1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  linux/arch/arm/lib/clear_user.S
4 *
5 *  Copyright (C) 1995, 1996,1997,1998 Russell King
6 */
7#include <linux/linkage.h>
8#include <asm/assembler.h>
9#include <asm/unwind.h>
10
11		.text
12
13/* Prototype: unsigned long arm_clear_user(void *addr, size_t sz)
14 * Purpose  : clear some user memory
15 * Params   : addr - user memory address to clear
16 *          : sz   - number of bytes to clear
17 * Returns  : number of bytes NOT cleared
18 */
19ENTRY(__clear_user_std)
20WEAK(arm_clear_user)
21UNWIND(.fnstart)
22UNWIND(.save {r1, lr})
23		stmfd	sp!, {r1, lr}
24		mov	r2, #0
25		cmp	r1, #4
26		blt	2f
27		ands	ip, r0, #3
28		beq	1f
29		cmp	ip, #2
30		strusr	r2, r0, 1
31		strusr	r2, r0, 1, le
32		strusr	r2, r0, 1, lt
33		rsb	ip, ip, #4
34		sub	r1, r1, ip		@  7  6  5  4  3  2  1
351:		subs	r1, r1, #8		@ -1 -2 -3 -4 -5 -6 -7
36		strusr	r2, r0, 4, pl, rept=2
37		bpl	1b
38		adds	r1, r1, #4		@  3  2  1  0 -1 -2 -3
39		strusr	r2, r0, 4, pl
402:		tst	r1, #2			@ 1x 1x 0x 0x 1x 1x 0x
41		strusr	r2, r0, 1, ne, rept=2
42		tst	r1, #1			@ x1 x0 x1 x0 x1 x0 x1
43		it	ne			@ explicit IT needed for the label
44USER(		strbtne	r2, [r0])
45		mov	r0, #0
46		ldmfd	sp!, {r1, pc}
47UNWIND(.fnend)
48ENDPROC(arm_clear_user)
49ENDPROC(__clear_user_std)
50
51		.pushsection .text.fixup,"ax"
52		.align	0
539001:		ldmfd	sp!, {r0, pc}
54		.popsection
55
56