github.com/FenixAra/go@v0.0.0-20170127160404-96ea0918e670/src/cmd/internal/objfile/objfile.go (about)

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