152 lines
4.5 KiB
Python
152 lines
4.5 KiB
Python
import os, struct
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class NotELFFileError(Exception):
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pass
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class ELFFile:
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EI_NIDENT = 16
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EI_CLASS = 4
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EI_DATA = 5
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EI_VERSION = 6
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EI_OSABI = 7
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EI_ABIVERSION = 8
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E_MACHINE = 0x12
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# possible values for EI_CLASS
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ELFCLASSNONE = 0
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ELFCLASS32 = 1
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ELFCLASS64 = 2
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# possible value for EI_VERSION
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EV_CURRENT = 1
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# possible values for EI_DATA
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ELFDATANONE = 0
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ELFDATA2LSB = 1
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ELFDATA2MSB = 2
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PT_INTERP = 3
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def my_assert(self, expectation, result):
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if not expectation == result:
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#print "'%x','%x' %s" % (ord(expectation), ord(result), self.name)
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raise NotELFFileError("%s is not an ELF" % self.name)
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def __init__(self, name, bits = 0):
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self.name = name
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self.bits = bits
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self.objdump_output = {}
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def open(self):
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if not os.path.isfile(self.name):
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raise NotELFFileError("%s is not a normal file" % self.name)
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self.file = file(self.name, "r")
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# Read 4k which should cover most of the headers we're after
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self.data = self.file.read(4096)
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if len(self.data) < ELFFile.EI_NIDENT + 4:
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raise NotELFFileError("%s is not an ELF" % self.name)
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self.my_assert(self.data[0], chr(0x7f) )
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self.my_assert(self.data[1], 'E')
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self.my_assert(self.data[2], 'L')
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self.my_assert(self.data[3], 'F')
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if self.bits == 0:
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if self.data[ELFFile.EI_CLASS] == chr(ELFFile.ELFCLASS32):
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self.bits = 32
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elif self.data[ELFFile.EI_CLASS] == chr(ELFFile.ELFCLASS64):
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self.bits = 64
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else:
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# Not 32-bit or 64.. lets assert
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raise NotELFFileError("ELF but not 32 or 64 bit.")
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elif self.bits == 32:
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self.my_assert(self.data[ELFFile.EI_CLASS], chr(ELFFile.ELFCLASS32))
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elif self.bits == 64:
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self.my_assert(self.data[ELFFile.EI_CLASS], chr(ELFFile.ELFCLASS64))
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else:
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raise NotELFFileError("Must specify unknown, 32 or 64 bit size.")
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self.my_assert(self.data[ELFFile.EI_VERSION], chr(ELFFile.EV_CURRENT) )
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self.sex = self.data[ELFFile.EI_DATA]
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if self.sex == chr(ELFFile.ELFDATANONE):
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raise NotELFFileError("self.sex == ELFDATANONE")
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elif self.sex == chr(ELFFile.ELFDATA2LSB):
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self.sex = "<"
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elif self.sex == chr(ELFFile.ELFDATA2MSB):
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self.sex = ">"
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else:
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raise NotELFFileError("Unknown self.sex")
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def osAbi(self):
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return ord(self.data[ELFFile.EI_OSABI])
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def abiVersion(self):
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return ord(self.data[ELFFile.EI_ABIVERSION])
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def abiSize(self):
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return self.bits
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def isLittleEndian(self):
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return self.sex == "<"
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def isBigEndian(self):
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return self.sex == ">"
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def getShort(self, offset):
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return struct.unpack_from(self.sex+"H", self.data, offset)[0]
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def getWord(self, offset):
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return struct.unpack_from(self.sex+"i", self.data, offset)[0]
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def isDynamic(self):
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"""
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Return True if there is a .interp segment (therefore dynamically
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linked), otherwise False (statically linked).
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"""
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offset = self.getWord(self.bits == 32 and 0x1C or 0x20)
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size = self.getShort(self.bits == 32 and 0x2A or 0x36)
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count = self.getShort(self.bits == 32 and 0x2C or 0x38)
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for i in range(0, count):
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p_type = self.getWord(offset + i * size)
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if p_type == ELFFile.PT_INTERP:
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return True
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return False
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def machine(self):
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"""
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We know the sex stored in self.sex and we
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know the position
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"""
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return self.getShort(ELFFile.E_MACHINE)
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def run_objdump(self, cmd, d):
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import bb.process
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import sys
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if cmd in self.objdump_output:
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return self.objdump_output[cmd]
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objdump = d.getVar('OBJDUMP', True)
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env = os.environ.copy()
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env["LC_ALL"] = "C"
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env["PATH"] = d.getVar('PATH', True)
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try:
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bb.note("%s %s %s" % (objdump, cmd, self.name))
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self.objdump_output[cmd] = bb.process.run([objdump, cmd, self.name], env=env, shell=False)[0]
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return self.objdump_output[cmd]
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except Exception as e:
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bb.note("%s %s %s failed: %s" % (objdump, cmd, self.name, e))
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return ""
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if __name__ == "__main__":
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import sys
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elf = ELFFile(sys.argv[1])
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elf.open()
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print(elf.isDynamic())
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