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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 21 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: 31 * 32 * $ cat /proc/cmdline 33 * <your cmdline> 34 * 35 * $ insmod livepatch-sample.ko 36 * $ cat /proc/cmdline 37 * this has been live patched 38 * 39 * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled 40 * $ cat /proc/cmdline 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 return klp_enable_patch(&patch); 73 } 74 75 static void livepatch_exit(void) 76 { 77 } 78 79 module_init(livepatch_init); 80 module_exit(livepatch_exit); 81 MODULE_LICENSE("GPL"); 82 MODULE_INFO(livepatch, "Y"); 83