cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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livepatch-shadow-fix2.c (2990B)


      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
      4 */
      5
      6/*
      7 * livepatch-shadow-fix2.c - Shadow variables, livepatch demo
      8 *
      9 * Purpose
     10 * -------
     11 *
     12 * Adds functionality to livepatch-shadow-mod's in-flight data
     13 * structures through a shadow variable.  The livepatch patches a
     14 * routine that periodically inspects data structures, incrementing a
     15 * per-data-structure counter, creating the counter if needed.
     16 *
     17 *
     18 * Usage
     19 * -----
     20 *
     21 * This module is not intended to be standalone.  See the "Usage"
     22 * section of livepatch-shadow-mod.c.
     23 */
     24
     25#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
     26
     27#include <linux/module.h>
     28#include <linux/kernel.h>
     29#include <linux/livepatch.h>
     30#include <linux/slab.h>
     31
     32/* Shadow variable enums */
     33#define SV_LEAK		1
     34#define SV_COUNTER	2
     35
     36struct dummy {
     37	struct list_head list;
     38	unsigned long jiffies_expire;
     39};
     40
     41static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
     42{
     43	int *shadow_count;
     44
     45	/*
     46	 * Patch: handle in-flight dummy structures, if they do not
     47	 * already have a SV_COUNTER shadow variable, then attach a
     48	 * new one.
     49	 */
     50	shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
     51				sizeof(*shadow_count), GFP_NOWAIT,
     52				NULL, NULL);
     53	if (shadow_count)
     54		*shadow_count += 1;
     55
     56	return time_after(jiffies, d->jiffies_expire);
     57}
     58
     59static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
     60{
     61	void *d = obj;
     62	int **shadow_leak = shadow_data;
     63
     64	pr_info("%s: dummy @ %p, prevented leak @ %p\n",
     65			 __func__, d, *shadow_leak);
     66	kfree(*shadow_leak);
     67}
     68
     69static void livepatch_fix2_dummy_free(struct dummy *d)
     70{
     71	int **shadow_leak;
     72	int *shadow_count;
     73
     74	/* Patch: copy the memory leak patch from the fix1 module. */
     75	shadow_leak = klp_shadow_get(d, SV_LEAK);
     76	if (shadow_leak)
     77		klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
     78	else
     79		pr_info("%s: dummy @ %p leaked!\n", __func__, d);
     80
     81	/*
     82	 * Patch: fetch the SV_COUNTER shadow variable and display
     83	 * the final count.  Detach the shadow variable.
     84	 */
     85	shadow_count = klp_shadow_get(d, SV_COUNTER);
     86	if (shadow_count) {
     87		pr_info("%s: dummy @ %p, check counter = %d\n",
     88			__func__, d, *shadow_count);
     89		klp_shadow_free(d, SV_COUNTER, NULL);
     90	}
     91
     92	kfree(d);
     93}
     94
     95static struct klp_func funcs[] = {
     96	{
     97		.old_name = "dummy_check",
     98		.new_func = livepatch_fix2_dummy_check,
     99	},
    100	{
    101		.old_name = "dummy_free",
    102		.new_func = livepatch_fix2_dummy_free,
    103	}, { }
    104};
    105
    106static struct klp_object objs[] = {
    107	{
    108		.name = "livepatch_shadow_mod",
    109		.funcs = funcs,
    110	}, { }
    111};
    112
    113static struct klp_patch patch = {
    114	.mod = THIS_MODULE,
    115	.objs = objs,
    116};
    117
    118static int livepatch_shadow_fix2_init(void)
    119{
    120	return klp_enable_patch(&patch);
    121}
    122
    123static void livepatch_shadow_fix2_exit(void)
    124{
    125	/* Cleanup any existing SV_COUNTER shadow variables */
    126	klp_shadow_free_all(SV_COUNTER, NULL);
    127}
    128
    129module_init(livepatch_shadow_fix2_init);
    130module_exit(livepatch_shadow_fix2_exit);
    131MODULE_LICENSE("GPL");
    132MODULE_INFO(livepatch, "Y");