Add decompiling.md

CONTRIBUTING.md

@@ -1,6 +1,6 @@
 # Contribution guide
 - [Project structure](#project-structure)
-- [Decompiling a function](#decompiling-a-function)
+- [Decompiling](#decompiling)
 - [Code style](#code-style)
 - [Creating new `.c`/`.cpp` files](#creating-new-ccpp-files)
 - [Non-matching functions](#non-matching-functions)
@@ -39,8 +39,8 @@
 - `assets.txt`: The order of asset directories to put in the ROM
 - `*.sha1`: SHA-1 digests of different versions of the game
 
-## Decompiling a function
-WIP
+## Decompiling
+See [/docs/decompiling.md](/docs/decompiling.md).
 
 ## Creating new `.c`/`.cpp` files
 New source files must be added to the LCF (Linker Command File). This is done via `lcf.py`, which generates the LCF when

docs/decompiling.md

@@ -0,0 +1,41 @@
+# Decompiling
+This document describes how you can start decompiling code and contribute to the project. Feel free to ask for help if you get
+stuck or need assistance.
+- [Decompiling a function](#decompiling-a-function)
+- [The Ghidra project](#the-ghidra-project)
+
+## Decompiling a function
+Say you've found a function you want to decompile. Here are the steps we recommend for decompiling it:
+1. Visit [decomp.me](https://decomp.me/) and start decomping.
+1. Under the platforms, select "Nintendo DS".
+1. Select compiler version `2.0sp1p5`.
+1. Copy and paste the target assembly for your function, including the `func_start` and `func_end` macros, and the pool constants.
+For example:
+```arm
+	.global func_ov09_0211bf48
+	thumb_func_start func_ov09_0211bf48
+func_ov09_0211bf48: ; 0x0211bf48
+	ldr r0, _0211bf50 ; =data_ov09_0211f59c
+	ldrb r0, [r0]
+	bx lr
+	nop
+	thumb_func_end func_ov09_0211bf48
+_0211bf50: .word data_ov09_0211f59c
+```
+6. Run `m2ctx.py include/MyHeader.hpp -c` to generate a context and put it in your clipboard.
+    - If no suitable header file exists, make a new one and put any structs and types you need in there.
+1. Paste the context into decomp.me, and create the scratch.
+1. Copy the `CC_FLAGS` from `Makefile` into the arguments field in decomp.me.
+    - Replace the `-d $(REGION)` flag with whichever region you intend to decompile for. You can also delete the flag entirely
+    if the function contains no region differences.
+1. Decompile the function and try to get a 100% match.
+    - There's no ARM decompiler in decomp.me yet, but Ghidra does the job quite well. See [the Ghidra section](#the-ghidra-project)
+    for more info.
+    - If you're unable to get a 100% match, share your decomp.me scratch with other contributors and they may assist you.
+    - In the worst case, you can also contribute [non-matching functions](/CONTRIBUTING.md#non-matching-functions) to this
+    project.
+
+## The Ghidra project
+We use a shared Ghidra project to analyze the game and decompile functions. We can't give access to the Ghidra server just yet,
+so come back here later for instructions on how to access it.
+