#include <linux/compiler.h>
#include <linux/limits.h>
+#include <linux/const.h>
/*
* We need to compute the minimum and maximum values representable in a given
}))
/**
- * array_size() - Calculate size of 2-dimensional array.
- *
- * @a: dimension one
- * @b: dimension two
+ * size_mul() - Calculate size_t multiplication with saturation at SIZE_MAX
*
- * Calculates size of 2-dimensional array: @a * @b.
+ * @factor1: first factor
+ * @factor2: second factor
*
- * Returns: number of bytes needed to represent the array or SIZE_MAX on
- * overflow.
+ * Returns: calculate @factor1 * @factor2, both promoted to size_t,
+ * with any overflow causing the return value to be SIZE_MAX. The
+ * lvalue must be size_t to avoid implicit type conversion.
*/
-static inline __must_check size_t array_size(size_t a, size_t b)
+static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
{
size_t bytes;
- if (check_mul_overflow(a, b, &bytes))
+ if (check_mul_overflow(factor1, factor2, &bytes))
return SIZE_MAX;
return bytes;
}
/**
- * array3_size() - Calculate size of 3-dimensional array.
+ * size_add() - Calculate size_t addition with saturation at SIZE_MAX
*
- * @a: dimension one
- * @b: dimension two
- * @c: dimension three
- *
- * Calculates size of 3-dimensional array: @a * @b * @c.
+ * @addend1: first addend
+ * @addend2: second addend
*
- * Returns: number of bytes needed to represent the array or SIZE_MAX on
- * overflow.
+ * Returns: calculate @addend1 + @addend2, both promoted to size_t,
+ * with any overflow causing the return value to be SIZE_MAX. The
+ * lvalue must be size_t to avoid implicit type conversion.
*/
-static inline __must_check size_t array3_size(size_t a, size_t b, size_t c)
+static inline size_t __must_check size_add(size_t addend1, size_t addend2)
{
size_t bytes;
- if (check_mul_overflow(a, b, &bytes))
- return SIZE_MAX;
- if (check_mul_overflow(bytes, c, &bytes))
+ if (check_add_overflow(addend1, addend2, &bytes))
return SIZE_MAX;
return bytes;
}
-/*
- * Compute a*b+c, returning SIZE_MAX on overflow. Internal helper for
- * struct_size() below.
+/**
+ * size_sub() - Calculate size_t subtraction with saturation at SIZE_MAX
+ *
+ * @minuend: value to subtract from
+ * @subtrahend: value to subtract from @minuend
+ *
+ * Returns: calculate @minuend - @subtrahend, both promoted to size_t,
+ * with any overflow causing the return value to be SIZE_MAX. For
+ * composition with the size_add() and size_mul() helpers, neither
+ * argument may be SIZE_MAX (or the result with be forced to SIZE_MAX).
+ * The lvalue must be size_t to avoid implicit type conversion.
*/
-static inline __must_check size_t __ab_c_size(size_t a, size_t b, size_t c)
+static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
{
size_t bytes;
- if (check_mul_overflow(a, b, &bytes))
- return SIZE_MAX;
- if (check_add_overflow(bytes, c, &bytes))
+ if (minuend == SIZE_MAX || subtrahend == SIZE_MAX ||
+ check_sub_overflow(minuend, subtrahend, &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.
- * @count: Number of elements in the array.
+ * array_size() - Calculate size of 2-dimensional array.
*
- * Calculates size of memory needed for structure @p followed by an
- * array of @count number of @member elements.
+ * @a: dimension one
+ * @b: dimension two
*
- * Return: number of bytes needed or SIZE_MAX on overflow.
+ * Calculates size of 2-dimensional array: @a * @b.
+ *
+ * Returns: number of bytes needed to represent the array or SIZE_MAX on
+ * overflow.
*/
-#define struct_size(p, member, count) \
- __ab_c_size(count, \
- sizeof(*(p)->member) + __must_be_array((p)->member),\
- sizeof(*(p)))
+#define array_size(a, b) size_mul(a, b)
+
+/**
+ * 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.
+ */
+#define array3_size(a, b, c) size_mul(size_mul(a, b), c)
/**
* flex_array_size() - Calculate size of a flexible array member
* Return: number of bytes needed or SIZE_MAX on overflow.
*/
#define flex_array_size(p, member, count) \
- array_size(count, \
- sizeof(*(p)->member) + __must_be_array((p)->member))
+ __builtin_choose_expr(__is_constexpr(count), \
+ (count) * sizeof(*(p)->member) + __must_be_array((p)->member), \
+ size_mul(count, sizeof(*(p)->member) + __must_be_array((p)->member)))
+
+/**
+ * struct_size() - Calculate size of structure with trailing flexible array.
+ *
+ * @p: Pointer to the structure.
+ * @member: Name of the array member.
+ * @count: Number of elements in the array.
+ *
+ * Calculates size of memory needed for structure @p followed by an
+ * array of @count number of @member elements.
+ *
+ * Return: number of bytes needed or SIZE_MAX on overflow.
+ */
+#define struct_size(p, member, count) \
+ __builtin_choose_expr(__is_constexpr(count), \
+ sizeof(*(p)) + flex_array_size(p, member, count), \
+ size_add(sizeof(*(p)), flex_array_size(p, member, count)))
#endif /* __LINUX_OVERFLOW_H */
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