[Vm-dev] Has anyone done a tutorial on...

Phil B pbpublist at gmail.com
Wed Sep 20 21:17:07 UTC 2017

In short, I seem to have a knack for finding hard to debug issues.

1) I have an issue related to some parsers I'm working on  re: large # of
stack pages in use.  Eliot provided some helpful tips a couple of months
ago that really helped here.  It turns out I had two different issues
related to this, one resolved (thanks to the image side VM params he
pointed me to) the other still outstanding (probably a deeper structural
issue and I'm thinking that the easier way to debug it will be to dial back
the stack pages and let it crash earlier). These are bugs in my code and
not not the VM.

2) Under heavy load I'm having problems with Event Tickler spiking in CPU
usage (50% or more) and the image becoming generally unresponsive.  Event
Tickler never seems to recover once in this state.

3) A variety of site-specific network socket issues.  I think I've done
about all I can in the image and need to start looking in the plugin but i
suspect that's only going to be productive on live connections w/ gdb.

4) Generally needing to be able to more quickly troubleshoot plugin and FFI
issues.  My images are heavy users of both and I've run into a variety of
edge cases where I segfault the VM.

Over time, I seem to keep running into issues like these so that's why I'm
looking to improve my debugging skills at the VM/image boundary.

On Sep 19, 2017 8:12 AM, "Bert Freudenberg" <bert at freudenbergs.de> wrote:

On Tue, Sep 19, 2017 at 1:25 AM, Phil B <pbpublist at gmail.com> wrote:

> Using gdb to explore a running image?  Blog post or video format is
> great.  Most of what I've run across is related to the internals of the VM
> rather than debugging an image.  My gdb skills are pretty rusty plus I
> suspect that not knowing all of the helper functions available in the VM
> (and how to best use them in a debugging workflow) is slowing me down.

​I'm curious about your use case, that is, what problem are you actually
trying to debug?

- Bert -​
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