1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-or-later
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * livepatch-sample.c - Kernel Live Patching Sample Module
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
6*4882a593Smuzhiyun */
7*4882a593Smuzhiyun
8*4882a593Smuzhiyun #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9*4882a593Smuzhiyun
10*4882a593Smuzhiyun #include <linux/module.h>
11*4882a593Smuzhiyun #include <linux/kernel.h>
12*4882a593Smuzhiyun #include <linux/livepatch.h>
13*4882a593Smuzhiyun
14*4882a593Smuzhiyun /*
15*4882a593Smuzhiyun * This (dumb) live patch overrides the function that prints the
16*4882a593Smuzhiyun * kernel boot cmdline when /proc/cmdline is read.
17*4882a593Smuzhiyun *
18*4882a593Smuzhiyun * Example:
19*4882a593Smuzhiyun *
20*4882a593Smuzhiyun * $ cat /proc/cmdline
21*4882a593Smuzhiyun * <your cmdline>
22*4882a593Smuzhiyun *
23*4882a593Smuzhiyun * $ insmod livepatch-sample.ko
24*4882a593Smuzhiyun * $ cat /proc/cmdline
25*4882a593Smuzhiyun * this has been live patched
26*4882a593Smuzhiyun *
27*4882a593Smuzhiyun * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
28*4882a593Smuzhiyun * $ cat /proc/cmdline
29*4882a593Smuzhiyun * <your cmdline>
30*4882a593Smuzhiyun */
31*4882a593Smuzhiyun
32*4882a593Smuzhiyun #include <linux/seq_file.h>
livepatch_cmdline_proc_show(struct seq_file * m,void * v)33*4882a593Smuzhiyun static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)
34*4882a593Smuzhiyun {
35*4882a593Smuzhiyun seq_printf(m, "%s\n", "this has been live patched");
36*4882a593Smuzhiyun return 0;
37*4882a593Smuzhiyun }
38*4882a593Smuzhiyun
39*4882a593Smuzhiyun static struct klp_func funcs[] = {
40*4882a593Smuzhiyun {
41*4882a593Smuzhiyun .old_name = "cmdline_proc_show",
42*4882a593Smuzhiyun .new_func = livepatch_cmdline_proc_show,
43*4882a593Smuzhiyun }, { }
44*4882a593Smuzhiyun };
45*4882a593Smuzhiyun
46*4882a593Smuzhiyun static struct klp_object objs[] = {
47*4882a593Smuzhiyun {
48*4882a593Smuzhiyun /* name being NULL means vmlinux */
49*4882a593Smuzhiyun .funcs = funcs,
50*4882a593Smuzhiyun }, { }
51*4882a593Smuzhiyun };
52*4882a593Smuzhiyun
53*4882a593Smuzhiyun static struct klp_patch patch = {
54*4882a593Smuzhiyun .mod = THIS_MODULE,
55*4882a593Smuzhiyun .objs = objs,
56*4882a593Smuzhiyun };
57*4882a593Smuzhiyun
livepatch_init(void)58*4882a593Smuzhiyun static int livepatch_init(void)
59*4882a593Smuzhiyun {
60*4882a593Smuzhiyun return klp_enable_patch(&patch);
61*4882a593Smuzhiyun }
62*4882a593Smuzhiyun
livepatch_exit(void)63*4882a593Smuzhiyun static void livepatch_exit(void)
64*4882a593Smuzhiyun {
65*4882a593Smuzhiyun }
66*4882a593Smuzhiyun
67*4882a593Smuzhiyun module_init(livepatch_init);
68*4882a593Smuzhiyun module_exit(livepatch_exit);
69*4882a593Smuzhiyun MODULE_LICENSE("GPL");
70*4882a593Smuzhiyun MODULE_INFO(livepatch, "Y");
71