alt Hacker NewsShow HN: Decomp Academy – Learn to decompile GameCube games into matching C
Over the past few months I've been heavily involved in the decompilation community. I've been hands-on decompiling a beloved game from my childhood (Star Fox Adventures). I started this journey with zero prior decomp experience—and to make things worse I had never really touched C nor assembly either.
Learning how to decompile was challenging. It's difficult to find any good learning resources for it and any open-source projects for this are inactive and/or contain little actual learning material.
So I put together Decomp Academy! Decomp Academy is an interactive way to learn how to decompile PowerPC assembly back into C. The site runs a live Metrowerks CodeWarrior GC/2.0 compiler, converts your C into assembly, and then checks how close your assembly matches the target. If even 1 instruction or bit is off, that's a fail. This is the gold standard for video game decompilation and this is much stricter than a normal decompile.
As of writing there are 250+ lessons on the site and the lessons start at the very basics so anyone with a little programming experience should be able to jump straight in, even if you're not a C expert. Some lessons also have real functions taken from live open source decomp projects (Star Fox Adventures, Mario Party 4, Pikmin, Metroid Prime). The idea being you learn everything you need to know to be able to jump in and contribute to a real decompilation project when done.
The site is completely free, open source and you have access to all lessons without having to sign up. All lessons are stored in markdown in the repo (src/curriculum), it's trivial to add or modify lessons. The site is very new and the lessons are rapidly changing every day with a whole C++ section on the way. The site has already been well received by the decomp community and I'm happy to share it with HN. I'm very keen on others to contribute to this project and I hope this becomes the best resource on the internet for learning the art of decompilation. Please let me know what you think!
Comments
I'd love it if there was some way to contribute to ongoing game decompilation projects, with a similarly streamlined web interface - it's something I'd be willing to dedicate some brain time to every so often, but setting up the toolchain etc. feels too much like work.
By the way, I was able to "cheat" on the second lesson with
void identity(void) { return; }
Dumb question — can LLM be used to reverse-engineer firmware blobs or binary only drivers for Linux, to create open-source drivers, for example, for unsupported smartphones?
I recently heard that Super Mario 64 (N64) modding community reverse engineered the game enough to recreate more-or-less accurate C code that can be compiled in binaries to execute on many popular target architectures. Have you managed to get beloved games into modifiable C code? Or is it more common to invest a lot of work to document assembly language functions? I know some old assembly but no idea what is involved at a high level. Maybe you explain in your lessons?
Also, how to folks obtain binaries? Presumably unless there is a source code breach or vulnerability, source never gets exposed, is thst correct?
Damn this is next level. Congratulations on your achievements!
When Fable was around I thought i'd test it by taking an old piece of Windows software from the late 90s/2000s(ModPlug Player) and seeing how well it could convert it to being a native Mac application.
I was blown away at how it got 85% of the way there in one prompt. Things such as writing a PE extractor, recovering the complete skin, menu tree, full accelerator table, all dialogs, and then it delved into the registry value names as well. Some more prompts got it to 99%(I was happy with that and stopped)
I then took an old 1999 DOS demoscene and yet again it did wonderful magic and got me a native mac build.
I dropped everything I was doing and just started going through all these old apps that I couldn't easily enjoy since im on a Mac. It got to the point where I was losing sleep over it(was just so excited).
The fun ended when I was stopped mid-project with the Fable ban. Opus just does not compare and essentially killed all the enthusiasm after the nth failure of it to complete the task.
It made me realize that among the efforts of the RE community, and the emerging capabilities of these frontier models, in the future we could have the possibility living in a renaissance of open computing if we want any software we see on the market to be forever remixed and tailored to our uses and completely open.
I don't know how the business and legal side will deal with this. There needs to be new frameworks and ways of thinking about this stuff.
I'm just happy that hopefully no code will ever be lost to the sands of time ever again.
The backend is closed source, but it runs all on AWS Lambda/DynamoDB/APIGateway and is written in Rust. Getting the compiler running in a Lambda was an adventure of it's own
Seems like a cool idea, but I can't even complete the first task. The compiler service seems to be broken, since in both lessons and the playground I just get "Could not write source: No space left on device (os error 28)".
This is cool as hell.
On the first lesson, it tells me there's a target on "the right". There isn't anything to the right, I've in clue where to look.
I like decomp, but it makes me nervous. Like how safe is it to decompile a game and publish it to like github with all the symbols, addresses, etc..
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Dumb question about reverse engineering binaries: is there a way to only do it piecemeal? I'm eventually waiting for LLMs and harnesses to get good enough to reverse engineer BFME (old Lord of the Rings game that still has an active modding community), but it's a multi GB sized game that would have to be done in bite-sized pieces.
Basically; can you reverse engineer in bite sized pieces, and recompile/customize their behavior, without needing to do it all at once?