124 lines
3.0 KiB
C
124 lines
3.0 KiB
C
// 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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#include <asm/word-at-a-time.h>
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static inline __wsum csum_finalize_sum(u64 temp64)
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{
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return (__force __wsum)((temp64 + ror64(temp64, 32)) >> 32);
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}
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static inline unsigned long update_csum_40b(unsigned long sum, const unsigned long m[5])
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{
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asm("addq %1,%0\n\t"
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"adcq %2,%0\n\t"
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"adcq %3,%0\n\t"
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"adcq %4,%0\n\t"
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"adcq %5,%0\n\t"
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"adcq $0,%0"
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:"+r" (sum)
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:"m" (m[0]), "m" (m[1]), "m" (m[2]),
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"m" (m[3]), "m" (m[4]));
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return sum;
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}
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/*
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* Do a 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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* Still, with CHECKSUM_COMPLETE this is called to compute
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* checksums on IPv6 headers (40 bytes) and other small parts.
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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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u64 temp64 = (__force u64)sum;
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/* Do two 40-byte chunks in parallel to get better ILP */
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if (likely(len >= 80)) {
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u64 temp64_2 = 0;
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do {
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temp64 = update_csum_40b(temp64, buff);
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temp64_2 = update_csum_40b(temp64_2, buff + 40);
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buff += 80;
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len -= 80;
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} while (len >= 80);
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asm("addq %1,%0\n\t"
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"adcq $0,%0"
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:"+r" (temp64): "r" (temp64_2));
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}
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/*
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* len == 40 is the hot case due to IPv6 headers, so return
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* early for that exact case without checking the tail bytes.
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*/
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if (len >= 40) {
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temp64 = update_csum_40b(temp64, buff);
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len -= 40;
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if (!len)
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return csum_finalize_sum(temp64);
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buff += 40;
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}
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if (len & 32) {
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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 $0,%[res]"
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: [res] "+r"(temp64)
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: [src] "r"(buff), "m"(*(const char(*)[32])buff));
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buff += 32;
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}
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if (len & 16) {
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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 $0,%[res]"
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: [res] "+r"(temp64)
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: [src] "r"(buff), "m"(*(const char(*)[16])buff));
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buff += 16;
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}
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if (len & 8) {
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asm("addq 0*8(%[src]),%[res]\n\t"
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"adcq $0,%[res]"
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: [res] "+r"(temp64)
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: [src] "r"(buff), "m"(*(const char(*)[8])buff));
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buff += 8;
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}
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if (len & 7) {
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unsigned int shift = (-len << 3) & 63;
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unsigned long trail;
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trail = (load_unaligned_zeropad(buff) << shift) >> shift;
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asm("addq %[trail],%[res]\n\t"
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"adcq $0,%[res]"
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: [res] "+r"(temp64)
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: [trail] "r"(trail));
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}
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return csum_finalize_sum(temp64);
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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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