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 klp_patch_pending(struct task_struct * task)204 static inline bool klp_patch_pending(struct task_struct *task) 205 { 206 return test_tsk_thread_flag(task, TIF_PATCH_PENDING); 207 } 208 klp_have_reliable_stack(void)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 klp_module_coming(struct module * mod)240 static inline int klp_module_coming(struct module *mod) { return 0; } klp_module_going(struct module * mod)241 static inline void klp_module_going(struct module *mod) {} klp_patch_pending(struct task_struct * task)242 static inline bool klp_patch_pending(struct task_struct *task) { return false; } klp_update_patch_state(struct task_struct * task)243 static inline void klp_update_patch_state(struct task_struct *task) {} klp_copy_process(struct task_struct * child)244 static inline void klp_copy_process(struct task_struct *child) {} 245 246 static inline klp_apply_section_relocs(struct module * pmod,Elf_Shdr * sechdrs,const char * shstrtab,const char * strtab,unsigned int symindex,unsigned int secindex,const char * objname)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_ */ 258