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212 lines
6.1 KiB
ReStructuredText
212 lines
6.1 KiB
ReStructuredText
drgn
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====
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.. image:: https://img.shields.io/pypi/v/drgn
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:target: https://pypi.org/project/drgn/
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:alt: PyPI
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.. image:: https://github.com/osandov/drgn/workflows/CI/badge.svg
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:target: https://github.com/osandov/drgn/actions
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:alt: CI Status
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.. image:: https://readthedocs.org/projects/drgn/badge/?version=latest
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:target: https://drgn.readthedocs.io/en/latest/?badge=latest
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:alt: Documentation Status
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.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
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:target: https://github.com/psf/black
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.. start-introduction
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drgn (pronounced "dragon") is a debugger with an emphasis on programmability.
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drgn exposes the types and variables in a program for easy, expressive
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scripting in Python. For example, you can debug the Linux kernel:
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.. code-block:: pycon
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>>> from drgn.helpers.linux import list_for_each_entry
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>>> for mod in list_for_each_entry('struct module',
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... prog['modules'].address_of_(),
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... 'list'):
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... if mod.refcnt.counter > 10:
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... print(mod.name)
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...
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(char [56])"snd"
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(char [56])"evdev"
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(char [56])"i915"
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Although other debuggers like `GDB <https://www.gnu.org/software/gdb/>`_ have
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scripting support, drgn aims to make scripting as natural as possible so that
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debugging feels like coding. This makes it well-suited for introspecting the
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complex, inter-connected state in large programs. It is also designed as a
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library that can be used to build debugging and introspection tools; see the
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official `tools <https://github.com/osandov/drgn/tree/main/tools>`_.
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drgn was developed at `Meta <https://opensource.fb.com/>`_ for debugging the
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Linux kernel (as an alternative to the `crash
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<https://crash-utility.github.io/>`_ utility), but it can also debug userspace
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programs written in C. C++ support is in progress.
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.. end-introduction
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Documentation can be found at `drgn.readthedocs.io
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<https://drgn.readthedocs.io>`_.
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.. start-installation
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Installation
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------------
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Package Manager
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^^^^^^^^^^^^^^^
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drgn can be installed using the package manager on some Linux distributions.
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* Fedora >= 32
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.. code-block:: console
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$ sudo dnf install drgn
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* RHEL/CentOS >= 8
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`Enable EPEL <https://docs.fedoraproject.org/en-US/epel/#_quickstart>`_. Then:
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.. code-block:: console
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$ sudo dnf install drgn
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* Arch Linux
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Install the `drgn <https://aur.archlinux.org/packages/drgn/>`_ package from
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the `AUR <https://wiki.archlinux.org/title/Arch_User_Repository>`_.
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pip
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^^^
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If your Linux distribution doesn't package the latest release of drgn, you can
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install it with `pip <https://pip.pypa.io/>`_.
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First, `install pip
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<https://packaging.python.org/guides/installing-using-linux-tools/#installing-pip-setuptools-wheel-with-linux-package-managers>`_.
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Then, run:
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.. code-block:: console
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$ sudo pip3 install drgn
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This will install a binary wheel by default. If you get a build error, then pip
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wasn't able to use the binary wheel. Install the dependencies listed `below
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<#from-source>`_ and try again.
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Note that RHEL/CentOS 6, Debian Stretch, Ubuntu Trusty, and Ubuntu Xenial (and
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older) ship Python versions which are too old. Python 3.6 or newer must be
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installed.
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From Source
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^^^^^^^^^^^
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To get the development version of drgn, you will need to build it from source.
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First, install dependencies:
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* Fedora/RHEL/CentOS
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.. code-block:: console
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$ sudo dnf install autoconf automake elfutils-devel gawk gcc git libtool make pkgconf python3 python3-devel python3-pip python3-setuptools
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Replace ``dnf`` with ``yum`` for RHEL/CentOS < 8.
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* Debian/Ubuntu
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.. code-block:: console
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$ sudo apt-get install autoconf automake gawk gcc git liblzma-dev libelf-dev libdw-dev make pkgconf python3 python3-dev python3-pip python3-setuptools zlib1g-dev
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* Arch Linux
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.. code-block:: console
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$ sudo pacman -S --needed autoconf automake gawk gcc git libelf make pkgconf python python-pip python-setuptools
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Optionally, install `libkdumpfile <https://github.com/ptesarik/libkdumpfile>`_
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if you want support for the `makedumpfile
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<https://github.com/makedumpfile/makedumpfile>`_ compressed kernel core dump
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format. ``libkdumpfile`` is currently only packaged on Fedora and EPEL. For
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other distributions, you must install it manually.
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Then, run:
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.. code-block:: console
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$ git clone https://github.com/osandov/drgn.git
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$ cd drgn
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$ python3 setup.py build
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$ sudo python3 setup.py install
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.. end-installation
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See the `installation documentation
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<https://drgn.readthedocs.io/en/latest/installation.html>`_ for more options.
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Quick Start
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-----------
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.. start-quick-start
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drgn debugs the running kernel by default; run ``sudo drgn``. To debug a
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running program, run ``sudo drgn -p $PID``. To debug a core dump (either a
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kernel vmcore or a userspace core dump), run ``drgn -c $PATH``. Make sure to
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`install debugging symbols
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<https://drgn.readthedocs.io/en/latest/getting_debugging_symbols.html>`_ for
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whatever you are debugging.
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Then, you can access variables in the program with ``prog['name']`` and access
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structure members with ``.``:
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.. code-block:: pycon
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$ sudo drgn
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>>> prog['init_task'].comm
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(char [16])"swapper/0"
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You can use various predefined helpers:
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.. code-block:: pycon
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>>> len(list(bpf_prog_for_each(prog)))
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11
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>>> task = find_task(prog, 115)
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>>> cmdline(task)
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[b'findmnt', b'-p']
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You can get stack traces with ``prog.stack_trace()`` and access parameters or
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local variables with ``stack_trace['name']``:
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.. code-block:: pycon
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>>> trace = prog.stack_trace(task)
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>>> trace[5]
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#5 at 0xffffffff8a5a32d0 (do_sys_poll+0x400/0x578) in do_poll at ./fs/select.c:961:8 (inlined)
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>>> poll_list = trace[5]['list']
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>>> file = fget(task, poll_list.entries[0].fd)
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>>> d_path(file.f_path.address_of_())
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b'/proc/115/mountinfo'
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.. end-quick-start
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See the `user guide <https://drgn.readthedocs.io/en/latest/user_guide.html>`_
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for more details and features.
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License
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-------
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.. start-license
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Copyright (c) Meta Platforms, Inc. and affiliates.
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drgn is licensed under the `GPLv3
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<https://www.gnu.org/licenses/gpl-3.0.en.html>`_ or later.
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.. end-license
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