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); 124