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  	"slices"
    16  	"sort"
    17  )
    18  
    19  var validSymType = map[rune]bool{
    20  	'T': true,
    21  	't': true,
    22  	'D': true,
    23  	'd': true,
    24  	'B': true,
    25  	'b': true,
    26  }
    27  
    28  type plan9File struct {
    29  	plan9 *plan9obj.File
    30  }
    31  
    32  func openPlan9(r io.ReaderAt) (rawFile, error) {
    33  	f, err := plan9obj.NewFile(r)
    34  	if err != nil {
    35  		return nil, err
    36  	}
    37  	return &plan9File{f}, nil
    38  }
    39  
    40  func (f *plan9File) symbols() ([]Sym, error) {
    41  	plan9Syms, err := f.plan9.Symbols()
    42  	if err != nil {
    43  		return nil, err
    44  	}
    45  
    46  	// Build sorted list of addresses of all symbols.
    47  	// We infer the size of a symbol by looking at where the next symbol begins.
    48  	var addrs []uint64
    49  	for _, s := range plan9Syms {
    50  		if !validSymType[s.Type] {
    51  			continue
    52  		}
    53  		addrs = append(addrs, s.Value)
    54  	}
    55  	slices.Sort(addrs)
    56  
    57  	var syms []Sym
    58  
    59  	for _, s := range plan9Syms {
    60  		if !validSymType[s.Type] {
    61  			continue
    62  		}
    63  		sym := Sym{Addr: s.Value, Name: s.Name, Code: s.Type}
    64  		i := sort.Search(len(addrs), func(x int) bool { return addrs[x] > s.Value })
    65  		if i < len(addrs) {
    66  			sym.Size = int64(addrs[i] - s.Value)
    67  		}
    68  		syms = append(syms, sym)
    69  	}
    70  
    71  	return syms, nil
    72  }
    73  
    74  func (f *plan9File) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
    75  	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
    76  	if pclntab, err = loadPlan9Table(f.plan9, "runtime.pclntab", "runtime.epclntab"); err != nil {
    77  		// We didn't find the symbols, so look for the names used in 1.3 and earlier.
    78  		// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
    79  		var err2 error
    80  		if pclntab, err2 = loadPlan9Table(f.plan9, "pclntab", "epclntab"); err2 != nil {
    81  			return 0, nil, nil, err
    82  		}
    83  	}
    84  	if symtab, err = loadPlan9Table(f.plan9, "runtime.symtab", "runtime.esymtab"); err != nil {
    85  		// Same as above.
    86  		var err2 error
    87  		if symtab, err2 = loadPlan9Table(f.plan9, "symtab", "esymtab"); err2 != nil {
    88  			return 0, nil, nil, err
    89  		}
    90  	}
    91  	return textStart, symtab, pclntab, nil
    92  }
    93  
    94  func (f *plan9File) text() (textStart uint64, text []byte, err error) {
    95  	sect := f.plan9.Section("text")
    96  	if sect == nil {
    97  		return 0, nil, fmt.Errorf("text section not found")
    98  	}
    99  	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
   100  	text, err = sect.Data()
   101  	return
   102  }
   103  
   104  func findPlan9Symbol(f *plan9obj.File, name string) (*plan9obj.Sym, error) {
   105  	syms, err := f.Symbols()
   106  	if err != nil {
   107  		return nil, err
   108  	}
   109  	for _, s := range syms {
   110  		if s.Name != name {
   111  			continue
   112  		}
   113  		return &s, nil
   114  	}
   115  	return nil, fmt.Errorf("no %s symbol found", name)
   116  }
   117  
   118  func loadPlan9Table(f *plan9obj.File, sname, ename string) ([]byte, error) {
   119  	ssym, err := findPlan9Symbol(f, sname)
   120  	if err != nil {
   121  		return nil, err
   122  	}
   123  	esym, err := findPlan9Symbol(f, ename)
   124  	if err != nil {
   125  		return nil, err
   126  	}
   127  	sect := f.Section("text")
   128  	if sect == nil {
   129  		return nil, err
   130  	}
   131  	data, err := sect.Data()
   132  	if err != nil {
   133  		return nil, err
   134  	}
   135  	textStart := f.LoadAddress + f.HdrSize
   136  	return data[ssym.Value-textStart : esym.Value-textStart], nil
   137  }
   138  
   139  func (f *plan9File) goarch() string {
   140  	switch f.plan9.Magic {
   141  	case plan9obj.Magic386:
   142  		return "386"
   143  	case plan9obj.MagicAMD64:
   144  		return "amd64"
   145  	case plan9obj.MagicARM:
   146  		return "arm"
   147  	}
   148  	return ""
   149  }
   150  
   151  func (f *plan9File) loadAddress() (uint64, error) {
   152  	return 0, fmt.Errorf("unknown load address")
   153  }
   154  
   155  func (f *plan9File) dwarf() (*dwarf.Data, error) {
   156  	return nil, errors.New("no DWARF data in Plan 9 file")
   157  }
   158
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