summaryrefslogtreecommitdiffstats
path: root/samples/livepatch/livepatch-shadow-fix2.c
blob: ff9948f0ec007b77ff54a60cd6d88203d399cbc3 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
/*
 * 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;

	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");