Linux kernel mirror (for testing)
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linux
1/*
2 * livepatch.h - Kernel Live Patching Core
3 *
4 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
5 * Copyright (C) 2014 SUSE
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2
10 * of the License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, see <http://www.gnu.org/licenses/>.
19 */
20
21#ifndef _LINUX_LIVEPATCH_H_
22#define _LINUX_LIVEPATCH_H_
23
24#include <linux/module.h>
25#include <linux/ftrace.h>
26#include <linux/completion.h>
27
28#if IS_ENABLED(CONFIG_LIVEPATCH)
29
30#include <asm/livepatch.h>
31
32/* task patch states */
33#define KLP_UNDEFINED -1
34#define KLP_UNPATCHED 0
35#define KLP_PATCHED 1
36
37/**
38 * struct klp_func - function structure for live patching
39 * @old_name: name of the function to be patched
40 * @new_func: pointer to the patched function code
41 * @old_sympos: a hint indicating which symbol position the old function
42 * can be found (optional)
43 * @immediate: patch the func immediately, bypassing safety mechanisms
44 * @old_addr: the address of the function being patched
45 * @kobj: kobject for sysfs resources
46 * @stack_node: list node for klp_ops func_stack list
47 * @old_size: size of the old function
48 * @new_size: size of the new function
49 * @patched: the func has been added to the klp_ops list
50 * @transition: the func is currently being applied or reverted
51 *
52 * The patched and transition variables define the func's patching state. When
53 * patching, a func is always in one of the following states:
54 *
55 * patched=0 transition=0: unpatched
56 * patched=0 transition=1: unpatched, temporary starting state
57 * patched=1 transition=1: patched, may be visible to some tasks
58 * patched=1 transition=0: patched, visible to all tasks
59 *
60 * And when unpatching, it goes in the reverse order:
61 *
62 * patched=1 transition=0: patched, visible to all tasks
63 * patched=1 transition=1: patched, may be visible to some tasks
64 * patched=0 transition=1: unpatched, temporary ending state
65 * patched=0 transition=0: unpatched
66 */
67struct klp_func {
68 /* external */
69 const char *old_name;
70 void *new_func;
71 /*
72 * The old_sympos field is optional and can be used to resolve
73 * duplicate symbol names in livepatch objects. If this field is zero,
74 * it is expected the symbol is unique, otherwise patching fails. If
75 * this value is greater than zero then that occurrence of the symbol
76 * in kallsyms for the given object is used.
77 */
78 unsigned long old_sympos;
79 bool immediate;
80
81 /* internal */
82 unsigned long old_addr;
83 struct kobject kobj;
84 struct list_head stack_node;
85 unsigned long old_size, new_size;
86 bool patched;
87 bool transition;
88};
89
90struct klp_object;
91
92/**
93 * struct klp_callbacks - pre/post live-(un)patch callback structure
94 * @pre_patch: executed before code patching
95 * @post_patch: executed after code patching
96 * @pre_unpatch: executed before code unpatching
97 * @post_unpatch: executed after code unpatching
98 * @post_unpatch_enabled: flag indicating if post-unpatch callback
99 * should run
100 *
101 * All callbacks are optional. Only the pre-patch callback, if provided,
102 * will be unconditionally executed. If the parent klp_object fails to
103 * patch for any reason, including a non-zero error status returned from
104 * the pre-patch callback, no further callbacks will be executed.
105 */
106struct klp_callbacks {
107 int (*pre_patch)(struct klp_object *obj);
108 void (*post_patch)(struct klp_object *obj);
109 void (*pre_unpatch)(struct klp_object *obj);
110 void (*post_unpatch)(struct klp_object *obj);
111 bool post_unpatch_enabled;
112};
113
114/**
115 * struct klp_object - kernel object structure for live patching
116 * @name: module name (or NULL for vmlinux)
117 * @funcs: function entries for functions to be patched in the object
118 * @callbacks: functions to be executed pre/post (un)patching
119 * @kobj: kobject for sysfs resources
120 * @mod: kernel module associated with the patched object
121 * (NULL for vmlinux)
122 * @patched: the object's funcs have been added to the klp_ops list
123 */
124struct klp_object {
125 /* external */
126 const char *name;
127 struct klp_func *funcs;
128 struct klp_callbacks callbacks;
129
130 /* internal */
131 struct kobject kobj;
132 struct module *mod;
133 bool patched;
134};
135
136/**
137 * struct klp_patch - patch structure for live patching
138 * @mod: reference to the live patch module
139 * @objs: object entries for kernel objects to be patched
140 * @immediate: patch all funcs immediately, bypassing safety mechanisms
141 * @list: list node for global list of registered patches
142 * @kobj: kobject for sysfs resources
143 * @enabled: the patch is enabled (but operation may be incomplete)
144 * @finish: for waiting till it is safe to remove the patch module
145 */
146struct klp_patch {
147 /* external */
148 struct module *mod;
149 struct klp_object *objs;
150 bool immediate;
151
152 /* internal */
153 struct list_head list;
154 struct kobject kobj;
155 bool enabled;
156 struct completion finish;
157};
158
159#define klp_for_each_object(patch, obj) \
160 for (obj = patch->objs; obj->funcs || obj->name; obj++)
161
162#define klp_for_each_func(obj, func) \
163 for (func = obj->funcs; \
164 func->old_name || func->new_func || func->old_sympos; \
165 func++)
166
167int klp_register_patch(struct klp_patch *);
168int klp_unregister_patch(struct klp_patch *);
169int klp_enable_patch(struct klp_patch *);
170int klp_disable_patch(struct klp_patch *);
171
172void arch_klp_init_object_loaded(struct klp_patch *patch,
173 struct klp_object *obj);
174
175/* Called from the module loader during module coming/going states */
176int klp_module_coming(struct module *mod);
177void klp_module_going(struct module *mod);
178
179void klp_copy_process(struct task_struct *child);
180void klp_update_patch_state(struct task_struct *task);
181
182static inline bool klp_patch_pending(struct task_struct *task)
183{
184 return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
185}
186
187static inline bool klp_have_reliable_stack(void)
188{
189 return IS_ENABLED(CONFIG_STACKTRACE) &&
190 IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
191}
192
193void *klp_shadow_get(void *obj, unsigned long id);
194void *klp_shadow_alloc(void *obj, unsigned long id, void *data,
195 size_t size, gfp_t gfp_flags);
196void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
197 size_t size, gfp_t gfp_flags);
198void klp_shadow_free(void *obj, unsigned long id);
199void klp_shadow_free_all(unsigned long id);
200
201#else /* !CONFIG_LIVEPATCH */
202
203static inline int klp_module_coming(struct module *mod) { return 0; }
204static inline void klp_module_going(struct module *mod) {}
205static inline bool klp_patch_pending(struct task_struct *task) { return false; }
206static inline void klp_update_patch_state(struct task_struct *task) {}
207static inline void klp_copy_process(struct task_struct *child) {}
208
209#endif /* CONFIG_LIVEPATCH */
210
211#endif /* _LINUX_LIVEPATCH_H_ */