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/*
* rh_kabi.h - Red Hat kabi abstraction header
*
* Copyright (c) 2014 Don Zickus
*
* This file is released under the GPLv2.
* See the file COPYING for more details.
*
* "Anyone can make KABI pass, not everyone can fix it."
* - Don Zickus
*
* The use of these macros does not guarantee that the usage and modification
* of code is correct. As with all Red Hat only changes, an engineer must
* explain why the use of the macro is valid in the patch containing the
* changes.
*
*/
#ifndef _LINUX_RH_KABI_H
#define _LINUX_RH_KABI_H
#include <linux/compiler.h>
#include <linux/stringify.h>
/*
* The RH_KABI_REPLACE* macros attempt to add the ability to use the '_new'
* element while preserving size alignment and kabi agreement with the '_orig'
* element.
*
* The #ifdef __GENKSYMS__ preserves the kabi agreement, while the anonymous
* union structure preserves the size alignment (assuming the '_new' element is
* not bigger than the '_orig' element).
*
* RH_KABI_REPLACE - simple replacement of _orig with a union of _orig and _new
* RH_KABI_DEPRECATE - mark the element as deprecated and make it unusable
* by modules while preserving kABI checksums
* RH_KABI_DEPRECATE_FN - mark the function pointer as deprecated and make it
* unusable by modules while preserving kABI checksums
*
* RH_KABI_EXTEND - simple macro for adding a new element to a struct while
* preserving the kabi agreement (by wrapping with GENKSYMS).
* RH_KABI_FILL_HOLE - simple macro for filling a hole in a struct while
* preserving the kabi agreement (by wrapping with GENKSYMS).
* RH_KABI_RENAME - simple macro for renaming an element without changing its type
* while preserving thi kabi agreement (by wrapping with GENKSYMS).
* This macro can be used in bitfields, for example.
* NOTE: does not include the final ';'
* RH_KABI_REPLACE_UNSAFE - unsafe version of RH_KABI_REPLACE. Only use for typedefs.
*
* NOTE NOTE NOTE
* Don't use ';' after these macros as it messes up the kabi checker by
* changing what the resulting token string looks like.
* Instead let this macro add the ';' so it can be properly hidden from
* the kabi checker (mainly for RH_KABI_EXTEND, but applied to all macros for
* uniformity).
* NOTE NOTE NOTE
*
* RH_KABI_CONST - adds a new const modifier to a function parameter
* preserving the old checksum
*
* This macro does the opposite: it changes the symbol checksum without
* actually changing anything about the exported symbol. It is useful for
* symbols that are not whitelisted, we're changing them in an incompatible
* way and want to prevent 3rd party modules to silently corrupt memory.
* Instead, by changing the symbol checksum, such modules won't be loaded by
* the kernel. This macro should only be used as a last resort when all other
* KABI workarounds have failed.
*
* RH_KABI_FORCE_CHANGE - Force change of the symbol checksum. The argument
* of the macro is a version for cases we need to do
* this more than once.
*/
#ifdef __GENKSYMS__
# define _RH_KABI_REPLACE(_orig, _new) _orig
# define _RH_KABI_REPLACE_UNSAFE(_orig, _new) _orig
# define _RH_KABI_DEPRECATE(_type, _orig) _type _orig
# define _RH_KABI_DEPRECATE_FN(_type, _orig, _args...) _type (*_orig)(_args)
# define RH_KABI_EXTEND(_new)
# define RH_KABI_FILL_HOLE(_new)
# define RH_KABI_RENAME(_orig, _new) _orig
# define RH_KABI_CONST
# define RH_KABI_FORCE_CHANGE(ver) __attribute__((rh_kabi_change ## ver))
#else
#define RH_KABI_ALIGN_WARNING ". Disable CONFIG_RH_KABI_SIZE_ALIGN_CHECKS if debugging."
#if IS_BUILTIN(CONFIG_RH_KABI_SIZE_ALIGN_CHECKS)
#define __RH_KABI_CHECK_SIZE_ALIGN(_orig, _new) \
union { \
_Static_assert(sizeof(struct{_new;}) <= sizeof(struct{_orig;}), \
__FILE__ ":" __stringify(__LINE__) ": " __stringify(_new) " is larger than " __stringify(_orig) RH_KABI_ALIGN_WARNING); \
_Static_assert(__alignof__(struct{_new;}) <= __alignof__(struct{_orig;}), \
__FILE__ ":" __stringify(__LINE__) ": " __stringify(_orig) " is not aligned the same as " __stringify(_new) RH_KABI_ALIGN_WARNING); \
}
#else
#define __RH_KABI_CHECK_SIZE_ALIGN(_orig, _new)
#endif
# define _RH_KABI_REPLACE(_orig, _new) \
union { \
_new; \
struct { \
_orig; \
} __UNIQUE_ID(rh_kabi_hide); \
__RH_KABI_CHECK_SIZE_ALIGN(_orig, _new); \
}
#define _RH_KABI_REPLACE_UNSAFE(_orig, _new) _new
# define _RH_KABI_DEPRECATE(_type, _orig) _type rh_reserved_##_orig
# define _RH_KABI_DEPRECATE_FN(_type, _orig, _args...) \
_type (* rh_reserved_##_orig)(_args)
# define RH_KABI_EXTEND(_new) _new;
/* Warning, only use if a hole exists for _all_ arches. Use pahole to verify */
# define RH_KABI_FILL_HOLE(_new) _new;
# define RH_KABI_RENAME(_orig, _new) _new
# define RH_KABI_CONST const
# define RH_KABI_FORCE_CHANGE(ver)
#endif /* __GENKSYMS__ */
/* colon added wrappers for the RH_KABI_REPLACE macros */
#define RH_KABI_REPLACE(_orig, _new) _RH_KABI_REPLACE(_orig, _new);
#define RH_KABI_REPLACE_UNSAFE(_orig, _new) _RH_KABI_REPLACE_UNSAFE(_orig, _new);
#define RH_KABI_DEPRECATE(_type, _orig) _RH_KABI_DEPRECATE(_type, _orig);
#define RH_KABI_DEPRECATE_FN(_type, _orig, _args...) \
_RH_KABI_DEPRECATE_FN(_type, _orig, _args);
/*
* We tried to standardize on Red Hat reserved names. These wrappers leverage
* those common names making it easier to read and find in the code.
*/
#define _RH_KABI_RESERVE(n) unsigned long rh_reserved##n
#define _RH_KABI_RESERVE_P(n) void (*rh_reserved##n)(void)
#define RH_KABI_RESERVE(n) _RH_KABI_RESERVE(n);
#define RH_KABI_RESERVE_P(n) _RH_KABI_RESERVE_P(n);
/*
* Simple wrappers to replace standard Red Hat reserved elements.
*/
#define RH_KABI_USE(n, _new) RH_KABI_REPLACE(_RH_KABI_RESERVE(n), _new)
#define RH_KABI_USE_P(n, _new) RH_KABI_REPLACE(_RH_KABI_RESERVE_P(n), _new)
/*
* Macros for breaking up a reserved element into two smaller chunks using an
* anonymous struct inside an anonymous union.
*/
#define RH_KABI_USE2(n, _new1, _new2) RH_KABI_REPLACE(_RH_KABI_RESERVE(n), struct{ _new1; _new2; })
#define RH_KABI_USE2_P(n, _new1, _new2) RH_KABI_REPLACE(_RH_KABI_RESERVE_P(n), struct{ _new1; _new2;})
/*
* Macro for breaking up a random element into two smaller chunks using an anonymous
* struct inside an anonymous union.
*/
#define RH_KABI_REPLACE2(orig, _new1, _new2) RH_KABI_REPLACE(orig, struct{ _new1; _new2;})
#endif /* _LINUX_RH_KABI_H */
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