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: Kees Cook <keescook@chromium.org>

diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index bc390f0261288c7ebda6088cc9e1c3a957e63146..aa691f2119b0bbc8c3be7739c857f2f89775d784 100644 (file)
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -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;                        \