The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/tty_inq.c

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    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 static int ttyinq_flush_secure = 1;
   72 SYSCTL_INT(_kern, OID_AUTO, tty_inq_flush_secure, CTLFLAG_RW,
   73         &ttyinq_flush_secure, 0, "Zero buffers while flushing");
   74 
   75 #define TTYINQ_QUOTESIZE        (TTYINQ_DATASIZE / BMSIZE)
   76 #define BMSIZE                  32
   77 #define GETBIT(tib,boff) \
   78         ((tib)->tib_quotes[(boff) / BMSIZE] & (1 << ((boff) % BMSIZE)))
   79 #define SETBIT(tib,boff) \
   80         ((tib)->tib_quotes[(boff) / BMSIZE] |= (1 << ((boff) % BMSIZE)))
   81 #define CLRBIT(tib,boff) \
   82         ((tib)->tib_quotes[(boff) / BMSIZE] &= ~(1 << ((boff) % BMSIZE)))
   83 
   84 struct ttyinq_block {
   85         struct ttyinq_block     *tib_prev;
   86         struct ttyinq_block     *tib_next;
   87         uint32_t                tib_quotes[TTYINQ_QUOTESIZE];
   88         char                    tib_data[TTYINQ_DATASIZE];
   89 };
   90 
   91 static uma_zone_t ttyinq_zone;
   92 
   93 #define TTYINQ_INSERT_TAIL(ti, tib) do {                                \
   94         if (ti->ti_end == 0) {                                          \
   95                 tib->tib_prev = NULL;                                   \
   96                 tib->tib_next = ti->ti_firstblock;                      \
   97                 ti->ti_firstblock = tib;                                \
   98         } else {                                                        \
   99                 tib->tib_prev = ti->ti_lastblock;                       \
  100                 tib->tib_next = ti->ti_lastblock->tib_next;             \
  101                 ti->ti_lastblock->tib_next = tib;                       \
  102         }                                                               \
  103         if (tib->tib_next != NULL)                                      \
  104                 tib->tib_next->tib_prev = tib;                          \
  105         ti->ti_nblocks++;                                               \
  106 } while (0)
  107 
  108 #define TTYINQ_REMOVE_HEAD(ti) do {                                     \
  109         ti->ti_firstblock = ti->ti_firstblock->tib_next;                \
  110         if (ti->ti_firstblock != NULL)                                  \
  111                 ti->ti_firstblock->tib_prev = NULL;                     \
  112         ti->ti_nblocks--;                                               \
  113 } while (0)
  114 
  115 #define TTYINQ_RECYCLE(ti, tib) do {                                    \
  116         if (ti->ti_quota <= ti->ti_nblocks)                             \
  117                 uma_zfree(ttyinq_zone, tib);                            \
  118         else                                                            \
  119                 TTYINQ_INSERT_TAIL(ti, tib);                            \
  120 } while (0)
  121 
  122 void
  123 ttyinq_setsize(struct ttyinq *ti, struct tty *tp, size_t size)
  124 {
  125         struct ttyinq_block *tib;
  126 
  127         ti->ti_quota = howmany(size, TTYINQ_DATASIZE);
  128 
  129         while (ti->ti_quota > ti->ti_nblocks) {
  130                 /*
  131                  * List is getting bigger.
  132                  * Add new blocks to the tail of the list.
  133                  *
  134                  * We must unlock the TTY temporarily, because we need
  135                  * to allocate memory. This won't be a problem, because
  136                  * in the worst case, another thread ends up here, which
  137                  * may cause us to allocate too many blocks, but this
  138                  * will be caught by the loop below.
  139                  */
  140                 tty_unlock(tp);
  141                 tib = uma_zalloc(ttyinq_zone, M_WAITOK);
  142                 tty_lock(tp);
  143 
  144                 TTYINQ_INSERT_TAIL(ti, tib);
  145         }
  146 }
  147 
  148 void
  149 ttyinq_free(struct ttyinq *ti)
  150 {
  151         struct ttyinq_block *tib;
  152         
  153         ttyinq_flush(ti);
  154         ti->ti_quota = 0;
  155 
  156         while ((tib = ti->ti_firstblock) != NULL) {
  157                 TTYINQ_REMOVE_HEAD(ti);
  158                 uma_zfree(ttyinq_zone, tib);
  159         }
  160 
  161         MPASS(ti->ti_nblocks == 0);
  162 }
  163 
  164 int
  165 ttyinq_read_uio(struct ttyinq *ti, struct tty *tp, struct uio *uio,
  166     size_t rlen, size_t flen)
  167 {
  168 
  169         MPASS(rlen <= uio->uio_resid);
  170 
  171         while (rlen > 0) {
  172                 int error;
  173                 struct ttyinq_block *tib;
  174                 size_t cbegin, cend, clen;
  175 
  176                 /* See if there still is data. */
  177                 if (ti->ti_begin == ti->ti_linestart)
  178                         return (0);
  179                 tib = ti->ti_firstblock;
  180                 if (tib == NULL)
  181                         return (0);
  182 
  183                 /*
  184                  * The end address should be the lowest of these three:
  185                  * - The write pointer
  186                  * - The blocksize - we can't read beyond the block
  187                  * - The end address if we could perform the full read
  188                  */
  189                 cbegin = ti->ti_begin;
  190                 cend = MIN(MIN(ti->ti_linestart, ti->ti_begin + rlen),
  191                     TTYINQ_DATASIZE);
  192                 clen = cend - cbegin;
  193                 MPASS(clen >= flen);
  194                 rlen -= clen;
  195 
  196                 /*
  197                  * We can prevent buffering in some cases:
  198                  * - We need to read the block until the end.
  199                  * - We don't need to read the block until the end, but
  200                  *   there is no data beyond it, which allows us to move
  201                  *   the write pointer to a new block.
  202                  */
  203                 if (cend == TTYINQ_DATASIZE || cend == ti->ti_end) {
  204                         atomic_add_long(&ttyinq_nfast, 1);
  205 
  206                         /*
  207                          * Fast path: zero copy. Remove the first block,
  208                          * so we can unlock the TTY temporarily.
  209                          */
  210                         TTYINQ_REMOVE_HEAD(ti);
  211                         ti->ti_begin = 0;
  212 
  213                         /*
  214                          * Because we remove the first block, we must
  215                          * fix up the block offsets.
  216                          */
  217 #define CORRECT_BLOCK(t) do {                   \
  218         if (t <= TTYINQ_DATASIZE)               \
  219                 t = 0;                          \
  220         else                                    \
  221                 t -= TTYINQ_DATASIZE;           \
  222 } while (0)
  223                         CORRECT_BLOCK(ti->ti_linestart);
  224                         CORRECT_BLOCK(ti->ti_reprint);
  225                         CORRECT_BLOCK(ti->ti_end);
  226 #undef CORRECT_BLOCK
  227 
  228                         /*
  229                          * Temporary unlock and copy the data to
  230                          * userspace. We may need to flush trailing
  231                          * bytes, like EOF characters.
  232                          */
  233                         tty_unlock(tp);
  234                         error = uiomove(tib->tib_data + cbegin,
  235                             clen - flen, uio);
  236                         tty_lock(tp);
  237 
  238                         /* Block can now be readded to the list. */
  239                         TTYINQ_RECYCLE(ti, tib);
  240                 } else {
  241                         char ob[TTYINQ_DATASIZE - 1];
  242                         atomic_add_long(&ttyinq_nslow, 1);
  243 
  244                         /*
  245                          * Slow path: store data in a temporary buffer.
  246                          */
  247                         memcpy(ob, tib->tib_data + cbegin, clen - flen);
  248                         ti->ti_begin += clen;
  249                         MPASS(ti->ti_begin < TTYINQ_DATASIZE);
  250 
  251                         /* Temporary unlock and copy the data to userspace. */
  252                         tty_unlock(tp);
  253                         error = uiomove(ob, clen - flen, uio);
  254                         tty_lock(tp);
  255                 }
  256 
  257                 if (error != 0)
  258                         return (error);
  259                 if (tty_gone(tp))
  260                         return (ENXIO);
  261         }
  262 
  263         return (0);
  264 }
  265 
  266 static __inline void
  267 ttyinq_set_quotes(struct ttyinq_block *tib, size_t offset,
  268     size_t length, int value)
  269 {
  270 
  271         if (value) {
  272                 /* Set the bits. */
  273                 for (; length > 0; length--, offset++)
  274                         SETBIT(tib, offset);
  275         } else {
  276                 /* Unset the bits. */
  277                 for (; length > 0; length--, offset++)
  278                         CLRBIT(tib, offset);
  279         }
  280 }
  281 
  282 size_t
  283 ttyinq_write(struct ttyinq *ti, const void *buf, size_t nbytes, int quote)
  284 {
  285         const char *cbuf = buf;
  286         struct ttyinq_block *tib;
  287         unsigned int boff;
  288         size_t l;
  289         
  290         while (nbytes > 0) {
  291                 boff = ti->ti_end % TTYINQ_DATASIZE;
  292 
  293                 if (ti->ti_end == 0) {
  294                         /* First time we're being used or drained. */
  295                         MPASS(ti->ti_begin == 0);
  296                         tib = ti->ti_firstblock;
  297                         if (tib == NULL) {
  298                                 /* Queue has no blocks. */
  299                                 break;
  300                         }
  301                         ti->ti_lastblock = tib;
  302                 } else if (boff == 0) {
  303                         /* We reached the end of this block on last write. */
  304                         tib = ti->ti_lastblock->tib_next;
  305                         if (tib == NULL) {
  306                                 /* We've reached the watermark. */
  307                                 break;
  308                         }
  309                         ti->ti_lastblock = tib;
  310                 } else {
  311                         tib = ti->ti_lastblock;
  312                 }
  313 
  314                 /* Don't copy more than was requested. */
  315                 l = MIN(nbytes, TTYINQ_DATASIZE - boff);
  316                 MPASS(l > 0);
  317                 memcpy(tib->tib_data + boff, cbuf, l);
  318 
  319                 /* Set the quoting bits for the proper region. */
  320                 ttyinq_set_quotes(tib, boff, l, quote);
  321 
  322                 cbuf += l;
  323                 nbytes -= l;
  324                 ti->ti_end += l;
  325         }
  326         
  327         return (cbuf - (const char *)buf);
  328 }
  329 
  330 int
  331 ttyinq_write_nofrag(struct ttyinq *ti, const void *buf, size_t nbytes, int quote)
  332 {
  333         size_t ret;
  334 
  335         if (ttyinq_bytesleft(ti) < nbytes)
  336                 return (-1);
  337 
  338         /* We should always be able to write it back. */
  339         ret = ttyinq_write(ti, buf, nbytes, quote);
  340         MPASS(ret == nbytes);
  341 
  342         return (0);
  343 }
  344 
  345 void
  346 ttyinq_canonicalize(struct ttyinq *ti)
  347 {
  348 
  349         ti->ti_linestart = ti->ti_reprint = ti->ti_end;
  350         ti->ti_startblock = ti->ti_reprintblock = ti->ti_lastblock;
  351 }
  352 
  353 size_t
  354 ttyinq_findchar(struct ttyinq *ti, const char *breakc, size_t maxlen,
  355     char *lastc)
  356 {
  357         struct ttyinq_block *tib = ti->ti_firstblock;
  358         unsigned int boff = ti->ti_begin;
  359         unsigned int bend = MIN(MIN(TTYINQ_DATASIZE, ti->ti_linestart),
  360             ti->ti_begin + maxlen);
  361 
  362         MPASS(maxlen > 0);
  363 
  364         if (tib == NULL)
  365                 return (0);
  366 
  367         while (boff < bend) {
  368                 if (index(breakc, tib->tib_data[boff]) && !GETBIT(tib, boff)) {
  369                         *lastc = tib->tib_data[boff];
  370                         return (boff - ti->ti_begin + 1);
  371                 }
  372                 boff++;
  373         }
  374 
  375         /* Not found - just process the entire block. */
  376         return (bend - ti->ti_begin);
  377 }
  378 
  379 void
  380 ttyinq_flush(struct ttyinq *ti)
  381 {
  382         struct ttyinq_block *tib = ti->ti_lastblock;
  383 
  384         ti->ti_begin = 0;
  385         ti->ti_linestart = 0;
  386         ti->ti_reprint = 0;
  387         ti->ti_end = 0;
  388 
  389         /* Zero all data in the input queue to get rid of passwords. */
  390         if (ttyinq_flush_secure) {
  391                 for (tib = ti->ti_firstblock; tib != NULL; tib = tib->tib_next)
  392                         bzero(&tib->tib_data, sizeof tib->tib_data);
  393         }
  394 }
  395 
  396 int
  397 ttyinq_peekchar(struct ttyinq *ti, char *c, int *quote)
  398 {
  399         unsigned int boff;
  400         struct ttyinq_block *tib = ti->ti_lastblock;
  401 
  402         if (ti->ti_linestart == ti->ti_end)
  403                 return (-1);
  404 
  405         MPASS(ti->ti_end > 0);
  406         boff = (ti->ti_end - 1) % TTYINQ_DATASIZE;
  407 
  408         *c = tib->tib_data[boff];
  409         *quote = GETBIT(tib, boff);
  410         
  411         return (0);
  412 }
  413 
  414 void
  415 ttyinq_unputchar(struct ttyinq *ti)
  416 {
  417 
  418         MPASS(ti->ti_linestart < ti->ti_end);
  419 
  420         if (--ti->ti_end % TTYINQ_DATASIZE == 0) {
  421                 /* Roll back to the previous block. */
  422                 ti->ti_lastblock = ti->ti_lastblock->tib_prev;
  423                 /*
  424                  * This can only fail if we are unputchar()'ing the
  425                  * first character in the queue.
  426                  */
  427                 MPASS((ti->ti_lastblock == NULL) == (ti->ti_end == 0));
  428         }
  429 }
  430 
  431 void
  432 ttyinq_reprintpos_set(struct ttyinq *ti)
  433 {
  434 
  435         ti->ti_reprint = ti->ti_end;
  436         ti->ti_reprintblock = ti->ti_lastblock;
  437 }
  438 
  439 void
  440 ttyinq_reprintpos_reset(struct ttyinq *ti)
  441 {
  442 
  443         ti->ti_reprint = ti->ti_linestart;
  444         ti->ti_reprintblock = ti->ti_startblock;
  445 }
  446 
  447 static void
  448 ttyinq_line_iterate(struct ttyinq *ti,
  449     ttyinq_line_iterator_t *iterator, void *data,
  450     unsigned int offset, struct ttyinq_block *tib)
  451 {
  452         unsigned int boff;
  453 
  454         /* Use the proper block when we're at the queue head. */
  455         if (offset == 0)
  456                 tib = ti->ti_firstblock;
  457 
  458         /* Iterate all characters and call the iterator function. */
  459         for (; offset < ti->ti_end; offset++) {
  460                 boff = offset % TTYINQ_DATASIZE;
  461                 MPASS(tib != NULL);
  462 
  463                 /* Call back the iterator function. */
  464                 iterator(data, tib->tib_data[boff], GETBIT(tib, boff));
  465 
  466                 /* Last byte iterated - go to the next block. */
  467                 if (boff == TTYINQ_DATASIZE - 1)
  468                         tib = tib->tib_next;
  469                 MPASS(tib != NULL);
  470         }
  471 }
  472 
  473 void
  474 ttyinq_line_iterate_from_linestart(struct ttyinq *ti,
  475     ttyinq_line_iterator_t *iterator, void *data)
  476 {
  477 
  478         ttyinq_line_iterate(ti, iterator, data,
  479             ti->ti_linestart, ti->ti_startblock);
  480 }
  481 
  482 void
  483 ttyinq_line_iterate_from_reprintpos(struct ttyinq *ti,
  484     ttyinq_line_iterator_t *iterator, void *data)
  485 {
  486 
  487         ttyinq_line_iterate(ti, iterator, data,
  488             ti->ti_reprint, ti->ti_reprintblock);
  489 }
  490 
  491 static void
  492 ttyinq_startup(void *dummy)
  493 {
  494 
  495         ttyinq_zone = uma_zcreate("ttyinq", sizeof(struct ttyinq_block),
  496             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
  497 }
  498 
  499 SYSINIT(ttyinq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyinq_startup, NULL);

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