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
208
209
210
211
212
213
214
215
216
217
218
|
/* strcpy -- copy a nul-terminated string.
Copyright (C) 2013-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* Endian independent macros for shifting bytes within registers. */
#ifdef __ARMEB__
#define lsh_gt lsr
#define lsh_ls lsl
#else
#define lsh_gt lsl
#define lsh_ls lsr
#endif
.syntax unified
.text
ENTRY (__stpcpy)
@ Signal stpcpy with NULL in IP.
mov ip, #0
b 0f
END (__stpcpy)
weak_alias (__stpcpy, stpcpy)
libc_hidden_def (__stpcpy)
libc_hidden_builtin_def (stpcpy)
ENTRY (strcpy)
@ Signal strcpy with DEST in IP.
mov ip, r0
0:
pld [r0, #0]
pld [r1, #0]
@ To cater to long strings, we want 8 byte alignment in the source.
@ To cater to small strings, we don't want to start that right away.
@ Loop up to 16 times, less whatever it takes to reach alignment.
and r3, r1, #7
rsb r3, r3, #16
@ Loop until we find ...
1: ldrb r2, [r1], #1
subs r3, r3, #1 @ ... the alignment point
strb r2, [r0], #1
it ne
cmpne r2, #0 @ ... or EOS
bne 1b
@ Disambiguate the exit possibilites above
cmp r2, #0 @ Found EOS
beq .Lreturn
@ Load the next two words asap
ldrd r2, r3, [r1], #8
pld [r0, #64]
pld [r1, #64]
@ For longer strings, we actaully need a stack frame.
push { r4, r5, r6, r7 }
cfi_adjust_cfa_offset (16)
cfi_rel_offset (r4, 0)
cfi_rel_offset (r5, 4)
cfi_rel_offset (r6, 8)
cfi_rel_offset (r7, 12)
@ Subtracting (unsigned saturating) from 1 for any byte means result
@ of 1 for any byte that was originally zero and 0 otherwise.
@ Therefore we consider the lsb of each byte the "found" bit.
#ifdef ARCH_HAS_T2
movw r7, #0x0101
tst r0, #3 @ Test alignment of DEST
movt r7, #0x0101
#else
ldr r7, =0x01010101
tst r0, #3
#endif
bne .Lunaligned
@ So now source (r1) is aligned to 8, and dest (r0) is aligned to 4.
@ Loop, reading 8 bytes at a time, searching for EOS.
.balign 16
2: uqsub8 r4, r7, r2 @ Find EOS
uqsub8 r5, r7, r3
pld [r1, #128]
cmp r4, #0 @ EOS in first word?
pld [r0, #128]
bne 3f
str r2, [r0], #4
cmp r5, #0 @ EOS in second word?
bne 4f
str r3, [r0], #4
ldrd r2, r3, [r1], #8
b 2b
3: sub r1, r1, #4 @ backup to first word
4: sub r1, r1, #4 @ backup to second word
@ ... then finish up any tail a byte at a time.
@ Note that we generally back up and re-read source bytes,
@ but we'll not re-write dest bytes.
.Lbyte_loop:
ldrb r2, [r1], #1
cmp r2, #0
strb r2, [r0], #1
bne .Lbyte_loop
pop { r4, r5, r6, r7 }
cfi_remember_state
cfi_adjust_cfa_offset (-16)
cfi_restore (r4)
cfi_restore (r5)
cfi_restore (r6)
cfi_restore (r7)
.Lreturn:
cmp ip, #0 @ Was this strcpy or stpcpy?
ite eq
subeq r0, r0, #1 @ stpcpy: undo post-inc from store
movne r0, ip @ strcpy: return original dest
bx lr
.Lunaligned:
cfi_restore_state
@ Here, source is aligned to 8, but the destination is not word
@ aligned. Therefore we have to shift the data in order to be
@ able to perform aligned word stores.
@ Find out which misalignment we're dealing with.
tst r0, #1
beq .Lunaligned2
tst r0, #2
bne .Lunaligned3
@ Fallthru to .Lunaligned1.
.macro unaligned_copy unalign
@ Prologue to unaligned loop. Seed shifted non-zero bytes.
uqsub8 r4, r7, r2 @ Find EOS
uqsub8 r5, r7, r3
cmp r4, #0 @ EOS in first word?
it ne
subne r1, r1, #8
bne .Lbyte_loop
#ifdef __ARMEB__
rev r2, r2 @ Byte stores below need LE data
#endif
@ Store a few bytes from the first word.
@ At the same time we align r0 and shift out bytes from r2.
.rept 4-\unalign
strb r2, [r0], #1
lsr r2, r2, #8
.endr
#ifdef __ARMEB__
rev r2, r2 @ Undo previous rev
#endif
@ Rotated unaligned copy loop. The tail of the prologue is
@ shared with the loop itself.
.balign 8
1: cmp r5, #0 @ EOS in second word?
bne 4f
@ Combine first and second words
orr r2, r2, r3, lsh_gt #(\unalign*8)
@ Save leftover bytes from the two words
lsh_ls r6, r3, #((4-\unalign)*8)
str r2, [r0], #4
@ The "real" start of the unaligned copy loop.
ldrd r2, r3, [r1], #8 @ Load 8 more bytes
uqsub8 r4, r7, r2 @ Find EOS
pld [r1, #128]
uqsub8 r5, r7, r3
pld [r0, #128]
cmp r4, #0 @ EOS in first word?
bne 3f
@ Combine the leftover and the first word
orr r6, r6, r2, lsh_gt #(\unalign*8)
@ Discard used bytes from the first word.
lsh_ls r2, r2, #((4-\unalign)*8)
str r6, [r0], #4
b 1b
@ Found EOS in one of the words; adjust backward
3: sub r1, r1, #4
mov r2, r6
4: sub r1, r1, #4
@ And store the remaining bytes from the leftover
#ifdef __ARMEB__
rev r2, r2
#endif
.rept \unalign
strb r2, [r0], #1
lsr r2, r2, #8
.endr
b .Lbyte_loop
.endm
.Lunaligned1:
unaligned_copy 1
.Lunaligned2:
unaligned_copy 2
.Lunaligned3:
unaligned_copy 3
END (strcpy)
libc_hidden_builtin_def (strcpy)
|
