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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (C) 2013 ARM Ltd.
4 * Copyright (C) 2013 Linaro.
5 *
6 * This code is based on glibc cortex strings work originally authored by Linaro
7 * be found @
8 *
9 * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
10 * files/head:/src/aarch64/
11 */
12
13#include <linux/linkage.h>
14#include <asm/assembler.h>
15
16/*
17* compare memory areas(when two memory areas' offset are different,
18* alignment handled by the hardware)
19*
20* Parameters:
21* x0 - const memory area 1 pointer
22* x1 - const memory area 2 pointer
23* x2 - the maximal compare byte length
24* Returns:
25* x0 - a compare result, maybe less than, equal to, or greater than ZERO
26*/
27
28/* Parameters and result. */
29src1 .req x0
30src2 .req x1
31limit .req x2
32result .req x0
33
34/* Internal variables. */
35data1 .req x3
36data1w .req w3
37data2 .req x4
38data2w .req w4
39has_nul .req x5
40diff .req x6
41endloop .req x7
42tmp1 .req x8
43tmp2 .req x9
44tmp3 .req x10
45pos .req x11
46limit_wd .req x12
47mask .req x13
48
49SYM_FUNC_START_WEAK_PI(memcmp)
50 cbz limit, .Lret0
51 eor tmp1, src1, src2
52 tst tmp1, #7
53 b.ne .Lmisaligned8
54 ands tmp1, src1, #7
55 b.ne .Lmutual_align
56 sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
57 lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
58 /*
59 * The input source addresses are at alignment boundary.
60 * Directly compare eight bytes each time.
61 */
62.Lloop_aligned:
63 ldr data1, [src1], #8
64 ldr data2, [src2], #8
65.Lstart_realigned:
66 subs limit_wd, limit_wd, #1
67 eor diff, data1, data2 /* Non-zero if differences found. */
68 csinv endloop, diff, xzr, cs /* Last Dword or differences. */
69 cbz endloop, .Lloop_aligned
70
71 /* Not reached the limit, must have found a diff. */
72 tbz limit_wd, #63, .Lnot_limit
73
74 /* Limit % 8 == 0 => the diff is in the last 8 bytes. */
75 ands limit, limit, #7
76 b.eq .Lnot_limit
77 /*
78 * The remained bytes less than 8. It is needed to extract valid data
79 * from last eight bytes of the intended memory range.
80 */
81 lsl limit, limit, #3 /* bytes-> bits. */
82 mov mask, #~0
83CPU_BE( lsr mask, mask, limit )
84CPU_LE( lsl mask, mask, limit )
85 bic data1, data1, mask
86 bic data2, data2, mask
87
88 orr diff, diff, mask
89 b .Lnot_limit
90
91.Lmutual_align:
92 /*
93 * Sources are mutually aligned, but are not currently at an
94 * alignment boundary. Round down the addresses and then mask off
95 * the bytes that precede the start point.
96 */
97 bic src1, src1, #7
98 bic src2, src2, #7
99 ldr data1, [src1], #8
100 ldr data2, [src2], #8
101 /*
102 * We can not add limit with alignment offset(tmp1) here. Since the
103 * addition probably make the limit overflown.
104 */
105 sub limit_wd, limit, #1/*limit != 0, so no underflow.*/
106 and tmp3, limit_wd, #7
107 lsr limit_wd, limit_wd, #3
108 add tmp3, tmp3, tmp1
109 add limit_wd, limit_wd, tmp3, lsr #3
110 add limit, limit, tmp1/* Adjust the limit for the extra. */
111
112 lsl tmp1, tmp1, #3/* Bytes beyond alignment -> bits.*/
113 neg tmp1, tmp1/* Bits to alignment -64. */
114 mov tmp2, #~0
115 /*mask off the non-intended bytes before the start address.*/
116CPU_BE( lsl tmp2, tmp2, tmp1 )/*Big-endian.Early bytes are at MSB*/
117 /* Little-endian. Early bytes are at LSB. */
118CPU_LE( lsr tmp2, tmp2, tmp1 )
119
120 orr data1, data1, tmp2
121 orr data2, data2, tmp2
122 b .Lstart_realigned
123
124 /*src1 and src2 have different alignment offset.*/
125.Lmisaligned8:
126 cmp limit, #8
127 b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/
128
129 and tmp1, src1, #7
130 neg tmp1, tmp1
131 add tmp1, tmp1, #8/*valid length in the first 8 bytes of src1*/
132 and tmp2, src2, #7
133 neg tmp2, tmp2
134 add tmp2, tmp2, #8/*valid length in the first 8 bytes of src2*/
135 subs tmp3, tmp1, tmp2
136 csel pos, tmp1, tmp2, hi /*Choose the maximum.*/
137
138 sub limit, limit, pos
139 /*compare the proceeding bytes in the first 8 byte segment.*/
140.Ltinycmp:
141 ldrb data1w, [src1], #1
142 ldrb data2w, [src2], #1
143 subs pos, pos, #1
144 ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
145 b.eq .Ltinycmp
146 cbnz pos, 1f /*diff occurred before the last byte.*/
147 cmp data1w, data2w
148 b.eq .Lstart_align
1491:
150 sub result, data1, data2
151 ret
152
153.Lstart_align:
154 lsr limit_wd, limit, #3
155 cbz limit_wd, .Lremain8
156
157 ands xzr, src1, #7
158 b.eq .Lrecal_offset
159 /*process more leading bytes to make src1 aligned...*/
160 add src1, src1, tmp3 /*backwards src1 to alignment boundary*/
161 add src2, src2, tmp3
162 sub limit, limit, tmp3
163 lsr limit_wd, limit, #3
164 cbz limit_wd, .Lremain8
165 /*load 8 bytes from aligned SRC1..*/
166 ldr data1, [src1], #8
167 ldr data2, [src2], #8
168
169 subs limit_wd, limit_wd, #1
170 eor diff, data1, data2 /*Non-zero if differences found.*/
171 csinv endloop, diff, xzr, ne
172 cbnz endloop, .Lunequal_proc
173 /*How far is the current SRC2 from the alignment boundary...*/
174 and tmp3, tmp3, #7
175
176.Lrecal_offset:/*src1 is aligned now..*/
177 neg pos, tmp3
178.Lloopcmp_proc:
179 /*
180 * Divide the eight bytes into two parts. First,backwards the src2
181 * to an alignment boundary,load eight bytes and compare from
182 * the SRC2 alignment boundary. If all 8 bytes are equal,then start
183 * the second part's comparison. Otherwise finish the comparison.
184 * This special handle can garantee all the accesses are in the
185 * thread/task space in avoid to overrange access.
186 */
187 ldr data1, [src1,pos]
188 ldr data2, [src2,pos]
189 eor diff, data1, data2 /* Non-zero if differences found. */
190 cbnz diff, .Lnot_limit
191
192 /*The second part process*/
193 ldr data1, [src1], #8
194 ldr data2, [src2], #8
195 eor diff, data1, data2 /* Non-zero if differences found. */
196 subs limit_wd, limit_wd, #1
197 csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/
198 cbz endloop, .Lloopcmp_proc
199.Lunequal_proc:
200 cbz diff, .Lremain8
201
202/* There is difference occurred in the latest comparison. */
203.Lnot_limit:
204/*
205* For little endian,reverse the low significant equal bits into MSB,then
206* following CLZ can find how many equal bits exist.
207*/
208CPU_LE( rev diff, diff )
209CPU_LE( rev data1, data1 )
210CPU_LE( rev data2, data2 )
211
212 /*
213 * The MS-non-zero bit of DIFF marks either the first bit
214 * that is different, or the end of the significant data.
215 * Shifting left now will bring the critical information into the
216 * top bits.
217 */
218 clz pos, diff
219 lsl data1, data1, pos
220 lsl data2, data2, pos
221 /*
222 * We need to zero-extend (char is unsigned) the value and then
223 * perform a signed subtraction.
224 */
225 lsr data1, data1, #56
226 sub result, data1, data2, lsr #56
227 ret
228
229.Lremain8:
230 /* Limit % 8 == 0 =>. all data are equal.*/
231 ands limit, limit, #7
232 b.eq .Lret0
233
234.Ltiny8proc:
235 ldrb data1w, [src1], #1
236 ldrb data2w, [src2], #1
237 subs limit, limit, #1
238
239 ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
240 b.eq .Ltiny8proc
241 sub result, data1, data2
242 ret
243.Lret0:
244 mov result, #0
245 ret
246SYM_FUNC_END_PI(memcmp)
247EXPORT_SYMBOL_NOKASAN(memcmp)