Re: [Xen-devel] Debugging Xen

["David Pilger" <pilger.david@xxxxxxxxx>]

On 1/2/07, Christoph Egger <Christoph.Egger@xxxxxxx> wrote:
> First, a happy new Year!
>
> What are the pros and cons of a xen-kernel debugger
> in your opinion?
Hi Christoph,
Happy new year!

In two words, code coverage.

Tracing over my code is my way to see if it is doing what it meant to
do. It's a programming practice I use, even if there aren't any bugs.
I'm aware that tracing is not possible at some portions of the
hypervisor, but calling a debugger loop that lets you perform actions
and interface through the serial driver is needed.

For instance, if you have a cretain IF condition in your code that
99.9% of the times it executes one path, how do you check the other
paths? mine is to change the IF condition on the fly with a debugger
and see how the program behaves on alternate paths. How do you
reproduce failures? my way is to think about all of the execution
paths that are possible for a certain situation and check all of them
using a debugger.

It all depends on the quality of the code that you produce, and the
lack of debugging capabilities at the hypervisor level makes it really
hard. Hypervisors today have a very critical role.

Anyway, this is just my need for such a debugger. but I guess others
will find it useful as well... For instance, to understand how open
source hypervisors such as Xen really works :)

How do you guys find it useful?

Thanks,
David.

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