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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Parsing of PE executables (Microsoft Windows).
package objfile
import (
"debug/dwarf"
"debug/pe"
"fmt"
"os"
"sort"
)
type peFile struct {
pe *pe.File
}
func openPE(r *os.File) (rawFile, error) {
f, err := pe.NewFile(r)
if err != nil {
return nil, err
}
switch f.OptionalHeader.(type) {
case *pe.OptionalHeader32, *pe.OptionalHeader64:
// ok
default:
return nil, fmt.Errorf("unrecognized PE format")
}
return &peFile{f}, nil
}
func (f *peFile) symbols() ([]Sym, error) {
// Build sorted list of addresses of all symbols.
// We infer the size of a symbol by looking at where the next symbol begins.
var addrs []uint64
var imageBase uint64
switch oh := f.pe.OptionalHeader.(type) {
case *pe.OptionalHeader32:
imageBase = uint64(oh.ImageBase)
case *pe.OptionalHeader64:
imageBase = oh.ImageBase
}
var syms []Sym
for _, s := range f.pe.Symbols {
const (
N_UNDEF = 0 // An undefined (extern) symbol
N_ABS = -1 // An absolute symbol (e_value is a constant, not an address)
N_DEBUG = -2 // A debugging symbol
)
sym := Sym{Name: s.Name, Addr: uint64(s.Value), Code: '?'}
switch s.SectionNumber {
case N_UNDEF:
sym.Code = 'U'
case N_ABS:
sym.Code = 'C'
case N_DEBUG:
sym.Code = '?'
default:
if s.SectionNumber < 0 || len(f.pe.Sections) < int(s.SectionNumber) {
return nil, fmt.Errorf("invalid section number in symbol table")
}
sect := f.pe.Sections[s.SectionNumber-1]
const (
text = 0x20
data = 0x40
bss = 0x80
permW = 0x80000000
)
ch := sect.Characteristics
switch {
case ch&text != 0:
sym.Code = 'T'
case ch&data != 0:
if ch&permW == 0 {
sym.Code = 'R'
} else {
sym.Code = 'D'
}
case ch&bss != 0:
sym.Code = 'B'
}
sym.Addr += imageBase + uint64(sect.VirtualAddress)
}
syms = append(syms, sym)
addrs = append(addrs, sym.Addr)
}
sort.Sort(uint64s(addrs))
for i := range syms {
j := sort.Search(len(addrs), func(x int) bool { return addrs[x] > syms[i].Addr })
if j < len(addrs) {
syms[i].Size = int64(addrs[j] - syms[i].Addr)
}
}
return syms, nil
}
func (f *peFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
var imageBase uint64
switch oh := f.pe.OptionalHeader.(type) {
case *pe.OptionalHeader32:
imageBase = uint64(oh.ImageBase)
case *pe.OptionalHeader64:
imageBase = oh.ImageBase
default:
return 0, nil, nil, fmt.Errorf("pe file format not recognized")
}
if sect := f.pe.Section(".text"); sect != nil {
textStart = imageBase + uint64(sect.VirtualAddress)
}
if pclntab, err = loadPETable(f.pe, "runtime.pclntab", "runtime.epclntab"); err != nil {
// We didn't find the symbols, so look for the names used in 1.3 and earlier.
// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
var err2 error
if pclntab, err2 = loadPETable(f.pe, "pclntab", "epclntab"); err2 != nil {
return 0, nil, nil, err
}
}
if symtab, err = loadPETable(f.pe, "runtime.symtab", "runtime.esymtab"); err != nil {
// Same as above.
var err2 error
if symtab, err2 = loadPETable(f.pe, "symtab", "esymtab"); err2 != nil {
return 0, nil, nil, err
}
}
return textStart, symtab, pclntab, nil
}
func (f *peFile) text() (textStart uint64, text []byte, err error) {
var imageBase uint64
switch oh := f.pe.OptionalHeader.(type) {
case *pe.OptionalHeader32:
imageBase = uint64(oh.ImageBase)
case *pe.OptionalHeader64:
imageBase = oh.ImageBase
default:
return 0, nil, fmt.Errorf("pe file format not recognized")
}
sect := f.pe.Section(".text")
if sect == nil {
return 0, nil, fmt.Errorf("text section not found")
}
textStart = imageBase + uint64(sect.VirtualAddress)
text, err = sect.Data()
return
}
func findPESymbol(f *pe.File, name string) (*pe.Symbol, error) {
for _, s := range f.Symbols {
if s.Name != name {
continue
}
if s.SectionNumber <= 0 {
return nil, fmt.Errorf("symbol %s: invalid section number %d", name, s.SectionNumber)
}
if len(f.Sections) < int(s.SectionNumber) {
return nil, fmt.Errorf("symbol %s: section number %d is larger than max %d", name, s.SectionNumber, len(f.Sections))
}
return s, nil
}
return nil, fmt.Errorf("no %s symbol found", name)
}
func loadPETable(f *pe.File, sname, ename string) ([]byte, error) {
ssym, err := findPESymbol(f, sname)
if err != nil {
return nil, err
}
esym, err := findPESymbol(f, ename)
if err != nil {
return nil, err
}
if ssym.SectionNumber != esym.SectionNumber {
return nil, fmt.Errorf("%s and %s symbols must be in the same section", sname, ename)
}
sect := f.Sections[ssym.SectionNumber-1]
data, err := sect.Data()
if err != nil {
return nil, err
}
return data[ssym.Value:esym.Value], nil
}
func (f *peFile) goarch() string {
// Not sure how to get the info we want from PE header.
// Look in symbol table for telltale rt0 symbol.
if _, err := findPESymbol(f.pe, "_rt0_386_windows"); err == nil {
return "386"
}
if _, err := findPESymbol(f.pe, "_rt0_amd64_windows"); err == nil {
return "amd64"
}
return ""
}
func (f *peFile) loadAddress() (uint64, error) {
return 0, fmt.Errorf("unknown load address")
}
func (f *peFile) dwarf() (*dwarf.Data, error) {
return f.pe.DWARF()
}
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