clear_user.S (1206B)
1/* SPDX-License-Identifier: GPL-2.0-only */ 2/* 3 * Copyright (C) 2021 Arm Ltd. 4 */ 5 6#include <linux/linkage.h> 7#include <asm/asm-uaccess.h> 8 9 .text 10 11/* Prototype: int __arch_clear_user(void *addr, size_t sz) 12 * Purpose : clear some user memory 13 * Params : addr - user memory address to clear 14 * : sz - number of bytes to clear 15 * Returns : number of bytes NOT cleared 16 * 17 * Alignment fixed up by hardware. 18 */ 19 20 .p2align 4 21 // Alignment is for the loop, but since the prologue (including BTI) 22 // is also 16 bytes we can keep any padding outside the function 23SYM_FUNC_START(__arch_clear_user) 24 add x2, x0, x1 25 subs x1, x1, #8 26 b.mi 2f 271: 28USER(9f, sttr xzr, [x0]) 29 add x0, x0, #8 30 subs x1, x1, #8 31 b.hi 1b 32USER(9f, sttr xzr, [x2, #-8]) 33 mov x0, #0 34 ret 35 362: tbz x1, #2, 3f 37USER(9f, sttr wzr, [x0]) 38USER(8f, sttr wzr, [x2, #-4]) 39 mov x0, #0 40 ret 41 423: tbz x1, #1, 4f 43USER(9f, sttrh wzr, [x0]) 444: tbz x1, #0, 5f 45USER(7f, sttrb wzr, [x2, #-1]) 465: mov x0, #0 47 ret 48 49 // Exception fixups 507: sub x0, x2, #5 // Adjust for faulting on the final byte... 518: add x0, x0, #4 // ...or the second word of the 4-7 byte case 529: sub x0, x2, x0 53 ret 54SYM_FUNC_END(__arch_clear_user) 55EXPORT_SYMBOL(__arch_clear_user)