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1ccea77e | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
13d1cf7e SJ |
2 | /* |
3 | * livepatch-sample.c - Kernel Live Patching Sample Module | |
4 | * | |
5 | * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> | |
13d1cf7e SJ |
6 | */ |
7 | ||
d83a7cb3 JP |
8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
9 | ||
13d1cf7e SJ |
10 | #include <linux/module.h> |
11 | #include <linux/kernel.h> | |
12 | #include <linux/livepatch.h> | |
13 | ||
14 | /* | |
15 | * This (dumb) live patch overrides the function that prints the | |
16 | * kernel boot cmdline when /proc/cmdline is read. | |
17 | * | |
18 | * Example: | |
700a3048 | 19 | * |
13d1cf7e SJ |
20 | * $ cat /proc/cmdline |
21 | * <your cmdline> | |
700a3048 | 22 | * |
13d1cf7e SJ |
23 | * $ insmod livepatch-sample.ko |
24 | * $ cat /proc/cmdline | |
25 | * this has been live patched | |
700a3048 JP |
26 | * |
27 | * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled | |
28 | * $ cat /proc/cmdline | |
13d1cf7e SJ |
29 | * <your cmdline> |
30 | */ | |
31 | ||
32 | #include <linux/seq_file.h> | |
33 | static int livepatch_cmdline_proc_show(struct seq_file *m, void *v) | |
34 | { | |
35 | seq_printf(m, "%s\n", "this has been live patched"); | |
36 | return 0; | |
37 | } | |
38 | ||
39 | static struct klp_func funcs[] = { | |
40 | { | |
41 | .old_name = "cmdline_proc_show", | |
42 | .new_func = livepatch_cmdline_proc_show, | |
43 | }, { } | |
44 | }; | |
45 | ||
46 | static struct klp_object objs[] = { | |
47 | { | |
48 | /* name being NULL means vmlinux */ | |
49 | .funcs = funcs, | |
50 | }, { } | |
51 | }; | |
52 | ||
53 | static struct klp_patch patch = { | |
54 | .mod = THIS_MODULE, | |
55 | .objs = objs, | |
56 | }; | |
57 | ||
58 | static int livepatch_init(void) | |
59 | { | |
958ef1e3 | 60 | return klp_enable_patch(&patch); |
13d1cf7e SJ |
61 | } |
62 | ||
63 | static void livepatch_exit(void) | |
64 | { | |
13d1cf7e SJ |
65 | } |
66 | ||
67 | module_init(livepatch_init); | |
68 | module_exit(livepatch_exit); | |
69 | MODULE_LICENSE("GPL"); | |
425595a7 | 70 | MODULE_INFO(livepatch, "Y"); |