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@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
crc32c_intel_le_hw_byte(uint32_t crc,unsigned char const * data,unsigned long length)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 */
crc32c_intel(unsigned char const * data,unsigned long length)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
crc32c_intel_probe(void)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