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 write_chan 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
  48 #include <asm/uaccess.h>
  49 #include <asm/system.h>
  50 #include <asm/bitops.h>
  51
  52 /* number of characters left in xmit buffer before select has we have room */
  53 #define WAKEUP_CHARS 256
  54
  55 /*
  56  * This defines the low- and high-watermarks for throttling and
  57  * unthrottling the TTY driver.  These watermarks are used for
  58  * controlling the space in the read buffer.
  59  */
  60 #define TTY_THRESHOLD_THROTTLE          128 /* now based on remaining room */
  61 #define TTY_THRESHOLD_UNTHROTTLE        128
  62
  63 static inline unsigned char *alloc_buf(void)
  64 {
  65         unsigned char *p;
  66         int prio = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
  67
  68         if (PAGE_SIZE != N_TTY_BUF_SIZE) {
  69                 p = kmalloc(N_TTY_BUF_SIZE, prio);
  70                 if (p)
  71                         memset(p, 0, N_TTY_BUF_SIZE);
  72         } else
  73                 p = (unsigned char *)get_zeroed_page(prio);
  74
  75         return p;
  76 }
  77
  78 static inline void free_buf(unsigned char *buf)
  79 {
  80         if (PAGE_SIZE != N_TTY_BUF_SIZE)
  81                 kfree(buf);
  82         else
  83                 free_page((unsigned long) buf);
  84 }
  85
  86 static inline void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
  87 {
  88         if (tty->read_cnt < N_TTY_BUF_SIZE) {
  89                 tty->read_buf[tty->read_head] = c;
  90                 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
  91                 tty->read_cnt++;
  92         }
  93 }
  94
  95 static inline void put_tty_queue(unsigned char c, struct tty_struct *tty)
  96 {
  97         unsigned long flags;
  98         /*
  99          *      The problem of stomping on the buffers ends here.
 100          *      Why didn't anyone see this one coming? --AJK
 101         */
 102         spin_lock_irqsave(&tty->read_lock, flags);
 103         put_tty_queue_nolock(c, tty);
 104         spin_unlock_irqrestore(&tty->read_lock, flags);
 105 }
 106
 107 /*
 108  * Check whether to call the driver.unthrottle function.
 109  * We test the TTY_THROTTLED bit first so that it always
 110  * indicates the current state.
 111  */
 112 static void check_unthrottle(struct tty_struct * tty)
 113 {
 114         if (tty->count &&
 115             test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
 116             tty->driver->unthrottle)
 117                 tty->driver->unthrottle(tty);
 118 }
 119
 120 /*
 121  * Reset the read buffer counters, clear the flags,
 122  * and make sure the driver is unthrottled. Called
 123  * from n_tty_open() and n_tty_flush_buffer().
 124  */
 125 static void reset_buffer_flags(struct tty_struct *tty)
 126 {
 127         unsigned long flags;
 128
 129         spin_lock_irqsave(&tty->read_lock, flags);
 130         tty->read_head = tty->read_tail = tty->read_cnt = 0;
 131         spin_unlock_irqrestore(&tty->read_lock, flags);
 132         tty->canon_head = tty->canon_data = tty->erasing = 0;
 133         memset(&tty->read_flags, 0, sizeof tty->read_flags);
 134         check_unthrottle(tty);
 135 }
 136
 137 /*
 138  * Flush the input buffer
 139  */
 140 void n_tty_flush_buffer(struct tty_struct * tty)
 141 {
 142         /* clear everything and unthrottle the driver */
 143         reset_buffer_flags(tty);
 144
 145         if (!tty->link)
 146                 return;
 147
 148         if (tty->link->packet) {
 149                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
 150                 wake_up_interruptible(&tty->link->read_wait);
 151         }
 152 }
 153
 154 /*
 155  * Return number of characters buffered to be delivered to user
 156  */
 157 ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
 158 {
 159         unsigned long flags;
 160         ssize_t n = 0;
 161
 162         spin_lock_irqsave(&tty->read_lock, flags);
 163         if (!tty->icanon) {
 164                 n = tty->read_cnt;
 165         } else if (tty->canon_data) {
 166                 n = (tty->canon_head > tty->read_tail) ?
 167                         tty->canon_head - tty->read_tail :
 168                         tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
 169         }
 170         spin_unlock_irqrestore(&tty->read_lock, flags);
 171         return n;
 172 }
 173
 174 static inline int is_utf8_continuation(unsigned char c)
 175 {
 176         return (c & 0xc0) == 0x80;
 177 }
 178
 179 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
 180 {
 181         return I_IUTF8(tty) && is_utf8_continuation(c);
 182 }
 183
 184 /*
 185  * Perform OPOST processing.  Returns -1 when the output device is
 186  * full and the character must be retried.
 187  */
 188 static int opost(unsigned char c, struct tty_struct *tty)
 189 {
 190         int     space, spaces;
 191
 192         space = tty->driver->write_room(tty);
 193         if (!space)
 194                 return -1;
 195
 196         if (O_OPOST(tty)) {
 197                 switch (c) {
 198                 case '\n':
 199                         if (O_ONLRET(tty))
 200                                 tty->column = 0;
 201                         if (O_ONLCR(tty)) {
 202                                 if (space < 2)
 203                                         return -1;
 204                                 tty->driver->put_char(tty, '\r');
 205                                 tty->column = 0;
 206                         }
 207                         tty->canon_column = tty->column;
 208                         break;
 209                 case '\r':
 210                         if (O_ONOCR(tty) && tty->column == 0)
 211                                 return 0;
 212                         if (O_OCRNL(tty)) {
 213                                 c = '\n';
 214                                 if (O_ONLRET(tty))
 215                                         tty->canon_column = tty->column = 0;
 216                                 break;
 217                         }
 218                         tty->canon_column = tty->column = 0;
 219                         break;
 220                 case '\t':
 221                         spaces = 8 - (tty->column & 7);
 222                         if (O_TABDLY(tty) == XTABS) {
 223                                 if (space < spaces)
 224                                         return -1;
 225                                 tty->column += spaces;
 226                                 tty->driver->write(tty, 0, "        ", spaces);
 227                                 return 0;
 228                         }
 229                         tty->column += spaces;
 230                         break;
 231                 case '\b':
 232                         if (tty->column > 0)
 233                                 tty->column--;
 234                         break;
 235                 default:
 236                         if (O_OLCUC(tty))
 237                                 c = toupper(c);
 238                         if (!iscntrl(c) && !is_continuation(c, tty))
 239                                 tty->column++;
 240                         break;
 241                 }
 242         }
 243         tty->driver->put_char(tty, c);
 244         return 0;
 245 }
 246
 247 /*
 248  * opost_block --- to speed up block console writes, among other
 249  * things.
 250  */
 251 static ssize_t opost_block(struct tty_struct * tty,
 252                        const unsigned char __user * inbuf, unsigned int nr)
 253 {
 254         char    buf[80];
 255         int     space;
 256         int     i;
 257         char    *cp;
 258
 259         space = tty->driver->write_room(tty);
 260         if (!space)
 261                 return 0;
 262         if (nr > space)
 263                 nr = space;
 264         if (nr > sizeof(buf))
 265             nr = sizeof(buf);
 266
 267         if (copy_from_user(buf, inbuf, nr))
 268                 return -EFAULT;
 269
 270         for (i = 0, cp = buf; i < nr; i++, cp++) {
 271                 switch (*cp) {
 272                 case '\n':
 273                         if (O_ONLRET(tty))
 274                                 tty->column = 0;
 275                         if (O_ONLCR(tty))
 276                                 goto break_out;
 277                         tty->canon_column = tty->column;
 278                         break;
 279                 case '\r':
 280                         if (O_ONOCR(tty) && tty->column == 0)
 281                                 goto break_out;
 282                         if (O_OCRNL(tty)) {
 283                                 *cp = '\n';
 284                                 if (O_ONLRET(tty))
 285                                         tty->canon_column = tty->column = 0;
 286                                 break;
 287                         }
 288                         tty->canon_column = tty->column = 0;
 289                         break;
 290                 case '\t':
 291                         goto break_out;
 292                 case '\b':
 293                         if (tty->column > 0)
 294                                 tty->column--;
 295                         break;
 296                 default:
 297                         if (O_OLCUC(tty))
 298                                 *cp = toupper(*cp);
 299                         if (!iscntrl(*cp))
 300                                 tty->column++;
 301                         break;
 302                 }
 303         }
 304 break_out:
 305         if (tty->driver->flush_chars)
 306                 tty->driver->flush_chars(tty);
 307         i = tty->driver->write(tty, 0, buf, i);
 308         return i;
 309 }
 310
 311
 312
 313 static inline void put_char(unsigned char c, struct tty_struct *tty)
 314 {
 315         tty->driver->put_char(tty, c);
 316 }
 317
 318 /* Must be called only when L_ECHO(tty) is true. */
 319
 320 static void echo_char(unsigned char c, struct tty_struct *tty)
 321 {
 322         if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') {
 323                 put_char('^', tty);
 324                 put_char(c ^ 0100, tty);
 325                 tty->column += 2;
 326         } else
 327                 opost(c, tty);
 328 }
 329
 330 static inline void finish_erasing(struct tty_struct *tty)
 331 {
 332         if (tty->erasing) {
 333                 put_char('/', tty);
 334                 tty->column++;
 335                 tty->erasing = 0;
 336         }
 337 }
 338
 339 static void eraser(unsigned char c, struct tty_struct *tty)
 340 {
 341         enum { ERASE, WERASE, KILL } kill_type;
 342         int head, seen_alnums, cnt;
 343         unsigned long flags;
 344
 345         if (tty->read_head == tty->canon_head) {
 346                 /* opost('\a', tty); */         /* what do you think? */
 347                 return;
 348         }
 349         if (c == ERASE_CHAR(tty))
 350                 kill_type = ERASE;
 351         else if (c == WERASE_CHAR(tty))
 352                 kill_type = WERASE;
 353         else {
 354                 if (!L_ECHO(tty)) {
 355                         spin_lock_irqsave(&tty->read_lock, flags);
 356                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 357                                           (N_TTY_BUF_SIZE - 1));
 358                         tty->read_head = tty->canon_head;
 359                         spin_unlock_irqrestore(&tty->read_lock, flags);
 360                         return;
 361                 }
 362                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
 363                         spin_lock_irqsave(&tty->read_lock, flags);
 364                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
 365                                           (N_TTY_BUF_SIZE - 1));
 366                         tty->read_head = tty->canon_head;
 367                         spin_unlock_irqrestore(&tty->read_lock, flags);
 368                         finish_erasing(tty);
 369                         echo_char(KILL_CHAR(tty), tty);
 370                         /* Add a newline if ECHOK is on and ECHOKE is off. */
 371                         if (L_ECHOK(tty))
 372                                 opost('\n', tty);
 373                         return;
 374                 }
 375                 kill_type = KILL;
 376         }
 377
 378         seen_alnums = 0;
 379         while (tty->read_head != tty->canon_head) {
 380                 head = tty->read_head;
 381
 382                 /* erase a single possibly multibyte character */
 383                 do {
 384                         head = (head - 1) & (N_TTY_BUF_SIZE-1);
 385                         c = tty->read_buf[head];
 386                 } while (is_continuation(c, tty) && head != tty->canon_head);
 387
 388                 /* do not partially erase */
 389                 if (is_continuation(c, tty))
 390                         break;
 391
 392                 if (kill_type == WERASE) {
 393                         /* Equivalent to BSD's ALTWERASE. */
 394                         if (isalnum(c) || c == '_')
 395                                 seen_alnums++;
 396                         else if (seen_alnums)
 397                                 break;
 398                 }
 399                 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
 400                 spin_lock_irqsave(&tty->read_lock, flags);
 401                 tty->read_head = head;
 402                 tty->read_cnt -= cnt;
 403                 spin_unlock_irqrestore(&tty->read_lock, flags);
 404                 if (L_ECHO(tty)) {
 405                         if (L_ECHOPRT(tty)) {
 406                                 if (!tty->erasing) {
 407                                         put_char('\\', tty);
 408                                         tty->column++;
 409                                         tty->erasing = 1;
 410                                 }
 411                                 /* if cnt > 1, output a multi-byte character */
 412                                 echo_char(c, tty);
 413                                 while (--cnt > 0) {
 414                                         head = (head+1) & (N_TTY_BUF_SIZE-1);
 415                                         put_char(tty->read_buf[head], tty);
 416                                 }
 417                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
 418                                 echo_char(ERASE_CHAR(tty), tty);
 419                         } else if (c == '\t') {
 420                                 unsigned int col = tty->canon_column;
 421                                 unsigned long tail = tty->canon_head;
 422
 423                                 /* Find the column of the last char. */
 424                                 while (tail != tty->read_head) {
 425                                         c = tty->read_buf[tail];
 426                                         if (c == '\t')
 427                                                 col = (col | 7) + 1;
 428                                         else if (iscntrl(c)) {
 429                                                 if (L_ECHOCTL(tty))
 430                                                         col += 2;
 431                                         } else if (!is_continuation(c, tty))
 432                                                 col++;
 433                                         tail = (tail+1) & (N_TTY_BUF_SIZE-1);
 434                                 }
 435
 436                                 /* should never happen */
 437                                 if (tty->column > 0x80000000)
 438                                         tty->column = 0;
 439
 440                                 /* Now backup to that column. */
 441                                 while (tty->column > col) {
 442                                         /* Can't use opost here. */
 443                                         put_char('\b', tty);
 444                                         if (tty->column > 0)
 445                                                 tty->column--;
 446                                 }
 447                         } else {
 448                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
 449                                         put_char('\b', tty);
 450                                         put_char(' ', tty);
 451                                         put_char('\b', tty);
 452                                         if (tty->column > 0)
 453                                                 tty->column--;
 454                                 }
 455                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
 456                                         put_char('\b', tty);
 457                                         put_char(' ', tty);
 458                                         put_char('\b', tty);
 459                                         if (tty->column > 0)
 460                                                 tty->column--;
 461                                 }
 462                         }
 463                 }
 464                 if (kill_type == ERASE)
 465                         break;
 466         }
 467         if (tty->read_head == tty->canon_head)
 468                 finish_erasing(tty);
 469 }
 470
 471 static inline void isig(int sig, struct tty_struct *tty, int flush)
 472 {
 473         if (tty->pgrp > 0)
 474                 kill_pg(tty->pgrp, sig, 1);
 475         if (flush || !L_NOFLSH(tty)) {
 476                 n_tty_flush_buffer(tty);
 477                 if (tty->driver->flush_buffer)
 478                         tty->driver->flush_buffer(tty);
 479         }
 480 }
 481
 482 static inline void n_tty_receive_break(struct tty_struct *tty)
 483 {
 484         if (I_IGNBRK(tty))
 485                 return;
 486         if (I_BRKINT(tty)) {
 487                 isig(SIGINT, tty, 1);
 488                 return;
 489         }
 490         if (I_PARMRK(tty)) {
 491                 put_tty_queue('\377', tty);
 492                 put_tty_queue('\0', tty);
 493         }
 494         put_tty_queue('\0', tty);
 495         wake_up_interruptible(&tty->read_wait);
 496 }
 497
 498 static inline void n_tty_receive_overrun(struct tty_struct *tty)
 499 {
 500         char buf[64];
 501
 502         tty->num_overrun++;
 503         if (time_before(tty->overrun_time, jiffies - HZ)) {
 504                 printk("%s: %d input overrun(s)\n", tty_name(tty, buf),
 505                        tty->num_overrun);
 506                 tty->overrun_time = jiffies;
 507                 tty->num_overrun = 0;
 508         }
 509 }
 510
 511 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
 512                                               unsigned char c)
 513 {
 514         if (I_IGNPAR(tty)) {
 515                 return;
 516         }
 517         if (I_PARMRK(tty)) {
 518                 put_tty_queue('\377', tty);
 519                 put_tty_queue('\0', tty);
 520                 put_tty_queue(c, tty);
 521         } else  if (I_INPCK(tty))
 522                 put_tty_queue('\0', tty);
 523         else
 524                 put_tty_queue(c, tty);
 525         wake_up_interruptible(&tty->read_wait);
 526 }
 527
 528 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 529 {
 530         unsigned long flags;
 531
 532         if (tty->raw) {
 533                 put_tty_queue(c, tty);
 534                 return;
 535         }
 536
 537         if (tty->stopped && !tty->flow_stopped &&
 538             I_IXON(tty) && I_IXANY(tty)) {
 539                 start_tty(tty);
 540                 return;
 541         }
 542
 543         if (I_ISTRIP(tty))
 544                 c &= 0x7f;
 545         if (I_IUCLC(tty) && L_IEXTEN(tty))
 546                 c=tolower(c);
 547
 548         if (tty->closing) {
 549                 if (I_IXON(tty)) {
 550                         if (c == START_CHAR(tty))
 551                                 start_tty(tty);
 552                         else if (c == STOP_CHAR(tty))
 553                                 stop_tty(tty);
 554                 }
 555                 return;
 556         }
 557
 558         /*
 559          * If the previous character was LNEXT, or we know that this
 560          * character is not one of the characters that we'll have to
 561          * handle specially, do shortcut processing to speed things
 562          * up.
 563          */
 564         if (!test_bit(c, tty->process_char_map) || tty->lnext) {
 565                 finish_erasing(tty);
 566                 tty->lnext = 0;
 567                 if (L_ECHO(tty)) {
 568                         if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
 569                                 put_char('\a', tty); /* beep if no space */
 570                                 return;
 571                         }
 572                         /* Record the column of first canon char. */
 573                         if (tty->canon_head == tty->read_head)
 574                                 tty->canon_column = tty->column;
 575                         echo_char(c, tty);
 576                 }
 577                 if (I_PARMRK(tty) && c == (unsigned char) '\377')
 578                         put_tty_queue(c, tty);
 579                 put_tty_queue(c, tty);
 580                 return;
 581         }
 582
 583         if (c == '\r') {
 584                 if (I_IGNCR(tty))
 585                         return;
 586                 if (I_ICRNL(tty))
 587                         c = '\n';
 588         } else if (c == '\n' && I_INLCR(tty))
 589                 c = '\r';
 590         if (I_IXON(tty)) {
 591                 if (c == START_CHAR(tty)) {
 592                         start_tty(tty);
 593                         return;
 594                 }
 595                 if (c == STOP_CHAR(tty)) {
 596                         stop_tty(tty);
 597                         return;
 598                 }
 599         }
 600         if (L_ISIG(tty)) {
 601                 int signal;
 602                 signal = SIGINT;
 603                 if (c == INTR_CHAR(tty))
 604                         goto send_signal;
 605                 signal = SIGQUIT;
 606                 if (c == QUIT_CHAR(tty))
 607                         goto send_signal;
 608                 signal = SIGTSTP;
 609                 if (c == SUSP_CHAR(tty)) {
 610 send_signal:
 611                         isig(signal, tty, 0);
 612                         return;
 613                 }
 614         }
 615         if (tty->icanon) {
 616                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
 617                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
 618                         eraser(c, tty);
 619                         return;
 620                 }
 621                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
 622                         tty->lnext = 1;
 623                         if (L_ECHO(tty)) {
 624                                 finish_erasing(tty);
 625                                 if (L_ECHOCTL(tty)) {
 626                                         put_char('^', tty);
 627                                         put_char('\b', tty);
 628                                 }
 629                         }
 630                         return;
 631                 }
 632                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
 633                     L_IEXTEN(tty)) {
 634                         unsigned long tail = tty->canon_head;
 635
 636                         finish_erasing(tty);
 637                         echo_char(c, tty);
 638                         opost('\n', tty);
 639                         while (tail != tty->read_head) {
 640                                 echo_char(tty->read_buf[tail], tty);
 641                                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
 642                         }
 643                         return;
 644                 }
 645                 if (c == '\n') {
 646                         if (L_ECHO(tty) || L_ECHONL(tty)) {
 647                                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
 648                                         put_char('\a', tty);
 649                                         return;
 650                                 }
 651                                 opost('\n', tty);
 652                         }
 653                         goto handle_newline;
 654                 }
 655                 if (c == EOF_CHAR(tty)) {
 656                         if (tty->canon_head != tty->read_head)
 657                                 set_bit(TTY_PUSH, &tty->flags);
 658                         c = __DISABLED_CHAR;
 659                         goto handle_newline;
 660                 }
 661                 if ((c == EOL_CHAR(tty)) ||
 662                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
 663                         /*
 664                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
 665                          */
 666                         if (L_ECHO(tty)) {
 667                                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
 668                                         put_char('\a', tty);
 669                                         return;
 670                                 }
 671                                 /* Record the column of first canon char. */
 672                                 if (tty->canon_head == tty->read_head)
 673                                         tty->canon_column = tty->column;
 674                                 echo_char(c, tty);
 675                         }
 676                         /*
 677                          * XXX does PARMRK doubling happen for
 678                          * EOL_CHAR and EOL2_CHAR?
 679                          */
 680                         if (I_PARMRK(tty) && c == (unsigned char) '\377')
 681                                 put_tty_queue(c, tty);
 682
 683                 handle_newline:
 684                         spin_lock_irqsave(&tty->read_lock, flags);
 685                         set_bit(tty->read_head, tty->read_flags);
 686                         put_tty_queue_nolock(c, tty);
 687                         tty->canon_head = tty->read_head;
 688                         tty->canon_data++;
 689                         spin_unlock_irqrestore(&tty->read_lock, flags);
 690                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
 691                         if (waitqueue_active(&tty->read_wait))
 692                                 wake_up_interruptible(&tty->read_wait);
 693                         return;
 694                 }
 695         }
 696
 697         finish_erasing(tty);
 698         if (L_ECHO(tty)) {
 699                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
 700                         put_char('\a', tty); /* beep if no space */
 701                         return;
 702                 }
 703                 if (c == '\n')
 704                         opost('\n', tty);
 705                 else {
 706                         /* Record the column of first canon char. */
 707                         if (tty->canon_head == tty->read_head)
 708                                 tty->canon_column = tty->column;
 709                         echo_char(c, tty);
 710                 }
 711         }
 712
 713         if (I_PARMRK(tty) && c == (unsigned char) '\377')
 714                 put_tty_queue(c, tty);
 715
 716         put_tty_queue(c, tty);
 717 }
 718
 719 static int n_tty_receive_room(struct tty_struct *tty)
 720 {
 721         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
 722
 723         /*
 724          * If we are doing input canonicalization, and there are no
 725          * pending newlines, let characters through without limit, so
 726          * that erase characters will be handled.  Other excess
 727          * characters will be beeped.
 728          */
 729         if (tty->icanon && !tty->canon_data)
 730                 return N_TTY_BUF_SIZE;
 731
 732         if (left > 0)
 733                 return left;
 734         return 0;
 735 }
 736
 737 /*
 738  * Required for the ptys, serial driver etc. since processes
 739  * that attach themselves to the master and rely on ASYNC
 740  * IO must be woken up
 741  */
 742
 743 static void n_tty_write_wakeup(struct tty_struct *tty)
 744 {
 745         if (tty->fasync)
 746         {
 747                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 748                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
 749         }
 750         return;
 751 }
 752
 753 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 754                               char *fp, int count)
 755 {
 756         const unsigned char *p;
 757         char *f, flags = TTY_NORMAL;
 758         int     i;
 759         char    buf[64];
 760         unsigned long cpuflags;
 761
 762         if (!tty->read_buf)
 763                 return;
 764
 765         if (tty->real_raw) {
 766                 spin_lock_irqsave(&tty->read_lock, cpuflags);
 767                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
 768                         N_TTY_BUF_SIZE - tty->read_head);
 769                 i = min(count, i);
 770                 memcpy(tty->read_buf + tty->read_head, cp, i);
 771                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
 772                 tty->read_cnt += i;
 773                 cp += i;
 774                 count -= i;
 775
 776                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
 777                         N_TTY_BUF_SIZE - tty->read_head);
 778                 i = min(count, i);
 779                 memcpy(tty->read_buf + tty->read_head, cp, i);
 780                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
 781                 tty->read_cnt += i;
 782                 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
 783         } else {
 784                 for (i=count, p = cp, f = fp; i; i--, p++) {
 785                         if (f)
 786                                 flags = *f++;
 787                         switch (flags) {
 788                         case TTY_NORMAL:
 789                                 n_tty_receive_char(tty, *p);
 790                                 break;
 791                         case TTY_BREAK:
 792                                 n_tty_receive_break(tty);
 793                                 break;
 794                         case TTY_PARITY:
 795                         case TTY_FRAME:
 796                                 n_tty_receive_parity_error(tty, *p);
 797                                 break;
 798                         case TTY_OVERRUN:
 799                                 n_tty_receive_overrun(tty);
 800                                 break;
 801                         default:
 802                                 printk("%s: unknown flag %d\n",
 803                                        tty_name(tty, buf), flags);
 804                                 break;
 805                         }
 806                 }
 807                 if (tty->driver->flush_chars)
 808                         tty->driver->flush_chars(tty);
 809         }
 810
 811         if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
 812                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
 813                 if (waitqueue_active(&tty->read_wait))
 814                         wake_up_interruptible(&tty->read_wait);
 815         }
 816
 817         /*
 818          * Check the remaining room for the input canonicalization
 819          * mode.  We don't want to throttle the driver if we're in
 820          * canonical mode and don't have a newline yet!
 821          */
 822         if (n_tty_receive_room(tty) < TTY_THRESHOLD_THROTTLE) {
 823                 /* check TTY_THROTTLED first so it indicates our state */
 824                 if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
 825                     tty->driver->throttle)
 826                         tty->driver->throttle(tty);
 827         }
 828 }
 829
 830 int is_ignored(int sig)
 831 {
 832         return (sigismember(&current->blocked, sig) ||
 833                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
 834 }
 835
 836 static void n_tty_set_termios(struct tty_struct *tty, struct termios * old)
 837 {
 838         if (!tty)
 839                 return;
 840
 841         tty->icanon = (L_ICANON(tty) != 0);
 842         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
 843                 tty->raw = 1;
 844                 tty->real_raw = 1;
 845                 return;
 846         }
 847         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
 848             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
 849             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
 850             I_PARMRK(tty)) {
 851                 local_irq_disable(); // FIXME: is this safe?
 852                 memset(tty->process_char_map, 0, 256/8);
 853
 854                 if (I_IGNCR(tty) || I_ICRNL(tty))
 855                         set_bit('\r', tty->process_char_map);
 856                 if (I_INLCR(tty))
 857                         set_bit('\n', tty->process_char_map);
 858
 859                 if (L_ICANON(tty)) {
 860                         set_bit(ERASE_CHAR(tty), tty->process_char_map);
 861                         set_bit(KILL_CHAR(tty), tty->process_char_map);
 862                         set_bit(EOF_CHAR(tty), tty->process_char_map);
 863                         set_bit('\n', tty->process_char_map);
 864                         set_bit(EOL_CHAR(tty), tty->process_char_map);
 865                         if (L_IEXTEN(tty)) {
 866                                 set_bit(WERASE_CHAR(tty),
 867                                         tty->process_char_map);
 868                                 set_bit(LNEXT_CHAR(tty),
 869                                         tty->process_char_map);
 870                                 set_bit(EOL2_CHAR(tty),
 871                                         tty->process_char_map);
 872                                 if (L_ECHO(tty))
 873                                         set_bit(REPRINT_CHAR(tty),
 874                                                 tty->process_char_map);
 875                         }
 876                 }
 877                 if (I_IXON(tty)) {
 878                         set_bit(START_CHAR(tty), tty->process_char_map);
 879                         set_bit(STOP_CHAR(tty), tty->process_char_map);
 880                 }
 881                 if (L_ISIG(tty)) {
 882                         set_bit(INTR_CHAR(tty), tty->process_char_map);
 883                         set_bit(QUIT_CHAR(tty), tty->process_char_map);
 884                         set_bit(SUSP_CHAR(tty), tty->process_char_map);
 885                 }
 886                 clear_bit(__DISABLED_CHAR, tty->process_char_map);
 887                 local_irq_enable(); // FIXME: is this safe?
 888                 tty->raw = 0;
 889                 tty->real_raw = 0;
 890         } else {
 891                 tty->raw = 1;
 892                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
 893                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
 894                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
 895                         tty->real_raw = 1;
 896                 else
 897                         tty->real_raw = 0;
 898         }
 899 }
 900
 901 static void n_tty_close(struct tty_struct *tty)
 902 {
 903         n_tty_flush_buffer(tty);
 904         if (tty->read_buf) {
 905                 free_buf(tty->read_buf);
 906                 tty->read_buf = 0;
 907         }
 908 }
 909
 910 static int n_tty_open(struct tty_struct *tty)
 911 {
 912         if (!tty)
 913                 return -EINVAL;
 914
 915         if (!tty->read_buf) {
 916                 tty->read_buf = alloc_buf();
 917                 if (!tty->read_buf)
 918                         return -ENOMEM;
 919         }
 920         memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
 921         reset_buffer_flags(tty);
 922         tty->column = 0;
 923         n_tty_set_termios(tty, 0);
 924         tty->minimum_to_wake = 1;
 925         tty->closing = 0;
 926         return 0;
 927 }
 928
 929 static inline int input_available_p(struct tty_struct *tty, int amt)
 930 {
 931         if (tty->icanon) {
 932                 if (tty->canon_data)
 933                         return 1;
 934         } else if (tty->read_cnt >= (amt ? amt : 1))
 935                 return 1;
 936
 937         return 0;
 938 }
 939
 940 /*
 941  * Helper function to speed up read_chan.  It is only called when
 942  * ICANON is off; it copies characters straight from the tty queue to
 943  * user space directly.  It can be profitably called twice; once to
 944  * drain the space from the tail pointer to the (physical) end of the
 945  * buffer, and once to drain the space from the (physical) beginning of
 946  * the buffer to head pointer.
 947  */
 948 static inline int copy_from_read_buf(struct tty_struct *tty,
 949                                       unsigned char __user **b,
 950                                       size_t *nr)
 951
 952 {
 953         int retval;
 954         ssize_t n;
 955         unsigned long flags;
 956
 957         retval = 0;
 958         spin_lock_irqsave(&tty->read_lock, flags);
 959         n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
 960         n = min((ssize_t)*nr, n);
 961         spin_unlock_irqrestore(&tty->read_lock, flags);
 962         if (n) {
 963                 mb();
 964                 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
 965                 n -= retval;
 966                 spin_lock_irqsave(&tty->read_lock, flags);
 967                 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
 968                 tty->read_cnt -= n;
 969                 spin_unlock_irqrestore(&tty->read_lock, flags);
 970                 *b += n;
 971                 *nr -= n;
 972         }
 973         return retval;
 974 }
 975
 976 extern ssize_t redirected_tty_write(struct file *,const char *,size_t,loff_t *);
 977
 978 static ssize_t read_chan(struct tty_struct *tty, struct file *file,
 979                          unsigned char __user *buf, size_t nr)
 980 {
 981         unsigned char __user *b = buf;
 982         DECLARE_WAITQUEUE(wait, current);
 983         int c;
 984         int minimum, time;
 985         ssize_t retval = 0;
 986         ssize_t size;
 987         long timeout;
 988         unsigned long flags;
 989
 990 do_it_again:
 991
 992         if (!tty->read_buf) {
 993                 printk("n_tty_read_chan: called with read_buf == NULL?!?\n");
 994                 return -EIO;
 995         }
 996
 997         /* Job control check -- must be done at start and after
 998            every sleep (POSIX.1 7.1.1.4). */
 999         /* NOTE: not yet done after every sleep pending a thorough
1000            check of the logic of this change. -- jlc */
1001         /* don't stop on /dev/console */
1002         if (file->f_op->write != redirected_tty_write &&
1003             current->signal->tty == tty) {
1004                 if (tty->pgrp <= 0)
1005                         printk("read_chan: tty->pgrp <= 0!\n");
1006                 else if (process_group(current) != tty->pgrp) {
1007                         if (is_ignored(SIGTTIN) ||
1008                             is_orphaned_pgrp(process_group(current)))
1009                                 return -EIO;
1010                         kill_pg(process_group(current), SIGTTIN, 1);
1011                         return -ERESTARTSYS;
1012                 }
1013         }
1014
1015         minimum = time = 0;
1016         timeout = MAX_SCHEDULE_TIMEOUT;
1017         if (!tty->icanon) {
1018                 time = (HZ / 10) * TIME_CHAR(tty);
1019                 minimum = MIN_CHAR(tty);
1020                 if (minimum) {
1021                         if (time)
1022                                 tty->minimum_to_wake = 1;
1023                         else if (!waitqueue_active(&tty->read_wait) ||
1024                                  (tty->minimum_to_wake > minimum))
1025                                 tty->minimum_to_wake = minimum;
1026                 } else {
1027                         timeout = 0;
1028                         if (time) {
1029                                 timeout = time;
1030                                 time = 0;
1031                         }
1032                         tty->minimum_to_wake = minimum = 1;
1033                 }
1034         }
1035
1036         if (file->f_flags & O_NONBLOCK) {
1037                 if (down_trylock(&tty->atomic_read))
1038                         return -EAGAIN;
1039         }
1040         else {
1041                 if (down_interruptible(&tty->atomic_read))
1042                         return -ERESTARTSYS;
1043         }
1044
1045         add_wait_queue(&tty->read_wait, &wait);
1046         set_bit(TTY_DONT_FLIP, &tty->flags);
1047         while (nr) {
1048                 /* First test for status change. */
1049                 if (tty->packet && tty->link->ctrl_status) {
1050                         unsigned char cs;
1051                         if (b != buf)
1052                                 break;
1053                         cs = tty->link->ctrl_status;
1054                         tty->link->ctrl_status = 0;
1055                         if (put_user(cs, b++)) {
1056                                 retval = -EFAULT;
1057                                 b--;
1058                                 break;
1059                         }
1060                         nr--;
1061                         break;
1062                 }
1063                 /* This statement must be first before checking for input
1064                    so that any interrupt will set the state back to
1065                    TASK_RUNNING. */
1066                 set_current_state(TASK_INTERRUPTIBLE);
1067
1068                 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1069                     ((minimum - (b - buf)) >= 1))
1070                         tty->minimum_to_wake = (minimum - (b - buf));
1071
1072                 if (!input_available_p(tty, 0)) {
1073                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1074                                 retval = -EIO;
1075                                 break;
1076                         }
1077                         if (tty_hung_up_p(file))
1078                                 break;
1079                         if (!timeout)
1080                                 break;
1081                         if (file->f_flags & O_NONBLOCK) {
1082                                 retval = -EAGAIN;
1083                                 break;
1084                         }
1085                         if (signal_pending(current)) {
1086                                 retval = -ERESTARTSYS;
1087                                 break;
1088                         }
1089                         clear_bit(TTY_DONT_FLIP, &tty->flags);
1090                         timeout = schedule_timeout(timeout);
1091                         set_bit(TTY_DONT_FLIP, &tty->flags);
1092                         continue;
1093                 }
1094                 __set_current_state(TASK_RUNNING);
1095
1096                 /* Deal with packet mode. */
1097                 if (tty->packet && b == buf) {
1098                         if (put_user(TIOCPKT_DATA, b++)) {
1099                                 retval = -EFAULT;
1100                                 b--;
1101                                 break;
1102                         }
1103                         nr--;
1104                 }
1105
1106                 if (tty->icanon) {
1107                         /* N.B. avoid overrun if nr == 0 */
1108                         while (nr && tty->read_cnt) {
1109                                 int eol;
1110
1111                                 eol = test_and_clear_bit(tty->read_tail,
1112                                                 tty->read_flags);
1113                                 c = tty->read_buf[tty->read_tail];
1114                                 spin_lock_irqsave(&tty->read_lock, flags);
1115                                 tty->read_tail = ((tty->read_tail+1) &
1116                                                   (N_TTY_BUF_SIZE-1));
1117                                 tty->read_cnt--;
1118                                 if (eol) {
1119                                         /* this test should be redundant:
1120                                          * we shouldn't be reading data if
1121                                          * canon_data is 0
1122                                          */
1123                                         if (--tty->canon_data < 0)
1124                                                 tty->canon_data = 0;
1125                                 }
1126                                 spin_unlock_irqrestore(&tty->read_lock, flags);
1127
1128                                 if (!eol || (c != __DISABLED_CHAR)) {
1129                                         if (put_user(c, b++)) {
1130                                                 retval = -EFAULT;
1131                                                 b--;
1132                                                 break;
1133                                         }
1134                                         nr--;
1135                                 }
1136                                 if (eol)
1137                                         break;
1138                         }
1139                         if (retval)
1140                                 break;
1141                 } else {
1142                         int uncopied;
1143                         uncopied = copy_from_read_buf(tty, &b, &nr);
1144                         uncopied += copy_from_read_buf(tty, &b, &nr);
1145                         if (uncopied) {
1146                                 retval = -EFAULT;
1147                                 break;
1148                         }
1149                 }
1150
1151                 /* If there is enough space in the read buffer now, let the
1152                  * low-level driver know. We use n_tty_chars_in_buffer() to
1153                  * check the buffer, as it now knows about canonical mode.
1154                  * Otherwise, if the driver is throttled and the line is
1155                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1156                  * we won't get any more characters.
1157                  */
1158                 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE)
1159                         check_unthrottle(tty);
1160
1161                 if (b - buf >= minimum)
1162                         break;
1163                 if (time)
1164                         timeout = time;
1165         }
1166         clear_bit(TTY_DONT_FLIP, &tty->flags);
1167         up(&tty->atomic_read);
1168         remove_wait_queue(&tty->read_wait, &wait);
1169
1170         if (!waitqueue_active(&tty->read_wait))
1171                 tty->minimum_to_wake = minimum;
1172
1173         __set_current_state(TASK_RUNNING);
1174         size = b - buf;
1175         if (size) {
1176                 retval = size;
1177                 if (nr)
1178                         clear_bit(TTY_PUSH, &tty->flags);
1179         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1180                  goto do_it_again;
1181
1182         return retval;
1183 }
1184
1185 static ssize_t write_chan(struct tty_struct * tty, struct file * file,
1186                           const unsigned char __user * buf, size_t nr)
1187 {
1188         const unsigned char __user *b = buf;
1189         DECLARE_WAITQUEUE(wait, current);
1190         int c;
1191         ssize_t retval = 0;
1192
1193         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1194         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1195                 retval = tty_check_change(tty);
1196                 if (retval)
1197                         return retval;
1198         }
1199
1200         add_wait_queue(&tty->write_wait, &wait);
1201         while (1) {
1202                 set_current_state(TASK_INTERRUPTIBLE);
1203                 if (signal_pending(current)) {
1204                         retval = -ERESTARTSYS;
1205                         break;
1206                 }
1207                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1208                         retval = -EIO;
1209                         break;
1210                 }
1211                 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1212                         while (nr > 0) {
1213                                 ssize_t num = opost_block(tty, b, nr);
1214                                 if (num < 0) {
1215                                         if (num == -EAGAIN)
1216                                                 break;
1217                                         retval = num;
1218                                         goto break_out;
1219                                 }
1220                                 b += num;
1221                                 nr -= num;
1222                                 if (nr == 0)
1223                                         break;
1224                                 get_user(c, b);
1225                                 if (opost(c, tty) < 0)
1226                                         break;
1227                                 b++; nr--;
1228                         }
1229                         if (tty->driver->flush_chars)
1230                                 tty->driver->flush_chars(tty);
1231                 } else {
1232                         c = tty->driver->write(tty, 1, b, nr);
1233                         if (c < 0) {
1234                                 retval = c;
1235                                 goto break_out;
1236                         }
1237                         b += c;
1238                         nr -= c;
1239                 }
1240                 if (!nr)
1241                         break;
1242                 if (file->f_flags & O_NONBLOCK) {
1243                         retval = -EAGAIN;
1244                         break;
1245                 }
1246                 schedule();
1247         }
1248 break_out:
1249         __set_current_state(TASK_RUNNING);
1250         remove_wait_queue(&tty->write_wait, &wait);
1251         return (b - buf) ? b - buf : retval;
1252 }
1253
1254 /* Called without the kernel lock held - fine */
1255 static unsigned int normal_poll(struct tty_struct * tty, struct file * file, poll_table *wait)
1256 {
1257         unsigned int mask = 0;
1258
1259         poll_wait(file, &tty->read_wait, wait);
1260         poll_wait(file, &tty->write_wait, wait);
1261         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
1262                 mask |= POLLIN | POLLRDNORM;
1263         if (tty->packet && tty->link->ctrl_status)
1264                 mask |= POLLPRI | POLLIN | POLLRDNORM;
1265         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
1266                 mask |= POLLHUP;
1267         if (tty_hung_up_p(file))
1268                 mask |= POLLHUP;
1269         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
1270                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
1271                         tty->minimum_to_wake = MIN_CHAR(tty);
1272                 else
1273                         tty->minimum_to_wake = 1;
1274         }
1275         if (tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS &&
1276                         tty->driver->write_room(tty) > 0)
1277                 mask |= POLLOUT | POLLWRNORM;
1278         return mask;
1279 }
1280
1281 struct tty_ldisc tty_ldisc_N_TTY = {
1282         TTY_LDISC_MAGIC,        /* magic */
1283         "n_tty",                /* name */
1284         0,                      /* num */
1285         0,                      /* flags */
1286         n_tty_open,             /* open */
1287         n_tty_close,            /* close */
1288         n_tty_flush_buffer,     /* flush_buffer */
1289         n_tty_chars_in_buffer,  /* chars_in_buffer */
1290         read_chan,              /* read */
1291         write_chan,             /* write */
1292         n_tty_ioctl,            /* ioctl */
1293         n_tty_set_termios,      /* set_termios */
1294         normal_poll,            /* poll */
1295         n_tty_receive_buf,      /* receive_buf */
1296         n_tty_receive_room,     /* receive_room */
1297         n_tty_write_wakeup      /* write_wakeup */
1298 };
1299