1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
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 {
186 return klp_enable_patch(&patch);
187 }
188
189 static void livepatch_callbacks_demo_exit(void)
190 {
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");
197
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