109 lines
2.7 KiB
C
109 lines
2.7 KiB
C
|
/*
|
||
|
|
* 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;
|
||
|
|
|
||
|
|
if (!klp_have_reliable_stack() && !patch.immediate) {
|
||
|
|
/*
|
||
|
|
* WARNING: Be very careful when using 'patch.immediate' in
|
||
|
|
* your patches. It's ok to use it for simple patches like
|
||
|
|
* this, but for more complex patches which change function
|
||
|
|
* semantics, locking semantics, or data structures, it may not
|
||
|
|
* be safe. Use of this option will also prevent removal of
|
||
|
|
* the patch.
|
||
|
|
*
|
||
|
|
* See Documentation/livepatch/livepatch.txt for more details.
|
||
|
|
*/
|
||
|
|
patch.immediate = true;
|
||
|
|
pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n");
|
||
|
|
}
|
||
|
|
|
||
|
|
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");
|