Linux kernel mirror (for testing)
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linux
1/*
2 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18/*
19 * livepatch-shadow-fix2.c - Shadow variables, livepatch demo
20 *
21 * Purpose
22 * -------
23 *
24 * Adds functionality to livepatch-shadow-mod's in-flight data
25 * structures through a shadow variable. The livepatch patches a
26 * routine that periodically inspects data structures, incrementing a
27 * per-data-structure counter, creating the counter if needed.
28 *
29 *
30 * Usage
31 * -----
32 *
33 * This module is not intended to be standalone. See the "Usage"
34 * section of livepatch-shadow-mod.c.
35 */
36
37#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
38
39#include <linux/module.h>
40#include <linux/kernel.h>
41#include <linux/livepatch.h>
42#include <linux/slab.h>
43
44/* Shadow variable enums */
45#define SV_LEAK 1
46#define SV_COUNTER 2
47
48struct dummy {
49 struct list_head list;
50 unsigned long jiffies_expire;
51};
52
53bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
54{
55 int *shadow_count;
56
57 /*
58 * Patch: handle in-flight dummy structures, if they do not
59 * already have a SV_COUNTER shadow variable, then attach a
60 * new one.
61 */
62 shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
63 sizeof(*shadow_count), GFP_NOWAIT,
64 NULL, NULL);
65 if (shadow_count)
66 *shadow_count += 1;
67
68 return time_after(jiffies, d->jiffies_expire);
69}
70
71static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
72{
73 void *d = obj;
74 void **shadow_leak = shadow_data;
75
76 kfree(*shadow_leak);
77 pr_info("%s: dummy @ %p, prevented leak @ %p\n",
78 __func__, d, *shadow_leak);
79}
80
81void livepatch_fix2_dummy_free(struct dummy *d)
82{
83 void **shadow_leak;
84 int *shadow_count;
85
86 /* Patch: copy the memory leak patch from the fix1 module. */
87 shadow_leak = klp_shadow_get(d, SV_LEAK);
88 if (shadow_leak)
89 klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
90 else
91 pr_info("%s: dummy @ %p leaked!\n", __func__, d);
92
93 /*
94 * Patch: fetch the SV_COUNTER shadow variable and display
95 * the final count. Detach the shadow variable.
96 */
97 shadow_count = klp_shadow_get(d, SV_COUNTER);
98 if (shadow_count) {
99 pr_info("%s: dummy @ %p, check counter = %d\n",
100 __func__, d, *shadow_count);
101 klp_shadow_free(d, SV_COUNTER, NULL);
102 }
103
104 kfree(d);
105}
106
107static struct klp_func funcs[] = {
108 {
109 .old_name = "dummy_check",
110 .new_func = livepatch_fix2_dummy_check,
111 },
112 {
113 .old_name = "dummy_free",
114 .new_func = livepatch_fix2_dummy_free,
115 }, { }
116};
117
118static struct klp_object objs[] = {
119 {
120 .name = "livepatch_shadow_mod",
121 .funcs = funcs,
122 }, { }
123};
124
125static struct klp_patch patch = {
126 .mod = THIS_MODULE,
127 .objs = objs,
128};
129
130static int livepatch_shadow_fix2_init(void)
131{
132 int ret;
133
134 ret = klp_register_patch(&patch);
135 if (ret)
136 return ret;
137 ret = klp_enable_patch(&patch);
138 if (ret) {
139 WARN_ON(klp_unregister_patch(&patch));
140 return ret;
141 }
142 return 0;
143}
144
145static void livepatch_shadow_fix2_exit(void)
146{
147 /* Cleanup any existing SV_COUNTER shadow variables */
148 klp_shadow_free_all(SV_COUNTER, NULL);
149
150 WARN_ON(klp_unregister_patch(&patch));
151}
152
153module_init(livepatch_shadow_fix2_init);
154module_exit(livepatch_shadow_fix2_exit);
155MODULE_LICENSE("GPL");
156MODULE_INFO(livepatch, "Y");