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# This file is part of PeachPy package and is licensed under the Simplified BSD license.
# See license.rst for the full text of the license.
from enum import IntEnum
class SectionFlags(IntEnum):
# Section contains writable data during process execution
writable = 0x1
# Section occupies memory during process execution
allocate = 0x2
# Section contains executable data machine instructions
executable = 0x4
class SectionType(IntEnum):
# Nil section
null = 0
# Program-specific content
program_bits = 1
# Symbol table
symbol_table = 2
# String table
string_table = 3
# Relocations with explicit addend
relocations_with_addend = 4
# Hash table for symbols used in dynamic linking
symbol_hash_table = 5
# Information for dynamic linking
dynamic_linking_info = 6
# Free-form note
note = 7
# Program-specific zero-initialized content
no_bits = 8
# Relocations without explicit addends
relocations = 9
# Minimal symbol table for dynamic linking
dynamic_symbol_table = 11
class SectionIndex(IntEnum):
absolute = 0xFFF1
common = 0xFFF2
undefined = 0x0000
class Section(object):
def __init__(self, name, type, allocate=False, writable=False, executable=False):
# Section name
self.name = name
# Type of the section content
self._type = SectionType.null
self.type = type # Check the type object in property setter
# Properties of section content
self.flags = 0
if allocate:
self.flags |= SectionFlags.allocate
if writable:
self.flags |= SectionFlags.writable
if executable:
self.flags |= SectionFlags.executable
# Section address alignment. Only powers of 2 are allowed. Value 0 or 1 mean no alignment restrictions.
self._alignment = 1
@property
def type(self):
return self._type
@type.setter
def type(self, type):
if not isinstance(type, SectionType):
raise TypeError("Section type %s is not a SectionType enum" % str(type))
self._type = type
@property
def alignment(self):
return self._alignment
@alignment.setter
def alignment(self, alignment):
from peachpy.util import is_uint32
if not is_uint32(alignment):
raise TypeError("Section alignment %s is not representable as a 32-bit unsigned integer" % str(alignment))
if alignment & (alignment - 1) != 0:
raise ValueError("Section alignment %d is not a power of 2" % alignment)
if alignment == 0:
alignment = 1
self._alignment = alignment
@staticmethod
def get_header_size(abi):
from peachpy.abi import ABI
assert isinstance(abi, ABI)
assert abi.elf_bitness in [32, 64]
return {32: 40, 64: 64}[abi.elf_bitness]
def get_content_size(self, abi):
return 0
def encode_header(self, encoder, name_index_map, section_index_map, offset,
address=None, link_section=None, info=None,
content_size=0, entry_size=0):
import peachpy.encoder
from peachpy.util import is_uint64, is_uint32
assert isinstance(encoder, peachpy.encoder.Encoder)
assert isinstance(name_index_map, dict)
assert section_index_map is None or isinstance(section_index_map, dict)
assert offset is None or is_uint64(offset)
assert address is None or is_uint64(address)
assert link_section is None or isinstance(link_section, Section)
assert info is None or is_uint64(info)
assert is_uint64(content_size)
assert is_uint32(entry_size)
assert encoder.bitness in [32, 64]
if encoder.bitness == 32:
assert offset is None or is_uint32(offset)
assert address is None or is_uint32(address)
assert self.name is None or self.name in name_index_map
assert section_index_map is not None or link_section is None
name_index = name_index_map.get(self.name, 0)
if address is None:
address = 0
if offset is None:
offset = 0
link = 0
if link_section is not None:
link = section_index_map[link_section]
if info is None:
info = 0
return encoder.uint32(name_index) + \
encoder.uint32(self.type) + \
encoder.unsigned_offset(self.flags) + \
encoder.unsigned_offset(address) + \
encoder.unsigned_offset(offset) + \
encoder.unsigned_offset(content_size) + \
encoder.uint32(link) + \
encoder.uint32(info) + \
encoder.unsigned_offset(self.alignment) + \
encoder.unsigned_offset(entry_size)
def encode_content(self, encoder, name_index_map, section_index_map, symbol_index_map):
import peachpy.encoder
assert isinstance(encoder, peachpy.encoder.Encoder)
assert isinstance(name_index_map, dict)
assert section_index_map is None or isinstance(section_index_map, dict)
assert symbol_index_map is None or isinstance(symbol_index_map, dict)
assert encoder.bitness in [32, 64]
return bytearray()
null_section = Section(None, SectionType.null)
class ProgramBitsSection(Section):
def __init__(self, name, allocate=True, writable=False, executable=False):
super(ProgramBitsSection, self).__init__(name, SectionType.program_bits, allocate, writable, executable)
self.content = bytearray()
def get_content_size(self, abi):
return len(self.content)
def encode_header(self, encoder, name_index_map, section_index_map, offset, address=None):
return super(ProgramBitsSection, self).encode_header(encoder, name_index_map, section_index_map, offset,
address=address, content_size=len(self.content))
def encode_content(self, encoder, name_index_map, section_index_map, symbol_index_map):
super(ProgramBitsSection, self).encode_content(encoder, name_index_map, section_index_map, symbol_index_map)
return self.content
class TextSection(ProgramBitsSection):
def __init__(self, name=".text"):
super(TextSection, self).__init__(name, executable=True)
class DataSection(ProgramBitsSection):
def __init__(self, name=".data"):
super(DataSection, self).__init__(name, writable=True)
class ReadOnlyDataSection(ProgramBitsSection):
def __init__(self, name=".rodata"):
super(ReadOnlyDataSection, self).__init__(name)
class StringSection(Section):
def __init__(self, name=".strtab"):
super(StringSection, self).__init__(name, SectionType.string_table)
self._string_index_map = dict()
self.content_size = 0
def add(self, string):
if not string:
return 0
elif string in self._string_index_map:
return self._string_index_map[string]
else:
import codecs
if self.content_size == 0:
self.content_size = 1
string_index = self.content_size
self._string_index_map[string] = string_index
string_bytes = codecs.encode(string, "utf-8")
self.content_size += len(string_bytes) + 1
return string_index
def get_content_size(self, abi):
return self.content_size
def encode_header(self, encoder, name_index_map, section_index_map, offset):
return super(StringSection, self).encode_header(encoder, name_index_map, section_index_map, offset,
content_size=self.content_size)
def encode_content(self, encoder, name_index_map, section_index_map, symbol_index_map):
super(StringSection, self).encode_content(encoder, name_index_map, section_index_map, symbol_index_map)
if self.content_size != 0:
import codecs
bytes = b"\x00"
for string in sorted(self._string_index_map, key=self._string_index_map.get):
bytes += codecs.encode(string, "utf8") + b"\x00"
return bytes
else:
return bytearray()
class SymbolSection(Section):
def __init__(self, name=".symtab", string_table=None):
super(SymbolSection, self).__init__(name, SectionType.symbol_table)
self._symbols_set = set()
self._local_symbols = list()
self._nonlocal_symbols = list()
self._string_table = string_table
@property
def symbol_index_map(self):
symbol_index_map = {symbol: index for index, symbol in enumerate(self._local_symbols)}
local_symbols_count = len(self._local_symbols)
symbol_index_map.update(
{symbol: local_symbols_count + index for index, symbol in enumerate(self._nonlocal_symbols)})
return symbol_index_map
def add(self, symbol):
from peachpy.formats.elf.symbol import Symbol, SymbolBinding
assert isinstance(symbol, Symbol)
if symbol in self._symbols_set:
raise ValueError("Symbol %s is already present in the section %s" % (str(symbol), self.name))
self._symbols_set.add(symbol)
if symbol.binding == SymbolBinding.local:
self._local_symbols.append(symbol)
else:
self._nonlocal_symbols.append(symbol)
def get_content_size(self, abi):
from peachpy.formats.elf.symbol import Symbol
from peachpy.abi import ABI
assert isinstance(abi, ABI)
assert abi.elf_bitness in [32, 64]
entry_size = Symbol.get_entry_size(abi)
return entry_size * (len(self._local_symbols) + len(self._nonlocal_symbols))
def encode_header(self, encoder, name_index_map, section_index_map, offset):
import peachpy.encoder
assert isinstance(encoder, peachpy.encoder.Encoder)
assert encoder.bitness in [32, 64]
entry_size = {32: 16, 64: 24}[encoder.bitness]
symbols_count = len(self._local_symbols) + len(self._nonlocal_symbols)
return super(SymbolSection, self).encode_header(encoder, name_index_map, section_index_map, offset,
link_section=self._string_table,
info=len(self._local_symbols),
content_size=symbols_count * entry_size,
entry_size=entry_size)
def encode_content(self, encoder, name_index_map, section_index_map, symbol_index_map):
super(SymbolSection, self).encode_content(encoder, name_index_map, section_index_map, symbol_index_map)
# Local symbols must be encoded before non-local symbols. Thus, need to separate the two classes
content = bytearray()
# Step 1: encode local symbols
for symbol in self._local_symbols:
content += symbol.encode(encoder, name_index_map, section_index_map)
# Step 2: encode non-local symbols
for symbol in self._nonlocal_symbols:
content += symbol.encode(encoder, name_index_map, section_index_map)
return content
class RelocationsWithAddendSection(Section):
def __init__(self, reference_section, symbol_table):
super(RelocationsWithAddendSection, self).__init__(".rela" + reference_section.name,
SectionType.relocations_with_addend)
self.reference_section = reference_section
self.symbol_table = symbol_table
self.relocations = list()
def add(self, relocation):
from peachpy.formats.elf.symbol import RelocationWithAddend
assert isinstance(relocation, RelocationWithAddend)
self.relocations.append(relocation)
def get_content_size(self, abi):
from peachpy.abi import ABI
assert isinstance(abi, ABI)
assert abi.elf_bitness in [32, 64]
entry_size = {32: 12, 64: 24}[abi.elf_bitness]
return entry_size * len(self.relocations)
def encode_header(self, encoder, name_index_map, section_index_map, offset):
import peachpy.encoder
assert isinstance(encoder, peachpy.encoder.Encoder)
assert encoder.bitness in [32, 64]
entry_size = {32: 16, 64: 24}[encoder.bitness]
relocations_count = len(self.relocations)
reference_section_index = section_index_map[self.reference_section]
return super(RelocationsWithAddendSection, self).\
encode_header(encoder, name_index_map, section_index_map, offset,
link_section=self.symbol_table,
info=reference_section_index,
content_size=relocations_count * entry_size,
entry_size=entry_size)
def encode_content(self, encoder, name_index_map, section_index_map, symbol_index_map):
super(RelocationsWithAddendSection, self).\
encode_content(encoder, name_index_map, section_index_map, symbol_index_map)
content = bytearray()
for relocation in self.relocations:
content += relocation.encode(encoder, symbol_index_map)
return content
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