offset_calc

#!/usr/bin/env ruby
#
# == Synopsis
#
# ocalc: computes file offset for a given vma address
#
# == Usage
#
# ocalc [OPTION] FILENAME ADDRESS
#
# -h, --help:
#   show help
#
# -a [arch], --arch [arch]
#    calculate for the specified architecture instead of the current (e.g., i386, x86_64, ppc7400)
#
# FILENAME: the mach-o binary executable to perform calcuations on
# ADDRESS: the address to convert to an offset
#
# == Example
#
# ocalc --arch i386 /bin/ls 0x33fb
 
require 'getoptlong'
require 'pp'
require 'rdoc/usage'
 
FatInfo = Struct.new(:offset, :size)
def fat_info(target_file)
  text = `lipo -detailed_info #{target_file}`
  Hash[*text.scan(/
    architecture\s(\w+)
    .*?
    offset\s(\d+)
    .*?
    size\s(\d+)
    /mx).collect { |a| [a[0], FatInfo.new(Integer(a[1]), Integer(a[2]))] }.flatten]
end
 
SegmentInfo = Struct.new(:sectname, :segname, :addr, :size, :offset)
def segment_info(target_file, arch=nil)
  arch_info = `otool #{arch ? "-arch #{arch} " : ""}-l #{target_file}`
  arch_info.scan(/
    Section
    .*?
    sectname\s(\w+)
    .*?
    segname\s(\w+)
    .*?
    addr\s(0x[0-9a-f]+)
    .*?
    size\s(0x[0-9a-f]+)
    .*?
    offset\s(\d+)
    /mx).collect { |a| SegmentInfo.new(a[0], a[1], Integer(a[2]), Integer(a[3]), Integer(a[4])) }.sort { |a, b| a.addr <=> b.addr }
end
 
if __FILE__ == $0
  opts = GetoptLong.new(
    [ '--help', '-h', GetoptLong::NO_ARGUMENT ],
    [ '--verbose', '-v', GetoptLong::NO_ARGUMENT ],
    [ '--arch', '-a', GetoptLong::OPTIONAL_ARGUMENT ]
  )
  opts.each do |opt, arg|
    case opt
    when '--help'
      RDoc::usage
    when '--verbose'
      @verbose = true
    when '--arch'
      @arch = arg
    end
  end
 
  if ARGV.length != 2
    puts "missing filename and/or offset argument (try --help)"
    exit 1
  end
 
  @filename = ARGV.shift
  @address = Integer(ARGV.shift)
 
  fi = fat_info(@filename)
  pp fi if @verbose
  fat_offset = if fi.empty?
    0
  else
    @arch ||= `arch`.chomp
    raise "unknown architecture: #{@arch}" unless fi.key?(@arch)
    fi[@arch].offset
  end
  si = segment_info(@filename, @arch)
  pp si if @verbose
 
  segment = si.detect { |s| s.addr <= @address && @address < s.addr + s.size }
  pp segment if @verbose
  if segment
    offset = @address - segment.addr + segment.offset + fat_offset
    puts "0x%x" % [offset]
  else
    raise "could not find matching segment for 0x%x" % [@address]
  end
end