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-rw-r--r--include/linux/overflow.h35
1 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index f9b60313eaea..7b5cf4a5cd19 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -309,4 +309,39 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
#define struct_size_t(type, member, count) \
struct_size((type *)NULL, member, count)
+/**
+ * _DEFINE_FLEX() - helper macro for DEFINE_FLEX() family.
+ * Enables caller macro to pass (different) initializer.
+ *
+ * @type: structure type name, including "struct" keyword.
+ * @name: Name for a variable to define.
+ * @member: Name of the array member.
+ * @count: Number of elements in the array; must be compile-time const.
+ * @initializer: initializer expression (could be empty for no init).
+ */
+#define _DEFINE_FLEX(type, name, member, count, initializer) \
+ _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 initializer; \
+ type *name = (type *)&name##_u
+
+/**
+ * DEFINE_FLEX() - Define an on-stack instance of structure with a trailing
+ * flexible array member.
+ *
+ * @type: structure type name, including "struct" keyword.
+ * @name: Name for a variable to define.
+ * @member: Name of the array member.
+ * @count: Number of elements in the array; must be compile-time const.
+ *
+ * Define a zeroed, on-stack, instance of @type structure with a trailing
+ * flexible array member.
+ * Use __struct_size(@name) to get compile-time size of it afterwards.
+ */
+#define DEFINE_FLEX(type, name, member, count) \
+ _DEFINE_FLEX(type, name, member, count, = {})
+
#endif /* __LINUX_OVERFLOW_H */