add explicit_bzero from musl

include/string.h

@@ -344,6 +344,7 @@ extern void __bzero (void *__s, size_t __n) __THROW __nonnull ((1));
 #endif
 
 #ifdef __USE_BSD
+extern void explicit_bzero (void *__d, size_t __n);
 # ifdef __UCLIBC_SUSV3_LEGACY__
 /* Copy N bytes of SRC to DEST (like memmove, but args reversed).  */
 extern void bcopy (const void *__src, void *__dest, size_t __n)

libc/string/explicit_bzero.c

@@ -0,0 +1,30 @@
+/*
+Copyright © 2005-2020 Rich Felker, et al.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+#define _BSD_SOURCE
+#include <string.h>
+
+void explicit_bzero(void *d, size_t n)
+{
+	d = memset(d, 0, n);
+	__asm__ __volatile__ ("" : : "r"(d) : "memory");
+}