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
29extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
30
31struct alt_region {
32	struct alt_instr *begin;
33	struct alt_instr *end;
34};
35
36static 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
60void 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, &region, NULL);
69}
70
71void 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(&region);
79}
80
81void free_alternatives_memory(void)
82{
83	free_reserved_area(__alt_instructions, __alt_instructions_end,
84			   0, "alternatives");
85}
86