1/* 2 * Hardware-accelerated CRC-32 variants for Linux on z Systems 3 * 4 * Use the z/Architecture Vector Extension Facility to accelerate the 5 * computing of CRC-32 checksums. 6 * 7 * This CRC-32 implementation algorithm processes the most-significant 8 * bit first (BE). 9 * 10 * Copyright IBM Corp. 2015 11 * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com> 12 */ 13 14#include <linux/linkage.h> 15#include <asm/vx-insn.h> 16 17/* Vector register range containing CRC-32 constants */ 18#define CONST_R1R2 %v9 19#define CONST_R3R4 %v10 20#define CONST_R5 %v11 21#define CONST_R6 %v12 22#define CONST_RU_POLY %v13 23#define CONST_CRC_POLY %v14 24 25.data 26.align 8 27 28/* 29 * The CRC-32 constant block contains reduction constants to fold and 30 * process particular chunks of the input data stream in parallel. 31 * 32 * For the CRC-32 variants, the constants are precomputed according to 33 * these defintions: 34 * 35 * R1 = x4*128+64 mod P(x) 36 * R2 = x4*128 mod P(x) 37 * R3 = x128+64 mod P(x) 38 * R4 = x128 mod P(x) 39 * R5 = x96 mod P(x) 40 * R6 = x64 mod P(x) 41 * 42 * Barret reduction constant, u, is defined as floor(x**64 / P(x)). 43 * 44 * where P(x) is the polynomial in the normal domain and the P'(x) is the 45 * polynomial in the reversed (bitreflected) domain. 46 * 47 * Note that the constant definitions below are extended in order to compute 48 * intermediate results with a single VECTOR GALOIS FIELD MULTIPLY instruction. 49 * The righmost doubleword can be 0 to prevent contribution to the result or 50 * can be multiplied by 1 to perform an XOR without the need for a separate 51 * VECTOR EXCLUSIVE OR instruction. 52 * 53 * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials: 54 * 55 * P(x) = 0x04C11DB7 56 * P'(x) = 0xEDB88320 57 */ 58 59.Lconstants_CRC_32_BE: 60 .quad 0x08833794c, 0x0e6228b11 # R1, R2 61 .quad 0x0c5b9cd4c, 0x0e8a45605 # R3, R4 62 .quad 0x0f200aa66, 1 << 32 # R5, x32 63 .quad 0x0490d678d, 1 # R6, 1 64 .quad 0x104d101df, 0 # u 65 .quad 0x104C11DB7, 0 # P(x) 66 67.previous 68 69.text 70/* 71 * The CRC-32 function(s) use these calling conventions: 72 * 73 * Parameters: 74 * 75 * %r2: Initial CRC value, typically ~0; and final CRC (return) value. 76 * %r3: Input buffer pointer, performance might be improved if the 77 * buffer is on a doubleword boundary. 78 * %r4: Length of the buffer, must be 64 bytes or greater. 79 * 80 * Register usage: 81 * 82 * %r5: CRC-32 constant pool base pointer. 83 * V0: Initial CRC value and intermediate constants and results. 84 * V1..V4: Data for CRC computation. 85 * V5..V8: Next data chunks that are fetched from the input buffer. 86 * 87 * V9..V14: CRC-32 constants. 88 */ 89ENTRY(crc32_be_vgfm_16) 90 /* Load CRC-32 constants */ 91 larl %r5,.Lconstants_CRC_32_BE 92 VLM CONST_R1R2,CONST_CRC_POLY,0,%r5 93 94 /* Load the initial CRC value into the leftmost word of V0. */ 95 VZERO %v0 96 VLVGF %v0,%r2,0 97 98 /* Load a 64-byte data chunk and XOR with CRC */ 99 VLM %v1,%v4,0,%r3 /* 64-bytes into V1..V4 */ 100 VX %v1,%v0,%v1 /* V1 ^= CRC */ 101 aghi %r3,64 /* BUF = BUF + 64 */ 102 aghi %r4,-64 /* LEN = LEN - 64 */ 103 104 /* Check remaining buffer size and jump to proper folding method */ 105 cghi %r4,64 106 jl .Lless_than_64bytes 107 108.Lfold_64bytes_loop: 109 /* Load the next 64-byte data chunk into V5 to V8 */ 110 VLM %v5,%v8,0,%r3 111 112 /* 113 * Perform a GF(2) multiplication of the doublewords in V1 with 114 * the reduction constants in V0. The intermediate result is 115 * then folded (accumulated) with the next data chunk in V5 and 116 * stored in V1. Repeat this step for the register contents 117 * in V2, V3, and V4 respectively. 118 */ 119 VGFMAG %v1,CONST_R1R2,%v1,%v5 120 VGFMAG %v2,CONST_R1R2,%v2,%v6 121 VGFMAG %v3,CONST_R1R2,%v3,%v7 122 VGFMAG %v4,CONST_R1R2,%v4,%v8 123 124 /* Adjust buffer pointer and length for next loop */ 125 aghi %r3,64 /* BUF = BUF + 64 */ 126 aghi %r4,-64 /* LEN = LEN - 64 */ 127 128 cghi %r4,64 129 jnl .Lfold_64bytes_loop 130 131.Lless_than_64bytes: 132 /* Fold V1 to V4 into a single 128-bit value in V1 */ 133 VGFMAG %v1,CONST_R3R4,%v1,%v2 134 VGFMAG %v1,CONST_R3R4,%v1,%v3 135 VGFMAG %v1,CONST_R3R4,%v1,%v4 136 137 /* Check whether to continue with 64-bit folding */ 138 cghi %r4,16 139 jl .Lfinal_fold 140 141.Lfold_16bytes_loop: 142 143 VL %v2,0,,%r3 /* Load next data chunk */ 144 VGFMAG %v1,CONST_R3R4,%v1,%v2 /* Fold next data chunk */ 145 146 /* Adjust buffer pointer and size for folding next data chunk */ 147 aghi %r3,16 148 aghi %r4,-16 149 150 /* Process remaining data chunks */ 151 cghi %r4,16 152 jnl .Lfold_16bytes_loop 153 154.Lfinal_fold: 155 /* 156 * The R5 constant is used to fold a 128-bit value into an 96-bit value 157 * that is XORed with the next 96-bit input data chunk. To use a single 158 * VGFMG instruction, multiply the rightmost 64-bit with x^32 (1<<32) to 159 * form an intermediate 96-bit value (with appended zeros) which is then 160 * XORed with the intermediate reduction result. 161 */ 162 VGFMG %v1,CONST_R5,%v1 163 164 /* 165 * Further reduce the remaining 96-bit value to a 64-bit value using a 166 * single VGFMG, the rightmost doubleword is multiplied with 0x1. The 167 * intermediate result is then XORed with the product of the leftmost 168 * doubleword with R6. The result is a 64-bit value and is subject to 169 * the Barret reduction. 170 */ 171 VGFMG %v1,CONST_R6,%v1 172 173 /* 174 * The input values to the Barret reduction are the degree-63 polynomial 175 * in V1 (R(x)), degree-32 generator polynomial, and the reduction 176 * constant u. The Barret reduction result is the CRC value of R(x) mod 177 * P(x). 178 * 179 * The Barret reduction algorithm is defined as: 180 * 181 * 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u 182 * 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x) 183 * 3. C(x) = R(x) XOR T2(x) mod x^32 184 * 185 * Note: To compensate the division by x^32, use the vector unpack 186 * instruction to move the leftmost word into the leftmost doubleword 187 * of the vector register. The rightmost doubleword is multiplied 188 * with zero to not contribute to the intermedate results. 189 */ 190 191 /* T1(x) = floor( R(x) / x^32 ) GF2MUL u */ 192 VUPLLF %v2,%v1 193 VGFMG %v2,CONST_RU_POLY,%v2 194 195 /* 196 * Compute the GF(2) product of the CRC polynomial in VO with T1(x) in 197 * V2 and XOR the intermediate result, T2(x), with the value in V1. 198 * The final result is in the rightmost word of V2. 199 */ 200 VUPLLF %v2,%v2 201 VGFMAG %v2,CONST_CRC_POLY,%v2,%v1 202 203.Ldone: 204 VLGVF %r2,%v2,3 205 br %r14 206 207.previous 208