Add new TRAILING_OVERLAP() helper macro to create a union between a flexible-array member (FAM) in a struct and a set of additional members that would otherwise follow it.
Co-developed-by: Kees Cook <[email protected]> Signed-off-by: Kees Cook <[email protected]> Signed-off-by: Gustavo A. R. Silva <[email protected]> --- include/linux/stddef.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/include/linux/stddef.h b/include/linux/stddef.h index 929d67710cc5..635513ff2829 100644 --- a/include/linux/stddef.h +++ b/include/linux/stddef.h @@ -93,4 +93,24 @@ enum { #define DECLARE_FLEX_ARRAY(TYPE, NAME) \ __DECLARE_FLEX_ARRAY(TYPE, NAME) +/** + * TRAILING_OVERLAP() - Overlap a flexible-array member with trailing members. + * + * Creates a union between a flexible-array member (FAM) in a struct and a set + * of additional members that would otherwise follow it. + * + * @TYPE: Flexible structure type name, including "struct" keyword. + * @NAME: Name for a variable to define. + * @FAM: The flexible-array member within @TYPE + * @MEMBERS: Trailing overlapping members. + */ +#define TRAILING_OVERLAP(TYPE, NAME, FAM, MEMBERS) \ + union { \ + TYPE NAME; \ + struct { \ + unsigned char __offset_to_fam[offsetof(TYPE, FAM)]; \ + MEMBERS \ + }; \ + } + #endif -- 2.43.0
