However, that does not mean the field is empty. This article will explore what actually exists, the tools you can use, the difference between disassemblers and decompilers, and the practical workflow for reverse engineering an NDS game. Before downloading any tools, you must understand the two layers of software translation. The Disassembler A disassembler reads machine code (the binary 1s and 0s the ARM CPU executes) and translates it into assembly language (e.g., LDR r0, [r1, #4] ). This is a 1:1 mapping. Every NDS ROM contains ARM9 and ARM7 binaries. A disassembler shows you exactly what the CPU does, step by step. The Decompiler A decompiler attempts to go further: from assembly back to a high-level language like C. This is an inverse problem —information about variable names, original loop structures, and comments is irretrievably lost during compilation. Modern decompilers use heuristics, pattern matching, and data-flow analysis to produce approximate C code.
The header at offset 0x20 says the ARM9 entry point. Usually 0x02000000 or 0x03700000 (for DLDI homebrew). nds decompiler
– For a simple function that sets the display mode, Ghidra might give: However, that does not mean the field is empty
– Ghidra will find code entry points. Use the Decompiler window. The Disassembler A disassembler reads machine code (the
Ghidra requires you to create a custom memory map for the NDS. Without it, the decompiler will produce nonsense like:
[ ARM9 binary ] – main game logic [ ARM7 binary ] – sound, touch screen, wifi [ Header ] – entry points, RAM addresses [ File system ] – graphics, sounds, scripts [ Overlay tables ] – code that loads dynamically When you run a "decompiler" on the ARM9 binary, you must tell it where code lives. The NDS maps code to specific addresses (e.g., 0x02000000 for main RAM, 0x01FF8000 for DTCM). A good decompiler needs a or memory map definition.
Introduction: The Black Box Under Your Fingertips In 2004, the Nintendo DS (NDS) changed portable gaming. With dual screens, a touch interface, and a clamshell design, it became one of the best-selling handhelds of all time. Under the hood, however, the NDS was a powerful (for its era) dual-processor system: an ARM9 for main game logic and an ARM7 for I/O and sound.