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