1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * livepatch-sample.c - Kernel Live Patching Sample Module
4 *
5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
6 */
7
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
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:
19 *
20 * $ cat /proc/cmdline
21 * <your cmdline>
22 *
23 * $ insmod livepatch-sample.ko
24 * $ cat /proc/cmdline
25 * this has been live patched
26 *
27 * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
28 * $ cat /proc/cmdline
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 {
60 return klp_enable_patch(&patch);
61 }
62
63 static void livepatch_exit(void)
64 {
65 }
66
67 module_init(livepatch_init);
68 module_exit(livepatch_exit);
69 MODULE_LICENSE("GPL");
70 MODULE_INFO(livepatch, "Y");
71
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