1 files changed, 46 insertions, 19 deletions

diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 659045046468..ef74051d5cfe 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -3,6 +3,7 @@
 #define __LINUX_OVERFLOW_H
 
 #include <linux/compiler.h>
+#include <linux/limits.h>
 
 /*
  * In the fallback code below, we need to compute the minimum and
@@ -43,6 +44,16 @@
 #define is_non_negative(a) ((a) > 0 || (a) == 0)
 #define is_negative(a) (!(is_non_negative(a)))
 
+/*
+ * Allows for effectively applying __must_check to a macro so we can have
+ * both the type-agnostic benefits of the macros while also being able to
+ * enforce that the return value is, in fact, checked.
+ */
+static inline bool __must_check __must_check_overflow(bool overflow)
+{
+	return unlikely(overflow);
+}
+
 #ifdef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW
 /*
  * For simplicity and code hygiene, the fallback code below insists on
@@ -52,32 +63,32 @@
  * alias for __builtin_add_overflow, but add type checks similar to
  * below.
  */
-#define check_add_overflow(a, b, d) ({		\
+#define check_add_overflow(a, b, d) __must_check_overflow(({	\
 	typeof(a) __a = (a);			\
 	typeof(b) __b = (b);			\
 	typeof(d) __d = (d);			\
 	(void) (&__a == &__b);			\
 	(void) (&__a == __d);			\
 	__builtin_add_overflow(__a, __b, __d);	\
-})
+}))
 
-#define check_sub_overflow(a, b, d) ({		\
+#define check_sub_overflow(a, b, d) __must_check_overflow(({	\
 	typeof(a) __a = (a);			\
 	typeof(b) __b = (b);			\
 	typeof(d) __d = (d);			\
 	(void) (&__a == &__b);			\
 	(void) (&__a == __d);			\
 	__builtin_sub_overflow(__a, __b, __d);	\
-})
+}))
 
-#define check_mul_overflow(a, b, d) ({		\
+#define check_mul_overflow(a, b, d) __must_check_overflow(({	\
 	typeof(a) __a = (a);			\
 	typeof(b) __b = (b);			\
 	typeof(d) __d = (d);			\
 	(void) (&__a == &__b);			\
 	(void) (&__a == __d);			\
 	__builtin_mul_overflow(__a, __b, __d);	\
-})
+}))
 
 #else
 
@@ -190,21 +201,20 @@
 })
 
 
-#define check_add_overflow(a, b, d)					\
+#define check_add_overflow(a, b, d)	__must_check_overflow(		\
 	__builtin_choose_expr(is_signed_type(typeof(a)),		\
 			__signed_add_overflow(a, b, d),			\
-			__unsigned_add_overflow(a, b, d))
+			__unsigned_add_overflow(a, b, d)))
 
-#define check_sub_overflow(a, b, d)					\
+#define check_sub_overflow(a, b, d)	__must_check_overflow(		\
 	__builtin_choose_expr(is_signed_type(typeof(a)),		\
 			__signed_sub_overflow(a, b, d),			\
-			__unsigned_sub_overflow(a, b, d))
+			__unsigned_sub_overflow(a, b, d)))
 
-#define check_mul_overflow(a, b, d)					\
+#define check_mul_overflow(a, b, d)	__must_check_overflow(		\
 	__builtin_choose_expr(is_signed_type(typeof(a)),		\
 			__signed_mul_overflow(a, b, d),			\
-			__unsigned_mul_overflow(a, b, d))
-
+			__unsigned_mul_overflow(a, b, d)))
 
 #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
 
@@ -227,7 +237,7 @@
  * '*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) ({					\
+#define check_shl_overflow(a, s, d) __must_check_overflow(({		\
 	typeof(a) _a = a;						\
 	typeof(s) _s = s;						\
 	typeof(d) _d = d;						\
@@ -237,7 +247,7 @@
 	*_d = (_a_full << _to_shift);					\
 	(_to_shift != _s || is_negative(*_d) || is_negative(_a) ||	\
 	(*_d >> _to_shift) != _a);					\
-})
+}))
 
 /**
  * array_size() - Calculate size of 2-dimensional array.
@@ -304,16 +314,33 @@ static inline __must_check size_t __ab_c_size(size_t a, size_t b, size_t c)
  * 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.
+ * @count: Number of elements in the array.
  *
  * Calculates size of memory needed for structure @p followed by an
- * array of @n @member elements.
+ * array of @count number of @member elements.
  *
  * Return: number of bytes needed or SIZE_MAX on overflow.
  */
-#define struct_size(p, member, n)					\
-	__ab_c_size(n,							\
+#define struct_size(p, member, count)					\
+	__ab_c_size(count,						\
 		    sizeof(*(p)->member) + __must_be_array((p)->member),\
 		    sizeof(*(p)))
 
+/**
+ * flex_array_size() - Calculate size of a flexible array member
+ *                     within an enclosing structure.
+ *
+ * @p: Pointer to the structure.
+ * @member: Name of the flexible array member.
+ * @count: Number of elements in the array.
+ *
+ * Calculates size of a flexible array of @count number of @member
+ * elements, at the end of structure @p.
+ *
+ * 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))
+
 #endif /* __LINUX_OVERFLOW_H */