Develop Reference

android - system app jni library load path

If android installed at below path:
/system/product/priv-app/mynative/app-debug.apk
And this apk contains a jni library:
app-debug/lib/arm64-v8a/libnative-lib.so
Where is the path android to load the library libnative-lib.so? I search device and never find that so file.

The answer might be: "it never was on the filesystem to begin with".
Modern Android build infrastructure sets extractNativeLibraries=false by default. This keeps the .so in the APK instead of having a copy linger on your device.
EDIT: I did some source digging, the Android runtime linker can open libraries directly from zip files if the filename contains !/. I think this would just show up as another mapping of the APK in /proc/pid/maps, but I did not investigate beyond that (eg how relocation is done in this case or what namespaces have to do with it).

Why does my Android app look for /data/app/package_name-1/lib/arm/libLibrary.so instead of using the folder armeabi

I get this in logcat when trying to load a library compiled only for armeabi (assuming that it is the fallback for all arm* abis).
08-14 09:43:51.516 7486-7486/package_name E/art﹕ dlopen("/data/app/package_name-1/lib/arm/libLibrary.so", RTLD_LAZY) failed: dlopen failed: unknown reloc type 160 # 0xa3725ab4 (82108)
Due to practical constraints, I cannot test this on a rooted device, so all I know is that the /data/data/package_name folder has a symlink lib -> /data/app/package_name-1/lib/arm
I know that this is not a device specific problem, since I have used native libraries earlier on the same device (with a different app, but same architecture earlier).
Can someone help me out here? Really confused on what exactly is happening.
I use gradle build (Android Studio), and the libLibrary.so is present inside the lib/armeabi folder within the apk on unzipping it.

The question was only partially correct. The true problem was with the relocation type (of which I had no idea initially).
Relocation errors usually occur when the loader and the object file do not understand the same format.
In this case, the .so file was built with c++_static instead of gnustl_static. Android/NDK provides most c++11 functionality, but some of them are not fully operational/functional like std::to_string which led me to try c++_static.
Hope this helps someone else out there who still has hairs left on his/her head.

Error while mapping shared library

I'm trying to debug my Android app (I'm using the libdash library through NDK) as a native application, and I'm having this error:
Error while mapping shared library sections:
`/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/amd64/libjpeg.so': not in executable format: File format not recognized
warning: Could not load shared library symbols for 92 libraries, e.g. /system/bin/linker.
Use the "info sharedlibrary" command to see the complete listing.
Do you need "set solib-search-path" or "set sysroot"?
warning: Unable to find dynamic linker breakpoint function.
GDB will retry eventurally. Meanwhile, it is likely
that GDB is unable to debug shared library initializers
or resolve pending breakpoints after dlopen().
this is the library that i'm trying to use
http://www.bitmovin.net/libdash/

http://mindtherobot.com/blog/452/android-beginners-ndk-setup-step-by-step/
Follow these directions. You need to take the library and put it somewhere special.

Your issue appears to be that you are cross compiling for Android, yet you haven't set your shared library lookup path. The result is that gdb is looking in your host system path to find the shared libraries instead.
Your host system is the system you run the build of your code on (your PC probably). Your target system is the system you're going to run the resulting "executable" on (some Android device). That's why it's called cross compiling. Since the two systems aren't the same, you need to make sure you're using a cross compiled version of gdb (one that knows your target and host types), which was probably provided with the Android SDK, and you also need to make sure you set the search path for the shared libraries.
You should check the general GDB documentation for details, but the method I prefer for setting my cross-compiled library paths is to set the solib-absolute-path. You can do that by running the following from within GDB:
(gdb) set solib-absolute-path <path to root directory all Android shared libraries are under>
This requires that you have the same directory structure as your Android file system with regard to library paths somewhere on your PC.
An alternate and more portable way of doing it is to set the solib-search-path so it will search the Android library locations within the SDK on your PC rather than your PC's default library search path, but for details on that you'll have to read the GDB documentation since I don't use it often enough to help much more.

Using openssl-fips-2.0 shared libraries in Android

I was able to follow directions in this question to build a shared lib of openssl for Android.
E.g.
cd openssl-fips-2.0/
./config
make
make install
And
cd openssl-1.0.1c/
./config fips --with-fipsdir=/usr/local/ssl/fips-2.0/ shared
make depend
make
This generates libcrypto.so.1.0.0 and libssl.so.1.0.0 with corresponding symbolic links to them as libcrypto.so and libssl.so.
Since the NDK build system doesn't support versioned shared libraries I had to use the symbolic links (with PREBUILT_SHARED_LIBRARY). However, with this, the libraries end up getting to the device as libcrypto.so and libssl.so instead of as libcrypto.so.1.0.0 and libssl.so.1.0.0 causing my library to fail to load as it is looking for the libraries with the version names.
The linked question mentions loading the libraries with System.load(libcrypto.so.1.0.0) instead of with System.loadLibrary() but I have not been able to get this to work even with full paths since as mentioned earlier, the file is copied to the device as libcrypto.so.
Anyone done this successfully?
Note: I've also tried modifying the openssl-1.0.1c config and makefiles to generate libcrypto.1.0.0.so (e.g. with the version number before the extension in the filename and soname) and this allowed me to get around the previous loading issue. However, with that I get an error when I try to turn on FIPS mode with FIPS_module_mode_set (FIPS_R_FINGERPRINT_DOES_NOT_MATCH).
I don't know yet why that is happening, but it could be due to NDK stripping of 'unneeded' stuff (see this question)... I'm still looking at this as well but if someone has some info on this as well it would be MUCH appreciated.

Let us identify the problem correctly. It's likely not the NDK build that causes problems, and definitely not the linker which strips away unused entries when it builds a shared lib from static lib.
First of all, I am not sure you can deliver FIPS mode in a usual APK, without rebuilding or at least rooting Android (see for example http://gcn.com/articles/2010/12/23/android-fips-security.aspx).
There is no problem for System.load() to load a versioned .so when you a) specify the full path correctly (e.g. System.load("/data/local/tmp/libssl.so.1.0.0")) and b) the file is delivered to that path. For the first tests, I would suggest to manually upload libcrypto.so.1.0.0 and libssl.so.1.0.0 to /sdcard/ and see if FIPS fingerprint becomes happier.
If the location on /sdcard/ causes any problem, you can try /data/local/ or /data/local/tmp/. You can also use /data/data/(your package)/files/. The latter has one advantage: it will be automatically deleted by the system when your app is uninstalled.
To make a versioned .so (like libcrypto.so.1.0.0) part of your APK, copy it to the assets folder of your project. It will be responsibility of your Java code to copy it from there to the designated location on disk. Make sure this Java code handles correctly upgrades and SD card swaps.

Building/finding shared libraries from Android source code

I wish to back port the Android RTP APIs introduced in version 3.1(Honeycomb) to earlier versions. I downloaded the source of version 4.0 and found that it these APIs had both java and native code. In order to build the native code with the NDK, certain shared libraries are required.
According the Android.mk file, these are libnativehelper, libcutils, libutils, and libmedia. Though the source of all of these are present in the source code, building them was difficult. Each required many other shared libraries. For eg, libmedia requires these shared libraries: libui, libcutils, libutils, libbinder, libsonivox, libicuuc, libexpat, libcamera_client, libstagefright_foundation, libgui and libdl.
So my question is, is there some way of obtaining the original 4 shared libs? Does it involve building the entire source?

Say I need to build a piece of native code which is going to use standard Android shared libraries such as libutils, libcutlis, libmedia. I would perform following steps:
Install AOSP repository with target version.
Add my source code to appropriate directories under ./frameworks/base. In your case it might be easier to create a separate folder and put proper Android.mk of course.
You might get compile errors if required functions from those standard shared libraries are not present in the previous version.
When you build the code as part of AOSP it will build required libraries and link them for you automatically.
P.S. To accomplish that you're better to use a Linux-based build host.

using cygwin terminal, build native part i.e. jni folder. To build using cygwin, goto jni folder using cygdrive command. Then type ndk-build. After successful completion, shared libraries i.e. .so files will be created in libs folder.

I can understand your problem, you can pull the libraries from /system/lib of device or emulator. But you need a system permission. But you can do it by installing application.
Otherwise build your source code on linux platfor. Building process is very easy, just using 2 or 3 command. First time it is needed long time to build. After that you need very short time to build, it will build only according to the timestamp of modified code.
Please have a look here