1// SPDX-License-Identifier: GPL-2.0
2#include <linux/module.h>
3#include <linux/cpu.h>
4#include <linux/smp.h>
5#include <asm/text-patching.h>
6#include <asm/alternative.h>
7#include <asm/facility.h>
8#include <asm/nospec-branch.h>
9
10static int __initdata_or_module alt_instr_disabled;
11
12static int __init disable_alternative_instructions(char *str)
13{
14 alt_instr_disabled = 1;
15 return 0;
16}
17
18early_param("noaltinstr", disable_alternative_instructions);
19
20static void __init_or_module __apply_alternatives(struct alt_instr *start,
21 struct alt_instr *end)
22{
23 struct alt_instr *a;
24 u8 *instr, *replacement;
25
26 /*
27 * The scan order should be from start to end. A later scanned
28 * alternative code can overwrite previously scanned alternative code.
29 */
30 for (a = start; a < end; a++) {
31 instr = (u8 *)&a->instr_offset + a->instr_offset;
32 replacement = (u8 *)&a->repl_offset + a->repl_offset;
33
34 if (!__test_facility(a->facility, alt_stfle_fac_list))
35 continue;
36
37 if (unlikely(a->instrlen % 2)) {
38 WARN_ONCE(1, "cpu alternatives instructions length is "
39 "odd, skipping patching\n");
40 continue;
41 }
42
43 s390_kernel_write(instr, replacement, a->instrlen);
44 }
45}
46
47void __init_or_module apply_alternatives(struct alt_instr *start,
48 struct alt_instr *end)
49{
50 if (!alt_instr_disabled)
51 __apply_alternatives(start, end);
52}
53
54extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
55void __init apply_alternative_instructions(void)
56{
57 apply_alternatives(start: __alt_instructions, end: __alt_instructions_end);
58}
59
60static void do_sync_core(void *info)
61{
62 sync_core();
63}
64
65void text_poke_sync(void)
66{
67 on_each_cpu(func: do_sync_core, NULL, wait: 1);
68}
69
70void text_poke_sync_lock(void)
71{
72 cpus_read_lock();
73 text_poke_sync();
74 cpus_read_unlock();
75}
76

source code of linux/arch/s390/kernel/alternative.c