1/* 2 * Based on arch/arm/lib/clear_user.S 3 * 4 * Copyright (C) 2012 ARM Ltd. 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 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program. If not, see <http://www.gnu.org/licenses/>. 17 */ 18#include <linux/linkage.h> 19 20#include <asm/asm-uaccess.h> 21 22 .text 23 24/* Prototype: int __clear_user(void *addr, size_t sz) 25 * Purpose : clear some user memory 26 * Params : addr - user memory address to clear 27 * : sz - number of bytes to clear 28 * Returns : number of bytes NOT cleared 29 * 30 * Alignment fixed up by hardware. 31 */ 32ENTRY(__clear_user) 33 uaccess_enable_not_uao x2, x3 34 mov x2, x1 // save the size for fixup return 35 subs x1, x1, #8 36 b.mi 2f 371: 38uao_user_alternative 9f, str, sttr, xzr, x0, 8 39 subs x1, x1, #8 40 b.pl 1b 412: adds x1, x1, #4 42 b.mi 3f 43uao_user_alternative 9f, str, sttr, wzr, x0, 4 44 sub x1, x1, #4 453: adds x1, x1, #2 46 b.mi 4f 47uao_user_alternative 9f, strh, sttrh, wzr, x0, 2 48 sub x1, x1, #2 494: adds x1, x1, #1 50 b.mi 5f 51uao_user_alternative 9f, strb, sttrb, wzr, x0, 0 525: mov x0, #0 53 uaccess_disable_not_uao x2 54 ret 55ENDPROC(__clear_user) 56 57 .section .fixup,"ax" 58 .align 2 599: mov x0, x2 // return the original size 60 ret 61 .previous 62