-
Notifications
You must be signed in to change notification settings - Fork 2
/
memzero.S
137 lines (123 loc) · 2.52 KB
/
memzero.S
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
/*
* linux/arch/arm/lib/memzero.S
*
* Copyright (C) 1995-2000 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include "kernel_defines.h"
.text
.syntax unified
ARM( .p2align 5 )
THUMB( .p2align 2 )
ENTRY(__kernel_memzero)
ands r3, r0, #3
mov r2, #0
bne 7f
/*
* we know that the pointer in r0 is aligned to a word boundary.
*/
1: cmp r1, #8
blt 5f
mov r3, r2
cmp r1, #64
push {r4}
blt 4f
#if MEMSET_WRITE_ALIGN_BYTES > 0
ands r4, r0, #(MEMSET_WRITE_ALIGN_BYTES - 1)
/* Let r4 be equal to the number of bytes align. */
rsb r4, r4, #MEMSET_WRITE_ALIGN_BYTES
/*
* At this point r4 contains the number of bytes to align
* if eq is not set. The eq flag is set if there are no bytes
* to align.
*/
#if MEMSET_WRITE_ALIGN_BYTES == 8
subne r1, r1, r4
strne r2, [r0], #4
#elif MEMSET_WRITE_ALIGN_BYTES == 32
beq 2f
tst r4, #4
sub r1, r1, r4
strne r2, [r0], #4
tst r4, #8
stmiane r0!, {r2, r3}
cmp r4, #16
stmiage r0!, {r2, r3}
stmiage r0!, {r2, r3}
#endif
cmp r1, #64
blt 4f
#endif
2:
mov r4, r2
push {r5}
mov r5, r2
/* Copy 64 bytes in one iteration. */
3: stmia r0!, {r2, r3, r4, r5}
subs r1, r1, #64 /* Thumb16 */
stmia r0!, {r2, r3, r4, r5}
cmp r1, #64
stmia r0!, {r2, r3, r4, r5}
stmia r0!, {r2, r3, r4, r5}
bge 3b
pop {r5}
/* Early exit if there are 0 bytes left. */
THUMB( cbz r1, 9f )
ARM( teq r1, #0 )
ARM( beq 9f )
/* Handle 8-64 bytes. */
4: bic r4, r1, #7
subs r1, r1, r4
rsb r4, r4, #64
/* The stmia instruction is 32-bit for ARM, 16-bit for Thumb2. */
THUMB( lsrs r4, r4, #2 )
ARM( lsrs r4, r4, #1 )
add pc, pc, r4
nop
stmia r0!, {r2, r3}
stmia r0!, {r2, r3}
stmia r0!, {r2, r3}
stmia r0!, {r2, r3}
stmia r0!, {r2, r3}
stmia r0!, {r2, r3}
stmia r0!, {r2, r3}
stmia r0!, {r2, r3}
pop {r4}
5: cmp r1, #4
strge r2, [r0], #4
/* Early exit for multiple of 4 size. */
ands r1, r1, #3
BXEQLR
/*
* At this point there are 1, 2 or 3 bytes,
* and the destination is word aligned.
*/
6: cmp r1, #2
strhge r2, [r0], #2
strbne r2, [r0]
BXLR
/* Unaligned case; align the destination. */
7: cmp r1, #4
blt 8f
cmp r3, #2
sub r1, r1, #4
strble r2, [r0]
strble r2, [r0, #1]
addle r0, r0, #2
add r1, r1, r3
strbne r2, [r0], #1
b 1b
/* 0 to 3 bytes left. */
8: cmp r1, #2
strbge r2, [r0]
strbge r2, [r0, #1]
addge r0, r0, #2
tst r1, #1
strbne r2, [r0]
BXLR
9: pop {r4}
BXLR
ENDPROC(__kernel_memzero)