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/*
* Copyright (C) 2017 Joe Lawrence <joe.lawrence@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/>.
*/
/*
* livepatch-shadow-fix2.c - Shadow variables, livepatch demo
*
* Purpose
* -------
*
* Adds functionality to livepatch-shadow-mod's in-flight data
* structures through a shadow variable. The livepatch patches a
* routine that periodically inspects data structures, incrementing a
* per-data-structure counter, creating the counter if needed.
*
*
* Usage
* -----
*
* This module is not intended to be standalone. See the "Usage"
* section of livepatch-shadow-mod.c.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/livepatch.h>
#include <linux/slab.h>
/* Shadow variable enums */
#define SV_LEAK 1
#define SV_COUNTER 2
struct dummy {
struct list_head list;
unsigned long jiffies_expire;
};
bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
{
int *shadow_count;
int count;
/*
* Patch: handle in-flight dummy structures, if they do not
* already have a SV_COUNTER shadow variable, then attach a
* new one.
*/
count = 0;
shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
&count, sizeof(count),
GFP_NOWAIT);
if (shadow_count)
*shadow_count += 1;
return time_after(jiffies, d->jiffies_expire);
}
void livepatch_fix2_dummy_free(struct dummy *d)
{
void **shadow_leak, *leak;
int *shadow_count;
/* Patch: copy the memory leak patch from the fix1 module. */
shadow_leak = klp_shadow_get(d, SV_LEAK);
if (shadow_leak) {
leak = *shadow_leak;
klp_shadow_free(d, SV_LEAK);
kfree(leak);
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
__func__, d, leak);
} else {
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
}
/*
* Patch: fetch the SV_COUNTER shadow variable and display
* the final count. Detach the shadow variable.
*/
shadow_count = klp_shadow_get(d, SV_COUNTER);
if (shadow_count) {
pr_info("%s: dummy @ %p, check counter = %d\n",
__func__, d, *shadow_count);
klp_shadow_free(d, SV_COUNTER);
}
kfree(d);
}
static struct klp_func funcs[] = {
{
.old_name = "dummy_check",
.new_func = livepatch_fix2_dummy_check,
},
{
.old_name = "dummy_free",
.new_func = livepatch_fix2_dummy_free,
}, { }
};
static struct klp_object objs[] = {
{
.name = "livepatch_shadow_mod",
.funcs = funcs,
}, { }
};
static struct klp_patch patch = {
.mod = THIS_MODULE,
.objs = objs,
};
static int livepatch_shadow_fix2_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_shadow_fix2_exit(void)
{
/* Cleanup any existing SV_COUNTER shadow variables */
klp_shadow_free_all(SV_COUNTER);
WARN_ON(klp_unregister_patch(&patch));
}
module_init(livepatch_shadow_fix2_init);
module_exit(livepatch_shadow_fix2_exit);
MODULE_LICENSE("GPL");
MODULE_INFO(livepatch, "Y");
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