drgn (pronounced "dragon") is a debugger-as-a-library. In contrast to existing debuggers like GDB which focus on breakpoint-based debugging, drgn excels in live introspection. 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 [56])"snd" (char [56])"evdev" (char [56])"i915"

drgn was developed 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 planned.

Documentation can be found at drgn.readthedocs.io.

Install the following dependencies:

• Python 3.6 or newer
• elfutils development libraries (libelf and libdw)
• GNU autotools (autoconf, automake, and libtool) and pkgconf

Then, run:

$ 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 details.

To debug the running kernel, run sudo drgn -k. 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. The program must have debugging symbols available.

Then, you can access variables in the program with prog['name'], access structure members with ., use various predefined helpers, and more:

$ sudo drgn -k >>> prog['init_task'].comm (char [16])"swapper/0" >>> d_path(fget(find_task(prog, 1), 0).f_path.address_of_()) b'/dev/null' >>> max(task.stime for task in for_each_task(prog)) (u64)4192109975952 >>> sum(disk.gendisk.part0.nr_sects for disk in for_each_disk(prog)) (sector_t)999705952

See the user guide for more information.

Copyright 2018-2019 Omar Sandoval

drgn is licensed under the GPLv3 or later.