1/*
2 * Based on arch/arm/lib/clear_user.S
3 *
4 * Copyright (C) 2012 ARM Ltd.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
17 */
18#include <linux/linkage.h>
19
20#include <asm/asm-uaccess.h>
21
22	.text
23
24/* Prototype: int __arch_clear_user(void *addr, size_t sz)
25 * Purpose  : clear some user memory
26 * Params   : addr - user memory address to clear
27 *          : sz   - number of bytes to clear
28 * Returns  : number of bytes NOT cleared
29 *
30 * Alignment fixed up by hardware.
31 */
32ENTRY(__arch_clear_user)
33	uaccess_enable_not_uao x2, x3, x4
34	mov	x2, x1			// save the size for fixup return
35	subs	x1, x1, #8
36	b.mi	2f
371:
38uao_user_alternative 9f, str, sttr, xzr, x0, 8
39	subs	x1, x1, #8
40	b.pl	1b
412:	adds	x1, x1, #4
42	b.mi	3f
43uao_user_alternative 9f, str, sttr, wzr, x0, 4
44	sub	x1, x1, #4
453:	adds	x1, x1, #2
46	b.mi	4f
47uao_user_alternative 9f, strh, sttrh, wzr, x0, 2
48	sub	x1, x1, #2
494:	adds	x1, x1, #1
50	b.mi	5f
51uao_user_alternative 9f, strb, sttrb, wzr, x0, 0
525:	mov	x0, #0
53	uaccess_disable_not_uao x2, x3
54	ret
55ENDPROC(__arch_clear_user)
56
57	.section .fixup,"ax"
58	.align	2
599:	mov	x0, x2			// return the original size
60	ret
61	.previous
62