diff --git a/libcutils/Android.bp b/libcutils/Android.bp
index f7b497d..39f8aba 100644
--- a/libcutils/Android.bp
+++ b/libcutils/Android.bp
@@ -18,6 +18,7 @@
 // they correspond to features not used by our host development tools
 // which are also hard or even impossible to port to native Win32
 libcutils_nonwindows_sources = [
+    "android_get_control_file.cpp",
     "fs.c",
     "multiuser.c",
     "socket_inaddr_any_server_unix.c",
@@ -34,7 +35,6 @@
     host_supported: true,
     srcs: [
         "config_utils.c",
-        "files.cpp",
         "fs_config.c",
         "canned_fs_config.c",
         "hashmap.c",
diff --git a/libcutils/android_get_control_env.h b/libcutils/android_get_control_env.h
new file mode 100644
index 0000000..638c831
--- /dev/null
+++ b/libcutils/android_get_control_env.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016 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 __CUTILS_ANDROID_GET_CONTROL_ENV_H
+#define __CUTILS_ANDROID_GET_CONTROL_ENV_H
+
+/* To declare library function hidden and internal */
+#define LIBCUTILS_HIDDEN __attribute__((visibility("hidden")))
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+LIBCUTILS_HIDDEN int __android_get_control_from_env(const char* prefix,
+                                                    const char* name);
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __CUTILS_ANDROID_GET_CONTROL_ENV_H */
diff --git a/libcutils/files.cpp b/libcutils/android_get_control_file.cpp
similarity index 73%
rename from libcutils/files.cpp
rename to libcutils/android_get_control_file.cpp
index bf15b42..496fbbf 100644
--- a/libcutils/files.cpp
+++ b/libcutils/android_get_control_file.cpp
@@ -25,11 +25,6 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-
-// This file contains files implementation that can be shared between
-// platforms as long as the correct headers are included.
-#define _GNU_SOURCE 1 // for asprintf
-
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -41,17 +36,16 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#include <cutils/files.h>
+#include <cutils/android_get_control_file.h>
 
-#ifndef TEMP_FAILURE_RETRY // _WIN32 does not define
-#define TEMP_FAILURE_RETRY(exp) (exp)
-#endif
+#include "android_get_control_env.h"
 
-int android_get_control_file(const char* path) {
-    if (!path) return -1;
+LIBCUTILS_HIDDEN int __android_get_control_from_env(const char* prefix,
+                                                    const char* name) {
+    if (!prefix || !name) return -1;
 
     char *key = NULL;
-    if (asprintf(&key, ANDROID_FILE_ENV_PREFIX "%s", path) < 0) return -1;
+    if (asprintf(&key, "%s%s", prefix, name) < 0) return -1;
     if (!key) return -1;
 
     char *cp = key;
@@ -70,29 +64,33 @@
 
     // validity checking
     if ((fd < 0) || (fd > INT_MAX)) return -1;
-#if defined(_SC_OPEN_MAX)
-    if (fd >= sysconf(_SC_OPEN_MAX)) return -1;
-#elif defined(OPEN_MAX)
-    if (fd >= OPEN_MAX) return -1;
-#elif defined(_POSIX_OPEN_MAX)
-    if (fd >= _POSIX_OPEN_MAX) return -1;
+
+    // Since we are inheriting an fd, it could legitimately exceed _SC_OPEN_MAX
+
+    // Still open?
+#if defined(F_GETFD) // Linux lowest overhead
+    if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFD)) < 0) return -1;
+#elif defined(F_GETFL) // Mac host lowest overhead
+    if (fcntl(fd, F_GETFL) < 0) return -1;
+#else // Hail Mary pass
+    struct stat s;
+    if (fstat(fd, &s) < 0) return -1;
 #endif
 
-#if defined(F_GETFD)
-    if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFD)) < 0) return -1;
-#elif defined(F_GETFL)
-    if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFL)) < 0) return -1;
-#else
-    struct stat s;
-    if (TEMP_FAILURE_RETRY(fstat(fd, &s)) < 0) return -1;
-#endif
+    return static_cast<int>(fd);
+}
+
+int android_get_control_file(const char* path) {
+    int fd = __android_get_control_from_env(ANDROID_FILE_ENV_PREFIX, path);
 
 #if defined(__linux__)
+    // Find file path from /proc and make sure it is correct
     char *proc = NULL;
-    if (asprintf(&proc, "/proc/self/fd/%ld", fd) < 0) return -1;
+    if (asprintf(&proc, "/proc/self/fd/%d", fd) < 0) return -1;
     if (!proc) return -1;
 
     size_t len = strlen(path);
+    // readlink() does not guarantee a nul byte, len+2 so we catch truncation.
     char *buf = static_cast<char *>(calloc(1, len + 2));
     if (!buf) {
         free(proc);
@@ -104,8 +102,8 @@
     free(buf);
     if (ret < 0) return -1;
     if (cmp != 0) return -1;
+    // It is what we think it is
 #endif
 
-    // It is what we think it is
-    return static_cast<int>(fd);
+    return fd;
 }
diff --git a/libcutils/klog.cpp b/libcutils/klog.cpp
index 9d823cf..4bad28a 100644
--- a/libcutils/klog.cpp
+++ b/libcutils/klog.cpp
@@ -24,7 +24,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#include <cutils/files.h>
+#include <cutils/android_get_control_file.h>
 #include <cutils/klog.h>
 
 static int klog_level = KLOG_DEFAULT_LEVEL;
diff --git a/libcutils/sockets.cpp b/libcutils/sockets.cpp
index 63761a2..23a447b 100644
--- a/libcutils/sockets.cpp
+++ b/libcutils/sockets.cpp
@@ -28,33 +28,9 @@
 
 // This file contains socket implementation that can be shared between
 // platforms as long as the correct headers are included.
-#define _GNU_SOURCE 1 // For asprintf
-
-#include <ctype.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <limits.h>
-#if !defined(_WIN32)
-#include <netinet/in.h>
-#endif
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#if !defined(_WIN32)
-#include <sys/un.h>
-#endif
-#include <unistd.h>
-
-#include <string>
 
 #include <cutils/sockets.h>
 
-#ifndef TEMP_FAILURE_RETRY // _WIN32 does not define
-#define TEMP_FAILURE_RETRY(exp) (exp)
-#endif
-
 int socket_get_local_port(cutils_socket_t sock) {
     sockaddr_storage addr;
     socklen_t addr_size = sizeof(addr);
@@ -65,58 +41,3 @@
     }
     return -1;
 }
-
-int android_get_control_socket(const char* name) {
-    char *key = NULL;
-    if (asprintf(&key, ANDROID_SOCKET_ENV_PREFIX "%s", name) < 0) return -1;
-    if (!key) return -1;
-
-    char *cp = key;
-    while (*cp) {
-        if (!isalnum(*cp)) *cp = '_';
-        ++cp;
-    }
-
-    const char* val = getenv(key);
-    free(key);
-    if (!val) return -1;
-
-    errno = 0;
-    long fd = strtol(val, NULL, 10);
-    if (errno) return -1;
-
-    // validity checking
-    if ((fd < 0) || (fd > INT_MAX)) return -1;
-#if defined(_SC_OPEN_MAX)
-    if (fd >= sysconf(_SC_OPEN_MAX)) return -1;
-#elif defined(OPEN_MAX)
-    if (fd >= OPEN_MAX) return -1;
-#elif defined(_POSIX_OPEN_MAX)
-    if (fd >= _POSIX_OPEN_MAX) return -1;
-#endif
-
-#if defined(F_GETFD)
-    if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFD)) < 0) return -1;
-#elif defined(F_GETFL)
-    if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFL)) < 0) return -1;
-#else
-    struct stat s;
-    if (TEMP_FAILURE_RETRY(fstat(fd, &s)) < 0) return -1;
-#endif
-
-#if !defined(_WIN32)
-    struct sockaddr_un addr;
-    socklen_t addrlen = sizeof(addr);
-    int ret = TEMP_FAILURE_RETRY(getsockname(fd, (struct sockaddr *)&addr, &addrlen));
-    if (ret < 0) return -1;
-    char *path = NULL;
-    if (asprintf(&path, ANDROID_SOCKET_DIR"/%s", name) < 0) return -1;
-    if (!path) return -1;
-    int cmp = strcmp(addr.sun_path, path);
-    free(path);
-    if (cmp != 0) return -1;
-#endif
-
-    // It is what we think it is
-    return static_cast<int>(fd);
-}
diff --git a/libcutils/sockets_unix.cpp b/libcutils/sockets_unix.cpp
index 3545403..948d09c 100644
--- a/libcutils/sockets_unix.cpp
+++ b/libcutils/sockets_unix.cpp
@@ -16,13 +16,21 @@
 
 #define LOG_TAG "socket-unix"
 
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
 #include <sys/uio.h>
+#include <sys/un.h>
 #include <time.h>
 #include <unistd.h>
 
 #include <android/log.h>
+#include <cutils/android_get_control_file.h>
 #include <cutils/sockets.h>
 
+#include "android_get_control_env.h"
+
 #if defined(__ANDROID__)
 /* For the socket trust (credentials) check */
 #include <private/android_filesystem_config.h>
@@ -80,3 +88,24 @@
 
     return writev(sock, iovec_buffers, num_buffers);
 }
+
+int android_get_control_socket(const char* name) {
+    int fd = __android_get_control_from_env(ANDROID_SOCKET_ENV_PREFIX, name);
+
+    if (fd < 0) return fd;
+
+    // Compare to UNIX domain socket name, must match!
+    struct sockaddr_un addr;
+    socklen_t addrlen = sizeof(addr);
+    int ret = TEMP_FAILURE_RETRY(getsockname(fd, (struct sockaddr *)&addr, &addrlen));
+    if (ret < 0) return -1;
+    char *path = NULL;
+    if (asprintf(&path, ANDROID_SOCKET_DIR "/%s", name) < 0) return -1;
+    if (!path) return -1;
+    int cmp = strcmp(addr.sun_path, path);
+    free(path);
+    if (cmp != 0) return -1;
+
+    // It is what we think it is
+    return fd;
+}
diff --git a/libcutils/sockets_windows.cpp b/libcutils/sockets_windows.cpp
index ed6b1a7..3064c70 100644
--- a/libcutils/sockets_windows.cpp
+++ b/libcutils/sockets_windows.cpp
@@ -84,3 +84,7 @@
 
     return -1;
 }
+
+int android_get_control_socket(const char* name) {
+    return -1;
+}
diff --git a/libcutils/tests/Android.bp b/libcutils/tests/Android.bp
index bd35412..72e2eac 100644
--- a/libcutils/tests/Android.bp
+++ b/libcutils/tests/Android.bp
@@ -14,7 +14,7 @@
 
 cc_defaults {
     name: "libcutils_test_default",
-    srcs: ["sockets_test.cpp", "files_test.cpp"],
+    srcs: ["sockets_test.cpp"],
 
     target: {
         android: {
@@ -28,7 +28,11 @@
         },
 
         not_windows: {
-            srcs: ["test_str_parms.cpp"],
+            srcs: [
+                "test_str_parms.cpp",
+                "android_get_control_socket_test.cpp",
+                "android_get_control_file_test.cpp"
+            ],
         },
     },
 
diff --git a/libcutils/tests/android_get_control_file_test.cpp b/libcutils/tests/android_get_control_file_test.cpp
new file mode 100644
index 0000000..6c6fd2a
--- /dev/null
+++ b/libcutils/tests/android_get_control_file_test.cpp
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#include <ctype.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <time.h>
+
+#include <string>
+
+#include <android-base/stringprintf.h>
+#include <android-base/test_utils.h>
+#include <cutils/android_get_control_file.h>
+#include <gtest/gtest.h>
+
+TEST(FilesTest, android_get_control_file) {
+    TemporaryFile tf;
+    ASSERT_GE(tf.fd, 0);
+
+    std::string key(ANDROID_FILE_ENV_PREFIX);
+    key += tf.path;
+
+    std::for_each(key.begin(), key.end(), [] (char& c) { c = isalnum(c) ? c : '_'; });
+
+    EXPECT_EQ(unsetenv(key.c_str()), 0);
+    EXPECT_EQ(android_get_control_file(tf.path), -1);
+
+    EXPECT_EQ(setenv(key.c_str(), android::base::StringPrintf("%d", tf.fd).c_str(), true), 0);
+
+    EXPECT_EQ(android_get_control_file(tf.path), tf.fd);
+    close(tf.fd);
+    EXPECT_EQ(android_get_control_file(tf.path), -1);
+    EXPECT_EQ(unsetenv(key.c_str()), 0);
+    EXPECT_EQ(android_get_control_file(tf.path), -1);
+}
diff --git a/libcutils/tests/android_get_control_socket_test.cpp b/libcutils/tests/android_get_control_socket_test.cpp
new file mode 100644
index 0000000..e586748
--- /dev/null
+++ b/libcutils/tests/android_get_control_socket_test.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <time.h>
+
+#include <cutils/sockets.h>
+#include <gtest/gtest.h>
+
+#ifndef SOCK_NONBLOCK
+#define SOCK_NONBLOCK 0
+#endif
+
+#ifndef SOCK_CLOEXEC
+#define SOCK_CLOEXEC 0
+#endif
+
+TEST(SocketsTest, android_get_control_socket) {
+    static const char key[] = ANDROID_SOCKET_ENV_PREFIX "SocketsTest_android_get_control_socket";
+    static const char* name = key + strlen(ANDROID_SOCKET_ENV_PREFIX);
+
+    EXPECT_EQ(unsetenv(key), 0);
+    EXPECT_EQ(android_get_control_socket(name), -1);
+
+    int fd;
+    ASSERT_GE(fd = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0), 0);
+#ifdef F_GETFL
+    int flags;
+    ASSERT_GE(flags = fcntl(fd, F_GETFL), 0);
+    ASSERT_GE(fcntl(fd, F_SETFL, flags | O_NONBLOCK), 0);
+#endif
+    EXPECT_EQ(android_get_control_socket(name), -1);
+
+    struct sockaddr_un addr;
+    memset(&addr, 0, sizeof(addr));
+    addr.sun_family = AF_UNIX;
+    snprintf(addr.sun_path, sizeof(addr.sun_path), ANDROID_SOCKET_DIR"/%s", name);
+    unlink(addr.sun_path);
+
+    EXPECT_EQ(bind(fd, (struct sockaddr*)&addr, sizeof(addr)), 0);
+    EXPECT_EQ(android_get_control_socket(name), -1);
+
+    char val[32];
+    snprintf(val, sizeof(val), "%d", fd);
+    EXPECT_EQ(setenv(key, val, true), 0);
+
+    EXPECT_EQ(android_get_control_socket(name), fd);
+    socket_close(fd);
+    EXPECT_EQ(android_get_control_socket(name), -1);
+    EXPECT_EQ(unlink(addr.sun_path), 0);
+    EXPECT_EQ(android_get_control_socket(name), -1);
+    EXPECT_EQ(unsetenv(key), 0);
+    EXPECT_EQ(android_get_control_socket(name), -1);
+}
diff --git a/libcutils/tests/files_test.cpp b/libcutils/tests/files_test.cpp
deleted file mode 100644
index 1a7d673..0000000
--- a/libcutils/tests/files_test.cpp
+++ /dev/null
@@ -1,46 +0,0 @@
-/*
- * Copyright (C) 2016 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.
- */
-
-#include <fcntl.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <sys/types.h>
-#include <time.h>
-
-#include <cutils/files.h>
-#include <gtest/gtest.h>
-
-TEST(FilesTest, android_get_control_file) {
-    static const char key[] = ANDROID_FILE_ENV_PREFIX "_dev_kmsg";
-    static const char name[] = "/dev/kmsg";
-
-    EXPECT_EQ(unsetenv(key), 0);
-    EXPECT_EQ(android_get_control_file(name), -1);
-
-    int fd;
-    ASSERT_GE(fd = open(name, O_RDONLY | O_CLOEXEC), 0);
-    EXPECT_EQ(android_get_control_file(name), -1);
-
-    char val[32];
-    snprintf(val, sizeof(val), "%d", fd);
-    EXPECT_EQ(setenv(key, val, true), 0);
-
-    EXPECT_EQ(android_get_control_file(name), fd);
-    close(fd);
-    EXPECT_EQ(android_get_control_file(name), -1);
-    EXPECT_EQ(unsetenv(key), 0);
-    EXPECT_EQ(android_get_control_file(name), -1);
-}
diff --git a/libcutils/tests/sockets_test.cpp b/libcutils/tests/sockets_test.cpp
index adfbf4a..0441fb6 100644
--- a/libcutils/tests/sockets_test.cpp
+++ b/libcutils/tests/sockets_test.cpp
@@ -18,11 +18,9 @@
 // IPv6 capabilities. These tests assume that no UDP packets are lost, which
 // should be the case for loopback communication, but is not guaranteed.
 
-#include <stdio.h>
-#include <stdlib.h>
+#include <string.h>
 #include <sys/socket.h>
 #include <sys/types.h>
-#include <sys/un.h>
 #include <time.h>
 
 #include <cutils/sockets.h>
@@ -189,49 +187,3 @@
 TEST(SocketsTest, TestSocketSendBuffersFailure) {
     EXPECT_EQ(-1, socket_send_buffers(INVALID_SOCKET, nullptr, 0));
 }
-
-#ifndef SOCK_NONBLOCK
-#define SOCK_NONBLOCK 0
-#endif
-
-#ifndef SOCK_CLOEXEC
-#define SOCK_CLOEXEC 0
-#endif
-
-TEST(SocketsTest, android_get_control_socket) {
-    static const char key[] = ANDROID_SOCKET_ENV_PREFIX "SocketsTest_android_get_control_socket";
-    static const char* name = key + strlen(ANDROID_SOCKET_ENV_PREFIX);
-
-    EXPECT_EQ(unsetenv(key), 0);
-    EXPECT_EQ(android_get_control_socket(name), -1);
-
-    int fd;
-    ASSERT_GE(fd = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0), 0);
-#ifdef F_GETFL
-    int flags;
-    ASSERT_GE(flags = fcntl(fd, F_GETFL), 0);
-    ASSERT_GE(fcntl(fd, F_SETFL, flags | O_NONBLOCK), 0);
-#endif
-    EXPECT_EQ(android_get_control_socket(name), -1);
-
-    struct sockaddr_un addr;
-    memset(&addr, 0, sizeof(addr));
-    addr.sun_family = AF_UNIX;
-    snprintf(addr.sun_path, sizeof(addr.sun_path), ANDROID_SOCKET_DIR"/%s", name);
-    unlink(addr.sun_path);
-
-    EXPECT_EQ(bind(fd, (struct sockaddr*)&addr, sizeof(addr)), 0);
-    EXPECT_EQ(android_get_control_socket(name), -1);
-
-    char val[32];
-    snprintf(val, sizeof(val), "%d", fd);
-    EXPECT_EQ(setenv(key, val, true), 0);
-
-    EXPECT_EQ(android_get_control_socket(name), fd);
-    socket_close(fd);
-    EXPECT_EQ(android_get_control_socket(name), -1);
-    EXPECT_EQ(unlink(addr.sun_path), 0);
-    EXPECT_EQ(android_get_control_socket(name), -1);
-    EXPECT_EQ(unsetenv(key), 0);
-    EXPECT_EQ(android_get_control_socket(name), -1);
-}