s390/crypto/crc32be-vx.S

1 /* SPDX-License-Identifier: GPL-2.0 */
3  * Hardware-accelerated CRC-32 variants for Linux on z Systems
6  * computing of CRC-32 checksums.
8  * This CRC-32 implementation algorithm processes the most-significant
9  * bit first (BE).
16 #include <asm/nospec-insn.h>
17 #include <asm/vx-insn.h>
19 /* Vector register range containing CRC-32 constants */
31  * The CRC-32 constant block contains reduction constants to fold and
34  * For the CRC-32 variants, the constants are precomputed according to
37  *	R1 = x4*128+64 mod P(x)
39  *	R3 = x128+64   mod P(x)
44  *	Barret reduction constant, u, is defined as floor(x**64 / P(x)).
55  * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials:
76  * The CRC-32 function(s) use these calling conventions:
83  *	%r4:	Length of the buffer, must be 64 bytes or greater.
87  *	%r5:	CRC-32 constant pool base pointer.
92  *	V9..V14: CRC-32 constants.
95 	/* Load CRC-32 constants */
103 	/* Load a 64-byte data chunk and XOR with CRC */
104 	VLM	%v1,%v4,0,%r3		/* 64-bytes into V1..V4 */
106 	aghi	%r3,64			/* BUF = BUF + 64 */
107 	aghi	%r4,-64			/* LEN = LEN - 64 */
110 	cghi	%r4,64
114 	/* Load the next 64-byte data chunk into V5 to V8 */
130 	aghi	%r3,64			/* BUF = BUF + 64 */
131 	aghi	%r4,-64			/* LEN = LEN - 64 */
133 	cghi	%r4,64
137 	/* Fold V1 to V4 into a single 128-bit value in V1 */
142 	/* Check whether to continue with 64-bit folding */
153 	aghi	%r4,-16
161 	 * The R5 constant is used to fold a 128-bit value into an 96-bit value
162 	 * that is XORed with the next 96-bit input data chunk.  To use a single
163 	 * VGFMG instruction, multiply the rightmost 64-bit with x^32 (1<<32) to
164 	 * form an intermediate 96-bit value (with appended zeros) which is then
170 	 * Further reduce the remaining 96-bit value to a 64-bit value using a
173 	 * doubleword with R6.	The result is a 64-bit value and is subject to
179 	 * The input values to the Barret reduction are the degree-63 polynomial
180 	 * in V1 (R(x)), degree-32 generator polynomial, and the reduction