1/*
2 *  linux/arch/arm/lib/clear_user.S
3 *
4 *  Copyright (C) 1995, 1996,1997,1998 Russell King
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#include <linux/linkage.h>
11#include <asm/assembler.h>
12
13		.text
14
15/* Prototype: int __clear_user(void *addr, size_t sz)
16 * Purpose  : clear some user memory
17 * Params   : addr - user memory address to clear
18 *          : sz   - number of bytes to clear
19 * Returns  : number of bytes NOT cleared
20 */
21ENTRY(__clear_user_std)
22WEAK(__clear_user)
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(		strnebt	r2, [r0])
45		mov	r0, #0
46		ldmfd	sp!, {r1, pc}
47ENDPROC(__clear_user)
48ENDPROC(__clear_user_std)
49
50		.pushsection .text.fixup,"ax"
51		.align	0
529001:		ldmfd	sp!, {r0, pc}
53		.popsection
54
55