Add new DECLARE_SIZED_FLEX() helper to set the default size of a flexible-array member. The code is identical to the declaration in __DEFINE_FLEX() which has also been changed to use DECLARE_SIZED_FLEX().
Add DECLARE_COUNTED_FLEX_ARRAY() helper which is a variant of DECLARE_FLEX_ARRAY() with a counted-by attribute. Also add default sized variants of DECLARE_FLEX_ARRAY(), DECLARE_SIZED_FLEX(), and DECLARE_COUNTED_FLEX_ARRAY(), DECLARE_COUNTED_SIZED_FLEX(). Signed-off-by: Jesse Taube <[email protected]> --- include/linux/overflow.h | 58 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 54 insertions(+), 4 deletions(-) diff --git a/include/linux/overflow.h b/include/linux/overflow.h index a8cb6319b4fb..a3384cae49e5 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -464,6 +464,59 @@ static __always_inline size_t __must_check size_sub(size_t minuend, size_t subtr */ #define struct_offset(p, member) (offsetof(typeof(*(p)), member)) +/** + * __DECLARE_SIZED_FLEX() - helper macro for DECLARE_SIZED_FLEX() family. + * Allows for easily declaring a structure with a trailing flexible array member + * to have a specific size. + * + * @obj: object to be given a specific size + * @name: Name of the array member. + * @count: Number of elements in the array; must be compile-time const. + */ +#define __DECLARE_SIZED_FLEX(obj, name, count) \ + _Static_assert(__builtin_constant_p(count), \ + "default sized flex array members require compile-time const count"); \ + union { \ + u8 bytes[struct_size_t(obj, name, count)]; \ + obj; \ + } + +/** + * DECLARE_COUNTED_FLEX_ARRAY() - Declare a counted flexible array + * + * @type: Type name. + * @name: Name of the array member. + * @counter: Name of the __counted_by member. + */ +#define DECLARE_COUNTED_FLEX_ARRAY(type, name, counter)\ + struct { \ + size_t counter; \ + type name[] __counted_by(counter); \ + } + +/** + * DECLARE_SIZED_FLEX() - Declare a structure with a trailing flexible array + * member with a default size. + * + * @type: Type name. + * @name: Name of the array member. + * @count: Number of elements in the array; must be compile-time const. + */ +#define DECLARE_SIZED_FLEX(type, name, count) \ + __DECLARE_SIZED_FLEX(type name[], name, count) + +/** + * DECLARE_COUNTED_SIZED_FLEX() - Declare a structure with a trailing flexible + * array member counted by count, with a default size. + * + * @type: Type name. + * @name: Name of the array member. + * @counter: Name of the __counted_by member. + * @count: Number of elements in the array; must be compile-time const. + */ +#define DECLARE_COUNTED_SIZED_FLEX(type, name, counter, count) \ + __DECLARE_SIZED_FLEX(DECLARE_COUNTED_FLEX_ARRAY(type, name, counter), name, count) + /** * __DEFINE_FLEX() - helper macro for DEFINE_FLEX() family. * Enables caller macro to pass arbitrary trailing expressions @@ -477,10 +530,7 @@ static __always_inline size_t __must_check size_sub(size_t minuend, size_t subtr #define __DEFINE_FLEX(type, name, member, count, trailer...) \ _Static_assert(__builtin_constant_p(count), \ "onstack flex array members require compile-time const count"); \ - union { \ - u8 bytes[struct_size_t(type, member, count)]; \ - type obj; \ - } name##_u trailer; \ + __DECLARE_SIZED_FLEX(type obj, member, count) name##_u trailer; \ type *name = (type *)&name##_u /** -- 2.54.0
