Android Pre-installing NDK Application

We are trying to pre-install a NDK Application into the /system/app directory. If I open the apk file in a ZIP file manager, the .so file is inside the lib directory. However, when we preinstall the apk file, the apk's .so file is not copied to system/lib directory, causing for the application to fail when we launched it in the device.

Can anyone please tell me what should be set in the Android.mk for the APK file so that the .so file will be extracted from the APK file and copied to system/lib directory? We need to include the application in the system image.

Any feedback will be grea开发者_如何学运维tly appreciated.

Thanks, artsylar

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I had the same need and after 2 days of heavy research, I came up with a solution to this problem. It is not simple and requires you to be able to modify the Android System code as well.

Basically PackageManagerService prevents system applications to unpack their native binaries (.so files), unless they have been updated. So the only way to fix this is by modifying PMS.java (aptly named since trying to solve this problem put me in a terrible mood).

On the system's first boot, I check every system package for native binaries by writing a isPackageNative(PackageParser.Package pkg) function:

    private boolean isPackageNative(PackageParser.Package pkg) throws IOException {
    final ZipFile zipFile = new ZipFile(pkg.mPath);
    final Enumeration<? extends ZipEntry> privateZipEntries = zipFile.entries();
    while (privateZipEntries.hasMoreElements()) {
        final ZipEntry zipEntry = privateZipEntries.nextElement();
        final String zipEntryName = zipEntry.getName();
        if(true) Log.e(TAG, "    Zipfile entry:"+zipEntryName);
        if (zipEntryName.endsWith(".so")) {
            zipFile.close();
            return true;
        }
    }
    zipFile.close();
    return false;
  }

This function checks every package for a native library and if it has one, I unpack it. PMS does this check in scanPackageLI(....). Search for the following code in the method:

   if (isSystemApp(pkg) && !isUpdatedSystemApp(pkg))

and add the isPackageNative(pkg) check. There are other small modifications required but you'll probably figure it out once you have this direction. Hope it helps!

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I think you cannot do it by default as Android's /system partition is mounted as read-only! You need a rooted phone so as to mount the /system with write privileges through this command:

mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system.

So, if you have a rooted phone you can add in your application this code:

Process p;  
try {  
    // Preform su to get root privledges
    p = Runtime.getRuntime().exec("su");
    // Attempt to write a file to a root-only  
    DataOutputStream os = new DataOutputStream(p.getOutputStream()); 
    // gain root privileges 
    os.writeBytes("mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system\n");
    // do here the copy operation you want in /system/lib file, for example:
    os.writeBytes("mv /sdcard/mylib.so /system/lib/\n");

     // Close the terminal  
     os.writeBytes("exit\n");  
     os.flush();  

 } catch (IOException e) {  
    toastMessage("could not get root access");  
 }

Otherwise, you have to follow the solution that digitalmouse12 gave..

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You will have to "adb push" the .so file yourself. Also, you don't necessarily have to push your library into system/lib (the folder might deny you permission anyway). Most push it to data/app and then load by issuing

System.load("/data/app/<libName>.so");

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There's probably documentation somewhere, but if you cannot find that, I would suggest identifying a pre-installed app with an associated jni library .so and examining the android sources or corresponding system image or update.zip to see how it's handled.

In other words, programming by example...