Index: sys/libkern/explicit_bzero.c
===================================================================
--- sys/libkern/explicit_bzero.c
+++ sys/libkern/explicit_bzero.c
@@ -1,28 +1,42 @@
-/*	$OpenBSD: explicit_bzero.c,v 1.3 2014/06/21 02:34:26 matthew Exp $ */
-/*
- * Public domain.
- * Written by Matthew Dempsky.
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (C) 2018 Rubicon Communications, LLC (Netgate) All Rights Reserved.
+ *
+ * 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 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 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.
  */
-
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");

 #ifdef _KERNEL
 #include <sys/libkern.h>
 #else
 #include <string.h>
 #endif /* _KERNEL */

-__attribute__((weak)) void __explicit_bzero_hook(void *, size_t);
-
-__attribute__((weak)) void
-__explicit_bzero_hook(void *buf, size_t len)
-{
-}
-
 void
 explicit_bzero(void *buf, size_t len)
 {
 	memset(buf, 0, len);
-	__explicit_bzero_hook(buf, len);
+	__asm__ __volatile__("" ::"r"(buf): "memory");
 }
+