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, fmt: "%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 | |