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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-callbacks-demo.c - (un)patching callbacks livepatch demo | |
20 | * | |
21 | * | |
22 | * Purpose | |
23 | * ------- | |
24 | * | |
25 | * Demonstration of registering livepatch (un)patching callbacks. | |
26 | * | |
27 | * | |
28 | * Usage | |
29 | * ----- | |
30 | * | |
31 | * Step 1 - load the simple module | |
32 | * | |
33 | * insmod samples/livepatch/livepatch-callbacks-mod.ko | |
34 | * | |
35 | * | |
36 | * Step 2 - load the demonstration livepatch (with callbacks) | |
37 | * | |
38 | * insmod samples/livepatch/livepatch-callbacks-demo.ko | |
39 | * | |
40 | * | |
41 | * Step 3 - cleanup | |
42 | * | |
43 | * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled | |
44 | * rmmod livepatch_callbacks_demo | |
45 | * rmmod livepatch_callbacks_mod | |
46 | * | |
47 | * Watch dmesg output to see livepatch enablement, callback execution | |
48 | * and patching operations for both vmlinux and module targets. | |
49 | * | |
50 | * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and | |
51 | * livepatch-callbacks-demo.ko to observe what happens when a | |
52 | * target module is loaded after a livepatch with callbacks. | |
53 | * | |
54 | * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch | |
55 | * callback return status. Try setting up a non-zero status | |
56 | * such as -19 (-ENODEV): | |
57 | * | |
58 | * # Load demo livepatch, vmlinux is patched | |
59 | * insmod samples/livepatch/livepatch-callbacks-demo.ko | |
60 | * | |
61 | * # Setup next pre-patch callback to return -ENODEV | |
62 | * echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret | |
63 | * | |
64 | * # Module loader refuses to load the target module | |
65 | * insmod samples/livepatch/livepatch-callbacks-mod.ko | |
66 | * insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device | |
67 | * | |
68 | * NOTE: There is a second target module, | |
69 | * livepatch-callbacks-busymod.ko, available for experimenting | |
70 | * with livepatch (un)patch callbacks. This module contains | |
71 | * a 'sleep_secs' parameter that parks the module on one of the | |
72 | * functions that the livepatch demo module wants to patch. | |
73 | * Modifying this value and tweaking the order of module loads can | |
74 | * effectively demonstrate stalled patch transitions: | |
75 | * | |
76 | * # Load a target module, let it park on 'busymod_work_func' for | |
77 | * # thirty seconds | |
78 | * insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30 | |
79 | * | |
80 | * # Meanwhile load the livepatch | |
81 | * insmod samples/livepatch/livepatch-callbacks-demo.ko | |
82 | * | |
83 | * # ... then load and unload another target module while the | |
84 | * # transition is in progress | |
85 | * insmod samples/livepatch/livepatch-callbacks-mod.ko | |
86 | * rmmod samples/livepatch/livepatch-callbacks-mod.ko | |
87 | * | |
88 | * # Finally cleanup | |
89 | * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled | |
90 | * rmmod samples/livepatch/livepatch-callbacks-demo.ko | |
91 | */ | |
92 | ||
93 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
94 | ||
95 | #include <linux/module.h> | |
96 | #include <linux/kernel.h> | |
97 | #include <linux/livepatch.h> | |
98 | ||
99 | static int pre_patch_ret; | |
100 | module_param(pre_patch_ret, int, 0644); | |
101 | MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)"); | |
102 | ||
103 | static const char *const module_state[] = { | |
104 | [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state", | |
105 | [MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init", | |
106 | [MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away", | |
107 | [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up", | |
108 | }; | |
109 | ||
110 | static void callback_info(const char *callback, struct klp_object *obj) | |
111 | { | |
112 | if (obj->mod) | |
113 | pr_info("%s: %s -> %s\n", callback, obj->mod->name, | |
114 | module_state[obj->mod->state]); | |
115 | else | |
116 | pr_info("%s: vmlinux\n", callback); | |
117 | } | |
118 | ||
119 | /* Executed on object patching (ie, patch enablement) */ | |
120 | static int pre_patch_callback(struct klp_object *obj) | |
121 | { | |
122 | callback_info(__func__, obj); | |
123 | return pre_patch_ret; | |
124 | } | |
125 | ||
126 | /* Executed on object unpatching (ie, patch disablement) */ | |
127 | static void post_patch_callback(struct klp_object *obj) | |
128 | { | |
129 | callback_info(__func__, obj); | |
130 | } | |
131 | ||
132 | /* Executed on object unpatching (ie, patch disablement) */ | |
133 | static void pre_unpatch_callback(struct klp_object *obj) | |
134 | { | |
135 | callback_info(__func__, obj); | |
136 | } | |
137 | ||
138 | /* Executed on object unpatching (ie, patch disablement) */ | |
139 | static void post_unpatch_callback(struct klp_object *obj) | |
140 | { | |
141 | callback_info(__func__, obj); | |
142 | } | |
143 | ||
144 | static void patched_work_func(struct work_struct *work) | |
145 | { | |
146 | pr_info("%s\n", __func__); | |
147 | } | |
148 | ||
149 | static struct klp_func no_funcs[] = { | |
150 | { } | |
151 | }; | |
152 | ||
153 | static struct klp_func busymod_funcs[] = { | |
154 | { | |
155 | .old_name = "busymod_work_func", | |
156 | .new_func = patched_work_func, | |
157 | }, { } | |
158 | }; | |
159 | ||
160 | static struct klp_object objs[] = { | |
161 | { | |
162 | .name = NULL, /* vmlinux */ | |
163 | .funcs = no_funcs, | |
164 | .callbacks = { | |
165 | .pre_patch = pre_patch_callback, | |
166 | .post_patch = post_patch_callback, | |
167 | .pre_unpatch = pre_unpatch_callback, | |
168 | .post_unpatch = post_unpatch_callback, | |
169 | }, | |
170 | }, { | |
171 | .name = "livepatch_callbacks_mod", | |
172 | .funcs = no_funcs, | |
173 | .callbacks = { | |
174 | .pre_patch = pre_patch_callback, | |
175 | .post_patch = post_patch_callback, | |
176 | .pre_unpatch = pre_unpatch_callback, | |
177 | .post_unpatch = post_unpatch_callback, | |
178 | }, | |
179 | }, { | |
180 | .name = "livepatch_callbacks_busymod", | |
181 | .funcs = busymod_funcs, | |
182 | .callbacks = { | |
183 | .pre_patch = pre_patch_callback, | |
184 | .post_patch = post_patch_callback, | |
185 | .pre_unpatch = pre_unpatch_callback, | |
186 | .post_unpatch = post_unpatch_callback, | |
187 | }, | |
188 | }, { } | |
189 | }; | |
190 | ||
191 | static struct klp_patch patch = { | |
192 | .mod = THIS_MODULE, | |
193 | .objs = objs, | |
194 | }; | |
195 | ||
196 | static int livepatch_callbacks_demo_init(void) | |
197 | { | |
958ef1e3 | 198 | return klp_enable_patch(&patch); |
93862e38 JL |
199 | } |
200 | ||
201 | static void livepatch_callbacks_demo_exit(void) | |
202 | { | |
93862e38 JL |
203 | } |
204 | ||
205 | module_init(livepatch_callbacks_demo_init); | |
206 | module_exit(livepatch_callbacks_demo_exit); | |
207 | MODULE_LICENSE("GPL"); | |
208 | MODULE_INFO(livepatch, "Y"); |