Commit 190faecf authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Kees Cook
Browse files

overflow: Add STACK_FLEX_ARRAY_SIZE() helper 



Add new STACK_FLEX_ARRAY_SIZE() helper to get the size of a
flexible-array member defined using DEFINE_FLEX()/DEFINE_RAW_FLEX()
at compile time.

This is essentially the same as ARRAY_SIZE() but for on-stack
flexible-array members.

Signed-off-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/83d53744e11c80eb3f03765238cbe648855f4168.1745355442.git.gustavoars@kernel.org


Signed-off-by: default avatarKees Cook <kees@kernel.org>
parent ccf1d2b4

include/linux/overflow.h

+15 −0
Original line number Diff line number Diff line
@@ -420,6 +420,8 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend) 
 * flexible array member.

 * Use __struct_size(@name) to get compile-time size of it afterwards.

 * Use __member_size(@name->member) to get compile-time size of @name members.

 * Use STACK_FLEX_ARRAY_SIZE(@name, @member) to get compile-time number of

 * elements in array @member.

 */

#define DEFINE_RAW_FLEX(type, name, member, count)	\

	_DEFINE_FLEX(type, name, member, count, = {})
@@ -438,8 +440,21 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend) 
 * flexible array member.

 * Use __struct_size(@NAME) to get compile-time size of it afterwards.

 * Use __member_size(@NAME->member) to get compile-time size of @NAME members.

 * Use STACK_FLEX_ARRAY_SIZE(@name, @member) to get compile-time number of

 * elements in array @member.

 */

#define DEFINE_FLEX(TYPE, NAME, MEMBER, COUNTER, COUNT)	\

	_DEFINE_FLEX(TYPE, NAME, MEMBER, COUNT, = { .obj.COUNTER = COUNT, })



/**

 * STACK_FLEX_ARRAY_SIZE() - helper macro for DEFINE_FLEX() family.

 * Returns the number of elements in @array.

 *

 * @name: Name for a variable defined in DEFINE_RAW_FLEX()/DEFINE_FLEX().

 * @array: Name of the array member.

 */

#define STACK_FLEX_ARRAY_SIZE(name, array)						\

	(__member_size((name)->array) / sizeof(*(name)->array) +			\

						__must_be_array((name)->array))



#endif /* __LINUX_OVERFLOW_H */