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 2 supports migration. */
14#define CONSOLE_LOGLEVEL_STATE_VERSION 2
15
16static 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
23static 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
32static struct klp_patch patch;
33
34static int allocate_loglevel_state(void)
35{
36	struct klp_state *loglevel_state, *prev_loglevel_state;
37
38	prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
39	if (prev_loglevel_state) {
40		pr_info("%s: space to store console_loglevel already allocated\n",
41		__func__);
42		return 0;
43	}
44
45	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
46	if (!loglevel_state)
47		return -EINVAL;
48
49	loglevel_state->data = kzalloc(sizeof(console_loglevel), GFP_KERNEL);
50	if (!loglevel_state->data)
51		return -ENOMEM;
52
53	pr_info("%s: allocating space to store console_loglevel\n",
54		__func__);
55	return 0;
56}
57
58static void fix_console_loglevel(void)
59{
60	struct klp_state *loglevel_state, *prev_loglevel_state;
61
62	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
63	if (!loglevel_state)
64		return;
65
66	prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
67	if (prev_loglevel_state) {
68		pr_info("%s: taking over the console_loglevel change\n",
69		__func__);
70		loglevel_state->data = prev_loglevel_state->data;
71		return;
72	}
73
74	pr_info("%s: fixing console_loglevel\n", __func__);
75	*(int *)loglevel_state->data = console_loglevel;
76	console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
77}
78
79static void restore_console_loglevel(void)
80{
81	struct klp_state *loglevel_state, *prev_loglevel_state;
82
83	prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
84	if (prev_loglevel_state) {
85		pr_info("%s: passing the console_loglevel change back to the old livepatch\n",
86		__func__);
87		return;
88	}
89
90	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
91	if (!loglevel_state)
92		return;
93
94	pr_info("%s: restoring console_loglevel\n", __func__);
95	console_loglevel = *(int *)loglevel_state->data;
96}
97
98static void free_loglevel_state(void)
99{
100	struct klp_state *loglevel_state, *prev_loglevel_state;
101
102	prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
103	if (prev_loglevel_state) {
104		pr_info("%s: keeping space to store console_loglevel\n",
105		__func__);
106		return;
107	}
108
109	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
110	if (!loglevel_state)
111		return;
112
113	pr_info("%s: freeing space for the stored console_loglevel\n",
114		__func__);
115	kfree(loglevel_state->data);
116}
117
118/* Executed on object patching (ie, patch enablement) */
119static int pre_patch_callback(struct klp_object *obj)
120{
121	callback_info(__func__, obj);
122	return allocate_loglevel_state();
123}
124
125/* Executed on object unpatching (ie, patch disablement) */
126static void post_patch_callback(struct klp_object *obj)
127{
128	callback_info(__func__, obj);
129	fix_console_loglevel();
130}
131
132/* Executed on object unpatching (ie, patch disablement) */
133static void pre_unpatch_callback(struct klp_object *obj)
134{
135	callback_info(__func__, obj);
136	restore_console_loglevel();
137}
138
139/* Executed on object unpatching (ie, patch disablement) */
140static void post_unpatch_callback(struct klp_object *obj)
141{
142	callback_info(__func__, obj);
143	free_loglevel_state();
144}
145
146static struct klp_func no_funcs[] = {
147	{}
148};
149
150static struct klp_object objs[] = {
151	{
152		.name = NULL,	/* vmlinux */
153		.funcs = no_funcs,
154		.callbacks = {
155			.pre_patch = pre_patch_callback,
156			.post_patch = post_patch_callback,
157			.pre_unpatch = pre_unpatch_callback,
158			.post_unpatch = post_unpatch_callback,
159		},
160	}, { }
161};
162
163static struct klp_state states[] = {
164	{
165		.id = CONSOLE_LOGLEVEL_STATE,
166		.version = CONSOLE_LOGLEVEL_STATE_VERSION,
167	}, { }
168};
169
170static struct klp_patch patch = {
171	.mod = THIS_MODULE,
172	.objs = objs,
173	.states = states,
174	.replace = true,
175};
176
177static int test_klp_callbacks_demo_init(void)
178{
179	return klp_enable_patch(&patch);
180}
181
182static void test_klp_callbacks_demo_exit(void)
183{
184}
185
186module_init(test_klp_callbacks_demo_init);
187module_exit(test_klp_callbacks_demo_exit);
188MODULE_LICENSE("GPL");
189MODULE_INFO(livepatch, "Y");
190MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>");
191MODULE_DESCRIPTION("Livepatch test: system state modification");
192