Xen devel - Jun 2006 - Anybody got a tool to peer into a guest domain?

Folks --

I''m -still- trying to get FreeBSD 6.0 up and running on VT-x  
hardware.  I''m at a point, per an earlier mail of mine where QEMU seg  
faults and leaves the guest domain in a blocked state.  I''d like to  
know what code was executing in the guest domain at the point QEMU  
seg faulted.

So, I''m looking for a tool to dump the register state of the guest  
domain and show some memory regions: code around the eip and esp leap  
to mind.  What''s a good tool for doing this?

-- Randy

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On 8 Jun 2006, at 04:46, Randy Thelen wrote:
> I''m -still- trying to get FreeBSD 6.0 up and running on VT-x
hardware.
>  I''m at a point, per an earlier mail of mine where QEMU seg faults
and
> leaves the guest domain in a blocked state.  I''d like to know what
> code was executing in the guest domain at the point QEMU seg faulted.
>
> So, I''m looking for a tool to dump the register state of the guest
> domain and show some memory regions: code around the eip and esp leap 
> to mind.  What''s a good tool for doing this?
The gdb debugger stub has been updated to work with HVM guests. See 
some docs under tools/debugger/gdb. tools/misc/xenctx might also work. 
Not sure it''s been updated for HVm guests though.

  -- Keir


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Keir Fraser wrote:
> The gdb debugger stub has been updated to work with HVM guests. See  
> some docs under tools/debugger/gdb.
After reading the README in that directory and following its  
directions, I''m still not successful at getting gdbserver to run.

Here is what I did:

$ ./gdbbuild
...
$ cp gdb-6.2.1-linux-i386-xen/gdb/gdbserver/gdbserver /usr/bin/

(email I''ve read since that operation indicate I should rename  
gdbserver to gdbserver-xen.  And the README states that the file will  
already be called gdbserver-xen, which it isn''t.)

$ xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0     1677     2 r-----   721.9
Linux-hvm                         10      256     1 -b----    25.0
$ gdbserver 127.0.0.1:9999 --attach 10
Cannot attach to process 10: Operation not permitted (1)
$

Hmm.

$ whoami
root
$

Some documentation indicates that I need to compile the guest domain  
kernel with:

 > Build your kernel with debug.  I use the flags
 >   "verbose=y domu_debug=y debug=y".  although I dont know if
these
 >   are all required.

But, I''m trying to debug a HVM domain with a FreeBSD, which leaves me  
with what options?  And, I''m debugging an arbitrary piece of code in  
that domain ... btxldr?  ficl?  Don''t know.  That''s part of
why I
need to peer into the domain.

-- Randy

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On 8 Jun 2006, at 19:34, Randy Thelen wrote:
> Some documentation indicates that I need to compile the guest domain 
> kernel with:
>
> > Build your kernel with debug.  I use the flags
> >   "verbose=y domu_debug=y debug=y".  although I dont know if
these
> >   are all required.
>
> But, I''m trying to debug a HVM domain with a FreeBSD, which leaves
me
> with what options?  And, I''m debugging an arbitrary piece of code
in
> that domain ... btxldr?  ficl?  Don''t know.  That''s part
of why I need
> to peer into the domain.
Those are build options for Xen.

There should be others on the list who can give tips (e.g., maybe some 
of the Intel guys).

  -- Keir


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