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# 97.align 16 98SYM_FUNC_START(crc_t10dif_pcl) 99 100 movdqa .Lbswap_mask(%rip), BSWAP_MASK 101 102 # For sizes less than 256 bytes, we can't fold 128 bytes at a time. 103 cmp $256, len 104 jl .Lless_than_256_bytes 105 106 # Load the first 128 data bytes. Byte swapping is necessary to make the 107 # bit order match the polynomial coefficient order. 108 movdqu 16*0(buf), %xmm0 109 movdqu 16*1(buf), %xmm1 110 movdqu 16*2(buf), %xmm2 111 movdqu 16*3(buf), %xmm3 112 movdqu 16*4(buf), %xmm4 113 movdqu 16*5(buf), %xmm5 114 movdqu 16*6(buf), %xmm6 115 movdqu 16*7(buf), %xmm7 116 add $128, buf 117 pshufb BSWAP_MASK, %xmm0 118 pshufb BSWAP_MASK, %xmm1 119 pshufb BSWAP_MASK, %xmm2 120 pshufb BSWAP_MASK, %xmm3 121 pshufb BSWAP_MASK, %xmm4 122 pshufb BSWAP_MASK, %xmm5 123 pshufb BSWAP_MASK, %xmm6 124 pshufb BSWAP_MASK, %xmm7 125 126 # XOR the first 16 data *bits* with the initial CRC value. 127 pxor %xmm8, %xmm8 128 pinsrw $7, init_crc, %xmm8 129 pxor %xmm8, %xmm0 130 131 movdqa .Lfold_across_128_bytes_consts(%rip), FOLD_CONSTS 132 133 # Subtract 128 for the 128 data bytes just consumed. Subtract another 134 # 128 to simplify the termination condition of the following loop. 135 sub $256, len 136 137 # While >= 128 data bytes remain (not counting xmm0-7), fold the 128 138 # bytes xmm0-7 into them, storing the result back into xmm0-7. 139.Lfold_128_bytes_loop: 140 fold_32_bytes 0, %xmm0, %xmm1 141 fold_32_bytes 32, %xmm2, %xmm3 142 fold_32_bytes 64, %xmm4, %xmm5 143 fold_32_bytes 96, %xmm6, %xmm7 144 add $128, buf 145 sub $128, len 146 jge .Lfold_128_bytes_loop 147 148 # Now fold the 112 bytes in xmm0-xmm6 into the 16 bytes in xmm7. 149 150 # Fold across 64 bytes. 151 movdqa .Lfold_across_64_bytes_consts(%rip), FOLD_CONSTS 152 fold_16_bytes %xmm0, %xmm4 153 fold_16_bytes %xmm1, %xmm5 154 fold_16_bytes %xmm2, %xmm6 155 fold_16_bytes %xmm3, %xmm7 156 # Fold across 32 bytes. 157 movdqa .Lfold_across_32_bytes_consts(%rip), FOLD_CONSTS 158 fold_16_bytes %xmm4, %xmm6 159 fold_16_bytes %xmm5, %xmm7 160 # Fold across 16 bytes. 161 movdqa .Lfold_across_16_bytes_consts(%rip), FOLD_CONSTS 162 fold_16_bytes %xmm6, %xmm7 163 164 # Add 128 to get the correct number of data bytes remaining in 0...127 165 # (not counting xmm7), following the previous extra subtraction by 128. 166 # Then subtract 16 to simplify the termination condition of the 167 # following loop. 168 add $128-16, len 169 170 # While >= 16 data bytes remain (not counting xmm7), fold the 16 bytes 171 # xmm7 into them, storing the result back into xmm7. 172 jl .Lfold_16_bytes_loop_done 173.Lfold_16_bytes_loop: 174 movdqa %xmm7, %xmm8 175 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 176 pclmulqdq $0x00, FOLD_CONSTS, %xmm8 177 pxor %xmm8, %xmm7 178 movdqu (buf), %xmm0 179 pshufb BSWAP_MASK, %xmm0 180 pxor %xmm0 , %xmm7 181 add $16, buf 182 sub $16, len 183 jge .Lfold_16_bytes_loop 184 185.Lfold_16_bytes_loop_done: 186 # Add 16 to get the correct number of data bytes remaining in 0...15 187 # (not counting xmm7), following the previous extra subtraction by 16. 188 add $16, len 189 je .Lreduce_final_16_bytes 190 191.Lhandle_partial_segment: 192 # Reduce the last '16 + len' bytes where 1 <= len <= 15 and the first 16 193 # bytes are in xmm7 and the rest are the remaining data in 'buf'. To do 194 # this without needing a fold constant for each possible 'len', redivide 195 # the bytes into a first chunk of 'len' bytes and a second chunk of 16 196 # bytes, then fold the first chunk into the second. 197 198 movdqa %xmm7, %xmm2 199 200 # xmm1 = last 16 original data bytes 201 movdqu -16(buf, len), %xmm1 202 pshufb BSWAP_MASK, %xmm1 203 204 # xmm2 = high order part of second chunk: xmm7 left-shifted by 'len' bytes. 205 lea .Lbyteshift_table+16(%rip), %rax 206 sub len, %rax 207 movdqu (%rax), %xmm0 208 pshufb %xmm0, %xmm2 209 210 # xmm7 = first chunk: xmm7 right-shifted by '16-len' bytes. 211 pxor .Lmask1(%rip), %xmm0 212 pshufb %xmm0, %xmm7 213 214 # xmm1 = second chunk: 'len' bytes from xmm1 (low-order bytes), 215 # then '16-len' bytes from xmm2 (high-order bytes). 216 pblendvb %xmm2, %xmm1 #xmm0 is implicit 217 218 # Fold the first chunk into the second chunk, storing the result in xmm7. 219 movdqa %xmm7, %xmm8 220 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 221 pclmulqdq $0x00, FOLD_CONSTS, %xmm8 222 pxor %xmm8, %xmm7 223 pxor %xmm1, %xmm7 224 225.Lreduce_final_16_bytes: 226 # Reduce the 128-bit value M(x), stored in xmm7, to the final 16-bit CRC 227 228 # Load 'x^48 * (x^48 mod G(x))' and 'x^48 * (x^80 mod G(x))'. 229 movdqa .Lfinal_fold_consts(%rip), FOLD_CONSTS 230 231 # Fold the high 64 bits into the low 64 bits, while also multiplying by 232 # x^64. This produces a 128-bit value congruent to x^64 * M(x) and 233 # whose low 48 bits are 0. 234 movdqa %xmm7, %xmm0 235 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 # high bits * x^48 * (x^80 mod G(x)) 236 pslldq $8, %xmm0 237 pxor %xmm0, %xmm7 # + low bits * x^64 238 239 # Fold the high 32 bits into the low 96 bits. This produces a 96-bit 240 # value congruent to x^64 * M(x) and whose low 48 bits are 0. 241 movdqa %xmm7, %xmm0 242 pand .Lmask2(%rip), %xmm0 # zero high 32 bits 243 psrldq $12, %xmm7 # extract high 32 bits 244 pclmulqdq $0x00, FOLD_CONSTS, %xmm7 # high 32 bits * x^48 * (x^48 mod G(x)) 245 pxor %xmm0, %xmm7 # + low bits 246 247 # Load G(x) and floor(x^48 / G(x)). 248 movdqa .Lbarrett_reduction_consts(%rip), FOLD_CONSTS 249 250 # Use Barrett reduction to compute the final CRC value. 251 movdqa %xmm7, %xmm0 252 pclmulqdq $0x11, FOLD_CONSTS, %xmm7 # high 32 bits * floor(x^48 / G(x)) 253 psrlq $32, %xmm7 # /= x^32 254 pclmulqdq $0x00, FOLD_CONSTS, %xmm7 # *= G(x) 255 psrlq $48, %xmm0 256 pxor %xmm7, %xmm0 # + low 16 nonzero bits 257 # Final CRC value (x^16 * M(x)) mod G(x) is in low 16 bits of xmm0. 258 259 pextrw $0, %xmm0, %eax 260 ret 261 262.align 16 263.Lless_than_256_bytes: 264 # Checksumming a buffer of length 16...255 bytes 265 266 # Load the first 16 data bytes. 267 movdqu (buf), %xmm7 268 pshufb BSWAP_MASK, %xmm7 269 add $16, buf 270 271 # XOR the first 16 data *bits* with the initial CRC value. 272 pxor %xmm0, %xmm0 273 pinsrw $7, init_crc, %xmm0 274 pxor %xmm0, %xmm7 275 276 movdqa .Lfold_across_16_bytes_consts(%rip), FOLD_CONSTS 277 cmp $16, len 278 je .Lreduce_final_16_bytes # len == 16 279 sub $32, len 280 jge .Lfold_16_bytes_loop # 32 <= len <= 255 281 add $16, len 282 jmp .Lhandle_partial_segment # 17 <= len <= 31 283SYM_FUNC_END(crc_t10dif_pcl) 284 285.section .rodata, "a", @progbits 286.align 16 287 288# Fold constants precomputed from the polynomial 0x18bb7 289# G(x) = x^16 + x^15 + x^11 + x^9 + x^8 + x^7 + x^5 + x^4 + x^2 + x^1 + x^0 290.Lfold_across_128_bytes_consts: 291 .quad 0x0000000000006123 # x^(8*128) mod G(x) 292 .quad 0x0000000000002295 # x^(8*128+64) mod G(x) 293.Lfold_across_64_bytes_consts: 294 .quad 0x0000000000001069 # x^(4*128) mod G(x) 295 .quad 0x000000000000dd31 # x^(4*128+64) mod G(x) 296.Lfold_across_32_bytes_consts: 297 .quad 0x000000000000857d # x^(2*128) mod G(x) 298 .quad 0x0000000000007acc # x^(2*128+64) mod G(x) 299.Lfold_across_16_bytes_consts: 300 .quad 0x000000000000a010 # x^(1*128) mod G(x) 301 .quad 0x0000000000001faa # x^(1*128+64) mod G(x) 302.Lfinal_fold_consts: 303 .quad 0x1368000000000000 # x^48 * (x^48 mod G(x)) 304 .quad 0x2d56000000000000 # x^48 * (x^80 mod G(x)) 305.Lbarrett_reduction_consts: 306 .quad 0x0000000000018bb7 # G(x) 307 .quad 0x00000001f65a57f8 # floor(x^48 / G(x)) 308 309.section .rodata.cst16.mask1, "aM", @progbits, 16 310.align 16 311.Lmask1: 312 .octa 0x80808080808080808080808080808080 313 314.section .rodata.cst16.mask2, "aM", @progbits, 16 315.align 16 316.Lmask2: 317 .octa 0x00000000FFFFFFFFFFFFFFFFFFFFFFFF 318 319.section .rodata.cst16.bswap_mask, "aM", @progbits, 16 320.align 16 321.Lbswap_mask: 322 .octa 0x000102030405060708090A0B0C0D0E0F 323 324.section .rodata.cst32.byteshift_table, "aM", @progbits, 32 325.align 16 326# For 1 <= len <= 15, the 16-byte vector beginning at &byteshift_table[16 - len] 327# is the index vector to shift left by 'len' bytes, and is also {0x80, ..., 328# 0x80} XOR the index vector to shift right by '16 - len' bytes. 329.Lbyteshift_table: 330 .byte 0x0, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87 331 .byte 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f 332 .byte 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7 333 .byte 0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe , 0x0 334