1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 * livepatch.h - Kernel Live Patching Core 4 * 5 * Copyright (C) 2014 Seth Jennings <[email protected]> 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 * @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 struct klp_object; 82 83 /** 84 * struct klp_callbacks - pre/post live-(un)patch callback structure 85 * @pre_patch: executed before code patching 86 * @post_patch: executed after code patching 87 * @pre_unpatch: executed before code unpatching 88 * @post_unpatch: executed after code unpatching 89 * @post_unpatch_enabled: flag indicating if post-unpatch callback 90 * should run 91 * 92 * All callbacks are optional. Only the pre-patch callback, if provided, 93 * will be unconditionally executed. If the parent klp_object fails to 94 * patch for any reason, including a non-zero error status returned from 95 * the pre-patch callback, no further callbacks will be executed. 96 */ 97 struct klp_callbacks { 98 int (*pre_patch)(struct klp_object *obj); 99 void (*post_patch)(struct klp_object *obj); 100 void (*pre_unpatch)(struct klp_object *obj); 101 void (*post_unpatch)(struct klp_object *obj); 102 bool post_unpatch_enabled; 103 }; 104 105 /** 106 * struct klp_object - kernel object structure for live patching 107 * @name: module name (or NULL for vmlinux) 108 * @funcs: function entries for functions to be patched in the object 109 * @callbacks: functions to be executed pre/post (un)patching 110 * @kobj: kobject for sysfs resources 111 * @func_list: dynamic list of the function entries 112 * @node: list node for klp_patch obj_list 113 * @mod: kernel module associated with the patched object 114 * (NULL for vmlinux) 115 * @dynamic: temporary object for nop functions; dynamically allocated 116 * @patched: the object's funcs have been added to the klp_ops list 117 */ 118 struct klp_object { 119 /* external */ 120 const char *name; 121 struct klp_func *funcs; 122 struct klp_callbacks callbacks; 123 124 /* internal */ 125 struct kobject kobj; 126 struct list_head func_list; 127 struct list_head node; 128 struct module *mod; 129 bool dynamic; 130 bool patched; 131 }; 132 133 /** 134 * struct klp_state - state of the system modified by the livepatch 135 * @id: system state identifier (non-zero) 136 * @data: custom data 137 */ 138 struct klp_state { 139 unsigned long id; 140 void *data; 141 }; 142 143 /** 144 * struct klp_patch - patch structure for live patching 145 * @mod: reference to the live patch module 146 * @objs: object entries for kernel objects to be patched 147 * @states: system states that can get modified 148 * @replace: replace all actively used patches 149 * @list: list node for global list of actively used patches 150 * @kobj: kobject for sysfs resources 151 * @obj_list: dynamic list of the object entries 152 * @enabled: the patch is enabled (but operation may be incomplete) 153 * @forced: was involved in a forced transition 154 * @free_work: patch cleanup from workqueue-context 155 * @finish: for waiting till it is safe to remove the patch module 156 */ 157 struct klp_patch { 158 /* external */ 159 struct module *mod; 160 struct klp_object *objs; 161 struct klp_state *states; 162 bool replace; 163 164 /* internal */ 165 struct list_head list; 166 struct kobject kobj; 167 struct list_head obj_list; 168 bool enabled; 169 bool forced; 170 struct work_struct free_work; 171 struct completion finish; 172 }; 173 174 #define klp_for_each_object_static(patch, obj) \ 175 for (obj = patch->objs; obj->funcs || obj->name; obj++) 176 177 #define klp_for_each_object_safe(patch, obj, tmp_obj) \ 178 list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node) 179 180 #define klp_for_each_object(patch, obj) \ 181 list_for_each_entry(obj, &patch->obj_list, node) 182 183 #define klp_for_each_func_static(obj, func) \ 184 for (func = obj->funcs; \ 185 func->old_name || func->new_func || func->old_sympos; \ 186 func++) 187 188 #define klp_for_each_func_safe(obj, func, tmp_func) \ 189 list_for_each_entry_safe(func, tmp_func, &obj->func_list, node) 190 191 #define klp_for_each_func(obj, func) \ 192 list_for_each_entry(func, &obj->func_list, node) 193 194 int klp_enable_patch(struct klp_patch *); 195 196 void arch_klp_init_object_loaded(struct klp_patch *patch, 197 struct klp_object *obj); 198 199 /* Called from the module loader during module coming/going states */ 200 int klp_module_coming(struct module *mod); 201 void klp_module_going(struct module *mod); 202 203 void klp_copy_process(struct task_struct *child); 204 void klp_update_patch_state(struct task_struct *task); 205 206 static inline bool klp_patch_pending(struct task_struct *task) 207 { 208 return test_tsk_thread_flag(task, TIF_PATCH_PENDING); 209 } 210 211 static inline bool klp_have_reliable_stack(void) 212 { 213 return IS_ENABLED(CONFIG_STACKTRACE) && 214 IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE); 215 } 216 217 typedef int (*klp_shadow_ctor_t)(void *obj, 218 void *shadow_data, 219 void *ctor_data); 220 typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data); 221 222 void *klp_shadow_get(void *obj, unsigned long id); 223 void *klp_shadow_alloc(void *obj, unsigned long id, 224 size_t size, gfp_t gfp_flags, 225 klp_shadow_ctor_t ctor, void *ctor_data); 226 void *klp_shadow_get_or_alloc(void *obj, unsigned long id, 227 size_t size, gfp_t gfp_flags, 228 klp_shadow_ctor_t ctor, void *ctor_data); 229 void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor); 230 void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor); 231 232 struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id); 233 struct klp_state *klp_get_prev_state(unsigned long id); 234 235 #else /* !CONFIG_LIVEPATCH */ 236 237 static inline int klp_module_coming(struct module *mod) { return 0; } 238 static inline void klp_module_going(struct module *mod) {} 239 static inline bool klp_patch_pending(struct task_struct *task) { return false; } 240 static inline void klp_update_patch_state(struct task_struct *task) {} 241 static inline void klp_copy_process(struct task_struct *child) {} 242 243 #endif /* CONFIG_LIVEPATCH */ 244 245 #endif /* _LINUX_LIVEPATCH_H_ */ 246