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); 124