Source file src/pkg/debug/dwarf/open.go
1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 // Package dwarf provides access to DWARF debugging information loaded from
6 // executable files, as defined in the DWARF 2.0 Standard at
7 // http://dwarfstd.org/doc/dwarf-2.0.0.pdf
8 package dwarf
9
10 import "encoding/binary"
11
12 // Data represents the DWARF debugging information
13 // loaded from an executable file (for example, an ELF or Mach-O executable).
14 type Data struct {
15 // raw data
16 abbrev []byte
17 aranges []byte
18 frame []byte
19 info []byte
20 line []byte
21 pubnames []byte
22 ranges []byte
23 str []byte
24
25 // parsed data
26 abbrevCache map[uint32]abbrevTable
27 addrsize int
28 order binary.ByteOrder
29 typeCache map[Offset]Type
30 unit []unit
31 }
32
33 // New returns a new Data object initialized from the given parameters.
34 // Rather than calling this function directly, clients should typically use
35 // the DWARF method of the File type of the appropriate package debug/elf,
36 // debug/macho, or debug/pe.
37 //
38 // The []byte arguments are the data from the corresponding debug section
39 // in the object file; for example, for an ELF object, abbrev is the contents of
40 // the ".debug_abbrev" section.
41 func New(abbrev, aranges, frame, info, line, pubnames, ranges, str []byte) (*Data, error) {
42 d := &Data{
43 abbrev: abbrev,
44 aranges: aranges,
45 frame: frame,
46 info: info,
47 line: line,
48 pubnames: pubnames,
49 ranges: ranges,
50 str: str,
51 abbrevCache: make(map[uint32]abbrevTable),
52 typeCache: make(map[Offset]Type),
53 }
54
55 // Sniff .debug_info to figure out byte order.
56 // bytes 4:6 are the version, a tiny 16-bit number (1, 2, 3).
57 if len(d.info) < 6 {
58 return nil, DecodeError{"info", Offset(len(d.info)), "too short"}
59 }
60 x, y := d.info[4], d.info[5]
61 switch {
62 case x == 0 && y == 0:
63 return nil, DecodeError{"info", 4, "unsupported version 0"}
64 case x == 0:
65 d.order = binary.BigEndian
66 case y == 0:
67 d.order = binary.LittleEndian
68 default:
69 return nil, DecodeError{"info", 4, "cannot determine byte order"}
70 }
71
72 u, err := d.parseUnits()
73 if err != nil {
74 return nil, err
75 }
76 d.unit = u
77 return d, nil
78 }