diff --git a/libc/upstream-netbsd/README.txt b/libc/upstream-netbsd/README.txt
new file mode 100644
index 0000000..86af6eb
--- /dev/null
+++ b/libc/upstream-netbsd/README.txt
@@ -0,0 +1,9 @@
+This directory contains upstream NetBSD source. You should not edit these
+files directly. Make fixes upstream and then pull down the new version of
+the file.
+
+Note that code in the other 'netbsd' directory contains Android modifications.
+We should work towards getting as many of those changes as possible upstream
+and then losing those files in favor of pure upstream copies here instead.
+
+TODO: write a script to make this process automated.
diff --git a/libc/upstream-netbsd/libc/string/strxfrm.c b/libc/upstream-netbsd/libc/string/strxfrm.c
new file mode 100644
index 0000000..42c2a24
--- /dev/null
+++ b/libc/upstream-netbsd/libc/string/strxfrm.c
@@ -0,0 +1,70 @@
+/*	$NetBSD: strxfrm.c,v 1.12 2012/06/25 22:32:46 abs Exp $	*/
+
+/*-
+ * Copyright (c) 1990, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * 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.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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>
+#if defined(LIBC_SCCS) && !defined(lint)
+#if 0
+static char sccsid[] = "@(#)strxfrm.c	8.1 (Berkeley) 6/4/93";
+#else
+__RCSID("$NetBSD: strxfrm.c,v 1.12 2012/06/25 22:32:46 abs Exp $");
+#endif
+#endif /* LIBC_SCCS and not lint */
+
+#include <assert.h>
+#include <string.h>
+
+/*
+ * Transform src, storing the result in dst, such that
+ * strcmp() on transformed strings returns what strcoll()
+ * on the original untransformed strings would return.
+ */
+size_t
+strxfrm(char *dst, const char *src, size_t n)
+{
+	size_t srclen, copysize;
+
+	_DIAGASSERT(src != NULL);
+
+	/*
+	 * Since locales are unimplemented, this is just a copy.
+	 */
+	srclen = strlen(src);
+	if (n != 0) {
+		_DIAGASSERT(dst != NULL);
+		copysize = srclen < n ? srclen : n - 1;
+		(void)memcpy(dst, src, copysize);
+		dst[copysize] = 0;
+	}
+	return (srclen);
+}
diff --git a/libc/upstream-netbsd/netbsd-compat.h b/libc/upstream-netbsd/netbsd-compat.h
new file mode 100644
index 0000000..a52052a
--- /dev/null
+++ b/libc/upstream-netbsd/netbsd-compat.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _BIONIC_NETBSD_COMPAT_H_included
+#define _BIONIC_NETBSD_COMPAT_H_included
+
+// NetBSD uses _DIAGASSERT to null-check arguments and the like.
+#include <assert.h>
+#define _DIAGASSERT(e) ((e) ? (void) 0 : __assert2(__FILE__, __LINE__, __func__, #e))
+
+#endif