自作エミュレータで学ぶx86アーキテクチャ emu2.3のruby版

emu23.rb

#!/usr/bin/env ruby

require 'pp'

class Emulator

    @@EAX = 0
    @@ECX = 1
    @@EDX = 2
    @@EBX = 3
    @@ESP = 4
    @@EBP = 5
    @@ESI = 6
    @@EDI = 7
    @@REGISTER_COUNT = 8


    def initialize(size: 10240, eip: 0, esp: 0x7c00)
        @registers = Array.new(@@REGISTER_COUNT, 0)
        @eflags = 0

        @memory = Array.new(size, 0)
        @eip = eip
        @registers[@@ESP] = esp

        init_instructions

        @register_names = [
            "eax",
            "ecx",
            "edx",
            "ebx",
            "esp",
            "ebp",
            "esi",
            "edi",
        ]
    end

    def read_binary_data_to_memory(data, size: 0x200)
        @memory = data[0..size]
    end

    def run
        while @eip < @memory.length
            code = get_code8(0)

            if @instructions[code].nil?
                puts("[*]Instruction #{code} is not implemtend")
                return
            end

            printf("EIP = 0x%08x, Code = 0x%02x\n", @eip, code)

            self.send(@instructions[code])

            if @eip == 0x00
                puts("[+]End of program")
                return
            end
        end
    end

    def dump_registers
        @@REGISTER_COUNT.times do |i|
            printf("%s = 0x%08x\n", @register_names[i], @registers[i])
        end
        printf("EIP = 0x%08x\n", @eip)
    end

private
    def mov_r32_imm32
        reg = get_code8(0) - 0xb8
        value = get_code32(1)

        @registers[reg] = value
        @eip += 5
    end

    def short_jump
        diff = get_code8(1)
        @eip += (diff + 2)
    end

    def init_instructions
        @instructions = Array.new(256, nil)

        8.times do |i|
            @instructions[0xb8 + i] = "mov_r32_imm32"
        end
        @instructions[0xeb] = "short_jump"
    end

    def get_code8(index)
        return @memory[@eip + index].unpack("C")[0]
    end

    def get_code32(index)
        ret = 0
        4.times do |i|
            ret |= get_code8(index + i) >> (i * 8)
        end
        return ret
    end
end

class Utility
    def self.read_bin_file(filepath)
        st = File::Stat.new(filepath)

        puts("[+]read #{filepath} size #{st.size}")
        f = File.open(filepath)
        return f.read(st.size)
    end
end

if __FILE__ == $0
    if ARGV.length != 1
      puts("usage: #{$0} file")
      exit(-1)
    end

    test_file = ARGV[0]
    excutable_file_data = Utility::read_bin_file(test_file)

    emurator = Emulator.new
    
    emurator.read_binary_data_to_memory(excutable_file_data)
    emurator.run

    emurator.dump_registers
end