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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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29bb79e9db
Add new TRAILING_OVERLAP() helper macro to create a union between a flexible-array member (FAM) and a set of members that would otherwise follow it. This overlays the trailing members onto the FAM while preserving the original memory layout. Co-developed-by: Kees Cook <kees@kernel.org> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Link: https://lore.kernel.org/r/aFG8gEwKXAWWIvX0@kspp Signed-off-by: Kees Cook <kees@kernel.org>
117 lines
3.8 KiB
C
117 lines
3.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_STDDEF_H
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#define _LINUX_STDDEF_H
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#include <uapi/linux/stddef.h>
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#undef NULL
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#define NULL ((void *)0)
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enum {
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false = 0,
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true = 1
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};
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#undef offsetof
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#define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER)
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/**
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* sizeof_field() - Report the size of a struct field in bytes
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*
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* @TYPE: The structure containing the field of interest
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* @MEMBER: The field to return the size of
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*/
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#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
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/**
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* offsetofend() - Report the offset of a struct field within the struct
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*
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* @TYPE: The type of the structure
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* @MEMBER: The member within the structure to get the end offset of
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*/
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#define offsetofend(TYPE, MEMBER) \
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(offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
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/**
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* struct_group() - Wrap a set of declarations in a mirrored struct
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*
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* @NAME: The identifier name of the mirrored sub-struct
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* @MEMBERS: The member declarations for the mirrored structs
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*
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* Used to create an anonymous union of two structs with identical
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* layout and size: one anonymous and one named. The former can be
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* used normally without sub-struct naming, and the latter can be
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* used to reason about the start, end, and size of the group of
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* struct members.
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*/
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#define struct_group(NAME, MEMBERS...) \
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__struct_group(/* no tag */, NAME, /* no attrs */, MEMBERS)
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/**
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* struct_group_attr() - Create a struct_group() with trailing attributes
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*
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* @NAME: The identifier name of the mirrored sub-struct
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* @ATTRS: Any struct attributes to apply
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* @MEMBERS: The member declarations for the mirrored structs
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*
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* Used to create an anonymous union of two structs with identical
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* layout and size: one anonymous and one named. The former can be
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* used normally without sub-struct naming, and the latter can be
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* used to reason about the start, end, and size of the group of
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* struct members. Includes structure attributes argument.
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*/
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#define struct_group_attr(NAME, ATTRS, MEMBERS...) \
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__struct_group(/* no tag */, NAME, ATTRS, MEMBERS)
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/**
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* struct_group_tagged() - Create a struct_group with a reusable tag
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*
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* @TAG: The tag name for the named sub-struct
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* @NAME: The identifier name of the mirrored sub-struct
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* @MEMBERS: The member declarations for the mirrored structs
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*
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* Used to create an anonymous union of two structs with identical
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* layout and size: one anonymous and one named. The former can be
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* used normally without sub-struct naming, and the latter can be
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* used to reason about the start, end, and size of the group of
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* struct members. Includes struct tag argument for the named copy,
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* so the specified layout can be reused later.
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*/
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#define struct_group_tagged(TAG, NAME, MEMBERS...) \
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__struct_group(TAG, NAME, /* no attrs */, MEMBERS)
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/**
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* DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
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*
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* @TYPE: The type of each flexible array element
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* @NAME: The name of the flexible array member
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*
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* In order to have a flexible array member in a union or alone in a
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* struct, it needs to be wrapped in an anonymous struct with at least 1
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* named member, but that member can be empty.
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*/
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#define DECLARE_FLEX_ARRAY(TYPE, NAME) \
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__DECLARE_FLEX_ARRAY(TYPE, NAME)
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/**
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* TRAILING_OVERLAP() - Overlap a flexible-array member with trailing members.
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*
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* Creates a union between a flexible-array member (FAM) in a struct and a set
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* of additional members that would otherwise follow it.
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*
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* @TYPE: Flexible structure type name, including "struct" keyword.
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* @NAME: Name for a variable to define.
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* @FAM: The flexible-array member within @TYPE
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* @MEMBERS: Trailing overlapping members.
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*/
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#define TRAILING_OVERLAP(TYPE, NAME, FAM, MEMBERS) \
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union { \
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TYPE NAME; \
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struct { \
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unsigned char __offset_to_##FAM[offsetof(TYPE, FAM)]; \
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MEMBERS \
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}; \
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}
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#endif
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