arch/x86/lib/csum-partial_64.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * arch/x86_64/lib/csum-partial.c
   4  *
   5  * This file contains network checksum routines that are better done
   6  * in an architecture-specific manner due to speed.
   7  */
   8
   9 #include <linux/compiler.h>
  10 #include <linux/export.h>
  11 #include <asm/checksum.h>
  12 #include <asm/word-at-a-time.h>
  13
  14 static inline __wsum csum_finalize_sum(u64 temp64)
  15 {
  16         return (__force __wsum)((temp64 + ror64(temp64, 32)) >> 32);
  17 }
  18
  19 static inline unsigned long update_csum_40b(unsigned long sum, const unsigned long m[5])
  20 {
  21         asm("addq %1,%0\n\t"
  22              "adcq %2,%0\n\t"
  23              "adcq %3,%0\n\t"
  24              "adcq %4,%0\n\t"
  25              "adcq %5,%0\n\t"
  26              "adcq $0,%0"
  27                 :"+r" (sum)
  28                 :"m" (m[0]), "m" (m[1]), "m" (m[2]),
  29                  "m" (m[3]), "m" (m[4]));
  30         return sum;
  31 }
  32
  33 /*
  34  * Do a checksum on an arbitrary memory area.
  35  * Returns a 32bit checksum.
  36  *
  37  * This isn't as time critical as it used to be because many NICs
  38  * do hardware checksumming these days.
  39  *
  40  * Still, with CHECKSUM_COMPLETE this is called to compute
  41  * checksums on IPv6 headers (40 bytes) and other small parts.
  42  * it's best to have buff aligned on a 64-bit boundary
  43  */
  44 __wsum csum_partial(const void *buff, int len, __wsum sum)
  45 {
  46         u64 temp64 = (__force u64)sum;
  47
  48         /* Do two 40-byte chunks in parallel to get better ILP */
  49         if (likely(len >= 80)) {
  50                 u64 temp64_2 = 0;
  51                 do {
  52                         temp64 = update_csum_40b(temp64, buff);
  53                         temp64_2 = update_csum_40b(temp64_2, buff + 40);
  54                         buff += 80;
  55                         len -= 80;
  56                 } while (len >= 80);
  57
  58                 asm("addq %1,%0\n\t"
  59                     "adcq $0,%0"
  60                     :"+r" (temp64): "r" (temp64_2));
  61         }
  62
  63         /*
  64          * len == 40 is the hot case due to IPv6 headers, so return
  65          * early for that exact case without checking the tail bytes.
  66          */
  67         if (len >= 40) {
  68                 temp64 = update_csum_40b(temp64, buff);
  69                 len -= 40;
  70                 if (!len)
  71                         return csum_finalize_sum(temp64);
  72                 buff += 40;
  73         }
  74
  75         if (len & 32) {
  76                 asm("addq 0*8(%[src]),%[res]\n\t"
  77                     "adcq 1*8(%[src]),%[res]\n\t"
  78                     "adcq 2*8(%[src]),%[res]\n\t"
  79                     "adcq 3*8(%[src]),%[res]\n\t"
  80                     "adcq $0,%[res]"
  81                     : [res] "+r"(temp64)
  82                     : [src] "r"(buff), "m"(*(const char(*)[32])buff));
  83                 buff += 32;
  84         }
  85         if (len & 16) {
  86                 asm("addq 0*8(%[src]),%[res]\n\t"
  87                     "adcq 1*8(%[src]),%[res]\n\t"
  88                     "adcq $0,%[res]"
  89                     : [res] "+r"(temp64)
  90                     : [src] "r"(buff), "m"(*(const char(*)[16])buff));
  91                 buff += 16;
  92         }
  93         if (len & 8) {
  94                 asm("addq 0*8(%[src]),%[res]\n\t"
  95                     "adcq $0,%[res]"
  96                     : [res] "+r"(temp64)
  97                     : [src] "r"(buff), "m"(*(const char(*)[8])buff));
  98                 buff += 8;
  99         }
 100         if (len & 7) {
 101                 unsigned int shift = (-len << 3) & 63;
 102                 unsigned long trail;
 103
 104                 trail = (load_unaligned_zeropad(buff) << shift) >> shift;
 105
 106                 asm("addq %[trail],%[res]\n\t"
 107                     "adcq $0,%[res]"
 108                     : [res] "+r"(temp64)
 109                     : [trail] "r"(trail));
 110         }
 111         return csum_finalize_sum(temp64);
 112 }
 113 EXPORT_SYMBOL(csum_partial);
 114
 115 /*
 116  * this routine is used for miscellaneous IP-like checksums, mainly
 117  * in icmp.c
 118  */
 119 __sum16 ip_compute_csum(const void *buff, int len)
 120 {
 121         return csum_fold(csum_partial(buff, len, 0));
 122 }
 123 EXPORT_SYMBOL(ip_compute_csum);