livepatch: Remove immediate feature
[muen/linux.git] / samples / livepatch / livepatch-shadow-fix2.c
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;
56         int count;
57
58         /*
59          * Patch: handle in-flight dummy structures, if they do not
60          * already have a SV_COUNTER shadow variable, then attach a
61          * new one.
62          */
63         count = 0;
64         shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
65                                                &count, sizeof(count),
66                                                GFP_NOWAIT);
67         if (shadow_count)
68                 *shadow_count += 1;
69
70         return time_after(jiffies, d->jiffies_expire);
71 }
72
73 void livepatch_fix2_dummy_free(struct dummy *d)
74 {
75         void **shadow_leak, *leak;
76         int *shadow_count;
77
78         /* Patch: copy the memory leak patch from the fix1 module. */
79         shadow_leak = klp_shadow_get(d, SV_LEAK);
80         if (shadow_leak) {
81                 leak = *shadow_leak;
82                 klp_shadow_free(d, SV_LEAK);
83                 kfree(leak);
84                 pr_info("%s: dummy @ %p, prevented leak @ %p\n",
85                          __func__, d, leak);
86         } else {
87                 pr_info("%s: dummy @ %p leaked!\n", __func__, d);
88         }
89
90         /*
91          * Patch: fetch the SV_COUNTER shadow variable and display
92          * the final count.  Detach the shadow variable.
93          */
94         shadow_count = klp_shadow_get(d, SV_COUNTER);
95         if (shadow_count) {
96                 pr_info("%s: dummy @ %p, check counter = %d\n",
97                         __func__, d, *shadow_count);
98                 klp_shadow_free(d, SV_COUNTER);
99         }
100
101         kfree(d);
102 }
103
104 static struct klp_func funcs[] = {
105         {
106                 .old_name = "dummy_check",
107                 .new_func = livepatch_fix2_dummy_check,
108         },
109         {
110                 .old_name = "dummy_free",
111                 .new_func = livepatch_fix2_dummy_free,
112         }, { }
113 };
114
115 static struct klp_object objs[] = {
116         {
117                 .name = "livepatch_shadow_mod",
118                 .funcs = funcs,
119         }, { }
120 };
121
122 static struct klp_patch patch = {
123         .mod = THIS_MODULE,
124         .objs = objs,
125 };
126
127 static int livepatch_shadow_fix2_init(void)
128 {
129         int ret;
130
131         ret = klp_register_patch(&patch);
132         if (ret)
133                 return ret;
134         ret = klp_enable_patch(&patch);
135         if (ret) {
136                 WARN_ON(klp_unregister_patch(&patch));
137                 return ret;
138         }
139         return 0;
140 }
141
142 static void livepatch_shadow_fix2_exit(void)
143 {
144         /* Cleanup any existing SV_COUNTER shadow variables */
145         klp_shadow_free_all(SV_COUNTER);
146
147         WARN_ON(klp_unregister_patch(&patch));
148 }
149
150 module_init(livepatch_shadow_fix2_init);
151 module_exit(livepatch_shadow_fix2_exit);
152 MODULE_LICENSE("GPL");
153 MODULE_INFO(livepatch, "Y");