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-rw-r--r--include/linux/overflow.h47
1 files changed, 47 insertions, 0 deletions
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 1d3be1a2204c..0e33b5cbdb9f 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -128,6 +128,53 @@ static inline bool __must_check __must_check_overflow(bool overflow)
(*_d >> _to_shift) != _a); \
}))
+#define __overflows_type_constexpr(x, T) ( \
+ is_unsigned_type(typeof(x)) ? \
+ (x) > type_max(typeof(T)) : \
+ is_unsigned_type(typeof(T)) ? \
+ (x) < 0 || (x) > type_max(typeof(T)) : \
+ (x) < type_min(typeof(T)) || (x) > type_max(typeof(T)))
+
+#define __overflows_type(x, T) ({ \
+ typeof(T) v = 0; \
+ check_add_overflow((x), v, &v); \
+})
+
+/**
+ * overflows_type - helper for checking the overflows between value, variables,
+ * or data type
+ *
+ * @n: source constant value or variable to be checked
+ * @T: destination variable or data type proposed to store @x
+ *
+ * Compares the @x expression for whether or not it can safely fit in
+ * the storage of the type in @T. @x and @T can have different types.
+ * If @x is a constant expression, this will also resolve to a constant
+ * expression.
+ *
+ * Returns: true if overflow can occur, false otherwise.
+ */
+#define overflows_type(n, T) \
+ __builtin_choose_expr(__is_constexpr(n), \
+ __overflows_type_constexpr(n, T), \
+ __overflows_type(n, T))
+
+/**
+ * castable_to_type - like __same_type(), but also allows for casted literals
+ *
+ * @n: variable or constant value
+ * @T: variable or data type
+ *
+ * Unlike the __same_type() macro, this allows a constant value as the
+ * first argument. If this value would not overflow into an assignment
+ * of the second argument's type, it returns true. Otherwise, this falls
+ * back to __same_type().
+ */
+#define castable_to_type(n, T) \
+ __builtin_choose_expr(__is_constexpr(n), \
+ !__overflows_type_constexpr(n, T), \
+ __same_type(n, T))
+
/**
* size_mul() - Calculate size_t multiplication with saturation at SIZE_MAX
* @factor1: first factor