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# -------------------------------------------------------------------------------
# elftools: ehabi/ehabiinfo.py
#
# Decoder for ARM exception handler bytecode.
#
# LeadroyaL (leadroyal@qq.com)
# This code is in the public domain
# -------------------------------------------------------------------------------
from ..common.utils import struct_parse
from .decoder import EHABIBytecodeDecoder
from .constants import EHABI_INDEX_ENTRY_SIZE
from .structs import EHABIStructs
class EHABIInfo(object):
""" ARM exception handler abi information class.
Parameters:
arm_idx_section:
elf.sections.Section object, section which type is SHT_ARM_EXIDX.
little_endian:
bool, endianness of elf file.
"""
def __init__(self, arm_idx_section, little_endian):
self._arm_idx_section = arm_idx_section
self._struct = EHABIStructs(little_endian)
self._num_entry = None
def section_name(self):
return self._arm_idx_section.name
def section_offset(self):
return self._arm_idx_section['sh_offset']
def num_entry(self):
""" Number of exception handler entry in the section.
"""
if self._num_entry is None:
self._num_entry = self._arm_idx_section['sh_size'] // EHABI_INDEX_ENTRY_SIZE
return self._num_entry
def get_entry(self, n):
""" Get the exception handler entry at index #n. (EHABIEntry object or a subclass)
"""
if n >= self.num_entry():
raise IndexError('Invalid entry %d/%d' % (n, self._num_entry))
eh_index_entry_offset = self.section_offset() + n * EHABI_INDEX_ENTRY_SIZE
eh_index_data = struct_parse(self._struct.EH_index_struct, self._arm_idx_section.stream, eh_index_entry_offset)
word0, word1 = eh_index_data['word0'], eh_index_data['word1']
if word0 & 0x80000000 != 0:
return CorruptEHABIEntry('Corrupt ARM exception handler table entry: %x' % n)
function_offset = arm_expand_prel31(word0, self.section_offset() + n * EHABI_INDEX_ENTRY_SIZE)
if word1 == 1:
# 0x1 means cannot unwind
return CannotUnwindEHABIEntry(function_offset)
elif word1 & 0x80000000 == 0:
# highest bit is zero, point to .ARM.extab data
eh_table_offset = arm_expand_prel31(word1, self.section_offset() + n * EHABI_INDEX_ENTRY_SIZE + 4)
eh_index_data = struct_parse(self._struct.EH_table_struct, self._arm_idx_section.stream, eh_table_offset)
word0 = eh_index_data['word0']
if word0 & 0x80000000 == 0:
# highest bit is one, generic model
return GenericEHABIEntry(function_offset, arm_expand_prel31(word0, eh_table_offset))
else:
# highest bit is one, arm compact model
# highest half must be 0b1000 for compact model
if word0 & 0x70000000 != 0:
return CorruptEHABIEntry('Corrupt ARM compact model table entry: %x' % n)
per_index = (word0 >> 24) & 0x7f
if per_index == 0:
# arm compact model 0
opcode = [(word0 & 0xFF0000) >> 16, (word0 & 0xFF00) >> 8, word0 & 0xFF]
return EHABIEntry(function_offset, per_index, opcode)
elif per_index == 1 or per_index == 2:
# arm compact model 1/2
more_word = (word0 >> 16) & 0xff
opcode = [(word0 >> 8) & 0xff, (word0 >> 0) & 0xff]
self._arm_idx_section.stream.seek(eh_table_offset + 4)
for i in range(more_word):
r = struct_parse(self._struct.EH_table_struct, self._arm_idx_section.stream)['word0']
opcode.append((r >> 24) & 0xFF)
opcode.append((r >> 16) & 0xFF)
opcode.append((r >> 8) & 0xFF)
opcode.append((r >> 0) & 0xFF)
return EHABIEntry(function_offset, per_index, opcode, eh_table_offset=eh_table_offset)
else:
return CorruptEHABIEntry('Unknown ARM compact model %d at table entry: %x' % (per_index, n))
else:
# highest bit is one, compact model must be 0
if word1 & 0x7f000000 != 0:
return CorruptEHABIEntry('Corrupt ARM compact model table entry: %x' % n)
opcode = [(word1 & 0xFF0000) >> 16, (word1 & 0xFF00) >> 8, word1 & 0xFF]
return EHABIEntry(function_offset, 0, opcode)
class EHABIEntry(object):
""" Exception handler abi entry.
Accessible attributes:
function_offset:
Integer.
None if corrupt. (Reference: CorruptEHABIEntry)
personality:
Integer.
None if corrupt or unwindable. (Reference: CorruptEHABIEntry, CannotUnwindEHABIEntry)
0/1/2 for ARM personality compact format.
Others for generic personality.
bytecode_array:
Integer array.
None if corrupt or unwindable or generic personality.
(Reference: CorruptEHABIEntry, CannotUnwindEHABIEntry, GenericEHABIEntry)
eh_table_offset:
Integer.
Only entries who point to .ARM.extab contains this field, otherwise return None.
unwindable:
bool. Whether this function is unwindable.
corrupt:
bool. Whether this entry is corrupt.
"""
def __init__(self,
function_offset,
personality,
bytecode_array,
eh_table_offset=None,
unwindable=True,
corrupt=False):
self.function_offset = function_offset
self.personality = personality
self.bytecode_array = bytecode_array
self.eh_table_offset = eh_table_offset
self.unwindable = unwindable
self.corrupt = corrupt
def mnmemonic_array(self):
if self.bytecode_array:
return EHABIBytecodeDecoder(self.bytecode_array).mnemonic_array
else:
return None
def __repr__(self):
return "<EHABIEntry function_offset=0x%x, personality=%d, %sbytecode=%s>" % (
self.function_offset,
self.personality,
"eh_table_offset=0x%x, " % self.eh_table_offset if self.eh_table_offset else "",
self.bytecode_array)
class CorruptEHABIEntry(EHABIEntry):
""" This entry is corrupt. Attribute #corrupt will be True.
"""
def __init__(self, reason):
super(CorruptEHABIEntry, self).__init__(function_offset=None, personality=None, bytecode_array=None,
corrupt=True)
self.reason = reason
def __repr__(self):
return "<CorruptEHABIEntry reason=%s>" % self.reason
class CannotUnwindEHABIEntry(EHABIEntry):
""" This function cannot be unwind. Attribute #unwindable will be False.
"""
def __init__(self, function_offset):
super(CannotUnwindEHABIEntry, self).__init__(function_offset, personality=None, bytecode_array=None,
unwindable=False)
def __repr__(self):
return "<CannotUnwindEHABIEntry function_offset=0x%x>" % self.function_offset
class GenericEHABIEntry(EHABIEntry):
""" This entry is generic model rather than ARM compact model.Attribute #bytecode_array will be None.
"""
def __init__(self, function_offset, personality):
super(GenericEHABIEntry, self).__init__(function_offset, personality, bytecode_array=None)
def __repr__(self):
return "<GenericEHABIEntry function_offset=0x%x, personality=0x%x>" % (self.function_offset, self.personality)
def arm_expand_prel31(address, place):
"""
address: uint32
place: uint32
return: uint64
"""
location = address & 0x7fffffff
if location & 0x04000000:
location |= 0xffffffff80000000
return location + place & 0xffffffffffffffff
|
