pylibdebuginfod

Python bindings for libdebuginfod.

This library provides a Python interface for the functions in the libdebuginfod.so library from elfutils. The debuginfod client/server infrastructure allows automatic distribution of debugging information (ELF symbol tables, DWARF and even source code) for binaries installed on the current system.

The debuginfod server is queried using a SHA-1 hash (the build ID) which is contained in a section .note.gnu.build-id in the stripped binary file.

Prerequisites

The minimum Python version required is 3.5.

The bindings require an installation of libdebuginfod.so and the pyelftools library.

libdebuginfod.so is shipped in the major distributions in the following packages:

• Debian (buster-backports, bullseye, sid): libdebuginfod1
• Fedora/CentOS: elfutils-debuginfod-client
• openSUSE Tumbleweed: elfutils
• Ubuntu (20.10 and later): libdebuginfod1

Alternatively, you can get and compile the source code from the official elfutils Git repository.

Usage

The following examples were run under Debian Buster with the libdebuginfod1, libelf1 and libdw1 packages from buster-backports.

In order to make libdebuginfod.so aware of the servers to query, you can set the DEBUGINFOD_URLS environment variable. For example, to query the Debian server, you can run:

$ export DEBUGINFOD_URLS="https://debuginfod.debian.net"

If the DEBUGINFOD_URLS environment variable is not set, it is temporarily set to the elfutils server (https://debuginfod.elfutils.org/) which federates to all trusted servers (listed on the elfutils website).

The other environment variables listed in the manual page are also respected as they are handled by libdebuginfod.so itself.

You can extract the build ID information using the readelf tool like this:

$ readelf -n /lib/x86_64-linux-gnu/libc-2.28.so

Displaying notes found in: .note.gnu.build-id
  Owner                 Data size	Description
  GNU                  0x00000014	NT_GNU_BUILD_ID (unique build ID bitstring)
    Build ID: 18b9a9a8c523e5cfe5b5d946d605d09242f09798

With the prerequisites in place, you can use the DebugInfoD class as follows:

  >>> from libdebuginfod import DebugInfoD
  >>> session = DebugInfoD()
  >>> session.begin() # optional, is also called from __init__ at the moment.
  >>> fd, path = session.find_debuginfo('18b9a9a8c523e5cfe5b5d946d605d09242f09798')
  >>> print((fd, path))
  (3, b'/home/user/.cache/debuginfod_client/18b9a9a8c523e5cfe5b5d946d605d09242f09798/debuginfo')
  >>> session.end()

In a more pythonic way, DebugInfoD can also be used as a context manager where begin() and end() are called automatically.

  >>> from libdebuginfod import DebugInfoD
  >>> with DebugInfoD() as d:
  ...     fd, path = d.find_debuginfo('18b9a9a8c523e5cfe5b5d946d605d09242f09798')
  ...     print((fd, path))
  ...
  (3, b'/home/user/.cache/debuginfod_client/18b9a9a8c523e5cfe5b5d946d605d09242f09798/debuginfo')

The scripts/debuginfod-find.py script supports three commands (debuginfo, executable and source) and accepts either a build ID or a path to a target file. If the filename matches the pattern [0-9a-f]+, please provide the path (e.g., ./e3) to avoid misinterpretation of the input as a build ID. If the command is source, you need to provide the path or build ID as the first input parameter and an absolute path to the target source file (as present in the DWARF information) as the second input parameter.

Example usage:

$ ./scripts/debuginfod-find.py debuginfo /lib/x86_64-linux-gnu/libc-2.28.so
/home/user/.cache/debuginfod_client/18b9a9a8c523e5cfe5b5d946d605d09242f09798/debuginfo

License(s)

The bindings themselves are released under the MIT license. As the script at scripts/debuginfod-find.py is a reimplementation of the debuginfod-find application from elfutils (which is licensed under the GPLv3+ license), the script is also released under the GPLv3+ license and not included in the packaged release of the bindings.