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_sched.h>
17
18#if IS_ENABLED(CONFIG_LIVEPATCH)
19
20/* task patch states */
21#define KLP_UNDEFINED	-1
22#define KLP_UNPATCHED	 0
23#define KLP_PATCHED	 1
24
25/**
26 * struct klp_func - function structure for live patching
27 * @old_name:	name of the function to be patched
28 * @new_func:	pointer to the patched function code
29 * @old_sympos: a hint indicating which symbol position the old function
30 *		can be found (optional)
31 * @old_func:	pointer to the function being patched
32 * @kobj:	kobject for sysfs resources
33 * @node:	list node for klp_object func_list
34 * @stack_node:	list node for klp_ops func_stack list
35 * @old_size:	size of the old function
36 * @new_size:	size of the new function
37 * @nop:        temporary patch to use the original code again; dyn. allocated
38 * @patched:	the func has been added to the klp_ops list
39 * @transition:	the func is currently being applied or reverted
40 *
41 * The patched and transition variables define the func's patching state.  When
42 * patching, a func is always in one of the following states:
43 *
44 *   patched=0 transition=0: unpatched
45 *   patched=0 transition=1: unpatched, temporary starting state
46 *   patched=1 transition=1: patched, may be visible to some tasks
47 *   patched=1 transition=0: patched, visible to all tasks
48 *
49 * And when unpatching, it goes in the reverse order:
50 *
51 *   patched=1 transition=0: patched, visible to all tasks
52 *   patched=1 transition=1: patched, may be visible to some tasks
53 *   patched=0 transition=1: unpatched, temporary ending state
54 *   patched=0 transition=0: unpatched
55 */
56struct klp_func {
57	/* external */
58	const char *old_name;
59	void *new_func;
60	/*
61	 * The old_sympos field is optional and can be used to resolve
62	 * duplicate symbol names in livepatch objects. If this field is zero,
63	 * it is expected the symbol is unique, otherwise patching fails. If
64	 * this value is greater than zero then that occurrence of the symbol
65	 * in kallsyms for the given object is used.
66	 */
67	unsigned long old_sympos;
68
69	/* internal */
70	void *old_func;
71	struct kobject kobj;
72	struct list_head node;
73	struct list_head stack_node;
74	unsigned long old_size, new_size;
75	bool nop;
76	bool patched;
77	bool transition;
78};
79
80struct klp_object;
81
82/**
83 * struct klp_callbacks - pre/post live-(un)patch callback structure
84 * @pre_patch:		executed before code patching
85 * @post_patch:		executed after code patching
86 * @pre_unpatch:	executed before code unpatching
87 * @post_unpatch:	executed after code unpatching
88 * @post_unpatch_enabled:	flag indicating if post-unpatch callback
89 * 				should run
90 *
91 * All callbacks are optional.  Only the pre-patch callback, if provided,
92 * will be unconditionally executed.  If the parent klp_object fails to
93 * patch for any reason, including a non-zero error status returned from
94 * the pre-patch callback, no further callbacks will be executed.
95 */
96struct klp_callbacks {
97	int (*pre_patch)(struct klp_object *obj);
98	void (*post_patch)(struct klp_object *obj);
99	void (*pre_unpatch)(struct klp_object *obj);
100	void (*post_unpatch)(struct klp_object *obj);
101	bool post_unpatch_enabled;
102};
103
104/**
105 * struct klp_object - kernel object structure for live patching
106 * @name:	module name (or NULL for vmlinux)
107 * @funcs:	function entries for functions to be patched in the object
108 * @callbacks:	functions to be executed pre/post (un)patching
109 * @kobj:	kobject for sysfs resources
110 * @func_list:	dynamic list of the function entries
111 * @node:	list node for klp_patch obj_list
112 * @mod:	kernel module associated with the patched object
113 *		(NULL for vmlinux)
114 * @dynamic:    temporary object for nop functions; dynamically allocated
115 * @patched:	the object's funcs have been added to the klp_ops list
116 */
117struct klp_object {
118	/* external */
119	const char *name;
120	struct klp_func *funcs;
121	struct klp_callbacks callbacks;
122
123	/* internal */
124	struct kobject kobj;
125	struct list_head func_list;
126	struct list_head node;
127	struct module *mod;
128	bool dynamic;
129	bool patched;
130};
131
132/**
133 * struct klp_state - state of the system modified by the livepatch
134 * @id:		system state identifier (non-zero)
135 * @version:	version of the change
136 * @data:	custom data
137 */
138struct klp_state {
139	unsigned long id;
140	unsigned int version;
141	void *data;
142};
143
144/**
145 * struct klp_patch - patch structure for live patching
146 * @mod:	reference to the live patch module
147 * @objs:	object entries for kernel objects to be patched
148 * @states:	system states that can get modified
149 * @replace:	replace all actively used patches
150 * @list:	list node for global list of actively used patches
151 * @kobj:	kobject for sysfs resources
152 * @obj_list:	dynamic list of the object entries
153 * @enabled:	the patch is enabled (but operation may be incomplete)
154 * @forced:	was involved in a forced transition
155 * @free_work:	patch cleanup from workqueue-context
156 * @finish:	for waiting till it is safe to remove the patch module
157 */
158struct klp_patch {
159	/* external */
160	struct module *mod;
161	struct klp_object *objs;
162	struct klp_state *states;
163	bool replace;
164
165	/* internal */
166	struct list_head list;
167	struct kobject kobj;
168	struct list_head obj_list;
169	bool enabled;
170	bool forced;
171	struct work_struct free_work;
172	struct completion finish;
173};
174
175#define klp_for_each_object_static(patch, obj) \
176	for (obj = patch->objs; obj->funcs || obj->name; obj++)
177
178#define klp_for_each_object_safe(patch, obj, tmp_obj)		\
179	list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node)
180
181#define klp_for_each_object(patch, obj)	\
182	list_for_each_entry(obj, &patch->obj_list, node)
183
184#define klp_for_each_func_static(obj, func) \
185	for (func = obj->funcs; \
186	     func->old_name || func->new_func || func->old_sympos; \
187	     func++)
188
189#define klp_for_each_func_safe(obj, func, tmp_func)			\
190	list_for_each_entry_safe(func, tmp_func, &obj->func_list, node)
191
192#define klp_for_each_func(obj, func)	\
193	list_for_each_entry(func, &obj->func_list, node)
194
195int klp_enable_patch(struct klp_patch *);
196
197/* Called from the module loader during module coming/going states */
198int klp_module_coming(struct module *mod);
199void klp_module_going(struct module *mod);
200
201void klp_copy_process(struct task_struct *child);
202void klp_update_patch_state(struct task_struct *task);
203
204static inline bool klp_patch_pending(struct task_struct *task)
205{
206	return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
207}
208
209static inline bool klp_have_reliable_stack(void)
210{
211	return IS_ENABLED(CONFIG_STACKTRACE) &&
212	       IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
213}
214
215typedef int (*klp_shadow_ctor_t)(void *obj,
216				 void *shadow_data,
217				 void *ctor_data);
218typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
219
220void *klp_shadow_get(void *obj, unsigned long id);
221void *klp_shadow_alloc(void *obj, unsigned long id,
222		       size_t size, gfp_t gfp_flags,
223		       klp_shadow_ctor_t ctor, void *ctor_data);
224void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
225			      size_t size, gfp_t gfp_flags,
226			      klp_shadow_ctor_t ctor, void *ctor_data);
227void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
228void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
229
230struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id);
231struct klp_state *klp_get_prev_state(unsigned long id);
232
233int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
234			     const char *shstrtab, const char *strtab,
235			     unsigned int symindex, unsigned int secindex,
236			     const char *objname);
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
246static inline
247int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
248			     const char *shstrtab, const char *strtab,
249			     unsigned int symindex, unsigned int secindex,
250			     const char *objname)
251{
252	return 0;
253}
254
255#endif /* CONFIG_LIVEPATCH */
256
257#endif /* _LINUX_LIVEPATCH_H_ */
258