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Source file src/cmd/internal/objfile/pe.go

Documentation: cmd/internal/objfile

  // 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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