// SPDX-License-Identifier: GPL-2.0-or-later
|
/*
|
* Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
|
*/
|
|
/*
|
* 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;
|
};
|
|
static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
|
{
|
int *shadow_count;
|
|
/*
|
* Patch: handle in-flight dummy structures, if they do not
|
* already have a SV_COUNTER shadow variable, then attach a
|
* new one.
|
*/
|
shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
|
sizeof(*shadow_count), GFP_NOWAIT,
|
NULL, NULL);
|
if (shadow_count)
|
*shadow_count += 1;
|
|
return time_after(jiffies, d->jiffies_expire);
|
}
|
|
static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
|
{
|
void *d = obj;
|
int **shadow_leak = shadow_data;
|
|
kfree(*shadow_leak);
|
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
|
__func__, d, *shadow_leak);
|
}
|
|
static void livepatch_fix2_dummy_free(struct dummy *d)
|
{
|
int **shadow_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)
|
klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
|
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, NULL);
|
}
|
|
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)
|
{
|
return klp_enable_patch(&patch);
|
}
|
|
static void livepatch_shadow_fix2_exit(void)
|
{
|
/* Cleanup any existing SV_COUNTER shadow variables */
|
klp_shadow_free_all(SV_COUNTER, NULL);
|
}
|
|
module_init(livepatch_shadow_fix2_init);
|
module_exit(livepatch_shadow_fix2_exit);
|
MODULE_LICENSE("GPL");
|
MODULE_INFO(livepatch, "Y");
|
