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#include <asm/livepatch.h>
 20
 21/* task patch states */
 22#define KLP_UNDEFINED	-1
 23#define KLP_UNPATCHED	 0
 24#define KLP_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 */
 57struct 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
 81struct klp_object;
 82
 83/**
 84 * struct klp_callbacks - pre/post live-(un)patch callback structure
 85 * @pre_patch:		executed before code patching
 86 * @post_patch:		executed after code patching
 87 * @pre_unpatch:	executed before code unpatching
 88 * @post_unpatch:	executed after code unpatching
 89 * @post_unpatch_enabled:	flag indicating if post-unpatch callback
 90 * 				should run
 91 *
 92 * All callbacks are optional.  Only the pre-patch callback, if provided,
 93 * will be unconditionally executed.  If the parent klp_object fails to
 94 * patch for any reason, including a non-zero error status returned from
 95 * the pre-patch callback, no further callbacks will be executed.
 96 */
 97struct klp_callbacks {
 98	int (*pre_patch)(struct klp_object *obj);
 99	void (*post_patch)(struct klp_object *obj);
100	void (*pre_unpatch)(struct klp_object *obj);
101	void (*post_unpatch)(struct klp_object *obj);
102	bool post_unpatch_enabled;
103};
104
105/**
106 * struct klp_object - kernel object structure for live patching
107 * @name:	module name (or NULL for vmlinux)
108 * @funcs:	function entries for functions to be patched in the object
109 * @callbacks:	functions to be executed pre/post (un)patching
110 * @kobj:	kobject for sysfs resources
111 * @func_list:	dynamic list of the function entries
112 * @node:	list node for klp_patch obj_list
113 * @mod:	kernel module associated with the patched object
114 *		(NULL for vmlinux)
115 * @dynamic:    temporary object for nop functions; dynamically allocated
116 * @patched:	the object's funcs have been added to the klp_ops list
117 */
118struct klp_object {
119	/* external */
120	const char *name;
121	struct klp_func *funcs;
122	struct klp_callbacks callbacks;
123
124	/* internal */
125	struct kobject kobj;
126	struct list_head func_list;
127	struct list_head node;
128	struct module *mod;
129	bool dynamic;
130	bool patched;
131};
132
133/**
134 * struct klp_state - state of the system modified by the livepatch
135 * @id:		system state identifier (non-zero)
136 * @version:	version of the change
137 * @data:	custom data
138 */
139struct klp_state {
140	unsigned long id;
141	unsigned int version;
142	void *data;
143};
144
145/**
146 * struct klp_patch - patch structure for live patching
147 * @mod:	reference to the live patch module
148 * @objs:	object entries for kernel objects to be patched
149 * @states:	system states that can get modified
150 * @replace:	replace all actively used patches
151 * @list:	list node for global list of actively used patches
152 * @kobj:	kobject for sysfs resources
153 * @obj_list:	dynamic list of the object entries
154 * @enabled:	the patch is enabled (but operation may be incomplete)
155 * @forced:	was involved in a forced transition
156 * @free_work:	patch cleanup from workqueue-context
157 * @finish:	for waiting till it is safe to remove the patch module
158 */
159struct klp_patch {
160	/* external */
161	struct module *mod;
162	struct klp_object *objs;
163	struct klp_state *states;
164	bool replace;
165
166	/* internal */
167	struct list_head list;
168	struct kobject kobj;
169	struct list_head obj_list;
170	bool enabled;
171	bool forced;
172	struct work_struct free_work;
173	struct completion finish;
174};
175
176#define klp_for_each_object_static(patch, obj) \
177	for (obj = patch->objs; obj->funcs || obj->name; obj++)
178
179#define klp_for_each_object_safe(patch, obj, tmp_obj)		\
180	list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node)
181
182#define klp_for_each_object(patch, obj)	\
183	list_for_each_entry(obj, &patch->obj_list, node)
184
185#define klp_for_each_func_static(obj, func) \
186	for (func = obj->funcs; \
187	     func->old_name || func->new_func || func->old_sympos; \
188	     func++)
189
190#define klp_for_each_func_safe(obj, func, tmp_func)			\
191	list_for_each_entry_safe(func, tmp_func, &obj->func_list, node)
192
193#define klp_for_each_func(obj, func)	\
194	list_for_each_entry(func, &obj->func_list, node)
195
196int klp_enable_patch(struct klp_patch *);
197
198/* Called from the module loader during module coming/going states */
199int klp_module_coming(struct module *mod);
200void klp_module_going(struct module *mod);
201
202void klp_copy_process(struct task_struct *child);
203void klp_update_patch_state(struct task_struct *task);
204
205static inline bool klp_patch_pending(struct task_struct *task)
206{
207	return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
208}
209
210static inline bool klp_have_reliable_stack(void)
211{
212	return IS_ENABLED(CONFIG_STACKTRACE) &&
213	       IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
214}
215
216typedef int (*klp_shadow_ctor_t)(void *obj,
217				 void *shadow_data,
218				 void *ctor_data);
219typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
220
221void *klp_shadow_get(void *obj, unsigned long id);
222void *klp_shadow_alloc(void *obj, unsigned long id,
223		       size_t size, gfp_t gfp_flags,
224		       klp_shadow_ctor_t ctor, void *ctor_data);
225void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
226			      size_t size, gfp_t gfp_flags,
227			      klp_shadow_ctor_t ctor, void *ctor_data);
228void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
229void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
230
231struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id);
232struct klp_state *klp_get_prev_state(unsigned long id);
233
234int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
235			     const char *shstrtab, const char *strtab,
236			     unsigned int symindex, unsigned int secindex,
237			     const char *objname);
238
239#else /* !CONFIG_LIVEPATCH */
240
241static inline int klp_module_coming(struct module *mod) { return 0; }
242static inline void klp_module_going(struct module *mod) {}
243static inline bool klp_patch_pending(struct task_struct *task) { return false; }
244static inline void klp_update_patch_state(struct task_struct *task) {}
245static inline void klp_copy_process(struct task_struct *child) {}
246
247static inline
248int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
249			     const char *shstrtab, const char *strtab,
250			     unsigned int symindex, unsigned int secindex,
251			     const char *objname)
252{
253	return 0;
254}
255
256#endif /* CONFIG_LIVEPATCH */
257
258#endif /* _LINUX_LIVEPATCH_H_ */