Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * arch/x86_64/lib/csum-partial.c |
| 3 | * |
| 4 | * This file contains network checksum routines that are better done |
| 5 | * in an architecture-specific manner due to speed. |
| 6 | */ |
| 7 | |
| 8 | #include <linux/compiler.h> |
| 9 | #include <linux/module.h> |
| 10 | #include <asm/checksum.h> |
| 11 | |
| 12 | #define __force_inline inline __attribute__((always_inline)) |
| 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 64-bit 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 | * Things tried and found to not make it faster: |
| 32 | * Manual Prefetching |
| 33 | * Unrolling to an 128 bytes inner loop. |
| 34 | * Using interleaving with more registers to break the carry chains. |
| 35 | */ |
| 36 | static __force_inline unsigned do_csum(const unsigned char *buff, unsigned len) |
| 37 | { |
| 38 | unsigned odd, count; |
| 39 | unsigned long result = 0; |
| 40 | |
| 41 | if (unlikely(len == 0)) |
| 42 | return result; |
| 43 | odd = 1 & (unsigned long) buff; |
| 44 | if (unlikely(odd)) { |
| 45 | result = *buff << 8; |
| 46 | len--; |
| 47 | buff++; |
| 48 | } |
| 49 | count = len >> 1; /* nr of 16-bit words.. */ |
| 50 | if (count) { |
| 51 | if (2 & (unsigned long) buff) { |
| 52 | result += *(unsigned short *)buff; |
| 53 | count--; |
| 54 | len -= 2; |
| 55 | buff += 2; |
| 56 | } |
| 57 | count >>= 1; /* nr of 32-bit words.. */ |
| 58 | if (count) { |
| 59 | unsigned long zero; |
| 60 | unsigned count64; |
| 61 | if (4 & (unsigned long) buff) { |
| 62 | result += *(unsigned int *) buff; |
| 63 | count--; |
| 64 | len -= 4; |
| 65 | buff += 4; |
| 66 | } |
| 67 | count >>= 1; /* nr of 64-bit words.. */ |
| 68 | |
| 69 | /* main loop using 64byte blocks */ |
| 70 | zero = 0; |
| 71 | count64 = count >> 3; |
| 72 | while (count64) { |
| 73 | asm("addq 0*8(%[src]),%[res]\n\t" |
| 74 | "adcq 1*8(%[src]),%[res]\n\t" |
| 75 | "adcq 2*8(%[src]),%[res]\n\t" |
| 76 | "adcq 3*8(%[src]),%[res]\n\t" |
| 77 | "adcq 4*8(%[src]),%[res]\n\t" |
| 78 | "adcq 5*8(%[src]),%[res]\n\t" |
| 79 | "adcq 6*8(%[src]),%[res]\n\t" |
| 80 | "adcq 7*8(%[src]),%[res]\n\t" |
| 81 | "adcq %[zero],%[res]" |
| 82 | : [res] "=r" (result) |
| 83 | : [src] "r" (buff), [zero] "r" (zero), |
| 84 | "[res]" (result)); |
| 85 | buff += 64; |
| 86 | count64--; |
| 87 | } |
| 88 | |
| 89 | /* last upto 7 8byte blocks */ |
| 90 | count %= 8; |
| 91 | while (count) { |
| 92 | asm("addq %1,%0\n\t" |
| 93 | "adcq %2,%0\n" |
| 94 | : "=r" (result) |
| 95 | : "m" (*(unsigned long *)buff), |
| 96 | "r" (zero), "0" (result)); |
| 97 | --count; |
| 98 | buff += 8; |
| 99 | } |
| 100 | result = add32_with_carry(result>>32, |
| 101 | result&0xffffffff); |
| 102 | |
| 103 | if (len & 4) { |
| 104 | result += *(unsigned int *) buff; |
| 105 | buff += 4; |
| 106 | } |
| 107 | } |
| 108 | if (len & 2) { |
| 109 | result += *(unsigned short *) buff; |
| 110 | buff += 2; |
| 111 | } |
| 112 | } |
| 113 | if (len & 1) |
| 114 | result += *buff; |
| 115 | result = add32_with_carry(result>>32, result & 0xffffffff); |
| 116 | if (unlikely(odd)) { |
| 117 | result = from32to16(result); |
| 118 | result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); |
| 119 | } |
| 120 | return result; |
| 121 | } |
| 122 | |
| 123 | /* |
| 124 | * computes the checksum of a memory block at buff, length len, |
| 125 | * and adds in "sum" (32-bit) |
| 126 | * |
| 127 | * returns a 32-bit number suitable for feeding into itself |
| 128 | * or csum_tcpudp_magic |
| 129 | * |
| 130 | * this function must be called with even lengths, except |
| 131 | * for the last fragment, which may be odd |
| 132 | * |
| 133 | * it's best to have buff aligned on a 64-bit boundary |
| 134 | */ |
| 135 | unsigned csum_partial(const unsigned char *buff, unsigned len, unsigned sum) |
| 136 | { |
| 137 | return add32_with_carry(do_csum(buff, len), sum); |
| 138 | } |
| 139 | |
| 140 | EXPORT_SYMBOL(csum_partial); |
| 141 | |
| 142 | /* |
| 143 | * this routine is used for miscellaneous IP-like checksums, mainly |
| 144 | * in icmp.c |
| 145 | */ |
| 146 | unsigned short ip_compute_csum(unsigned char * buff, int len) |
| 147 | { |
| 148 | return csum_fold(csum_partial(buff,len,0)); |
| 149 | } |
Andi Kleen | 2ee60e17 | 2006-06-26 13:59:44 +0200 | [diff] [blame] | 150 | EXPORT_SYMBOL(ip_compute_csum); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 151 | |