On which forum to ask questions regarding: Android, JNI, NativeActivity, debugging a JNI lib without sources, reverse engineering them, is almost hacking?

Question

Java

Or maybe even disassembly of ELF ARM/x86 assemblies...

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My problem from the point of view of a reverser, and not a simple developer , is relatively noobish and uncomplicated. Tea, I'm not breaking into the Pentagon.

There is an android app.
It has a JNI library like lib.so. NativeActivity.
The main functionality is in it, but Behavior (a dozen classes with fifty methods in each) is written in Java.
There is no obfuscation.

And here is my task - to create for this library my application of the Launcher type, adding additional. functional.
Decompiling the whole thing is hard and long, de-smali-tion even more so.
Therefore, I just take the library and start recreating Behaviour, by typing to determine the really necessary methods, closing them with stubs (stub), etc. etc.

At first everything went well. LogCat has a detailed StackTrace of each exception. Decompiled, took the desired method, copy-pasted - and moved on.
But then I got to those places in the library where the Behavior methods are called somehow differently!
I don't know what's the matter, I don't know how to disassemble such libraries.
But only "blablabla Exception NoSuchMethodError" appeared in LogCat, without Stacktrace.
... Not even a week has passed since I solved the problem, just by guessing to press Debug in Eclipse, at a time when I used to press Run all my life.
I corrected these exceptions.

But now another problem:
in LogCat, the error "JNI ERROR" pops up, there is
no StackTrace anywhere,
which is interesting, in the debugger there is again a mention of "exception NoSuchMethodError", but no stack traces, nothing. I searched everything - well, no, that's all. Everywhere it is written: they say the code is native, so it is impossible to debug it...

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...And unfortunately, neither here, on the Toaster, nor on StackOverflow (including English), I did not find help, no matter how I searched, how many questions I didn't set how many tags I tried.
On StackOverflow, even on the first problem, they said that it was impossible to solve it. But a solution has been found.
I think everything is simple with the second one too - but you need to have special magic.

So, where can I find such magicians?
Maybe in Google Groups? After all, the official Android forum...
Or on XDA (a forum with the word "Hacking" in its name)?
Or is it generally worth focusing not on the "android" of the forum, but on something else?

Answer 1

there is a JNI library like lib.so. NativeActivity.
...
I don't know how to disassemble such libraries.

You take objdump from the toolchain with which the lib is built and execute objdump -xd lib.so.NativeActivity.
Ask clarifying questions: it is not clear what exactly you are having difficulty with.