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/* 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
ENDPROC(crc32_be_vgfm_16)
.previous
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