github.com/westcoastroms/westcoastroms-build@v0.0.0-20190928114312-2350e5a73030/build/soong/cmd/symbol_inject/macho.go (about)

     1  // Copyright 2018 Google Inc. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package main
    16  
    17  import (
    18  	"debug/macho"
    19  	"fmt"
    20  	"io"
    21  	"sort"
    22  	"strings"
    23  )
    24  
    25  func machoSymbolsFromFile(r io.ReaderAt) (*File, error) {
    26  	machoFile, err := macho.NewFile(r)
    27  	if err != nil {
    28  		return nil, cantParseError{err}
    29  	}
    30  
    31  	return extractMachoSymbols(machoFile)
    32  }
    33  
    34  func extractMachoSymbols(machoFile *macho.File) (*File, error) {
    35  	symbols := machoFile.Symtab.Syms
    36  	sort.SliceStable(symbols, func(i, j int) bool {
    37  		if symbols[i].Sect != symbols[j].Sect {
    38  			return symbols[i].Sect < symbols[j].Sect
    39  		}
    40  		return symbols[i].Value < symbols[j].Value
    41  	})
    42  
    43  	file := &File{}
    44  
    45  	for _, section := range machoFile.Sections {
    46  		file.Sections = append(file.Sections, &Section{
    47  			Name:   section.Name,
    48  			Addr:   section.Addr,
    49  			Offset: uint64(section.Offset),
    50  			Size:   section.Size,
    51  		})
    52  	}
    53  
    54  	for _, symbol := range symbols {
    55  		if symbol.Sect > 0 {
    56  			section := file.Sections[symbol.Sect-1]
    57  			file.Symbols = append(file.Symbols, &Symbol{
    58  				// symbols in macho files seem to be prefixed with an underscore
    59  				Name: strings.TrimPrefix(symbol.Name, "_"),
    60  				// MachO symbol value is virtual address of the symbol, convert it to offset into the section.
    61  				Addr: symbol.Value - section.Addr,
    62  				// MachO symbols don't have size information.
    63  				Size:    0,
    64  				Section: section,
    65  			})
    66  		}
    67  	}
    68  
    69  	return file, nil
    70  }
    71  
    72  func dumpMachoSymbols(r io.ReaderAt) error {
    73  	machoFile, err := macho.NewFile(r)
    74  	if err != nil {
    75  		return cantParseError{err}
    76  	}
    77  
    78  	fmt.Println("&macho.File{")
    79  
    80  	fmt.Println("\tSections: []*macho.Section{")
    81  	for _, section := range machoFile.Sections {
    82  		fmt.Printf("\t\t&macho.Section{SectionHeader: %#v},\n", section.SectionHeader)
    83  	}
    84  	fmt.Println("\t},")
    85  
    86  	fmt.Println("\tSymtab: &macho.Symtab{")
    87  	fmt.Println("\t\tSyms: []macho.Symbol{")
    88  	for _, symbol := range machoFile.Symtab.Syms {
    89  		fmt.Printf("\t\t\t%#v,\n", symbol)
    90  	}
    91  	fmt.Println("\t\t},")
    92  	fmt.Println("\t},")
    93  
    94  	fmt.Println("}")
    95  
    96  	return nil
    97  }