pygdbmi - Get Structured Output from GDB's Machine Interface

API Documentation

Parse gdb machine interface string output and return structured data types (Python dicts) that are JSON serializable. Useful for writing the backend to a gdb frontend. For example, gdbgui uses pygdbmi on the backend.

Also implements a class to control gdb, GdbController, which allows programmatic control of gdb using Python, which is also useful if creating a front end.

To get machine interface output from gdb, run gdb with the --interpreter=mi2 flag.

Installation

pip install pygdbmi

Compatibility

Operating Systems

Ubuntu 14.04+

OSX:

Follow these instructions to codesign gdb if you get an error about (please check gdb is codesigned - see taskgated(8))

Windows

gdb versions

gdb 7.7+

Examples

gdb mi defines a syntax for its output that is suitable for machine readability and scripting: example output:

-> -break-insert main
<- ^done,bkpt={number="1",type="breakpoint",disp="keep",
    enabled="y",addr="0x08048564",func="main",file="myprog.c",
    fullname="/home/myprog.c",line="68",thread-groups=["i1"],
    times="0"}
<- (gdb)

Use pygdbmi.gdbmiparser.parse_response to turn that string output into a JSON serializable dictionary

from pygdbmi import gdbmiparser
from pprint import pprint
response = gdbmiparser.parse_response('^done,bkpt={number="1",type="breakpoint",disp="keep", enabled="y",addr="0x08048564",func="main",file="myprog.c",fullname="/home/myprog.c",line="68",thread-groups=["i1"],times="0"')
pprint(response)
> {'message': 'done',
 'payload': {'bkpt': {'addr': '0x08048564',
                      'disp': 'keep',
                      'enabled': 'y',
                      'file': 'myprog.c',
                      'fullname': '/home/myprog.c',
                      'func': 'main',
                      'line': '68',
                      'number': '1',
                      'thread-groups': ['i1'],
                      'times': '0',
                      'type': 'breakpoint'}},
 'type': 'result'}

Ain't that better?

But how do you get the gdb output into Python in the first place? If you want, pygdbmi also has a class to control gdb as subprocess. You can write commands, and get structured output back:

from pygdbmi.gdbcontroller import GdbController
from pprint import pprint

# Start gdb process
gdbmi = GdbController()

# Load binary a.out and get structured response
response = gdbmi.write('-file-exec-file a.out')
pprint(response)
[{'message': u'thread-group-added',
  'payload': {u'id': u'i1'},
  'type': 'notify'},
 {'message': u'done', 'payload': None, 'type': 'result'}]

Now do whatever you want with gdb. All gdb commands, as well as gdb machine interface commands are acceptable. gdb mi commands give better structured output that is machine readable, rather than gdb console output. mi commands begin with a -.

response = gdbmi.write('-break-insert main')
response = gdbmi.write('-exec-run')
response = gdbmi.write('next')
response = gdbmi.write('next')
response = gdbmi.write('continue')
response = gdbmi.exit()

Parsed Output Description

Each parsed gdb response consists of a list of dictionaries. Each dictionary has keys message, payload, token, and type.

• message contains a textual message from gdb, which is not always present. When missing, this is None.
• payload contains the content of gdb's output, which can contain any of the following: dictionary, list, string. This too is not always present, and can be None depending on the response.
• token If an input command was prefixed with a (optional) token then the corresponding output for that command will also be prefixed by that same token. This field is only present for pygdbmi output types nofity and result. When missing, this is None.

The type is defined based on gdb's various mi output record types, and can be

• result - the result of a gdb command, such as done, running, error, etc.
• notify - additional async changes that have occurred, such as breakpoint modified
• console - textual responses to cli commands
• log - debugging messages from gdb's internals
• output - output from target
• target - output from remote target
• done - when gdb has finished its output

Contributing

Set up a new virtual environment, then clone this repo and run pip install -r requirements.txt and pip install -r dev_requirements.txt.

Confirm unit tests are working with make test, then begin development.

Update unit tests as necessary at pygdbmi/tests/test\_app.py.

Projects Using pygdbmi

• gdbgui implements a browser-based frontend to gdb, using pygdbmi on the backend
• PINCE is a gdb frontend that aims to provide a reverse engineering tool and a reusable library focused on games. It uses pygdbmi to parse gdb/mi based output for some functions
• Know of another project? Create a PR and add it here.