data/ (The file system containing textures, models, and audio) Step 2: Setting Up the Workspace
: Tools like DSLazy or ndstool are used first to unpack the .nds file into its core components: the ARM9 and ARM7 binaries, overlays, and the file system.
: Includes tools for extracting ROMs into separate code and asset files and supports integration with objdiff to track progress toward a matching build. 3. NDS-Decompilation-Project-Maker
A decompiler must not only translate instructions but also parse this structure, separate the two CPU binaries, and map memory addresses back to logical segments.
The ROM hacking community has developed specialized loaders (such as the ghidra-nds-loader ) that automatically recognize .nds files, map the correct memory regions for the ARM9 and ARM7 processors, and label known hardware registers. 2. IDA Pro (Commercial / IDA Free) nds decompiler
Decompilation exists in a complex legal space. Game code is copyrighted intellectual property, and the process of reverse engineering can potentially infringe on those rights. However, several factors may provide legal cover for responsible decompilation efforts.
Begin with a specific, narrow goal: locate a piece of text, understand a game mechanic, or find where a particular variable is stored. Use No$GBA breakpoints to halt execution when a value changes, then trace back to the code responsible. Follow tutorials like "Reverse Engineering a DS Game" from StarCube Labs, which provides a primer on loading DS ROMs into Ghidra and setting breakpoints.
Decompilation is rarely a "one-click" solution. Compilers discard massive amounts of context when turning source code into binary.
If you are just getting started, I can help you or GitHub project for a game you are interested in. Which game do you want to begin your decompiler project with? AetiasHax/ds-decomp: Toolkit for decompiling DS games data/ (The file system containing textures, models, and
In ARM binaries, data (like image pointers) is often mixed with code. If a decompiler tries to read an image as code, it produces "garbage" output. Legal Sensitivity:
Instead of just one tool, the community often forms projects around specific games. The most famous are the Pokémon Diamond/Pearl Pokémon HeartGold/SoulSilver
Retail NDS games do not include function names or variable titles. You will see names like FUN_020004a2 instead of Player_CalculateDamage . You must manually deduce what functions do based on their behavior and rename them.
Whether you are looking to fix bugs in a classic game, translate a Japan-exclusive title, or understand how early 2000s developers optimized code for restricted hardware, decompilation is your gateway. This comprehensive guide explores how NDS decompilers work, the primary tools available, the architecture of the Nintendo DS, and a step-by-step overview of the decompilation workflow. Understanding the Challenge: The NDS Architecture IDA Pro (Commercial / IDA Free) Decompilation exists
offers a user-friendly graphical interface that unpacks every section of an NDS ROM and allows you to repack them after modification. A typical NDS ROM consists of a header, ARM9 binary (the primary game logic), ARM7 binary (system and audio handling), optional overlays, filename tables (FNT), file allocation tables (FAT), icon/title logos, and the FAT files—the actual graphics, music, and data resources. Be aware that ROMs with overlays present additional complexity and are not fully supported by some unpacking tools.
By decompiling the code, developers can rewrite the graphics layer for OpenGL or DirectX, allowing NDS games to run natively on PCs with 4K resolution and widescreen support. Advanced Modding:
offers a more accessible emulator with debugging features, though its capabilities are often described as "weak-sauce" compared to No$GBA. It does support GDB debugging, allowing you to attach external debuggers.
for free NDS reverse engineering. Use IDA Pro + Hex-Rays only if you do NDS RE professionally.
By automating the transition from binary to source, an NDS decompiler serves as an essential tool for digital archeology. Future work involves integrating machine learning to improve variable naming and "symbolication" based on known open-source SDKs.