// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package dwarf provides access to DWARF debugging information loaded from
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// executable files, as defined in the DWARF 2.0 Standard at
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// http://dwarfstd.org/doc/dwarf-2.0.0.pdf
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package dwarf
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import "encoding/binary"
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// Data represents the DWARF debugging information
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// loaded from an executable file (for example, an ELF or Mach-O executable).
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type Data struct {
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// raw data
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abbrev []byte
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aranges []byte
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frame []byte
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info []byte
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line []byte
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pubnames []byte
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ranges []byte
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str []byte
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// parsed data
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abbrevCache map[uint64]abbrevTable
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order binary.ByteOrder
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typeCache map[Offset]Type
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typeSigs map[uint64]*typeUnit
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unit []unit
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}
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// New returns a new Data object initialized from the given parameters.
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// Rather than calling this function directly, clients should typically use
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// the DWARF method of the File type of the appropriate package debug/elf,
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// debug/macho, or debug/pe.
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//
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// The []byte arguments are the data from the corresponding debug section
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// in the object file; for example, for an ELF object, abbrev is the contents of
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// the ".debug_abbrev" section.
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func New(abbrev, aranges, frame, info, line, pubnames, ranges, str []byte) (*Data, error) {
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d := &Data{
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abbrev: abbrev,
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aranges: aranges,
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frame: frame,
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info: info,
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line: line,
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pubnames: pubnames,
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ranges: ranges,
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str: str,
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abbrevCache: make(map[uint64]abbrevTable),
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typeCache: make(map[Offset]Type),
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typeSigs: make(map[uint64]*typeUnit),
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}
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// Sniff .debug_info to figure out byte order.
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// 32-bit DWARF: 4 byte length, 2 byte version.
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// 64-bit DWARf: 4 bytes of 0xff, 8 byte length, 2 byte version.
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if len(d.info) < 6 {
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return nil, DecodeError{"info", Offset(len(d.info)), "too short"}
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}
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offset := 4
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if d.info[0] == 0xff && d.info[1] == 0xff && d.info[2] == 0xff && d.info[3] == 0xff {
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if len(d.info) < 14 {
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return nil, DecodeError{"info", Offset(len(d.info)), "too short"}
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}
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offset = 12
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}
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// Fetch the version, a tiny 16-bit number (1, 2, 3, 4, 5).
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x, y := d.info[offset], d.info[offset+1]
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switch {
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case x == 0 && y == 0:
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return nil, DecodeError{"info", 4, "unsupported version 0"}
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case x == 0:
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d.order = binary.BigEndian
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case y == 0:
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d.order = binary.LittleEndian
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default:
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return nil, DecodeError{"info", 4, "cannot determine byte order"}
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}
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u, err := d.parseUnits()
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if err != nil {
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return nil, err
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}
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d.unit = u
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return d, nil
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}
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// AddTypes will add one .debug_types section to the DWARF data. A
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// typical object with DWARF version 4 debug info will have multiple
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// .debug_types sections. The name is used for error reporting only,
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// and serves to distinguish one .debug_types section from another.
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func (d *Data) AddTypes(name string, types []byte) error {
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return d.parseTypes(name, types)
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}
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