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1ccea77e | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
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2 | /* |
3 | * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> | |
93862e38 JL |
4 | */ |
5 | ||
6 | /* | |
7 | * livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo | |
8 | * | |
9 | * | |
10 | * Purpose | |
11 | * ------- | |
12 | * | |
13 | * Demonstration of registering livepatch (un)patching callbacks. | |
14 | * | |
15 | * | |
16 | * Usage | |
17 | * ----- | |
18 | * | |
19 | * Step 1 - load the simple module | |
20 | * | |
21 | * insmod samples/livepatch/livepatch-callbacks-mod.ko | |
22 | * | |
23 | * | |
24 | * Step 2 - load the demonstration livepatch (with callbacks) | |
25 | * | |
26 | * insmod samples/livepatch/livepatch-callbacks-demo.ko | |
27 | * | |
28 | * | |
29 | * Step 3 - cleanup | |
30 | * | |
31 | * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled | |
32 | * rmmod livepatch_callbacks_demo | |
33 | * rmmod livepatch_callbacks_mod | |
34 | * | |
35 | * Watch dmesg output to see livepatch enablement, callback execution | |
36 | * and patching operations for both vmlinux and module targets. | |
37 | * | |
38 | * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and | |
39 | * livepatch-callbacks-demo.ko to observe what happens when a | |
40 | * target module is loaded after a livepatch with callbacks. | |
41 | * | |
42 | * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch | |
43 | * callback return status. Try setting up a non-zero status | |
44 | * such as -19 (-ENODEV): | |
45 | * | |
46 | * # Load demo livepatch, vmlinux is patched | |
47 | * insmod samples/livepatch/livepatch-callbacks-demo.ko | |
48 | * | |
49 | * # Setup next pre-patch callback to return -ENODEV | |
50 | * echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret | |
51 | * | |
52 | * # Module loader refuses to load the target module | |
53 | * insmod samples/livepatch/livepatch-callbacks-mod.ko | |
54 | * insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device | |
55 | * | |
56 | * NOTE: There is a second target module, | |
57 | * livepatch-callbacks-busymod.ko, available for experimenting | |
58 | * with livepatch (un)patch callbacks. This module contains | |
59 | * a 'sleep_secs' parameter that parks the module on one of the | |
60 | * functions that the livepatch demo module wants to patch. | |
61 | * Modifying this value and tweaking the order of module loads can | |
62 | * effectively demonstrate stalled patch transitions: | |
63 | * | |
64 | * # Load a target module, let it park on 'busymod_work_func' for | |
65 | * # thirty seconds | |
66 | * insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30 | |
67 | * | |
68 | * # Meanwhile load the livepatch | |
69 | * insmod samples/livepatch/livepatch-callbacks-demo.ko | |
70 | * | |
71 | * # ... then load and unload another target module while the | |
72 | * # transition is in progress | |
73 | * insmod samples/livepatch/livepatch-callbacks-mod.ko | |
74 | * rmmod samples/livepatch/livepatch-callbacks-mod.ko | |
75 | * | |
76 | * # Finally cleanup | |
77 | * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled | |
78 | * rmmod samples/livepatch/livepatch-callbacks-demo.ko | |
79 | */ | |
80 | ||
81 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
82 | ||
83 | #include <linux/module.h> | |
84 | #include <linux/kernel.h> | |
85 | #include <linux/livepatch.h> | |
86 | ||
87 | static int pre_patch_ret; | |
88 | module_param(pre_patch_ret, int, 0644); | |
89 | MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)"); | |
90 | ||
91 | static const char *const module_state[] = { | |
92 | [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state", | |
93 | [MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init", | |
94 | [MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away", | |
95 | [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up", | |
96 | }; | |
97 | ||
98 | static void callback_info(const char *callback, struct klp_object *obj) | |
99 | { | |
100 | if (obj->mod) | |
101 | pr_info("%s: %s -> %s\n", callback, obj->mod->name, | |
102 | module_state[obj->mod->state]); | |
103 | else | |
104 | pr_info("%s: vmlinux\n", callback); | |
105 | } | |
106 | ||
107 | /* Executed on object patching (ie, patch enablement) */ | |
108 | static int pre_patch_callback(struct klp_object *obj) | |
109 | { | |
110 | callback_info(__func__, obj); | |
111 | return pre_patch_ret; | |
112 | } | |
113 | ||
114 | /* Executed on object unpatching (ie, patch disablement) */ | |
115 | static void post_patch_callback(struct klp_object *obj) | |
116 | { | |
117 | callback_info(__func__, obj); | |
118 | } | |
119 | ||
120 | /* Executed on object unpatching (ie, patch disablement) */ | |
121 | static void pre_unpatch_callback(struct klp_object *obj) | |
122 | { | |
123 | callback_info(__func__, obj); | |
124 | } | |
125 | ||
126 | /* Executed on object unpatching (ie, patch disablement) */ | |
127 | static void post_unpatch_callback(struct klp_object *obj) | |
128 | { | |
129 | callback_info(__func__, obj); | |
130 | } | |
131 | ||
132 | static void patched_work_func(struct work_struct *work) | |
133 | { | |
134 | pr_info("%s\n", __func__); | |
135 | } | |
136 | ||
137 | static struct klp_func no_funcs[] = { | |
138 | { } | |
139 | }; | |
140 | ||
141 | static struct klp_func busymod_funcs[] = { | |
142 | { | |
143 | .old_name = "busymod_work_func", | |
144 | .new_func = patched_work_func, | |
145 | }, { } | |
146 | }; | |
147 | ||
148 | static struct klp_object objs[] = { | |
149 | { | |
150 | .name = NULL, /* vmlinux */ | |
151 | .funcs = no_funcs, | |
152 | .callbacks = { | |
153 | .pre_patch = pre_patch_callback, | |
154 | .post_patch = post_patch_callback, | |
155 | .pre_unpatch = pre_unpatch_callback, | |
156 | .post_unpatch = post_unpatch_callback, | |
157 | }, | |
158 | }, { | |
159 | .name = "livepatch_callbacks_mod", | |
160 | .funcs = no_funcs, | |
161 | .callbacks = { | |
162 | .pre_patch = pre_patch_callback, | |
163 | .post_patch = post_patch_callback, | |
164 | .pre_unpatch = pre_unpatch_callback, | |
165 | .post_unpatch = post_unpatch_callback, | |
166 | }, | |
167 | }, { | |
168 | .name = "livepatch_callbacks_busymod", | |
169 | .funcs = busymod_funcs, | |
170 | .callbacks = { | |
171 | .pre_patch = pre_patch_callback, | |
172 | .post_patch = post_patch_callback, | |
173 | .pre_unpatch = pre_unpatch_callback, | |
174 | .post_unpatch = post_unpatch_callback, | |
175 | }, | |
176 | }, { } | |
177 | }; | |
178 | ||
179 | static struct klp_patch patch = { | |
180 | .mod = THIS_MODULE, | |
181 | .objs = objs, | |
182 | }; | |
183 | ||
184 | static int livepatch_callbacks_demo_init(void) | |
185 | { | |
958ef1e3 | 186 | return klp_enable_patch(&patch); |
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187 | } |
188 | ||
189 | static void livepatch_callbacks_demo_exit(void) | |
190 | { | |
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191 | } |
192 | ||
193 | module_init(livepatch_callbacks_demo_init); | |
194 | module_exit(livepatch_callbacks_demo_exit); | |
195 | MODULE_LICENSE("GPL"); | |
196 | MODULE_INFO(livepatch, "Y"); |