I'm trying to push executable file to the phone, file was compiled by NDK.
But after copying files to the device they lost their permission (became no excecutable).
Is there any solution to fix kernel sources, or other sources in Android to fix this problem (lost permissions)? I'm pretty sure that it can be ext4 problem...
Note:
I don't want use chmod each time.
If you can wrap your executable in an installable APK, here is the simple trick: https://stackoverflow.com/a/17384650/192373. It has been tested to work up to JellyBean 4.3, but please be aware that it relies on some undocumented behaviours of the PackageManager.
Related
Environment
Windows (x64) Host
Android 5.0 USB connected to the Windows machine
Un-rooted Samsung Galaxy 5
Use-case
Java APK Application
Native C++ executable packed as a raw resource part of the APK
Upon startup executable is to be ~extracted~ to a temp folder where it would execute
Questions/Discussion
Is the above use-case supported by the Android OS?
To the best of my knowledge, '/data/local/tmp' is not accessible to a running app ( but to shell & root ), Is there a directory where the file can be extracted too and executed? ( dir must have execution rights )
What would be the best approach to achieve the above mentioned?
Yes, you can do this. You will need to make sure that the native executable is for the appropriate target architecture (some type of ARM processor, usually).
But you shouldn't extract it to /data/local/tmp. You will need to extract it to /data/data/application.package.name/lib, which is a directory to which your app has read/write permissions.
There are more details in this question and its accepted answer. It looks as though you can have the executable extracted automatically for you if you name it as if it were a library file rather than a standalone executable.
Final purpose of this feat: Use android device for development by fast compiling without needing to use proguard each single time (which causes huge delays)
First try is on Sony Ericsson Xperia Mini Pro
I have installed in it Cyanogenmod which is already rooted and the root checker app has verified it.
This is the app I used to embed Scala library 2.9.1 inside android device:
https://github.com/jbrechtel/Android-Scala-Installer
The lines uses-library android:name="scala_... are now included inside the AndroidManifest
After the above actions I did some minor changes inside "project/Build.scala" like this line: useProguard in Android := false,
I am probably missing something because after recompiling and executing android:start-device I got java.lang.ClassNotFoundException
which is the error you are expecting to get when you have not done the previous steps (rooting device and installing scala libraries inside device)
Any ideas are welcome! Thank you
PS: Intellij is the chosen IDE for the current project so eclipse and the relative plugins is not an option
There is nothing wrong with what I have mentioned above!
BUT there is a command inside Android Scala Installer which requests the "/system" folder to be mounted as writable. Unfortunately this does not work on my gingerbread android phone and this might be the general case.
I simply commented out the operation of the mount /system as writable (and also the command mount /system as read only) and the libraries installed successfully!
Note that I set manually the permissions of /system as writable before installing libraries
In fact I forked the github repository and therefore you can find me implementation over here:
https://github.com/pligor/scala-android-libs
To summarize. Yes the only alterations needed in your scala android source code is to set the settings in Build.scala file for proguard to be false and you include the uses <uses-library android:name="scala_... inside Android Manifest.
I have two executables, both cross compiled to run in Android. I have put both on the device in the same directory. I have put all the shared libraries that they are dependent on in the same directory, including ld-linux.so.3. I run the executables by using:
ld-linux.so.3 --library-path /path/to/libraries executable_name
both work on older versions of Android when running as any user. The both work on the latest version of Android if running as root. Only one works on the latest version of android when running as any user. Instead it gives:
failed to map segment from shared object: executable_name operation not permitted
How can I find out what is different with the executable that won't run?
I read a lot online and most people that get this error, either:
A) don't have execute permissions for one of the libraries they are dependent on or the executable itself.
or
B) are trying to run from a directory that is mounted as NOEXEC.
both of these don't appear to be the case. It can find all libraries and I can load any library by itself and see what other things it is dependent on being resolved. Also, I can run basic scripts from the directories of interest.
The newer version of Android, Jelly Bean, is a different linux kernel version and I wonder if that is related.
What give? How do I debug?
Permission issue. Need to remount /tmp. The following command works for me (Centos 7):
sudo mount /tmp -o remount,exec
I had this error in a different context. For some reason it causes an error when trying to use the /tmp folder.
To solve this I simply:
mkdir tmp
export TMPDIR=`pwd`/tmp
The TMPDIR is a constant that tells where the temporary folder of the system is.
This solutions resolves by creating a directory where we are allowed to and settings this directory into the system. Therefore we can now write to the new system default temporary folder.
The issue was with how the executables were compiled. They needed to be compiled with a cross compiler that properly supported newer arm devices. The compiler I used generated executables that would only work on a subset of arm devices. The issue was not with the different versions of android.
SELinux is enabled by default on Android 4.3, however it is supposed to be "permissive" [0]. Maybe your phone vendor added more restrictive rules.
[0] https://source.android.com/devices/tech/security/se-linux.html
As a follow up to an earlier question (Android ioctl - root permissions and usage), is it possible to create a separate native executable and package it in an APK?
The app needs root access and isn't going into the Android marketplace, but I'd like to be able to install it without using a script that pushes an extra executable onto the device.
There is an easy way to package an executable into an APK, and let the system installer take care of unpacking this executable, see How to package native commandline application in apk?.
The trick (tested up to Jelly Bean 4.3) is to name the file "libmyexecutable.so" and put it into libs/armeabi of your Android project (I assume an ADT or ant build). The Package Manager will unpack the file to /data/data/your.package.full.name/lib (it's a symbolic link, for backwards compatibility reasons, so maybe in some future version of Android this will not work anymore) on the device, with executable permissions.
Note that the file has all read-and-execute permissions, so you can use Runtime.getRuntime().exec() or system() from other apps, too.
Update:
These days, you should use libs/armeabi-v7a for 32 -bit ARM executables, and you probably need to prepare 64-bit ARM version of the same executables, too.
You can put it into assets and copy it to the app's private directory on first run. After you set the executable bit, you should be able to run it.
I'm developping a android's aplication using some shared
libraries written by me and compiled with ndk-r5b. The application works,
y and the calls to the libraries works too, but I detected some errors,
segmentations faults, and I need to debug it, but, I don't know how debug
native code from android and I don't know if I can generate core dumps,
as in linux, for debug my libraries.
Any idea?
The ndk comes with ndk-gdb, which supposedly allows you to debug native applications. Also, if you download the whole andriod open source project, they also have some version of gdb used for debugging. Look in the docs/ folder of the ndk to learn about using it. This tutorial might also prove helpful: http://vilimpoc.org/blog/2010/09/23/hello-gdbserver-a-debuggable-jni-example-for-android/
However, as shown in a recent question I asked: Running ndk-gdb with package not found error on motorola phone I still can't get it to work.
Edit: You said in the comments you were using a Samsung Device: Samsung decide to wreck havoc on some of the crucial internals required for native debugging, but it's easily fixable if you have root access to the device. If you use the --verbose flag, you'll probably find that the error is different than that, a package unknown error. That's because it's looking in /data/system/packages.list, but samsung renamed that file to /dbdata/system/packages.list. So if you make a symlink to that file in /data/system/packages.list, (requires root access) it should work. Or at least so claims the ndk mailing list: http://osdir.com/ml/android-ndk/2011-03/msg00036.html