1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Hardware-accelerated CRC-32 variants for Linux on z Systems 4 * 5 * Use the z/Architecture Vector Extension Facility to accelerate the 6 * computing of CRC-32 checksums. 7 * 8 * This CRC-32 implementation algorithm processes the most-significant 9 * bit first (BE). 10 * 11 * Copyright IBM Corp. 2015 12 * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com> 13 */ 14 15 #include <linux/linkage.h> 16 #include <asm/nospec-insn.h> 17 #include <asm/vx-insn.h> 18 19 /* Vector register range containing CRC-32 constants */ 20 #define CONST_R1R2 %v9 21 #define CONST_R3R4 %v10 22 #define CONST_R5 %v11 23 #define CONST_R6 %v12 24 #define CONST_RU_POLY %v13 25 #define CONST_CRC_POLY %v14 26 27 .data 28 .balign 8 29 30 /* 31 * The CRC-32 constant block contains reduction constants to fold and 32 * process particular chunks of the input data stream in parallel. 33 * 34 * For the CRC-32 variants, the constants are precomputed according to 35 * these definitions: 36 * 37 * R1 = x4*128+64 mod P(x) 38 * R2 = x4*128 mod P(x) 39 * R3 = x128+64 mod P(x) 40 * R4 = x128 mod P(x) 41 * R5 = x96 mod P(x) 42 * R6 = x64 mod P(x) 43 * 44 * Barret reduction constant, u, is defined as floor(x**64 / P(x)). 45 * 46 * where P(x) is the polynomial in the normal domain and the P'(x) is the 47 * polynomial in the reversed (bitreflected) domain. 48 * 49 * Note that the constant definitions below are extended in order to compute 50 * intermediate results with a single VECTOR GALOIS FIELD MULTIPLY instruction. 51 * The rightmost doubleword can be 0 to prevent contribution to the result or 52 * can be multiplied by 1 to perform an XOR without the need for a separate 53 * VECTOR EXCLUSIVE OR instruction. 54 * 55 * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials: 56 * 57 * P(x) = 0x04C11DB7 58 * P'(x) = 0xEDB88320 59 */ 60 61 SYM_DATA_START_LOCAL(constants_CRC_32_BE) 62 .quad 0x08833794c, 0x0e6228b11 # R1, R2 63 .quad 0x0c5b9cd4c, 0x0e8a45605 # R3, R4 64 .quad 0x0f200aa66, 1 << 32 # R5, x32 65 .quad 0x0490d678d, 1 # R6, 1 66 .quad 0x104d101df, 0 # u 67 .quad 0x104C11DB7, 0 # P(x) 68 SYM_DATA_END(constants_CRC_32_BE) 69 70 .previous 71 72 GEN_BR_THUNK %r14 73 74 .text 75 /* 76 * The CRC-32 function(s) use these calling conventions: 77 * 78 * Parameters: 79 * 80 * %r2: Initial CRC value, typically ~0; and final CRC (return) value. 81 * %r3: Input buffer pointer, performance might be improved if the 82 * buffer is on a doubleword boundary. 83 * %r4: Length of the buffer, must be 64 bytes or greater. 84 * 85 * Register usage: 86 * 87 * %r5: CRC-32 constant pool base pointer. 88 * V0: Initial CRC value and intermediate constants and results. 89 * V1..V4: Data for CRC computation. 90 * V5..V8: Next data chunks that are fetched from the input buffer. 91 * 92 * V9..V14: CRC-32 constants. 93 */ 94 SYM_FUNC_START(crc32_be_vgfm_16) 95 /* Load CRC-32 constants */ 96 larl %r5,constants_CRC_32_BE 97 VLM CONST_R1R2,CONST_CRC_POLY,0,%r5 98 99 /* Load the initial CRC value into the leftmost word of V0. */ 100 VZERO %v0 101 VLVGF %v0,%r2,0 102 103 /* Load a 64-byte data chunk and XOR with CRC */ 104 VLM %v1,%v4,0,%r3 /* 64-bytes into V1..V4 */ 105 VX %v1,%v0,%v1 /* V1 ^= CRC */ 106 aghi %r3,64 /* BUF = BUF + 64 */ 107 aghi %r4,-64 /* LEN = LEN - 64 */ 108 109 /* Check remaining buffer size and jump to proper folding method */ 110 cghi %r4,64 111 jl .Lless_than_64bytes 112 113 .Lfold_64bytes_loop: 114 /* Load the next 64-byte data chunk into V5 to V8 */ 115 VLM %v5,%v8,0,%r3 116 117 /* 118 * Perform a GF(2) multiplication of the doublewords in V1 with 119 * the reduction constants in V0. The intermediate result is 120 * then folded (accumulated) with the next data chunk in V5 and 121 * stored in V1. Repeat this step for the register contents 122 * in V2, V3, and V4 respectively. 123 */ 124 VGFMAG %v1,CONST_R1R2,%v1,%v5 125 VGFMAG %v2,CONST_R1R2,%v2,%v6 126 VGFMAG %v3,CONST_R1R2,%v3,%v7 127 VGFMAG %v4,CONST_R1R2,%v4,%v8 128 129 /* Adjust buffer pointer and length for next loop */ 130 aghi %r3,64 /* BUF = BUF + 64 */ 131 aghi %r4,-64 /* LEN = LEN - 64 */ 132 133 cghi %r4,64 134 jnl .Lfold_64bytes_loop 135 136 .Lless_than_64bytes: 137 /* Fold V1 to V4 into a single 128-bit value in V1 */ 138 VGFMAG %v1,CONST_R3R4,%v1,%v2 139 VGFMAG %v1,CONST_R3R4,%v1,%v3 140 VGFMAG %v1,CONST_R3R4,%v1,%v4 141 142 /* Check whether to continue with 64-bit folding */ 143 cghi %r4,16 144 jl .Lfinal_fold 145 146 .Lfold_16bytes_loop: 147 148 VL %v2,0,,%r3 /* Load next data chunk */ 149 VGFMAG %v1,CONST_R3R4,%v1,%v2 /* Fold next data chunk */ 150 151 /* Adjust buffer pointer and size for folding next data chunk */ 152 aghi %r3,16 153 aghi %r4,-16 154 155 /* Process remaining data chunks */ 156 cghi %r4,16 157 jnl .Lfold_16bytes_loop 158 159 .Lfinal_fold: 160 /* 161 * The R5 constant is used to fold a 128-bit value into an 96-bit value 162 * that is XORed with the next 96-bit input data chunk. To use a single 163 * VGFMG instruction, multiply the rightmost 64-bit with x^32 (1<<32) to 164 * form an intermediate 96-bit value (with appended zeros) which is then 165 * XORed with the intermediate reduction result. 166 */ 167 VGFMG %v1,CONST_R5,%v1 168 169 /* 170 * Further reduce the remaining 96-bit value to a 64-bit value using a 171 * single VGFMG, the rightmost doubleword is multiplied with 0x1. The 172 * intermediate result is then XORed with the product of the leftmost 173 * doubleword with R6. The result is a 64-bit value and is subject to 174 * the Barret reduction. 175 */ 176 VGFMG %v1,CONST_R6,%v1 177 178 /* 179 * The input values to the Barret reduction are the degree-63 polynomial 180 * in V1 (R(x)), degree-32 generator polynomial, and the reduction 181 * constant u. The Barret reduction result is the CRC value of R(x) mod 182 * P(x). 183 * 184 * The Barret reduction algorithm is defined as: 185 * 186 * 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u 187 * 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x) 188 * 3. C(x) = R(x) XOR T2(x) mod x^32 189 * 190 * Note: To compensate the division by x^32, use the vector unpack 191 * instruction to move the leftmost word into the leftmost doubleword 192 * of the vector register. The rightmost doubleword is multiplied 193 * with zero to not contribute to the intermediate results. 194 */ 195 196 /* T1(x) = floor( R(x) / x^32 ) GF2MUL u */ 197 VUPLLF %v2,%v1 198 VGFMG %v2,CONST_RU_POLY,%v2 199 200 /* 201 * Compute the GF(2) product of the CRC polynomial in VO with T1(x) in 202 * V2 and XOR the intermediate result, T2(x), with the value in V1. 203 * The final result is in the rightmost word of V2. 204 */ 205 VUPLLF %v2,%v2 206 VGFMAG %v2,CONST_CRC_POLY,%v2,%v1 207 208 .Ldone: 209 VLGVF %r2,%v2,3 210 BR_EX %r14 211 SYM_FUNC_END(crc32_be_vgfm_16) 212 213 .previous 214