96 lines
3.4 KiB
Python
96 lines
3.4 KiB
Python
#-------------------------------------------------------------------------------
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# elftools: dwarf/dwarf_utils.py
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#
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# Minor, shared DWARF helpers
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#
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# Eli Bendersky (eliben@gmail.com)
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# This code is in the public domain
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#-------------------------------------------------------------------------------
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from __future__ import annotations
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import os
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import binascii
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from typing import IO, TYPE_CHECKING, Any
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from ..construct.macros import Array
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from ..common.exceptions import DWARFError
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from ..common.utils import preserve_stream_pos, struct_parse
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if TYPE_CHECKING:
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from collections.abc import Iterator
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from ..construct import Struct
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from .compileunit import CompileUnit
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from .structs import DWARFStructs
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from .typeunit import TypeUnit
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def _get_base_offset(cu: CompileUnit | TypeUnit, base_attribute_name: str) -> int:
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"""Retrieves a required, base offset-type atribute
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from the top DIE in the CU. Applies to several indirectly
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encoded objects - range lists, location lists, strings, addresses.
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"""
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cu_top_die = cu.get_top_DIE()
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if base_attribute_name not in cu_top_die.attributes:
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raise DWARFError("The CU at offset 0x%x needs %s" % (cu.cu_offset, base_attribute_name))
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return cu_top_die.attributes[base_attribute_name].value
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def _resolve_via_offset_table(
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stream: IO[bytes],
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cu: CompileUnit | TypeUnit,
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index: int,
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base_attribute_name: str,
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) -> int:
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"""Given an index in the offset table and directions where to find it,
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retrieves an offset. Works for loclists, rnglists.
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The DWARF offset bitness of the CU block in the section matches that
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of the CU record in dwarf_info. See DWARFv5 standard, section 7.4.
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This is used for translating DW_FORM_loclistx, DW_FORM_rnglistx
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via the offset table in the respective section.
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"""
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base_offset = _get_base_offset(cu, base_attribute_name)
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# That's offset (within the rnglists/loclists/str_offsets section) of
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# the offset table for this CU's block in that section, which in turn is indexed by the index.
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offset_size = 4 if cu.structs.dwarf_format == 32 else 8
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with preserve_stream_pos(stream):
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return base_offset + struct_parse(cu.structs.the_Dwarf_offset, stream, base_offset + index*offset_size)
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def _iter_CUs_in_section(
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stream: IO[bytes],
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structs: DWARFStructs,
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parser: Struct,
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) -> Iterator[Any]:
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"""Iterates through the list of CU sections in loclists or rangelists. Almost identical structures there.
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get_parser is a lambda that takes structs, returns the parser
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"""
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stream.seek(0, os.SEEK_END)
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endpos = stream.tell()
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stream.seek(0, os.SEEK_SET)
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offset = 0
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while offset < endpos:
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header = struct_parse(parser, stream, offset)
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if header.offset_count > 0:
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offset_parser = structs.Dwarf_uint64 if header.is64 else structs.Dwarf_uint32
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header['offsets'] = struct_parse(Array(header.offset_count, offset_parser('')), stream)
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else:
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header['offsets'] = False
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yield header
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offset = header.offset_after_length + header.unit_length
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def _file_crc32(file: IO[bytes]) -> int:
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""" Provided a readable binary stream, reads the stream to the end
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and computes the CRC32 checksum of its contents,
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with the initial value of 0.
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"""
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d = file.read(4096)
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checksum = 0
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while d:
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checksum = binascii.crc32(d, checksum)
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d = file.read(4096)
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return checksum
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