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
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;
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
51static 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
64static 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
76static 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) */
90static 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) */
97static 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) */
104static 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) */
111static void post_unpatch_callback(struct klp_object *obj)
112{
113	callback_info(__func__, obj);
114	free_loglevel_state();
115}
116
117static struct klp_func no_funcs[] = {
118	{}
119};
120
121static 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
134static struct klp_state states[] = {
135	{
136		.id = CONSOLE_LOGLEVEL_STATE,
137		.version = CONSOLE_LOGLEVEL_STATE_VERSION,
138	}, { }
139};
140
141static struct klp_patch patch = {
142	.mod = THIS_MODULE,
143	.objs = objs,
144	.states = states,
145	.replace = true,
146};
147
148static int test_klp_callbacks_demo_init(void)
149{
150	return klp_enable_patch(&patch);
151}
152
153static void test_klp_callbacks_demo_exit(void)
154{
155}
156
157module_init(test_klp_callbacks_demo_init);
158module_exit(test_klp_callbacks_demo_exit);
159MODULE_LICENSE("GPL");
160MODULE_INFO(livepatch, "Y");
161MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>");
162MODULE_DESCRIPTION("Livepatch test: system state modification");
163