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:
>>> 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 )"snd" (char )"evdev" (char )"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. It is also designed as a library that can be used to build debugging and introspection tools; see the official tools.
Documentation can be found at drgn.readthedocs.io.
drgn can be installed using the package manager on some Linux distributions.
Fedora >= 32
$ sudo dnf install drgn
RHEL/CentOS >= 8
Enable EPEL. Then:
$ sudo dnf install drgn
If your Linux distribution doesn't package the latest release of drgn, you can install it with pip.
First, install pip. Then, run:
$ 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 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.
To get the development version of drgn, you will need to build it from source. First, install dependencies:
$ sudo dnf install autoconf automake elfutils-devel gcc git libtool make pkgconf python3 python3-devel python3-pip python3-setuptools
yumfor RHEL/CentOS < 8.
$ 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
$ sudo pacman -S --needed autoconf automake gcc git libelf libtool make pkgconf python python-pip python-setuptools
Optionally, install libkdumpfile
if you want support for the makedumpfile compressed kernel core dump
libkdumpfile is currently only packaged on Fedora and EPEL. For
other distributions, you must install it manually.
$ git clone https://github.com/osandov/drgn.git $ cd drgn $ python3 setup.py build $ sudo python3 setup.py install
See the installation documentation for more options.
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
$ sudo drgn >>> prog['init_task'].comm (char )"swapper/0"
You can use various predefined helpers:
>>> 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
>>> trace = prog.stack_trace(task) >>> trace #5 at 0xffffffff8a5a32d0 (do_sys_poll+0x400/0x578) in do_poll at ./fs/select.c:961:8 (inlined) >>> poll_list = trace['list'] >>> file = fget(task, poll_list.entries.fd) >>> d_path(file.f_path.address_of_()) b'/proc/115/mountinfo'
See the user guide for more details and features.
Copyright (c) Meta Platforms, Inc. and affiliates.
drgn is licensed under the GPLv3 or later.