projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 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 | ||
| d83a7cb3 JP |
20 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 21 | ||
| 13d1cf7e SJ |
22 | #include <linux/module.h> |
| 23 | #include <linux/kernel.h> | |
| 24 | #include <linux/livepatch.h> | |
| 25 | ||
| 26 | /* | |
| 27 | * This (dumb) live patch overrides the function that prints the | |
| 28 | * kernel boot cmdline when /proc/cmdline is read. | |
| 29 | * | |
| 30 | * Example: | |
| 700a3048 | 31 | * |
| 13d1cf7e SJ |
32 | * $ cat /proc/cmdline |
| 33 | * <your cmdline> | |
| 700a3048 | 34 | * |
| 13d1cf7e SJ |
35 | * $ insmod livepatch-sample.ko |
| 36 | * $ cat /proc/cmdline | |
| 37 | * this has been live patched | |
| 700a3048 JP |
38 | * |
| 39 | * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled | |
| 40 | * $ cat /proc/cmdline | |
| 13d1cf7e SJ |
41 | * <your cmdline> |
| 42 | */ | |
| 43 | ||
| 44 | #include <linux/seq_file.h> | |
| 45 | static int livepatch_cmdline_proc_show(struct seq_file *m, void *v) | |
| 46 | { | |
| 47 | seq_printf(m, "%s\n", "this has been live patched"); | |
| 48 | return 0; | |
| 49 | } | |
| 50 | ||
| 51 | static struct klp_func funcs[] = { | |
| 52 | { | |
| 53 | .old_name = "cmdline_proc_show", | |
| 54 | .new_func = livepatch_cmdline_proc_show, | |
| 55 | }, { } | |
| 56 | }; | |
| 57 | ||
| 58 | static struct klp_object objs[] = { | |
| 59 | { | |
| 60 | /* name being NULL means vmlinux */ | |
| 61 | .funcs = funcs, | |
| 62 | }, { } | |
| 63 | }; | |
| 64 | ||
| 65 | static struct klp_patch patch = { | |
| 66 | .mod = THIS_MODULE, | |
| 67 | .objs = objs, | |
| 68 | }; | |
| 69 | ||
| 70 | static int livepatch_init(void) | |
| 71 | { | |
| 72 | int ret; | |
| 73 | ||
| 74 | ret = klp_register_patch(&patch); | |
| 75 | if (ret) | |
| 76 | return ret; | |
| 77 | ret = klp_enable_patch(&patch); | |
| 78 | if (ret) { | |
| 79 | WARN_ON(klp_unregister_patch(&patch)); | |
| 80 | return ret; | |
| 81 | } | |
| 82 | return 0; | |
| 83 | } | |
| 84 | ||
| 85 | static void livepatch_exit(void) | |
| 86 | { | |
| 13d1cf7e SJ |
87 | WARN_ON(klp_unregister_patch(&patch)); |
| 88 | } | |
| 89 | ||
| 90 | module_init(livepatch_init); | |
| 91 | module_exit(livepatch_exit); | |
| 92 | MODULE_LICENSE("GPL"); | |
| 425595a7 | 93 | MODULE_INFO(livepatch, "Y"); |