Database Develop

[Q] Can Xposed hook native methods?

Letts assume there is a method
public static native boolean doSomething(params...);
which gets called by regular Java code.
Can Xposed hook it?

EDIT: I'm wrong, see rovo's answer.

Yes, native methods can be hooked. However, in case this is for an app's code, it has to be done after System.loadLibrary(), otherwise the latter overwrites the hook. Ideally, the framework should take care of this itself, but it's not straight-forward and the has been vey little need for this.

rovo89 said:
Yes, native methods can be hooked. However, in case this is for an app's code, it has to be done after System.loadLibrary(), otherwise the latter overwrites the hook. Ideally, the framework should take care of this itself, but it's not straight-forward and the has been vey little need for this.
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I've always assumed this wasn't the case. Just to clarify, Xposed is able to hook native functions, but not (native) C/C++ code/libraries? I've read more than once it can't so I'm a bit confused. Thanks for the correction.

GermainZ said:
Just to clarify, Xposed is able to hook native functions, but not (native) C/C++ code/libraries?
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Correct. Only JNI functions can be hooked, i.e. those which are declared in and called by Java code.

How to do it "after System.loadLibrary()"?

How you go about hooking such methods? I am trying to hook some API methods, mainly the ones declared in the "Connectivity" class one such example is "isTetheringSupported" however I am struggling to do so as when I hook the method directly, the hook is never executed as I believe it is being called via the java.lang.reflect.Method invoke method, and when I try and hook that method I get the following error "java.lang.NoSuchMethodError: java.lang.reflect.Method#invoke()#exact"

hwhh_1 said:
How you go about hooking such methods? I am trying to hook some API methods, mainly the ones declared in the "Connectivity" class one such example is "isTetheringSupported" however I am struggling to do so as when I hook the method directly, the hook is never executed as I believe it is being called via the java.lang.reflect.Method invoke method, and when I try and hook that method I get the following error "java.lang.NoSuchMethodError: java.lang.reflect.Method#invoke()#exact"
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Are you talking about EdXposed? If so it should be noted that hook not working for a particular method can also be a result of art compiler optimizations. E.g. if the method is simple and not called from many places, compiler will include body of such method directly into methods that call that method. It's called inlining. So while you can see method at source code level, during runtime it's empty and never called as original body became part of another method. To overcome this you have to find a different strategy, e.g. hook such methods that are less likely to become inlined.

C3C076 said:
Are you talking about EdXposed? If so it should be noted that hook not working for a particular method can also be a result of art compiler optimizations. E.g. if the method is simple and not called from many places, compiler will include body of such method directly into methods that call that method. It's called inlining. So while you can see method at source code level, during runtime it's empty and never called as original body became part of another method. To overcome this you have to find a different strategy, e.g. hook such methods that are less likely to become inlined.
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In order to see if it inlined, there is a setting in EDXPOSED to deoptimize boot image.

Global Static Object Possible?

Currently I'm reading off a SQLITE database and storing the results in memory for further processing, lets call this Object X.
I put Object X is lets say in Class A, so I basically have a static reference to it.
Is it possible in any way to maintain the same copy of Object X in all of the process that I hook to?
Currently, Object X will become null as a package loads via my class that implements IXposedHookLoadPackage (it appears that it has its own version of Object X for every package loaded).

jasonpohzh said:
Is it possible in any way to maintain the same copy of Object X in all of the process that I hook to?
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In short: No. Every process has its own memory. Whatever you set up in initZygote() will be cloned for the application processes, but any changes you do in one process won't be reflected in the other processes (including the main/Zygote process). You have to use some kind of IPC (inter-process communication) for that, like broadcasts or simply a file.

[Q] Sharing data between Xposed module and activity

Hi,
I have an Xposed module that listens for certain events and then notify the main application/Activity that contains this module about the events. I tried to put the events into a static buffer class that's accessible from both the module and Activity. But the buffer is always empty. Right now, I have to use Broadcast to achieve the notification. Is it impossible to share data between the module and Activity via static in-memory objects? Thank you!

AFAIK, you can't do it like that when xposed module runs in a different process than your app.
Xposed module hooking on one package and your app package are isolated processes that cannot share memory.
One way is to use broadcast, as you mentioned.
Another way is to create a service within your app and use ServiceConnection to bind to it and execute actions on it
Example of such service: https://github.com/GravityBox/Gravi...o/kitkat/gravitybox/KeyguardImageService.java
Example how that service is called from system context (different process): https://github.com/GravityBox/Gravi...m/ceco/kitkat/gravitybox/ModDisplay.java#L521

[Q] Hook and run outside

Hello,
Im looking to hook a method(gaining some info) and then execute command externally from the hook. Is there a way to run code from the xposed module app after the hook is applied?

Yes,
If method from class then XposedHelpers.callMethod(params);
If from helper (nothing with UI, activity, etc) then simply Helper.doSomething()
If something other, try to use intents (broadcast intent after executing method, receive it via receiver and perform your code.

[Q] Is static members shared between processes in XPosed hook class?

Here's what I think XPosed does:
1. Before zygote_init, hook all apis and insert xposed_before_xxx and xposed_after_xxx method (where xxx is the name of the api).
2. Load modules. Load hook class, realize it and keep it in memory of zygote. For each injecting method, add it to the private list of xposed_before/after_xxx.
3. When an new app loads (forks from zygote), it also forked the hook class and the hooked method.
4. When an app calls xxx, it actually runs xposed_before_xxx first, and the latter calls every inject method in its private list. Then the original api is called. Then xposed_after_xxx is called, and deals with itself's list.
So for each app, hook class is individual after forking from zygote. So, static members are not shared. Cause each hook class has only one instance in an app, static members act the same as non-static members. Am I right?
And by the way, how does a xposed module to communicate between processes? I've seen a post realizing its own rpc by getting context and creating a service. Any simpler ways for just single direction transferring? Currently I'm using XSharedPreference and SharedPreference, but then then the hook method can't write back anything (such as logging). Any ideas to solve this?
Thanks for reading my long & poor English...