github.com/hbdrawn/golang@v0.0.0-20141214014649-6b835209aba2/src/cmd/internal/objfile/plan9obj.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  // Parsing of Plan 9 a.out executables.
     6  
     7  package objfile
     8  
     9  import (
    10  	"debug/plan9obj"
    11  	"fmt"
    12  	"os"
    13  	"sort"
    14  )
    15  
    16  var validSymType = map[rune]bool{
    17  	'T': true,
    18  	't': true,
    19  	'D': true,
    20  	'd': true,
    21  	'B': true,
    22  	'b': true,
    23  }
    24  
    25  type plan9File struct {
    26  	plan9 *plan9obj.File
    27  }
    28  
    29  func openPlan9(r *os.File) (rawFile, error) {
    30  	f, err := plan9obj.NewFile(r)
    31  	if err != nil {
    32  		return nil, err
    33  	}
    34  	return &plan9File{f}, nil
    35  }
    36  
    37  func (f *plan9File) symbols() ([]Sym, error) {
    38  	plan9Syms, err := f.plan9.Symbols()
    39  	if err != nil {
    40  		return nil, err
    41  	}
    42  
    43  	// Build sorted list of addresses of all symbols.
    44  	// We infer the size of a symbol by looking at where the next symbol begins.
    45  	var addrs []uint64
    46  	for _, s := range plan9Syms {
    47  		if !validSymType[s.Type] {
    48  			continue
    49  		}
    50  		addrs = append(addrs, s.Value)
    51  	}
    52  	sort.Sort(uint64s(addrs))
    53  
    54  	var syms []Sym
    55  
    56  	for _, s := range plan9Syms {
    57  		if !validSymType[s.Type] {
    58  			continue
    59  		}
    60  		sym := Sym{Addr: s.Value, Name: s.Name, Code: rune(s.Type)}
    61  		i := sort.Search(len(addrs), func(x int) bool { return addrs[x] > s.Value })
    62  		if i < len(addrs) {
    63  			sym.Size = int64(addrs[i] - s.Value)
    64  		}
    65  		syms = append(syms, sym)
    66  	}
    67  
    68  	return syms, nil
    69  }
    70  
    71  func (f *plan9File) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
    72  	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
    73  	if pclntab, err = loadPlan9Table(f.plan9, "runtime.pclntab", "runtime.epclntab"); err != nil {
    74  		// We didn't find the symbols, so look for the names used in 1.3 and earlier.
    75  		// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
    76  		var err2 error
    77  		if pclntab, err2 = loadPlan9Table(f.plan9, "pclntab", "epclntab"); err2 != nil {
    78  			return 0, nil, nil, err
    79  		}
    80  	}
    81  	if symtab, err = loadPlan9Table(f.plan9, "runtime.symtab", "runtime.esymtab"); err != nil {
    82  		// Same as above.
    83  		var err2 error
    84  		if symtab, err2 = loadPlan9Table(f.plan9, "symtab", "esymtab"); err2 != nil {
    85  			return 0, nil, nil, err
    86  		}
    87  	}
    88  	return textStart, symtab, pclntab, nil
    89  }
    90  
    91  func (f *plan9File) text() (textStart uint64, text []byte, err error) {
    92  	sect := f.plan9.Section("text")
    93  	if sect == nil {
    94  		return 0, nil, fmt.Errorf("text section not found")
    95  	}
    96  	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
    97  	text, err = sect.Data()
    98  	return
    99  }
   100  
   101  func findPlan9Symbol(f *plan9obj.File, name string) (*plan9obj.Sym, error) {
   102  	syms, err := f.Symbols()
   103  	if err != nil {
   104  		return nil, err
   105  	}
   106  	for _, s := range syms {
   107  		if s.Name != name {
   108  			continue
   109  		}
   110  		return &s, nil
   111  	}
   112  	return nil, fmt.Errorf("no %s symbol found", name)
   113  }
   114  
   115  func loadPlan9Table(f *plan9obj.File, sname, ename string) ([]byte, error) {
   116  	ssym, err := findPlan9Symbol(f, sname)
   117  	if err != nil {
   118  		return nil, err
   119  	}
   120  	esym, err := findPlan9Symbol(f, ename)
   121  	if err != nil {
   122  		return nil, err
   123  	}
   124  	sect := f.Section("text")
   125  	if sect == nil {
   126  		return nil, err
   127  	}
   128  	data, err := sect.Data()
   129  	if err != nil {
   130  		return nil, err
   131  	}
   132  	textStart := f.LoadAddress + f.HdrSize
   133  	return data[ssym.Value-textStart : esym.Value-textStart], nil
   134  }
   135  
   136  func (f *plan9File) goarch() string {
   137  	switch f.plan9.Magic {
   138  	case plan9obj.Magic386:
   139  		return "386"
   140  	case plan9obj.MagicAMD64:
   141  		return "amd64"
   142  	case plan9obj.MagicARM:
   143  		return "arm"
   144  	}
   145  	return ""
   146  }