1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
2 | /* |
3 | * livepatch.h - Kernel Live Patching Core |
4 | * |
5 | * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> |
6 | * Copyright (C) 2014 SUSE |
7 | */ |
8 | |
9 | #ifndef _LINUX_LIVEPATCH_H_ |
10 | #define _LINUX_LIVEPATCH_H_ |
11 | |
12 | #include <linux/module.h> |
13 | #include <linux/ftrace.h> |
14 | #include <linux/completion.h> |
15 | #include <linux/list.h> |
16 | |
17 | #if IS_ENABLED(CONFIG_LIVEPATCH) |
18 | |
19 | /* task patch states */ |
20 | #define KLP_UNDEFINED -1 |
21 | #define KLP_UNPATCHED 0 |
22 | #define KLP_PATCHED 1 |
23 | |
24 | /** |
25 | * struct klp_func - function structure for live patching |
26 | * @old_name: name of the function to be patched |
27 | * @new_func: pointer to the patched function code |
28 | * @old_sympos: a hint indicating which symbol position the old function |
29 | * can be found (optional) |
30 | * @old_func: pointer to the function being patched |
31 | * @kobj: kobject for sysfs resources |
32 | * @node: list node for klp_object func_list |
33 | * @stack_node: list node for klp_ops func_stack list |
34 | * @old_size: size of the old function |
35 | * @new_size: size of the new function |
36 | * @nop: temporary patch to use the original code again; dyn. allocated |
37 | * @patched: the func has been added to the klp_ops list |
38 | * @transition: the func is currently being applied or reverted |
39 | * |
40 | * The patched and transition variables define the func's patching state. When |
41 | * patching, a func is always in one of the following states: |
42 | * |
43 | * patched=0 transition=0: unpatched |
44 | * patched=0 transition=1: unpatched, temporary starting state |
45 | * patched=1 transition=1: patched, may be visible to some tasks |
46 | * patched=1 transition=0: patched, visible to all tasks |
47 | * |
48 | * And when unpatching, it goes in the reverse order: |
49 | * |
50 | * patched=1 transition=0: patched, visible to all tasks |
51 | * patched=1 transition=1: patched, may be visible to some tasks |
52 | * patched=0 transition=1: unpatched, temporary ending state |
53 | * patched=0 transition=0: unpatched |
54 | */ |
55 | struct klp_func { |
56 | /* external */ |
57 | const char *old_name; |
58 | void *new_func; |
59 | /* |
60 | * The old_sympos field is optional and can be used to resolve |
61 | * duplicate symbol names in livepatch objects. If this field is zero, |
62 | * it is expected the symbol is unique, otherwise patching fails. If |
63 | * this value is greater than zero then that occurrence of the symbol |
64 | * in kallsyms for the given object is used. |
65 | */ |
66 | unsigned long old_sympos; |
67 | |
68 | /* internal */ |
69 | void *old_func; |
70 | struct kobject kobj; |
71 | struct list_head node; |
72 | struct list_head stack_node; |
73 | unsigned long old_size, new_size; |
74 | bool nop; |
75 | bool patched; |
76 | bool transition; |
77 | }; |
78 | |
79 | struct klp_object; |
80 | |
81 | /** |
82 | * struct klp_callbacks - pre/post live-(un)patch callback structure |
83 | * @pre_patch: executed before code patching |
84 | * @post_patch: executed after code patching |
85 | * @pre_unpatch: executed before code unpatching |
86 | * @post_unpatch: executed after code unpatching |
87 | * @post_unpatch_enabled: flag indicating if post-unpatch callback |
88 | * should run |
89 | * |
90 | * All callbacks are optional. Only the pre-patch callback, if provided, |
91 | * will be unconditionally executed. If the parent klp_object fails to |
92 | * patch for any reason, including a non-zero error status returned from |
93 | * the pre-patch callback, no further callbacks will be executed. |
94 | */ |
95 | struct klp_callbacks { |
96 | int (*pre_patch)(struct klp_object *obj); |
97 | void (*post_patch)(struct klp_object *obj); |
98 | void (*pre_unpatch)(struct klp_object *obj); |
99 | void (*post_unpatch)(struct klp_object *obj); |
100 | bool post_unpatch_enabled; |
101 | }; |
102 | |
103 | /** |
104 | * struct klp_object - kernel object structure for live patching |
105 | * @name: module name (or NULL for vmlinux) |
106 | * @funcs: function entries for functions to be patched in the object |
107 | * @callbacks: functions to be executed pre/post (un)patching |
108 | * @kobj: kobject for sysfs resources |
109 | * @func_list: dynamic list of the function entries |
110 | * @node: list node for klp_patch obj_list |
111 | * @mod: kernel module associated with the patched object |
112 | * (NULL for vmlinux) |
113 | * @dynamic: temporary object for nop functions; dynamically allocated |
114 | * @patched: the object's funcs have been added to the klp_ops list |
115 | */ |
116 | struct klp_object { |
117 | /* external */ |
118 | const char *name; |
119 | struct klp_func *funcs; |
120 | struct klp_callbacks callbacks; |
121 | |
122 | /* internal */ |
123 | struct kobject kobj; |
124 | struct list_head func_list; |
125 | struct list_head node; |
126 | struct module *mod; |
127 | bool dynamic; |
128 | bool patched; |
129 | }; |
130 | |
131 | /** |
132 | * struct klp_state - state of the system modified by the livepatch |
133 | * @id: system state identifier (non-zero) |
134 | * @version: version of the change |
135 | * @data: custom data |
136 | */ |
137 | struct klp_state { |
138 | unsigned long id; |
139 | unsigned int version; |
140 | void *data; |
141 | }; |
142 | |
143 | /** |
144 | * struct klp_patch - patch structure for live patching |
145 | * @mod: reference to the live patch module |
146 | * @objs: object entries for kernel objects to be patched |
147 | * @states: system states that can get modified |
148 | * @replace: replace all actively used patches |
149 | * @list: list node for global list of actively used patches |
150 | * @kobj: kobject for sysfs resources |
151 | * @obj_list: dynamic list of the object entries |
152 | * @enabled: the patch is enabled (but operation may be incomplete) |
153 | * @forced: was involved in a forced transition |
154 | * @free_work: patch cleanup from workqueue-context |
155 | * @finish: for waiting till it is safe to remove the patch module |
156 | */ |
157 | struct klp_patch { |
158 | /* external */ |
159 | struct module *mod; |
160 | struct klp_object *objs; |
161 | struct klp_state *states; |
162 | bool replace; |
163 | |
164 | /* internal */ |
165 | struct list_head list; |
166 | struct kobject kobj; |
167 | struct list_head obj_list; |
168 | bool enabled; |
169 | bool forced; |
170 | struct work_struct free_work; |
171 | struct completion finish; |
172 | }; |
173 | |
174 | #define klp_for_each_object_static(patch, obj) \ |
175 | for (obj = patch->objs; obj->funcs || obj->name; obj++) |
176 | |
177 | #define klp_for_each_object_safe(patch, obj, tmp_obj) \ |
178 | list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node) |
179 | |
180 | #define klp_for_each_object(patch, obj) \ |
181 | list_for_each_entry(obj, &patch->obj_list, node) |
182 | |
183 | #define klp_for_each_func_static(obj, func) \ |
184 | for (func = obj->funcs; \ |
185 | func->old_name || func->new_func || func->old_sympos; \ |
186 | func++) |
187 | |
188 | #define klp_for_each_func_safe(obj, func, tmp_func) \ |
189 | list_for_each_entry_safe(func, tmp_func, &obj->func_list, node) |
190 | |
191 | #define klp_for_each_func(obj, func) \ |
192 | list_for_each_entry(func, &obj->func_list, node) |
193 | |
194 | int klp_enable_patch(struct klp_patch *); |
195 | |
196 | /* Called from the module loader during module coming/going states */ |
197 | int klp_module_coming(struct module *mod); |
198 | void klp_module_going(struct module *mod); |
199 | |
200 | void klp_copy_process(struct task_struct *child); |
201 | void klp_update_patch_state(struct task_struct *task); |
202 | |
203 | static inline bool klp_patch_pending(struct task_struct *task) |
204 | { |
205 | return test_tsk_thread_flag(task, TIF_PATCH_PENDING); |
206 | } |
207 | |
208 | static inline bool klp_have_reliable_stack(void) |
209 | { |
210 | return IS_ENABLED(CONFIG_STACKTRACE) && |
211 | IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE); |
212 | } |
213 | |
214 | typedef int (*klp_shadow_ctor_t)(void *obj, |
215 | void *shadow_data, |
216 | void *ctor_data); |
217 | typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data); |
218 | |
219 | void *klp_shadow_get(void *obj, unsigned long id); |
220 | void *klp_shadow_alloc(void *obj, unsigned long id, |
221 | size_t size, gfp_t gfp_flags, |
222 | klp_shadow_ctor_t ctor, void *ctor_data); |
223 | void *klp_shadow_get_or_alloc(void *obj, unsigned long id, |
224 | size_t size, gfp_t gfp_flags, |
225 | klp_shadow_ctor_t ctor, void *ctor_data); |
226 | void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor); |
227 | void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor); |
228 | |
229 | struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id); |
230 | struct klp_state *klp_get_prev_state(unsigned long id); |
231 | |
232 | int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, |
233 | const char *shstrtab, const char *strtab, |
234 | unsigned int symindex, unsigned int secindex, |
235 | const char *objname); |
236 | |
237 | #else /* !CONFIG_LIVEPATCH */ |
238 | |
239 | static inline int klp_module_coming(struct module *mod) { return 0; } |
240 | static inline void klp_module_going(struct module *mod) {} |
241 | static inline bool klp_patch_pending(struct task_struct *task) { return false; } |
242 | static inline void klp_update_patch_state(struct task_struct *task) {} |
243 | static inline void klp_copy_process(struct task_struct *child) {} |
244 | |
245 | static inline |
246 | int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, |
247 | const char *shstrtab, const char *strtab, |
248 | unsigned int symindex, unsigned int secindex, |
249 | const char *objname) |
250 | { |
251 | return 0; |
252 | } |
253 | |
254 | #endif /* CONFIG_LIVEPATCH */ |
255 | |
256 | #endif /* _LINUX_LIVEPATCH_H_ */ |
257 | |