diff --git a/libc/bionic/dirname_r.c b/libc/bionic/dirname_r.c
new file mode 100644
index 0000000..df2e9bf
--- /dev/null
+++ b/libc/bionic/dirname_r.c
@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2008 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 <libgen.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/param.h>
+
+int
+dirname_r(const char*  path, char*  buffer, size_t  bufflen)
+{
+    const char *endp;
+    int         result, len;
+
+    /* Empty or NULL string gets treated as "." */
+    if (path == NULL || *path == '\0') {
+        path = ".";
+        len  = 1;
+        goto Exit;
+    }
+
+    /* Strip trailing slashes */
+    endp = path + strlen(path) - 1;
+    while (endp > path && *endp == '/')
+        endp--;
+
+    /* Find the start of the dir */
+    while (endp > path && *endp != '/')
+        endp--;
+
+    /* Either the dir is "/" or there are no slashes */
+    if (endp == path) {
+        path = (*endp == '/') ? "/" : ".";
+        len  = 1;
+        goto Exit;
+    }
+
+    do {
+        endp--;
+    } while (endp > path && *endp == '/');
+
+    len = endp - path +1;
+
+Exit:
+    result = len;
+    if (len+1 > MAXPATHLEN) {
+        errno = ENAMETOOLONG;
+        return -1;
+    }
+    if (buffer == NULL)
+        return result;
+
+    if (len > (int)bufflen-1) {
+        len    = (int)bufflen-1;
+        result = -1;
+        errno  = ERANGE;
+    }
+
+    if (len >= 0) {
+        memcpy( buffer, path, len );
+        buffer[len] = 0;
+    }
+    return result;
+}