pe.go

Documentation: cmd/internal/objfile

     1  // Copyright 2013 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  // Parsing of PE executables (Microsoft Windows).
     6  
     7  package objfile
     8  
     9  import (
    10  	"debug/dwarf"
    11  	"debug/pe"
    12  	"fmt"
    13  	"io"
    14  	"sort"
    15  )
    16  
    17  type peFile struct {
    18  	pe *pe.File
    19  }
    20  
    21  func openPE(r io.ReaderAt) (rawFile, error) {
    22  	f, err := pe.NewFile(r)
    23  	if err != nil {
    24  		return nil, err
    25  	}
    26  	return &peFile{f}, nil
    27  }
    28  
    29  func (f *peFile) symbols() ([]Sym, error) {
    30  	// Build sorted list of addresses of all symbols.
    31  	// We infer the size of a symbol by looking at where the next symbol begins.
    32  	var addrs []uint64
    33  
    34  	var imageBase uint64
    35  	switch oh := f.pe.OptionalHeader.(type) {
    36  	case *pe.OptionalHeader32:
    37  		imageBase = uint64(oh.ImageBase)
    38  	case *pe.OptionalHeader64:
    39  		imageBase = oh.ImageBase
    40  	}
    41  
    42  	var syms []Sym
    43  	for _, s := range f.pe.Symbols {
    44  		const (
    45  			N_UNDEF = 0  // An undefined (extern) symbol
    46  			N_ABS   = -1 // An absolute symbol (e_value is a constant, not an address)
    47  			N_DEBUG = -2 // A debugging symbol
    48  		)
    49  		sym := Sym{Name: s.Name, Addr: uint64(s.Value), Code: '?'}
    50  		switch s.SectionNumber {
    51  		case N_UNDEF:
    52  			sym.Code = 'U'
    53  		case N_ABS:
    54  			sym.Code = 'C'
    55  		case N_DEBUG:
    56  			sym.Code = '?'
    57  		default:
    58  			if s.SectionNumber < 0 || len(f.pe.Sections) < int(s.SectionNumber) {
    59  				return nil, fmt.Errorf("invalid section number in symbol table")
    60  			}
    61  			sect := f.pe.Sections[s.SectionNumber-1]
    62  			const (
    63  				text  = 0x20
    64  				data  = 0x40
    65  				bss   = 0x80
    66  				permW = 0x80000000
    67  			)
    68  			ch := sect.Characteristics
    69  			switch {
    70  			case ch&text != 0:
    71  				sym.Code = 'T'
    72  			case ch&data != 0:
    73  				if ch&permW == 0 {
    74  					sym.Code = 'R'
    75  				} else {
    76  					sym.Code = 'D'
    77  				}
    78  			case ch&bss != 0:
    79  				sym.Code = 'B'
    80  			}
    81  			sym.Addr += imageBase + uint64(sect.VirtualAddress)
    82  		}
    83  		syms = append(syms, sym)
    84  		addrs = append(addrs, sym.Addr)
    85  	}
    86  
    87  	sort.Sort(uint64s(addrs))
    88  	for i := range syms {
    89  		j := sort.Search(len(addrs), func(x int) bool { return addrs[x] > syms[i].Addr })
    90  		if j < len(addrs) {
    91  			syms[i].Size = int64(addrs[j] - syms[i].Addr)
    92  		}
    93  	}
    94  
    95  	return syms, nil
    96  }
    97  
    98  func (f *peFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
    99  	var imageBase uint64
   100  	switch oh := f.pe.OptionalHeader.(type) {
   101  	case *pe.OptionalHeader32:
   102  		imageBase = uint64(oh.ImageBase)
   103  	case *pe.OptionalHeader64:
   104  		imageBase = oh.ImageBase
   105  	default:
   106  		return 0, nil, nil, fmt.Errorf("pe file format not recognized")
   107  	}
   108  	if sect := f.pe.Section(".text"); sect != nil {
   109  		textStart = imageBase + uint64(sect.VirtualAddress)
   110  	}
   111  	if pclntab, err = loadPETable(f.pe, "runtime.pclntab", "runtime.epclntab"); err != nil {
   112  		// We didn't find the symbols, so look for the names used in 1.3 and earlier.
   113  		// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
   114  		var err2 error
   115  		if pclntab, err2 = loadPETable(f.pe, "pclntab", "epclntab"); err2 != nil {
   116  			return 0, nil, nil, err
   117  		}
   118  	}
   119  	if symtab, err = loadPETable(f.pe, "runtime.symtab", "runtime.esymtab"); err != nil {
   120  		// Same as above.
   121  		var err2 error
   122  		if symtab, err2 = loadPETable(f.pe, "symtab", "esymtab"); err2 != nil {
   123  			return 0, nil, nil, err
   124  		}
   125  	}
   126  	return textStart, symtab, pclntab, nil
   127  }
   128  
   129  func (f *peFile) text() (textStart uint64, text []byte, err error) {
   130  	var imageBase uint64
   131  	switch oh := f.pe.OptionalHeader.(type) {
   132  	case *pe.OptionalHeader32:
   133  		imageBase = uint64(oh.ImageBase)
   134  	case *pe.OptionalHeader64:
   135  		imageBase = oh.ImageBase
   136  	default:
   137  		return 0, nil, fmt.Errorf("pe file format not recognized")
   138  	}
   139  	sect := f.pe.Section(".text")
   140  	if sect == nil {
   141  		return 0, nil, fmt.Errorf("text section not found")
   142  	}
   143  	textStart = imageBase + uint64(sect.VirtualAddress)
   144  	text, err = sect.Data()
   145  	return
   146  }
   147  
   148  func findPESymbol(f *pe.File, name string) (*pe.Symbol, error) {
   149  	for _, s := range f.Symbols {
   150  		if s.Name != name {
   151  			continue
   152  		}
   153  		if s.SectionNumber <= 0 {
   154  			return nil, fmt.Errorf("symbol %s: invalid section number %d", name, s.SectionNumber)
   155  		}
   156  		if len(f.Sections) < int(s.SectionNumber) {
   157  			return nil, fmt.Errorf("symbol %s: section number %d is larger than max %d", name, s.SectionNumber, len(f.Sections))
   158  		}
   159  		return s, nil
   160  	}
   161  	return nil, fmt.Errorf("no %s symbol found", name)
   162  }
   163  
   164  func loadPETable(f *pe.File, sname, ename string) ([]byte, error) {
   165  	ssym, err := findPESymbol(f, sname)
   166  	if err != nil {
   167  		return nil, err
   168  	}
   169  	esym, err := findPESymbol(f, ename)
   170  	if err != nil {
   171  		return nil, err
   172  	}
   173  	if ssym.SectionNumber != esym.SectionNumber {
   174  		return nil, fmt.Errorf("%s and %s symbols must be in the same section", sname, ename)
   175  	}
   176  	sect := f.Sections[ssym.SectionNumber-1]
   177  	data, err := sect.Data()
   178  	if err != nil {
   179  		return nil, err
   180  	}
   181  	return data[ssym.Value:esym.Value], nil
   182  }
   183  
   184  func (f *peFile) goarch() string {
   185  	switch f.pe.Machine {
   186  	case pe.IMAGE_FILE_MACHINE_I386:
   187  		return "386"
   188  	case pe.IMAGE_FILE_MACHINE_AMD64:
   189  		return "amd64"
   190  	case pe.IMAGE_FILE_MACHINE_ARMNT:
   191  		return "arm"
   192  	case pe.IMAGE_FILE_MACHINE_ARM64:
   193  		return "arm64"
   194  	default:
   195  		return ""
   196  	}
   197  }
   198  
   199  func (f *peFile) loadAddress() (uint64, error) {
   200  	return 0, fmt.Errorf("unknown load address")
   201  }
   202  
   203  func (f *peFile) dwarf() (*dwarf.Data, error) {
   204  	return f.pe.DWARF()
   205  }
   206
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