diff --git a/libc/Android.mk b/libc/Android.mk
index 4470efa..b033790 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -11,7 +11,6 @@
 	unistd/exec.c \
 	unistd/fnmatch.c \
 	unistd/getopt_long.c \
-	unistd/popen.c \
 	unistd/syslog.c \
 	unistd/system.c \
 	unistd/time.c \
@@ -326,6 +325,7 @@
     upstream-netbsd/libc/gen/ftw.c \
     upstream-netbsd/libc/gen/nftw.c \
     upstream-netbsd/libc/gen/nice.c \
+    upstream-netbsd/libc/gen/popen.c \
     upstream-netbsd/libc/gen/psignal.c \
     upstream-netbsd/libc/gen/setjmperr.c \
     upstream-netbsd/libc/gen/utime.c \
diff --git a/libc/unistd/popen.c b/libc/unistd/popen.c
deleted file mode 100644
index c2355c1..0000000
--- a/libc/unistd/popen.c
+++ /dev/null
@@ -1,164 +0,0 @@
-/*	$OpenBSD: popen.c,v 1.17 2005/08/08 08:05:34 espie Exp $ */
-/*
- * Copyright (c) 1988, 1993
- *	The Regents of the University of California.  All rights reserved.
- *
- * This code is derived from software written by Ken Arnold and
- * published in UNIX Review, Vol. 6, No. 8.
- *
- * 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/param.h>
-#include <sys/wait.h>
-
-#include <signal.h>
-#include <errno.h>
-#include <unistd.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <paths.h>
-
-static struct pid {
-	struct pid *next;
-	FILE *fp;
-	pid_t pid;
-} *pidlist;
-
-extern char **environ;
-
-FILE *
-popen(const char *program, const char *type)
-{
-	struct pid * volatile cur;
-	FILE *iop;
-	int pdes[2];
-	pid_t pid;
-	char *argp[] = {"sh", "-c", NULL, NULL};
-
-	if ((*type != 'r' && *type != 'w') || type[1] != '\0') {
-		errno = EINVAL;
-		return (NULL);
-	}
-
-	if ((cur = malloc(sizeof(struct pid))) == NULL)
-		return (NULL);
-
-	if (pipe(pdes) < 0) {
-		free(cur);
-		return (NULL);
-	}
-
-	switch (pid = fork()) {
-	case -1:			/* Error. */
-		(void)close(pdes[0]);
-		(void)close(pdes[1]);
-		free(cur);
-		return (NULL);
-		/* NOTREACHED */
-	case 0:				/* Child. */
-	    {
-		struct pid *pcur;
-		/*
-		 * We fork()'d, we got our own copy of the list, no
-		 * contention.
-		 */
-		for (pcur = pidlist; pcur; pcur = pcur->next)
-			close(fileno(pcur->fp));
-
-		if (*type == 'r') {
-			(void) close(pdes[0]);
-			if (pdes[1] != STDOUT_FILENO) {
-				(void)dup2(pdes[1], STDOUT_FILENO);
-				(void)close(pdes[1]);
-			}
-		} else {
-			(void)close(pdes[1]);
-			if (pdes[0] != STDIN_FILENO) {
-				(void)dup2(pdes[0], STDIN_FILENO);
-				(void)close(pdes[0]);
-			}
-		}
-		argp[2] = (char *)program;
-		execve(_PATH_BSHELL, argp, environ);
-		_exit(127);
-		/* NOTREACHED */
-	    }
-	}
-
-	/* Parent; assume fdopen can't fail. */
-	if (*type == 'r') {
-		iop = fdopen(pdes[0], type);
-		(void)close(pdes[1]);
-	} else {
-		iop = fdopen(pdes[1], type);
-		(void)close(pdes[0]);
-	}
-
-	/* Link into list of file descriptors. */
-	cur->fp = iop;
-	cur->pid =  pid;
-	cur->next = pidlist;
-	pidlist = cur;
-
-	return (iop);
-}
-
-/*
- * pclose --
- *	Pclose returns -1 if stream is not associated with a `popened' command,
- *	if already `pclosed', or waitpid returns an error.
- */
-int
-pclose(FILE *iop)
-{
-	struct pid *cur, *last;
-	int pstat;
-	pid_t pid;
-
-	/* Find the appropriate file pointer. */
-	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
-		if (cur->fp == iop)
-			break;
-
-	if (cur == NULL)
-		return (-1);
-
-	(void)fclose(iop);
-
-	do {
-		pid = waitpid(cur->pid, &pstat, 0);
-	} while (pid == -1 && errno == EINTR);
-
-	/* Remove the entry from the linked list. */
-	if (last == NULL)
-		pidlist = cur->next;
-	else
-		last->next = cur->next;
-	free(cur);
-
-	return (pid == -1 ? -1 : pstat);
-}
diff --git a/libc/upstream-netbsd/env.h b/libc/upstream-netbsd/env.h
new file mode 100644
index 0000000..8f99f9d
--- /dev/null
+++ b/libc/upstream-netbsd/env.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2013 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_ENV_H_included
+#define _BIONIC_NETBSD_ENV_H_included
+
+/* Placeholder. */
+
+#endif
diff --git a/libc/upstream-netbsd/libc/gen/popen.c b/libc/upstream-netbsd/libc/gen/popen.c
new file mode 100644
index 0000000..593e346
--- /dev/null
+++ b/libc/upstream-netbsd/libc/gen/popen.c
@@ -0,0 +1,227 @@
+/*	$NetBSD: popen.c,v 1.32 2012/06/25 22:32:43 abs Exp $	*/
+
+/*
+ * Copyright (c) 1988, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software written by Ken Arnold and
+ * published in UNIX Review, Vol. 6, No. 8.
+ *
+ * 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[] = "@(#)popen.c	8.3 (Berkeley) 5/3/95";
+#else
+__RCSID("$NetBSD: popen.c,v 1.32 2012/06/25 22:32:43 abs Exp $");
+#endif
+#endif /* LIBC_SCCS and not lint */
+
+#include "namespace.h"
+#include <sys/param.h>
+#include <sys/wait.h>
+#include <sys/socket.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <paths.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "env.h"
+#include "reentrant.h"
+
+#ifdef __weak_alias
+__weak_alias(popen,_popen)
+__weak_alias(pclose,_pclose)
+#endif
+
+static struct pid {
+	struct pid *next;
+	FILE *fp;
+#ifdef _REENTRANT
+	int fd;
+#endif
+	pid_t pid;
+} *pidlist; 
+	
+#ifdef _REENTRANT
+static rwlock_t pidlist_lock = RWLOCK_INITIALIZER;
+#endif
+
+FILE *
+popen(const char *command, const char *type)
+{
+	struct pid *cur, *old;
+	FILE *iop;
+	const char * volatile xtype = type;
+	int pdes[2], pid, serrno;
+	volatile int twoway;
+	int flags;
+
+	_DIAGASSERT(command != NULL);
+	_DIAGASSERT(xtype != NULL);
+
+	flags = strchr(xtype, 'e') ? O_CLOEXEC : 0;
+	if (strchr(xtype, '+')) {
+		int stype = flags ? (SOCK_STREAM | SOCK_CLOEXEC) : SOCK_STREAM;
+		twoway = 1;
+		xtype = "r+";
+		if (socketpair(AF_LOCAL, stype, 0, pdes) < 0)
+			return NULL;
+	} else  {
+		twoway = 0;
+		xtype = strrchr(xtype, 'r') ? "r" : "w";
+		if (pipe2(pdes, flags) == -1)
+			return NULL;
+	}
+
+	if ((cur = malloc(sizeof(struct pid))) == NULL) {
+		(void)close(pdes[0]);
+		(void)close(pdes[1]);
+		errno = ENOMEM;
+		return (NULL);
+	}
+
+	(void)rwlock_rdlock(&pidlist_lock);
+	(void)__readlockenv();
+	switch (pid = vfork()) {
+	case -1:			/* Error. */
+		serrno = errno;
+		(void)__unlockenv();
+		(void)rwlock_unlock(&pidlist_lock);
+		free(cur);
+		(void)close(pdes[0]);
+		(void)close(pdes[1]);
+		errno = serrno;
+		return (NULL);
+		/* NOTREACHED */
+	case 0:				/* Child. */
+		/* POSIX.2 B.3.2.2 "popen() shall ensure that any streams
+		   from previous popen() calls that remain open in the 
+		   parent process are closed in the new child process. */
+		for (old = pidlist; old; old = old->next)
+#ifdef _REENTRANT
+			close(old->fd); /* don't allow a flush */
+#else
+			close(fileno(old->fp)); /* don't allow a flush */
+#endif
+
+		if (*xtype == 'r') {
+			(void)close(pdes[0]);
+			if (pdes[1] != STDOUT_FILENO) {
+				(void)dup2(pdes[1], STDOUT_FILENO);
+				(void)close(pdes[1]);
+			}
+			if (twoway)
+				(void)dup2(STDOUT_FILENO, STDIN_FILENO);
+		} else {
+			(void)close(pdes[1]);
+			if (pdes[0] != STDIN_FILENO) {
+				(void)dup2(pdes[0], STDIN_FILENO);
+				(void)close(pdes[0]);
+			}
+		}
+
+		execl(_PATH_BSHELL, "sh", "-c", command, NULL);
+		_exit(127);
+		/* NOTREACHED */
+	}
+	(void)__unlockenv();
+
+	/* Parent; assume fdopen can't fail. */
+	if (*xtype == 'r') {
+		iop = fdopen(pdes[0], xtype);
+#ifdef _REENTRANT
+		cur->fd = pdes[0];
+#endif
+		(void)close(pdes[1]);
+	} else {
+		iop = fdopen(pdes[1], xtype);
+#ifdef _REENTRANT
+		cur->fd = pdes[1];
+#endif
+		(void)close(pdes[0]);
+	}
+
+	/* Link into list of file descriptors. */
+	cur->fp = iop;
+	cur->pid =  pid;
+	cur->next = pidlist;
+	pidlist = cur;
+	(void)rwlock_unlock(&pidlist_lock);
+
+	return (iop);
+}
+
+/*
+ * pclose --
+ *	Pclose returns -1 if stream is not associated with a `popened' command,
+ *	if already `pclosed', or waitpid returns an error.
+ */
+int
+pclose(FILE *iop)
+{
+	struct pid *cur, *last;
+	int pstat;
+	pid_t pid;
+
+	_DIAGASSERT(iop != NULL);
+
+	rwlock_wrlock(&pidlist_lock);
+
+	/* Find the appropriate file pointer. */
+	for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
+		if (cur->fp == iop)
+			break;
+	if (cur == NULL) {
+		(void)rwlock_unlock(&pidlist_lock);
+		return (-1);
+	}
+
+	(void)fclose(iop);
+
+	/* Remove the entry from the linked list. */
+	if (last == NULL)
+		pidlist = cur->next;
+	else
+		last->next = cur->next;
+
+	(void)rwlock_unlock(&pidlist_lock);
+
+	do {
+		pid = waitpid(cur->pid, &pstat, 0);
+	} while (pid == -1 && errno == EINTR);
+
+	free(cur);
+
+	return (pid == -1 ? -1 : pstat);
+}
diff --git a/libc/upstream-netbsd/netbsd-compat.h b/libc/upstream-netbsd/netbsd-compat.h
index 3833c1d..e33885e 100644
--- a/libc/upstream-netbsd/netbsd-compat.h
+++ b/libc/upstream-netbsd/netbsd-compat.h
@@ -24,4 +24,13 @@
 // TODO: update our <sys/cdefs.h> to support this properly.
 #define __type_fit(t, a) (0 == 0)
 
+// TODO: our 2.6 emulator kernels don't support SOCK_CLOEXEC yet, so we have to do without.
+#define SOCK_CLOEXEC 0
+
+#define _GNU_SOURCE
+
+// TODO: we don't yet have thread-safe environment variables.
+#define __readlockenv() 0
+#define __unlockenv() 0
+
 #endif
diff --git a/libc/upstream-netbsd/reentrant.h b/libc/upstream-netbsd/reentrant.h
index a4381d4..e2945da 100644
--- a/libc/upstream-netbsd/reentrant.h
+++ b/libc/upstream-netbsd/reentrant.h
@@ -17,9 +17,22 @@
 #ifndef _BIONIC_NETBSD_REENTRANT_H_included
 #define _BIONIC_NETBSD_REENTRANT_H_included
 
+#define _REENTRANT
+
 #include <pthread.h>
 #include <signal.h>
 
-// Placeholder.
+//
+// Map NetBSD libc internal locking to pthread locking.
+//
+
+#define MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
+#define mutex_t pthread_mutex_t
+
+#define RWLOCK_INITIALIZER PTHREAD_RWLOCK_INITIALIZER
+#define rwlock_t pthread_rwlock_t
+#define rwlock_rdlock pthread_rwlock_rdlock
+#define rwlock_unlock pthread_rwlock_unlock
+#define rwlock_wrlock pthread_rwlock_wrlock
 
 #endif