include/linux/livepatch.h

   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 void *klp_shadow_get(void *obj, unsigned long id);
 190 void *klp_shadow_alloc(void *obj, unsigned long id, void *data,
 191                        size_t size, gfp_t gfp_flags);
 192 void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
 193                               size_t size, gfp_t gfp_flags);
 194 void klp_shadow_free(void *obj, unsigned long id);
 195 void klp_shadow_free_all(unsigned long id);
 196
 197 #else /* !CONFIG_LIVEPATCH */
 198
 199 static inline int klp_module_coming(struct module *mod) { return 0; }
 200 static inline void klp_module_going(struct module *mod) {}
 201 static inline bool klp_patch_pending(struct task_struct *task) { return false; }
 202 static inline void klp_update_patch_state(struct task_struct *task) {}
 203 static inline void klp_copy_process(struct task_struct *child) {}
 204
 205 #endif /* CONFIG_LIVEPATCH */
 206
 207 #endif /* _LINUX_LIVEPATCH_H_ */