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

Documentation: cmd/internal/objfile

  // Copyright 2014 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.
  
  // Package objfile implements portable access to OS-specific executable files.
  package objfile
  
  import (
  	"debug/dwarf"
  	"debug/gosym"
  	"fmt"
  	"io"
  	"os"
  	"sort"
  )
  
  type rawFile interface {
  	symbols() (syms []Sym, err error)
  	pcln() (textStart uint64, symtab, pclntab []byte, err error)
  	text() (textStart uint64, text []byte, err error)
  	goarch() string
  	loadAddress() (uint64, error)
  	dwarf() (*dwarf.Data, error)
  }
  
  // A File is an opened executable file.
  type File struct {
  	r       *os.File
  	entries []*Entry
  }
  
  type Entry struct {
  	name string
  	raw  rawFile
  }
  
  // A Sym is a symbol defined in an executable file.
  type Sym struct {
  	Name   string  // symbol name
  	Addr   uint64  // virtual address of symbol
  	Size   int64   // size in bytes
  	Code   rune    // nm code (T for text, D for data, and so on)
  	Type   string  // XXX?
  	Relocs []Reloc // in increasing Addr order
  }
  
  type Reloc struct {
  	Addr     uint64 // Address of first byte that reloc applies to.
  	Size     uint64 // Number of bytes
  	Stringer RelocStringer
  }
  
  type RelocStringer interface {
  	// insnOffset is the offset of the instruction containing the relocation
  	// from the start of the symbol containing the relocation.
  	String(insnOffset uint64) string
  }
  
  var openers = []func(io.ReaderAt) (rawFile, error){
  	openElf,
  	openMacho,
  	openPE,
  	openPlan9,
  }
  
  // Open opens the named file.
  // The caller must call f.Close when the file is no longer needed.
  func Open(name string) (*File, error) {
  	r, err := os.Open(name)
  	if err != nil {
  		return nil, err
  	}
  	if f, err := openGoFile(r); err == nil {
  		return f, nil
  	}
  	for _, try := range openers {
  		if raw, err := try(r); err == nil {
  			return &File{r, []*Entry{&Entry{raw: raw}}}, nil
  		}
  	}
  	r.Close()
  	return nil, fmt.Errorf("open %s: unrecognized object file", name)
  }
  
  func (f *File) Close() error {
  	return f.r.Close()
  }
  
  func (f *File) Entries() []*Entry {
  	return f.entries
  }
  
  func (f *File) Symbols() ([]Sym, error) {
  	return f.entries[0].Symbols()
  }
  
  func (f *File) PCLineTable() (Liner, error) {
  	return f.entries[0].PCLineTable()
  }
  
  func (f *File) Text() (uint64, []byte, error) {
  	return f.entries[0].Text()
  }
  
  func (f *File) GOARCH() string {
  	return f.entries[0].GOARCH()
  }
  
  func (f *File) LoadAddress() (uint64, error) {
  	return f.entries[0].LoadAddress()
  }
  
  func (f *File) DWARF() (*dwarf.Data, error) {
  	return f.entries[0].DWARF()
  }
  
  func (f *File) Disasm() (*Disasm, error) {
  	return f.entries[0].Disasm()
  }
  
  func (e *Entry) Name() string {
  	return e.name
  }
  
  func (e *Entry) Symbols() ([]Sym, error) {
  	syms, err := e.raw.symbols()
  	if err != nil {
  		return nil, err
  	}
  	sort.Sort(byAddr(syms))
  	return syms, nil
  }
  
  type byAddr []Sym
  
  func (x byAddr) Less(i, j int) bool { return x[i].Addr < x[j].Addr }
  func (x byAddr) Len() int           { return len(x) }
  func (x byAddr) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
  
  func (e *Entry) PCLineTable() (Liner, error) {
  	// If the raw file implements Liner directly, use that.
  	// Currently, only Go intermediate objects and archives (goobj) use this path.
  	if pcln, ok := e.raw.(Liner); ok {
  		return pcln, nil
  	}
  	// Otherwise, read the pcln tables and build a Liner out of that.
  	textStart, symtab, pclntab, err := e.raw.pcln()
  	if err != nil {
  		return nil, err
  	}
  	return gosym.NewTable(symtab, gosym.NewLineTable(pclntab, textStart))
  }
  
  func (e *Entry) Text() (uint64, []byte, error) {
  	return e.raw.text()
  }
  
  func (e *Entry) GOARCH() string {
  	return e.raw.goarch()
  }
  
  // LoadAddress returns the expected load address of the file.
  // This differs from the actual load address for a position-independent
  // executable.
  func (e *Entry) LoadAddress() (uint64, error) {
  	return e.raw.loadAddress()
  }
  
  // DWARF returns DWARF debug data for the file, if any.
  // This is for cmd/pprof to locate cgo functions.
  func (e *Entry) DWARF() (*dwarf.Data, error) {
  	return e.raw.dwarf()
  }
  

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