1// Copyright 2014 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 objfile implements portable access to OS-specific executable files.
6package objfile
7
8import (
9	"debug/dwarf"
10	"debug/gosym"
11	"fmt"
12	"io"
13	"os"
14	"sort"
15)
16
17type rawFile interface {
18	symbols() (syms []Sym, err error)
19	pcln() (textStart uint64, symtab, pclntab []byte, err error)
20	text() (textStart uint64, text []byte, err error)
21	goarch() string
22	loadAddress() (uint64, error)
23	dwarf() (*dwarf.Data, error)
24}
25
26// A File is an opened executable file.
27type File struct {
28	r       *os.File
29	entries []*Entry
30}
31
32type Entry struct {
33	name string
34	raw  rawFile
35}
36
37// A Sym is a symbol defined in an executable file.
38type Sym struct {
39	Name   string  // symbol name
40	Addr   uint64  // virtual address of symbol
41	Size   int64   // size in bytes
42	Code   rune    // nm code (T for text, D for data, and so on)
43	Type   string  // XXX?
44	Relocs []Reloc // in increasing Addr order
45}
46
47type Reloc struct {
48	Addr     uint64 // Address of first byte that reloc applies to.
49	Size     uint64 // Number of bytes
50	Stringer RelocStringer
51}
52
53type RelocStringer interface {
54	// insnOffset is the offset of the instruction containing the relocation
55	// from the start of the symbol containing the relocation.
56	String(insnOffset uint64) string
57}
58
59var openers = []func(io.ReaderAt) (rawFile, error){
60	openElf,
61	openMacho,
62	openPE,
63	openPlan9,
64	openXcoff,
65}
66
67// Open opens the named file.
68// The caller must call f.Close when the file is no longer needed.
69func Open(name string) (*File, error) {
70	r, err := os.Open(name)
71	if err != nil {
72		return nil, err
73	}
74	if f, err := openGoFile(r); err == nil {
75		return f, nil
76	}
77	for _, try := range openers {
78		if raw, err := try(r); err == nil {
79			return &File{r, []*Entry{{raw: raw}}}, nil
80		}
81	}
82	r.Close()
83	return nil, fmt.Errorf("open %s: unrecognized object file", name)
84}
85
86func (f *File) Close() error {
87	return f.r.Close()
88}
89
90func (f *File) Entries() []*Entry {
91	return f.entries
92}
93
94func (f *File) Symbols() ([]Sym, error) {
95	return f.entries[0].Symbols()
96}
97
98func (f *File) PCLineTable() (Liner, error) {
99	return f.entries[0].PCLineTable()
100}
101
102func (f *File) Text() (uint64, []byte, error) {
103	return f.entries[0].Text()
104}
105
106func (f *File) GOARCH() string {
107	return f.entries[0].GOARCH()
108}
109
110func (f *File) LoadAddress() (uint64, error) {
111	return f.entries[0].LoadAddress()
112}
113
114func (f *File) DWARF() (*dwarf.Data, error) {
115	return f.entries[0].DWARF()
116}
117
118func (f *File) Disasm() (*Disasm, error) {
119	return f.entries[0].Disasm()
120}
121
122func (e *Entry) Name() string {
123	return e.name
124}
125
126func (e *Entry) Symbols() ([]Sym, error) {
127	syms, err := e.raw.symbols()
128	if err != nil {
129		return nil, err
130	}
131	sort.Sort(byAddr(syms))
132	return syms, nil
133}
134
135type byAddr []Sym
136
137func (x byAddr) Less(i, j int) bool { return x[i].Addr < x[j].Addr }
138func (x byAddr) Len() int           { return len(x) }
139func (x byAddr) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
140
141func (e *Entry) PCLineTable() (Liner, error) {
142	// If the raw file implements Liner directly, use that.
143	// Currently, only Go intermediate objects and archives (goobj) use this path.
144	if pcln, ok := e.raw.(Liner); ok {
145		return pcln, nil
146	}
147	// Otherwise, read the pcln tables and build a Liner out of that.
148	textStart, symtab, pclntab, err := e.raw.pcln()
149	if err != nil {
150		return nil, err
151	}
152	return gosym.NewTable(symtab, gosym.NewLineTable(pclntab, textStart))
153}
154
155func (e *Entry) Text() (uint64, []byte, error) {
156	return e.raw.text()
157}
158
159func (e *Entry) GOARCH() string {
160	return e.raw.goarch()
161}
162
163// LoadAddress returns the expected load address of the file.
164// This differs from the actual load address for a position-independent
165// executable.
166func (e *Entry) LoadAddress() (uint64, error) {
167	return e.raw.loadAddress()
168}
169
170// DWARF returns DWARF debug data for the file, if any.
171// This is for cmd/pprof to locate cgo functions.
172func (e *Entry) DWARF() (*dwarf.Data, error) {
173	return e.raw.dwarf()
174}
175