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13d1cf7e SJ |
1 | /* |
2 | * livepatch-sample.c - Kernel Live Patching Sample Module | |
3 | * | |
4 | * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public License | |
8 | * as published by the Free Software Foundation; either version 2 | |
9 | * of the License, or (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program; if not, see <http://www.gnu.org/licenses/>. | |
18 | */ | |
19 | ||
20 | #include <linux/module.h> | |
21 | #include <linux/kernel.h> | |
22 | #include <linux/livepatch.h> | |
23 | ||
24 | /* | |
25 | * This (dumb) live patch overrides the function that prints the | |
26 | * kernel boot cmdline when /proc/cmdline is read. | |
27 | * | |
28 | * Example: | |
29 | * $ cat /proc/cmdline | |
30 | * <your cmdline> | |
31 | * $ insmod livepatch-sample.ko | |
32 | * $ cat /proc/cmdline | |
33 | * this has been live patched | |
34 | * $ echo 0 > /sys/kernel/livepatch/klp_sample/enabled | |
35 | * <your cmdline> | |
36 | */ | |
37 | ||
38 | #include <linux/seq_file.h> | |
39 | static int livepatch_cmdline_proc_show(struct seq_file *m, void *v) | |
40 | { | |
41 | seq_printf(m, "%s\n", "this has been live patched"); | |
42 | return 0; | |
43 | } | |
44 | ||
45 | static struct klp_func funcs[] = { | |
46 | { | |
47 | .old_name = "cmdline_proc_show", | |
48 | .new_func = livepatch_cmdline_proc_show, | |
49 | }, { } | |
50 | }; | |
51 | ||
52 | static struct klp_object objs[] = { | |
53 | { | |
54 | /* name being NULL means vmlinux */ | |
55 | .funcs = funcs, | |
56 | }, { } | |
57 | }; | |
58 | ||
59 | static struct klp_patch patch = { | |
60 | .mod = THIS_MODULE, | |
61 | .objs = objs, | |
62 | }; | |
63 | ||
64 | static int livepatch_init(void) | |
65 | { | |
66 | int ret; | |
67 | ||
68 | ret = klp_register_patch(&patch); | |
69 | if (ret) | |
70 | return ret; | |
71 | ret = klp_enable_patch(&patch); | |
72 | if (ret) { | |
73 | WARN_ON(klp_unregister_patch(&patch)); | |
74 | return ret; | |
75 | } | |
76 | return 0; | |
77 | } | |
78 | ||
79 | static void livepatch_exit(void) | |
80 | { | |
81 | WARN_ON(klp_disable_patch(&patch)); | |
82 | WARN_ON(klp_unregister_patch(&patch)); | |
83 | } | |
84 | ||
85 | module_init(livepatch_init); | |
86 | module_exit(livepatch_exit); | |
87 | MODULE_LICENSE("GPL"); |