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8454f0e090
[ Upstream commit4e86f32a13] Recently the kernel test robot has reported an ARM-specific BUILD_BUG_ON() in an old and unmaintained wil6210 wireless driver. The problem comes from the structure packing rules of old ARM ABI ('-mabi=apcs-gnu'). For example, the following structure is packed to 18 bytes instead of 16: struct poorly_packed { unsigned int a; unsigned int b; unsigned short c; union { struct { unsigned short d; unsigned int e; } __attribute__((packed)); struct { unsigned short d; unsigned int e; } __attribute__((packed)) inner; }; } __attribute__((packed)); To fit it into 16 bytes, it's required to add packed attribute to the container union as well: struct poorly_packed { unsigned int a; unsigned int b; unsigned short c; union { struct { unsigned short d; unsigned int e; } __attribute__((packed)); struct { unsigned short d; unsigned int e; } __attribute__((packed)) inner; } __attribute__((packed)); } __attribute__((packed)); Thanks to Andrew Pinski of GCC team for sorting the things out at https://gcc.gnu.org/pipermail/gcc/2023-November/242888.html. Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202311150821.cI4yciFE-lkp@intel.com Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> Link: https://lore.kernel.org/r/20231120110607.98956-1-dmantipov@yandex.ru Fixes:50d7bd38c3("stddef: Introduce struct_group() helper macro") Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
48 lines
1.5 KiB
C
48 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef _UAPI_LINUX_STDDEF_H
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#define _UAPI_LINUX_STDDEF_H
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#include <linux/compiler_types.h>
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#ifndef __always_inline
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#define __always_inline inline
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#endif
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/**
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* __struct_group() - Create a mirrored named and anonyomous struct
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*
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* @TAG: The tag name for the named sub-struct (usually empty)
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* @NAME: The identifier name of the mirrored sub-struct
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* @ATTRS: Any struct attributes (usually empty)
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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 layout
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* and size: one anonymous and one named. The former's members can be used
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* normally without sub-struct naming, and the latter can be used to
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* reason about the start, end, and size of the group of struct members.
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* The named struct can also be explicitly tagged for layer reuse, as well
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* as both having struct attributes appended.
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*/
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#define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
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union { \
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struct { MEMBERS } ATTRS; \
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struct TAG { MEMBERS } ATTRS NAME; \
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} ATTRS
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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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struct { \
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struct { } __empty_ ## NAME; \
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TYPE NAME[]; \
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}
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#endif
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