Index: head/sys/compat/linuxkpi/common/include/linux/overflow.h
===================================================================
--- head/sys/compat/linuxkpi/common/include/linux/overflow.h
+++ head/sys/compat/linuxkpi/common/include/linux/overflow.h
@@ -0,0 +1,52 @@
+/*-
+ * Copyright (c) 2020 The FreeBSD Foundation
+ *
+ * This software was developed by Emmanuel Vadot under sponsorship
+ * from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef __LINUX_OVERFLOW_H__
+#define	__LINUX_OVERFLOW_H__
+
+#ifndef	__has_builtin
+#define	__has_builtin(x)	0
+#endif
+
+#if __has_builtin(__builtin_add_overflow)
+#define check_add_overflow(a, b, c)		\
+	__builtin_add_overflow(a, b, c)
+#else
+#error "Compiler does not support __builtin_add_overflow"
+#endif
+
+#if __has_builtin(__builtin_mul_overflow)
+#define check_mul_overflow(a, b, c)	\
+	__builtin_mul_overflow(a, b, c)
+#else
+#error "Compiler does not support __builtin_mul_overflow"
+#endif
+
+#endif	/* __LINUX_OVERFLOW_H__ */