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| -rw-r--r-- | docs/decompiling.md | 36 |
1 files changed, 28 insertions, 8 deletions
diff --git a/docs/decompiling.md b/docs/decompiling.md index bedb1cbb..3ff23f2b 100644 --- a/docs/decompiling.md +++ b/docs/decompiling.md @@ -2,6 +2,7 @@ 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. - [Pick a source file](#pick-a-source-file) +- [Decompiling a source file](#decompiling-a-source-file) - [Decompiling a function](#decompiling-a-function) - [Decompiling `.init` functions](#decompiling-init-functions) - [The Ghidra project](#the-ghidra-project) @@ -18,13 +19,24 @@ If you want to unclaim the file, leave another comment so we can be certain that again. Remember to make a pull request of any notable progress you made on the source file, which can include [non-matching functions](/CONTRIBUTING.md#non-matching-functions). +## Decompiling a source file +It can be tricky to fully decompile an assembly file into a C/C++ source file, so here's some advice to make it easier: +- C/C++ code is built before assembly code + - This means you can take one function from the top of your assembly file, decompile it, and append it to the bottom of + your C/C++ file. +- Build the ROM often + - We recommend building every time you decompile a function. + - This is because functions can sometimes match in decomp.me, but not when building. + - If your ROM doesn't match, it's easier to know which function is wrong if it's the only function added since the last + successful build. + ## 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: +1. Select compiler preset "Phantom Hourglass". +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 @@ -36,13 +48,9 @@ func_ov09_0211bf48: ; 0x0211bf48 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. +5. 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. - - Also copy `CXX_FLAGS` if your function comes from a `.cpp` file. Otherwise, copy `C_FLAGS` if it's a `.c` file. - - 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. @@ -70,6 +78,18 @@ is 12 (`0xc`) bytes long and is also implicit, so we don't need to define it our > [!IMPORTANT] > An important thing to keep in mind is that a static initializer can construct multiple global objects. +## Decompiling data +> [!NOTE] +> Under construction! It's not fully clear how data is decompiled, as the compiler is strict on how it orders global variables. +> Feel free to contribute to this section or provide us with more information! + +Other than `.text` and `.init` which contain code, there are the following sections for data: +- `.rodata`: Global or static constants +- `.data`: Global or static variables +- `.bss`/`.sbss`: Global or static uninitialized variables + +You can see examples of these data sections in the [compilation section in `build_system.md`](/docs/build_system.md#compiling-code). + ## The Ghidra project We use a shared Ghidra project to analyze the game and decompile functions. To gain access to the project, install [Ghidra version 10.2.3](https://github.com/NationalSecurityAgency/ghidra/releases/tag/Ghidra_10.2.3_build) and request access |