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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 <[email protected]>
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_DESCRIPTION("Kernel Live Patching Sample Module");
70	MODULE_LICENSE("GPL");
71	MODULE_INFO(livepatch, "Y");
72

livepatch-sample.c