Giuliano Procida
6a50a8334a
If BUILD_VDSO or __DISABLE_EXPORTS are defined, only disable the KABI macros that cause symbols to be emitted in special gendwarfksym sections. Preserve the other macros. This is to avoid diverging type definitions that upset pahole. Bug: 400972353 Bug: 445902333 Change-Id: Ifea62ced4730bdd7350df3b7c74d661a84b038af Signed-off-by: Giuliano Procida <gprocida@google.com>
210 lines
6.8 KiB
C
210 lines
6.8 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) 2020-2025 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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#ifdef CONFIG_ANDROID_KABI_RESERVE
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#include <linux/args.h>
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#include <linux/compiler.h>
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#include <linux/compiler_attributes.h>
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#include <linux/stringify.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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#if defined(BUILD_VDSO) || defined(__DISABLE_EXPORTS)
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#define __ANDROID_KABI_RULE(hint, target, value)
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#else
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#define __ANDROID_KABI_RULE(hint, target, value) \
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static const char CONCATENATE(__gendwarfksyms_rule_, \
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__COUNTER__)[] __used __aligned(1) \
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__section(".discard.gendwarfksyms.kabi_rules") = \
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"1\0" #hint "\0" target "\0" value
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#endif
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#define _ANDROID_KABI_RULE(hint, target, value) \
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__ANDROID_KABI_RULE(hint, #target, #value)
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#define _ANDROID_KABI_NORMAL_SIZE_ALIGN(_orig, _new) \
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union { \
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_Static_assert( \
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sizeof(struct { _new; }) <= \
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sizeof(struct { _orig; }), \
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FILE_LINE ": " __stringify(_new) \
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" is larger than " __stringify(_orig)); \
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_Static_assert( \
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__alignof__(struct { _new; }) <= \
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__alignof__(struct { _orig; }), \
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FILE_LINE ": " __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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#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_NORMAL_SIZE_ALIGN(_orig, _new); \
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}
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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 use by LTS backports.
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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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*
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* ANDROID_BACKPORT_RESERVE
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* Similar to ANDROID_KABI_RESERVE, but this is for planned feature backports
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* (not for LTS).
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*/
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#define ANDROID_KABI_RESERVE(number) u64 __kabi_reserved##number
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#define ANDROID_BACKPORT_RESERVE(number) u64 __kabi_reserved_backport##number
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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_DECLONLY(fqn)
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* Treat the struct/union/enum fqn as a declaration, i.e. even if
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* a definition is available, don't expand the contents.
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*/
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#define ANDROID_KABI_DECLONLY(fqn) _ANDROID_KABI_RULE(declonly, fqn, /**/)
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/*
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* ANDROID_KABI_ENUMERATOR_IGNORE(fqn, field)
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* When expanding enum fqn, skip the provided field. This makes it
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* possible to hide added enum fields from versioning.
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*/
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#define ANDROID_KABI_ENUMERATOR_IGNORE(fqn, field) \
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_ANDROID_KABI_RULE(enumerator_ignore, fqn field, /**/)
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/*
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* ANDROID_KABI_ENUMERATOR_VALUE(fqn, field, value)
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* When expanding enum fqn, use the provided value for the
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* specified field. This makes it possible to override enumerator
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* values when calculating versions.
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*/
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#define ANDROID_KABI_ENUMERATOR_VALUE(fqn, field, value) \
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_ANDROID_KABI_RULE(enumerator_value, fqn field, value)
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/*
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* ANDROID_KABI_BYTE_SIZE(fqn, value)
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* Set the byte_size attribute for the struct/union/enum fqn to
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* value bytes.
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*/
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#define ANDROID_KABI_BYTE_SIZE(fqn, value) \
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_ANDROID_KABI_RULE(byte_size, fqn, value)
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/*
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* ANDROID_KABI_TYPE_STRING(type, str)
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* For the given type, override the type string used in symtypes
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* output and version calculation with str.
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*/
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#define ANDROID_KABI_TYPE_STRING(type, str) \
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__ANDROID_KABI_RULE(type_string, type, str)
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/*
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* ANDROID_KABI_IGNORE
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* Add a new field that's ignored in versioning.
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*/
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#define ANDROID_KABI_IGNORE(n, _new) \
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union { \
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_new; \
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unsigned char __kabi_ignored##n; \
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}
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/*
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* ANDROID_KABI_REPLACE
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* Replace a field with a compatible new field.
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*/
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#define ANDROID_KABI_REPLACE(_oldtype, _oldname, _new) \
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_ANDROID_KABI_REPLACE(_oldtype __kabi_renamed##_oldname, struct { _new; })
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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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/*
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* ANDROID_BACKPORT_USE(number, _new)
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* Use a previous padding entry that was defined with ANDROID_BACKPORT_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_BACKPORT_USE(number, _new) \
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_ANDROID_KABI_REPLACE(ANDROID_BACKPORT_RESERVE(number), _new)
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#else /* CONFIG_ANDROID_KABI_RESERVE */
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#define ANDROID_KABI_RESERVE(number)
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#define ANDROID_BACKPORT_RESERVE(number)
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#define ANDROID_KABI_DECLONLY(fqn)
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#define ANDROID_KABI_ENUMERATOR_IGNORE(fqn, field)
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#define ANDROID_KABI_ENUMERATOR_VALUE(fqn, field, value)
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#define ANDROID_KABI_BYTE_SIZE(fqn, value)
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#define ANDROID_KABI_TYPE_STRING(type, str)
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#define ANDROID_KABI_IGNORE(n, _new) _new
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#define ANDROID_KABI_REPLACE(_oldtype, _oldname, _new) _new
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#define ANDROID_KABI_USE(number, _new) _new
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#define ANDROID_KABI_USE2(number, _new1, _new2) _new1; _new2
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#endif /* CONFIG_ANDROID_KABI_RESERVE */
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#endif /* _ANDROID_KABI_H */
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