Commit bd1ebf24 authored by Kees Cook's avatar Kees Cook
Browse files

overflow: Allow non-type arg to type_max() and type_min() 

A common use of type_max() is to find the max for the type of a
variable. Using the pattern type_max(typeof(var)) is needlessly
verbose. Instead, since typeof(type) == type we can just explicitly
call typeof() on the argument to type_max() and type_min(). Add
wrappers for readability.

We can do some replacements right away:

$ git grep '\btype_\(min\|max\)(typeof' | wc -l
11

Link: https://lore.kernel.org/r/20240301062221.work.840-kees@kernel.org


Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent e606e4b7

include/linux/overflow.h

+7 −5
Original line number Diff line number Diff line
@@ -31,8 +31,10 @@ 
 * credit to Christian Biere.

 */

#define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type)))

#define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T)))

#define type_min(T) ((T)((T)-type_max(T)-(T)1))

#define __type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T)))

#define type_max(t)	__type_max(typeof(t))

#define __type_min(T) ((T)((T)-type_max(T)-(T)1))

#define type_min(t)	__type_min(typeof(t))



/*

 * Avoids triggering -Wtype-limits compilation warning,
@@ -207,10 +209,10 @@ static inline bool __must_check __must_check_overflow(bool overflow) 


#define __overflows_type_constexpr(x, T) (			\

	is_unsigned_type(typeof(x)) ?				\

		(x) > type_max(typeof(T)) :			\

		(x) > type_max(T) :				\

	is_unsigned_type(typeof(T)) ?				\

		(x) < 0 || (x) > type_max(typeof(T)) :		\

	(x) < type_min(typeof(T)) || (x) > type_max(typeof(T)))

		(x) < 0 || (x) > type_max(T) :			\

	(x) < type_min(T) || (x) > type_max(T))



#define __overflows_type(x, T)		({	\

	typeof(T) v = 0;			\