LXR linux/samples/livepatch/livepatch-sample.c

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * livepatch-sample.c - Kernel Live Patching Sample Module
   4 *
   5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   6 */
   7
   8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  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 the
  16 * kernel boot cmdline when /proc/cmdline is read.
  17 *
  18 * Example:
  19 *
  20 * $ cat /proc/cmdline
  21 * <your cmdline>
  22 *
  23 * $ insmod livepatch-sample.ko
  24 * $ cat /proc/cmdline
  25 * this has been live patched
  26 *
  27 * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
  28 * $ cat /proc/cmdline
  29 * <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