;
1666         }
1667         n_tty_set_room(tty);
1668         /*
1669          * Fix tty hang when I_IXON(tty) is cleared, but the tty
1670          * been stopped by STOP_CHAR(tty) before it.
1671          */
1672         if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1673                 start_tty(tty);
1674         }
1675
1676         /* The termios change make the tty ready for I/O */
1677         wake_up_interruptible(&tty->write_wait);
1678         wake_up_interruptible(&tty->read_wait);
1679 }
1680
1681 /**
1682  *      n_tty_close             -       close the ldisc for this tty
1683  *      @tty: device
1684  *
1685  *      Called from the terminal layer when this line discipline is
1686  *      being shut down, either because of a close or becsuse of a
1687  *      discipline change. The function will not be called while other
1688  *      ldisc methods are in progress.
1689  */
1690
1691 static void n_tty_close(struct tty_struct *tty)
1692 {
1693         struct n_tty_data *ldata = tty->disc_data;
1694
1695         if (tty->link)
1696                 n_tty_packet_mode_flush(tty);
1697
1698         vfree(ldata);
1699         tty->disc_data = NULL;
1700 }
1701
1702 /**
1703  *      n_tty_open              -       open an ldisc
1704  *      @tty: terminal to open
1705  *
1706  *      Called when this line discipline is being attached to the
1707  *      terminal device. Can sleep. Called serialized so that no
1708  *      other events will occur in parallel. No further open will occur
1709  *      until a close.
1710  */
1711
1712 static int n_tty_open(struct tty_struct *tty)
1713 {
1714         struct n_tty_data *ldata;
1715
1716         /* Currently a malloc failure here can panic */
1717         ldata = vmalloc(sizeof(*ldata));
1718         if (!ldata)
1719                 goto err;
1720
1721         ldata->overrun_time = jiffies;
1722         mutex_init(&ldata->atomic_read_lock);
1723         mutex_init(&ldata->output_lock);
1724
1725         tty->disc_data = ldata;
1726         reset_buffer_flags(tty->disc_data);
1727         ldata->column = 0;
1728         ldata->canon_column = 0;
1729         ldata->minimum_to_wake = 1;
1730         ldata->num_overrun = 0;
1731         ldata->no_room = 0;
1732         ldata->lnext = 0;
1733         tty->closing = 0;
1734         /* indicate buffer work may resume */
1735         clear_bit(TTY_LDISC_HALTED, &tty->flags);
1736         n_tty_set_termios(tty, NULL);
1737         tty_unthrottle(tty);
1738
1739         return 0;
1740 err:
1741         return -ENOMEM;
1742 }
1743
1744 static inline int input_available_p(struct tty_struct *tty, int amt)
1745 {
1746         struct n_tty_data *ldata = tty->disc_data;
1747
1748         if (ldata->icanon && !L_EXTPROC(tty)) {
1749                 if (ldata->canon_head != ldata->read_tail)
1750                         return 1;
1751         } else if (read_cnt(ldata) >= (amt ? amt : 1))
1752                 return 1;
1753
1754         return 0;
1755 }
1756
1757 /**
1758  *      copy_from_read_buf      -       copy read data directly
1759  *      @tty: terminal device
1760  *      @b: user data
1761  *      @nr: size of data
1762  *
1763  *      Helper function to speed up n_tty_read.  It is only called when
1764  *      ICANON is off; it copies characters straight from the tty queue to
1765  *      user space directly.  It can be profitably called twice; once to
1766  *      drain the space from the tail pointer to the (physical) end of the
1767  *      buffer, and once to drain the space from the (physical) beginning of
1768  *      the buffer to head pointer.
1769  *
1770  *      Called under the ldata->atomic_read_lock sem
1771  *
1772  *      n_tty_read()/consumer path:
1773  *              caller holds non-exclusive termios_rwsem
1774  *              read_tail published
1775  */
1776
1777 static int copy_from_read_buf(struct tty_struct *tty,
1778                                       unsigned char __user **b,
1779                                       size_t *nr)
1780
1781 {
1782         struct n_tty_data *ldata = tty->disc_data;
1783         int retval;
1784         size_t n;
1785         bool is_eof;
1786         size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1787
1788         retval = 0;
1789         n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1790         n = min(*nr, n);
1791         if (n) {
1792                 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1793                 n -= retval;
1794                 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1795                 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1796                                 ldata->icanon);
1797                 ldata->read_tail += n;
1798                 /* Turn single EOF into zero-length read */
1799                 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1800                         n = 0;
1801                 *b += n;
1802                 *nr -= n;
1803         }
1804         return retval;
1805 }
1806
1807 /**
1808  *      canon_copy_from_read_buf        -       copy read data in canonical mode
1809  *      @tty: terminal device
1810  *      @b: user data
1811  *      @nr: size of data
1812  *
1813  *      Helper function for n_tty_read.  It is only called when ICANON is on;
1814  *      it copies one line of input up to and including the line-delimiting
1815  *      character into the user-space buffer.
1816  *
1817  *      Called under the atomic_read_lock mutex
1818  *
1819  *      n_tty_read()/consumer path:
1820  *              caller holds non-exclusive termios_rwsem
1821  *              read_tail published
1822  */
1823
1824 static int canon_copy_from_read_buf(struct tty_struct *tty,
1825                                     unsigned char __user **b,
1826                                     size_t *nr)
1827 {
1828         struct n_tty_data *ldata = tty->disc_data;
1829         size_t n, size, more, c;
1830         size_t eol;
1831         size_t tail;
1832         int ret, found = 0;
1833         bool eof_push = 0;
1834
1835         /* N.B. avoid overrun if nr == 0 */
1836         n = min(*nr, read_cnt(ldata));
1837         if (!n)
1838                 return 0;
1839
1840         tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1841         size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1842
1843         n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1844                     __func__, *nr, tail, n, size);
1845
1846         eol = find_next_bit(ldata->read_flags, size, tail);
1847         more = n - (size - tail);
1848         if (eol == N_TTY_BUF_SIZE && more) {
1849                 /* scan wrapped without finding set bit */
1850                 eol = find_next_bit(ldata->read_flags, more, 0);
1851                 if (eol != more)
1852                         found = 1;
1853         } else if (eol != size)
1854                 found = 1;
1855
1856         size = N_TTY_BUF_SIZE - tail;
1857         n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
1858         c = n;
1859
1860         if (found && read_buf(ldata, eol) == __DISABLED_CHAR) {
1861                 n--;
1862                 eof_push = !n && ldata->read_tail != ldata->line_start;
1863         }
1864
1865         n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
1866                     __func__, eol, found, n, c, size, more);
1867
1868         if (n > size) {
1869                 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
1870                 if (ret)
1871                         return -EFAULT;
1872                 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
1873         } else
1874                 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1875
1876         if (ret)
1877                 return -EFAULT;
1878         *b += n;
1879         *nr -= n;
1880
1881         if (found)
1882                 clear_bit(eol, ldata->read_flags);
1883         smp_mb__after_clear_bit();
1884         ldata->read_tail += c;
1885
1886         if (found) {
1887                 ldata->line_start = ldata->read_tail;
1888                 tty_audit_push(tty);
1889         }
1890         return eof_push ? -EAGAIN : 0;
1891 }
1892
1893 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1894                                                         size_t, loff_t *);
1895
1896 /**
1897  *      job_control             -       check job control
1898  *      @tty: tty
1899  *      @file: file handle
1900  *
1901  *      Perform job control management checks on this file/tty descriptor
1902  *      and if appropriate send any needed signals and return a negative
1903  *      error code if action should be taken.
1904  *
1905  *      Locking: redirected write test is safe
1906  *               current->signal->tty check is safe
1907  *               ctrl_lock to safely reference tty->pgrp
1908  */
1909
1910 static int job_control(struct tty_struct *tty, struct file *file)
1911 {
1912         /* Job control check -- must be done at start and after
1913            every sleep (POSIX.1 7.1.1.4). */
1914         /* NOTE: not yet done after every sleep pending a thorough
1915            check of the logic of this change. -- jlc */
1916         /* don't stop on /dev/console */
1917         if (file->f_op->write == redirected_tty_write ||
1918             current->signal->tty != tty)
1919                 return 0;
1920
1921         spin_lock_irq(&tty->ctrl_lock);
1922         if (!tty->pgrp)
1923                 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1924         else if (task_pgrp(current) != tty->pgrp) {
1925                 spin_unlock_irq(&tty->ctrl_lock);
1926                 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1927                         return -EIO;
1928                 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1929                 set_thread_flag(TIF_SIGPENDING);
1930                 return -ERESTARTSYS;
1931         }
1932         spin_unlock_irq(&tty->ctrl_lock);
1933         return 0;
1934 }
1935
1936
1937 /**
1938  *      n_tty_read              -       read function for tty
1939  *      @tty: tty device
1940  *      @file: file object
1941  *      @buf: userspace buffer pointer
1942  *      @nr: size of I/O
1943  *
1944  *      Perform reads for the line discipline. We are guaranteed that the
1945  *      line discipline will not be closed under us but we may get multiple
1946  *      parallel readers and must handle this ourselves. We may also get
1947  *      a hangup. Always called in user context, may sleep.
1948  *
1949  *      This code must be sure never to sleep through a hangup.
1950  *
1951  *      n_tty_read()/consumer path:
1952  *              claims non-exclusive termios_rwsem
1953  *              publishes read_tail
1954  */
1955
1956 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1957                          unsigned char __user *buf, size_t nr)
1958 {
1959         struct n_tty_data *ldata = tty->disc_data;
1960         unsigned char __user *b = buf;
1961         DECLARE_WAITQUEUE(wait, current);
1962         int c;
1963         int minimum, time;
1964         ssize_t retval = 0;
1965         long timeout;
1966         unsigned long flags;
1967         int packet;
1968
1969         c = job_control(tty, file);
1970         if (c < 0)
1971                 return c;
1972
1973         down_read(&tty->termios_rwsem);
1974
1975         minimum = time = 0;
1976         timeout = MAX_SCHEDULE_TIMEOUT;
1977         if (!ldata->icanon) {
1978                 minimum = MIN_CHAR(tty);
1979                 if (minimum) {
1980                         time = (HZ / 10) * TIME_CHAR(tty);
1981                         if (time)
1982                                 ldata->minimum_to_wake = 1;
1983                         else if (!waitqueue_active(&tty->read_wait) ||
1984                                  (ldata->minimum_to_wake > minimum))
1985                                 ldata->minimum_to_wake = minimum;
1986                 } else {
1987                         timeout = (HZ / 10) * TIME_CHAR(tty);
1988                         ldata->minimum_to_wake = minimum = 1;
1989                 }
1990         }
1991
1992         /*
1993          *      Internal serialization of reads.
1994          */
1995         if (file->f_flags & O_NONBLOCK) {
1996                 if (!mutex_trylock(&ldata->atomic_read_lock)) {
1997                         up_read(&tty->termios_rwsem);
1998                         return -EAGAIN;
1999                 }
2000         } else {
2001                 if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
2002                         up_read(&tty->termios_rwsem);
2003                         return -ERESTARTSYS;
2004                 }
2005         }
2006         packet = tty->packet;
2007
2008         add_wait_queue(&tty->read_wait, &wait);
2009         while (nr) {
2010                 /* First test for status change. */
2011                 if (packet && tty->link->ctrl_status) {
2012                         unsigned char cs;
2013                         if (b != buf)
2014                                 break;
2015                         spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2016                         cs = tty->link->ctrl_status;
2017                         tty->link->ctrl_status = 0;
2018                         spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2019                         if (tty_put_user(tty, cs, b++)) {
2020                                 retval = -EFAULT;
2021                                 b--;
2022                                 break;
2023                         }
2024                         nr--;
2025                         break;
2026                 }
2027                 /* This statement must be first before checking for input
2028                    so that any interrupt will set the state back to
2029                    TASK_RUNNING. */
2030                 set_current_state(TASK_INTERRUPTIBLE);
2031
2032                 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2033                     ((minimum - (b - buf)) >= 1))
2034                         ldata->minimum_to_wake = (minimum - (b - buf));
2035
2036                 if (!input_available_p(tty, 0)) {
2037                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2038                                 retval = -EIO;
2039                                 break;
2040                         }
2041                         if (tty_hung_up_p(file))
2042                                 break;
2043                         if (!timeout)
2044                                 break;
2045                         if (file->f_flags & O_NONBLOCK) {
2046                                 retval = -EAGAIN;
2047                                 break;
2048                         }
2049                         if (signal_pending(current)) {
2050                                 retval = -ERESTARTSYS;
2051                                 break;
2052                         }
2053                         n_tty_set_room(tty);
2054                         up_read(&tty->termios_rwsem);
2055
2056                         timeout = schedule_timeout(timeout);
2057
2058                         down_read(&tty->termios_rwsem);
2059                         continue;
2060                 }
2061                 __set_current_state(TASK_RUNNING);
2062
2063                 /* Deal with packet mode. */
2064                 if (packet && b == buf) {
2065                         if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2066                                 retval = -EFAULT;
2067                                 b--;
2068                                 break;
2069                         }
2070                         nr--;
2071                 }
2072
2073                 if (ldata->icanon && !L_EXTPROC(tty)) {
2074                         retval = canon_copy_from_read_buf(tty, &b, &nr);
2075                         if (retval == -EAGAIN) {
2076                                 retval = 0;
2077                                 continue;
2078                         } else if (retval)
2079                                 break;
2080                 } else {
2081                         int uncopied;
2082                         /* The copy function takes the read lock and handles
2083                            locking internally for this case */
2084                         uncopied = copy_from_read_buf(tty, &b, &nr);
2085                         uncopied += copy_from_read_buf(tty, &b, &nr);
2086                         if (uncopied) {
2087                                 retval = -EFAULT;
2088                                 break;
2089                         }
2090                 }
2091
2092                 n_tty_check_unthrottle(tty);
2093
2094                 if (b - buf >= minimum)
2095                         break;
2096                 if (time)
2097                         timeout = time;
2098         }
2099         mutex_unlock(&ldata->atomic_read_lock);
2100         remove_wait_queue(&tty->read_wait, &wait);
2101
2102         if (!waitqueue_active(&tty->read_wait))
2103                 ldata->minimum_to_wake = minimum;
2104
2105         __set_current_state(TASK_RUNNING);
2106         if (b - buf)
2107                 retval = b - buf;
2108
2109         n_tty_set_room(tty);
2110         up_read(&tty->termios_rwsem);
2111         return retval;
2112 }
2113
2114 /**
2115  *      n_tty_write             -       write function for tty
2116  *      @tty: tty device
2117  *      @file: file object
2118  *      @buf: userspace buffer pointer
2119  *      @nr: size of I/O
2120  *
2121  *      Write function of the terminal device.  This is serialized with
2122  *      respect to other write callers but not to termios changes, reads
2123  *      and other such events.  Since the receive code will echo characters,
2124  *      thus calling driver write methods, the output_lock is used in
2125  *      the output processing functions called here as well as in the
2126  *      echo processing function to protect the column state and space
2127  *      left in the buffer.
2128  *
2129  *      This code must be sure never to sleep through a hangup.
2130  *
2131  *      Locking: output_lock to protect column state and space left
2132  *               (note that the process_output*() functions take this
2133  *                lock themselves)
2134  */
2135
2136 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2137                            const unsigned char *buf, size_t nr)
2138 {
2139         const unsigned char *b = buf;
2140         DECLARE_WAITQUEUE(wait, current);
2141         int c;
2142         ssize_t retval = 0;
2143
2144         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2145         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2146                 retval = tty_check_change(tty);
2147                 if (retval)
2148                         return retval;
2149         }
2150
2151         down_read(&tty->termios_rwsem);
2152
2153         /* Write out any echoed characters that are still pending */
2154         process_echoes(tty);
2155
2156         add_wait_queue(&tty->write_wait, &wait);
2157         while (1) {
2158                 set_current_state(TASK_INTERRUPTIBLE);
2159                 if (signal_pending(current)) {
2160                         retval = -ERESTARTSYS;
2161                         break;
2162                 }
2163                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2164                         retval = -EIO;
2165                         break;
2166                 }
2167                 if (O_OPOST(tty)) {
2168                         while (nr > 0) {
2169                                 ssize_t num = process_output_block(tty, b, nr);
2170                                 if (num < 0) {
2171                                         if (num == -EAGAIN)
2172                                                 break;
2173                                         retval = num;
2174                                         goto break_out;
2175                                 }
2176                                 b += num;
2177                                 nr -= num;
2178                                 if (nr == 0)
2179                                         break;
2180                                 c = *b;
2181                                 if (process_output(c, tty) < 0)
2182                                         break;
2183                                 b++; nr--;
2184                         }
2185                         if (tty->ops->flush_chars)
2186                                 tty->ops->flush_chars(tty);
2187                 } else {
2188                         while (nr > 0) {
2189                                 c = tty->ops->write(tty, b, nr);
2190                                 if (c < 0) {
2191                                         retval = c;
2192                                         goto break_out;
2193                                 }
2194                                 if (!c)
2195                                         break;
2196                                 b += c;
2197                                 nr -= c;
2198                         }
2199                 }
2200                 if (!nr)
2201                         break;
2202                 if (file->f_flags & O_NONBLOCK) {
2203                         retval = -EAGAIN;
2204                         break;
2205                 }
2206                 up_read(&tty->termios_rwsem);
2207
2208                 schedule();
2209
2210                 down_read(&tty->termios_rwsem);
2211         }
2212 break_out:
2213         __set_current_state(TASK_RUNNING);
2214         remove_wait_queue(&tty->write_wait, &wait);
2215         if (b - buf != nr && tty->fasync)
2216                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2217         up_read(&tty->termios_rwsem);
2218         return (b - buf) ? b - buf : retval;
2219 }
2220
2221 /**
2222  *      n_tty_poll              -       poll method for N_TTY
2223  *      @tty: terminal device
2224  *      @file: file accessing it
2225  *      @wait: poll table
2226  *
2227  *      Called when the line discipline is asked to poll() for data or
2228  *      for special events. This code is not serialized with respect to
2229  *      other events save open/close.
2230  *
2231  *      This code must be sure never to sleep through a hangup.
2232  *      Called without the kernel lock held - fine
2233  */
2234
2235 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2236                                                         poll_table *wait)
2237 {
2238         struct n_tty_data *ldata = tty->disc_data;
2239         unsigned int mask = 0;
2240
2241         poll_wait(file, &tty->read_wait, wait);
2242         poll_wait(file, &tty->write_wait, wait);
2243         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2244                 mask |= POLLIN | POLLRDNORM;
2245         if (tty->packet && tty->link->ctrl_status)
2246                 mask |= POLLPRI | POLLIN | POLLRDNORM;
2247         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2248                 mask |= POLLHUP;
2249         if (tty_hung_up_p(file))
2250                 mask |= POLLHUP;
2251         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2252                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2253                         ldata->minimum_to_wake = MIN_CHAR(tty);
2254                 else
2255                         ldata->minimum_to_wake = 1;
2256         }
2257         if (tty->ops->write && !tty_is_writelocked(tty) &&
2258                         tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2259                         tty_write_room(tty) > 0)
2260                 mask |= POLLOUT | POLLWRNORM;
2261         return mask;
2262 }
2263
2264 static unsigned long inq_canon(struct n_tty_data *ldata)
2265 {
2266         size_t nr, head, tail;
2267
2268         if (ldata->canon_head == ldata->read_tail)
2269                 return 0;
2270         head = ldata->canon_head;
2271         tail = ldata->read_tail;
2272         nr = head - tail;
2273         /* Skip EOF-chars.. */
2274         while (head != tail) {
2275                 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2276                     read_buf(ldata, tail) == __DISABLED_CHAR)
2277                         nr--;
2278                 tail++;
2279         }
2280         return nr;
2281 }
2282
2283 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2284                        unsigned int cmd, unsigned long arg)
2285 {
2286         struct n_tty_data *ldata = tty->disc_data;
2287         int retval;
2288
2289         switch (cmd) {
2290         case TIOCOUTQ:
2291                 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2292         case TIOCINQ:
2293                 down_write(&tty->termios_rwsem);
2294                 if (L_ICANON(tty))
2295                         retval = inq_canon(ldata);
2296                 else
2297                         retval = read_cnt(ldata);
2298                 up_write(&tty->termios_rwsem);
2299                 return put_user(retval, (unsigned int __user *) arg);
2300         default:
2301                 return n_tty_ioctl_helper(tty, file, cmd, arg);
2302         }
2303 }
2304
2305 static void n_tty_fasync(struct tty_struct *tty, int on)
2306 {
2307         struct n_tty_data *ldata = tty->disc_data;
2308
2309         if (!waitqueue_active(&tty->read_wait)) {
2310                 if (on)
2311                         ldata->minimum_to_wake = 1;
2312                 else if (!tty->fasync)
2313                         ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2314         }
2315 }
2316
2317 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2318         .magic           = TTY_LDISC_MAGIC,
2319         .name            = "n_tty",
2320         .open            = n_tty_open,
2321         .close           = n_tty_close,
2322         .flush_buffer    = n_tty_flush_buffer,
2323         .chars_in_buffer = n_tty_chars_in_buffer,
2324         .read            = n_tty_read,
2325         .write           = n_tty_write,
2326         .ioctl           = n_tty_ioctl,
2327         .set_termios     = n_tty_set_termios,
2328         .poll            = n_tty_poll,
2329         .receive_buf     = n_tty_receive_buf,
2330         .write_wakeup    = n_tty_write_wakeup,
2331         .fasync          = n_tty_fasync,
2332         .receive_buf2    = n_tty_receive_buf2,
2333 };
2334
2335 /**
2336  *      n_tty_inherit_ops       -       inherit N_TTY methods
2337  *      @ops: struct tty_ldisc_ops where to save N_TTY methods
2338  *
2339  *      Enables a 'subclass' line discipline to 'inherit' N_TTY
2340  *      methods.
2341  */
2342
2343 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2344 {
2345         *ops = tty_ldisc_N_TTY;
2346         ops->owner = NULL;
2347         ops->refcount = ops->flags = 0;
2348 }
2349 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);