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/vx-insn.h> 17 18/* Vector register range containing CRC-32 constants */ 19#define CONST_R1R2 %v9 20#define CONST_R3R4 %v10 21#define CONST_R5 %v11 22#define CONST_R6 %v12 23#define CONST_RU_POLY %v13 24#define CONST_CRC_POLY %v14 25 26.data 27.align 8 28 29/* 30 * The CRC-32 constant block contains reduction constants to fold and 31 * process particular chunks of the input data stream in parallel. 32 * 33 * For the CRC-32 variants, the constants are precomputed according to 34 * these defintions: 35 * 36 * R1 = x4*128+64 mod P(x) 37 * R2 = x4*128 mod P(x) 38 * R3 = x128+64 mod P(x) 39 * R4 = x128 mod P(x) 40 * R5 = x96 mod P(x) 41 * R6 = x64 mod P(x) 42 * 43 * Barret reduction constant, u, is defined as floor(x**64 / P(x)). 44 * 45 * where P(x) is the polynomial in the normal domain and the P'(x) is the 46 * polynomial in the reversed (bitreflected) domain. 47 * 48 * Note that the constant definitions below are extended in order to compute 49 * intermediate results with a single VECTOR GALOIS FIELD MULTIPLY instruction. 50 * The righmost doubleword can be 0 to prevent contribution to the result or 51 * can be multiplied by 1 to perform an XOR without the need for a separate 52 * VECTOR EXCLUSIVE OR instruction. 53 * 54 * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials: 55 * 56 * P(x) = 0x04C11DB7 57 * P'(x) = 0xEDB88320 58 */ 59 60.Lconstants_CRC_32_BE: 61 .quad 0x08833794c, 0x0e6228b11 # R1, R2 62 .quad 0x0c5b9cd4c, 0x0e8a45605 # R3, R4 63 .quad 0x0f200aa66, 1 << 32 # R5, x32 64 .quad 0x0490d678d, 1 # R6, 1 65 .quad 0x104d101df, 0 # u 66 .quad 0x104C11DB7, 0 # P(x) 67 68.previous 69 70.text 71/* 72 * The CRC-32 function(s) use these calling conventions: 73 * 74 * Parameters: 75 * 76 * %r2: Initial CRC value, typically ~0; and final CRC (return) value. 77 * %r3: Input buffer pointer, performance might be improved if the 78 * buffer is on a doubleword boundary. 79 * %r4: Length of the buffer, must be 64 bytes or greater. 80 * 81 * Register usage: 82 * 83 * %r5: CRC-32 constant pool base pointer. 84 * V0: Initial CRC value and intermediate constants and results. 85 * V1..V4: Data for CRC computation. 86 * V5..V8: Next data chunks that are fetched from the input buffer. 87 * 88 * V9..V14: CRC-32 constants. 89 */ 90ENTRY(crc32_be_vgfm_16) 91 /* Load CRC-32 constants */ 92 larl %r5,.Lconstants_CRC_32_BE 93 VLM CONST_R1R2,CONST_CRC_POLY,0,%r5 94 95 /* Load the initial CRC value into the leftmost word of V0. */ 96 VZERO %v0 97 VLVGF %v0,%r2,0 98 99 /* Load a 64-byte data chunk and XOR with CRC */ 100 VLM %v1,%v4,0,%r3 /* 64-bytes into V1..V4 */ 101 VX %v1,%v0,%v1 /* V1 ^= CRC */ 102 aghi %r3,64 /* BUF = BUF + 64 */ 103 aghi %r4,-64 /* LEN = LEN - 64 */ 104 105 /* Check remaining buffer size and jump to proper folding method */ 106 cghi %r4,64 107 jl .Lless_than_64bytes 108 109.Lfold_64bytes_loop: 110 /* Load the next 64-byte data chunk into V5 to V8 */ 111 VLM %v5,%v8,0,%r3 112 113 /* 114 * Perform a GF(2) multiplication of the doublewords in V1 with 115 * the reduction constants in V0. The intermediate result is 116 * then folded (accumulated) with the next data chunk in V5 and 117 * stored in V1. Repeat this step for the register contents 118 * in V2, V3, and V4 respectively. 119 */ 120 VGFMAG %v1,CONST_R1R2,%v1,%v5 121 VGFMAG %v2,CONST_R1R2,%v2,%v6 122 VGFMAG %v3,CONST_R1R2,%v3,%v7 123 VGFMAG %v4,CONST_R1R2,%v4,%v8 124 125 /* Adjust buffer pointer and length for next loop */ 126 aghi %r3,64 /* BUF = BUF + 64 */ 127 aghi %r4,-64 /* LEN = LEN - 64 */ 128 129 cghi %r4,64 130 jnl .Lfold_64bytes_loop 131 132.Lless_than_64bytes: 133 /* Fold V1 to V4 into a single 128-bit value in V1 */ 134 VGFMAG %v1,CONST_R3R4,%v1,%v2 135 VGFMAG %v1,CONST_R3R4,%v1,%v3 136 VGFMAG %v1,CONST_R3R4,%v1,%v4 137 138 /* Check whether to continue with 64-bit folding */ 139 cghi %r4,16 140 jl .Lfinal_fold 141 142.Lfold_16bytes_loop: 143 144 VL %v2,0,,%r3 /* Load next data chunk */ 145 VGFMAG %v1,CONST_R3R4,%v1,%v2 /* Fold next data chunk */ 146 147 /* Adjust buffer pointer and size for folding next data chunk */ 148 aghi %r3,16 149 aghi %r4,-16 150 151 /* Process remaining data chunks */ 152 cghi %r4,16 153 jnl .Lfold_16bytes_loop 154 155.Lfinal_fold: 156 /* 157 * The R5 constant is used to fold a 128-bit value into an 96-bit value 158 * that is XORed with the next 96-bit input data chunk. To use a single 159 * VGFMG instruction, multiply the rightmost 64-bit with x^32 (1<<32) to 160 * form an intermediate 96-bit value (with appended zeros) which is then 161 * XORed with the intermediate reduction result. 162 */ 163 VGFMG %v1,CONST_R5,%v1 164 165 /* 166 * Further reduce the remaining 96-bit value to a 64-bit value using a 167 * single VGFMG, the rightmost doubleword is multiplied with 0x1. The 168 * intermediate result is then XORed with the product of the leftmost 169 * doubleword with R6. The result is a 64-bit value and is subject to 170 * the Barret reduction. 171 */ 172 VGFMG %v1,CONST_R6,%v1 173 174 /* 175 * The input values to the Barret reduction are the degree-63 polynomial 176 * in V1 (R(x)), degree-32 generator polynomial, and the reduction 177 * constant u. The Barret reduction result is the CRC value of R(x) mod 178 * P(x). 179 * 180 * The Barret reduction algorithm is defined as: 181 * 182 * 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u 183 * 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x) 184 * 3. C(x) = R(x) XOR T2(x) mod x^32 185 * 186 * Note: To compensate the division by x^32, use the vector unpack 187 * instruction to move the leftmost word into the leftmost doubleword 188 * of the vector register. The rightmost doubleword is multiplied 189 * with zero to not contribute to the intermedate results. 190 */ 191 192 /* T1(x) = floor( R(x) / x^32 ) GF2MUL u */ 193 VUPLLF %v2,%v1 194 VGFMG %v2,CONST_RU_POLY,%v2 195 196 /* 197 * Compute the GF(2) product of the CRC polynomial in VO with T1(x) in 198 * V2 and XOR the intermediate result, T2(x), with the value in V1. 199 * The final result is in the rightmost word of V2. 200 */ 201 VUPLLF %v2,%v2 202 VGFMAG %v2,CONST_CRC_POLY,%v2,%v1 203 204.Ldone: 205 VLGVF %r2,%v2,3 206 br %r14 207 208.previous 209