func findEntry(f *macho.File, bits int) (uint64, error) {
	var entry uint64
	for _, l := range f.Loads {
		var cmd macho.LoadCmd
		data := l.Raw()
		binary.Read(bytes.NewReader(data), f.ByteOrder, &cmd)
		if cmd == macho.LoadCmdUnixThread {
			// LC_UNIXTHREAD
			if bits == 64 {
				ip := 144
				entry = f.ByteOrder.Uint64(data[ip : ip+8])
			} else {
				ip := 56
				entry = uint64(f.ByteOrder.Uint32(data[ip : ip+4]))
			}
			return entry, nil
		} else if cmd == machoLoadCmdMain {
			// [8:16] == entry - __TEXT, data[16:24] == stack size
			__TEXT := f.Segment("__TEXT")
			if __TEXT == nil {
				return 0, errors.New("Found LC_MAIN but did not find __TEXT segment.")
			}
			entry = f.ByteOrder.Uint64(data[8:16]) + __TEXT.Addr
			return entry, nil
		}
	}
	return 0, errors.New("Could not find entry point.")
}

func printFileInformation(f *macho.File) {
	log.Printf("ByteOrder: %s", f.ByteOrder)
	printHeader(&f.FileHeader)

	// Also f.FileHeader.Ncmd
	log.Printf("file has %d load commands", len(f.Loads))
	log.Printf("file has %d sections", len(f.Sections))

	printSections(f.Sections)
	printSymtab(f.Symtab)
	printDysymtab(f.Dysymtab)
	printImportedLibraries(f.ImportedLibraries())
}

// Open an input file.
func open(name string) (*file, error) {
	efile, err := Open(name)
	var mfile *macho.File
	if err != nil {
		var merr error
		mfile, merr = macho.Open(name)
		if merr != nil {
			return nil, err
		}
	}

	r := &file{elf: efile, macho: mfile}

	if efile != nil {
		r.dwarf, err = efile.DWARF()
	} else {
		r.dwarf, err = mfile.DWARF()
	}
	if err != nil {
		return nil, err
	}

	var syms []sym
	if efile != nil {
		esyms, err := efile.Symbols()
		if err != nil {
			return nil, err
		}
		syms = make([]sym, 0, len(esyms))
		for _, s := range esyms {
			if ST_TYPE(s.Info) == STT_FUNC {
				syms = append(syms, sym{s.Name, uintptr(s.Value)})
			}
		}
	} else {
		syms = make([]sym, 0, len(mfile.Symtab.Syms))
		for _, s := range mfile.Symtab.Syms {
			syms = append(syms, sym{s.Name, uintptr(s.Value)})
		}
	}

	r.symsByName = make([]sym, len(syms))
	copy(r.symsByName, syms)
	sort.Sort(symsByName(r.symsByName))

	r.symsByAddr = syms
	sort.Sort(symsByAddr(r.symsByAddr))

	return r, nil
}

func (dbp *Process) parseDebugLineInfo(exe *macho.File, wg *sync.WaitGroup) {
	defer wg.Done()

	if sec := exe.Section("__debug_line"); sec != nil {
		debugLine, err := exe.Section("__debug_line").Data()
		if err != nil {
			fmt.Println("could not get __debug_line section", err)
			os.Exit(1)
		}
		dbp.lineInfo = line.Parse(debugLine)
	} else {
		fmt.Println("could not find __debug_line section in binary")
		os.Exit(1)
	}
}

func (dbp *Process) parseDebugFrame(exe *macho.File, wg *sync.WaitGroup) {
	defer wg.Done()

	if sec := exe.Section("__debug_frame"); sec != nil {
		debugFrame, err := exe.Section("__debug_frame").Data()
		if err != nil {
			fmt.Println("could not get __debug_frame section", err)
			os.Exit(1)
		}
		dbp.frameEntries = frame.Parse(debugFrame)
	} else {
		fmt.Println("could not find __debug_frame section in binary")
		os.Exit(1)
	}
}

//============================================================================
//		main : Entry point.
//----------------------------------------------------------------------------
func main() {

	var dwarfData *dwarf.Data
	var theFile *macho.File
	var theErr os.Error
	var relativeAddress uint64
	var runtimeAddress uint64
	var loadAddress uint64
	var segmentAddress uint64
	var pathMacho string
	var pathDsym string

	// Parse our arguments
	flag.Uint64Var(&runtimeAddress, "raddr", 0, "")
	flag.Uint64Var(&loadAddress, "laddr", 0, "")
	flag.StringVar(&pathMacho, "macho", "", "")
	flag.StringVar(&pathDsym, "dsym", "", "")
	flag.Parse()

	if runtimeAddress == 0 || loadAddress == 0 || pathMacho == "" || pathDsym == "" {
		printHelp()
	}

	// Find the text segment address
	theFile, theErr = macho.Open(pathMacho)
	if theErr != nil {
		fatalError("Can't open Mach-O file: " + theErr.String())
	}

	segmentAddress = theFile.Segment("__TEXT").Addr

	theFile.Close()

	// Calculate the target address
	relativeAddress = runtimeAddress - loadAddress
	gTargetAddress = segmentAddress + relativeAddress

	// Find the target
	theFile, theErr = macho.Open(pathDsym)
	if theErr != nil {
		fatalError("Can't open .dsym file: " + theErr.String())
	}

	dwarfData, theErr = theFile.DWARF()
	if theErr != nil {
		fatalError("Can't find DWARF info: " + theErr.String())
	}

	processChildren(dwarfData.Reader(), 0, false)

	theFile.Close()
}

func (dbp *Process) obtainGoSymbols(exe *macho.File, wg *sync.WaitGroup) {
	defer wg.Done()

	var (
		symdat  []byte
		pclndat []byte
		err     error
	)

	if sec := exe.Section("__gosymtab"); sec != nil {
		symdat, err = sec.Data()
		if err != nil {
			fmt.Println("could not get .gosymtab section", err)
			os.Exit(1)
		}
	}

	if sec := exe.Section("__gopclntab"); sec != nil {
		pclndat, err = sec.Data()
		if err != nil {
			fmt.Println("could not get .gopclntab section", err)
			os.Exit(1)
		}
	}

	pcln := gosym.NewLineTable(pclndat, exe.Section("__text").Addr)
	tab, err := gosym.NewTable(symdat, pcln)
	if err != nil {
		fmt.Println("could not get initialize line table", err)
		os.Exit(1)
	}

	dbp.goSymTable = tab
}