1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Hardware-accelerated CRC-32 variants for Linux on z Systems
4 *
5 * Use the z/Architecture Vector Extension Facility to accelerate the
6 * computing of bitreflected CRC-32 checksums for IEEE 802.3 Ethernet
7 * and Castagnoli.
8 *
9 * This CRC-32 implementation algorithm is bitreflected and processes
10 * the least-significant bit first (Little-Endian).
11 *
12 * Copyright IBM Corp. 2015
13 * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
14 */
15
16 #include <linux/types.h>
17 #include <asm/fpu.h>
18 #include "crc32-vx.h"
19
20 /* Vector register range containing CRC-32 constants */
21 #define CONST_PERM_LE2BE 9
22 #define CONST_R2R1 10
23 #define CONST_R4R3 11
24 #define CONST_R5 12
25 #define CONST_RU_POLY 13
26 #define CONST_CRC_POLY 14
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 definitions:
34 *
35 * R1 = [(x4*128+32 mod P'(x) << 32)]' << 1
36 * R2 = [(x4*128-32 mod P'(x) << 32)]' << 1
37 * R3 = [(x128+32 mod P'(x) << 32)]' << 1
38 * R4 = [(x128-32 mod P'(x) << 32)]' << 1
39 * R5 = [(x64 mod P'(x) << 32)]' << 1
40 * R6 = [(x32 mod P'(x) << 32)]' << 1
41 *
42 * The bitreflected Barret reduction constant, u', is defined as
43 * the bit reversal of floor(x**64 / P(x)).
44 *
45 * where P(x) is the polynomial in the normal domain and the P'(x) is the
46 * polynomial in the reversed (bitreflected) domain.
47 *
48 * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials:
49 *
50 * P(x) = 0x04C11DB7
51 * P'(x) = 0xEDB88320
52 *
53 * CRC-32C (Castagnoli) polynomials:
54 *
55 * P(x) = 0x1EDC6F41
56 * P'(x) = 0x82F63B78
57 */
58
59 static unsigned long constants_CRC_32_LE[] = {
60 0x0f0e0d0c0b0a0908, 0x0706050403020100, /* BE->LE mask */
61 0x1c6e41596, 0x154442bd4, /* R2, R1 */
62 0x0ccaa009e, 0x1751997d0, /* R4, R3 */
63 0x0, 0x163cd6124, /* R5 */
64 0x0, 0x1f7011641, /* u' */
65 0x0, 0x1db710641 /* P'(x) << 1 */
66 };
67
68 static unsigned long constants_CRC_32C_LE[] = {
69 0x0f0e0d0c0b0a0908, 0x0706050403020100, /* BE->LE mask */
70 0x09e4addf8, 0x740eef02, /* R2, R1 */
71 0x14cd00bd6, 0xf20c0dfe, /* R4, R3 */
72 0x0, 0x0dd45aab8, /* R5 */
73 0x0, 0x0dea713f1, /* u' */
74 0x0, 0x105ec76f0 /* P'(x) << 1 */
75 };
76
77 /**
78 * crc32_le_vgfm_generic - Compute CRC-32 (LE variant) with vector registers
79 * @crc: Initial CRC value, typically ~0.
80 * @buf: Input buffer pointer, performance might be improved if the
81 * buffer is on a doubleword boundary.
82 * @size: Size of the buffer, must be 64 bytes or greater.
83 * @constants: CRC-32 constant pool base pointer.
84 *
85 * Register usage:
86 * V0: Initial CRC value and intermediate constants and results.
87 * V1..V4: Data for CRC computation.
88 * V5..V8: Next data chunks that are fetched from the input buffer.
89 * V9: Constant for BE->LE conversion and shift operations
90 * V10..V14: CRC-32 constants.
91 */
92 static u32 crc32_le_vgfm_generic(u32 crc, unsigned char const *buf, size_t size, unsigned long *constants)
93 {
94 /* Load CRC-32 constants */
95 fpu_vlm(CONST_PERM_LE2BE, CONST_CRC_POLY, constants);
96
97 /*
98 * Load the initial CRC value.
99 *
100 * The CRC value is loaded into the rightmost word of the
101 * vector register and is later XORed with the LSB portion
102 * of the loaded input data.
103 */
104 fpu_vzero(0); /* Clear V0 */
105 fpu_vlvgf(0, crc, 3); /* Load CRC into rightmost word */
106
107 /* Load a 64-byte data chunk and XOR with CRC */
108 fpu_vlm(1, 4, buf);
109 fpu_vperm(1, 1, 1, CONST_PERM_LE2BE);
110 fpu_vperm(2, 2, 2, CONST_PERM_LE2BE);
111 fpu_vperm(3, 3, 3, CONST_PERM_LE2BE);
112 fpu_vperm(4, 4, 4, CONST_PERM_LE2BE);
113
114 fpu_vx(1, 0, 1); /* V1 ^= CRC */
115 buf += 64;
116 size -= 64;
117
118 while (size >= 64) {
119 fpu_vlm(5, 8, buf);
120 fpu_vperm(5, 5, 5, CONST_PERM_LE2BE);
121 fpu_vperm(6, 6, 6, CONST_PERM_LE2BE);
122 fpu_vperm(7, 7, 7, CONST_PERM_LE2BE);
123 fpu_vperm(8, 8, 8, CONST_PERM_LE2BE);
124 /*
125 * Perform a GF(2) multiplication of the doublewords in V1 with
126 * the R1 and R2 reduction constants in V0. The intermediate
127 * result is then folded (accumulated) with the next data chunk
128 * in V5 and stored in V1. Repeat this step for the register
129 * contents in V2, V3, and V4 respectively.
130 */
131 fpu_vgfmag(1, CONST_R2R1, 1, 5);
132 fpu_vgfmag(2, CONST_R2R1, 2, 6);
133 fpu_vgfmag(3, CONST_R2R1, 3, 7);
134 fpu_vgfmag(4, CONST_R2R1, 4, 8);
135 buf += 64;
136 size -= 64;
137 }
138
139 /*
140 * Fold V1 to V4 into a single 128-bit value in V1. Multiply V1 with R3
141 * and R4 and accumulating the next 128-bit chunk until a single 128-bit
142 * value remains.
143 */
144 fpu_vgfmag(1, CONST_R4R3, 1, 2);
145 fpu_vgfmag(1, CONST_R4R3, 1, 3);
146 fpu_vgfmag(1, CONST_R4R3, 1, 4);
147
148 while (size >= 16) {
149 fpu_vl(2, buf);
150 fpu_vperm(2, 2, 2, CONST_PERM_LE2BE);
151 fpu_vgfmag(1, CONST_R4R3, 1, 2);
152 buf += 16;
153 size -= 16;
154 }
155
156 /*
157 * Set up a vector register for byte shifts. The shift value must
158 * be loaded in bits 1-4 in byte element 7 of a vector register.
159 * Shift by 8 bytes: 0x40
160 * Shift by 4 bytes: 0x20
161 */
162 fpu_vleib(9, 0x40, 7);
163
164 /*
165 * Prepare V0 for the next GF(2) multiplication: shift V0 by 8 bytes
166 * to move R4 into the rightmost doubleword and set the leftmost
167 * doubleword to 0x1.
168 */
169 fpu_vsrlb(0, CONST_R4R3, 9);
170 fpu_vleig(0, 1, 0);
171
172 /*
173 * Compute GF(2) product of V1 and V0. The rightmost doubleword
174 * of V1 is multiplied with R4. The leftmost doubleword of V1 is
175 * multiplied by 0x1 and is then XORed with rightmost product.
176 * Implicitly, the intermediate leftmost product becomes padded
177 */
178 fpu_vgfmg(1, 0, 1);
179
180 /*
181 * Now do the final 32-bit fold by multiplying the rightmost word
182 * in V1 with R5 and XOR the result with the remaining bits in V1.
183 *
184 * To achieve this by a single VGFMAG, right shift V1 by a word
185 * and store the result in V2 which is then accumulated. Use the
186 * vector unpack instruction to load the rightmost half of the
187 * doubleword into the rightmost doubleword element of V1; the other
188 * half is loaded in the leftmost doubleword.
189 * The vector register with CONST_R5 contains the R5 constant in the
190 * rightmost doubleword and the leftmost doubleword is zero to ignore
191 * the leftmost product of V1.
192 */
193 fpu_vleib(9, 0x20, 7); /* Shift by words */
194 fpu_vsrlb(2, 1, 9); /* Store remaining bits in V2 */
195 fpu_vupllf(1, 1); /* Split rightmost doubleword */
196 fpu_vgfmag(1, CONST_R5, 1, 2); /* V1 = (V1 * R5) XOR V2 */
197
198 /*
199 * Apply a Barret reduction to compute the final 32-bit CRC value.
200 *
201 * The input values to the Barret reduction are the degree-63 polynomial
202 * in V1 (R(x)), degree-32 generator polynomial, and the reduction
203 * constant u. The Barret reduction result is the CRC value of R(x) mod
204 * P(x).
205 *
206 * The Barret reduction algorithm is defined as:
207 *
208 * 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u
209 * 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x)
210 * 3. C(x) = R(x) XOR T2(x) mod x^32
211 *
212 * Note: The leftmost doubleword of vector register containing
213 * CONST_RU_POLY is zero and, thus, the intermediate GF(2) product
214 * is zero and does not contribute to the final result.
215 */
216
217 /* T1(x) = floor( R(x) / x^32 ) GF2MUL u */
218 fpu_vupllf(2, 1);
219 fpu_vgfmg(2, CONST_RU_POLY, 2);
220
221 /*
222 * Compute the GF(2) product of the CRC polynomial with T1(x) in
223 * V2 and XOR the intermediate result, T2(x), with the value in V1.
224 * The final result is stored in word element 2 of V2.
225 */
226 fpu_vupllf(2, 2);
227 fpu_vgfmag(2, CONST_CRC_POLY, 2, 1);
228
229 return fpu_vlgvf(2, 2);
230 }
231
232 u32 crc32_le_vgfm_16(u32 crc, unsigned char const *buf, size_t size)
233 {
234 return crc32_le_vgfm_generic(crc, buf, size, &constants_CRC_32_LE[0]);
235 }
236
237 u32 crc32c_le_vgfm_16(u32 crc, unsigned char const *buf, size_t size)
238 {
239 return crc32_le_vgfm_generic(crc, buf, size, &constants_CRC_32C_LE[0]);
240 }
241
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