From: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Add shift_overflow() helper to help driver authors to ensure that
shift operand doesn't cause to overflow, which is very common pattern
for RDMA drivers.
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
---
include/linux/overflow.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 8712ff70995f..2a3395248e94 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -202,6 +202,29 @@
#endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
+/**
+ * shift_overflow() - Peform shift operation with overflow check
+ * @a: value to be shifted
+ * @b: shift operand
+ *
+ * Checks if a << b will overflow
+ *
+ * Returns: result of shift for no overflow or SIZE_MAX for overflow
+ */
+static inline __must_check size_t shift_overflow(size_t a, size_t b)
+{
+ size_t c, res;
+
+ if (b >= sizeof(size_t) * BITS_PER_BYTE)
+ return SIZE_MAX;
+
+ c = (size_t)1 << b;
+ if (check_mul_overflow(a, c, &res))
+ return SIZE_MAX;
+
+ return res;
+}
+
/**
* array_size() - Calculate size of 2-dimensional array.
*
--
2.14.4
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