Line data    Source code

       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           0 :         unsigned short b = a >> 16;
      17           0 :         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             : static inline __wsum csum_tail(u64 temp64, int odd)
      25             : {
      26             :         unsigned int result;
      27             : 
      28           0 :         result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff);
      29           0 :         if (unlikely(odd)) {
      30           0 :                 result = from32to16(result);
      31           0 :                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
      32             :         }
      33             :         return (__force __wsum)result;
      34             : }
      35             : 
      36             : /*
      37             :  * Do a checksum on an arbitrary memory area.
      38             :  * Returns a 32bit checksum.
      39             :  *
      40             :  * This isn't as time critical as it used to be because many NICs
      41             :  * do hardware checksumming these days.
      42             :  *
      43             :  * Still, with CHECKSUM_COMPLETE this is called to compute
      44             :  * checksums on IPv6 headers (40 bytes) and other small parts.
      45             :  * it's best to have buff aligned on a 64-bit boundary
      46             :  */
      47           0 : __wsum csum_partial(const void *buff, int len, __wsum sum)
      48             : {
      49           0 :         u64 temp64 = (__force u64)sum;
      50             :         unsigned odd;
      51             : 
      52           0 :         odd = 1 & (unsigned long) buff;
      53           0 :         if (unlikely(odd)) {
      54           0 :                 if (unlikely(len == 0))
      55             :                         return sum;
      56           0 :                 temp64 = ror32((__force u32)sum, 8);
      57           0 :                 temp64 += (*(unsigned char *)buff << 8);
      58           0 :                 len--;
      59           0 :                 buff++;
      60             :         }
      61             : 
      62             :         /*
      63             :          * len == 40 is the hot case due to IPv6 headers, but annotating it likely()
      64             :          * has noticeable negative affect on codegen for all other cases with
      65             :          * minimal performance benefit here.
      66             :          */
      67           0 :         if (len == 40) {
      68           0 :                 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 4*8(%[src]),%[res]\n\t"
      73             :                     "adcq $0,%[res]"
      74             :                     : [res] "+r"(temp64)
      75             :                     : [src] "r"(buff), "m"(*(const char(*)[40])buff));
      76           0 :                 return csum_tail(temp64, odd);
      77             :         }
      78           0 :         if (unlikely(len >= 64)) {
      79             :                 /*
      80             :                  * Extra accumulators for better ILP in the loop.
      81             :                  */
      82             :                 u64 tmp_accum, tmp_carries;
      83             : 
      84           0 :                 asm("xorl %k[tmp_accum],%k[tmp_accum]\n\t"
      85             :                     "xorl %k[tmp_carries],%k[tmp_carries]\n\t"
      86             :                     "subl $64, %[len]\n\t"
      87             :                     "1:\n\t"
      88             :                     "addq 0*8(%[src]),%[res]\n\t"
      89             :                     "adcq 1*8(%[src]),%[res]\n\t"
      90             :                     "adcq 2*8(%[src]),%[res]\n\t"
      91             :                     "adcq 3*8(%[src]),%[res]\n\t"
      92             :                     "adcl $0,%k[tmp_carries]\n\t"
      93             :                     "addq 4*8(%[src]),%[tmp_accum]\n\t"
      94             :                     "adcq 5*8(%[src]),%[tmp_accum]\n\t"
      95             :                     "adcq 6*8(%[src]),%[tmp_accum]\n\t"
      96             :                     "adcq 7*8(%[src]),%[tmp_accum]\n\t"
      97             :                     "adcl $0,%k[tmp_carries]\n\t"
      98             :                     "addq $64, %[src]\n\t"
      99             :                     "subl $64, %[len]\n\t"
     100             :                     "jge 1b\n\t"
     101             :                     "addq %[tmp_accum],%[res]\n\t"
     102             :                     "adcq %[tmp_carries],%[res]\n\t"
     103             :                     "adcq $0,%[res]"
     104             :                     : [tmp_accum] "=&r"(tmp_accum),
     105             :                       [tmp_carries] "=&r"(tmp_carries), [res] "+r"(temp64),
     106             :                       [len] "+r"(len), [src] "+r"(buff)
     107             :                     : "m"(*(const char *)buff));
     108             :         }
     109             : 
     110           0 :         if (len & 32) {
     111           0 :                 asm("addq 0*8(%[src]),%[res]\n\t"
     112             :                     "adcq 1*8(%[src]),%[res]\n\t"
     113             :                     "adcq 2*8(%[src]),%[res]\n\t"
     114             :                     "adcq 3*8(%[src]),%[res]\n\t"
     115             :                     "adcq $0,%[res]"
     116             :                     : [res] "+r"(temp64)
     117             :                     : [src] "r"(buff), "m"(*(const char(*)[32])buff));
     118           0 :                 buff += 32;
     119             :         }
     120           0 :         if (len & 16) {
     121           0 :                 asm("addq 0*8(%[src]),%[res]\n\t"
     122             :                     "adcq 1*8(%[src]),%[res]\n\t"
     123             :                     "adcq $0,%[res]"
     124             :                     : [res] "+r"(temp64)
     125             :                     : [src] "r"(buff), "m"(*(const char(*)[16])buff));
     126           0 :                 buff += 16;
     127             :         }
     128           0 :         if (len & 8) {
     129           0 :                 asm("addq 0*8(%[src]),%[res]\n\t"
     130             :                     "adcq $0,%[res]"
     131             :                     : [res] "+r"(temp64)
     132             :                     : [src] "r"(buff), "m"(*(const char(*)[8])buff));
     133           0 :                 buff += 8;
     134             :         }
     135           0 :         if (len & 7) {
     136           0 :                 unsigned int shift = (-len << 3) & 63;
     137             :                 unsigned long trail;
     138             : 
     139           0 :                 trail = (load_unaligned_zeropad(buff) << shift) >> shift;
     140             : 
     141           0 :                 asm("addq %[trail],%[res]\n\t"
     142             :                     "adcq $0,%[res]"
     143             :                     : [res] "+r"(temp64)
     144             :                     : [trail] "r"(trail));
     145             :         }
     146           0 :         return csum_tail(temp64, odd);
     147             : }
     148             : EXPORT_SYMBOL(csum_partial);
     149             : 
     150             : /*
     151             :  * this routine is used for miscellaneous IP-like checksums, mainly
     152             :  * in icmp.c
     153             :  */
     154           0 : __sum16 ip_compute_csum(const void *buff, int len)
     155             : {
     156           0 :         return csum_fold(csum_partial(buff, len, 0));
     157             : }
     158             : EXPORT_SYMBOL(ip_compute_csum);