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      1 #include <inttypes.h>
      2 #include <string.h>
      3 #include <unistd.h>
      4 #include <stdlib.h>
      5 #include <signal.h>
      6 #include <sys/types.h>
      7 #include <sys/wait.h>
      8 #include "crc32c.h"
      9 
     10 /*
     11  * Based on a posting to lkml by Austin Zhang <austin.zhang (at) intel.com>
     12  *
     13  * Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
     14  * CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
     15  * CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
     16  * http://www.intel.com/products/processor/manuals/
     17  * Intel(R) 64 and IA-32 Architectures Software Developer's Manual
     18  * Volume 2A: Instruction Set Reference, A-M
     19  */
     20 
     21 int crc32c_intel_available = 0;
     22 
     23 #ifdef ARCH_HAVE_SSE4_2
     24 
     25 #if BITS_PER_LONG == 64
     26 #define REX_PRE "0x48, "
     27 #define SCALE_F 8
     28 #else
     29 #define REX_PRE
     30 #define SCALE_F 4
     31 #endif
     32 
     33 static int crc32c_probed;
     34 
     35 static uint32_t crc32c_intel_le_hw_byte(uint32_t crc, unsigned char const *data,
     36 					unsigned long length)
     37 {
     38 	while (length--) {
     39 		__asm__ __volatile__(
     40 			".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
     41 			:"=S"(crc)
     42 			:"0"(crc), "c"(*data)
     43 		);
     44 		data++;
     45 	}
     46 
     47 	return crc;
     48 }
     49 
     50 /*
     51  * Steps through buffer one byte at at time, calculates reflected
     52  * crc using table.
     53  */
     54 uint32_t crc32c_intel(unsigned char const *data, unsigned long length)
     55 {
     56 	unsigned int iquotient = length / SCALE_F;
     57 	unsigned int iremainder = length % SCALE_F;
     58 #if BITS_PER_LONG == 64
     59 	uint64_t *ptmp = (uint64_t *) data;
     60 #else
     61 	uint32_t *ptmp = (uint32_t *) data;
     62 #endif
     63 	uint32_t crc = ~0;
     64 
     65 	while (iquotient--) {
     66 		__asm__ __volatile__(
     67 			".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
     68 			:"=S"(crc)
     69 			:"0"(crc), "c"(*ptmp)
     70 		);
     71 		ptmp++;
     72 	}
     73 
     74 	if (iremainder)
     75 		crc = crc32c_intel_le_hw_byte(crc, (unsigned char *)ptmp,
     76 				 iremainder);
     77 
     78 	return crc;
     79 }
     80 
     81 void crc32c_intel_probe(void)
     82 {
     83 	if (!crc32c_probed) {
     84 		unsigned int eax, ebx, ecx = 0, edx;
     85 
     86 		eax = 1;
     87 
     88 		do_cpuid(&eax, &ebx, &ecx, &edx);
     89 		crc32c_intel_available = (ecx & (1 << 20)) != 0;
     90 		crc32c_probed = 1;
     91 	}
     92 }
     93 
     94 #endif /* ARCH_HAVE_SSE */
     95