| /* SPDX-License-Identifier: GPL-2.0-only */ |
| /* |
| * Copyright (C) 2021 Arm Ltd. |
| */ |
| |
| #include <linux/linkage.h> |
| #include <asm/asm-uaccess.h> |
| |
| .text |
| |
| /* Prototype: int __arch_clear_user(void *addr, size_t sz) |
| * Purpose : clear some user memory |
| * Params : addr - user memory address to clear |
| * : sz - number of bytes to clear |
| * Returns : number of bytes NOT cleared |
| * |
| * Alignment fixed up by hardware. |
| */ |
| |
| .p2align 4 |
| // Alignment is for the loop, but since the prologue (including BTI) |
| // is also 16 bytes we can keep any padding outside the function |
| SYM_FUNC_START(__arch_clear_user) |
| add x2, x0, x1 |
| subs x1, x1, #8 |
| b.mi 2f |
| 1: |
| USER(9f, sttr xzr, [x0]) |
| add x0, x0, #8 |
| subs x1, x1, #8 |
| b.hi 1b |
| USER(9f, sttr xzr, [x2, #-8]) |
| mov x0, #0 |
| ret |
| |
| 2: tbz x1, #2, 3f |
| USER(9f, sttr wzr, [x0]) |
| USER(8f, sttr wzr, [x2, #-4]) |
| mov x0, #0 |
| ret |
| |
| 3: tbz x1, #1, 4f |
| USER(9f, sttrh wzr, [x0]) |
| 4: tbz x1, #0, 5f |
| USER(7f, sttrb wzr, [x2, #-1]) |
| 5: mov x0, #0 |
| ret |
| |
| // Exception fixups |
| 7: sub x0, x2, #5 // Adjust for faulting on the final byte... |
| 8: add x0, x0, #4 // ...or the second word of the 4-7 byte case |
| 9: sub x0, x2, x0 |
| ret |
| SYM_FUNC_END(__arch_clear_user) |
| EXPORT_SYMBOL(__arch_clear_user) |
