/* * livepatch-sample.c - Kernel Live Patching Sample Module * * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, see <http://www.gnu.org/licenses/>. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> #include <linux/kernel.h> #include <linux/livepatch.h> /* * This (dumb) live patch overrides the function that prints the * kernel boot cmdline when /proc/cmdline is read. * * Example: * * $ cat /proc/cmdline * <your cmdline> * * $ insmod livepatch-sample.ko * $ cat /proc/cmdline * this has been live patched * * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled * $ cat /proc/cmdline * <your cmdline> */ #include <linux/seq_file.h> static int livepatch_cmdline_proc_show(struct seq_file *m, void *v) { seq_printf(m, "%s\n", "this has been live patched"); return 0; } static struct klp_func funcs[] = { { .old_name = "cmdline_proc_show", .new_func = livepatch_cmdline_proc_show, }, { } }; static struct klp_object objs[] = { { /* name being NULL means vmlinux */ .funcs = funcs, }, { } }; static struct klp_patch patch = { .mod = THIS_MODULE, .objs = objs, }; static int livepatch_init(void) { int ret; ret = klp_register_patch(&patch); if (ret) return ret; ret = klp_enable_patch(&patch); if (ret) { WARN_ON(klp_unregister_patch(&patch)); return ret; } return 0; } static void livepatch_exit(void) { WARN_ON(klp_unregister_patch(&patch)); } module_init(livepatch_init); module_exit(livepatch_exit); MODULE_LICENSE("GPL"); MODULE_INFO(livepatch, "Y");