/* 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 | |

.align 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 defintions: | |

* | |

* 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 righmost 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 | |

*/ | |

.Lconstants_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) | |

.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. | |

*/ | |

ENTRY(crc32_be_vgfm_16) | |

/* Load CRC-32 constants */ | |

larl %r5,.Lconstants_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 intermedate 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 | |

.previous |