Ask HN: How are you using LLMs for traversing decompiler output?

Echoing IDA but its pricing is a huge PITA if you’re using it in a hobbyist capacity i.e. you don’t have an employer willing to pay for it. Could opt for the home version but that’s a yearly cost and you have to use their cloud decompiler. Ghidra’s your best bet if you want something FOSS and community-driven although not as great at decompilation.

Most decompilers do not strive for recompilability. [1] I believe there are (or were) some academic projects that aimed for recompilation as a core feature, but it is a hard problem.

On the commercial side, IDA / HexRays [2] is very strong for C-like decompilation. If you're looking at Go, Rust, or even C++ it is going to be a little bit more messy. As other commenters have said, you'll work function-by-function and it is expensive, though the free version does have decompilation (F5) for x86 and x64 (IIRC).

Binary Ninja [3] (no affiliation) is the coolest IMO, they have multiple intermediate representations they lift the assembly through. So you get like assembly -> low level IL -> medium level IL -> high level IL. There are also SSA forms (static single assignment) that can aid in programmatic analyses. The high level IL is very readable but makes no effort to be compilable as a programming language. That being said, Binary Ninja has implemented different "views" on the HLIL so you can show it as pseudo-C, Rust, etc. There is a free online version and the commercial version is cheaper than IDA but still expensive. Good Python API, good UI.

Ghidra [4] is the RE framework released by NSA. It is free and open source. It supports a ton of niche architectures. This is what most people use. I think the UI is awful, personally. It has a decompiler, the results are OK. They have an intermediate representation (P-Code) and plugins are in Java (since it is written in Java). I haven't worked much with it.

Most online decompilations you see for old games are likely using Ghidra, some might be using IDA. This is largely a manual process of doing a function at a time and building up the mental map of the program and how things interact.

Also worth mentioning are lifters. There were a few projects that aimed to lift assembly to LLVM IR (compiler framework's intermediate representation), with the idea being that then all your analyses could be written over LLVM IR as a lingua franca. Since it is in LLVM IR, it would be also recompilable and retargetable. [5][6]

1. https://reverseengineering.stackexchange.com/questions/2603/...

2. https://hex-rays.com/ida-free

3. https://binary.ninja/free/

4. https://ghidra-sre.org/

5. https://github.com/avast/retdec

6. https://github.com/lifting-bits/mcsema

Looking at an individual function, IDA hex-rays output is often recompilable as-is (or with minor modifications), but it won't necessarily be idiomatic, especially if you don't have symbol information.

I was about to comment that the domain was quite clever...

i don't think so (that it is a terrible name); it's a pretty common term https://www.urbandictionary.com/define.php?term=reveng

The allowed types are a bit misleading. Any binary is accepted, any architecture. You can upload shared objects, ELF executables, PE binaries, etc.

I like to give it bomb executables (reverse engineering challenges) to test it.

Program database file - only relevant if the binary is Windows. But that makes decomp an order of magnitude easier. I’d be surprised if OP had one though.