1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2019 SUSE
3
4 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
5
6 #include <linux/slab.h>
7 #include <linux/module.h>
8 #include <linux/kernel.h>
9 #include <linux/printk.h>
10 #include <linux/livepatch.h>
11
12 #define CONSOLE_LOGLEVEL_STATE 1
13 /* Version 1 does not support migration. */
14 #define CONSOLE_LOGLEVEL_STATE_VERSION 1
15
16 static const char *const module_state[] = {
17 [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state",
18 [MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init",
19 [MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away",
20 [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up",
21 };
22
23 static void callback_info(const char *callback, struct klp_object *obj)
24 {
25 if (obj->mod)
26 pr_info("%s: %s -> %s\n", callback, obj->mod->name,
27 module_state[obj->mod->state]);
28 else
29 pr_info("%s: vmlinux\n", callback);
30 }
31
32 static struct klp_patch patch;
33
34 static int allocate_loglevel_state(void)
35 {
36 struct klp_state *loglevel_state;
37
38 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
39 if (!loglevel_state)
40 return -EINVAL;
41
42 loglevel_state->data = kzalloc(sizeof(console_loglevel), GFP_KERNEL);
43 if (!loglevel_state->data)
44 return -ENOMEM;
45
46 pr_info("%s: allocating space to store console_loglevel\n",
47 __func__);
48 return 0;
49 }
50
51 static void fix_console_loglevel(void)
52 {
53 struct klp_state *loglevel_state;
54
55 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
56 if (!loglevel_state)
57 return;
58
59 pr_info("%s: fixing console_loglevel\n", __func__);
60 *(int *)loglevel_state->data = console_loglevel;
61 console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
62 }
63
64 static void restore_console_loglevel(void)
65 {
66 struct klp_state *loglevel_state;
67
68 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
69 if (!loglevel_state)
70 return;
71
72 pr_info("%s: restoring console_loglevel\n", __func__);
73 console_loglevel = *(int *)loglevel_state->data;
74 }
75
76 static void free_loglevel_state(void)
77 {
78 struct klp_state *loglevel_state;
79
80 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
81 if (!loglevel_state)
82 return;
83
84 pr_info("%s: freeing space for the stored console_loglevel\n",
85 __func__);
86 kfree(loglevel_state->data);
87 }
88
89 /* Executed on object patching (ie, patch enablement) */
90 static int pre_patch_callback(struct klp_object *obj)
91 {
92 callback_info(__func__, obj);
93 return allocate_loglevel_state();
94 }
95
96 /* Executed on object unpatching (ie, patch disablement) */
97 static void post_patch_callback(struct klp_object *obj)
98 {
99 callback_info(__func__, obj);
100 fix_console_loglevel();
101 }
102
103 /* Executed on object unpatching (ie, patch disablement) */
104 static void pre_unpatch_callback(struct klp_object *obj)
105 {
106 callback_info(__func__, obj);
107 restore_console_loglevel();
108 }
109
110 /* Executed on object unpatching (ie, patch disablement) */
111 static void post_unpatch_callback(struct klp_object *obj)
112 {
113 callback_info(__func__, obj);
114 free_loglevel_state();
115 }
116
117 static struct klp_func no_funcs[] = {
118 {}
119 };
120
121 static struct klp_object objs[] = {
122 {
123 .name = NULL, /* vmlinux */
124 .funcs = no_funcs,
125 .callbacks = {
126 .pre_patch = pre_patch_callback,
127 .post_patch = post_patch_callback,
128 .pre_unpatch = pre_unpatch_callback,
129 .post_unpatch = post_unpatch_callback,
130 },
131 }, { }
132 };
133
134 static struct klp_state states[] = {
135 {
136 .id = CONSOLE_LOGLEVEL_STATE,
137 .version = CONSOLE_LOGLEVEL_STATE_VERSION,
138 }, { }
139 };
140
141 static struct klp_patch patch = {
142 .mod = THIS_MODULE,
143 .objs = objs,
144 .states = states,
145 .replace = true,
146 };
147
148 static int test_klp_callbacks_demo_init(void)
149 {
150 return klp_enable_patch(&patch);
151 }
152
153 static void test_klp_callbacks_demo_exit(void)
154 {
155 }
156
157 module_init(test_klp_callbacks_demo_init);
158 module_exit(test_klp_callbacks_demo_exit);
159 MODULE_LICENSE("GPL");
160 MODULE_INFO(livepatch, "Y");
161 MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>");
162 MODULE_DESCRIPTION("Livepatch test: system state modification");
163
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