329 lines
13 KiB
Python
Executable File
329 lines
13 KiB
Python
Executable File
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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Module ELF contains ELF, Symbol, Section classes for manipulation over ELF files.
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It can parse, and change ELF file. This version works only with vmlinux and doesn't properly work with ELF that contains
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UND symbols
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"""
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import subprocess
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import re
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import os
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import struct
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from Utils import Utils
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from collections import OrderedDict
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from binascii import unhexlify
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__author__ = "Vadym Stupakov"
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__copyright__ = "Copyright (c) 2017 Samsung Electronics"
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__credits__ = ["Vadym Stupakov"]
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__version__ = "1.0"
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__maintainer__ = "Vadym Stupakov"
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__email__ = "v.stupakov@samsung.com"
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__status__ = "Production"
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class Symbol:
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def __init__(self, name=str(), sym_type=str(), bind=str(), visibility=str(), addr=int(), size=int(), ndx=str()):
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self.utils = Utils()
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self.name = str(name)
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self.type = str(sym_type)
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self.bind = str(bind)
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self.ndx = str(ndx)
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self.visibility = str(visibility)
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self.addr = self.utils.to_int(addr)
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self.size = self.utils.to_int(size)
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def __str__(self):
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return "name: '{}', type: '{}', bind: '{}', ndx: '{}', visibility: '{}', address: '{}', size: '{}'".format(
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self.name, self.type, self.bind, self.ndx, self.visibility, hex(self.addr), hex(self.size)
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)
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def __lt__(self, other):
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return self.addr <= other.addr
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class Section:
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def __init__(self, name=str(), sec_type=str(), addr=int(), offset=int(), size=int()):
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self.utils = Utils()
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self.name = str(name)
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self.type = str(sec_type)
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self.addr = self.utils.to_int(addr)
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self.offset = self.utils.to_int(offset)
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self.size = self.utils.to_int(size)
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def __str__(self):
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return "name: '{}', type: '{}', address: '{}', offset: '{}', size: '{}'".format(
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self.name, self.type, hex(self.addr), hex(self.offset), hex(self.size)
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)
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def __lt__(self, other):
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return self.addr <= other.addr
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class ELF:
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"""
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Utils for manipulating over ELF
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"""
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def __init__(self, elf_file, readelf_path="readelf"):
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self.__elf_file = elf_file
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self.utils = Utils()
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self.__readelf_path = readelf_path
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self.__sections = OrderedDict()
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self.__symbols = OrderedDict()
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self.__relocs = list()
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self.__re_hexdecimal = "\s*[0-9A-Fa-f]+\s*"
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self.__re_sec_name = "\s*[._a-zA-Z]+\s*"
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self.__re_type = "\s*[A-Z]+\s*"
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def __readelf_raw(self, options):
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"""
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Execute readelf with options and print raw output
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:param options readelf options: ["opt1", "opt2", "opt3", ..., "optN"]
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:returns raw output
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"""
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ret = subprocess.Popen(args=[self.__readelf_path] + options,
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE)
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stdout, stderr = ret.communicate()
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if "readelf: Error: the PHDR segment is not covered by a LOAD segment" in stderr.decode("utf-8").strip():
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ret.returncode = 0
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if ret.returncode != 0:
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raise ChildProcessError(stderr.decode("utf-8") + stdout.decode("utf-8"))
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return stdout.decode("utf-8")
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def set_elf_file(self, elf_file):
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if os.path.abspath(self.__elf_file) != os.path.abspath(elf_file):
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self.__elf_file = os.path.abspath(elf_file)
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self.__sections.clear()
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self.__symbols.clear()
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self.__relocs.clear()
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def get_elf_file(self):
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return os.path.abspath(self.__elf_file)
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def get_sections(self):
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""""
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Execute -> parse -> transform to dict() readelf output
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:returns dict: {sec_addr : Section()}
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"""
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if len(self.__sections) == 0:
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sec_header = self.__readelf_raw(["-SW", self.__elf_file]).strip()
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secs = re.compile("^.*\[.*\](" + self.__re_sec_name + self.__re_type + self.__re_hexdecimal +
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self.__re_hexdecimal + self.__re_hexdecimal + ")", re.MULTILINE)
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found = secs.findall(sec_header)
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for line in found:
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line = line.split()
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if len(line) == 5:
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self.__sections[int(line[2], 16)] = Section(name=line[0], sec_type=line[1], addr=int(line[2], 16),
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offset=int(line[3], 16), size=int(line[4], 16))
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self.__sections = OrderedDict(sorted(self.__sections.items()))
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return self.__sections
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def get_symbols(self):
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""""
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Execute -> parse -> transform to dict() readelf output
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:returns dict: {sym_addr : Symbol()}
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"""
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if len(self.__symbols) == 0:
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sym_tab = self.__readelf_raw(["-sW", self.__elf_file])
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syms = re.compile(r"^.*\d+:\s(.*$)", re.MULTILINE)
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found = syms.findall(sym_tab.strip())
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for line in found:
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line = line.split()
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if len(line) == 7:
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size = line[1]
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# This needs, because readelf prints sizes in hex if size is large
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if size[:2].upper() == "0X":
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size = int(size, 16)
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else:
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size = int(size, 10)
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"""
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Do not include additional compiler information with name $d and $x
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$d and $x is mapping symbols, their virtual addresses may coincide with virtual addresses
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of the real objects
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"""
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if line[6] not in ("$d", "$x"):
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self.__symbols[int(line[0], 16)] = Symbol(addr=int(line[0], 16), size=size, sym_type=line[2],
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bind=line[3], visibility=line[4], ndx=line[5],
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name=line[6])
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self.__symbols = OrderedDict(sorted(self.__symbols.items()))
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return self.__symbols
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def get_relocs(self, start_addr=None, end_addr=None):
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""""
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:param start_addr: start address :int
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:param end_addr: end address: int
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:returns list: [reloc1, reloc2, reloc3, ..., relocN]
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"""
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if len(self.__relocs) == 0:
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relocs = self.__readelf_raw(["-rW", self.__elf_file])
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rel = re.compile(r"^(" + self.__re_hexdecimal + ")\s*", re.MULTILINE)
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self.__relocs = [self.utils.to_int(el) for el in rel.findall(relocs.strip())]
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if start_addr and end_addr is not None:
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ranged_rela = list()
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for el in self.__relocs:
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if self.utils.to_int(start_addr) <= self.utils.to_int(el) <= self.utils.to_int(end_addr):
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ranged_rela.append(el)
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return ranged_rela
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return self.__relocs
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def get_altinstructions(self, start_addr=None, end_addr=None):
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"""
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:param start_addr: start address :int
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:param end_addr: end address: int
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:returns list: [[alt_inst1_addr, length1], [alt_inst2_addr, length2], ...]
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.altinstructions section contains an array of struct alt_instr.
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As instance, for kernel 4.14 from /arch/arm64/include/asm/alternative.h
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struct alt_instr {
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s32 orig_offset; /* offset to original instruction */
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s32 alt_offset; /* offset to replacement instruction */
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u16 cpufeature; /* cpufeature bit set for replacement */
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u8 orig_len; /* size of original instruction(s) */
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u8 alt_len; /* size of new instruction(s), <= orig_len */
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};
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Later, address of original instruction can be calculated as
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at runtime : &(alt_instr->orig_offset) + alt_instr->orig_offset + kernel offset
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ELF processing : address of .altinstruction section + in section offset of alt_instr structure + value of alt_instr.orig_offset
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details in /arch/arm64/kernel/alternative.c, void __apply_alternatives(void *, bool)
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"""
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# The struct_format should reflect <struct alt_instr> content
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struct_format = '<iiHBB'
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pattern_altinst_section_content = "^ *0x[0-9A-Fa-f]{16} (.*) .*.{16}$"
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pattern_altinstr_section_addr = "^ *(0x[0-9A-Fa-f]{16}).*.*.{16}$"
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ranged_altinst = list()
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__hex_dump = self.__readelf_raw(["--hex-dump=.altinstructions", self.__elf_file])
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if len(__hex_dump) == 0:
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return ranged_altinst
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# .altinstruction section start addr in ELF
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__altinstr_section_addr = int(re.findall(pattern_altinstr_section_addr, __hex_dump, re.MULTILINE)[0], 16)
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# To provide .altinstruction section content using host readelf only
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# some magic with string parcing is needed
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hex_dump_list = re.findall(pattern_altinst_section_content, __hex_dump, re.MULTILINE)
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__hex_dump_str = ''.join(hex_dump_list).replace(" ", "")
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__altinstr_section_bin = unhexlify(__hex_dump_str)
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__struct_size = struct.calcsize(struct_format)
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if (len(__altinstr_section_bin) % __struct_size) != 0:
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return ranged_altinst
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if start_addr and end_addr is not None:
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__i = 0
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while __i < (len(__altinstr_section_bin) - __struct_size):
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__struct_byte = __altinstr_section_bin[__i: __i + __struct_size]
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__struct_value = list(struct.unpack(struct_format, __struct_byte))
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# original instruction addr (going to be replaced) considered as "gap"
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__original_instruction_addr = __struct_value[0] + __altinstr_section_addr + __i
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# derive the target ARM instruction(s) length.
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__target_instruction_len = __struct_value[4]
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if self.utils.to_int(start_addr) <= __original_instruction_addr <= self.utils.to_int(end_addr):
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ranged_altinst.append([__original_instruction_addr, __target_instruction_len])
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__i = __i + __struct_size
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return ranged_altinst
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def get_symbol_by_name(self, sym_names):
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"""
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Get symbol by_name
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:param sym_names: "sym_name" : str or list
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:return: Symbol() or [Symbol()]
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"""
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if isinstance(sym_names, str):
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for addr, symbol_obj in self.get_symbols().items():
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if symbol_obj.name == sym_names:
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return symbol_obj
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elif isinstance(sym_names, list):
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symbols = [self.get_symbol_by_name(sym_name) for sym_name in sym_names]
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return symbols
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else:
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raise ValueError
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return None
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def get_symbol_by_vaddr(self, vaddrs=None):
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"""
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Get symbol by virtual address
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:param vaddrs: vaddr : int or list
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:return: Symbol() or [Symbol()]
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"""
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if isinstance(vaddrs, int):
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if vaddrs in self.get_symbols():
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return self.get_symbols()[vaddrs]
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for addr, symbol_obj in self.get_symbols().items():
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if (addr + symbol_obj.size) >= vaddrs >= addr:
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return symbol_obj
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elif isinstance(vaddrs, list):
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symbol = [self.get_symbol_by_vaddr(vaddr) for vaddr in vaddrs]
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return symbol
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else:
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raise ValueError
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return None
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def get_section_by_name(self, sec_names=None):
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"""
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Get section by_name
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:param sec_names: "sec_name" : str or list
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:return: Section() or [Section()]
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"""
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if isinstance(sec_names, str):
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for addr, section_obj in self.get_sections().items():
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if section_obj.name == sec_names:
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return section_obj
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elif isinstance(sec_names, list):
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sections = [self.get_section_by_name(sec_name) for sec_name in sec_names]
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return sections
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else:
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raise ValueError
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return None
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def get_section_by_vaddr(self, vaddrs=None):
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"""
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Get section by virtual address
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:param vaddrs: vaddr : int or list
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:return: Section() or [Section()]
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"""
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if isinstance(vaddrs, int):
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if vaddrs in self.get_sections():
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return self.get_sections()[vaddrs]
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for addr, section_obj in self.get_sections().items():
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if (addr + section_obj.size) >= vaddrs >= addr:
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return section_obj
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elif isinstance(vaddrs, list):
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sections = [self.get_symbol_by_vaddr(vaddr) for vaddr in vaddrs]
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return sections
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else:
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raise ValueError
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return None
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def vaddr_to_file_offset(self, vaddrs):
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"""
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Transform virtual address to file offset
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:param vaddrs: addr string or int or list
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:returns file offset or list
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"""
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if isinstance(vaddrs, str) or isinstance(vaddrs, int):
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section = self.get_section_by_vaddr(vaddrs)
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return self.utils.to_int(vaddrs, 16) - section.addr + section.offset
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elif isinstance(vaddrs, list):
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return [self.vaddr_to_file_offset(vaddr) for vaddr in vaddrs]
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else:
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raise ValueError
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def read_data_from_vaddr(self, vaddr, size, out_file):
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with open(self.__elf_file, "rb") as elf_fp:
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elf_fp.seek(self.vaddr_to_file_offset(vaddr))
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with open(out_file, "wb") as out_fp:
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out_fp.write(elf_fp.read(size))
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