kabi: Generalize naming of kabi helper macros

 *   approaches can (and often are) combined.

 *

 *   To use this for 'struct foo' (the "base structure"), define a new

 *   structure called 'struct foo_rh'; this new struct is called "auxiliary

 *   structure called 'struct foo_resvd'; this new struct is called "auxiliary

 *   structure".  Then add KABI_AUX_EMBED or KABI_AUX_PTR to the end

 *   of the base structure.  The argument is the name of the base structure,

 *   without the 'struct' keyword.

 *   end.  Note the auxiliary structure cannot be shrunk in size later (i.e.,

 *   fields cannot be removed, only deprecated).  Any code accessing fields

 *   from the aux struct must guard the access using the KABI_AUX macro.

 *   The access itself is then done via a '_rh' field in the base struct.

 *   The access itself is then done via a '_resvd' field in the base struct.

 *

 *   The auxiliary structure is not guaranteed for access by modules unless

 *   explicitly commented as such in the declaration of the aux struct

 *

 *   Example:

 *

 *   struct foo_rh {

 *   struct foo_resvd {

 *           int newly_added;

 *   };

 *

 *   void use(struct foo *f)

 *   {

 *           if (KABI_AUX(f, foo, newly_added))

 *                   f->_rh->newly_added = 123;

 *                   f->_resvd->newly_added = 123;

 *	     else

 *	             // the field 'newly_added' is not present in the passed

 *	             // struct, fall back to old behavior

 *	             f->big_hammer = true;

 *   }

 *

 *   static struct foo_rh my_foo_rh {

 *   static struct foo_resvd my_foo_resvd {

 *           .newly_added = 0;

 *   }

 *

 *   static struct foo my_foo = {

 *           .big_hammer = false,

 *           ._rh = &my_foo_rh,

 *           ._resvd = &my_foo_resvd,

 *           KABI_AUX_INIT_SIZE(foo)

 *   };

 *

 *

 *   Example:

 *

 *   struct foo_rh {

 *   struct foo_resvd {

 *   };

 *

 *   struct foo {

		_Static_assert(__alignof__(struct{_new;}) <= __alignof__(struct{_orig;}), \

			       __FILE__ ":" __stringify(__LINE__) ": "  __stringify(_orig) " is not aligned the same as " __stringify(_new) KABI_ALIGN_WARNING); \

	}

# define __ABI_CHECK_SIZE(_item, _size)				\

# define __KABI_CHECK_SIZE(_item, _size)				\

	_Static_assert(sizeof(struct{_item;}) <= _size,			\

		       __FILE__ ":" __stringify(__LINE__) ": " __stringify(_item) " is larger than the reserved size (" __stringify(_size) " bytes)" KABI_ALIGN_WARNING)

#else

	})

#define _KABI_AUX_PTR(_struct)					\

	size_t _struct##_size_rh;					\

	_KABI_EXCLUDE(struct _struct##_rh *_rh)

	size_t _struct##_size_resvd;					\

	_KABI_EXCLUDE(struct _struct##_resvd *_resvd)

#define KABI_AUX_PTR(_struct)					\

	_KABI_AUX_PTR(_struct);

#define _KABI_AUX_EMBED(_struct)					\

	size_t _struct##_size_rh;					\

	_KABI_EXCLUDE(struct _struct##_rh _rh)

	size_t _struct##_size_resvd;					\

	_KABI_EXCLUDE(struct _struct##_resvd _resvd)

#define KABI_AUX_EMBED(_struct)					\

	_KABI_AUX_EMBED(_struct);

/*

 * KABI_AUX_SET_SIZE calculates and sets the size of the extended struct and

 * stores it in the size_rh field for structs that are dynamically allocated.

 * stores it in the size_resvd field for structs that are dynamically allocated.

 * This macro MUST be called when expanding a base struct with

 * KABI_SIZE_AND_EXTEND, and it MUST be called from the allocation site

 * regardless of being allocated in the kernel or a module.

 * a semicolon is necessary at the end of the line where it is invoked.

 */

#define KABI_AUX_SET_SIZE(_name, _struct) ({				\

	(_name)->_struct##_size_rh = sizeof(struct _struct##_rh);	\

	(_name)->_struct##_size_resvd = sizeof(struct _struct##_resvd);	\

})

/*

 * KABI_AUX_INIT_SIZE calculates and sets the size of the extended struct and

 * stores it in the size_rh field for structs that are statically allocated.

 * stores it in the size_resvd field for structs that are statically allocated.

 * This macro MUST be called when expanding a base struct with

 * KABI_SIZE_AND_EXTEND, and it MUST be called from the declaration site

 * regardless of being allocated in the kernel or a module.

 */

#define KABI_AUX_INIT_SIZE(_struct)					\

	._struct##_size_rh = sizeof(struct _struct##_rh),

	._struct##_size_resvd = sizeof(struct _struct##_resvd),

/*

 * KABI_AUX verifies allocated memory exists.  This MUST be called to

 * verify that memory in the _rh struct is valid, and can be called

 * verify that memory in the _resvd struct is valid, and can be called

 * regardless if KABI_SIZE_AND_EXTEND or KABI_SIZE_AND_EXTEND_PTR is

 * used.

 */

#define KABI_AUX(_ptr, _struct, _field) ({				\

	size_t __off = offsetof(struct _struct##_rh, _field);		\

	(_ptr)->_struct##_size_rh > __off ? true : false;		\

	size_t __off = offsetof(struct _struct##_resvd, _field);		\

	(_ptr)->_struct##_size_resvd > __off ? true : false;		\

})

#endif /* _LINUX_KABI_H */