Debug python3 with gdb on photon linux

photon-py3-gdb-debug.md

Debug python3 process with GDB on Photon Linux

• Enable the debuginfo package repository.

  In /etc/yum.repos.d/photon-debuginfo.repo change enabled=0 to enable=1.

  /etc/yum.repos.d/photon-debuginfo.repo should look like this

  [photon-debuginfo]
  name=VMware Photon Linux debuginfo $releasever ($basearch)
  baseurl=https://packages.vmware.com/photon/$releasever/photon_debuginfo_$releasever_$basearch
  gpgkey=file:///etc/pki/rpm-gpg/VMWARE-RPM-GPG-KEY
  gpgcheck=1
  enabled=1
  skip_if_unavailable=True
  

• Install matching gdb, python3, python3-devel, and python3-debuginfo packages. At the time of this writting the python3-debuginfo package is older than the current python3 packages.

  tdnf install gdb python3==3.7.0 python3-devel==3.7.0 python3-debuginfo

• Download the python extensions for gdb from cypthon's source tree. Download the version from the tag matching the python version we installed. (3.7.0 in this case).

  wget https://raw.githubusercontent.com/python/cpython/v3.7.0/Tools/gdb/libpython.py

• Start gdb with the -p option to attach to our running python process.

  gdb -p <pid>

• If everything goes well, you will see gdb load python's debug headers.

  Reading symbols from /usr/bin/python3.7...Reading symbols from /usr/lib/debug/bin/python3.7-3.7.0-6.ph3.x86_64.debug...done.

• Source the python extension in your gdb session

  source libpython.py

• Now get a python backtrace from gdb using py-bt

  (gdb) source libpython.py
  (gdb) py-bt
  Traceback (most recent call first):
    <built-in method sleep of module object at remote 0x7f3b243b7d18>
    File "/usr/lib/python3.7/site-packages/salt/utils/process.py", line 662, in run
      time.sleep(10)
    <built-in method next of module object at remote 0x7f3b2460cc28>
    File "/usr/lib/python3.7/site-packages/salt/ext/tornado/gen.py", line 309, in wrapper
      yielded = next(result)
    File "/usr/lib/python3.7/site-packages/salt/master.py", line 831, in start
      self.process_manager.run()
    File "/usr/lib/python3.7/site-packages/salt/cli/daemons.py", line 217, in start
      self.master.start()
    File "/usr/lib/python3.7/site-packages/salt/scripts.py", line 104, in salt_master
      master.start()
    File "/usr/bin/salt-master", line 11, in <module>
      load_entry_point('salt==3002.5', 'console_scripts', 'salt-master')()
  

• Check out some of the other python extenssion commands: py-bt-full, py-down, py-list, py-locals, py-print, py-up, python, python-interactive