e12dcc29cc
Add configs to control removing the macros or not. On some platform,
configureing out the macros removes the associated members from the
structs, this reduces the object size of the slabs related with the
structs, therefore reduces the total slab memory consumption of system.
Besides, this also reduces vmlinux size a bit, therefore the total
kernel memory size increses a bit.
The macros are ANDROID_KABI_RESERVE, ANDROID_VENDOR_DATA,
ANDROID_VENDOR_DATA_ARRAY, ANDROID_OEM_DATA, ANDROID_OEM_DATA_ARRAY.
Bug: 206561931
(cherry picked from commit b7a6c15a6f)
Signed-off-by: Qingqing Zhou <quic_qqzhou@quicinc.com>
(cherry picked from commit 3c06a5ce5e5857a1dff88a784e58e32bbddaf759)
Signed-off-by: Jaskaran Singh <quic_jasksing@quicinc.com>
Change-Id: Iea4b962dff386a17c9bef20ae048be4e17bf43ab
118 lines
3.6 KiB
C
118 lines
3.6 KiB
C
/* 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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