nitrodis.rb

# NDSファイルの中のoverlayたちを展開して逆アセンブルする

# Usage: ruby nitrodis.rb <filename>.nds


require "fileutils"

OBJDUMP = 'C:/devkitPro/devkitARM/bin/arm-none-eabi-objdump.exe'
SIZEOF_OVR = 32

Fat = Struct.new(:start, :end)
Ovr = Struct.new(:id, :ramaddr, :ramsize, :bsssize, :start, :end, :file_id, :reserved)

def read_u32(f, ofs)
  f.seek ofs
  f.read(4).unpack("V")[0]
end

def read_u32_list(f, ofs, len)
  f.seek ofs
  f.read(4 * len).unpack("V*")
end

def read_cstr(f, ofs, len)
  f.seek ofs
  f.read(len).unpack("Z*")[0]
end

def read(f, ofs, bytes)
  f.seek ofs
  f.read(bytes)
end

def do_file(fname, bin, addr)
  File.binwrite(fname+".orig", bin)
  system "./DSDecmp", "-d", "-f", "lzovl", fname+".orig", fname
  destfname = File.exist?(fname) ? fname : fname + ".orig"
  system OBJDUMP, "-b", "binary", "-m", "arm",
         "-Mforce-thumb", "--adjust-vma=#{addr}",
         "-D", destfname, {1 => destfname + ".dis"}
end

fname = ARGV[0]
open(fname, "rb") do |f|
  romname = read_cstr(f, 0, 12).gsub(" ", "")
  arm9exe_start = read_u32(f, 0x20)
  arm9exe_size = read_u32(f, 0x2c)

  fat_off = read_u32(f, 0x48)
  fat_size = read_u32(f, 0x4c)
  num_files = fat_size / 8
  arm9_overlay_off = read_u32(f, 0x50)
  arm9_overlay_size = read_u32(f, 0x54)
  num_overlay_9 = arm9_overlay_size / SIZEOF_OVR
  fats = []
  ovrs = []
  num_files.times do |i|
    s, e = read_u32_list(f, fat_off + i * 8, 2)
    fats << Fat.new(s, e)
  end
  dirname = "overlay-#{romname}"
  #FileUtils.rm_r dirname
  FileUtils.mkdir_p dirname

  bin = read(f, arm9exe_start, arm9exe_size)
  do_file "#{dirname}/arm9exe", bin, 0x02000000

  num_overlay_9.times do |i|
    ovr = Ovr.new(*read_u32_list(f, arm9_overlay_off + i * SIZEOF_OVR, 8))
    ovrs << ovr
    fat = fats[ovr.file_id]
    #puts "%d %08x %d %d %08x %08x %d %d %08x" % [ovr.file_id, ovr.ramaddr, ovr.ramsize, ovr.bsssize, ovr.start, ovr.end, fat.start, fat.end - fat.start, ovr.reserved]
    #puts "%d %08x %d" % [ovr.file_id, ovr.ramaddr, ovr.ramsize]
    bin = read(f, fat.start, fat.end - fat.start)
    ovrfname = "#{dirname}/#{ovr.file_id}"
    do_file ovrfname, bin, ovr.ramaddr
  end
end