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 #include <linux/livepatch_external.h>
17 #include <linux/livepatch_sched.h>
18
19 #if IS_ENABLED(CONFIG_LIVEPATCH)
20
21 /* task patch states */
22 #define KLP_TRANSITION_IDLE -1
23 #define KLP_TRANSITION_UNPATCHED 0
24 #define KLP_TRANSITION_PATCHED 1
25
26 /**
27 * struct klp_func - function structure for live patching
28 * @old_name: name of the function to be patched
29 * @new_func: pointer to the patched function code
30 * @old_sympos: a hint indicating which symbol position the old function
31 * can be found (optional)
32 * @old_func: pointer to the function being patched
33 * @kobj: kobject for sysfs resources
34 * @node: list node for klp_object func_list
35 * @stack_node: list node for klp_ops func_stack list
36 * @old_size: size of the old function
37 * @new_size: size of the new function
38 * @nop: temporary patch to use the original code again; dyn. allocated
39 * @patched: the func has been added to the klp_ops list
40 * @transition: the func is currently being applied or reverted
41 *
42 * The patched and transition variables define the func's patching state. When
43 * patching, a func is always in one of the following states:
44 *
45 * patched=0 transition=0: unpatched
46 * patched=0 transition=1: unpatched, temporary starting state
47 * patched=1 transition=1: patched, may be visible to some tasks
48 * patched=1 transition=0: patched, visible to all tasks
49 *
50 * And when unpatching, it goes in the reverse order:
51 *
52 * patched=1 transition=0: patched, visible to all tasks
53 * patched=1 transition=1: patched, may be visible to some tasks
54 * patched=0 transition=1: unpatched, temporary ending state
55 * patched=0 transition=0: unpatched
56 */
57 struct klp_func {
58 /* external */
59 const char *old_name;
60 void *new_func;
61 /*
62 * The old_sympos field is optional and can be used to resolve
63 * duplicate symbol names in livepatch objects. If this field is zero,
64 * it is expected the symbol is unique, otherwise patching fails. If
65 * this value is greater than zero then that occurrence of the symbol
66 * in kallsyms for the given object is used.
67 */
68 unsigned long old_sympos;
69
70 /* internal */
71 void *old_func;
72 struct kobject kobj;
73 struct list_head node;
74 struct list_head stack_node;
75 unsigned long old_size, new_size;
76 bool nop;
77 bool patched;
78 bool transition;
79 };
80
81 /**
82 * struct klp_object - kernel object structure for live patching
83 * @name: module name (or NULL for vmlinux)
84 * @funcs: function entries for functions to be patched in the object
85 * @callbacks: functions to be executed pre/post (un)patching
86 * @kobj: kobject for sysfs resources
87 * @func_list: dynamic list of the function entries
88 * @node: list node for klp_patch obj_list
89 * @mod: kernel module associated with the patched object
90 * (NULL for vmlinux)
91 * @dynamic: temporary object for nop functions; dynamically allocated
92 * @patched: the object's funcs have been added to the klp_ops list
93 */
94 struct klp_object {
95 /* external */
96 const char *name;
97 struct klp_func *funcs;
98 struct klp_callbacks callbacks;
99
100 /* internal */
101 struct kobject kobj;
102 struct list_head func_list;
103 struct list_head node;
104 struct module *mod;
105 bool dynamic;
106 bool patched;
107 };
108
109 /**
110 * struct klp_state - state of the system modified by the livepatch
111 * @id: system state identifier (non-zero)
112 * @version: version of the change
113 * @data: custom data
114 */
115 struct klp_state {
116 unsigned long id;
117 unsigned int version;
118 void *data;
119 };
120
121 /**
122 * struct klp_patch - patch structure for live patching
123 * @mod: reference to the live patch module
124 * @objs: object entries for kernel objects to be patched
125 * @states: system states that can get modified
126 * @replace: replace all actively used patches
127 * @list: list node for global list of actively used patches
128 * @kobj: kobject for sysfs resources
129 * @obj_list: dynamic list of the object entries
130 * @enabled: the patch is enabled (but operation may be incomplete)
131 * @forced: was involved in a forced transition
132 * @free_work: patch cleanup from workqueue-context
133 * @finish: for waiting till it is safe to remove the patch module
134 */
135 struct klp_patch {
136 /* external */
137 struct module *mod;
138 struct klp_object *objs;
139 struct klp_state *states;
140 bool replace;
141
142 /* internal */
143 struct list_head list;
144 struct kobject kobj;
145 struct list_head obj_list;
146 bool enabled;
147 bool forced;
148 struct work_struct free_work;
149 struct completion finish;
150 };
151
152 #define klp_for_each_object_static(patch, obj) \
153 for (obj = patch->objs; obj->funcs || obj->name; obj++)
154
155 #define klp_for_each_object_safe(patch, obj, tmp_obj) \
156 list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node)
157
158 #define klp_for_each_object(patch, obj) \
159 list_for_each_entry(obj, &patch->obj_list, node)
160
161 #define klp_for_each_func_static(obj, func) \
162 for (func = obj->funcs; \
163 func->old_name || func->new_func || func->old_sympos; \
164 func++)
165
166 #define klp_for_each_func_safe(obj, func, tmp_func) \
167 list_for_each_entry_safe(func, tmp_func, &obj->func_list, node)
168
169 #define klp_for_each_func(obj, func) \
170 list_for_each_entry(func, &obj->func_list, node)
171
172 int klp_enable_patch(struct klp_patch *);
173
174 /* Called from the module loader during module coming/going states */
175 int klp_module_coming(struct module *mod);
176 void klp_module_going(struct module *mod);
177
178 void *klp_find_section_by_name(const struct module *mod, const char *name,
179 size_t *sec_size);
180
181 void klp_copy_process(struct task_struct *child);
182 void klp_update_patch_state(struct task_struct *task);
183
klp_patch_pending(struct task_struct * task)184 static inline bool klp_patch_pending(struct task_struct *task)
185 {
186 return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
187 }
188
klp_have_reliable_stack(void)189 static inline bool klp_have_reliable_stack(void)
190 {
191 return IS_ENABLED(CONFIG_STACKTRACE) &&
192 IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
193 }
194
195 typedef int (*klp_shadow_ctor_t)(void *obj,
196 void *shadow_data,
197 void *ctor_data);
198 typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
199
200 void *klp_shadow_get(void *obj, unsigned long id);
201 void *klp_shadow_alloc(void *obj, unsigned long id,
202 size_t size, gfp_t gfp_flags,
203 klp_shadow_ctor_t ctor, void *ctor_data);
204 void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
205 size_t size, gfp_t gfp_flags,
206 klp_shadow_ctor_t ctor, void *ctor_data);
207 void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
208 void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
209
210 struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id);
211 struct klp_state *klp_get_prev_state(unsigned long id);
212
213 int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
214 const char *shstrtab, const char *strtab,
215 unsigned int symindex, unsigned int secindex,
216 const char *objname);
217
218 #else /* !CONFIG_LIVEPATCH */
219
klp_module_coming(struct module * mod)220 static inline int klp_module_coming(struct module *mod) { return 0; }
klp_module_going(struct module * mod)221 static inline void klp_module_going(struct module *mod) {}
klp_patch_pending(struct task_struct * task)222 static inline bool klp_patch_pending(struct task_struct *task) { return false; }
klp_update_patch_state(struct task_struct * task)223 static inline void klp_update_patch_state(struct task_struct *task) {}
klp_copy_process(struct task_struct * child)224 static inline void klp_copy_process(struct task_struct *child) {}
225
226 static inline
klp_apply_section_relocs(struct module * pmod,Elf_Shdr * sechdrs,const char * shstrtab,const char * strtab,unsigned int symindex,unsigned int secindex,const char * objname)227 int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
228 const char *shstrtab, const char *strtab,
229 unsigned int symindex, unsigned int secindex,
230 const char *objname)
231 {
232 return 0;
233 }
234
235 #endif /* CONFIG_LIVEPATCH */
236
237 #endif /* _LINUX_LIVEPATCH_H_ */
238