include/linux/livepatch.h

   1 /*
   2  * livepatch.h - Kernel Live Patching Core
   3  *
   4  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   5  * Copyright (C) 2014 SUSE
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2
  10  * of the License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #ifndef _LINUX_LIVEPATCH_H_
  22 #define _LINUX_LIVEPATCH_H_
  23
  24 #include <linux/module.h>
  25 #include <linux/ftrace.h>
  26 #include <linux/completion.h>
  27
  28 #if IS_ENABLED(CONFIG_LIVEPATCH)
  29
  30 #include <asm/livepatch.h>
  31
  32 /* task patch states */
  33 #define KLP_UNDEFINED   -1
  34 #define KLP_UNPATCHED    0
  35 #define KLP_PATCHED      1
  36
  37 /**
  38  * struct klp_func - function structure for live patching
  39  * @old_name:   name of the function to be patched
  40  * @new_func:   pointer to the patched function code
  41  * @old_sympos: a hint indicating which symbol position the old function
  42  *              can be found (optional)
  43  * @immediate:  patch the func immediately, bypassing safety mechanisms
  44  * @old_addr:   the address of the function being patched
  45  * @kobj:       kobject for sysfs resources
  46  * @stack_node: list node for klp_ops func_stack list
  47  * @old_size:   size of the old function
  48  * @new_size:   size of the new function
  49  * @patched:    the func has been added to the klp_ops list
  50  * @transition: the func is currently being applied or reverted
  51  *
  52  * The patched and transition variables define the func's patching state.  When
  53  * patching, a func is always in one of the following states:
  54  *
  55  *   patched=0 transition=0: unpatched
  56  *   patched=0 transition=1: unpatched, temporary starting state
  57  *   patched=1 transition=1: patched, may be visible to some tasks
  58  *   patched=1 transition=0: patched, visible to all tasks
  59  *
  60  * And when unpatching, it goes in the reverse order:
  61  *
  62  *   patched=1 transition=0: patched, visible to all tasks
  63  *   patched=1 transition=1: patched, may be visible to some tasks
  64  *   patched=0 transition=1: unpatched, temporary ending state
  65  *   patched=0 transition=0: unpatched
  66  */
  67 struct klp_func {
  68         /* external */
  69         const char *old_name;
  70         void *new_func;
  71         /*
  72          * The old_sympos field is optional and can be used to resolve
  73          * duplicate symbol names in livepatch objects. If this field is zero,
  74          * it is expected the symbol is unique, otherwise patching fails. If
  75          * this value is greater than zero then that occurrence of the symbol
  76          * in kallsyms for the given object is used.
  77          */
  78         unsigned long old_sympos;
  79         bool immediate;
  80
  81         /* internal */
  82         unsigned long old_addr;
  83         struct kobject kobj;
  84         struct list_head stack_node;
  85         unsigned long old_size, new_size;
  86         bool patched;
  87         bool transition;
  88 };
  89
  90 /**
  91  * struct klp_object - kernel object structure for live patching
  92  * @name:       module name (or NULL for vmlinux)
  93  * @funcs:      function entries for functions to be patched in the object
  94  * @kobj:       kobject for sysfs resources
  95  * @mod:        kernel module associated with the patched object
  96  *              (NULL for vmlinux)
  97  * @patched:    the object's funcs have been added to the klp_ops list
  98  */
  99 struct klp_object {
 100         /* external */
 101         const char *name;
 102         struct klp_func *funcs;
 103
 104         /* internal */
 105         struct kobject kobj;
 106         struct module *mod;
 107         bool patched;
 108 };
 109
 110 /**
 111  * struct klp_patch - patch structure for live patching
 112  * @mod:        reference to the live patch module
 113  * @objs:       object entries for kernel objects to be patched
 114  * @immediate:  patch all funcs immediately, bypassing safety mechanisms
 115  * @list:       list node for global list of registered patches
 116  * @kobj:       kobject for sysfs resources
 117  * @enabled:    the patch is enabled (but operation may be incomplete)
 118  * @finish:     for waiting till it is safe to remove the patch module
 119  */
 120 struct klp_patch {
 121         /* external */
 122         struct module *mod;
 123         struct klp_object *objs;
 124         bool immediate;
 125
 126         /* internal */
 127         struct list_head list;
 128         struct kobject kobj;
 129         bool enabled;
 130         struct completion finish;
 131 };
 132
 133 #define klp_for_each_object(patch, obj) \
 134         for (obj = patch->objs; obj->funcs || obj->name; obj++)
 135
 136 #define klp_for_each_func(obj, func) \
 137         for (func = obj->funcs; \
 138              func->old_name || func->new_func || func->old_sympos; \
 139              func++)
 140
 141 int klp_register_patch(struct klp_patch *);
 142 int klp_unregister_patch(struct klp_patch *);
 143 int klp_enable_patch(struct klp_patch *);
 144 int klp_disable_patch(struct klp_patch *);
 145
 146 void arch_klp_init_object_loaded(struct klp_patch *patch,
 147                                  struct klp_object *obj);
 148
 149 /* Called from the module loader during module coming/going states */
 150 int klp_module_coming(struct module *mod);
 151 void klp_module_going(struct module *mod);
 152
 153 void klp_copy_process(struct task_struct *child);
 154 void klp_update_patch_state(struct task_struct *task);
 155
 156 static inline bool klp_patch_pending(struct task_struct *task)
 157 {
 158         return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
 159 }
 160
 161 static inline bool klp_have_reliable_stack(void)
 162 {
 163         return IS_ENABLED(CONFIG_STACKTRACE) &&
 164                IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
 165 }
 166
 167 #else /* !CONFIG_LIVEPATCH */
 168
 169 static inline int klp_module_coming(struct module *mod) { return 0; }
 170 static inline void klp_module_going(struct module *mod) {}
 171 static inline bool klp_patch_pending(struct task_struct *task) { return false; }
 172 static inline void klp_update_patch_state(struct task_struct *task) {}
 173 static inline void klp_copy_process(struct task_struct *child) {}
 174
 175 #endif /* CONFIG_LIVEPATCH */
 176
 177 #endif /* _LINUX_LIVEPATCH_H_ */