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#include <linux/list.h>
28
29#if IS_ENABLED(CONFIG_LIVEPATCH)
30
31#include <asm/livepatch.h>
32
33/* task patch states */
34#define KLP_UNDEFINED -1
35#define KLP_UNPATCHED 0
36#define KLP_PATCHED 1
37
38/**
39 * struct klp_func - function structure for live patching
40 * @old_name: name of the function to be patched
41 * @new_func: pointer to the patched function code
42 * @old_sympos: a hint indicating which symbol position the old function
43 * can be found (optional)
44 * @old_func: pointer to the function being patched
45 * @kobj: kobject for sysfs resources
46 * @node: list node for klp_object func_list
47 * @stack_node: list node for klp_ops func_stack list
48 * @old_size: size of the old function
49 * @new_size: size of the new function
50 * @kobj_added: @kobj has been added and needs freeing
51 * @nop: temporary patch to use the original code again; dyn. allocated
52 * @patched: the func has been added to the klp_ops list
53 * @transition: the func is currently being applied or reverted
54 *
55 * The patched and transition variables define the func's patching state. When
56 * patching, a func is always in one of the following states:
57 *
58 * patched=0 transition=0: unpatched
59 * patched=0 transition=1: unpatched, temporary starting state
60 * patched=1 transition=1: patched, may be visible to some tasks
61 * patched=1 transition=0: patched, visible to all tasks
62 *
63 * And when unpatching, it goes in the reverse order:
64 *
65 * patched=1 transition=0: patched, visible to all tasks
66 * patched=1 transition=1: patched, may be visible to some tasks
67 * patched=0 transition=1: unpatched, temporary ending state
68 * patched=0 transition=0: unpatched
69 */
70struct klp_func {
71 /* external */
72 const char *old_name;
73 void *new_func;
74 /*
75 * The old_sympos field is optional and can be used to resolve
76 * duplicate symbol names in livepatch objects. If this field is zero,
77 * it is expected the symbol is unique, otherwise patching fails. If
78 * this value is greater than zero then that occurrence of the symbol
79 * in kallsyms for the given object is used.
80 */
81 unsigned long old_sympos;
82
83 /* internal */
84 void *old_func;
85 struct kobject kobj;
86 struct list_head node;
87 struct list_head stack_node;
88 unsigned long old_size, new_size;
89 bool kobj_added;
90 bool nop;
91 bool patched;
92 bool transition;
93};
94
95struct klp_object;
96
97/**
98 * struct klp_callbacks - pre/post live-(un)patch callback structure
99 * @pre_patch: executed before code patching
100 * @post_patch: executed after code patching
101 * @pre_unpatch: executed before code unpatching
102 * @post_unpatch: executed after code unpatching
103 * @post_unpatch_enabled: flag indicating if post-unpatch callback
104 * should run
105 *
106 * All callbacks are optional. Only the pre-patch callback, if provided,
107 * will be unconditionally executed. If the parent klp_object fails to
108 * patch for any reason, including a non-zero error status returned from
109 * the pre-patch callback, no further callbacks will be executed.
110 */
111struct klp_callbacks {
112 int (*pre_patch)(struct klp_object *obj);
113 void (*post_patch)(struct klp_object *obj);
114 void (*pre_unpatch)(struct klp_object *obj);
115 void (*post_unpatch)(struct klp_object *obj);
116 bool post_unpatch_enabled;
117};
118
119/**
120 * struct klp_object - kernel object structure for live patching
121 * @name: module name (or NULL for vmlinux)
122 * @funcs: function entries for functions to be patched in the object
123 * @callbacks: functions to be executed pre/post (un)patching
124 * @kobj: kobject for sysfs resources
125 * @func_list: dynamic list of the function entries
126 * @node: list node for klp_patch obj_list
127 * @mod: kernel module associated with the patched object
128 * (NULL for vmlinux)
129 * @kobj_added: @kobj has been added and needs freeing
130 * @dynamic: temporary object for nop functions; dynamically allocated
131 * @patched: the object's funcs have been added to the klp_ops list
132 */
133struct klp_object {
134 /* external */
135 const char *name;
136 struct klp_func *funcs;
137 struct klp_callbacks callbacks;
138
139 /* internal */
140 struct kobject kobj;
141 struct list_head func_list;
142 struct list_head node;
143 struct module *mod;
144 bool kobj_added;
145 bool dynamic;
146 bool patched;
147};
148
149/**
150 * struct klp_patch - patch structure for live patching
151 * @mod: reference to the live patch module
152 * @objs: object entries for kernel objects to be patched
153 * @replace: replace all actively used patches
154 * @list: list node for global list of actively used patches
155 * @kobj: kobject for sysfs resources
156 * @obj_list: dynamic list of the object entries
157 * @kobj_added: @kobj has been added and needs freeing
158 * @enabled: the patch is enabled (but operation may be incomplete)
159 * @forced: was involved in a forced transition
160 * @free_work: patch cleanup from workqueue-context
161 * @finish: for waiting till it is safe to remove the patch module
162 */
163struct klp_patch {
164 /* external */
165 struct module *mod;
166 struct klp_object *objs;
167 bool replace;
168
169 /* internal */
170 struct list_head list;
171 struct kobject kobj;
172 struct list_head obj_list;
173 bool kobj_added;
174 bool enabled;
175 bool forced;
176 struct work_struct free_work;
177 struct completion finish;
178};
179
180#define klp_for_each_object_static(patch, obj) \
181 for (obj = patch->objs; obj->funcs || obj->name; obj++)
182
183#define klp_for_each_object_safe(patch, obj, tmp_obj) \
184 list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node)
185
186#define klp_for_each_object(patch, obj) \
187 list_for_each_entry(obj, &patch->obj_list, node)
188
189#define klp_for_each_func_static(obj, func) \
190 for (func = obj->funcs; \
191 func->old_name || func->new_func || func->old_sympos; \
192 func++)
193
194#define klp_for_each_func_safe(obj, func, tmp_func) \
195 list_for_each_entry_safe(func, tmp_func, &obj->func_list, node)
196
197#define klp_for_each_func(obj, func) \
198 list_for_each_entry(func, &obj->func_list, node)
199
200int klp_enable_patch(struct klp_patch *);
201
202void arch_klp_init_object_loaded(struct klp_patch *patch,
203 struct klp_object *obj);
204
205/* Called from the module loader during module coming/going states */
206int klp_module_coming(struct module *mod);
207void klp_module_going(struct module *mod);
208
209void klp_copy_process(struct task_struct *child);
210void klp_update_patch_state(struct task_struct *task);
211
212static inline bool klp_patch_pending(struct task_struct *task)
213{
214 return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
215}
216
217static inline bool klp_have_reliable_stack(void)
218{
219 return IS_ENABLED(CONFIG_STACKTRACE) &&
220 IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
221}
222
223typedef int (*klp_shadow_ctor_t)(void *obj,
224 void *shadow_data,
225 void *ctor_data);
226typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
227
228void *klp_shadow_get(void *obj, unsigned long id);
229void *klp_shadow_alloc(void *obj, unsigned long id,
230 size_t size, gfp_t gfp_flags,
231 klp_shadow_ctor_t ctor, void *ctor_data);
232void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
233 size_t size, gfp_t gfp_flags,
234 klp_shadow_ctor_t ctor, void *ctor_data);
235void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
236void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
237
238#else /* !CONFIG_LIVEPATCH */
239
240static inline int klp_module_coming(struct module *mod) { return 0; }
241static inline void klp_module_going(struct module *mod) {}
242static inline bool klp_patch_pending(struct task_struct *task) { return false; }
243static inline void klp_update_patch_state(struct task_struct *task) {}
244static inline void klp_copy_process(struct task_struct *child) {}
245
246#endif /* CONFIG_LIVEPATCH */
247
248#endif /* _LINUX_LIVEPATCH_H_ */
249