livepatch.h

  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 */
 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
 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 */
 94struct 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 */
115struct 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 */
135struct 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
172int klp_enable_patch(struct klp_patch *);
173
174/* Called from the module loader during module coming/going states */
175int klp_module_coming(struct module *mod);
176void klp_module_going(struct module *mod);
177
178void *klp_find_section_by_name(const struct module *mod, const char *name,
179			       size_t *sec_size);
180
181void klp_copy_process(struct task_struct *child);
182void klp_update_patch_state(struct task_struct *task);
183
184static inline bool klp_patch_pending(struct task_struct *task)
185{
186	return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
187}
188
189static inline bool klp_have_reliable_stack(void)
190{
191	return IS_ENABLED(CONFIG_STACKTRACE) &&
192	       IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
193}
194
195typedef int (*klp_shadow_ctor_t)(void *obj,
196				 void *shadow_data,
197				 void *ctor_data);
198typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
199
200void *klp_shadow_get(void *obj, unsigned long id);
201void *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);
204void *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);
207void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
208void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
209
210struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id);
211struct klp_state *klp_get_prev_state(unsigned long id);
212
213int 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
220static inline int klp_module_coming(struct module *mod) { return 0; }
221static inline void klp_module_going(struct module *mod) {}
222static inline bool klp_patch_pending(struct task_struct *task) { return false; }
223static inline void klp_update_patch_state(struct task_struct *task) {}
224static inline void klp_copy_process(struct task_struct *child) {}
225
226static inline
227int 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_ */