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