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150 lines
3.5 KiB
150 lines
3.5 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* arch/x86_64/lib/csum-partial.c |
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* |
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* This file contains network checksum routines that are better done |
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* in an architecture-specific manner due to speed. |
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*/ |
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#include <linux/compiler.h> |
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#include <linux/export.h> |
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#include <asm/checksum.h> |
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static inline unsigned short from32to16(unsigned a) |
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{ |
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unsigned short b = a >> 16; |
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asm("addw %w2,%w0\n\t" |
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"adcw $0,%w0\n" |
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: "=r" (b) |
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: "0" (b), "r" (a)); |
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return b; |
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} |
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/* |
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* Do a 64-bit checksum on an arbitrary memory area. |
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* Returns a 32bit checksum. |
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* |
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* This isn't as time critical as it used to be because many NICs |
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* do hardware checksumming these days. |
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* |
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* Things tried and found to not make it faster: |
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* Manual Prefetching |
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* Unrolling to an 128 bytes inner loop. |
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* Using interleaving with more registers to break the carry chains. |
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*/ |
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static unsigned do_csum(const unsigned char *buff, unsigned len) |
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{ |
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unsigned odd, count; |
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unsigned long result = 0; |
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if (unlikely(len == 0)) |
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return result; |
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odd = 1 & (unsigned long) buff; |
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if (unlikely(odd)) { |
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result = *buff << 8; |
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len--; |
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buff++; |
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} |
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count = len >> 1; /* nr of 16-bit words.. */ |
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if (count) { |
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if (2 & (unsigned long) buff) { |
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result += *(unsigned short *)buff; |
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count--; |
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len -= 2; |
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buff += 2; |
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} |
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count >>= 1; /* nr of 32-bit words.. */ |
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if (count) { |
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unsigned long zero; |
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unsigned count64; |
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if (4 & (unsigned long) buff) { |
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result += *(unsigned int *) buff; |
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count--; |
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len -= 4; |
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buff += 4; |
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} |
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count >>= 1; /* nr of 64-bit words.. */ |
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/* main loop using 64byte blocks */ |
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zero = 0; |
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count64 = count >> 3; |
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while (count64) { |
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asm("addq 0*8(%[src]),%[res]\n\t" |
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"adcq 1*8(%[src]),%[res]\n\t" |
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"adcq 2*8(%[src]),%[res]\n\t" |
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"adcq 3*8(%[src]),%[res]\n\t" |
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"adcq 4*8(%[src]),%[res]\n\t" |
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"adcq 5*8(%[src]),%[res]\n\t" |
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"adcq 6*8(%[src]),%[res]\n\t" |
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"adcq 7*8(%[src]),%[res]\n\t" |
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"adcq %[zero],%[res]" |
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: [res] "=r" (result) |
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: [src] "r" (buff), [zero] "r" (zero), |
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"[res]" (result)); |
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buff += 64; |
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count64--; |
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} |
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/* last up to 7 8byte blocks */ |
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count %= 8; |
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while (count) { |
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asm("addq %1,%0\n\t" |
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"adcq %2,%0\n" |
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: "=r" (result) |
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: "m" (*(unsigned long *)buff), |
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"r" (zero), "0" (result)); |
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--count; |
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buff += 8; |
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} |
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result = add32_with_carry(result>>32, |
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result&0xffffffff); |
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if (len & 4) { |
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result += *(unsigned int *) buff; |
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buff += 4; |
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} |
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} |
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if (len & 2) { |
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result += *(unsigned short *) buff; |
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buff += 2; |
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} |
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} |
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if (len & 1) |
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result += *buff; |
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result = add32_with_carry(result>>32, result & 0xffffffff); |
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if (unlikely(odd)) { |
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result = from32to16(result); |
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result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); |
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} |
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return result; |
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} |
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/* |
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* computes the checksum of a memory block at buff, length len, |
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* and adds in "sum" (32-bit) |
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* |
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* returns a 32-bit number suitable for feeding into itself |
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* or csum_tcpudp_magic |
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* |
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* this function must be called with even lengths, except |
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* for the last fragment, which may be odd |
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* |
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* it's best to have buff aligned on a 64-bit boundary |
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*/ |
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__wsum csum_partial(const void *buff, int len, __wsum sum) |
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{ |
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return (__force __wsum)add32_with_carry(do_csum(buff, len), |
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(__force u32)sum); |
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} |
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EXPORT_SYMBOL(csum_partial); |
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/* |
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* this routine is used for miscellaneous IP-like checksums, mainly |
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* in icmp.c |
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*/ |
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__sum16 ip_compute_csum(const void *buff, int len) |
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{ |
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return csum_fold(csum_partial(buff,len,0)); |
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} |
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EXPORT_SYMBOL(ip_compute_csum); |
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