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 #include <linux/livepatch_sched.h>
  17
  18 #if IS_ENABLED(CONFIG_LIVEPATCH)
  19
  20 /* task patch states */
  21 #define KLP_TRANSITION_IDLE             -1
  22 #define KLP_TRANSITION_UNPATCHED         0
  23 #define KLP_TRANSITION_PATCHED           1
  24
  25 /**
  26  * struct klp_func - function structure for live patching
  27  * @old_name:   name of the function to be patched
  28  * @new_func:   pointer to the patched function code
  29  * @old_sympos: a hint indicating which symbol position the old function
  30  *              can be found (optional)
  31  * @old_func:   pointer to the function being patched
  32  * @kobj:       kobject for sysfs resources
  33  * @node:       list node for klp_object func_list
  34  * @stack_node: list node for klp_ops func_stack list
  35  * @old_size:   size of the old function
  36  * @new_size:   size of the new function
  37  * @nop:        temporary patch to use the original code again; dyn. allocated
  38  * @patched:    the func has been added to the klp_ops list
  39  * @transition: the func is currently being applied or reverted
  40  *
  41  * The patched and transition variables define the func's patching state.  When
  42  * patching, a func is always in one of the following states:
  43  *
  44  *   patched=0 transition=0: unpatched
  45  *   patched=0 transition=1: unpatched, temporary starting state
  46  *   patched=1 transition=1: patched, may be visible to some tasks
  47  *   patched=1 transition=0: patched, visible to all tasks
  48  *
  49  * And when unpatching, it goes in the reverse order:
  50  *
  51  *   patched=1 transition=0: patched, visible to all tasks
  52  *   patched=1 transition=1: patched, may be visible to some tasks
  53  *   patched=0 transition=1: unpatched, temporary ending state
  54  *   patched=0 transition=0: unpatched
  55  */
  56 struct klp_func {
  57         /* external */
  58         const char *old_name;
  59         void *new_func;
  60         /*
  61          * The old_sympos field is optional and can be used to resolve
  62          * duplicate symbol names in livepatch objects. If this field is zero,
  63          * it is expected the symbol is unique, otherwise patching fails. If
  64          * this value is greater than zero then that occurrence of the symbol
  65          * in kallsyms for the given object is used.
  66          */
  67         unsigned long old_sympos;
  68
  69         /* internal */
  70         void *old_func;
  71         struct kobject kobj;
  72         struct list_head node;
  73         struct list_head stack_node;
  74         unsigned long old_size, new_size;
  75         bool nop;
  76         bool patched;
  77         bool transition;
  78 };
  79
  80 struct klp_object;
  81
  82 /**
  83  * struct klp_callbacks - pre/post live-(un)patch callback structure
  84  * @pre_patch:          executed before code patching
  85  * @post_patch:         executed after code patching
  86  * @pre_unpatch:        executed before code unpatching
  87  * @post_unpatch:       executed after code unpatching
  88  * @post_unpatch_enabled:       flag indicating if post-unpatch callback
  89  *                              should run
  90  *
  91  * All callbacks are optional.  Only the pre-patch callback, if provided,
  92  * will be unconditionally executed.  If the parent klp_object fails to
  93  * patch for any reason, including a non-zero error status returned from
  94  * the pre-patch callback, no further callbacks will be executed.
  95  */
  96 struct klp_callbacks {
  97         int (*pre_patch)(struct klp_object *obj);
  98         void (*post_patch)(struct klp_object *obj);
  99         void (*pre_unpatch)(struct klp_object *obj);
 100         void (*post_unpatch)(struct klp_object *obj);
 101         bool post_unpatch_enabled;
 102 };
 103
 104 /**
 105  * struct klp_object - kernel object structure for live patching
 106  * @name:       module name (or NULL for vmlinux)
 107  * @funcs:      function entries for functions to be patched in the object
 108  * @callbacks:  functions to be executed pre/post (un)patching
 109  * @kobj:       kobject for sysfs resources
 110  * @func_list:  dynamic list of the function entries
 111  * @node:       list node for klp_patch obj_list
 112  * @mod:        kernel module associated with the patched object
 113  *              (NULL for vmlinux)
 114  * @dynamic:    temporary object for nop functions; dynamically allocated
 115  * @patched:    the object's funcs have been added to the klp_ops list
 116  */
 117 struct klp_object {
 118         /* external */
 119         const char *name;
 120         struct klp_func *funcs;
 121         struct klp_callbacks callbacks;
 122
 123         /* internal */
 124         struct kobject kobj;
 125         struct list_head func_list;
 126         struct list_head node;
 127         struct module *mod;
 128         bool dynamic;
 129         bool patched;
 130 };
 131
 132 /**
 133  * struct klp_state - state of the system modified by the livepatch
 134  * @id:         system state identifier (non-zero)
 135  * @version:    version of the change
 136  * @data:       custom data
 137  */
 138 struct klp_state {
 139         unsigned long id;
 140         unsigned int version;
 141         void *data;
 142 };
 143
 144 /**
 145  * struct klp_patch - patch structure for live patching
 146  * @mod:        reference to the live patch module
 147  * @objs:       object entries for kernel objects to be patched
 148  * @states:     system states that can get modified
 149  * @replace:    replace all actively used patches
 150  * @list:       list node for global list of actively used patches
 151  * @kobj:       kobject for sysfs resources
 152  * @obj_list:   dynamic list of the object entries
 153  * @enabled:    the patch is enabled (but operation may be incomplete)
 154  * @forced:     was involved in a forced transition
 155  * @free_work:  patch cleanup from workqueue-context
 156  * @finish:     for waiting till it is safe to remove the patch module
 157  */
 158 struct klp_patch {
 159         /* external */
 160         struct module *mod;
 161         struct klp_object *objs;
 162         struct klp_state *states;
 163         bool replace;
 164
 165         /* internal */
 166         struct list_head list;
 167         struct kobject kobj;
 168         struct list_head obj_list;
 169         bool enabled;
 170         bool forced;
 171         struct work_struct free_work;
 172         struct completion finish;
 173 };
 174
 175 #define klp_for_each_object_static(patch, obj) \
 176         for (obj = patch->objs; obj->funcs || obj->name; obj++)
 177
 178 #define klp_for_each_object_safe(patch, obj, tmp_obj)           \
 179         list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node)
 180
 181 #define klp_for_each_object(patch, obj) \
 182         list_for_each_entry(obj, &patch->obj_list, node)
 183
 184 #define klp_for_each_func_static(obj, func) \
 185         for (func = obj->funcs; \
 186              func->old_name || func->new_func || func->old_sympos; \
 187              func++)
 188
 189 #define klp_for_each_func_safe(obj, func, tmp_func)                     \
 190         list_for_each_entry_safe(func, tmp_func, &obj->func_list, node)
 191
 192 #define klp_for_each_func(obj, func)    \
 193         list_for_each_entry(func, &obj->func_list, node)
 194
 195 int klp_enable_patch(struct klp_patch *);
 196
 197 /* Called from the module loader during module coming/going states */
 198 int klp_module_coming(struct module *mod);
 199 void klp_module_going(struct module *mod);
 200
 201 void klp_copy_process(struct task_struct *child);
 202 void klp_update_patch_state(struct task_struct *task);
 203
 204 static inline bool klp_patch_pending(struct task_struct *task)
 205 {
 206         return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
 207 }
 208
 209 static inline bool klp_have_reliable_stack(void)
 210 {
 211         return IS_ENABLED(CONFIG_STACKTRACE) &&
 212                IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
 213 }
 214
 215 typedef int (*klp_shadow_ctor_t)(void *obj,
 216                                  void *shadow_data,
 217                                  void *ctor_data);
 218 typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
 219
 220 void *klp_shadow_get(void *obj, unsigned long id);
 221 void *klp_shadow_alloc(void *obj, unsigned long id,
 222                        size_t size, gfp_t gfp_flags,
 223                        klp_shadow_ctor_t ctor, void *ctor_data);
 224 void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
 225                               size_t size, gfp_t gfp_flags,
 226                               klp_shadow_ctor_t ctor, void *ctor_data);
 227 void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
 228 void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
 229
 230 struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id);
 231 struct klp_state *klp_get_prev_state(unsigned long id);
 232
 233 int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
 234                              const char *shstrtab, const char *strtab,
 235                              unsigned int symindex, unsigned int secindex,
 236                              const char *objname);
 237
 238 #else /* !CONFIG_LIVEPATCH */
 239
 240 static inline int klp_module_coming(struct module *mod) { return 0; }
 241 static inline void klp_module_going(struct module *mod) {}
 242 static inline bool klp_patch_pending(struct task_struct *task) { return false; }
 243 static inline void klp_update_patch_state(struct task_struct *task) {}
 244 static inline void klp_copy_process(struct task_struct *child) {}
 245
 246 static inline
 247 int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
 248                              const char *shstrtab, const char *strtab,
 249                              unsigned int symindex, unsigned int secindex,
 250                              const char *objname)
 251 {
 252         return 0;
 253 }
 254
 255 #endif /* CONFIG_LIVEPATCH */
 256
 257 #endif /* _LINUX_LIVEPATCH_H_ */