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Binary Disassembly

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Allison Mackenzie edited this page Oct 9, 2023 · 32 revisions

This page is a stub. WIP.

Although it is the goal of the administrators to disassemble all of the game's binaries long before having everyone rush to match functions, perhaps the information contained here is useful to those of you who are curious how we went about this process. This information can be used for many of your favorite games.

This page is a stub. WIP.

Adding the Binary to the Makefile

The first thing done is adding the binary to the Makefile. Let's take the overlay Pumpkin Gorge as an example. Pumpkin Gorge is obviously shortened to PG/pg.

Note: For this section, you'll want to ignore the *'s in the actual Makefile as this is added here only in the wiki for emphasis!

The following can be added at the top in the appropriate place.

OVL_PG			:= pg

In the case of an overlay, you can find the overlays instruction and add it as part of the necessary overlays (this is obviously not necessary in cases of things which are not overlays).

overlays: ac ag cc ch cr credits dc ee eh gg gs gy1 gy2 hh hr ia la landmap pd **pg** ps sf sv td tl zl

A little bit further down in the make file you should add the instruction for that particular overlay.

pg: ovlpg_dirs $(BUILD_DIR)/PG.BIN
$(BUILD_DIR)/PG.BIN: $(BUILD_DIR)/ovlpg.elf
	$(OBJCOPY) -O binary $< $@

Next, you'll add it to the extract instruction.

extract: extract_main extract_game extract_ovlac extract_ovlag extract_ovlcc extract_ovlch extract_ovlcr extract_ovlcredits extract_ovldc extract_ovlee extract_ovleh extract_ovlgy1 extract_ovlgy2 extract_ovlhh extract_ovlhr extract_ovlia extract_ovlla extract_ovllandmap extract_ovlpd **extract_ovlpg** extract_ovlps extract_ovlsf extract_ovlsv extract_ovltd extract_ovltl extract_ovlzl

Finally, you'll want to add it to the phony at the bottom of the make file.

.PHONY: main game ac ag cc ch cr credits dc ee eh gg gs gy1 gy2 hh hr ia la landmap pd **pg** ps sf sv td tl zl

Creating a Splat Config File

Inside your root directory, you'll find a folder/directory called config which contains a few files that start with the word splat. There's 2 ways to make the appropriate file.

Copy and Pasting

If you're working with a project which already contains a splat yaml files, then copy/pasting a new one, then renaming it appropriately, and editing the contents to fit your needs is 100% a valid option. It's what we did for most of the overlays in MediEvil Decomp!

Using Splat To Generate One For You

You can also using Splat directly to do that. Instructions on how to do that will be added here soon!

Creating a Symbols File

Also inside your config folder/directory, you'll find some txt files which start with the word symbols. STUB WIP.

Modifying the Splat Config File

The Splat Config file is the gateway of the extraction process from the binary to MIPS assembly and C code (as well as rodata and data). Let's take a look at Sleeping Village (SV/sv).

name: SV.BIN
sha1: 7a5b3a3f15a61ebb69e1fe98893a7fa9e3289407
options:
  platform: psx
  basename: ovlsv
  base_path: ..
  build_path: build/
  target_path: disk/OVERLAYS/SV.BIN
  asm_path: asm/ovl/sv
  asset_path: assets/ovl/sv
  src_path: src/ovl/sv
  compiler: GCC
  symbol_addrs_path: config/symbols.ovlsv.txt
  undefined_funcs_auto_path: config/undefined_funcs_auto.ovlsv.txt
  undefined_syms_auto_path: config/undefined_syms_auto.ovlsv.txt
  ld_script_path: config/ld/ovlsv.ld
  find_file_boundaries: yes
  use_legacy_include_asm: no
  migrate_rodata_to_functions: yes
  asm_jtbl_label_macro: jlabel
  section_order:
    - ".rodata"
    - ".text"
    - ".data"

  subalign: 2

  rodata_string_guesser_level: 2
  data_string_guesser_level: 2

segments:
  - name: ovlsv
    type: code
    start: 0x00000000
    vram: 0x80010000
    subsegments:
      - [0x0, rodata]
      - [0xD8, c]
      - [0x72D0, data]
  - [0xD214]

The Different Properties

  • name: The binary (SV.BIN).
  • sha1: The sha1sum, to find this type sva1sum ./disk/OVERLAYS/SV.BIN in the root directory in a terminal.
  • options: Added options for Splat.
  • platform: The console/platform the game is based on, in MediEvil's case it is on the PlayStation 1, so psx.
  • basename: ovlsv, meaning overlay Sleeping Village.
  • base_path: .. - meaning the root or where to start the traversal for other options.

disasm_unknown: true

You can add disasm_unknown: true as an option to the YAML configuration file to force all data to be extracted as assembly.

Finding The Size Of the Binary

The process of finding the size of the binary is quite simple. You will need to use a hex editor program, such as HxD, to open the binary then scroll all the way to the bottom and find the very last address. Using Pumpkin Gorge again as an example, 0x94DF is the final value, so the size is 0x94E0 because you need to add 1 bit to it. Make sure to read the next section to understand why.

Size Must Be 0 Aligned

Under the segment property, the size of the overlay (which is indicated by the line - [0x0000] must end in a multiple of 4 (0, 4, 8, or C in hexadecimal). , the nearest 0 Aligned value is 0x94E0 which is the correct size.

medievil.check.sha

Inside of the config directory, there is a file called medievil.check.sha which contains the sha1sum value of the different binaries. This is the same value you generated for the splat config sha1 property. To reiterate, to generate a sha1sum you will need to type sva1sum <path to file>, then add it to the file. The MediEvil Decompilation project handles this by order of importance being Main > Game > Overlays, then in alphabetical order, although this isn't necessary.

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