Debug companion app?

[lars18th]

Hi,

I'm not sure if this question is stupid. However, I prefer to ask... 😉

Currently to execute the Termux environment from the ADB shell we need to use the "run-as" command. However, this implies that the Apk requires to be compiled as Debug. Ok, then the Termux App installed by hand requires to be in Debug. But this implies that the performance is reduced, rigth? So, why not provide a Termux-companion App, that will be compiled in Debug, and then it will work calling to the regular Termux App compiled in Release mode?

Please, if this sounds stupid or crazy, then you only need to explain the reason for it. Sorry for any noise created.
Regards.

[agnostic-apollo]

All termux github builds are debuggable and I have not noticed any performance issues under normal conditions, its still snappy. If I am not mistaken, any serious performance issues are likely gonna happen when app is connected to a debugger, like in android studio, despite any extra debug code added to the app.

If you are still worried about performance issues and want to remotely connect, use ssh, although that will have network issues.

https://github.com/termux/termux-app#github

https://wiki.termux.com/wiki/Remote_Access#SSH

So, why not provide a Termux-companion App, that will be compiled in Debug, and then it will work calling to the regular Termux App compiled in Release mode?

How is the app supposed to "connect" to regular app, over which protocol?

[agnostic-apollo]

How about testing it yourself with github vs f-droid builds if its that much of a concern.

[lars18th]

Hi @agnostic-apollo ,

Perhaps I'm expresed wrong. I'm using Termux with the github version. And this version is debuggable. So I can start it using the run-as command from the ADB shell. So this is not a problem for me now.

So, what I ask if it's possible to provide the same for a Termux without debug enabled. Only that. For example, the Termux-api can call to Termux-App. The question is: if one is debuggable and the other not, but signed with the same certificate... then they can communicate? IF the answer is YES, then perhaps a Termux non debuggable can be started from a debuggable Termux-companion that has started with run-as.

I hope now the question will be more clear. Excuse me for my poor explanation before.
Regards.

[agnostic-apollo]

Define "started from a debuggable Termux-companion". And if there will be constant communication between debuggable Termux-companion and Termux non debuggable, then you would obviously have performance issues you are trying to avoid.

Secondly, run-as doesn't start the app process or goes through it, it just changes current uid/gid/selinux context and capabilities that would normally be assigned to the app and starts a shell process. It won't be running any debuggable code in the app, only debuggable flag is checked by run-as.

https://cs.android.com/android/platform/superproject/+/android-12.0.0_r4:system/core/run-as/run-as.cpp;l=164

https://cs.android.com/android/platform/superproject/+/android-12.0.0_r4:external/minijail/libminijail.c;l=2264

Any performance issues would be when app is run and likely connected to debugger. I have not noticed any slow downs, even on my 6 year old device. And I am pretty sure no termux dev would invest time to implement a companion app for any said minuscule improvements just for a few run-as users, even if it was possible. There are far more important things to do. And any communication protocol between the apps will obv have its own lags, so there is no point anyways.

If you have root, then you can alternatively use non-debuggable termux and start a shell in termux context. Check https://android.stackexchange.com/questions/217016/how-to-run-a-program-in-an-app-context-with-magisk. Termux util-linux provides setpriv and nsenter binaries now added in termux/termux-packages#8198.

[lars18th]

Hi @agnostic-apollo ,

Thank you for the detailed explanation. Now I'm aware of some relevant information that I've missed:

• The "run-as" tool checks if the package has the "debug" flag.
• Setting the "debug" flag in the Termux has a negligible performance penalty.

In this case, I apologize for this request. It doesn't have sense. Even I've learned a lot about the Termux context. 😃
Thank you.

[agnostic-apollo]

negligible performance penalty.

I don't know how negligible though, that would require testing.

Welcome.