crc/crc32c-intel.c

   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 #ifdef ARCH_HAVE_SSE
  22
  23 #if BITS_PER_LONG == 64
  24 #define REX_PRE "0x48, "
  25 #define SCALE_F 8
  26 #else
  27 #define REX_PRE
  28 #define SCALE_F 4
  29 #endif
  30
  31 uint32_t crc32c_intel_le_hw_byte(uint32_t crc, unsigned char const *data,
  32                                  unsigned long length)
  33 {
  34         while (length--) {
  35                 __asm__ __volatile__(
  36                         ".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
  37                         :"=S"(crc)
  38                         :"0"(crc), "c"(*data)
  39                 );
  40                 data++;
  41         }
  42
  43         return crc;
  44 }
  45
  46 /*
  47  * Steps through buffer one byte at at time, calculates reflected
  48  * crc using table.
  49  */
  50 uint32_t crc32c_intel(unsigned char const *data, unsigned long length)
  51 {
  52         unsigned int iquotient = length / SCALE_F;
  53         unsigned int iremainder = length % SCALE_F;
  54 #if BITS_PER_LONG == 64
  55         uint64_t *ptmp = (uint64_t *) data;
  56 #else
  57         uint32_t *ptmp = (uint32_t *) data;
  58 #endif
  59         uint32_t crc = ~0;
  60
  61         while (iquotient--) {
  62                 __asm__ __volatile__(
  63                         ".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
  64                         :"=S"(crc)
  65                         :"0"(crc), "c"(*ptmp)
  66                 );
  67                 ptmp++;
  68         }
  69
  70         if (iremainder)
  71                 crc = crc32c_intel_le_hw_byte(crc, (unsigned char *)ptmp,
  72                                  iremainder);
  73
  74         return crc;
  75 }
  76
  77 static void sig_ill(int sig)
  78 {
  79 }
  80
  81 static void crc32c_test(void)
  82 {
  83         unsigned char buf[4] = { 1, 2, 3, 4 };
  84         struct sigaction act;
  85
  86         /*
  87          * Check if hw accelerated crc32c is available
  88          */
  89         memset(&act, 0, sizeof(act));
  90         act.sa_handler = sig_ill;
  91         act.sa_flags = SA_RESETHAND;
  92         sigaction(SIGILL, &act, NULL);
  93
  94         (void) crc32c_intel(buf, sizeof(buf));
  95 }
  96
  97 int crc32c_intel_works(void)
  98 {
  99         if (!fork()) {
 100                 crc32c_test();
 101                 exit(0);
 102         } else {
 103                 int status;
 104
 105                 wait(&status);
 106                 return !WIFSIGNALED(status);
 107         }
 108 }
 109
 110 #endif /* ARCH_HAVE_SSE */