| 1 | /* |
| 2 | * alternative runtime patching |
| 3 | * inspired by the x86 version |
| 4 | * |
| 5 | * Copyright (C) 2014 ARM Ltd. |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License version 2 as |
| 9 | * published by the Free Software Foundation. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License |
| 17 | * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 18 | */ |
| 19 | |
| 20 | #define pr_fmt(fmt) "alternatives: " fmt |
| 21 | |
| 22 | #include <linux/init.h> |
| 23 | #include <linux/cpu.h> |
| 24 | #include <asm/cacheflush.h> |
| 25 | #include <asm/alternative.h> |
| 26 | #include <asm/cpufeature.h> |
| 27 | #include <linux/stop_machine.h> |
| 28 | |
| 29 | extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; |
| 30 | |
| 31 | struct alt_region { |
| 32 | struct alt_instr *begin; |
| 33 | struct alt_instr *end; |
| 34 | }; |
| 35 | |
| 36 | static int __apply_alternatives(void *alt_region) |
| 37 | { |
| 38 | struct alt_instr *alt; |
| 39 | struct alt_region *region = alt_region; |
| 40 | u8 *origptr, *replptr; |
| 41 | |
| 42 | for (alt = region->begin; alt < region->end; alt++) { |
| 43 | if (!cpus_have_cap(alt->cpufeature)) |
| 44 | continue; |
| 45 | |
| 46 | BUG_ON(alt->alt_len > alt->orig_len); |
| 47 | |
| 48 | pr_info_once("patching kernel code\n"); |
| 49 | |
| 50 | origptr = (u8 *)&alt->orig_offset + alt->orig_offset; |
| 51 | replptr = (u8 *)&alt->alt_offset + alt->alt_offset; |
| 52 | memcpy(origptr, replptr, alt->alt_len); |
| 53 | flush_icache_range((uintptr_t)origptr, |
| 54 | (uintptr_t)(origptr + alt->alt_len)); |
| 55 | } |
| 56 | |
| 57 | return 0; |
| 58 | } |
| 59 | |
| 60 | void apply_alternatives_all(void) |
| 61 | { |
| 62 | struct alt_region region = { |
| 63 | .begin = __alt_instructions, |
| 64 | .end = __alt_instructions_end, |
| 65 | }; |
| 66 | |
| 67 | /* better not try code patching on a live SMP system */ |
| 68 | stop_machine(__apply_alternatives, ®ion, NULL); |
| 69 | } |
| 70 | |
| 71 | void apply_alternatives(void *start, size_t length) |
| 72 | { |
| 73 | struct alt_region region = { |
| 74 | .begin = start, |
| 75 | .end = start + length, |
| 76 | }; |
| 77 | |
| 78 | __apply_alternatives(®ion); |
| 79 | } |
| 80 | |
| 81 | void free_alternatives_memory(void) |
| 82 | { |
| 83 | free_reserved_area(__alt_instructions, __alt_instructions_end, |
| 84 | 0, "alternatives"); |
| 85 | } |