drivers/char/n_tty.c

   1 /*
   2  * n_tty.c --- implements the N_TTY line discipline.
   3  *
   4  * This code used to be in tty_io.c, but things are getting hairy
   5  * enough that it made sense to split things off.  (The N_TTY
   6  * processing has changed so much that it's hardly recognizable,
   7  * anyway...)
   8  *
   9  * Note that the open routine for N_TTY is guaranteed never to return
  10  * an error.  This is because Linux will fall back to setting a line
  11  * to N_TTY if it can not switch to any other line discipline.
  12  *
  13  * Written by Theodore Ts'o, Copyright 1994.
  14  *
  15  * This file also contains code originally written by Linus Torvalds,
  16  * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
  17  *
  18  * This file may be redistributed under the terms of the GNU General Public
  19  * License.
  20  *
  21  * Reduced memory usage for older ARM systems  - Russell King.
  22  *
  23  * 2000/01/20   Fixed SMP locking on put_tty_queue using bits of
  24  *              the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
  25  *              who actually finally proved there really was a race.
  26  *
  27  * 2002/03/18   Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
  28  *              waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
  29  *              Also fixed a bug in BLOCKING mode where n_tty_write returns
  30  *              EAGAIN
  31  */
  32
  33 #include <linux/types.h>
  34 #include <linux/major.h>
  35 #include <linux/errno.h>
  36 #include <linux/signal.h>
  37 #include <linux/fcntl.h>
  38 #include <linux/sched.h>
  39 #include <linux/interrupt.h>
  40 #include <linux/tty.h>
  41 #include <linux/timer.h>
  42 #include <linux/ctype.h>
  43 #include <linux/mm.h>
  44 #include <linux/string.h>
  45 #include <linux/slab.h>
  46 #include <linux/poll.h>
  47 #include <linux/bitops.h>
  48 #include <linux/audit.h>
  49 #include <linux/file.h>
  50
  51 #include <asm/uaccess.h>
  52 #include <asm/system.h>
  53
  54 /* number of characters left in xmit buffer before select has we have room */
  55 #define WAKEUP_CHARS 256
  56
  57 /*
  58  * This defines the low- and high-watermarks for throttling and
  59  * unthrottling the TTY driver.  These watermarks are used for
  60  * controlling the space in the read buffer.
  61  */
  62 #define TTY_THRESHOLD_THROTTLE          128 /* now based on remaining room */
  63 #define TTY_THRESHOLD_UNTHROTTLE        128
  64
  65 static inline unsigned char *alloc_buf(void)
  66 {
  67         gfp_t prio = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
  68
  69         if (PAGE_SIZE != N_TTY_BUF_SIZE)
  70                 return kmalloc(N_TTY_BUF_SIZE, prio);
  71         else
  72                 return (unsigned char *)__get_free_page(prio);
  73 }
  74
  75 static inline void free_buf(unsigned char *buf)
  76 {
  77         if (PAGE_SIZE != N_TTY_BUF_SIZE)
  78                 kfree(buf);
  79         else
  80                 free_page((unsigned long) buf);
  81 }
  82
  83 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
  84                                unsigned char __user *ptr)
  85 {
  86         tty_audit_add_data(tty, &x, 1);
  87         return put_user(x, ptr);
  88 }
  89
  90 /**
  91  *      n_tty_set__room -       receive space
  92  *      @tty: terminal
  93  *
  94  *      Called by the driver to find out how much data it is
  95  *      permitted to feed to the line discipline without any being lost
  96  *      and thus to manage flow control. Not serialized. Answers for the
  97  *      "instant".
  98  */
  99
 100 static void n_tty_set_room(struct tty_struct *tty)
 101 {
 102         /* tty->read_cnt is not read locked ? */
 103         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
 104
 105         /*
 106          * If we are doing input canonicalization, and there are no
 107          * pending newlines, let characters through without limit, so
 108          * that erase characters will be handled.  Other excess
 109          * characters will be beeped.
 110          */
 111         if (left <= 0)
 112                 left = tty->icanon && !tty->canon_data;
 113         tty->receive_room = left;
 114 }
 115
 116 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
 117 {
 118         if (tty->read_cnt < N_TTY_BUF_SIZE) {
 119                 tty->read_buf[tty->read_head] = c;
 120                 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
 121                 tty->read_cnt++;
 122         }
 123 }
 124
 125 /**
 126  *      put_tty_queue           -       add character to tty
 127  *      @c: character
 128  *      @tty: tty device
 129  *
 130  *      Add a character to the tty read_buf queue. This is done under the
 131  *      read_lock to serialize character addition and also to protect us
 132  *      against parallel reads or flushes
 133  */
 134
 135 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
 136 {
 137         unsigned long flags;
 138         /*
 139          *      The problem of stomping on the buffers ends here.
 140          *      Why didn't anyone see this one coming? --AJK
 141         */
 142         spin_lock_irqsave(&tty->read_lock, flags);
 143         put_tty_queue_nolock(c, tty);
 144         spin_unlock_irqrestore(&tty->read_lock, flags);
 145 }
 146
 147 /**
 148  *      check_unthrottle        -       allow new receive data
 149  *      @tty; tty device
 150  *
 151  *      Check whether to call the driver unthrottle functions
 152  *
 153  *      Can sleep, may be called under the atomic_read_lock mutex but
 154  *      this is not guaranteed.
 155  */
 156 static void check_unthrottle(struct tty_struct *tty)
 157 {
 158         if (tty->count)
 159                 tty_unthrottle(tty);
 160 }
 161
 162 /**
 163  *      reset_buffer_flags      -       reset buffer state
 164  *      @tty: terminal to reset
 165  *
 166  *      Reset the read buffer counters, clear the flags,
 167  *      and make sure the driver is unthrottled. Called
 168  *      from n_tty_open() and n_tty_flush_buffer().
 169  *
 170  *      Locking: tty_read_lock for read fields.
 171  */
 172 static void reset_buffer_flags(struct tty_struct *tty)
 173 {
 174         unsigned long flags;
 175
 176         spin_lock_irqsave(&tty->read_lock, flags);
 177         tty->read_head = tty->read_tail = tty->read_cnt = 0;
 178         spin_unlock_irqrestore(&tty->read_lock, flags);
 179         tty->canon_head = tty->canon_data = tty->erasing = 0;
 180         memset(&tty->read_flags, 0, sizeof tty->read_flags);
 181         n_tty_set_room(tty);
 182         check_unthrottle(tty);
 183 }
 184
 185 /**
 186  *      n_tty_flush_buffer      -       clean input queue
 187  *      @tty:   terminal device
 188  *
 189  *      Flush the input buffer. Called when the line discipline is
 190  *      being closed, when the tty layer wants the buffer flushed (eg
 191  *      at hangup) or when the N_TTY line discipline internally has to
 192  *      clean the pending queue (for example some signals).
 193  *
 194  *      Locking: ctrl_lock, read_lock.
 195  */
 196
 197 static void n_tty_flush_buffer(struct tty_struct *tty)
 198 {
 199         unsigned long flags;
 200         /* clear everything and unthrottle the driver */
 201         reset_buffer_flags(tty);
 202
 203         if (!tty->link)
 204                 return;
 205
 206         spin_lock_irqsave(&tty->ctrl_lock, flags);
 207         if (tty->link->packet) {
 208                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
 209                 wake_up_interruptible(&tty->link->read_wait);
 210         }
 211         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 212 }
 213
 214 /**
 215  *      n_tty_chars_in_buffer   -       report available bytes
 216  *      @tty: tty device
 217  *
 218  *      Report the number of characters buffered to be delivered to user
 219  *      at this instant in time.
 220  *
 221  *      Locking: read_lock
 222  */
 223
 224 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
 225 {
 226         unsigned long flags;
 227         ssize_t n = 0;
 228
 229         spin_lock_irqsave(&tty->read_lock, flags);
 230         if (!tty->icanon) {
 231                 n = tty->read_cnt;
 232         } else if (tty->canon_data) {
 233                 n = (tty->canon_head > tty->read_tail) ?
 234                         tty->canon_head - tty->read_tail :
 235                         tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
 236         }
 237         spin_unlock_irqrestore(&tty->read_lock, flags);
 238         return n;
 239 }
 240
 241 /**
 242  *      is_utf8_continuation    -       utf8 multibyte check
 243  *      @c: byte to check
 244  *
 245  *      Returns true if the utf8 character 'c' is a multibyte continuation
 246  *      character. We use this to correctly compute the on screen size
 247  *      of the character when printing
 248  */
 249
 250 static inline int is_utf8_continuation(unsigned char c)
 251 {
 252         return (c & 0xc0) == 0x80;
 253 }
 254
 255 /**
 256  *      is_continuation         -       multibyte check
 257  *      @c: byte to check
 258  *
 259  *      Returns true if the utf8 character 'c' is a multibyte continuation
 260  *      character and the terminal is in unicode mode.
 261  */
 262
 263 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
 264 {
 265         return I_IUTF8(tty) && is_utf8_continuation(c);
 266 }
 267
 268 /**
 269  *      opost                   -       output post processor
 270  *      @c: character (or partial unicode symbol)
 271  *      @tty: terminal device
 272  *
 273  *      Perform OPOST processing.  Returns -1 when the output device is
 274  *      full and the character must be retried. Note that Linux currently
 275  *      ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY. They simply aren't
 276  *      relevant in the world today. If you ever need them, add them here.
 277  *
 278  *      Called from both the receive and transmit sides and can be called
 279  *      re-entrantly. Relies on lock_kernel() for tty->column state.
 280  */
 281
 282 static int opost(unsigned char c, struct tty_struct *tty)
 283 {
 284         int     space, spaces;
 285
 286         space = tty_write_room(tty);
 287         if (!space)
 288                 return -1;
 289
 290         lock_kernel();
 291         if (O_OPOST(tty)) {
 292                 switch (c) {
 293                 case '\n':
 294                         if (O_ONLRET(tty))
 295                                 tty->column = 0;
 296                         if (O_ONLCR(tty)) {
 297                                 if (space < 2) {
 298                                         unlock_kernel();
 299                                         return -1;
 300                                 }
 301                                 tty_put_char(tty, '\r');
 302                                 tty->column = 0;
 303                         }
 304                         tty->canon_column = tty->column;
 305                         break;
 306                 case '\r':
 307                         if (O_ONOCR(tty) && tty->column == 0) {
 308                                 unlock_kernel();
 309                                 return 0;
 310                         }
 311                         if (O_OCRNL(tty)) {
 312                                 c = '\n';
 313                                 if (O_ONLRET(tty))
 314                                         tty->canon_column = tty->column = 0;
 315                                 break;
 316                         }
 317                         tty->canon_column = tty->column = 0;
 318                         break;
 319                 case '\t':
 320                         spaces = 8 - (tty->column & 7);
 321                         if (O_TABDLY(tty) == XTABS) {
 322                                 if (space < spaces) {
 323                                         unlock_kernel();
 324                                         return -1;
 325                                 }
 326                                 tty->column += spaces;
 327                                 tty->ops->write(tty, "        ", spaces);
 328                                 unlock_kernel();
 329                                 return 0;
 330                         }
 331                         tty->column += spaces;
 332                         break;
 333                 case '\b':
 334                         if (tty->column > 0)
 335                                 tty->column--;
 336                         break;
 337                 default:
 338                         if (O_OLCUC(tty))
 339                                 c = toupper(c);
 340                         if (!iscntrl(c) && !is_continuation(c, tty))
 341                                 tty->column++;
 342                         break;
 343                 }
 344         }
 345         tty_put_char(tty, c);
 346         unlock_kernel();
 347         return 0;
 348 }
 349
 350 /**
 351  *      opost_block             -       block postprocess
 352  *      @tty: terminal device
 353  *      @inbuf: user buffer
 354  *      @nr: number of bytes
 355  *
 356  *      This path is used to speed up block console writes, among other
 357  *      things when processing blocks of output data. It handles only
 358  *      the simple cases normally found and helps to generate blocks of
 359  *      symbols for the console driver and thus improve performance.
 360  *
 361  *      Called from n_tty_write under the tty layer write lock. Relies
 362  *      on lock_kernel for the tty->column state.
 363  */
 364
 365 static ssize_t opost_block(struct tty_struct *tty,
 366                        const unsigned char *buf, unsigned int nr)
 367 {
 368         int     space;
 369         int     i;
 370         const unsigned char *cp;
 371
 372         space = tty_write_room(tty);
 373         if (!space)
 374                 return 0;
 375         if (nr > space)
 376                 nr = space;
 377
 378         lock_kernel();
 379         for (i = 0, cp = buf; i < nr; i++, cp++) {
 380                 switch (*cp) {
 381                 case '\n':
 382                         if (O_ONLRET(tty))
 383                                 tty->column = 0;
 384                         if (O_ONLCR(tty))
 385                                 goto break_out;
 386                         tty->canon_column = tty->column;
 387                         break;
 388                 case '\r':
 389                         if (O_ONOCR(tty) && tty->column == 0)
 390                                 goto break_out;
 391                         if (O_OCRNL(tty))
 392                                 goto break_out;
 393                         tty->canon_column = tty->column = 0;
 394                         break;
 395                 case '\t':
 396                         goto break_out;
 397                 case '\b':
 398                         if (tty->column > 0)
 399                                 tty->column--;
 400                         break;
 401                 default:
 402                         if (O_OLCUC(tty))
 403                                 goto break_out;
 404                         if (!iscntrl(*cp))
 405                                 tty->column++;
 406                         break;
 407                 }
 408         }
 409 break_out:
 410         if (tty->ops->flush_chars)
 411                 tty->ops->flush_chars(tty);
 412         i = tty->ops->write(tty, buf, i);
 413         unlock_kernel();
 414         return i;
 415 }
 416
 417
 418 /**
 419  *      echo_char       -       echo characters
 420  *      @c: unicode byte to echo
 421  *      @tty: terminal device
 422  *
 423  *      Echo user input back onto the screen. This must be called only when
 424  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
 425  *
 426  *      Relies on BKL for tty column locking
 427  */
 428
 429 static void echo_char(unsigned char c, struct tty_struct *tty)
 430 {
 431         if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') {
 432                 tty_put_char(tty, '^');
 433                 tty_put_char(tty, c ^ 0100);
 434                 tty->column += 2;
 435         } else
 436                 opost(c, tty);
 437 }
 438
 439 /**
 440  *      finsh_erasing           -       complete erase
 441  *      @tty: tty doing the erase
 442  *
 443  *      Relies on BKL for tty column locking
 444  */
 445 static inline void finish_erasing(struct tty_struct *tty)
 446 {
 447         if (tty->erasing) {
 448                 tty_put_char(tty, '/');
 449                 tty->column++;
 450                 tty->erasing = 0;
 451         }
 452 }
 453
 454 /**
 455  *      eraser          -       handle erase function
 456  *      @c: character input
 457  *      @tty: terminal device
 458  *
 459  *      Perform erase and necessary output when an erase character is
 460  *      present in the stream from the driver layer. Handles the complexities
 461  *      of UTF-8 multibyte symbols.
 462  *
 463  *      Locking: read_lock for tty buffers, BKL for column/erasing state
 464  */
 465
 466 static void eraser(unsigned char c, struct tty_struct *tty)
 467 {
 468         enum { ERASE, WERASE, KILL } kill_type;
 469         int head, seen_alnums, cnt;
 470         unsigned long flags;
 471
 472         /* FIXME: locking needed ? */
 473         if (tty->read_head == tty->canon_head) {
 474                 /* opost('\a', tty); */         /* what do you think? */
 475                 return;
 476         }
 477         if (c == ERASE_CHAR(tty))
 478                 kill_type = ERASE;
 479         else if (c == WERASE_CHAR(tty))
 480                 kill_type = WERASE;
 481         else {
 482                 if (!L_ECHO(tty)) {
 483                         spin_lock_irqsave(&tty->read_lock, flags);
 484                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 485                                           (N_TTY_BUF_SIZE - 1));
 486                         tty->read_head = tty->canon_head;
 487                         spin_unlock_irqrestore(&tty->read_lock, flags);
 488                         return;
 489                 }
 490                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
 491                         spin_lock_irqsave(&tty->read_lock, flags);
 492                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 493                                           (N_TTY_BUF_SIZE - 1));
 494                         tty->read_head = tty->canon_head;
 495                         spin_unlock_irqrestore(&tty->read_lock, flags);
 496                         finish_erasing(tty);
 497                         echo_char(KILL_CHAR(tty), tty);
 498                         /* Add a newline if ECHOK is on and ECHOKE is off. */
 499                         if (L_ECHOK(tty))
 500                                 opost('\n', tty);
 501                         return;
 502                 }
 503                 kill_type = KILL;
 504         }
 505
 506         seen_alnums = 0;
 507         /* FIXME: Locking ?? */
 508         while (tty->read_head != tty->canon_head) {
 509                 head = tty->read_head;
 510
 511                 /* erase a single possibly multibyte character */
 512                 do {
 513                         head = (head - 1) & (N_TTY_BUF_SIZE-1);
 514                         c = tty->read_buf[head];
 515                 } while (is_continuation(c, tty) && head != tty->canon_head);
 516
 517                 /* do not partially erase */
 518                 if (is_continuation(c, tty))
 519                         break;
 520
 521                 if (kill_type == WERASE) {
 522                         /* Equivalent to BSD's ALTWERASE. */
 523                         if (isalnum(c) || c == '_')
 524                                 seen_alnums++;
 525                         else if (seen_alnums)
 526                                 break;
 527                 }
 528                 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
 529                 spin_lock_irqsave(&tty->read_lock, flags);
 530                 tty->read_head = head;
 531                 tty->read_cnt -= cnt;
 532                 spin_unlock_irqrestore(&tty->read_lock, flags);
 533                 if (L_ECHO(tty)) {
 534                         if (L_ECHOPRT(tty)) {
 535                                 if (!tty->erasing) {
 536                                         tty_put_char(tty, '\\');
 537                                         tty->column++;
 538                                         tty->erasing = 1;
 539                                 }
 540                                 /* if cnt > 1, output a multi-byte character */
 541                                 echo_char(c, tty);
 542                                 while (--cnt > 0) {
 543                                         head = (head+1) & (N_TTY_BUF_SIZE-1);
 544                                         tty_put_char(tty, tty->read_buf[head]);
 545                                 }
 546                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
 547                                 echo_char(ERASE_CHAR(tty), tty);
 548                         } else if (c == '\t') {
 549                                 unsigned int col = tty->canon_column;
 550                                 unsigned long tail = tty->canon_head;
 551
 552                                 /* Find the column of the last char. */
 553                                 while (tail != tty->read_head) {
 554                                         c = tty->read_buf[tail];
 555                                         if (c == '\t')
 556                                                 col = (col | 7) + 1;
 557                                         else if (iscntrl(c)) {
 558                                                 if (L_ECHOCTL(tty))
 559                                                         col += 2;
 560                                         } else if (!is_continuation(c, tty))
 561                                                 col++;
 562                                         tail = (tail+1) & (N_TTY_BUF_SIZE-1);
 563                                 }
 564
 565                                 /* should never happen */
 566                                 if (tty->column > 0x80000000)
 567                                         tty->column = 0;
 568
 569                                 /* Now backup to that column. */
 570                                 while (tty->column > col) {
 571                                         /* Can't use opost here. */
 572                                         tty_put_char(tty, '\b');
 573                                         if (tty->column > 0)
 574                                                 tty->column--;
 575                                 }
 576                         } else {
 577                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
 578                                         tty_put_char(tty, '\b');
 579                                         tty_put_char(tty, ' ');
 580                                         tty_put_char(tty, '\b');
 581                                         if (tty->column > 0)
 582                                                 tty->column--;
 583                                 }
 584                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
 585                                         tty_put_char(tty, '\b');
 586                                         tty_put_char(tty, ' ');
 587                                         tty_put_char(tty, '\b');
 588                                         if (tty->column > 0)
 589                                                 tty->column--;
 590                                 }
 591                         }
 592                 }
 593                 if (kill_type == ERASE)
 594                         break;
 595         }
 596         if (tty->read_head == tty->canon_head)
 597                 finish_erasing(tty);
 598 }
 599
 600 /**
 601  *      isig            -       handle the ISIG optio
 602  *      @sig: signal
 603  *      @tty: terminal
 604  *      @flush: force flush
 605  *
 606  *      Called when a signal is being sent due to terminal input. This
 607  *      may caus terminal flushing to take place according to the termios
 608  *      settings and character used. Called from the driver receive_buf
 609  *      path so serialized.
 610  *
 611  *      Locking: ctrl_lock, read_lock (both via flush buffer)
 612  */
 613
 614 static inline void isig(int sig, struct tty_struct *tty, int flush)
 615 {
 616         if (tty->pgrp)
 617                 kill_pgrp(tty->pgrp, sig, 1);
 618         if (flush || !L_NOFLSH(tty)) {
 619                 n_tty_flush_buffer(tty);
 620                 tty_driver_flush_buffer(tty);
 621         }
 622 }
 623
 624 /**
 625  *      n_tty_receive_break     -       handle break
 626  *      @tty: terminal
 627  *
 628  *      An RS232 break event has been hit in the incoming bitstream. This
 629  *      can cause a variety of events depending upon the termios settings.
 630  *
 631  *      Called from the receive_buf path so single threaded.
 632  */
 633
 634 static inline void n_tty_receive_break(struct tty_struct *tty)
 635 {
 636         if (I_IGNBRK(tty))
 637                 return;
 638         if (I_BRKINT(tty)) {
 639                 isig(SIGINT, tty, 1);
 640                 return;
 641         }
 642         if (I_PARMRK(tty)) {
 643                 put_tty_queue('\377', tty);
 644                 put_tty_queue('\0', tty);
 645         }
 646         put_tty_queue('\0', tty);
 647         wake_up_interruptible(&tty->read_wait);
 648 }
 649
 650 /**
 651  *      n_tty_receive_overrun   -       handle overrun reporting
 652  *      @tty: terminal
 653  *
 654  *      Data arrived faster than we could process it. While the tty
 655  *      driver has flagged this the bits that were missed are gone
 656  *      forever.
 657  *
 658  *      Called from the receive_buf path so single threaded. Does not
 659  *      need locking as num_overrun and overrun_time are function
 660  *      private.
 661  */
 662
 663 static inline void n_tty_receive_overrun(struct tty_struct *tty)
 664 {
 665         char buf[64];
 666
 667         tty->num_overrun++;
 668         if (time_before(tty->overrun_time, jiffies - HZ) ||
 669                         time_after(tty->overrun_time, jiffies)) {
 670                 printk(KERN_WARNING "%s: %d input overrun(s)\n",
 671                         tty_name(tty, buf),
 672                         tty->num_overrun);
 673                 tty->overrun_time = jiffies;
 674                 tty->num_overrun = 0;
 675         }
 676 }
 677
 678 /**
 679  *      n_tty_receive_parity_error      -       error notifier
 680  *      @tty: terminal device
 681  *      @c: character
 682  *
 683  *      Process a parity error and queue the right data to indicate
 684  *      the error case if necessary. Locking as per n_tty_receive_buf.
 685  */
 686 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
 687                                               unsigned char c)
 688 {
 689         if (I_IGNPAR(tty))
 690                 return;
 691         if (I_PARMRK(tty)) {
 692                 put_tty_queue('\377', tty);
 693                 put_tty_queue('\0', tty);
 694                 put_tty_queue(c, tty);
 695         } else  if (I_INPCK(tty))
 696                 put_tty_queue('\0', tty);
 697         else
 698                 put_tty_queue(c, tty);
 699         wake_up_interruptible(&tty->read_wait);
 700 }
 701
 702 /**
 703  *      n_tty_receive_char      -       perform processing
 704  *      @tty: terminal device
 705  *      @c: character
 706  *
 707  *      Process an individual character of input received from the driver.
 708  *      This is serialized with respect to itself by the rules for the
 709  *      driver above.
 710  */
 711
 712 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 713 {
 714         unsigned long flags;
 715
 716         if (tty->raw) {
 717                 put_tty_queue(c, tty);
 718                 return;
 719         }
 720
 721         if (I_ISTRIP(tty))
 722                 c &= 0x7f;
 723         if (I_IUCLC(tty) && L_IEXTEN(tty))
 724                 c=tolower(c);
 725
 726         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
 727             ((I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty)) ||
 728              c == INTR_CHAR(tty) || c == QUIT_CHAR(tty) || c == SUSP_CHAR(tty)))
 729                 start_tty(tty);
 730
 731         if (tty->closing) {
 732                 if (I_IXON(tty)) {
 733                         if (c == START_CHAR(tty))
 734                                 start_tty(tty);
 735                         else if (c == STOP_CHAR(tty))
 736                                 stop_tty(tty);
 737                 }
 738                 return;
 739         }
 740
 741         /*
 742          * If the previous character was LNEXT, or we know that this
 743          * character is not one of the characters that we'll have to
 744          * handle specially, do shortcut processing to speed things
 745          * up.
 746          */
 747         if (!test_bit(c, tty->process_char_map) || tty->lnext) {
 748                 finish_erasing(tty);
 749                 tty->lnext = 0;
 750                 if (L_ECHO(tty)) {
 751                         if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
 752                                 tty_put_char(tty, '\a'); /* beep if no space */
 753                                 return;
 754                         }
 755                         /* Record the column of first canon char. */
 756                         if (tty->canon_head == tty->read_head)
 757                                 tty->canon_column = tty->column;
 758                         echo_char(c, tty);
 759                 }
 760                 if (I_PARMRK(tty) && c == (unsigned char) '\377')
 761                         put_tty_queue(c, tty);
 762                 put_tty_queue(c, tty);
 763                 return;
 764         }
 765
 766         if (I_IXON(tty)) {
 767                 if (c == START_CHAR(tty)) {
 768                         start_tty(tty);
 769                         return;
 770                 }
 771                 if (c == STOP_CHAR(tty)) {
 772                         stop_tty(tty);
 773                         return;
 774                 }
 775         }
 776
 777         if (L_ISIG(tty)) {
 778                 int signal;
 779                 signal = SIGINT;
 780                 if (c == INTR_CHAR(tty))
 781                         goto send_signal;
 782                 signal = SIGQUIT;
 783                 if (c == QUIT_CHAR(tty))
 784                         goto send_signal;
 785                 signal = SIGTSTP;
 786                 if (c == SUSP_CHAR(tty)) {
 787 send_signal:
 788                         /*
 789                          * Echo character, and then send the signal.
 790                          * Note that we do not use isig() here because we want
 791                          * the order to be:
 792                          * 1) flush, 2) echo, 3) signal
 793                          */
 794                         if (!L_NOFLSH(tty)) {
 795                                 n_tty_flush_buffer(tty);
 796                                 tty_driver_flush_buffer(tty);
 797                         }
 798                         if (L_ECHO(tty))
 799                                 echo_char(c, tty);
 800                         if (tty->pgrp)
 801                                 kill_pgrp(tty->pgrp, signal, 1);
 802                         return;
 803                 }
 804         }
 805
 806         if (c == '\r') {
 807                 if (I_IGNCR(tty))
 808                         return;
 809                 if (I_ICRNL(tty))
 810                         c = '\n';
 811         } else if (c == '\n' && I_INLCR(tty))
 812                 c = '\r';
 813
 814         if (tty->icanon) {
 815                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
 816                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
 817                         eraser(c, tty);
 818                         return;
 819                 }
 820                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
 821                         tty->lnext = 1;
 822                         if (L_ECHO(tty)) {
 823                                 finish_erasing(tty);
 824                                 if (L_ECHOCTL(tty)) {
 825                                         tty_put_char(tty, '^');
 826                                         tty_put_char(tty, '\b');
 827                                 }
 828                         }
 829                         return;
 830                 }
 831                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
 832                     L_IEXTEN(tty)) {
 833                         unsigned long tail = tty->canon_head;
 834
 835                         finish_erasing(tty);
 836                         echo_char(c, tty);
 837                         opost('\n', tty);
 838                         while (tail != tty->read_head) {
 839                                 echo_char(tty->read_buf[tail], tty);
 840                                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
 841                         }
 842                         return;
 843                 }
 844                 if (c == '\n') {
 845                         if (L_ECHO(tty) || L_ECHONL(tty)) {
 846                                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
 847                                         tty_put_char(tty, '\a');
 848                                 opost('\n', tty);
 849                         }
 850                         goto handle_newline;
 851                 }
 852                 if (c == EOF_CHAR(tty)) {
 853                         if (tty->canon_head != tty->read_head)
 854                                 set_bit(TTY_PUSH, &tty->flags);
 855                         c = __DISABLED_CHAR;
 856                         goto handle_newline;
 857                 }
 858                 if ((c == EOL_CHAR(tty)) ||
 859                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
 860                         /*
 861                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
 862                          */
 863                         if (L_ECHO(tty)) {
 864                                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
 865                                         tty_put_char(tty, '\a');
 866                                 /* Record the column of first canon char. */
 867                                 if (tty->canon_head == tty->read_head)
 868                                         tty->canon_column = tty->column;
 869                                 echo_char(c, tty);
 870                         }
 871                         /*
 872                          * XXX does PARMRK doubling happen for
 873                          * EOL_CHAR and EOL2_CHAR?
 874                          */
 875                         if (I_PARMRK(tty) && c == (unsigned char) '\377')
 876                                 put_tty_queue(c, tty);
 877
 878 handle_newline:
 879                         spin_lock_irqsave(&tty->read_lock, flags);
 880                         set_bit(tty->read_head, tty->read_flags);
 881                         put_tty_queue_nolock(c, tty);
 882                         tty->canon_head = tty->read_head;
 883                         tty->canon_data++;
 884                         spin_unlock_irqrestore(&tty->read_lock, flags);
 885                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
 886                         if (waitqueue_active(&tty->read_wait))
 887                                 wake_up_interruptible(&tty->read_wait);
 888                         return;
 889                 }
 890         }
 891
 892         finish_erasing(tty);
 893         if (L_ECHO(tty)) {
 894                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
 895                         tty_put_char(tty, '\a'); /* beep if no space */
 896                         return;
 897                 }
 898                 if (c == '\n')
 899                         opost('\n', tty);
 900                 else {
 901                         /* Record the column of first canon char. */
 902                         if (tty->canon_head == tty->read_head)
 903                                 tty->canon_column = tty->column;
 904                         echo_char(c, tty);
 905                 }
 906         }
 907
 908         if (I_PARMRK(tty) && c == (unsigned char) '\377')
 909                 put_tty_queue(c, tty);
 910
 911         put_tty_queue(c, tty);
 912 }
 913
 914
 915 /**
 916  *      n_tty_write_wakeup      -       asynchronous I/O notifier
 917  *      @tty: tty device
 918  *
 919  *      Required for the ptys, serial driver etc. since processes
 920  *      that attach themselves to the master and rely on ASYNC
 921  *      IO must be woken up
 922  */
 923
 924 static void n_tty_write_wakeup(struct tty_struct *tty)
 925 {
 926         if (tty->fasync) {
 927                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 928                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
 929         }
 930 }
 931
 932 /**
 933  *      n_tty_receive_buf       -       data receive
 934  *      @tty: terminal device
 935  *      @cp: buffer
 936  *      @fp: flag buffer
 937  *      @count: characters
 938  *
 939  *      Called by the terminal driver when a block of characters has
 940  *      been received. This function must be called from soft contexts
 941  *      not from interrupt context. The driver is responsible for making
 942  *      calls one at a time and in order (or using flush_to_ldisc)
 943  */
 944
 945 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 946                               char *fp, int count)
 947 {
 948         const unsigned char *p;
 949         char *f, flags = TTY_NORMAL;
 950         int     i;
 951         char    buf[64];
 952         unsigned long cpuflags;
 953
 954         if (!tty->read_buf)
 955                 return;
 956
 957         if (tty->real_raw) {
 958                 spin_lock_irqsave(&tty->read_lock, cpuflags);
 959                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
 960                         N_TTY_BUF_SIZE - tty->read_head);
 961                 i = min(count, i);
 962                 memcpy(tty->read_buf + tty->read_head, cp, i);
 963                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
 964                 tty->read_cnt += i;
 965                 cp += i;
 966                 count -= i;
 967
 968                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
 969                         N_TTY_BUF_SIZE - tty->read_head);
 970                 i = min(count, i);
 971                 memcpy(tty->read_buf + tty->read_head, cp, i);
 972                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
 973                 tty->read_cnt += i;
 974                 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
 975         } else {
 976                 for (i = count, p = cp, f = fp; i; i--, p++) {
 977                         if (f)
 978                                 flags = *f++;
 979                         switch (flags) {
 980                         case TTY_NORMAL:
 981                                 n_tty_receive_char(tty, *p);
 982                                 break;
 983                         case TTY_BREAK:
 984                                 n_tty_receive_break(tty);
 985                                 break;
 986                         case TTY_PARITY:
 987                         case TTY_FRAME:
 988                                 n_tty_receive_parity_error(tty, *p);
 989                                 break;
 990                         case TTY_OVERRUN:
 991                                 n_tty_receive_overrun(tty);
 992                                 break;
 993                         default:
 994                                 printk(KERN_ERR "%s: unknown flag %d\n",
 995                                        tty_name(tty, buf), flags);
 996                                 break;
 997                         }
 998                 }
 999                 if (tty->ops->flush_chars)
1000                         tty->ops->flush_chars(tty);
1001         }
1002
1003         n_tty_set_room(tty);
1004
1005         if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
1006                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1007                 if (waitqueue_active(&tty->read_wait))
1008                         wake_up_interruptible(&tty->read_wait);
1009         }
1010
1011         /*
1012          * Check the remaining room for the input canonicalization
1013          * mode.  We don't want to throttle the driver if we're in
1014          * canonical mode and don't have a newline yet!
1015          */
1016         if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1017                 tty_throttle(tty);
1018 }
1019
1020 int is_ignored(int sig)
1021 {
1022         return (sigismember(&current->blocked, sig) ||
1023                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1024 }
1025
1026 /**
1027  *      n_tty_set_termios       -       termios data changed
1028  *      @tty: terminal
1029  *      @old: previous data
1030  *
1031  *      Called by the tty layer when the user changes termios flags so
1032  *      that the line discipline can plan ahead. This function cannot sleep
1033  *      and is protected from re-entry by the tty layer. The user is
1034  *      guaranteed that this function will not be re-entered or in progress
1035  *      when the ldisc is closed.
1036  *
1037  *      Locking: Caller holds tty->termios_mutex
1038  */
1039
1040 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1041 {
1042         int canon_change = 1;
1043         BUG_ON(!tty);
1044
1045         if (old)
1046                 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1047         if (canon_change) {
1048                 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1049                 tty->canon_head = tty->read_tail;
1050                 tty->canon_data = 0;
1051                 tty->erasing = 0;
1052         }
1053
1054         if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1055                 wake_up_interruptible(&tty->read_wait);
1056
1057         tty->icanon = (L_ICANON(tty) != 0);
1058         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1059                 tty->raw = 1;
1060                 tty->real_raw = 1;
1061                 n_tty_set_room(tty);
1062                 return;
1063         }
1064         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1065             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1066             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1067             I_PARMRK(tty)) {
1068                 memset(tty->process_char_map, 0, 256/8);
1069
1070                 if (I_IGNCR(tty) || I_ICRNL(tty))
1071                         set_bit('\r', tty->process_char_map);
1072                 if (I_INLCR(tty))
1073                         set_bit('\n', tty->process_char_map);
1074
1075                 if (L_ICANON(tty)) {
1076                         set_bit(ERASE_CHAR(tty), tty->process_char_map);
1077                         set_bit(KILL_CHAR(tty), tty->process_char_map);
1078                         set_bit(EOF_CHAR(tty), tty->process_char_map);
1079                         set_bit('\n', tty->process_char_map);
1080                         set_bit(EOL_CHAR(tty), tty->process_char_map);
1081                         if (L_IEXTEN(tty)) {
1082                                 set_bit(WERASE_CHAR(tty),
1083                                         tty->process_char_map);
1084                                 set_bit(LNEXT_CHAR(tty),
1085                                         tty->process_char_map);
1086                                 set_bit(EOL2_CHAR(tty),
1087                                         tty->process_char_map);
1088                                 if (L_ECHO(tty))
1089                                         set_bit(REPRINT_CHAR(tty),
1090                                                 tty->process_char_map);
1091                         }
1092                 }
1093                 if (I_IXON(tty)) {
1094                         set_bit(START_CHAR(tty), tty->process_char_map);
1095                         set_bit(STOP_CHAR(tty), tty->process_char_map);
1096                 }
1097                 if (L_ISIG(tty)) {
1098                         set_bit(INTR_CHAR(tty), tty->process_char_map);
1099                         set_bit(QUIT_CHAR(tty), tty->process_char_map);
1100                         set_bit(SUSP_CHAR(tty), tty->process_char_map);
1101                 }
1102                 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1103                 tty->raw = 0;
1104                 tty->real_raw = 0;
1105         } else {
1106                 tty->raw = 1;
1107                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1108                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1109                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1110                         tty->real_raw = 1;
1111                 else
1112                         tty->real_raw = 0;
1113         }
1114         n_tty_set_room(tty);
1115         /* The termios change make the tty ready for I/O */
1116         wake_up_interruptible(&tty->write_wait);
1117         wake_up_interruptible(&tty->read_wait);
1118 }
1119
1120 /**
1121  *      n_tty_close             -       close the ldisc for this tty
1122  *      @tty: device
1123  *
1124  *      Called from the terminal layer when this line discipline is
1125  *      being shut down, either because of a close or becsuse of a
1126  *      discipline change. The function will not be called while other
1127  *      ldisc methods are in progress.
1128  */
1129
1130 static void n_tty_close(struct tty_struct *tty)
1131 {
1132         n_tty_flush_buffer(tty);
1133         if (tty->read_buf) {
1134                 free_buf(tty->read_buf);
1135                 tty->read_buf = NULL;
1136         }
1137 }
1138
1139 /**
1140  *      n_tty_open              -       open an ldisc
1141  *      @tty: terminal to open
1142  *
1143  *      Called when this line discipline is being attached to the
1144  *      terminal device. Can sleep. Called serialized so that no
1145  *      other events will occur in parallel. No further open will occur
1146  *      until a close.
1147  */
1148
1149 static int n_tty_open(struct tty_struct *tty)
1150 {
1151         if (!tty)
1152                 return -EINVAL;
1153
1154         /* This one is ugly. Currently a malloc failure here can panic */
1155         if (!tty->read_buf) {
1156                 tty->read_buf = alloc_buf();
1157                 if (!tty->read_buf)
1158                         return -ENOMEM;
1159         }
1160         memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
1161         reset_buffer_flags(tty);
1162         tty->column = 0;
1163         n_tty_set_termios(tty, NULL);
1164         tty->minimum_to_wake = 1;
1165         tty->closing = 0;
1166         return 0;
1167 }
1168
1169 static inline int input_available_p(struct tty_struct *tty, int amt)
1170 {
1171         if (tty->icanon) {
1172                 if (tty->canon_data)
1173                         return 1;
1174         } else if (tty->read_cnt >= (amt ? amt : 1))
1175                 return 1;
1176
1177         return 0;
1178 }
1179
1180 /**
1181  *      copy_from_read_buf      -       copy read data directly
1182  *      @tty: terminal device
1183  *      @b: user data
1184  *      @nr: size of data
1185  *
1186  *      Helper function to speed up n_tty_read.  It is only called when
1187  *      ICANON is off; it copies characters straight from the tty queue to
1188  *      user space directly.  It can be profitably called twice; once to
1189  *      drain the space from the tail pointer to the (physical) end of the
1190  *      buffer, and once to drain the space from the (physical) beginning of
1191  *      the buffer to head pointer.
1192  *
1193  *      Called under the tty->atomic_read_lock sem
1194  *
1195  */
1196
1197 static int copy_from_read_buf(struct tty_struct *tty,
1198                                       unsigned char __user **b,
1199                                       size_t *nr)
1200
1201 {
1202         int retval;
1203         size_t n;
1204         unsigned long flags;
1205
1206         retval = 0;
1207         spin_lock_irqsave(&tty->read_lock, flags);
1208         n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1209         n = min(*nr, n);
1210         spin_unlock_irqrestore(&tty->read_lock, flags);
1211         if (n) {
1212                 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1213                 n -= retval;
1214                 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1215                 spin_lock_irqsave(&tty->read_lock, flags);
1216                 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1217                 tty->read_cnt -= n;
1218                 spin_unlock_irqrestore(&tty->read_lock, flags);
1219                 *b += n;
1220                 *nr -= n;
1221         }
1222         return retval;
1223 }
1224
1225 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1226                                                         size_t, loff_t *);
1227
1228 /**
1229  *      job_control             -       check job control
1230  *      @tty: tty
1231  *      @file: file handle
1232  *
1233  *      Perform job control management checks on this file/tty descriptor
1234  *      and if appropriate send any needed signals and return a negative
1235  *      error code if action should be taken.
1236  *
1237  *      FIXME:
1238  *      Locking: None - redirected write test is safe, testing
1239  *      current->signal should possibly lock current->sighand
1240  *      pgrp locking ?
1241  */
1242
1243 static int job_control(struct tty_struct *tty, struct file *file)
1244 {
1245         /* Job control check -- must be done at start and after
1246            every sleep (POSIX.1 7.1.1.4). */
1247         /* NOTE: not yet done after every sleep pending a thorough
1248            check of the logic of this change. -- jlc */
1249         /* don't stop on /dev/console */
1250         if (file->f_op->write != redirected_tty_write &&
1251             current->signal->tty == tty) {
1252                 if (!tty->pgrp)
1253                         printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1254                 else if (task_pgrp(current) != tty->pgrp) {
1255                         if (is_ignored(SIGTTIN) ||
1256                             is_current_pgrp_orphaned())
1257                                 return -EIO;
1258                         kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1259                         set_thread_flag(TIF_SIGPENDING);
1260                         return -ERESTARTSYS;
1261                 }
1262         }
1263         return 0;
1264 }
1265
1266
1267 /**
1268  *      n_tty_read              -       read function for tty
1269  *      @tty: tty device
1270  *      @file: file object
1271  *      @buf: userspace buffer pointer
1272  *      @nr: size of I/O
1273  *
1274  *      Perform reads for the line discipline. We are guaranteed that the
1275  *      line discipline will not be closed under us but we may get multiple
1276  *      parallel readers and must handle this ourselves. We may also get
1277  *      a hangup. Always called in user context, may sleep.
1278  *
1279  *      This code must be sure never to sleep through a hangup.
1280  */
1281
1282 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1283                          unsigned char __user *buf, size_t nr)
1284 {
1285         unsigned char __user *b = buf;
1286         DECLARE_WAITQUEUE(wait, current);
1287         int c;
1288         int minimum, time;
1289         ssize_t retval = 0;
1290         ssize_t size;
1291         long timeout;
1292         unsigned long flags;
1293         int packet;
1294
1295 do_it_again:
1296
1297         BUG_ON(!tty->read_buf);
1298
1299         c = job_control(tty, file);
1300         if (c < 0)
1301                 return c;
1302
1303         minimum = time = 0;
1304         timeout = MAX_SCHEDULE_TIMEOUT;
1305         if (!tty->icanon) {
1306                 time = (HZ / 10) * TIME_CHAR(tty);
1307                 minimum = MIN_CHAR(tty);
1308                 if (minimum) {
1309                         if (time)
1310                                 tty->minimum_to_wake = 1;
1311                         else if (!waitqueue_active(&tty->read_wait) ||
1312                                  (tty->minimum_to_wake > minimum))
1313                                 tty->minimum_to_wake = minimum;
1314                 } else {
1315                         timeout = 0;
1316                         if (time) {
1317                                 timeout = time;
1318                                 time = 0;
1319                         }
1320                         tty->minimum_to_wake = minimum = 1;
1321                 }
1322         }
1323
1324         /*
1325          *      Internal serialization of reads.
1326          */
1327         if (file->f_flags & O_NONBLOCK) {
1328                 if (!mutex_trylock(&tty->atomic_read_lock))
1329                         return -EAGAIN;
1330         } else {
1331                 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1332                         return -ERESTARTSYS;
1333         }
1334         packet = tty->packet;
1335
1336         add_wait_queue(&tty->read_wait, &wait);
1337         while (nr) {
1338                 /* First test for status change. */
1339                 if (packet && tty->link->ctrl_status) {
1340                         unsigned char cs;
1341                         if (b != buf)
1342                                 break;
1343                         spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1344                         cs = tty->link->ctrl_status;
1345                         tty->link->ctrl_status = 0;
1346                         spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1347                         if (tty_put_user(tty, cs, b++)) {
1348                                 retval = -EFAULT;
1349                                 b--;
1350                                 break;
1351                         }
1352                         nr--;
1353                         break;
1354                 }
1355                 /* This statement must be first before checking for input
1356                    so that any interrupt will set the state back to
1357                    TASK_RUNNING. */
1358                 set_current_state(TASK_INTERRUPTIBLE);
1359
1360                 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1361                     ((minimum - (b - buf)) >= 1))
1362                         tty->minimum_to_wake = (minimum - (b - buf));
1363
1364                 if (!input_available_p(tty, 0)) {
1365                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1366                                 retval = -EIO;
1367                                 break;
1368                         }
1369                         if (tty_hung_up_p(file))
1370                                 break;
1371                         if (!timeout)
1372                                 break;
1373                         if (file->f_flags & O_NONBLOCK) {
1374                                 retval = -EAGAIN;
1375                                 break;
1376                         }
1377                         if (signal_pending(current)) {
1378                                 retval = -ERESTARTSYS;
1379                                 break;
1380                         }
1381                         /* FIXME: does n_tty_set_room need locking ? */
1382                         n_tty_set_room(tty);
1383                         timeout = schedule_timeout(timeout);
1384                         continue;
1385                 }
1386                 __set_current_state(TASK_RUNNING);
1387
1388                 /* Deal with packet mode. */
1389                 if (packet && b == buf) {
1390                         if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1391                                 retval = -EFAULT;
1392                                 b--;
1393                                 break;
1394                         }
1395                         nr--;
1396                 }
1397
1398                 if (tty->icanon) {
1399                         /* N.B. avoid overrun if nr == 0 */
1400                         while (nr && tty->read_cnt) {
1401                                 int eol;
1402
1403                                 eol = test_and_clear_bit(tty->read_tail,
1404                                                 tty->read_flags);
1405                                 c = tty->read_buf[tty->read_tail];
1406                                 spin_lock_irqsave(&tty->read_lock, flags);
1407                                 tty->read_tail = ((tty->read_tail+1) &
1408                                                   (N_TTY_BUF_SIZE-1));
1409                                 tty->read_cnt--;
1410                                 if (eol) {
1411                                         /* this test should be redundant:
1412                                          * we shouldn't be reading data if
1413                                          * canon_data is 0
1414                                          */
1415                                         if (--tty->canon_data < 0)
1416                                                 tty->canon_data = 0;
1417                                 }
1418                                 spin_unlock_irqrestore(&tty->read_lock, flags);
1419
1420                                 if (!eol || (c != __DISABLED_CHAR)) {
1421                                         if (tty_put_user(tty, c, b++)) {
1422                                                 retval = -EFAULT;
1423                                                 b--;
1424                                                 break;
1425                                         }
1426                                         nr--;
1427                                 }
1428                                 if (eol) {
1429                                         tty_audit_push(tty);
1430                                         break;
1431                                 }
1432                         }
1433                         if (retval)
1434                                 break;
1435                 } else {
1436                         int uncopied;
1437                         /* The copy function takes the read lock and handles
1438                            locking internally for this case */
1439                         uncopied = copy_from_read_buf(tty, &b, &nr);
1440                         uncopied += copy_from_read_buf(tty, &b, &nr);
1441                         if (uncopied) {
1442                                 retval = -EFAULT;
1443                                 break;
1444                         }
1445                 }
1446
1447                 /* If there is enough space in the read buffer now, let the
1448                  * low-level driver know. We use n_tty_chars_in_buffer() to
1449                  * check the buffer, as it now knows about canonical mode.
1450                  * Otherwise, if the driver is throttled and the line is
1451                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1452                  * we won't get any more characters.
1453                  */
1454                 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1455                         n_tty_set_room(tty);
1456                         check_unthrottle(tty);
1457                 }
1458
1459                 if (b - buf >= minimum)
1460                         break;
1461                 if (time)
1462                         timeout = time;
1463         }
1464         mutex_unlock(&tty->atomic_read_lock);
1465         remove_wait_queue(&tty->read_wait, &wait);
1466
1467         if (!waitqueue_active(&tty->read_wait))
1468                 tty->minimum_to_wake = minimum;
1469
1470         __set_current_state(TASK_RUNNING);
1471         size = b - buf;
1472         if (size) {
1473                 retval = size;
1474                 if (nr)
1475                         clear_bit(TTY_PUSH, &tty->flags);
1476         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1477                  goto do_it_again;
1478
1479         n_tty_set_room(tty);
1480         return retval;
1481 }
1482
1483 /**
1484  *      n_tty_write             -       write function for tty
1485  *      @tty: tty device
1486  *      @file: file object
1487  *      @buf: userspace buffer pointer
1488  *      @nr: size of I/O
1489  *
1490  *      Write function of the terminal device. This is serialized with
1491  *      respect to other write callers but not to termios changes, reads
1492  *      and other such events. We must be careful with N_TTY as the receive
1493  *      code will echo characters, thus calling driver write methods.
1494  *
1495  *      This code must be sure never to sleep through a hangup.
1496  */
1497
1498 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1499                           const unsigned char *buf, size_t nr)
1500 {
1501         const unsigned char *b = buf;
1502         DECLARE_WAITQUEUE(wait, current);
1503         int c;
1504         ssize_t retval = 0;
1505
1506         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1507         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1508                 retval = tty_check_change(tty);
1509                 if (retval)
1510                         return retval;
1511         }
1512
1513         add_wait_queue(&tty->write_wait, &wait);
1514         while (1) {
1515                 set_current_state(TASK_INTERRUPTIBLE);
1516                 if (signal_pending(current)) {
1517                         retval = -ERESTARTSYS;
1518                         break;
1519                 }
1520                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1521                         retval = -EIO;
1522                         break;
1523                 }
1524                 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1525                         while (nr > 0) {
1526                                 ssize_t num = opost_block(tty, b, nr);
1527                                 if (num < 0) {
1528                                         if (num == -EAGAIN)
1529                                                 break;
1530                                         retval = num;
1531                                         goto break_out;
1532                                 }
1533                                 b += num;
1534                                 nr -= num;
1535                                 if (nr == 0)
1536                                         break;
1537                                 c = *b;
1538                                 if (opost(c, tty) < 0)
1539                                         break;
1540                                 b++; nr--;
1541                         }
1542                         if (tty->ops->flush_chars)
1543                                 tty->ops->flush_chars(tty);
1544                 } else {
1545                         while (nr > 0) {
1546                                 c = tty->ops->write(tty, b, nr);
1547                                 if (c < 0) {
1548                                         retval = c;
1549                                         goto break_out;
1550                                 }
1551                                 if (!c)
1552                                         break;
1553                                 b += c;
1554                                 nr -= c;
1555                         }
1556                 }
1557                 if (!nr)
1558                         break;
1559                 if (file->f_flags & O_NONBLOCK) {
1560                         retval = -EAGAIN;
1561                         break;
1562                 }
1563                 schedule();
1564         }
1565 break_out:
1566         __set_current_state(TASK_RUNNING);
1567         remove_wait_queue(&tty->write_wait, &wait);
1568         return (b - buf) ? b - buf : retval;
1569 }
1570
1571 /**
1572  *      n_tty_poll              -       poll method for N_TTY
1573  *      @tty: terminal device
1574  *      @file: file accessing it
1575  *      @wait: poll table
1576  *
1577  *      Called when the line discipline is asked to poll() for data or
1578  *      for special events. This code is not serialized with respect to
1579  *      other events save open/close.
1580  *
1581  *      This code must be sure never to sleep through a hangup.
1582  *      Called without the kernel lock held - fine
1583  */
1584
1585 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
1586                                                         poll_table *wait)
1587 {
1588         unsigned int mask = 0;
1589
1590         poll_wait(file, &tty->read_wait, wait);
1591         poll_wait(file, &tty->write_wait, wait);
1592         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
1593                 mask |= POLLIN | POLLRDNORM;
1594         if (tty->packet && tty->link->ctrl_status)
1595                 mask |= POLLPRI | POLLIN | POLLRDNORM;
1596         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
1597                 mask |= POLLHUP;
1598         if (tty_hung_up_p(file))
1599                 mask |= POLLHUP;
1600         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
1601                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
1602                         tty->minimum_to_wake = MIN_CHAR(tty);
1603                 else
1604                         tty->minimum_to_wake = 1;
1605         }
1606         if (tty->ops->write && !tty_is_writelocked(tty) &&
1607                         tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
1608                         tty_write_room(tty) > 0)
1609                 mask |= POLLOUT | POLLWRNORM;
1610         return mask;
1611 }
1612
1613 static unsigned long inq_canon(struct tty_struct *tty)
1614 {
1615         int nr, head, tail;
1616
1617         if (!tty->canon_data)
1618                 return 0;
1619         head = tty->canon_head;
1620         tail = tty->read_tail;
1621         nr = (head - tail) & (N_TTY_BUF_SIZE-1);
1622         /* Skip EOF-chars.. */
1623         while (head != tail) {
1624                 if (test_bit(tail, tty->read_flags) &&
1625                     tty->read_buf[tail] == __DISABLED_CHAR)
1626                         nr--;
1627                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1628         }
1629         return nr;
1630 }
1631
1632 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
1633                        unsigned int cmd, unsigned long arg)
1634 {
1635         int retval;
1636
1637         switch (cmd) {
1638         case TIOCOUTQ:
1639                 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
1640         case TIOCINQ:
1641                 /* FIXME: Locking */
1642                 retval = tty->read_cnt;
1643                 if (L_ICANON(tty))
1644                         retval = inq_canon(tty);
1645                 return put_user(retval, (unsigned int __user *) arg);
1646         default:
1647                 return n_tty_ioctl_helper(tty, file, cmd, arg);
1648         }
1649 }
1650
1651 struct tty_ldisc_ops tty_ldisc_N_TTY = {
1652         .magic           = TTY_LDISC_MAGIC,
1653         .name            = "n_tty",
1654         .open            = n_tty_open,
1655         .close           = n_tty_close,
1656         .flush_buffer    = n_tty_flush_buffer,
1657         .chars_in_buffer = n_tty_chars_in_buffer,
1658         .read            = n_tty_read,
1659         .write           = n_tty_write,
1660         .ioctl           = n_tty_ioctl,
1661         .set_termios     = n_tty_set_termios,
1662         .poll            = n_tty_poll,
1663         .receive_buf     = n_tty_receive_buf,
1664         .write_wakeup    = n_tty_write_wakeup
1665 };
1666