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 .fixup,"ax" 51 .align 0 529001: ldmfd sp!, {r0, pc} 53 .popsection 54 55