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TOMOYO Linux Cross Reference
Linux/include/linux/livepatch.h

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  1 /*
  2  * livepatch.h - Kernel Live Patching Core
  3  *
  4  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
  5  * Copyright (C) 2014 SUSE
  6  *
  7  * This program is free software; you can redistribute it and/or
  8  * modify it under the terms of the GNU General Public License
  9  * as published by the Free Software Foundation; either version 2
 10  * of the License, or (at your option) any later version.
 11  *
 12  * This program is distributed in the hope that it will be useful,
 13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15  * GNU General Public License for more details.
 16  *
 17  * You should have received a copy of the GNU General Public License
 18  * along with this program; if not, see <http://www.gnu.org/licenses/>.
 19  */
 20 
 21 #ifndef _LINUX_LIVEPATCH_H_
 22 #define _LINUX_LIVEPATCH_H_
 23 
 24 #include <linux/module.h>
 25 #include <linux/ftrace.h>
 26 #include <linux/completion.h>
 27 
 28 #if IS_ENABLED(CONFIG_LIVEPATCH)
 29 
 30 #include <asm/livepatch.h>
 31 
 32 /* task patch states */
 33 #define KLP_UNDEFINED   -1
 34 #define KLP_UNPATCHED    0
 35 #define KLP_PATCHED      1
 36 
 37 /**
 38  * struct klp_func - function structure for live patching
 39  * @old_name:   name of the function to be patched
 40  * @new_func:   pointer to the patched function code
 41  * @old_sympos: a hint indicating which symbol position the old function
 42  *              can be found (optional)
 43  * @old_addr:   the address of the function being patched
 44  * @kobj:       kobject for sysfs resources
 45  * @stack_node: list node for klp_ops func_stack list
 46  * @old_size:   size of the old function
 47  * @new_size:   size of the new function
 48  * @patched:    the func has been added to the klp_ops list
 49  * @transition: the func is currently being applied or reverted
 50  *
 51  * The patched and transition variables define the func's patching state.  When
 52  * patching, a func is always in one of the following states:
 53  *
 54  *   patched=0 transition=0: unpatched
 55  *   patched=0 transition=1: unpatched, temporary starting state
 56  *   patched=1 transition=1: patched, may be visible to some tasks
 57  *   patched=1 transition=0: patched, visible to all tasks
 58  *
 59  * And when unpatching, it goes in the reverse order:
 60  *
 61  *   patched=1 transition=0: patched, visible to all tasks
 62  *   patched=1 transition=1: patched, may be visible to some tasks
 63  *   patched=0 transition=1: unpatched, temporary ending state
 64  *   patched=0 transition=0: unpatched
 65  */
 66 struct klp_func {
 67         /* external */
 68         const char *old_name;
 69         void *new_func;
 70         /*
 71          * The old_sympos field is optional and can be used to resolve
 72          * duplicate symbol names in livepatch objects. If this field is zero,
 73          * it is expected the symbol is unique, otherwise patching fails. If
 74          * this value is greater than zero then that occurrence of the symbol
 75          * in kallsyms for the given object is used.
 76          */
 77         unsigned long old_sympos;
 78 
 79         /* internal */
 80         unsigned long old_addr;
 81         struct kobject kobj;
 82         struct list_head stack_node;
 83         unsigned long old_size, new_size;
 84         bool patched;
 85         bool transition;
 86 };
 87 
 88 struct klp_object;
 89 
 90 /**
 91  * struct klp_callbacks - pre/post live-(un)patch callback structure
 92  * @pre_patch:          executed before code patching
 93  * @post_patch:         executed after code patching
 94  * @pre_unpatch:        executed before code unpatching
 95  * @post_unpatch:       executed after code unpatching
 96  * @post_unpatch_enabled:       flag indicating if post-unpatch callback
 97  *                              should run
 98  *
 99  * All callbacks are optional.  Only the pre-patch callback, if provided,
100  * will be unconditionally executed.  If the parent klp_object fails to
101  * patch for any reason, including a non-zero error status returned from
102  * the pre-patch callback, no further callbacks will be executed.
103  */
104 struct klp_callbacks {
105         int (*pre_patch)(struct klp_object *obj);
106         void (*post_patch)(struct klp_object *obj);
107         void (*pre_unpatch)(struct klp_object *obj);
108         void (*post_unpatch)(struct klp_object *obj);
109         bool post_unpatch_enabled;
110 };
111 
112 /**
113  * struct klp_object - kernel object structure for live patching
114  * @name:       module name (or NULL for vmlinux)
115  * @funcs:      function entries for functions to be patched in the object
116  * @callbacks:  functions to be executed pre/post (un)patching
117  * @kobj:       kobject for sysfs resources
118  * @mod:        kernel module associated with the patched object
119  *              (NULL for vmlinux)
120  * @patched:    the object's funcs have been added to the klp_ops list
121  */
122 struct klp_object {
123         /* external */
124         const char *name;
125         struct klp_func *funcs;
126         struct klp_callbacks callbacks;
127 
128         /* internal */
129         struct kobject kobj;
130         struct module *mod;
131         bool patched;
132 };
133 
134 /**
135  * struct klp_patch - patch structure for live patching
136  * @mod:        reference to the live patch module
137  * @objs:       object entries for kernel objects to be patched
138  * @list:       list node for global list of registered patches
139  * @kobj:       kobject for sysfs resources
140  * @enabled:    the patch is enabled (but operation may be incomplete)
141  * @finish:     for waiting till it is safe to remove the patch module
142  */
143 struct klp_patch {
144         /* external */
145         struct module *mod;
146         struct klp_object *objs;
147 
148         /* internal */
149         struct list_head list;
150         struct kobject kobj;
151         bool enabled;
152         struct completion finish;
153 };
154 
155 #define klp_for_each_object(patch, obj) \
156         for (obj = patch->objs; obj->funcs || obj->name; obj++)
157 
158 #define klp_for_each_func(obj, func) \
159         for (func = obj->funcs; \
160              func->old_name || func->new_func || func->old_sympos; \
161              func++)
162 
163 int klp_register_patch(struct klp_patch *);
164 int klp_unregister_patch(struct klp_patch *);
165 int klp_enable_patch(struct klp_patch *);
166 int klp_disable_patch(struct klp_patch *);
167 
168 void arch_klp_init_object_loaded(struct klp_patch *patch,
169                                  struct klp_object *obj);
170 
171 /* Called from the module loader during module coming/going states */
172 int klp_module_coming(struct module *mod);
173 void klp_module_going(struct module *mod);
174 
175 void klp_copy_process(struct task_struct *child);
176 void klp_update_patch_state(struct task_struct *task);
177 
178 static inline bool klp_patch_pending(struct task_struct *task)
179 {
180         return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
181 }
182 
183 static inline bool klp_have_reliable_stack(void)
184 {
185         return IS_ENABLED(CONFIG_STACKTRACE) &&
186                IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
187 }
188 
189 typedef int (*klp_shadow_ctor_t)(void *obj,
190                                  void *shadow_data,
191                                  void *ctor_data);
192 typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
193 
194 void *klp_shadow_get(void *obj, unsigned long id);
195 void *klp_shadow_alloc(void *obj, unsigned long id,
196                        size_t size, gfp_t gfp_flags,
197                        klp_shadow_ctor_t ctor, void *ctor_data);
198 void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
199                               size_t size, gfp_t gfp_flags,
200                               klp_shadow_ctor_t ctor, void *ctor_data);
201 void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
202 void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
203 
204 #else /* !CONFIG_LIVEPATCH */
205 
206 static inline int klp_module_coming(struct module *mod) { return 0; }
207 static inline void klp_module_going(struct module *mod) {}
208 static inline bool klp_patch_pending(struct task_struct *task) { return false; }
209 static inline void klp_update_patch_state(struct task_struct *task) {}
210 static inline void klp_copy_process(struct task_struct *child) {}
211 
212 #endif /* CONFIG_LIVEPATCH */
213 
214 #endif /* _LINUX_LIVEPATCH_H_ */
215 

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