Index: lib/libc/string/bzero.3
===================================================================
--- lib/libc/string/bzero.3
+++ lib/libc/string/bzero.3
@@ -62,9 +62,9 @@
 .Pp
 The
 .Fn explicit_bzero
-variant behaves the same, but will not be removed by a compiler's dead store
-optimization pass, making it useful for clearing sensitive memory such as a
-password.
+variant is the same, but has correct flags to force the call to occur,
+no matter if the compiler thinks it is pointless, or not, making it 
+useful for clearing sensitive memory such as a password.
 .Sh SEE ALSO
 .Xr memset 3 ,
 .Xr swab 3
Index: sys/libkern/explicit_bzero.c
===================================================================
--- sys/libkern/explicit_bzero.c
+++ sys/libkern/explicit_bzero.c
@@ -2,6 +2,8 @@
 /*
  * Public domain.
  * Written by Matthew Dempsky.
+ *
+ * reworked by Jim Thompson <jim@netgate.com>
  */
 
 #include <sys/cdefs.h>
@@ -13,6 +15,40 @@
 #include <string.h>
 #endif /* _KERNEL */
 
+#if __clang__
+	/*
+	 * http://clang.llvm.org/docs/LanguageExtensions.html#feature-checking-macros
+	 * http://lists.cs.uiuc.edu/pipermail/cfe-dev/2014-December/040627.html
+	 */
+	#if __has_attribute( noinline ) /* && __has_attribute( optnone ) */
+		#define NOOPT /* __attribute__ (( optnone )) */
+		#define NOINLINE __attribute__ (( noinline ))
+	#endif
+#elif __GNUC__
+	/*
+	 * http://gcc.gnu.org/onlinedocs/gcc/Function-Specific-Option-Pragmas.html
+	 * http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
+	 */
+	#if __GNUC__ > 4 || ( __GNUC__ == 4 && __GNUC_MINOR__ >= 4 )
+		#define NOOPT __attribute__ (( optimize( 0 ) ))
+		#define NOINLINE __attribute__ (( noinline ))
+	#endif
+#endif
+
+#if defined(NOOPT) && defined(NOINLINE)
+NOOPT NOINLINE void
+explicit_bzero(void *buf, size_t len)
+{
+	size_t i;
+	unsigned char *p = buf;
+
+	for (i = 0; i < len; i++) {
+		p[i] = 0;
+	}
+}
+
+#else
+
 __attribute__((weak)) void __explicit_bzero_hook(void *, size_t);
 
 __attribute__((weak)) void
@@ -26,3 +62,4 @@
 	memset(buf, 0, len);
 	__explicit_bzero_hook(buf, len);
 }
+#endif