Class: ASMREPL::REPL

Inherits:
Object
  • Object
show all
Includes:
Fiddle
Defined in:
lib/asmrepl/repl.rb

Constant Summary collapse

CFuncs = 
Linux

Instance Method Summary collapse

Constructor Details

#initialize ⇒ REPL

Returns a new instance of REPL.



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# File 'lib/asmrepl/repl.rb', line 21

def initialize
  size = 1024 * 16 # 16k is enough for anyone!
  @buffer = CFuncs.jitbuffer(size)
  CFuncs.memset(@buffer.memory, 0xCC, size)
  @parser    = ASMREPL::Parser.new
  @assembler = ASMREPL::Assembler.new
end

Instance Method Details

#display_state(state) ⇒ Object 



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# File 'lib/asmrepl/repl.rb', line 29

def display_state state
  puts " CPU STATE ".center(48, "=")
  puts state
  puts
  puts "FLAGS: #{state.flags.inspect}"
  puts
end

#start ⇒ Object 



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# File 'lib/asmrepl/repl.rb', line 37

def start
  pid = fork {
    CFuncs.traceme
    @buffer.to_function([], TYPE_INT).call
  }

  tracer = CFuncs::Tracer.new pid
  should_cpu = true
  while tracer.wait
    state = tracer.state

    # Show CPU state once on boot
    if should_cpu
      display_state state
      should_cpu = false
    end

    # Move the JIT buffer to the current instruction pointer
    pos = (state.rip - @buffer.memory.to_i)
    @buffer.seek pos
    use_history = true
    loop do
      cmd = nil
      text = Reline.readmultiline(">> ", use_history) do |multiline_input|
        if multiline_input =~ /\A\s*(\w+)\s*\Z/
          register = $1
          cmd = [:read, register]
        else
          cmd = :run
        end
        true
      end

      case cmd
      in :run
        break if text.chomp.empty?
        binary = @assembler.assemble @parser.parse text.chomp
        binary.bytes.each { |byte| @buffer.putc byte }
        break
      in [:read, "cpu"]
        display_state state
      in [:read, reg]
        val = state[reg]
        if val
          puts sprintf("%#018x", state[reg])
        else
          puts "Unknown command: "
          puts "  " + text
        end
      else
      end
    end
    tracer.continue
  end
end