/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* android_kabi.h - Android kernel abi abstraction header
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*
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* Copyright (C) 2020 Google, Inc.
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*
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* Heavily influenced by rh_kabi.h which came from the RHEL/CENTOS kernel and
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* was:
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* Copyright (c) 2014 Don Zickus
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* Copyright (c) 2015-2018 Jiri Benc
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* Copyright (c) 2015 Sabrina Dubroca, Hannes Frederic Sowa
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* Copyright (c) 2016-2018 Prarit Bhargava
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* Copyright (c) 2017 Paolo Abeni, Larry Woodman
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*
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* These macros are to be used to try to help alleviate future kernel abi
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* changes that will occur as LTS and other kernel patches are merged into the
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* tree during a period in which the kernel abi is wishing to not be disturbed.
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*
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* There are two times these macros should be used:
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* - Before the kernel abi is "frozen"
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* Padding can be added to various kernel structures that have in the past
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* been known to change over time. That will give "room" in the structure
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* that can then be used when fields are added so that the structure size
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* will not change.
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*
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* - After the kernel abi is "frozen"
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* If a structure's field is changed to a type that is identical in size to
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* the previous type, it can be changed with a union macro
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* If a field is added to a structure, the padding fields can be used to add
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* the new field in a "safe" way.
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*/
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#ifndef _ANDROID_KABI_H
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#define _ANDROID_KABI_H
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#include <linux/compiler.h>
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/*
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* Worker macros, don't use these, use the ones without a leading '_'
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*/
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#define __ANDROID_KABI_CHECK_SIZE_ALIGN(_orig, _new) \
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union { \
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_Static_assert(sizeof(struct{_new;}) <= sizeof(struct{_orig;}), \
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__FILE__ ":" __stringify(__LINE__) ": " \
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__stringify(_new) \
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" is larger than " \
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__stringify(_orig) ); \
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_Static_assert(__alignof__(struct{_new;}) <= __alignof__(struct{_orig;}), \
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__FILE__ ":" __stringify(__LINE__) ": " \
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__stringify(_orig) \
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" is not aligned the same as " \
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__stringify(_new) ); \
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}
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#ifdef __GENKSYMS__
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#define _ANDROID_KABI_REPLACE(_orig, _new) _orig
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#else
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#define _ANDROID_KABI_REPLACE(_orig, _new) \
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union { \
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_new; \
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struct { \
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_orig; \
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}; \
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__ANDROID_KABI_CHECK_SIZE_ALIGN(_orig, _new); \
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}
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#endif /* __GENKSYMS__ */
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#define _ANDROID_KABI_RESERVE(n) u64 android_kabi_reserved##n
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/*
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* Macros to use _before_ the ABI is frozen
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*/
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/*
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* ANDROID_KABI_RESERVE
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* Reserve some "padding" in a structure for potential future use.
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* This normally placed at the end of a structure.
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* number: the "number" of the padding variable in the structure. Start with
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* 1 and go up.
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*/
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#ifdef CONFIG_ANDROID_KABI_RESERVE
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#define ANDROID_KABI_RESERVE(number) _ANDROID_KABI_RESERVE(number)
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#else
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#define ANDROID_KABI_RESERVE(number)
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#endif
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/*
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* Macros to use _after_ the ABI is frozen
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*/
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/*
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* ANDROID_KABI_USE(number, _new)
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* Use a previous padding entry that was defined with ANDROID_KABI_RESERVE
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* number: the previous "number" of the padding variable
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* _new: the variable to use now instead of the padding variable
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*/
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#define ANDROID_KABI_USE(number, _new) \
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_ANDROID_KABI_REPLACE(_ANDROID_KABI_RESERVE(number), _new)
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/*
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* ANDROID_KABI_USE2(number, _new1, _new2)
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* Use a previous padding entry that was defined with ANDROID_KABI_RESERVE for
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* two new variables that fit into 64 bits. This is good for when you do not
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* want to "burn" a 64bit padding variable for a smaller variable size if not
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* needed.
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*/
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#define ANDROID_KABI_USE2(number, _new1, _new2) \
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_ANDROID_KABI_REPLACE(_ANDROID_KABI_RESERVE(number), struct{ _new1; _new2; })
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#endif /* _ANDROID_KABI_H */
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