1######################################################################## 2# Implement fast CRC-T10DIF computation with SSE and PCLMULQDQ instructions 3# 4# Copyright (c) 2013, Intel Corporation 5# 6# Authors: 7# Erdinc Ozturk <erdinc.ozturk@intel.com> 8# Vinodh Gopal <vinodh.gopal@intel.com> 9# James Guilford <james.guilford@intel.com> 10# Tim Chen <tim.c.chen@linux.intel.com> 11# 12# This software is available to you under a choice of one of two 13# licenses. You may choose to be licensed under the terms of the GNU 14# General Public License (GPL) Version 2, available from the file 15# COPYING in the main directory of this source tree, or the 16# OpenIB.org BSD license below: 17# 18# Redistribution and use in source and binary forms, with or without 19# modification, are permitted provided that the following conditions are 20# met: 21# 22# * Redistributions of source code must retain the above copyright 23# notice, this list of conditions and the following disclaimer. 24# 25# * Redistributions in binary form must reproduce the above copyright 26# notice, this list of conditions and the following disclaimer in the 27# documentation and/or other materials provided with the 28# distribution. 29# 30# * Neither the name of the Intel Corporation nor the names of its 31# contributors may be used to endorse or promote products derived from 32# this software without specific prior written permission. 33# 34# 35# THIS SOFTWARE IS PROVIDED BY INTEL CORPORATION ""AS IS"" AND ANY 36# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 37# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 38# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL CORPORATION OR 39# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 40# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 41# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 42# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 43# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 44# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 45# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 46# 47# Reference paper titled "Fast CRC Computation for Generic 48# Polynomials Using PCLMULQDQ Instruction" 49# URL: http://www.intel.com/content/dam/www/public/us/en/documents 50# /white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf 51# 52 53#include <linux/linkage.h> 54 55.text 56 57#define init_crc %edi 58#define buf %rsi 59#define len %rdx 60 61#define FOLD_CONSTS %xmm10 62#define BSWAP_MASK %xmm11 63 64# Fold reg1, reg2 into the next 32 data bytes, storing the result back into 65# reg1, reg2. 66.macro fold_32_bytes offset, reg1, reg2 67 movdqu \offset(buf), %xmm9 68 movdqu \offset+16(buf), %xmm12 69 pshufb BSWAP_MASK, %xmm9 70 pshufb BSWAP_MASK, %xmm12 71 movdqa \reg1, %xmm8 72 movdqa \reg2, %xmm13 73 pclmulqdq $0x00, FOLD_CONSTS, \reg1 74 pclmulqdq $0x11, FOLD_CONSTS, %xmm8 75 pclmulqdq $0x00, FOLD_CONSTS, \reg2 76 pclmulqdq $0x11, FOLD_CONSTS, %xmm13 77 pxor %xmm9 , \reg1 78 xorps %xmm8 , \reg1 79 pxor %xmm12, \reg2 80 xorps %xmm13, \reg2 81.endm 82 83# Fold src_reg into dst_reg. 84.macro fold_16_bytes src_reg, dst_reg 85 movdqa \src_reg, %xmm8 86 pclmulqdq $0x11, FOLD_CONSTS, \src_reg 87 pclmulqdq $0x00, FOLD_CONSTS, %xmm8 88 pxor %xmm8, \dst_reg 89 xorps \src_reg, \dst_reg 90.endm 91 92# 93# u16 crc_t10dif_pcl(u16 init_crc, const *u8 buf, size_t len); 94# 95# Assumes len >= 16. 96# 97SYM_FUNC_START(crc_t10dif_pcl) 98 99 movdqa .Lbswap_mask(%rip), BSWAP_MASK 100 101 # For sizes less than 256 bytes, we can't fold 128 bytes at a time. 102 cmp $256, len 103 jl .Lless_than_256_bytes 104 105 # Load the first 128 data bytes. Byte swapping is necessary to make the 106 # bit order match the polynomial coefficient order. 107 movdqu 16*0(buf), %xmm0 108 movdqu 16*1(buf), %xmm1 109 movdqu 16*2(buf), %xmm2 110 movdqu 16*3(buf), %xmm3 111 movdqu 16*4(buf), %xmm4 112 movdqu 16*5(buf), %xmm5 113 movdqu 16*6(buf), %xmm6 114 movdqu 16*7(buf), %xmm7 115 add $128, buf 116 pshufb BSWAP_MASK, %xmm0 117 pshufb BSWAP_MASK, %xmm1 118 pshufb BSWAP_MASK, %xmm2 119 pshufb BSWAP_MASK, %xmm3 120 pshufb BSWAP_MASK, %xmm4 121 pshufb BSWAP_MASK, %xmm5 122 pshufb BSWAP_MASK, %xmm6 123 pshufb BSWAP_MASK, %xmm7 124 125 # XOR the first 16 data *bits* with the initial CRC value. 126 pxor %xmm8, %xmm8 127 pinsrw $7, init_crc, %xmm8 128 pxor %xmm8, %xmm0 129 130 movdqa .Lfold_across_128_bytes_consts(%rip), FOLD_CONSTS 131 132 # Subtract 128 for the 128 data bytes just consumed. Subtract another 133 # 128 to simplify the termination condition of the following loop. 134 sub $256, len 135 136 # While >= 128 data bytes remain (not counting xmm0-7), fold the 128 137 # bytes xmm0-7 into them, storing the result back into xmm0-7. 138.Lfold_128_bytes_loop: 139 fold_32_bytes 0, %xmm0, %xmm1 140 fold_32_bytes 32, %xmm2, %xmm3 141 fold_32_bytes 64, %xmm4, %xmm5 142 fold_32_bytes 96, %xmm6, %xmm7 143 add $128, buf 144 sub $128, len 145 jge .Lfold_128_bytes_loop 146 147 # Now fold the 112 bytes in xmm0-xmm6 into the 16 bytes in xmm7. 148 149 # Fold across 64 bytes. 150 movdqa .Lfold_across_64_bytes_consts(%rip), FOLD_CONSTS 151 fold_16_bytes %xmm0, %xmm4 152 fold_16_bytes %xmm1, %xmm5 153 fold_16_bytes %xmm2, %xmm6 154 fold_16_bytes %xmm3, %xmm7 155 # Fold across 32 bytes. 156 movdqa .Lfold_across_32_bytes_consts(%rip), FOLD_CONSTS 157 fold_16_bytes %xmm4, %xmm6 158 fold_16_bytes %xmm5, %xmm7 159 # Fold across 16 bytes. 160 movdqa .Lfold_across_16_bytes_consts(%rip), FOLD_CONSTS 161 fold_16_bytes %xmm6, %xmm7 162 163 # Add 128 to get the correct number of data bytes remaining in 0...127 164 # (not counting xmm7), following the previous extra subtraction by 128. 165 # Then subtract 16 to simplify the termination condition of the 166 # following loop. 167 add $128-16, len 168 169 # While >= 16 data bytes remain (not counting xmm7), fold the 16 bytes 170 # xmm7 into them, storing the result back into xmm7. 171 jl .Lfold_16_bytes_loop_done 172.Lfold_16_bytes_loop: 173 movdqa %xmm7, %xmm8 174 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 175 pclmulqdq $0x00, FOLD_CONSTS, %xmm8 176 pxor %xmm8, %xmm7 177 movdqu (buf), %xmm0 178 pshufb BSWAP_MASK, %xmm0 179 pxor %xmm0 , %xmm7 180 add $16, buf 181 sub $16, len 182 jge .Lfold_16_bytes_loop 183 184.Lfold_16_bytes_loop_done: 185 # Add 16 to get the correct number of data bytes remaining in 0...15 186 # (not counting xmm7), following the previous extra subtraction by 16. 187 add $16, len 188 je .Lreduce_final_16_bytes 189 190.Lhandle_partial_segment: 191 # Reduce the last '16 + len' bytes where 1 <= len <= 15 and the first 16 192 # bytes are in xmm7 and the rest are the remaining data in 'buf'. To do 193 # this without needing a fold constant for each possible 'len', redivide 194 # the bytes into a first chunk of 'len' bytes and a second chunk of 16 195 # bytes, then fold the first chunk into the second. 196 197 movdqa %xmm7, %xmm2 198 199 # xmm1 = last 16 original data bytes 200 movdqu -16(buf, len), %xmm1 201 pshufb BSWAP_MASK, %xmm1 202 203 # xmm2 = high order part of second chunk: xmm7 left-shifted by 'len' bytes. 204 lea .Lbyteshift_table+16(%rip), %rax 205 sub len, %rax 206 movdqu (%rax), %xmm0 207 pshufb %xmm0, %xmm2 208 209 # xmm7 = first chunk: xmm7 right-shifted by '16-len' bytes. 210 pxor .Lmask1(%rip), %xmm0 211 pshufb %xmm0, %xmm7 212 213 # xmm1 = second chunk: 'len' bytes from xmm1 (low-order bytes), 214 # then '16-len' bytes from xmm2 (high-order bytes). 215 pblendvb %xmm2, %xmm1 #xmm0 is implicit 216 217 # Fold the first chunk into the second chunk, storing the result in xmm7. 218 movdqa %xmm7, %xmm8 219 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 220 pclmulqdq $0x00, FOLD_CONSTS, %xmm8 221 pxor %xmm8, %xmm7 222 pxor %xmm1, %xmm7 223 224.Lreduce_final_16_bytes: 225 # Reduce the 128-bit value M(x), stored in xmm7, to the final 16-bit CRC 226 227 # Load 'x^48 * (x^48 mod G(x))' and 'x^48 * (x^80 mod G(x))'. 228 movdqa .Lfinal_fold_consts(%rip), FOLD_CONSTS 229 230 # Fold the high 64 bits into the low 64 bits, while also multiplying by 231 # x^64. This produces a 128-bit value congruent to x^64 * M(x) and 232 # whose low 48 bits are 0. 233 movdqa %xmm7, %xmm0 234 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 # high bits * x^48 * (x^80 mod G(x)) 235 pslldq $8, %xmm0 236 pxor %xmm0, %xmm7 # + low bits * x^64 237 238 # Fold the high 32 bits into the low 96 bits. This produces a 96-bit 239 # value congruent to x^64 * M(x) and whose low 48 bits are 0. 240 movdqa %xmm7, %xmm0 241 pand .Lmask2(%rip), %xmm0 # zero high 32 bits 242 psrldq $12, %xmm7 # extract high 32 bits 243 pclmulqdq $0x00, FOLD_CONSTS, %xmm7 # high 32 bits * x^48 * (x^48 mod G(x)) 244 pxor %xmm0, %xmm7 # + low bits 245 246 # Load G(x) and floor(x^48 / G(x)). 247 movdqa .Lbarrett_reduction_consts(%rip), FOLD_CONSTS 248 249 # Use Barrett reduction to compute the final CRC value. 250 movdqa %xmm7, %xmm0 251 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 # high 32 bits * floor(x^48 / G(x)) 252 psrlq $32, %xmm7 # /= x^32 253 pclmulqdq $0x00, FOLD_CONSTS, %xmm7 # *= G(x) 254 psrlq $48, %xmm0 255 pxor %xmm7, %xmm0 # + low 16 nonzero bits 256 # Final CRC value (x^16 * M(x)) mod G(x) is in low 16 bits of xmm0. 257 258 pextrw $0, %xmm0, %eax 259 RET 260 261.align 16 262.Lless_than_256_bytes: 263 # Checksumming a buffer of length 16...255 bytes 264 265 # Load the first 16 data bytes. 266 movdqu (buf), %xmm7 267 pshufb BSWAP_MASK, %xmm7 268 add $16, buf 269 270 # XOR the first 16 data *bits* with the initial CRC value. 271 pxor %xmm0, %xmm0 272 pinsrw $7, init_crc, %xmm0 273 pxor %xmm0, %xmm7 274 275 movdqa .Lfold_across_16_bytes_consts(%rip), FOLD_CONSTS 276 cmp $16, len 277 je .Lreduce_final_16_bytes # len == 16 278 sub $32, len 279 jge .Lfold_16_bytes_loop # 32 <= len <= 255 280 add $16, len 281 jmp .Lhandle_partial_segment # 17 <= len <= 31 282SYM_FUNC_END(crc_t10dif_pcl) 283 284.section .rodata, "a", @progbits 285.align 16 286 287# Fold constants precomputed from the polynomial 0x18bb7 288# G(x) = x^16 + x^15 + x^11 + x^9 + x^8 + x^7 + x^5 + x^4 + x^2 + x^1 + x^0 289.Lfold_across_128_bytes_consts: 290 .quad 0x0000000000006123 # x^(8*128) mod G(x) 291 .quad 0x0000000000002295 # x^(8*128+64) mod G(x) 292.Lfold_across_64_bytes_consts: 293 .quad 0x0000000000001069 # x^(4*128) mod G(x) 294 .quad 0x000000000000dd31 # x^(4*128+64) mod G(x) 295.Lfold_across_32_bytes_consts: 296 .quad 0x000000000000857d # x^(2*128) mod G(x) 297 .quad 0x0000000000007acc # x^(2*128+64) mod G(x) 298.Lfold_across_16_bytes_consts: 299 .quad 0x000000000000a010 # x^(1*128) mod G(x) 300 .quad 0x0000000000001faa # x^(1*128+64) mod G(x) 301.Lfinal_fold_consts: 302 .quad 0x1368000000000000 # x^48 * (x^48 mod G(x)) 303 .quad 0x2d56000000000000 # x^48 * (x^80 mod G(x)) 304.Lbarrett_reduction_consts: 305 .quad 0x0000000000018bb7 # G(x) 306 .quad 0x00000001f65a57f8 # floor(x^48 / G(x)) 307 308.section .rodata.cst16.mask1, "aM", @progbits, 16 309.align 16 310.Lmask1: 311 .octa 0x80808080808080808080808080808080 312 313.section .rodata.cst16.mask2, "aM", @progbits, 16 314.align 16 315.Lmask2: 316 .octa 0x00000000FFFFFFFFFFFFFFFFFFFFFFFF 317 318.section .rodata.cst16.bswap_mask, "aM", @progbits, 16 319.align 16 320.Lbswap_mask: 321 .octa 0x000102030405060708090A0B0C0D0E0F 322 323.section .rodata.cst32.byteshift_table, "aM", @progbits, 32 324.align 16 325# For 1 <= len <= 15, the 16-byte vector beginning at &byteshift_table[16 - len] 326# is the index vector to shift left by 'len' bytes, and is also {0x80, ..., 327# 0x80} XOR the index vector to shift right by '16 - len' bytes. 328.Lbyteshift_table: 329 .byte 0x0, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87 330 .byte 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f 331 .byte 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7 332 .byte 0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe , 0x0 333