sys/kern/tty_inq.c

   1 /*-
   2  * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
   3  * All rights reserved.
   4  *
   5  * Portions of this software were developed under sponsorship from Snow
   6  * B.V., the Netherlands.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #include <sys/cdefs.h>
  31 __FBSDID("$FreeBSD$");
  32
  33 #include <sys/param.h>
  34 #include <sys/kernel.h>
  35 #include <sys/lock.h>
  36 #include <sys/queue.h>
  37 #include <sys/sysctl.h>
  38 #include <sys/systm.h>
  39 #include <sys/tty.h>
  40 #include <sys/uio.h>
  41
  42 #include <vm/uma.h>
  43
  44 /*
  45  * TTY input queue buffering.
  46  *
  47  * Unlike the output queue, the input queue has more features that are
  48  * needed to properly implement various features offered by the TTY
  49  * interface:
  50  *
  51  * - Data can be removed from the tail of the queue, which is used to
  52  *   implement backspace.
  53  * - Once in a while, input has to be `canonicalized'. When ICANON is
  54  *   turned on, this will be done after a CR has been inserted.
  55  *   Otherwise, it should be done after any character has been inserted.
  56  * - The input queue can store one bit per byte, called the quoting bit.
  57  *   This bit is used by TTYDISC to make backspace work on quoted
  58  *   characters.
  59  *
  60  * In most cases, there is probably less input than output, so unlike
  61  * the outq, we'll stick to 128 byte blocks here.
  62  */
  63
  64 /* Statistics. */
  65 static unsigned long ttyinq_nfast = 0;
  66 SYSCTL_ULONG(_kern, OID_AUTO, tty_inq_nfast, CTLFLAG_RD,
  67         &ttyinq_nfast, 0, "Unbuffered reads to userspace on input");
  68 static unsigned long ttyinq_nslow = 0;
  69 SYSCTL_ULONG(_kern, OID_AUTO, tty_inq_nslow, CTLFLAG_RD,
  70         &ttyinq_nslow, 0, "Buffered reads to userspace on input");
  71
  72 #define TTYINQ_QUOTESIZE        (TTYINQ_DATASIZE / BMSIZE)
  73 #define BMSIZE                  32
  74 #define GETBIT(tib,boff) \
  75         ((tib)->tib_quotes[(boff) / BMSIZE] & (1 << ((boff) % BMSIZE)))
  76 #define SETBIT(tib,boff) \
  77         ((tib)->tib_quotes[(boff) / BMSIZE] |= (1 << ((boff) % BMSIZE)))
  78 #define CLRBIT(tib,boff) \
  79         ((tib)->tib_quotes[(boff) / BMSIZE] &= ~(1 << ((boff) % BMSIZE)))
  80
  81 struct ttyinq_block {
  82         struct ttyinq_block     *tib_prev;
  83         struct ttyinq_block     *tib_next;
  84         uint32_t                tib_quotes[TTYINQ_QUOTESIZE];
  85         char                    tib_data[TTYINQ_DATASIZE];
  86 };
  87
  88 static uma_zone_t ttyinq_zone;
  89
  90 #define TTYINQ_INSERT_TAIL(ti, tib) do {                                \
  91         if (ti->ti_end == 0) {                                          \
  92                 tib->tib_prev = NULL;                                   \
  93                 tib->tib_next = ti->ti_firstblock;                      \
  94                 ti->ti_firstblock = tib;                                \
  95         } else {                                                        \
  96                 tib->tib_prev = ti->ti_lastblock;                       \
  97                 tib->tib_next = ti->ti_lastblock->tib_next;             \
  98                 ti->ti_lastblock->tib_next = tib;                       \
  99         }                                                               \
 100         if (tib->tib_next != NULL)                                      \
 101                 tib->tib_next->tib_prev = tib;                          \
 102         ti->ti_nblocks++;                                               \
 103 } while (0)
 104
 105 #define TTYINQ_REMOVE_HEAD(ti) do {                                     \
 106         ti->ti_firstblock = ti->ti_firstblock->tib_next;                \
 107         if (ti->ti_firstblock != NULL)                                  \
 108                 ti->ti_firstblock->tib_prev = NULL;                     \
 109         ti->ti_nblocks--;                                               \
 110 } while (0)
 111
 112 #define TTYINQ_RECYCLE(ti, tib) do {                                    \
 113         if (ti->ti_quota <= ti->ti_nblocks)                             \
 114                 uma_zfree(ttyinq_zone, tib);                            \
 115         else                                                            \
 116                 TTYINQ_INSERT_TAIL(ti, tib);                            \
 117 } while (0)
 118
 119 void
 120 ttyinq_setsize(struct ttyinq *ti, struct tty *tp, size_t size)
 121 {
 122         struct ttyinq_block *tib;
 123
 124         ti->ti_quota = howmany(size, TTYINQ_DATASIZE);
 125
 126         while (ti->ti_quota > ti->ti_nblocks) {
 127                 /*
 128                  * List is getting bigger.
 129                  * Add new blocks to the tail of the list.
 130                  *
 131                  * We must unlock the TTY temporarily, because we need
 132                  * to allocate memory. This won't be a problem, because
 133                  * in the worst case, another thread ends up here, which
 134                  * may cause us to allocate too many blocks, but this
 135                  * will be caught by the loop below.
 136                  */
 137                 tty_unlock(tp);
 138                 tib = uma_zalloc(ttyinq_zone, M_WAITOK);
 139                 tty_lock(tp);
 140
 141                 TTYINQ_INSERT_TAIL(ti, tib);
 142         }
 143 }
 144
 145 void
 146 ttyinq_free(struct ttyinq *ti)
 147 {
 148         struct ttyinq_block *tib;
 149
 150         ttyinq_flush(ti);
 151         ti->ti_quota = 0;
 152
 153         while ((tib = ti->ti_firstblock) != NULL) {
 154                 TTYINQ_REMOVE_HEAD(ti);
 155                 uma_zfree(ttyinq_zone, tib);
 156         }
 157
 158         MPASS(ti->ti_nblocks == 0);
 159 }
 160
 161 int
 162 ttyinq_read_uio(struct ttyinq *ti, struct tty *tp, struct uio *uio,
 163     size_t rlen, size_t flen)
 164 {
 165
 166         MPASS(rlen <= uio->uio_resid);
 167
 168         while (rlen > 0) {
 169                 int error;
 170                 struct ttyinq_block *tib;
 171                 size_t cbegin, cend, clen;
 172
 173                 /* See if there still is data. */
 174                 if (ti->ti_begin == ti->ti_linestart)
 175                         return (0);
 176                 tib = ti->ti_firstblock;
 177                 if (tib == NULL)
 178                         return (0);
 179
 180                 /*
 181                  * The end address should be the lowest of these three:
 182                  * - The write pointer
 183                  * - The blocksize - we can't read beyond the block
 184                  * - The end address if we could perform the full read
 185                  */
 186                 cbegin = ti->ti_begin;
 187                 cend = MIN(MIN(ti->ti_linestart, ti->ti_begin + rlen),
 188                     TTYINQ_DATASIZE);
 189                 clen = cend - cbegin;
 190                 MPASS(clen >= flen);
 191                 rlen -= clen;
 192
 193                 /*
 194                  * We can prevent buffering in some cases:
 195                  * - We need to read the block until the end.
 196                  * - We don't need to read the block until the end, but
 197                  *   there is no data beyond it, which allows us to move
 198                  *   the write pointer to a new block.
 199                  */
 200                 if (cend == TTYINQ_DATASIZE || cend == ti->ti_end) {
 201                         atomic_add_long(&ttyinq_nfast, 1);
 202
 203                         /*
 204                          * Fast path: zero copy. Remove the first block,
 205                          * so we can unlock the TTY temporarily.
 206                          */
 207                         TTYINQ_REMOVE_HEAD(ti);
 208                         ti->ti_begin = 0;
 209
 210                         /*
 211                          * Because we remove the first block, we must
 212                          * fix up the block offsets.
 213                          */
 214 #define CORRECT_BLOCK(t) do {                   \
 215         if (t <= TTYINQ_DATASIZE)               \
 216                 t = 0;                          \
 217         else                                    \
 218                 t -= TTYINQ_DATASIZE;           \
 219 } while (0)
 220                         CORRECT_BLOCK(ti->ti_linestart);
 221                         CORRECT_BLOCK(ti->ti_reprint);
 222                         CORRECT_BLOCK(ti->ti_end);
 223 #undef CORRECT_BLOCK
 224
 225                         /*
 226                          * Temporary unlock and copy the data to
 227                          * userspace. We may need to flush trailing
 228                          * bytes, like EOF characters.
 229                          */
 230                         tty_unlock(tp);
 231                         error = uiomove(tib->tib_data + cbegin,
 232                             clen - flen, uio);
 233                         tty_lock(tp);
 234
 235                         /* Block can now be readded to the list. */
 236                         TTYINQ_RECYCLE(ti, tib);
 237                 } else {
 238                         char ob[TTYINQ_DATASIZE - 1];
 239                         atomic_add_long(&ttyinq_nslow, 1);
 240
 241                         /*
 242                          * Slow path: store data in a temporary buffer.
 243                          */
 244                         memcpy(ob, tib->tib_data + cbegin, clen - flen);
 245                         ti->ti_begin += clen;
 246                         MPASS(ti->ti_begin < TTYINQ_DATASIZE);
 247
 248                         /* Temporary unlock and copy the data to userspace. */
 249                         tty_unlock(tp);
 250                         error = uiomove(ob, clen - flen, uio);
 251                         tty_lock(tp);
 252                 }
 253
 254                 if (error != 0)
 255                         return (error);
 256                 if (tty_gone(tp))
 257                         return (ENXIO);
 258         }
 259
 260         return (0);
 261 }
 262
 263 static __inline void
 264 ttyinq_set_quotes(struct ttyinq_block *tib, size_t offset,
 265     size_t length, int value)
 266 {
 267
 268         if (value) {
 269                 /* Set the bits. */
 270                 for (; length > 0; length--, offset++)
 271                         SETBIT(tib, offset);
 272         } else {
 273                 /* Unset the bits. */
 274                 for (; length > 0; length--, offset++)
 275                         CLRBIT(tib, offset);
 276         }
 277 }
 278
 279 size_t
 280 ttyinq_write(struct ttyinq *ti, const void *buf, size_t nbytes, int quote)
 281 {
 282         const char *cbuf = buf;
 283         struct ttyinq_block *tib;
 284         unsigned int boff;
 285         size_t l;
 286
 287         while (nbytes > 0) {
 288                 boff = ti->ti_end % TTYINQ_DATASIZE;
 289
 290                 if (ti->ti_end == 0) {
 291                         /* First time we're being used or drained. */
 292                         MPASS(ti->ti_begin == 0);
 293                         tib = ti->ti_firstblock;
 294                         if (tib == NULL) {
 295                                 /* Queue has no blocks. */
 296                                 break;
 297                         }
 298                         ti->ti_lastblock = tib;
 299                 } else if (boff == 0) {
 300                         /* We reached the end of this block on last write. */
 301                         tib = ti->ti_lastblock->tib_next;
 302                         if (tib == NULL) {
 303                                 /* We've reached the watermark. */
 304                                 break;
 305                         }
 306                         ti->ti_lastblock = tib;
 307                 } else {
 308                         tib = ti->ti_lastblock;
 309                 }
 310
 311                 /* Don't copy more than was requested. */
 312                 l = MIN(nbytes, TTYINQ_DATASIZE - boff);
 313                 MPASS(l > 0);
 314                 memcpy(tib->tib_data + boff, cbuf, l);
 315
 316                 /* Set the quoting bits for the proper region. */
 317                 ttyinq_set_quotes(tib, boff, l, quote);
 318
 319                 cbuf += l;
 320                 nbytes -= l;
 321                 ti->ti_end += l;
 322         }
 323
 324         return (cbuf - (const char *)buf);
 325 }
 326
 327 int
 328 ttyinq_write_nofrag(struct ttyinq *ti, const void *buf, size_t nbytes, int quote)
 329 {
 330         size_t ret;
 331
 332         if (ttyinq_bytesleft(ti) < nbytes)
 333                 return (-1);
 334
 335         /* We should always be able to write it back. */
 336         ret = ttyinq_write(ti, buf, nbytes, quote);
 337         MPASS(ret == nbytes);
 338
 339         return (0);
 340 }
 341
 342 void
 343 ttyinq_canonicalize(struct ttyinq *ti)
 344 {
 345
 346         ti->ti_linestart = ti->ti_reprint = ti->ti_end;
 347         ti->ti_startblock = ti->ti_reprintblock = ti->ti_lastblock;
 348 }
 349
 350 size_t
 351 ttyinq_findchar(struct ttyinq *ti, const char *breakc, size_t maxlen,
 352     char *lastc)
 353 {
 354         struct ttyinq_block *tib = ti->ti_firstblock;
 355         unsigned int boff = ti->ti_begin;
 356         unsigned int bend = MIN(MIN(TTYINQ_DATASIZE, ti->ti_linestart),
 357             ti->ti_begin + maxlen);
 358
 359         MPASS(maxlen > 0);
 360
 361         if (tib == NULL)
 362                 return (0);
 363
 364         while (boff < bend) {
 365                 if (index(breakc, tib->tib_data[boff]) && !GETBIT(tib, boff)) {
 366                         *lastc = tib->tib_data[boff];
 367                         return (boff - ti->ti_begin + 1);
 368                 }
 369                 boff++;
 370         }
 371
 372         /* Not found - just process the entire block. */
 373         return (bend - ti->ti_begin);
 374 }
 375
 376 void
 377 ttyinq_flush(struct ttyinq *ti)
 378 {
 379
 380         ti->ti_begin = 0;
 381         ti->ti_linestart = 0;
 382         ti->ti_reprint = 0;
 383         ti->ti_end = 0;
 384 }
 385
 386 #if 0
 387 void
 388 ttyinq_flush_safe(struct ttyinq *ti)
 389 {
 390         struct ttyinq_block *tib;
 391
 392         ttyinq_flush(ti);
 393
 394         /* Zero all data in the input queue to make it more safe */
 395         TAILQ_FOREACH(tib, &ti->ti_list, tib_list) {
 396                 bzero(&tib->tib_quotes, sizeof tib->tib_quotes);
 397                 bzero(&tib->tib_data, sizeof tib->tib_data);
 398         }
 399 }
 400 #endif
 401
 402 int
 403 ttyinq_peekchar(struct ttyinq *ti, char *c, int *quote)
 404 {
 405         unsigned int boff;
 406         struct ttyinq_block *tib = ti->ti_lastblock;
 407
 408         if (ti->ti_linestart == ti->ti_end)
 409                 return (-1);
 410
 411         MPASS(ti->ti_end > 0);
 412         boff = (ti->ti_end - 1) % TTYINQ_DATASIZE;
 413
 414         *c = tib->tib_data[boff];
 415         *quote = GETBIT(tib, boff);
 416
 417         return (0);
 418 }
 419
 420 void
 421 ttyinq_unputchar(struct ttyinq *ti)
 422 {
 423
 424         MPASS(ti->ti_linestart < ti->ti_end);
 425
 426         if (--ti->ti_end % TTYINQ_DATASIZE == 0) {
 427                 /* Roll back to the previous block. */
 428                 ti->ti_lastblock = ti->ti_lastblock->tib_prev;
 429                 /*
 430                  * This can only fail if we are unputchar()'ing the
 431                  * first character in the queue.
 432                  */
 433                 MPASS((ti->ti_lastblock == NULL) == (ti->ti_end == 0));
 434         }
 435 }
 436
 437 void
 438 ttyinq_reprintpos_set(struct ttyinq *ti)
 439 {
 440
 441         ti->ti_reprint = ti->ti_end;
 442         ti->ti_reprintblock = ti->ti_lastblock;
 443 }
 444
 445 void
 446 ttyinq_reprintpos_reset(struct ttyinq *ti)
 447 {
 448
 449         ti->ti_reprint = ti->ti_linestart;
 450         ti->ti_reprintblock = ti->ti_startblock;
 451 }
 452
 453 static void
 454 ttyinq_line_iterate(struct ttyinq *ti,
 455     ttyinq_line_iterator_t *iterator, void *data,
 456     unsigned int offset, struct ttyinq_block *tib)
 457 {
 458         unsigned int boff;
 459
 460         /* Use the proper block when we're at the queue head. */
 461         if (offset == 0)
 462                 tib = ti->ti_firstblock;
 463
 464         /* Iterate all characters and call the iterator function. */
 465         for (; offset < ti->ti_end; offset++) {
 466                 boff = offset % TTYINQ_DATASIZE;
 467                 MPASS(tib != NULL);
 468
 469                 /* Call back the iterator function. */
 470                 iterator(data, tib->tib_data[boff], GETBIT(tib, boff));
 471
 472                 /* Last byte iterated - go to the next block. */
 473                 if (boff == TTYINQ_DATASIZE - 1)
 474                         tib = tib->tib_next;
 475                 MPASS(tib != NULL);
 476         }
 477 }
 478
 479 void
 480 ttyinq_line_iterate_from_linestart(struct ttyinq *ti,
 481     ttyinq_line_iterator_t *iterator, void *data)
 482 {
 483
 484         ttyinq_line_iterate(ti, iterator, data,
 485             ti->ti_linestart, ti->ti_startblock);
 486 }
 487
 488 void
 489 ttyinq_line_iterate_from_reprintpos(struct ttyinq *ti,
 490     ttyinq_line_iterator_t *iterator, void *data)
 491 {
 492
 493         ttyinq_line_iterate(ti, iterator, data,
 494             ti->ti_reprint, ti->ti_reprintblock);
 495 }
 496
 497 static void
 498 ttyinq_startup(void *dummy)
 499 {
 500
 501         ttyinq_zone = uma_zcreate("ttyinq", sizeof(struct ttyinq_block),
 502             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 503 }
 504
 505 SYSINIT(ttyinq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyinq_startup, NULL);