plan9obj.go

     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/dwarf"
    11  	"debug/plan9obj"
    12  	"errors"
    13  	"fmt"
    14  	"io"
    15  	"sort"
    16  )
    17  
    18  var validSymType = map[rune]bool{
    19  	'T': true,
    20  	't': true,
    21  	'D': true,
    22  	'd': true,
    23  	'B': true,
    24  	'b': true,
    25  }
    26  
    27  type plan9File struct {
    28  	plan9 *plan9obj.File
    29  }
    30  
    31  func openPlan9(r io.ReaderAt) (rawFile, error) {
    32  	f, err := plan9obj.NewFile(r)
    33  	if err != nil {
    34  		return nil, err
    35  	}
    36  	return &plan9File{f}, nil
    37  }
    38  
    39  func (f *plan9File) symbols() ([]Sym, error) {
    40  	plan9Syms, err := f.plan9.Symbols()
    41  	if err != nil {
    42  		return nil, err
    43  	}
    44  
    45  	// Build sorted list of addresses of all symbols.
    46  	// We infer the size of a symbol by looking at where the next symbol begins.
    47  	var addrs []uint64
    48  	for _, s := range plan9Syms {
    49  		if !validSymType[s.Type] {
    50  			continue
    51  		}
    52  		addrs = append(addrs, s.Value)
    53  	}
    54  	sort.Sort(uint64s(addrs))
    55  
    56  	var syms []Sym
    57  
    58  	for _, s := range plan9Syms {
    59  		if !validSymType[s.Type] {
    60  			continue
    61  		}
    62  		sym := Sym{Addr: s.Value, Name: s.Name, Code: s.Type}
    63  		i := sort.Search(len(addrs), func(x int) bool { return addrs[x] > s.Value })
    64  		if i < len(addrs) {
    65  			sym.Size = int64(addrs[i] - s.Value)
    66  		}
    67  		syms = append(syms, sym)
    68  	}
    69  
    70  	return syms, nil
    71  }
    72  
    73  func (f *plan9File) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
    74  	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
    75  	if pclntab, err = loadPlan9Table(f.plan9, "runtime.pclntab", "runtime.epclntab"); err != nil {
    76  		// We didn't find the symbols, so look for the names used in 1.3 and earlier.
    77  		// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
    78  		var err2 error
    79  		if pclntab, err2 = loadPlan9Table(f.plan9, "pclntab", "epclntab"); err2 != nil {
    80  			return 0, nil, nil, err
    81  		}
    82  	}
    83  	if symtab, err = loadPlan9Table(f.plan9, "runtime.symtab", "runtime.esymtab"); err != nil {
    84  		// Same as above.
    85  		var err2 error
    86  		if symtab, err2 = loadPlan9Table(f.plan9, "symtab", "esymtab"); err2 != nil {
    87  			return 0, nil, nil, err
    88  		}
    89  	}
    90  	return textStart, symtab, pclntab, nil
    91  }
    92  
    93  func (f *plan9File) text() (textStart uint64, text []byte, err error) {
    94  	sect := f.plan9.Section("text")
    95  	if sect == nil {
    96  		return 0, nil, fmt.Errorf("text section not found")
    97  	}
    98  	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
    99  	text, err = sect.Data()
   100  	return
   101  }
   102  
   103  func findPlan9Symbol(f *plan9obj.File, name string) (*plan9obj.Sym, error) {
   104  	syms, err := f.Symbols()
   105  	if err != nil {
   106  		return nil, err
   107  	}
   108  	for _, s := range syms {
   109  		if s.Name != name {
   110  			continue
   111  		}
   112  		return &s, nil
   113  	}
   114  	return nil, fmt.Errorf("no %s symbol found", name)
   115  }
   116  
   117  func loadPlan9Table(f *plan9obj.File, sname, ename string) ([]byte, error) {
   118  	ssym, err := findPlan9Symbol(f, sname)
   119  	if err != nil {
   120  		return nil, err
   121  	}
   122  	esym, err := findPlan9Symbol(f, ename)
   123  	if err != nil {
   124  		return nil, err
   125  	}
   126  	sect := f.Section("text")
   127  	if sect == nil {
   128  		return nil, err
   129  	}
   130  	data, err := sect.Data()
   131  	if err != nil {
   132  		return nil, err
   133  	}
   134  	textStart := f.LoadAddress + f.HdrSize
   135  	return data[ssym.Value-textStart : esym.Value-textStart], nil
   136  }
   137  
   138  func (f *plan9File) goarch() string {
   139  	switch f.plan9.Magic {
   140  	case plan9obj.Magic386:
   141  		return "386"
   142  	case plan9obj.MagicAMD64:
   143  		return "amd64"
   144  	case plan9obj.MagicARM:
   145  		return "arm"
   146  	}
   147  	return ""
   148  }
   149  
   150  func (f *plan9File) loadAddress() (uint64, error) {
   151  	return 0, fmt.Errorf("unknown load address")
   152  }
   153  
   154  func (f *plan9File) dwarf() (*dwarf.Data, error) {
   155  	return nil, errors.New("no DWARF data in Plan 9 file")
   156  }
   157
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