--- zzzz-none-000/linux-4.9.218/include/linux/overflow.h	2020-04-02 15:20:41.000000000 +0000
+++ seale-7590ax-750/linux-4.9.218/include/linux/overflow.h	2023-03-29 10:59:07.000000000 +0000
@@ -202,4 +202,108 @@
 
 #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
 
+/** check_shl_overflow() - Calculate a left-shifted value and check overflow
+ *
+ * @a: Value to be shifted
+ * @s: How many bits left to shift
+ * @d: Pointer to where to store the result
+ *
+ * Computes *@d = (@a << @s)
+ *
+ * Returns true if '*d' cannot hold the result or when 'a << s' doesn't
+ * make sense. Example conditions:
+ * - 'a << s' causes bits to be lost when stored in *d.
+ * - 's' is garbage (e.g. negative) or so large that the result of
+ *   'a << s' is guaranteed to be 0.
+ * - 'a' is negative.
+ * - 'a << s' sets the sign bit, if any, in '*d'.
+ *
+ * '*d' will hold the results of the attempted shift, but is not
+ * considered "safe for use" if false is returned.
+ */
+#define check_shl_overflow(a, s, d) ({					\
+	typeof(a) _a = a;						\
+	typeof(s) _s = s;						\
+	typeof(d) _d = d;						\
+	u64 _a_full = _a;						\
+	unsigned int _to_shift =					\
+		_s >= 0 && _s < 8 * sizeof(*d) ? _s : 0;		\
+	*_d = (_a_full << _to_shift);					\
+	(_to_shift != _s || *_d < 0 || _a < 0 ||			\
+		(*_d >> _to_shift) != _a);				\
+})
+
+/**
+ * array_size() - Calculate size of 2-dimensional array.
+ *
+ * @a: dimension one
+ * @b: dimension two
+ *
+ * Calculates size of 2-dimensional array: @a * @b.
+ *
+ * Returns: number of bytes needed to represent the array or SIZE_MAX on
+ * overflow.
+ */
+static inline __must_check size_t array_size(size_t a, size_t b)
+{
+	size_t bytes;
+
+	if (check_mul_overflow(a, b, &bytes))
+		return SIZE_MAX;
+
+	return bytes;
+}
+
+/**
+ * array3_size() - Calculate size of 3-dimensional array.
+ *
+ * @a: dimension one
+ * @b: dimension two
+ * @c: dimension three
+ *
+ * Calculates size of 3-dimensional array: @a * @b * @c.
+ *
+ * Returns: number of bytes needed to represent the array or SIZE_MAX on
+ * overflow.
+ */
+static inline __must_check size_t array3_size(size_t a, size_t b, size_t c)
+{
+	size_t bytes;
+
+	if (check_mul_overflow(a, b, &bytes))
+		return SIZE_MAX;
+	if (check_mul_overflow(bytes, c, &bytes))
+		return SIZE_MAX;
+
+	return bytes;
+}
+
+static inline __must_check size_t __ab_c_size(size_t n, size_t size, size_t c)
+{
+	size_t bytes;
+
+	if (check_mul_overflow(n, size, &bytes))
+		return SIZE_MAX;
+	if (check_add_overflow(bytes, c, &bytes))
+		return SIZE_MAX;
+
+	return bytes;
+}
+
+/**
+ * struct_size() - Calculate size of structure with trailing array.
+ * @p: Pointer to the structure.
+ * @member: Name of the array member.
+ * @n: Number of elements in the array.
+ *
+ * Calculates size of memory needed for structure @p followed by an
+ * array of @n @member elements.
+ *
+ * Return: number of bytes needed or SIZE_MAX on overflow.
+ */
+#define struct_size(p, member, n)					\
+	__ab_c_size(n,							\
+		    sizeof(*(p)->member) + __must_be_array((p)->member),\
+		    sizeof(*(p)))
+
 #endif /* __LINUX_OVERFLOW_H */