Quelle livepatch-shadow-fix2.c Sprache: C

// 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;

pr_info("%s: dummy @ %p, prevented leak @ %p\n",
    __func__, d, *shadow_leak);
kfree(*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_DESCRIPTION("Live patching demo for shadow variables");
MODULE_LICENSE("GPL");
MODULE_INFO(livepatch, "Y");

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