Update to latest remill

[mrexodia]

Recently I spent quite a lot of time updating remill to be compatible with LLVM 15-21 and to drastically improve the build process of the semantics: lifting-bits/remill#736

Just wanted to let you know in case you would like to update remill to the latest version with these changes!

[yomaytk]

Thanks for the suggestion!
Remill’s build environment has been maintained mainly on a few OSes like Ubuntu, so updating the build setup would be really helpful!
Build environment issues were also mentioned in this issue recently, and we’re planning to bring it into elfconv soon.

[Fancy2209]

I can help!
Though last time I tested, you can't really just add_subdirectory on upstream remill? I remember not beeing able to set CMAKE_PREFIX_PATH from the CMakeLists, guess I'll try to get it working with the user manually passing that

[mrexodia]

You should be able to (although I wouldn’t recommend it). A superbuild pattern is the easiest and most idiomatic cmake.

A full example is here: https://github.com/LLVMParty/remill-template

[Fancy2209]

so rely on the user to build remill and then just do find_package(remill REQUIRED)?

[mrexodia]

It doesn't have to be the user, it's just a separate CMake project called dependencies which does ExternalProject_Add + magic to build everything in dependencies/install.

The core idea is that the dependencies project contains all of the links+configuration for the dependencies and builds 'the universe'. Remill used to be particularly painful, because it depended on gcc-multilib but that requirement has since been removed so now it's just LLVM+glog+gtest+XED (all of which are in the example project)

[yomaytk]

As mentioned briefly above, the main issues with the current build system is that it depends on cxx-common(actual dependency code). This repository is no longer maintained, and due to this dependency, the build environment is limited to Ubuntu 22.04 with LLVM 16.

@mrexodia
Thank you for suggesting remill-template and for your work on it! Since elfconv includes many custom modifications to remill, I believe it is more practical to use a build system that is decoupled from the upstream remill project. This repository appears to be potentially useful for elfconv as well, although I have not yet had tried it.

@Fancy2209
If you are interested in working on this, contributions such as pull requests or related issues would be very welcome!🚀

[mrexodia]

The cxx-common repository is completely removed from Remill now so you shouldn't have any issues. My dependencies folder is something you can copy into your project, it is not connected to Remill. For example Remill itself uses a copy to get its own dependencies for CI: https://github.com/lifting-bits/remill/tree/master/dependencies

Since elfconv includes many custom modifications to remill

Any reason to not upstream the changes? Remill is currently actively maintained and I'm sure they would be happy to take your improvements! CC @kyle-elliott-tob

[kyle-elliott-tob]

Actively maintained indeed, always happy to take patches or just discuss pain points and solutions 😄

[yomaytk]

Recently, I was able to remove the dependency on cxx-common by improving the dependency setup, and it is now working correctly (#210). Thank you for the great work!

Any reason to not upstream the changes? Remill is currently actively maintained and I'm sure they would be happy to take your improvements!

When I first started working on elfconv, remill did not seem very active, so I did not pay much attention to following upstream.

Since then, I have added several custom changes. In particular, I implemented optimization passes to speed up the LLVM IR generated by remill (ref. backend/remill/lib/BC/VroTraceLifter.cpp). Because of this, I made some relatively large changes, such as modifying parts of the AArch64 semantics interface. So catching up with the upstream remill may take some time.

However, it looks like remill has recently added more x86 instructions. Since I would like to support x86 in the future, I will consider following upstream more closely.

I also think there may be areas where I can contribute back, for example by adding additional AArch64 instruction support. I’m not sure how much time I can dedicate yet, but I would be happy to contribute or join discussions as much as I can!