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118
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1 import struct
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126
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2 import collections
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118
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3
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4 class ElfFile:
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5 def __init__(self, f):
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6 self.f = f
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7 self.parse()
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8 def parse(self):
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9 self.parseHeader()
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10 @property
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11 def ElfClass(self):
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12 return classes[self.ei_class]
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13 def parseHeader(self):
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14 # Parse identifier
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15 e_ident = self.f.read(16)
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16 ELFMAGIC = bytes([0x7f]) + b'ELF'
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17 assert e_ident[0:4] == ELFMAGIC
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18 self.ei_class = e_ident[4]
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126
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19 # Change the class of this object in some strange way:
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20 self.__class__ = classes[self.ei_class]
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21 print('ELF class: ', self.ElfClass)
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22 assert self.ei_class in classes.keys()
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23 self.ei_data = e_ident[5]
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24 print('ei_data:', self.ei_data)
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25 ei_version = e_ident[6]
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26 assert ei_version == 1
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27
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28 # rest of the ELF header:
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29 e_type = self.readHalf()
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30 e_machine = self.readHalf()
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31 e_version = self.readWord()
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32 e_entry = self.readAddr()
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126
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33 self.e_phoff = self.readOff()
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34 self.e_shoff = self.readOff()
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35 self.e_flags = self.readWord()
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118
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36 e_ehsize = self.readHalf()
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126
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37 self.e_phentsize = self.readHalf()
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38 self.e_phnum = self.readHalf()
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39 self.e_shentsize = self.readHalf()
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40 self.e_shnum = self.readHalf()
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41 self.e_shstrndx = self.readHalf()
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42
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43 assert e_ehsize == self.HEADERSIZE
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44 print('program header size', self.e_phentsize, self.e_phnum)
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45 print('section header size', self.e_shentsize, self.e_shnum)
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46 print('string index:', self.e_shstrndx)
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118
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47 def readFmt(self, fmt):
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48 size = struct.calcsize(fmt)
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49 return struct.unpack(fmt, self.f.read(size))
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50 def readHalf(self):
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51 return self.readFmt('<H')[0]
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52 def readWord(self):
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53 return self.readFmt('<I')[0]
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126
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54 def parsePrograms(self):
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55 # Skip to start of program headers:
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56 self.f.seek(self.e_phoff)
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57 pheaders = []
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58 for i in range(self.e_phnum):
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59 pheaders.append(self.parseProgramHeader())
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60 return pheaders
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61
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62 ProgramHeader = collections.namedtuple('ProgramHeader', ['p_type',
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63 'p_flags', 'p_offset', 'p_vaddr', 'p_paddr', 'p_filesz', 'p_memsz'])
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64
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65 class Elf32File(ElfFile):
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66 HEADERSIZE=52
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67 def readAddr(self):
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68 return self.readFmt('<I')[0]
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69 readOff = readAddr
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70 def parseProgramHeader(self):
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71 p_type = self.readWord()
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72 p_offset = self.readOff()
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73 p_vaddr = self.readAddr()
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74 p_paddr = self.readAddr()
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75 p_filesz = self.readWord()
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76 p_memsz = self.readWord()
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77 p_flags = self.readWord()
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78 p_align = self.readWord()
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79 return ProgramHeader(p_type, p_flags, p_offset, p_vaddr, p_paddr, p_filesz, p_memsz)
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80
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81 class Elf64File(ElfFile):
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82 HEADERSIZE=64
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83 def readAddr(self):
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84 return self.readFmt('<Q')[0]
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85 readOff = readAddr
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86 readXword = readAddr
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87 def parseProgramHeader(self):
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88 p_type = self.readWord()
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89 p_flags = self.readWord()
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90 p_offset = self.readOff()
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91 p_vaddr = self.readAddr()
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92 p_paddr = self.readAddr()
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93 p_filesz = self.readXword()
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94 p_memsz = self.readXword()
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95 p_align = self.readXword()
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96 return ProgramHeader(p_type, p_flags, p_offset, p_vaddr, p_paddr)
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118
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97
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126
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98 classes = {1:Elf32File, 2:Elf64File}
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99
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