fs/btrfs/crc32c.h

   1 #ifndef __BTRFS_CRC32C__
   2 #define __BTRFS_CRC32C__
   3 #include <asm/byteorder.h>
   4 #include <linux/crc32c.h>
   5 #include <linux/version.h>
   6
   7 /* #define CONFIG_BTRFS_HW_SUM 1 */
   8
   9 #ifdef CONFIG_BTRFS_HW_SUM
  10 #ifdef CONFIG_X86
  11 /*
  12  * Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
  13  * CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
  14  * CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
  15  * http://www.intel.com/products/processor/manuals/
  16  * Intel(R) 64 and IA-32 Architectures Software Developer's Manual
  17  * Volume 2A: Instruction Set Reference, A-M
  18  */
  19
  20 #include <asm/cpufeature.h>
  21 #include <asm/processor.h>
  22
  23 #define X86_FEATURE_XMM4_2     (4*32+20) /* Streaming SIMD Extensions-4.2 */
  24 #define cpu_has_xmm4_2         boot_cpu_has(X86_FEATURE_XMM4_2)
  25
  26 #ifdef CONFIG_X86_64
  27 #define REX_PRE "0x48, "
  28 #define SCALE_F 8
  29 #else
  30 #define REX_PRE
  31 #define SCALE_F 4
  32 #endif
  33
  34 static inline u32 btrfs_crc32c_le_hw_byte(u32 crc, unsigned char const *data,
  35                                    size_t length)
  36 {
  37         while (length--) {
  38                 __asm__ __volatile__(
  39                         ".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
  40                         :"=S"(crc)
  41                         :"0"(crc), "c"(*data)
  42                 );
  43                 data++;
  44         }
  45
  46         return crc;
  47 }
  48
  49 static inline u32 __pure btrfs_crc32c_le_hw(u32 crc, unsigned char const *p,
  50                                      size_t len)
  51 {
  52         unsigned int iquotient = len / SCALE_F;
  53         unsigned int iremainder = len % SCALE_F;
  54 #ifdef CONFIG_X86_64
  55         u64 *ptmp = (u64 *)p;
  56 #else
  57         u32 *ptmp = (u32 *)p;
  58 #endif
  59
  60         while (iquotient--) {
  61                 __asm__ __volatile__(
  62                         ".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
  63                         :"=S"(crc)
  64                         :"0"(crc), "c"(*ptmp)
  65                 );
  66                 ptmp++;
  67         }
  68
  69         if (iremainder)
  70                 crc = btrfs_crc32c_le_hw_byte(crc, (unsigned char *)ptmp,
  71                                               iremainder);
  72
  73         return crc;
  74 }
  75 #endif /* CONFIG_BTRFS_HW_SUM */
  76
  77 static inline u32 __btrfs_crc32c(u32 crc, unsigned char const *address,
  78                                  size_t len)
  79 {
  80 #ifdef CONFIG_BTRFS_HW_SUM
  81         if (cpu_has_xmm4_2)
  82                 return btrfs_crc32c_le_hw(crc, address, len);
  83 #endif
  84         return crc32c_le(crc, address, len);
  85 }
  86
  87 #else
  88
  89 #define __btrfs_crc32c(seed, data, length) crc32c(seed, data, length)
  90
  91 #endif /* CONFIG_X86 */
  92
  93 /**
  94  * implementation of crc32c_le() changed in linux-2.6.23,
  95  * has of v0.13 btrfs-progs is using the latest version.
  96  * We must workaround older implementations of crc32c_le()
  97  * found on older kernel versions.
  98  */
  99 #define btrfs_crc32c(seed, data, length) \
 100         __btrfs_crc32c(seed, (unsigned char const *)data, length)
 101 #endif
 102