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(callback: __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(callback: __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(callback: __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(callback: __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 | |