fs/btrfs/crc32c.h

   1 /*
   2  * Copyright (C) 2008 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #ifndef __BTRFS_CRC32C__
  20 #define __BTRFS_CRC32C__
  21 #include <asm/byteorder.h>
  22 #include <linux/crc32c.h>
  23 #include <linux/version.h>
  24
  25 /* #define CONFIG_BTRFS_HW_SUM 1 */
  26
  27 #ifdef CONFIG_BTRFS_HW_SUM
  28 #ifdef CONFIG_X86
  29 /*
  30  * Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
  31  * CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
  32  * CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
  33  * http://www.intel.com/products/processor/manuals/
  34  * Intel(R) 64 and IA-32 Architectures Software Developer's Manual
  35  * Volume 2A: Instruction Set Reference, A-M
  36  */
  37
  38 #include <asm/cpufeature.h>
  39 #include <asm/processor.h>
  40
  41 #define X86_FEATURE_XMM4_2     (4*32+20) /* Streaming SIMD Extensions-4.2 */
  42 #define cpu_has_xmm4_2         boot_cpu_has(X86_FEATURE_XMM4_2)
  43
  44 #ifdef CONFIG_X86_64
  45 #define REX_PRE "0x48, "
  46 #define SCALE_F 8
  47 #else
  48 #define REX_PRE
  49 #define SCALE_F 4
  50 #endif
  51
  52 static inline u32 btrfs_crc32c_le_hw_byte(u32 crc, unsigned char const *data,
  53                                    size_t length)
  54 {
  55         while (length--) {
  56                 __asm__ __volatile__(
  57                         ".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
  58                         :"=S"(crc)
  59                         :"0"(crc), "c"(*data)
  60                 );
  61                 data++;
  62         }
  63
  64         return crc;
  65 }
  66
  67 static inline u32 __pure btrfs_crc32c_le_hw(u32 crc, unsigned char const *p,
  68                                      size_t len)
  69 {
  70         unsigned int iquotient = len / SCALE_F;
  71         unsigned int iremainder = len % SCALE_F;
  72 #ifdef CONFIG_X86_64
  73         u64 *ptmp = (u64 *)p;
  74 #else
  75         u32 *ptmp = (u32 *)p;
  76 #endif
  77
  78         while (iquotient--) {
  79                 __asm__ __volatile__(
  80                         ".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
  81                         :"=S"(crc)
  82                         :"0"(crc), "c"(*ptmp)
  83                 );
  84                 ptmp++;
  85         }
  86
  87         if (iremainder)
  88                 crc = btrfs_crc32c_le_hw_byte(crc, (unsigned char *)ptmp,
  89                                               iremainder);
  90
  91         return crc;
  92 }
  93 #endif /* CONFIG_BTRFS_HW_SUM */
  94
  95 static inline u32 __btrfs_crc32c(u32 crc, unsigned char const *address,
  96                                  size_t len)
  97 {
  98 #ifdef CONFIG_BTRFS_HW_SUM
  99         if (cpu_has_xmm4_2)
 100                 return btrfs_crc32c_le_hw(crc, address, len);
 101 #endif
 102         return crc32c_le(crc, address, len);
 103 }
 104
 105 #else
 106
 107 #define __btrfs_crc32c(seed, data, length) crc32c(seed, data, length)
 108
 109 #endif /* CONFIG_X86 */
 110
 111 /**
 112  * implementation of crc32c_le() changed in linux-2.6.23,
 113  * has of v0.13 btrfs-progs is using the latest version.
 114  * We must workaround older implementations of crc32c_le()
 115  * found on older kernel versions.
 116  */
 117 #define btrfs_crc32c(seed, data, length) \
 118         __btrfs_crc32c(seed, (unsigned char const *)data, length)
 119 #endif
 120