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| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2025-06-17 22:05:36 +0300 |
|---|---|---|
| committer | Kees Cook <kees@kernel.org> | 2025-06-19 00:30:53 +0300 |
| commit | 29bb79e9dbf1ba100125e39deb7147acd490903f (patch) | |
| tree | 247c540fe8a4ec7a83669f75c752aa80fffe968e /include/linux | |
| parent | 4bfbc2691de8c869339090e851703209b17ba378 (diff) | |
| download | linux-29bb79e9dbf1ba100125e39deb7147acd490903f.tar.xz | |
stddef: Introduce TRAILING_OVERLAP() helper macro
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>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/stddef.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/include/linux/stddef.h b/include/linux/stddef.h index 929d67710cc5..dab49e2ec8c0 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 |