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#include <asm/unwind.h>
13
14		.text
15
16/* Prototype: unsigned long arm_clear_user(void *addr, size_t sz)
17 * Purpose  : clear some user memory
18 * Params   : addr - user memory address to clear
19 *          : sz   - number of bytes to clear
20 * Returns  : number of bytes NOT cleared
21 */
22ENTRY(__clear_user_std)
23WEAK(arm_clear_user)
24UNWIND(.fnstart)
25UNWIND(.save {r1, lr})
26		stmfd	sp!, {r1, lr}
27		mov	r2, #0
28		cmp	r1, #4
29		blt	2f
30		ands	ip, r0, #3
31		beq	1f
32		cmp	ip, #2
33		strusr	r2, r0, 1
34		strusr	r2, r0, 1, le
35		strusr	r2, r0, 1, lt
36		rsb	ip, ip, #4
37		sub	r1, r1, ip		@  7  6  5  4  3  2  1
381:		subs	r1, r1, #8		@ -1 -2 -3 -4 -5 -6 -7
39		strusr	r2, r0, 4, pl, rept=2
40		bpl	1b
41		adds	r1, r1, #4		@  3  2  1  0 -1 -2 -3
42		strusr	r2, r0, 4, pl
432:		tst	r1, #2			@ 1x 1x 0x 0x 1x 1x 0x
44		strusr	r2, r0, 1, ne, rept=2
45		tst	r1, #1			@ x1 x0 x1 x0 x1 x0 x1
46		it	ne			@ explicit IT needed for the label
47USER(		strnebt	r2, [r0])
48		mov	r0, #0
49		ldmfd	sp!, {r1, pc}
50UNWIND(.fnend)
51ENDPROC(arm_clear_user)
52ENDPROC(__clear_user_std)
53
54		.pushsection .text.fixup,"ax"
55		.align	0
569001:		ldmfd	sp!, {r0, pc}
57		.popsection
58
59