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 } 86