/* SPDX-License-Identifier: GPL-2.0 */ /* * Hardware-accelerated CRC-32 variants for Linux on z Systems * * Use the z/Architecture Vector Extension Facility to accelerate the * computing of CRC-32 checksums. * * This CRC-32 implementation algorithm processes the most-significant * bit first (BE). * * Copyright IBM Corp. 2015 * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com> */ #include <linux/linkage.h> #include <asm/nospec-insn.h> #include <asm/vx-insn.h> /* Vector register range containing CRC-32 constants */ #define CONST_R1R2 %v9 #define CONST_R3R4 %v10 #define CONST_R5 %v11 #define CONST_R6 %v12 #define CONST_RU_POLY %v13 #define CONST_CRC_POLY %v14 .data .balign 8 /* * The CRC-32 constant block contains reduction constants to fold and * process particular chunks of the input data stream in parallel. * * For the CRC-32 variants, the constants are precomputed according to * these definitions: * * R1 = x4*128+64 mod P(x) * R2 = x4*128 mod P(x) * R3 = x128+64 mod P(x) * R4 = x128 mod P(x) * R5 = x96 mod P(x) * R6 = x64 mod P(x) * * Barret reduction constant, u, is defined as floor(x**64 / P(x)). * * where P(x) is the polynomial in the normal domain and the P'(x) is the * polynomial in the reversed (bitreflected) domain. * * Note that the constant definitions below are extended in order to compute * intermediate results with a single VECTOR GALOIS FIELD MULTIPLY instruction. * The rightmost doubleword can be 0 to prevent contribution to the result or * can be multiplied by 1 to perform an XOR without the need for a separate * VECTOR EXCLUSIVE OR instruction. * * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials: * * P(x) = 0x04C11DB7 * P'(x) = 0xEDB88320 */ SYM_DATA_START_LOCAL(constants_CRC_32_BE) .quad 0x08833794c, 0x0e6228b11 # R1, R2 .quad 0x0c5b9cd4c, 0x0e8a45605 # R3, R4 .quad 0x0f200aa66, 1 << 32 # R5, x32 .quad 0x0490d678d, 1 # R6, 1 .quad 0x104d101df, 0 # u .quad 0x104C11DB7, 0 # P(x) SYM_DATA_END(constants_CRC_32_BE) .previous GEN_BR_THUNK %r14 .text /* * The CRC-32 function(s) use these calling conventions: * * Parameters: * * %r2: Initial CRC value, typically ~0; and final CRC (return) value. * %r3: Input buffer pointer, performance might be improved if the * buffer is on a doubleword boundary. * %r4: Length of the buffer, must be 64 bytes or greater. * * Register usage: * * %r5: CRC-32 constant pool base pointer. * V0: Initial CRC value and intermediate constants and results. * V1..V4: Data for CRC computation. * V5..V8: Next data chunks that are fetched from the input buffer. * * V9..V14: CRC-32 constants. */ SYM_FUNC_START(crc32_be_vgfm_16) /* Load CRC-32 constants */ larl %r5,constants_CRC_32_BE VLM CONST_R1R2,CONST_CRC_POLY,0,%r5 /* Load the initial CRC value into the leftmost word of V0. */ VZERO %v0 VLVGF %v0,%r2,0 /* Load a 64-byte data chunk and XOR with CRC */ VLM %v1,%v4,0,%r3 /* 64-bytes into V1..V4 */ VX %v1,%v0,%v1 /* V1 ^= CRC */ aghi %r3,64 /* BUF = BUF + 64 */ aghi %r4,-64 /* LEN = LEN - 64 */ /* Check remaining buffer size and jump to proper folding method */ cghi %r4,64 jl .Lless_than_64bytes .Lfold_64bytes_loop: /* Load the next 64-byte data chunk into V5 to V8 */ VLM %v5,%v8,0,%r3 /* * Perform a GF(2) multiplication of the doublewords in V1 with * the reduction constants in V0. The intermediate result is * then folded (accumulated) with the next data chunk in V5 and * stored in V1. Repeat this step for the register contents * in V2, V3, and V4 respectively. */ VGFMAG %v1,CONST_R1R2,%v1,%v5 VGFMAG %v2,CONST_R1R2,%v2,%v6 VGFMAG %v3,CONST_R1R2,%v3,%v7 VGFMAG %v4,CONST_R1R2,%v4,%v8 /* Adjust buffer pointer and length for next loop */ aghi %r3,64 /* BUF = BUF + 64 */ aghi %r4,-64 /* LEN = LEN - 64 */ cghi %r4,64 jnl .Lfold_64bytes_loop .Lless_than_64bytes: /* Fold V1 to V4 into a single 128-bit value in V1 */ VGFMAG %v1,CONST_R3R4,%v1,%v2 VGFMAG %v1,CONST_R3R4,%v1,%v3 VGFMAG %v1,CONST_R3R4,%v1,%v4 /* Check whether to continue with 64-bit folding */ cghi %r4,16 jl .Lfinal_fold .Lfold_16bytes_loop: VL %v2,0,,%r3 /* Load next data chunk */ VGFMAG %v1,CONST_R3R4,%v1,%v2 /* Fold next data chunk */ /* Adjust buffer pointer and size for folding next data chunk */ aghi %r3,16 aghi %r4,-16 /* Process remaining data chunks */ cghi %r4,16 jnl .Lfold_16bytes_loop .Lfinal_fold: /* * The R5 constant is used to fold a 128-bit value into an 96-bit value * that is XORed with the next 96-bit input data chunk. To use a single * VGFMG instruction, multiply the rightmost 64-bit with x^32 (1<<32) to * form an intermediate 96-bit value (with appended zeros) which is then * XORed with the intermediate reduction result. */ VGFMG %v1,CONST_R5,%v1 /* * Further reduce the remaining 96-bit value to a 64-bit value using a * single VGFMG, the rightmost doubleword is multiplied with 0x1. The * intermediate result is then XORed with the product of the leftmost * doubleword with R6. The result is a 64-bit value and is subject to * the Barret reduction. */ VGFMG %v1,CONST_R6,%v1 /* * The input values to the Barret reduction are the degree-63 polynomial * in V1 (R(x)), degree-32 generator polynomial, and the reduction * constant u. The Barret reduction result is the CRC value of R(x) mod * P(x). * * The Barret reduction algorithm is defined as: * * 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u * 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x) * 3. C(x) = R(x) XOR T2(x) mod x^32 * * Note: To compensate the division by x^32, use the vector unpack * instruction to move the leftmost word into the leftmost doubleword * of the vector register. The rightmost doubleword is multiplied * with zero to not contribute to the intermediate results. */ /* T1(x) = floor( R(x) / x^32 ) GF2MUL u */ VUPLLF %v2,%v1 VGFMG %v2,CONST_RU_POLY,%v2 /* * Compute the GF(2) product of the CRC polynomial in VO with T1(x) in * V2 and XOR the intermediate result, T2(x), with the value in V1. * The final result is in the rightmost word of V2. */ VUPLLF %v2,%v2 VGFMAG %v2,CONST_CRC_POLY,%v2,%v1 .Ldone: VLGVF %r2,%v2,3 BR_EX %r14 SYM_FUNC_END(crc32_be_vgfm_16) .previous