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/i386/i386/in_cksum.c

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    1 /*-
    2  * Copyright (c) 1990 The Regents of the University of California.
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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  *      from tahoe:     in_cksum.c      1.2     86/01/05
   30  *      from:           @(#)in_cksum.c  1.3 (Berkeley) 1/19/91
   31  */
   32 
   33 #include <sys/cdefs.h>
   34 __FBSDID("$FreeBSD: releng/6.1/sys/i386/i386/in_cksum.c 158179 2006-04-30 16:44:43Z cvs2svn $");
   35 
   36 /*
   37  * MPsafe: alfred
   38  */
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/mbuf.h>
   42 
   43 #include <netinet/in.h>
   44 #include <netinet/in_systm.h>
   45 #include <netinet/ip.h>
   46 
   47 #include <machine/in_cksum.h>
   48 
   49 /*
   50  * Checksum routine for Internet Protocol family headers.
   51  *
   52  * This routine is very heavily used in the network
   53  * code and should be modified for each CPU to be as fast as possible.
   54  *
   55  * This implementation is 386 version.
   56  */
   57 
   58 #undef  ADDCARRY
   59 #define ADDCARRY(x)     if ((x) > 0xffff) (x) -= 0xffff
   60 /*
   61  * icc needs to be special cased here, as the asm code below results
   62  * in broken code if compiled with icc.
   63  */
   64 #if !defined(__GNUCLIKE_ASM) || defined(__INTEL_COMPILER)
   65 /* non gcc parts stolen from sys/alpha/alpha/in_cksum.c */
   66 #define REDUCE32                                                          \
   67     {                                                                     \
   68         q_util.q = sum;                                                   \
   69         sum = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3];      \
   70     }
   71 #define REDUCE16                                                          \
   72     {                                                                     \
   73         q_util.q = sum;                                                   \
   74         l_util.l = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \
   75         sum = l_util.s[0] + l_util.s[1];                                  \
   76         ADDCARRY(sum);                                                    \
   77     }
   78 #endif
   79 #define REDUCE          {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);}
   80 
   81 #if !defined(__GNUCLIKE_ASM) || defined(__INTEL_COMPILER)
   82 static const u_int32_t in_masks[] = {
   83         /*0 bytes*/ /*1 byte*/  /*2 bytes*/ /*3 bytes*/
   84         0x00000000, 0x000000FF, 0x0000FFFF, 0x00FFFFFF, /* offset 0 */
   85         0x00000000, 0x0000FF00, 0x00FFFF00, 0xFFFFFF00, /* offset 1 */
   86         0x00000000, 0x00FF0000, 0xFFFF0000, 0xFFFF0000, /* offset 2 */
   87         0x00000000, 0xFF000000, 0xFF000000, 0xFF000000, /* offset 3 */
   88 };
   89 
   90 union l_util {
   91         u_int16_t s[2];
   92         u_int32_t l;
   93 };
   94 union q_util {
   95         u_int16_t s[4];
   96         u_int32_t l[2];
   97         u_int64_t q;
   98 };
   99 
  100 static u_int64_t
  101 in_cksumdata(const u_int32_t *lw, int len)
  102 {
  103         u_int64_t sum = 0;
  104         u_int64_t prefilled;
  105         int offset;
  106         union q_util q_util;
  107 
  108         if ((3 & (long) lw) == 0 && len == 20) {
  109              sum = (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3] + lw[4];
  110              REDUCE32;
  111              return sum;
  112         }
  113 
  114         if ((offset = 3 & (long) lw) != 0) {
  115                 const u_int32_t *masks = in_masks + (offset << 2);
  116                 lw = (u_int32_t *) (((long) lw) - offset);
  117                 sum = *lw++ & masks[len >= 3 ? 3 : len];
  118                 len -= 4 - offset;
  119                 if (len <= 0) {
  120                         REDUCE32;
  121                         return sum;
  122                 }
  123         }
  124 #if 0
  125         /*
  126          * Force to cache line boundary.
  127          */
  128         offset = 32 - (0x1f & (long) lw);
  129         if (offset < 32 && len > offset) {
  130                 len -= offset;
  131                 if (4 & offset) {
  132                         sum += (u_int64_t) lw[0];
  133                         lw += 1;
  134                 }
  135                 if (8 & offset) {
  136                         sum += (u_int64_t) lw[0] + lw[1];
  137                         lw += 2;
  138                 }
  139                 if (16 & offset) {
  140                         sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
  141                         lw += 4;
  142                 }
  143         }
  144 #endif
  145         /*
  146          * access prefilling to start load of next cache line.
  147          * then add current cache line
  148          * save result of prefilling for loop iteration.
  149          */
  150         prefilled = lw[0];
  151         while ((len -= 32) >= 4) {
  152                 u_int64_t prefilling = lw[8];
  153                 sum += prefilled + lw[1] + lw[2] + lw[3]
  154                         + lw[4] + lw[5] + lw[6] + lw[7];
  155                 lw += 8;
  156                 prefilled = prefilling;
  157         }
  158         if (len >= 0) {
  159                 sum += prefilled + lw[1] + lw[2] + lw[3]
  160                         + lw[4] + lw[5] + lw[6] + lw[7];
  161                 lw += 8;
  162         } else {
  163                 len += 32;
  164         }
  165         while ((len -= 16) >= 0) {
  166                 sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
  167                 lw += 4;
  168         }
  169         len += 16;
  170         while ((len -= 4) >= 0) {
  171                 sum += (u_int64_t) *lw++;
  172         }
  173         len += 4;
  174         if (len > 0)
  175                 sum += (u_int64_t) (in_masks[len] & *lw);
  176         REDUCE32;
  177         return sum;
  178 }
  179 
  180 u_short
  181 in_addword(u_short a, u_short b)
  182 {
  183         u_int64_t sum = a + b;
  184 
  185         ADDCARRY(sum);
  186         return (sum);
  187 }
  188 
  189 u_short
  190 in_pseudo(u_int32_t a, u_int32_t b, u_int32_t c)
  191 {
  192         u_int64_t sum;
  193         union q_util q_util;
  194         union l_util l_util;
  195                     
  196         sum = (u_int64_t) a + b + c;
  197         REDUCE16;
  198         return (sum);
  199 }
  200 
  201 u_short
  202 in_cksum_skip(struct mbuf *m, int len, int skip)
  203 {
  204         u_int64_t sum = 0;
  205         int mlen = 0;
  206         int clen = 0;
  207         caddr_t addr;
  208         union q_util q_util;
  209         union l_util l_util;
  210 
  211         len -= skip;
  212         for (; skip && m; m = m->m_next) {
  213                 if (m->m_len > skip) {
  214                         mlen = m->m_len - skip;
  215                         addr = mtod(m, caddr_t) + skip;
  216                         goto skip_start;
  217                 } else {
  218                         skip -= m->m_len;
  219                 }
  220         }
  221 
  222         for (; m && len; m = m->m_next) {
  223                 if (m->m_len == 0)
  224                         continue;
  225                 mlen = m->m_len;
  226                 addr = mtod(m, caddr_t);
  227 skip_start:
  228                 if (len < mlen)
  229                         mlen = len;
  230                 if ((clen ^ (long) addr) & 1)
  231                     sum += in_cksumdata((const u_int32_t *)addr, mlen) << 8;
  232                 else
  233                     sum += in_cksumdata((const u_int32_t *)addr, mlen);
  234 
  235                 clen += mlen;
  236                 len -= mlen;
  237         }
  238         REDUCE16;
  239         return (~sum & 0xffff);
  240 }
  241 
  242 u_int in_cksum_hdr(const struct ip *ip)
  243 {
  244     u_int64_t sum = in_cksumdata((const u_int32_t *)ip, sizeof(struct ip));
  245     union q_util q_util;
  246     union l_util l_util;
  247 
  248     REDUCE16;
  249     return (~sum & 0xffff);
  250 }
  251 #else
  252 
  253 /*
  254  * These asm statements require __volatile because they pass information
  255  * via the condition codes.  GCC does not currently provide a way to specify
  256  * the condition codes as an input or output operand.
  257  *
  258  * The LOAD macro below is effectively a prefetch into cache.  GCC will
  259  * load the value into a register but will not use it.  Since modern CPUs
  260  * reorder operations, this will generally take place in parallel with
  261  * other calculations.
  262  */
  263 #define ADD(n)  __asm __volatile \
  264                 ("addl %1, %0" : "+r" (sum) : \
  265                 "g" (((const u_int32_t *)w)[n / 4]))
  266 #define ADDC(n) __asm __volatile \
  267                 ("adcl %1, %0" : "+r" (sum) : \
  268                 "g" (((const u_int32_t *)w)[n / 4]))
  269 #define LOAD(n) __asm __volatile \
  270                 ("" : : "r" (((const u_int32_t *)w)[n / 4]))
  271 #define MOP     __asm __volatile \
  272                 ("adcl         $0, %0" : "+r" (sum))
  273 
  274 u_short
  275 in_cksum_skip(m, len, skip)
  276         struct mbuf *m;
  277         int len;
  278         int skip;
  279 {
  280         register u_short *w;
  281         register unsigned sum = 0;
  282         register int mlen = 0;
  283         int byte_swapped = 0;
  284         union { char    c[2]; u_short   s; } su;
  285 
  286         len -= skip;
  287         for (; skip && m; m = m->m_next) {
  288                 if (m->m_len > skip) {
  289                         mlen = m->m_len - skip;
  290                         w = (u_short *)(mtod(m, u_char *) + skip);
  291                         goto skip_start;
  292                 } else {
  293                         skip -= m->m_len;
  294                 }
  295         }
  296 
  297         for (;m && len; m = m->m_next) {
  298                 if (m->m_len == 0)
  299                         continue;
  300                 w = mtod(m, u_short *);
  301                 if (mlen == -1) {
  302                         /*
  303                          * The first byte of this mbuf is the continuation
  304                          * of a word spanning between this mbuf and the
  305                          * last mbuf.
  306                          */
  307 
  308                         /* su.c[0] is already saved when scanning previous
  309                          * mbuf.  sum was REDUCEd when we found mlen == -1
  310                          */
  311                         su.c[1] = *(u_char *)w;
  312                         sum += su.s;
  313                         w = (u_short *)((char *)w + 1);
  314                         mlen = m->m_len - 1;
  315                         len--;
  316                 } else
  317                         mlen = m->m_len;
  318 skip_start:
  319                 if (len < mlen)
  320                         mlen = len;
  321                 len -= mlen;
  322                 /*
  323                  * Force to long boundary so we do longword aligned
  324                  * memory operations
  325                  */
  326                 if (3 & (int) w) {
  327                         REDUCE;
  328                         if ((1 & (int) w) && (mlen > 0)) {
  329                                 sum <<= 8;
  330                                 su.c[0] = *(char *)w;
  331                                 w = (u_short *)((char *)w + 1);
  332                                 mlen--;
  333                                 byte_swapped = 1;
  334                         }
  335                         if ((2 & (int) w) && (mlen >= 2)) {
  336                                 sum += *w++;
  337                                 mlen -= 2;
  338                         }
  339                 }
  340                 /*
  341                  * Advance to a 486 cache line boundary.
  342                  */
  343                 if (4 & (int) w && mlen >= 4) {
  344                         ADD(0);
  345                         MOP;
  346                         w += 2;
  347                         mlen -= 4;
  348                 }
  349                 if (8 & (int) w && mlen >= 8) {
  350                         ADD(0);
  351                         ADDC(4);
  352                         MOP;
  353                         w += 4;
  354                         mlen -= 8;
  355                 }
  356                 /*
  357                  * Do as much of the checksum as possible 32 bits at at time.
  358                  * In fact, this loop is unrolled to make overhead from
  359                  * branches &c small.
  360                  */
  361                 mlen -= 1;
  362                 while ((mlen -= 32) >= 0) {
  363                         /*
  364                          * Add with carry 16 words and fold in the last
  365                          * carry by adding a 0 with carry.
  366                          *
  367                          * The early ADD(16) and the LOAD(32) are to load
  368                          * the next 2 cache lines in advance on 486's.  The
  369                          * 486 has a penalty of 2 clock cycles for loading
  370                          * a cache line, plus whatever time the external
  371                          * memory takes to load the first word(s) addressed.
  372                          * These penalties are unavoidable.  Subsequent
  373                          * accesses to a cache line being loaded (and to
  374                          * other external memory?) are delayed until the
  375                          * whole load finishes.  These penalties are mostly
  376                          * avoided by not accessing external memory for
  377                          * 8 cycles after the ADD(16) and 12 cycles after
  378                          * the LOAD(32).  The loop terminates when mlen
  379                          * is initially 33 (not 32) to guaranteed that
  380                          * the LOAD(32) is within bounds.
  381                          */
  382                         ADD(16);
  383                         ADDC(0);
  384                         ADDC(4);
  385                         ADDC(8);
  386                         ADDC(12);
  387                         LOAD(32);
  388                         ADDC(20);
  389                         ADDC(24);
  390                         ADDC(28);
  391                         MOP;
  392                         w += 16;
  393                 }
  394                 mlen += 32 + 1;
  395                 if (mlen >= 32) {
  396                         ADD(16);
  397                         ADDC(0);
  398                         ADDC(4);
  399                         ADDC(8);
  400                         ADDC(12);
  401                         ADDC(20);
  402                         ADDC(24);
  403                         ADDC(28);
  404                         MOP;
  405                         w += 16;
  406                         mlen -= 32;
  407                 }
  408                 if (mlen >= 16) {
  409                         ADD(0);
  410                         ADDC(4);
  411                         ADDC(8);
  412                         ADDC(12);
  413                         MOP;
  414                         w += 8;
  415                         mlen -= 16;
  416                 }
  417                 if (mlen >= 8) {
  418                         ADD(0);
  419                         ADDC(4);
  420                         MOP;
  421                         w += 4;
  422                         mlen -= 8;
  423                 }
  424                 if (mlen == 0 && byte_swapped == 0)
  425                         continue;       /* worth 1% maybe ?? */
  426                 REDUCE;
  427                 while ((mlen -= 2) >= 0) {
  428                         sum += *w++;
  429                 }
  430                 if (byte_swapped) {
  431                         sum <<= 8;
  432                         byte_swapped = 0;
  433                         if (mlen == -1) {
  434                                 su.c[1] = *(char *)w;
  435                                 sum += su.s;
  436                                 mlen = 0;
  437                         } else
  438                                 mlen = -1;
  439                 } else if (mlen == -1)
  440                         /*
  441                          * This mbuf has odd number of bytes.
  442                          * There could be a word split betwen
  443                          * this mbuf and the next mbuf.
  444                          * Save the last byte (to prepend to next mbuf).
  445                          */
  446                         su.c[0] = *(char *)w;
  447         }
  448 
  449         if (len)
  450                 printf("%s: out of data by %d\n", __func__, len);
  451         if (mlen == -1) {
  452                 /* The last mbuf has odd # of bytes. Follow the
  453                    standard (the odd byte is shifted left by 8 bits) */
  454                 su.c[1] = 0;
  455                 sum += su.s;
  456         }
  457         REDUCE;
  458         return (~sum & 0xffff);
  459 }
  460 #endif

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