94 lines
1.9 KiB
C
94 lines
1.9 KiB
C
#include <inttypes.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include "crc32c.h"
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/*
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* Based on a posting to lkml by Austin Zhang <austin.zhang@intel.com>
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*
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* Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
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* CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
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* CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
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* http://www.intel.com/products/processor/manuals/
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* Intel(R) 64 and IA-32 Architectures Software Developer's Manual
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* Volume 2A: Instruction Set Reference, A-M
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*/
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int crc32c_intel_available = 0;
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#ifdef ARCH_HAVE_SSE4_2
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#if BITS_PER_LONG == 64
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#define REX_PRE "0x48, "
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#define SCALE_F 8
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#else
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#define REX_PRE
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#define SCALE_F 4
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#endif
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static int crc32c_probed;
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static uint32_t crc32c_intel_le_hw_byte(uint32_t crc, unsigned char const *data,
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unsigned long length)
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{
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while (length--) {
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__asm__ __volatile__(
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".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
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:"=S"(crc)
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:"0"(crc), "c"(*data)
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);
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data++;
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}
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return crc;
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}
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/*
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* Steps through buffer one byte at at time, calculates reflected
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* crc using table.
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*/
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uint32_t crc32c_intel(unsigned char const *data, unsigned long length)
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{
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unsigned int iquotient = length / SCALE_F;
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unsigned int iremainder = length % SCALE_F;
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#if BITS_PER_LONG == 64
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uint64_t *ptmp = (uint64_t *) data;
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#else
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uint32_t *ptmp = (uint32_t *) data;
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#endif
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uint32_t crc = ~0;
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while (iquotient--) {
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__asm__ __volatile__(
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".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
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:"=S"(crc)
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:"0"(crc), "c"(*ptmp)
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);
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ptmp++;
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}
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if (iremainder)
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crc = crc32c_intel_le_hw_byte(crc, (unsigned char *)ptmp,
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iremainder);
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return crc;
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}
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void crc32c_intel_probe(void)
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{
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if (!crc32c_probed) {
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unsigned int eax, ebx, ecx = 0, edx;
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eax = 1;
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do_cpuid(&eax, &ebx, &ecx, &edx);
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crc32c_intel_available = (ecx & (1 << 20)) != 0;
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crc32c_probed = 1;
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}
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}
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#endif /* ARCH_HAVE_SSE */
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