How do you debug Xen?

How do you debug Xen?

[Emre Can Sezer]

Hi,

I want to use a debugger to debug some code I wrote in the hypervisor.
What is the best way to go about this?  I would appreciate any links or
info.

The only thing I found was enabling gdbstub and using gdb remotely via 
serial cable.  Is there an example on how to set this up?  The
examples in kgdb website refer to linux, so I'm hoping to get something
more specific. I tried to look through the mailing list archives but
couldn't find anything but the patches.

And if I'm trying to debug a 64-bit Xen, can I do this from a 32-bit
remote machine?

Thanks,

John

Debugging Xen via serial console

[Emre Can Sezer]

I'm trying to debug Xen remotely using serial port.  I followed the 
instructions on the following post made in this xen-devel list:
http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00678.html

I was able to connect gdb but I ran into a problem where even after I 
clear all the breakpoints, execution traps into gdb with SIGTRAP at 
restore_all_xen().  This only happens if I set a breakpoint and then try 
to continue after hitting the break point.  If I simply connect gdb but 
continue without setting any breakpoints, everything is OK.

The post mentions some stability issues and I haven't seen any follow 
ups.  Is this still a viable debugging method?  Or is there some other 
method I should try?

Thanks in advance,

John

Re: Debugging Xen via serial console

[Dan Doucette]

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Hi John,

The patches I submitted quickly fell out of sync with the 3.2 unstable
branch at the time.  I found a month or so later they stopped working, and I
didnt have the time to keep them up to date.
For Xen debugging, have you tried the kdb branch maintained my Mukesh Rathor
(Oracle)?  I used this a few months ago and it seemed to work.  The branch
is off the mainline, however.  Its usage is documented in the xen wiki
pages, I believe.

If you would prefer to use gdb, the functionality should be easy to
resurrect.  There really wasnt much to it.
I would recommend using my serial port splitter (ssplitd.c), which I found
easier to use and was complete in its implementation.  I submitted all the
changes in proper patch form after the posting you referenced above, if you
are interested.

Dan.




On Wed, Jan 28, 2009 at 10:53 AM, Emre Can Sezer <ecsezer@ncsu.edu> wrote:

> I'm trying to debug Xen remotely using serial port.  I followed the
> instructions on the following post made in this xen-devel list:
> http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00678.html
>
> I was able to connect gdb but I ran into a problem where even after I clear
> all the breakpoints, execution traps into gdb with SIGTRAP at
> restore_all_xen().  This only happens if I set a breakpoint and then try to
> continue after hitting the break point.  If I simply connect gdb but
> continue without setting any breakpoints, everything is OK.
>
> The post mentions some stability issues and I haven't seen any follow ups.
>  Is this still a viable debugging method?  Or is there some other method I
> should try?
>
> Thanks in advance,
>
> John
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>

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Re: Debugging Xen via serial console

[Emre Can Sezer]

Hi Dan,

I'm currently using your version of ssplitd as it is.  I haven't tried
kdb.  For some reason I thought that was for debugging guest domains.
I'll look into it.  As for resurrecting the gdbstub, I'm *NOT* familiar 
enough
with it to try it myself. I do have a few people here who might be though.
I'll post something if we get it working.

Thanks,

John

Dan Doucette wrote:
> Hi John,
>  
> The patches I submitted quickly fell out of sync with the 3.2 unstable 
> branch at the time.  I found a month or so later they stopped working, 
> and I didnt have the time to keep them up to date.
> For Xen debugging, have you tried the kdb branch maintained my Mukesh 
> Rathor (Oracle)?  I used this a few months ago and it seemed to work.  
> The branch is off the mainline, however.  Its usage is documented in 
> the xen wiki pages, I believe.
>  
> If you would prefer to use gdb, the functionality should be easy to 
> resurrect.  There really wasnt much to it.
> I would recommend using my serial port splitter (ssplitd.c), which I 
> found easier to use and was complete in its implementation.  I 
> submitted all the changes in proper patch form after the posting you 
> referenced above, if you are interested.
>  
> Dan.
>  
>
>
>  
> On Wed, Jan 28, 2009 at 10:53 AM, Emre Can Sezer <ecsezer@ncsu.edu 
> <mailto:ecsezer@ncsu.edu>> wrote:
>
>     I'm trying to debug Xen remotely using serial port.  I followed
>     the instructions on the following post made in this xen-devel list:
>     http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00678.html
>
>     I was able to connect gdb but I ran into a problem where even
>     after I clear all the breakpoints, execution traps into gdb with
>     SIGTRAP at restore_all_xen().  This only happens if I set a
>     breakpoint and then try to continue after hitting the break point.
>      If I simply connect gdb but continue without setting any
>     breakpoints, everything is OK.
>
>     The post mentions some stability issues and I haven't seen any
>     follow ups.  Is this still a viable debugging method?  Or is there
>     some other method I should try?
>
>     Thanks in advance,
>
>     John
>
>
>
>
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>     Xen-devel mailing list
>     Xen-devel@lists.xensource.com <mailto:Xen-devel@lists.xensource.com>
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>
>