71 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * livepatch-sample.c - Kernel Live Patching Sample Module4 *5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>6 */7 8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt9 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 the16 * kernel boot cmdline when /proc/cmdline is read.17 *18 * Example:19 *20 * $ cat /proc/cmdline21 * <your cmdline>22 *23 * $ insmod livepatch-sample.ko24 * $ cat /proc/cmdline25 * this has been live patched26 *27 * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled28 * $ cat /proc/cmdline29 * <your cmdline>30 */31 32#include <linux/seq_file.h>33static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)34{35 seq_printf(m, "%s\n", "this has been live patched");36 return 0;37}38 39static struct klp_func funcs[] = {40 {41 .old_name = "cmdline_proc_show",42 .new_func = livepatch_cmdline_proc_show,43 }, { }44};45 46static struct klp_object objs[] = {47 {48 /* name being NULL means vmlinux */49 .funcs = funcs,50 }, { }51};52 53static struct klp_patch patch = {54 .mod = THIS_MODULE,55 .objs = objs,56};57 58static int livepatch_init(void)59{60 return klp_enable_patch(&patch);61}62 63static void livepatch_exit(void)64{65}66 67module_init(livepatch_init);68module_exit(livepatch_exit);69MODULE_LICENSE("GPL");70MODULE_INFO(livepatch, "Y");71