samples/livepatch/livepatch-sample.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * livepatch-sample.c - Kernel Live Patching Sample Module
0004  *
0005  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
0006  */
0007
0008 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0009
0010 #include <linux/module.h>
0011 #include <linux/kernel.h>
0012 #include <linux/livepatch.h>
0013
0014 /*
0015  * This (dumb) live patch overrides the function that prints the
0016  * kernel boot cmdline when /proc/cmdline is read.
0017  *
0018  * Example:
0019  *
0020  * $ cat /proc/cmdline
0021  * <your cmdline>
0022  *
0023  * $ insmod livepatch-sample.ko
0024  * $ cat /proc/cmdline
0025  * this has been live patched
0026  *
0027  * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
0028  * $ cat /proc/cmdline
0029  * <your cmdline>
0030  */
0031
0032 #include <linux/seq_file.h>
0033 static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)
0034 {
0035     seq_printf(m, "%s\n", "this has been live patched");
0036     return 0;
0037 }
0038
0039 static struct klp_func funcs[] = {
0040     {
0041         .old_name = "cmdline_proc_show",
0042         .new_func = livepatch_cmdline_proc_show,
0043     }, { }
0044 };
0045
0046 static struct klp_object objs[] = {
0047     {
0048         /* name being NULL means vmlinux */
0049         .funcs = funcs,
0050     }, { }
0051 };
0052
0053 static struct klp_patch patch = {
0054     .mod = THIS_MODULE,
0055     .objs = objs,
0056 };
0057
0058 static int livepatch_init(void)
0059 {
0060     return klp_enable_patch(&patch);
0061 }
0062
0063 static void livepatch_exit(void)
0064 {
0065 }
0066
0067 module_init(livepatch_init);
0068 module_exit(livepatch_exit);
0069 MODULE_LICENSE("GPL");
0070 MODULE_INFO(livepatch, "Y");