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439e7271 JL |
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 | ||
48 | struct dummy { | |
49 | struct list_head list; | |
50 | unsigned long jiffies_expire; | |
51 | }; | |
52 | ||
53 | bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies) | |
54 | { | |
55 | int *shadow_count; | |
439e7271 JL |
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 | */ | |
439e7271 | 62 | shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER, |
e91c2518 PM |
63 | sizeof(*shadow_count), GFP_NOWAIT, |
64 | NULL, NULL); | |
439e7271 JL |
65 | if (shadow_count) |
66 | *shadow_count += 1; | |
67 | ||
68 | return time_after(jiffies, d->jiffies_expire); | |
69 | } | |
70 | ||
3b2c77d0 PM |
71 | static 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 | ||
439e7271 JL |
81 | void livepatch_fix2_dummy_free(struct dummy *d) |
82 | { | |
3b2c77d0 | 83 | void **shadow_leak; |
439e7271 JL |
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); | |
3b2c77d0 PM |
88 | if (shadow_leak) |
89 | klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor); | |
90 | else | |
439e7271 | 91 | pr_info("%s: dummy @ %p leaked!\n", __func__, d); |
439e7271 JL |
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); | |
3b2c77d0 | 101 | klp_shadow_free(d, SV_COUNTER, NULL); |
439e7271 JL |
102 | } |
103 | ||
104 | kfree(d); | |
105 | } | |
106 | ||
107 | static 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 | ||
118 | static struct klp_object objs[] = { | |
119 | { | |
120 | .name = "livepatch_shadow_mod", | |
121 | .funcs = funcs, | |
122 | }, { } | |
123 | }; | |
124 | ||
125 | static struct klp_patch patch = { | |
126 | .mod = THIS_MODULE, | |
127 | .objs = objs, | |
128 | }; | |
129 | ||
130 | static int livepatch_shadow_fix2_init(void) | |
131 | { | |
132 | int ret; | |
133 | ||
439e7271 JL |
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 | ||
145 | static void livepatch_shadow_fix2_exit(void) | |
146 | { | |
147 | /* Cleanup any existing SV_COUNTER shadow variables */ | |
3b2c77d0 | 148 | klp_shadow_free_all(SV_COUNTER, NULL); |
439e7271 JL |
149 | |
150 | WARN_ON(klp_unregister_patch(&patch)); | |
151 | } | |
152 | ||
153 | module_init(livepatch_shadow_fix2_init); | |
154 | module_exit(livepatch_shadow_fix2_exit); | |
155 | MODULE_LICENSE("GPL"); | |
156 | MODULE_INFO(livepatch, "Y"); |