diff --git a/libc/bionic/lockf.cpp b/libc/bionic/lockf.cpp
new file mode 100644
index 0000000..1510b3d
--- /dev/null
+++ b/libc/bionic/lockf.cpp
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * 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 THE COPYRIGHT HOLDERS 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
+ * COPYRIGHT OWNER 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 <unistd.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+
+int lockf64(int fd, int cmd, off64_t length) {
+  // Translate POSIX lockf into fcntl.
+  struct flock fl;
+  memset(&fl, 0, sizeof(fl));
+  fl.l_whence = SEEK_CUR;
+  fl.l_start = 0;
+  fl.l_len = length;
+
+  if (cmd == F_ULOCK) {
+    fl.l_type = F_UNLCK;
+    cmd = F_SETLK64;
+    return fcntl(fd, F_SETLK64, &fl);
+  }
+
+  if (cmd == F_LOCK) {
+    fl.l_type = F_WRLCK;
+    return fcntl(fd, F_SETLKW64, &fl);
+  }
+
+  if (cmd == F_TLOCK) {
+    fl.l_type = F_WRLCK;
+    return fcntl(fd, F_SETLK64, &fl);
+  }
+
+  if (cmd == F_TEST) {
+    fl.l_type = F_RDLCK;
+    if (fcntl(fd, F_GETLK64, &fl) == -1) return -1;
+    if (fl.l_type == F_UNLCK || fl.l_pid == getpid()) return 0;
+    errno = EACCES;
+    return -1;
+  }
+
+  errno = EINVAL;
+  return -1;
+}
+
+int lockf(int fd, int cmd, off_t length) {
+  return lockf64(fd, cmd, length);
+}