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overflow: Add STACK_FLEX_ARRAY_SIZE() helper

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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: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/83d53744e11c80eb3f03765238cbe648855f4168.1745355442.git.gustavoars@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Gustavo A. R. Silva
2025-04-22 15:05:18 -06:00
committed by Kees Cook
parent ccf1d2b4a1
commit 190faecf64
1 changed files with 15 additions and 0 deletions
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15
include/linux/overflow.h
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@@ -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 */