1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Copyright (C) 2021 Arm Ltd.
4 */
5
6 #include <linux/linkage.h>
7 #include <asm/asm-uaccess.h>
8
9 .text
10
11 /* Prototype: int __arch_clear_user(void *addr
12 * Purpose : clear some user memory
13 * Params : addr - user memory address to cl
14 * : sz - number of bytes to clear
15 * Returns : number of bytes NOT cleared
16 *
17 * Alignment fixed up by hardware.
18 */
19
20 .p2align 4
21 // Alignment is for the loop, but sinc
22 // is also 16 bytes we can keep any pa
23 SYM_FUNC_START(__arch_clear_user)
24 add x2, x0, x1
25 subs x1, x1, #8
26 b.mi 2f
27 1:
28 USER(9f, sttr xzr, [x0])
29 add x0, x0, #8
30 subs x1, x1, #8
31 b.hi 1b
32 USER(9f, sttr xzr, [x2, #-8])
33 mov x0, #0
34 ret
35
36 2: tbz x1, #2, 3f
37 USER(9f, sttr wzr, [x0])
38 USER(8f, sttr wzr, [x2, #-4])
39 mov x0, #0
40 ret
41
42 3: tbz x1, #1, 4f
43 USER(9f, sttrh wzr, [x0])
44 4: tbz x1, #0, 5f
45 USER(7f, sttrb wzr, [x2, #-1])
46 5: mov x0, #0
47 ret
48
49 // Exception fixups
50 7: sub x0, x2, #5 // Adjust for
51 8: add x0, x0, #4 // ...or the s
52 9: sub x0, x2, x0
53 ret
54 SYM_FUNC_END(__arch_clear_user)
55 EXPORT_SYMBOL(__arch_clear_user)
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