| 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 | /* task patch states */ |
| 20 | #define KLP_UNDEFINED -1 |
| 21 | #define KLP_UNPATCHED 0 |
| 22 | #define KLP_PATCHED 1 |
| 23 | |
| 24 | /** |
| 25 | * struct klp_func - function structure for live patching |
| 26 | * @old_name: name of the function to be patched |
| 27 | * @new_func: pointer to the patched function code |
| 28 | * @old_sympos: a hint indicating which symbol position the old function |
| 29 | * can be found (optional) |
| 30 | * @old_func: pointer to the function being patched |
| 31 | * @kobj: kobject for sysfs resources |
| 32 | * @node: list node for klp_object func_list |
| 33 | * @stack_node: list node for klp_ops func_stack list |
| 34 | * @old_size: size of the old function |
| 35 | * @new_size: size of the new function |
| 36 | * @nop: temporary patch to use the original code again; dyn. allocated |
| 37 | * @patched: the func has been added to the klp_ops list |
| 38 | * @transition: the func is currently being applied or reverted |
| 39 | * |
| 40 | * The patched and transition variables define the func's patching state. When |
| 41 | * patching, a func is always in one of the following states: |
| 42 | * |
| 43 | * patched=0 transition=0: unpatched |
| 44 | * patched=0 transition=1: unpatched, temporary starting state |
| 45 | * patched=1 transition=1: patched, may be visible to some tasks |
| 46 | * patched=1 transition=0: patched, visible to all tasks |
| 47 | * |
| 48 | * And when unpatching, it goes in the reverse order: |
| 49 | * |
| 50 | * patched=1 transition=0: patched, visible to all tasks |
| 51 | * patched=1 transition=1: patched, may be visible to some tasks |
| 52 | * patched=0 transition=1: unpatched, temporary ending state |
| 53 | * patched=0 transition=0: unpatched |
| 54 | */ |
| 55 | struct klp_func { |
| 56 | /* external */ |
| 57 | const char *old_name; |
| 58 | void *new_func; |
| 59 | /* |
| 60 | * The old_sympos field is optional and can be used to resolve |
| 61 | * duplicate symbol names in livepatch objects. If this field is zero, |
| 62 | * it is expected the symbol is unique, otherwise patching fails. If |
| 63 | * this value is greater than zero then that occurrence of the symbol |
| 64 | * in kallsyms for the given object is used. |
| 65 | */ |
| 66 | unsigned long old_sympos; |
| 67 | |
| 68 | /* internal */ |
| 69 | void *old_func; |
| 70 | struct kobject kobj; |
| 71 | struct list_head node; |
| 72 | struct list_head stack_node; |
| 73 | unsigned long old_size, new_size; |
| 74 | bool nop; |
| 75 | bool patched; |
| 76 | bool transition; |
| 77 | }; |
| 78 | |
| 79 | struct klp_object; |
| 80 | |
| 81 | /** |
| 82 | * struct klp_callbacks - pre/post live-(un)patch callback structure |
| 83 | * @pre_patch: executed before code patching |
| 84 | * @post_patch: executed after code patching |
| 85 | * @pre_unpatch: executed before code unpatching |
| 86 | * @post_unpatch: executed after code unpatching |
| 87 | * @post_unpatch_enabled: flag indicating if post-unpatch callback |
| 88 | * should run |
| 89 | * |
| 90 | * All callbacks are optional. Only the pre-patch callback, if provided, |
| 91 | * will be unconditionally executed. If the parent klp_object fails to |
| 92 | * patch for any reason, including a non-zero error status returned from |
| 93 | * the pre-patch callback, no further callbacks will be executed. |
| 94 | */ |
| 95 | struct klp_callbacks { |
| 96 | int (*pre_patch)(struct klp_object *obj); |
| 97 | void (*post_patch)(struct klp_object *obj); |
| 98 | void (*pre_unpatch)(struct klp_object *obj); |
| 99 | void (*post_unpatch)(struct klp_object *obj); |
| 100 | bool post_unpatch_enabled; |
| 101 | }; |
| 102 | |
| 103 | /** |
| 104 | * struct klp_object - kernel object structure for live patching |
| 105 | * @name: module name (or NULL for vmlinux) |
| 106 | * @funcs: function entries for functions to be patched in the object |
| 107 | * @callbacks: functions to be executed pre/post (un)patching |
| 108 | * @kobj: kobject for sysfs resources |
| 109 | * @func_list: dynamic list of the function entries |
| 110 | * @node: list node for klp_patch obj_list |
| 111 | * @mod: kernel module associated with the patched object |
| 112 | * (NULL for vmlinux) |
| 113 | * @dynamic: temporary object for nop functions; dynamically allocated |
| 114 | * @patched: the object's funcs have been added to the klp_ops list |
| 115 | */ |
| 116 | struct klp_object { |
| 117 | /* external */ |
| 118 | const char *name; |
| 119 | struct klp_func *funcs; |
| 120 | struct klp_callbacks callbacks; |
| 121 | |
| 122 | /* internal */ |
| 123 | struct kobject kobj; |
| 124 | struct list_head func_list; |
| 125 | struct list_head node; |
| 126 | struct module *mod; |
| 127 | bool dynamic; |
| 128 | bool patched; |
| 129 | }; |
| 130 | |
| 131 | /** |
| 132 | * struct klp_state - state of the system modified by the livepatch |
| 133 | * @id: system state identifier (non-zero) |
| 134 | * @version: version of the change |
| 135 | * @data: custom data |
| 136 | */ |
| 137 | struct klp_state { |
| 138 | unsigned long id; |
| 139 | unsigned int version; |
| 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 | /* Called from the module loader during module coming/going states */ |
| 197 | int klp_module_coming(struct module *mod); |
| 198 | void klp_module_going(struct module *mod); |
| 199 | |
| 200 | void klp_copy_process(struct task_struct *child); |
| 201 | void klp_update_patch_state(struct task_struct *task); |
| 202 | |
| 203 | static inline bool klp_patch_pending(struct task_struct *task) |
| 204 | { |
| 205 | return test_tsk_thread_flag(task, TIF_PATCH_PENDING); |
| 206 | } |
| 207 | |
| 208 | static inline bool klp_have_reliable_stack(void) |
| 209 | { |
| 210 | return IS_ENABLED(CONFIG_STACKTRACE) && |
| 211 | IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE); |
| 212 | } |
| 213 | |
| 214 | typedef int (*klp_shadow_ctor_t)(void *obj, |
| 215 | void *shadow_data, |
| 216 | void *ctor_data); |
| 217 | typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data); |
| 218 | |
| 219 | void *klp_shadow_get(void *obj, unsigned long id); |
| 220 | void *klp_shadow_alloc(void *obj, unsigned long id, |
| 221 | size_t size, gfp_t gfp_flags, |
| 222 | klp_shadow_ctor_t ctor, void *ctor_data); |
| 223 | void *klp_shadow_get_or_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_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor); |
| 227 | void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor); |
| 228 | |
| 229 | struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id); |
| 230 | struct klp_state *klp_get_prev_state(unsigned long id); |
| 231 | |
| 232 | int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, |
| 233 | const char *shstrtab, const char *strtab, |
| 234 | unsigned int symindex, unsigned int secindex, |
| 235 | const char *objname); |
| 236 | |
| 237 | #else /* !CONFIG_LIVEPATCH */ |
| 238 | |
| 239 | static inline int klp_module_coming(struct module *mod) { return 0; } |
| 240 | static inline void klp_module_going(struct module *mod) {} |
| 241 | static inline bool klp_patch_pending(struct task_struct *task) { return false; } |
| 242 | static inline void klp_update_patch_state(struct task_struct *task) {} |
| 243 | static inline void klp_copy_process(struct task_struct *child) {} |
| 244 | |
| 245 | static inline |
| 246 | int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, |
| 247 | const char *shstrtab, const char *strtab, |
| 248 | unsigned int symindex, unsigned int secindex, |
| 249 | const char *objname) |
| 250 | { |
| 251 | return 0; |
| 252 | } |
| 253 | |
| 254 | #endif /* CONFIG_LIVEPATCH */ |
| 255 | |
| 256 | #endif /* _LINUX_LIVEPATCH_H_ */ |