/* SPDX-License-Identifier: GPL-2.0-or-later */

  /*
   * livepatch.h - Kernel Live Patching Core
   *
   * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
   * Copyright (C) 2014 SUSE

   */
  
  #ifndef _LINUX_LIVEPATCH_H_
  #define _LINUX_LIVEPATCH_H_
  
  #include <linux/module.h>
  #include <linux/ftrace.h>

  #include <linux/completion.h>

  #include <linux/list.h>

  #if IS_ENABLED(CONFIG_LIVEPATCH)

  #include <asm/livepatch.h>

  /* task patch states */
  #define KLP_UNDEFINED	-1
  #define KLP_UNPATCHED	 0
  #define KLP_PATCHED	 1

  /**
   * struct klp_func - function structure for live patching
   * @old_name:	name of the function to be patched
   * @new_func:	pointer to the patched function code

   * @old_sympos: a hint indicating which symbol position the old function
   *		can be found (optional)

   * @old_func:	pointer to the function being patched

   * @kobj:	kobject for sysfs resources

   * @node:	list node for klp_object func_list

   * @stack_node:	list node for klp_ops func_stack list

   * @old_size:	size of the old function
   * @new_size:	size of the new function

   * @nop:        temporary patch to use the original code again; dyn. allocated

   * @patched:	the func has been added to the klp_ops list

   * @transition:	the func is currently being applied or reverted
   *
   * The patched and transition variables define the func's patching state.  When
   * patching, a func is always in one of the following states:
   *
   *   patched=0 transition=0: unpatched
   *   patched=0 transition=1: unpatched, temporary starting state
   *   patched=1 transition=1: patched, may be visible to some tasks
   *   patched=1 transition=0: patched, visible to all tasks
   *
   * And when unpatching, it goes in the reverse order:
   *
   *   patched=1 transition=0: patched, visible to all tasks
   *   patched=1 transition=1: patched, may be visible to some tasks
   *   patched=0 transition=1: unpatched, temporary ending state
   *   patched=0 transition=0: unpatched

   */
  struct klp_func {
  	/* external */
  	const char *old_name;
  	void *new_func;
  	/*

  	 * The old_sympos field is optional and can be used to resolve
  	 * duplicate symbol names in livepatch objects. If this field is zero,
  	 * it is expected the symbol is unique, otherwise patching fails. If
  	 * this value is greater than zero then that occurrence of the symbol
  	 * in kallsyms for the given object is used.

  	 */

  	unsigned long old_sympos;

  
  	/* internal */

  	void *old_func;

  	struct kobject kobj;

  	struct list_head node;

  	struct list_head stack_node;

  	unsigned long old_size, new_size;

  	bool nop;

  	bool patched;

  	bool transition;

  };

  struct klp_object;
  
  /**
   * struct klp_callbacks - pre/post live-(un)patch callback structure
   * @pre_patch:		executed before code patching
   * @post_patch:		executed after code patching
   * @pre_unpatch:	executed before code unpatching
   * @post_unpatch:	executed after code unpatching
   * @post_unpatch_enabled:	flag indicating if post-unpatch callback
   * 				should run
   *
   * All callbacks are optional.  Only the pre-patch callback, if provided,
   * will be unconditionally executed.  If the parent klp_object fails to
   * patch for any reason, including a non-zero error status returned from
   * the pre-patch callback, no further callbacks will be executed.
   */
  struct klp_callbacks {
  	int (*pre_patch)(struct klp_object *obj);
  	void (*post_patch)(struct klp_object *obj);
  	void (*pre_unpatch)(struct klp_object *obj);
  	void (*post_unpatch)(struct klp_object *obj);
  	bool post_unpatch_enabled;
  };

  /**

   * struct klp_object - kernel object structure for live patching
   * @name:	module name (or NULL for vmlinux)

   * @funcs:	function entries for functions to be patched in the object

   * @callbacks:	functions to be executed pre/post (un)patching

   * @kobj:	kobject for sysfs resources

   * @func_list:	dynamic list of the function entries
   * @node:	list node for klp_patch obj_list

   * @mod:	kernel module associated with the patched object

   *		(NULL for vmlinux)

   * @dynamic:    temporary object for nop functions; dynamically allocated

   * @patched:	the object's funcs have been added to the klp_ops list

   */
  struct klp_object {
  	/* external */
  	const char *name;

  	struct klp_func *funcs;

  	struct klp_callbacks callbacks;

  
  	/* internal */

  	struct kobject kobj;

  	struct list_head func_list;
  	struct list_head node;

  	struct module *mod;

  	bool dynamic;

  	bool patched;

  };
  
  /**

   * struct klp_state - state of the system modified by the livepatch
   * @id:		system state identifier (non-zero)

   * @version:	version of the change

   * @data:	custom data
   */
  struct klp_state {
  	unsigned long id;

  	unsigned int version;

  	void *data;
  };
  
  /**

   * struct klp_patch - patch structure for live patching
   * @mod:	reference to the live patch module
   * @objs:	object entries for kernel objects to be patched

   * @states:	system states that can get modified

   * @replace:	replace all actively used patches

   * @list:	list node for global list of actively used patches

   * @kobj:	kobject for sysfs resources

   * @obj_list:	dynamic list of the object entries

   * @enabled:	the patch is enabled (but operation may be incomplete)

   * @forced:	was involved in a forced transition

   * @free_work:	patch cleanup from workqueue-context

   * @finish:	for waiting till it is safe to remove the patch module

   */
  struct klp_patch {
  	/* external */
  	struct module *mod;
  	struct klp_object *objs;

  	struct klp_state *states;

  	bool replace;

  
  	/* internal */
  	struct list_head list;
  	struct kobject kobj;

  	struct list_head obj_list;

  	bool enabled;

  	bool forced;

  	struct work_struct free_work;

  	struct completion finish;

  };

  #define klp_for_each_object_static(patch, obj) \

  	for (obj = patch->objs; obj->funcs || obj->name; obj++)

  #define klp_for_each_object_safe(patch, obj, tmp_obj)		\
  	list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node)

  #define klp_for_each_object(patch, obj)	\
  	list_for_each_entry(obj, &patch->obj_list, node)
  
  #define klp_for_each_func_static(obj, func) \

  	for (func = obj->funcs; \
  	     func->old_name || func->new_func || func->old_sympos; \
  	     func++)

  #define klp_for_each_func_safe(obj, func, tmp_func)			\
  	list_for_each_entry_safe(func, tmp_func, &obj->func_list, node)

  #define klp_for_each_func(obj, func)	\
  	list_for_each_entry(func, &obj->func_list, node)

  int klp_enable_patch(struct klp_patch *);

  /* Called from the module loader during module coming/going states */
  int klp_module_coming(struct module *mod);
  void klp_module_going(struct module *mod);

  void klp_copy_process(struct task_struct *child);

  void klp_update_patch_state(struct task_struct *task);

  static inline bool klp_patch_pending(struct task_struct *task)
  {
  	return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
  }
  
  static inline bool klp_have_reliable_stack(void)
  {
  	return IS_ENABLED(CONFIG_STACKTRACE) &&
  	       IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
  }

  typedef int (*klp_shadow_ctor_t)(void *obj,
  				 void *shadow_data,
  				 void *ctor_data);

  typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);

  void *klp_shadow_get(void *obj, unsigned long id);

  void *klp_shadow_alloc(void *obj, unsigned long id,
  		       size_t size, gfp_t gfp_flags,
  		       klp_shadow_ctor_t ctor, void *ctor_data);
  void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
  			      size_t size, gfp_t gfp_flags,
  			      klp_shadow_ctor_t ctor, void *ctor_data);

  void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
  void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);

  struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id);
  struct klp_state *klp_get_prev_state(unsigned long id);

  int 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);

  #else /* !CONFIG_LIVEPATCH */
  
  static inline int klp_module_coming(struct module *mod) { return 0; }

  static inline void klp_module_going(struct module *mod) {}

  static inline bool klp_patch_pending(struct task_struct *task) { return false; }

  static inline void klp_update_patch_state(struct task_struct *task) {}

  static inline void klp_copy_process(struct task_struct *child) {}

  static inline
  int 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)
  {
  	return 0;
  }

  #endif /* CONFIG_LIVEPATCH */

  #endif /* _LINUX_LIVEPATCH_H_ */