1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
/*
* 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/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
.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 %r14
.previous
|
