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pyelftools

repository·main·Indexed 25 days ago

https://github.com/eliben/pyelftools

A pure-Python library for parsing and analyzing ELF (Executable and Linkable Format) files and DWARF debugging information. It provides a high-level API for interacting with ELF sections, segments, and symbol tables, as well as a low-level API for binary stream parsing. The library includes a specialized fork of the construct library for declarative binary data parsing and building.

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What's inside pyelftools

  2. Understand the API levels in pyelftools

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    The library provides two distinct API levels:

    1. High-level API (Recommended): Most of the library is designed around this level. It encapsulates complex parsing details into Python classes with intuitive attributes and behaviors. This is the primary way users should interact with ELF and DWARF data.

    2. Low-level API: This level directly exposes the parsed contents of the binary streams. It is primarily used for defining how headers and structures are parsed.

      • ELF structures are defined in elftools/elf/structs.py.
      • DWARF structures are defined in elftools/dwarf/structs.py.
      • Warning: The low-level API should be used with caution as it requires deep knowledge of the ELF/DWARF standards.

  3. Access ELF sections and segments

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    ELF Sections

    Sections are the main informational units of an ELF file. ELFFile provides methods to count, index, and iterate over sections.

    All section objects implement the Section interface (defined in elftools/elf/sections.py), which allows:

    • Dictionary-like access to the section header.
    • Accessing section data as a buffer.

    Specialized section classes provide additional functionality for specific section types:

    • SymbolTableSection (in elftools/elf/sections.py): For interacting with symbol tables.
    • StringTableSection (in elftools/elf/sections.py): For string tables.
    • RelocationSection (in elftools/elf/relocation.py): For relocation information.

    ELF Segments

    Segments are represented by the Segment class (defined in elftools/elf/segments.py). Use the methods provided by ELFFile to count and enumerate segments. Some well-known segments have specialized classes in the same module providing more information.

  5. Use pyelftools without installation

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    Since pyelftools has no external dependencies, you can use it without installing it by cloning the Git repository and locally adjusting your PYTHONPATH to include the repository directory.

  7. Run pyelftools examples

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    After installing pyelftools, you can run the included examples from any location by executing the example script with the --test flag and providing an ELF filename as an argument.

    > python <path_to_pyelftools>/examples/<example_name> --test <elf_filename>

  9. Run readelf comparison tests

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    To verify that pyelftools correctly clones the functionality of GNU binutils, you can run the readelf comparison tests. This suite runs the scripts/readelf.py script on various files and compares the output against the system's installed readelf utility.

    Note: Failures may occur due to minor output differences between different versions of readelf or different system architectures. You can check the READELF_PATH variable in test/run_readelf_tests.py to see which binutils version is being used for comparison.

  11. Overview of construct in pyelftools

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    The construct library included in pyelftools is a Python library designed for the declarative parsing and building of binary data. This specific version is a fork of construct 2, modified to support Python 3 and include various bug fixes. Note that this version is maintained separately from the modern, upstream construct project to avoid breaking changes in pyelftools caused by the upstream project's API evolutions.

  12. Access DWARF debugging information

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    The DWARFInfo class (in elftools/dwarf/dwarfinfo.py) is the main entry point for DWARF data. While it can be used independently to parse DWARF data from memory or files, the easiest way to obtain it is through an ELFFile instance.

    To extract DWARF information from an ELF file:

    1. Use ELFFile.has_dwarf_info() to check if debugging information is present.
    2. If true, call ELFFile.get_dwarf_info() to receive a ready-to-use DWARFInfo object. ELFFile handles the necessary bookkeeping, such as relocation of DWARF sections.