/* * alternative runtime patching * inspired by the x86 version * * Copyright (C) 2014 ARM Ltd. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ #define pr_fmt(fmt) "alternatives: " fmt #include <linux/init.h> #include <linux/cpu.h> #include <asm/cacheflush.h> #include <asm/alternative.h> #include <asm/cpufeature.h> #include <linux/stop_machine.h> extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; struct alt_region { struct alt_instr *begin; struct alt_instr *end; }; static int __apply_alternatives(void *alt_region) { struct alt_instr *alt; struct alt_region *region = alt_region; u8 *origptr, *replptr; for (alt = region->begin; alt < region->end; alt++) { if (!cpus_have_cap(alt->cpufeature)) continue; BUG_ON(alt->alt_len != alt->orig_len); pr_info_once("patching kernel code\n"); origptr = (u8 *)&alt->orig_offset + alt->orig_offset; replptr = (u8 *)&alt->alt_offset + alt->alt_offset; memcpy(origptr, replptr, alt->alt_len); flush_icache_range((uintptr_t)origptr, (uintptr_t)(origptr + alt->alt_len)); } return 0; } void apply_alternatives_all(void) { struct alt_region region = { .begin = __alt_instructions, .end = __alt_instructions_end, }; /* better not try code patching on a live SMP system */ stop_machine(__apply_alternatives, ®ion, NULL); } void apply_alternatives(void *start, size_t length) { struct alt_region region = { .begin = start, .end = start + length, }; __apply_alternatives(®ion); } void free_alternatives_memory(void) { free_reserved_area(__alt_instructions, __alt_instructions_end, 0, "alternatives"); }