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
87static int pre_patch_ret;
88module_param(pre_patch_ret, int, 0644);
89MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)");
90
91static 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
98static 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) */
108static 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) */
115static void post_patch_callback(struct klp_object *obj)
116{
117	callback_info(__func__, obj);
118}
119
120/* Executed on object unpatching (ie, patch disablement) */
121static void pre_unpatch_callback(struct klp_object *obj)
122{
123	callback_info(__func__, obj);
124}
125
126/* Executed on object unpatching (ie, patch disablement) */
127static void post_unpatch_callback(struct klp_object *obj)
128{
129	callback_info(__func__, obj);
130}
131
132static void patched_work_func(struct work_struct *work)
133{
134	pr_info("%s\n", __func__);
135}
136
137static struct klp_func no_funcs[] = {
138	{ }
139};
140
141static struct klp_func busymod_funcs[] = {
142	{
143		.old_name = "busymod_work_func",
144		.new_func = patched_work_func,
145	}, { }
146};
147
148static 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
179static struct klp_patch patch = {
180	.mod = THIS_MODULE,
181	.objs = objs,
182};
183
184static int livepatch_callbacks_demo_init(void)
185{
186	return klp_enable_patch(&patch);
187}
188
189static void livepatch_callbacks_demo_exit(void)
190{
191}
192
193module_init(livepatch_callbacks_demo_init);
194module_exit(livepatch_callbacks_demo_exit);
195MODULE_LICENSE("GPL");
196MODULE_INFO(livepatch, "Y");
197