Re: [Xen-devel] gdbserver-xen / gdb crashing domU

[Kip Macy <kip.macy@xxxxxxxxx>]

domu_debug must be enabled in xen's Rules.mk, otherwise the int3 gets
passed onto the OS which will cause it to crash as it isn't expecting
to see a debug trap in ring 0 (unless of course you have a 
debugger compiled into the kernel itself). 

Just re-compile and then pass -p (pause) to xm create followed by an attach with gdbserver-xen.

       -Kip

On 9/27/05, Jonathan M. McCune <jonmccune@xxxxxxx> wrote:

Hello,

I'm trying to use gdb and gdbserver-xen to walk through the instructions
executed when starting up a domU kernel.  We are using the current
xen-unstable (linux-2.6.12-xenU).  I have followed the instructions in
tools/debugger/gdb/ and I am able to successfully attach to a running
domU kernel.  I have compiled the domU kernel with debug options as
described in tools/debugger/gdb/README.  After attaching to the running
domU kernel, I observe the following behavior:

Issuing the gdb commands 'step', 'stepi', 'next', and 'nexti' when the
domU kernel is initially paused all crash the domU kernel silently
(i.e., the state of said domU goes to 'c' if you issue an `xm list` in
dom0).  'continue' causes the domU kernel to boot up correctly.

All the breakpoints I've tried setting so far (setting the breakpoints
before issuing the 'continue' in gdb) cause the domU kernel to panic
when the function at which the breakpoint is set gets run.  Functions
I've tried setting breakpoints for include dup_task_struct, queue_work,
scheduler_tick, and activate_task.

Is it possible to step through the domU kernel code as it is booted in Xen?

Thanks,
-Jon



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