Running a native library on Android L. error: only position independent executables (PIE) are supported

Question

When I run native code on Android L (Nexus 5), I get the error.

error: only position independent executables (PIE) are supported.

<

Answer 1

The Chromium project released a wrapper that allows PIE binaries to run on pre-JB Android releases. Note that your PIE executable requires a few extra flags to make this work:

CFLAGS += -fvisibility=default -fPIE
LDFLAGS += -rdynamic -fPIE -pie

In my case, I was shipping ~2MB binaries for 3 architectures and did not want to add 6MB of uncompressed data to the APK just to continue supporting ICS. run_pie is extremely tiny (6-7kB) so it fit the bill.

run_pie should not be built with the PIE flags, and it should not be executed on Android 5.0+ (because, of course, non-PIE binaries are banned). Unfortunately it cannot be built statically because it needs to be linked with -ldl and NDK only provides a shared version of that library.

The Java side could look something like:

String dir = mContext.getFilesDir().getPath();
String command = dir + "/busybox netstat";
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
    command = dir + "/run_pie " + command;
}

where busybox is a PIE executable and lives in the app's private files directory.

See also: earlier discussions of this topic here and here.

Edit JFDee: In my case, I kept getting the error "dlopen() failed: Cannot load library" when running run_pie with my PIE executable. I had to explicitly set LD_LIBRARY_PATH to the directory the executable resided in, i.e. the current path.

In that case the amended example code line of the "run_pie" call would look like this:

...
    command = "LD_LIBRARY_PATH=. " + dir + "/run_pie " + command;
...