drgn ==== .. image:: https://img.shields.io/pypi/v/drgn :target: https://pypi.org/project/drgn/ :alt: PyPI .. image:: https://github.com/osandov/drgn/workflows/CI/badge.svg :target: https://github.com/osandov/drgn/actions :alt: CI Status .. image:: https://readthedocs.org/projects/drgn/badge/?version=latest :target: https://drgn.readthedocs.io/en/latest/?badge=latest :alt: Documentation Status .. image:: https://img.shields.io/badge/code%20style-black-000000.svg :target: https://github.com/psf/black .. start-introduction drgn (pronounced "dragon") is a debugger with an emphasis on programmability. drgn exposes the types and variables in a program for easy, expressive scripting in Python. For example, you can debug the Linux kernel: .. code-block:: pycon >>> from drgn.helpers.linux import list_for_each_entry >>> for mod in list_for_each_entry('struct module', ... prog['modules'].address_of_(), ... 'list'): ... if mod.refcnt.counter > 10: ... print(mod.name) ... (char [56])"snd" (char [56])"evdev" (char [56])"i915" Although other debuggers like `GDB `_ have scripting support, drgn aims to make scripting as natural as possible so that debugging feels like coding. This makes it well-suited for introspecting the complex, inter-connected state in large programs. Additionally, drgn is designed as a library that can be used to build debugging and introspection tools; see the official `tools `_. drgn was developed at `Meta `_ for debugging the Linux kernel (as an alternative to the `crash `_ utility), but it can also debug userspace programs written in C. C++ support is in progress. .. end-introduction Documentation can be found at `drgn.readthedocs.io `_. .. start-installation Installation ------------ Package Manager ^^^^^^^^^^^^^^^ drgn can be installed using the package manager on some Linux distributions. .. image:: https://repology.org/badge/vertical-allrepos/drgn.svg :target: https://repology.org/project/drgn/versions :alt: Packaging Status * Fedora >= 32 .. code-block:: console $ sudo dnf install drgn * RHEL/CentOS >= 8 `Enable EPEL `_. Then: .. code-block:: console $ sudo dnf install drgn * Arch Linux Install the `drgn `_ package from the `AUR `_. * Debian >= 12 (Bookworm) .. code-block:: console $ sudo apt install python3-drgn * openSUSE .. code-block:: console $ sudo zypper install python3-drgn * Ubuntu Enable the `michel-slm/kernel-utils PPA `_. Then: .. code-block:: console $ sudo apt install python3-drgn pip ^^^ If your Linux distribution doesn't package the latest release of drgn, you can install it with `pip `_. First, `install pip `_. Then, run: .. code-block:: console $ sudo pip3 install drgn This will install a binary wheel by default. If you get a build error, then pip wasn't able to use the binary wheel. Install the dependencies listed `below <#from-source>`_ and try again. Note that RHEL/CentOS 6, Debian Stretch, Ubuntu Trusty, and Ubuntu Xenial (and older) ship Python versions which are too old. Python 3.6 or newer must be installed. From Source ^^^^^^^^^^^ To get the development version of drgn, you will need to build it from source. First, install dependencies: * Fedora .. code-block:: console $ sudo dnf install autoconf automake elfutils-devel gcc git libkdumpfile-devel libtool make pkgconf python3 python3-devel python3-pip python3-setuptools * RHEL/CentOS .. code-block:: console $ sudo dnf install autoconf automake elfutils-devel gcc git libtool make pkgconf python3 python3-devel python3-pip python3-setuptools Optionally, install ``libkdumpfile-devel`` from EPEL on RHEL/CentOS >= 8 or install `libkdumpfile `_ from source if you want support for the makedumpfile format. Replace ``dnf`` with ``yum`` for RHEL/CentOS < 8. * Debian/Ubuntu .. code-block:: console $ sudo apt-get install autoconf automake gcc git liblzma-dev libelf-dev libdw-dev libtool make pkgconf python3 python3-dev python3-pip python3-setuptools zlib1g-dev Optionally, install libkdumpfile from source if you want support for the makedumpfile format. * Arch Linux .. code-block:: console $ sudo pacman -S --needed autoconf automake gcc git libelf libtool make pkgconf python python-pip python-setuptools Optionally, install `libkdumpfile `__ from the AUR or from source if you want support for the makedumpfile format. * openSUSE .. code-block:: console $ sudo zypper install autoconf automake gcc git libdw-devel libelf-devel libkdumpfile-devel libtool make pkgconf python3 python3-devel python3-pip python3-setuptools Then, run: .. code-block:: console $ git clone https://github.com/osandov/drgn.git $ cd drgn $ python3 setup.py build $ sudo python3 setup.py install .. end-installation See the `installation documentation `_ for more options. Quick Start ----------- .. start-quick-start drgn debugs the running kernel by default; run ``sudo drgn``. To debug a running program, run ``sudo drgn -p $PID``. To debug a core dump (either a kernel vmcore or a userspace core dump), run ``drgn -c $PATH``. Make sure to `install debugging symbols `_ for whatever you are debugging. Then, you can access variables in the program with ``prog['name']`` and access structure members with ``.``: .. code-block:: pycon $ sudo drgn >>> prog['init_task'].comm (char [16])"swapper/0" You can use various predefined helpers: .. code-block:: pycon >>> len(list(bpf_prog_for_each(prog))) 11 >>> task = find_task(prog, 115) >>> cmdline(task) [b'findmnt', b'-p'] You can get stack traces with ``prog.stack_trace()`` and access parameters or local variables with ``stack_trace['name']``: .. code-block:: pycon >>> trace = prog.stack_trace(task) >>> trace[5] #5 at 0xffffffff8a5a32d0 (do_sys_poll+0x400/0x578) in do_poll at ./fs/select.c:961:8 (inlined) >>> poll_list = trace[5]['list'] >>> file = fget(task, poll_list.entries[0].fd) >>> d_path(file.f_path.address_of_()) b'/proc/115/mountinfo' .. end-quick-start See the `user guide `_ for more details and features. License ------- .. start-license Copyright (c) Meta Platforms, Inc. and affiliates. drgn is licensed under the `LGPLv2.1 `_ or later. .. end-license