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 unsigned short from32to16(unsigned a)
  15 {
  16         unsigned short b = a >> 16;
  17         asm("addw %w2,%w0\n\t"
  18             "adcw $0,%w0\n"
  19             : "=r" (b)
  20             : "0" (b), "r" (a));
  21         return b;
  22 }
  23
  24 /*
  25  * Do a checksum on an arbitrary memory area.
  26  * Returns a 32bit checksum.
  27  *
  28  * This isn't as time critical as it used to be because many NICs
  29  * do hardware checksumming these days.
  30  *
  31  * Still, with CHECKSUM_COMPLETE this is called to compute
  32  * checksums on IPv6 headers (40 bytes) and other small parts.
  33  * it's best to have buff aligned on a 64-bit boundary
  34  */
  35 __wsum csum_partial(const void *buff, int len, __wsum sum)
  36 {
  37         u64 temp64 = (__force u64)sum;
  38         unsigned odd, result;
  39
  40         odd = 1 & (unsigned long) buff;
  41         if (unlikely(odd)) {
  42                 if (unlikely(len == 0))
  43                         return sum;
  44                 temp64 = ror32((__force u32)sum, 8);
  45                 temp64 += (*(unsigned char *)buff << 8);
  46                 len--;
  47                 buff++;
  48         }
  49
  50         while (unlikely(len >= 64)) {
  51                 asm("addq 0*8(%[src]),%[res]\n\t"
  52                     "adcq 1*8(%[src]),%[res]\n\t"
  53                     "adcq 2*8(%[src]),%[res]\n\t"
  54                     "adcq 3*8(%[src]),%[res]\n\t"
  55                     "adcq 4*8(%[src]),%[res]\n\t"
  56                     "adcq 5*8(%[src]),%[res]\n\t"
  57                     "adcq 6*8(%[src]),%[res]\n\t"
  58                     "adcq 7*8(%[src]),%[res]\n\t"
  59                     "adcq $0,%[res]"
  60                     : [res] "+r" (temp64)
  61                     : [src] "r" (buff)
  62                     : "memory");
  63                 buff += 64;
  64                 len -= 64;
  65         }
  66
  67         if (len & 32) {
  68                 asm("addq 0*8(%[src]),%[res]\n\t"
  69                     "adcq 1*8(%[src]),%[res]\n\t"
  70                     "adcq 2*8(%[src]),%[res]\n\t"
  71                     "adcq 3*8(%[src]),%[res]\n\t"
  72                     "adcq $0,%[res]"
  73                         : [res] "+r" (temp64)
  74                         : [src] "r" (buff)
  75                         : "memory");
  76                 buff += 32;
  77         }
  78         if (len & 16) {
  79                 asm("addq 0*8(%[src]),%[res]\n\t"
  80                     "adcq 1*8(%[src]),%[res]\n\t"
  81                     "adcq $0,%[res]"
  82                         : [res] "+r" (temp64)
  83                         : [src] "r" (buff)
  84                         : "memory");
  85                 buff += 16;
  86         }
  87         if (len & 8) {
  88                 asm("addq 0*8(%[src]),%[res]\n\t"
  89                     "adcq $0,%[res]"
  90                         : [res] "+r" (temp64)
  91                         : [src] "r" (buff)
  92                         : "memory");
  93                 buff += 8;
  94         }
  95         if (len & 7) {
  96                 unsigned int shift = (8 - (len & 7)) * 8;
  97                 unsigned long trail;
  98
  99                 trail = (load_unaligned_zeropad(buff) << shift) >> shift;
 100
 101                 asm("addq %[trail],%[res]\n\t"
 102                     "adcq $0,%[res]"
 103                         : [res] "+r" (temp64)
 104                         : [trail] "r" (trail));
 105         }
 106         result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff);
 107         if (unlikely(odd)) {
 108                 result = from32to16(result);
 109                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 110         }
 111         return (__force __wsum)result;
 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);