2 * linux/arch/arm/lib/clear_user.S
4 * Copyright (C) 1995, 1996,1997,1998 Russell King
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.
10 #include <linux/linkage.h>
11 #include <asm/assembler.h>
12 #include <asm/unwind.h>
13 #include <asm/export.h>
17 /* Prototype: unsigned long arm_clear_user(void *addr, size_t sz)
18 * Purpose : clear some user memory
19 * Params : addr - user memory address to clear
20 * : sz - number of bytes to clear
21 * Returns : number of bytes NOT cleared
23 ENTRY(__clear_user_std)
26 UNWIND(.save {r1, lr})
38 sub r1, r1, ip @ 7 6 5 4 3 2 1
39 1: subs r1, r1, #8 @ -1 -2 -3 -4 -5 -6 -7
40 strusr r2, r0, 4, pl, rept=2
42 adds r1, r1, #4 @ 3 2 1 0 -1 -2 -3
44 2: tst r1, #2 @ 1x 1x 0x 0x 1x 1x 0x
45 strusr r2, r0, 1, ne, rept=2
46 tst r1, #1 @ x1 x0 x1 x0 x1 x0 x1
47 it ne @ explicit IT needed for the label
48 USER( strnebt r2, [r0])
52 ENDPROC(arm_clear_user)
53 ENDPROC(__clear_user_std)
54 #ifndef CONFIG_UACCESS_WITH_MEMCPY
55 EXPORT_SYMBOL(arm_clear_user)
58 .pushsection .text.fixup,"ax"
60 9001: ldmfd sp!, {r0, pc}