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 static inline __wsum csum_tail(u64 temp64, int odd) 25 { 26 unsigned int result; 27 28 result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff); 29 if (unlikely(odd)) { 30 result = from32to16(result); 31 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 __wsum csum_partial(const void *buff, int len, __wsum sum) 48 { 49 u64 temp64 = (__force u64)sum; 50 unsigned odd; 51 52 odd = 1 & (unsigned long) buff; 53 if (unlikely(odd)) { 54 if (unlikely(len == 0)) 55 return sum; 56 temp64 = ror32((__force u32)sum, 8); 57 temp64 += (*(unsigned char *)buff << 8); 58 len--; 59 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 if (len == 40) { 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 4*8(%[src]),%[res]\n\t" 73 "adcq $0,%[res]" 74 : [res] "+r"(temp64) 75 : [src] "r"(buff), "m"(*(const char(*)[40])buff)); 76 return csum_tail(temp64, odd); 77 } 78 if (unlikely(len >= 64)) { 79 /* 80 * Extra accumulators for better ILP in the loop. 81 */ 82 u64 tmp_accum, tmp_carries; 83 84 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 if (len & 32) { 111 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 buff += 32; 119 } 120 if (len & 16) { 121 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 buff += 16; 127 } 128 if (len & 8) { 129 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 buff += 8; 134 } 135 if (len & 7) { 136 unsigned int shift = (-len << 3) & 63; 137 unsigned long trail; 138 139 trail = (load_unaligned_zeropad(buff) << shift) >> shift; 140 141 asm("addq %[trail],%[res]\n\t" 142 "adcq $0,%[res]" 143 : [res] "+r"(temp64) 144 : [trail] "r"(trail)); 145 } 146 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 __sum16 ip_compute_csum(const void *buff, int len) 155 { 156 return csum_fold(csum_partial(buff, len, 0)); 157 } 158 EXPORT_SYMBOL(ip_compute_csum); 159