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4e86f32a13
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>
59 lines
1.8 KiB
C
59 lines
1.8 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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#ifdef __cplusplus
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/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
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#define __DECLARE_FLEX_ARRAY(T, member) \
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T member[0]
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#else
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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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#ifndef __counted_by
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#define __counted_by(m)
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#endif
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#endif /* _UAPI_LINUX_STDDEF_H */
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