Xen devel - Apr 2013 - 【Problem】 about using gdbsx to debug guest linux VM

I run a centos6.2 guest VM in xen4.1.2,  the id of centos-domU is 22.

The info of dom0 is:
2.6.32-131.21.1.el6.xendom0.x86_64 #1 SMP Tue Dec 13 18:09:29 EST 2011
x86_64 x86_64 x86_64 GNU/Linux

Centos-domU:
2.6.32-220.7.1.el6.x86_64 #1 SMP Wed Mar 7 00:52:02 GMT 2012 x86_64 x86_64
x86_64 GNU/Linux


At dom0, I went like this:
[malei@xentest-4-1 Tue Apr 30 ~]$ sudo gdbsx -a 22 64 9999
Listening on port 9999
Remote debugging from host 172.16.1.122

(After that, I found the vm became paused, but next, I should run gdb on
centos-domU,
so I set the vm to be unpaused by xl unpause 22)


Then, at centos-domU, I went like this:
(gdb) set verbose on
(gdb) set print pretty
(gdb) file /usr/lib/debug/lib/modules/2.6.32-220.el6.x86_64/vmlinux
Reading symbols from
/usr/lib/debug/lib/modules/2.6.32-220.el6.x86_64/vmlinux...done.
(gdb) directory
rpmbuild/BUILD/kernel-2.6.32-220.el6/linux-2.6.32-220.el6.x86_64/
Source directories searched:
/home/malei/rpmbuild/BUILD/kernel-2.6.32-220.el6/linux-2.6.32-220.el6.x86_64:$cdir:$cwd
(gdb) directory
/usr/src/debug/kernel-2.6.32-220.el6/linux-2.6.32-220.el6.x86_64/
Source directories searched:
/usr/src/debug/kernel-2.6.32-220.el6/linux-2.6.32-220.el6.x86_64:/home/malei/rpmbuild/BUILD/kernel-2.6.32-220.el6/linux-2.6.32-220.el6.x86_64:$cdir:$cwd
(gdb) target remote 10.18.135.250:9999
Remote debugging using 10.18.135.250:9999
[Switching to Remote target]
0xffffffffa013c5e6 in ?? ()
(gdb) b start_kernel
Breakpoint 1 at 0xffffffff81c1fb52: file init/main.c, line 564.
(gdb) c
Continuing.
Remote connection closed


At that time, messages echoed at dom0:
[malei@xentest-4-1 Tue Apr 30 ~]$ sudo gdbsx -a 22 64 9999
Listening on port 9999
Remote debugging from host 172.16.1.122
gdbsx: xg_main.c:497: xg_resume_n_wait: Assertion `_domain_is_paused()''
failed.




Why would the Assertion failure happen?
Preciate for your reply, thanks in advance.



Best regards.


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On Tue, 30 Apr 2013 14:00:53 +0800
马磊 <aware.why@gmail.com> wrote:
> I run a centos6.2 guest VM in xen4.1.2,  the id of centos-domU is 22.
> 
> The info of dom0 is:
> 2.6.32-131.21.1.el6.xendom0.x86_64 #1 SMP Tue Dec 13 18:09:29 EST 2011
> x86_64 x86_64 x86_64 GNU/Linux
> 
> Centos-domU:
> 2.6.32-220.7.1.el6.x86_64 #1 SMP Wed Mar 7 00:52:02 GMT 2012 x86_64
> x86_64 x86_64 GNU/Linux
> 
> 
> At dom0, I went like this:
> [malei@xentest-4-1 Tue Apr 30 ~]$ sudo gdbsx -a 22 64 9999
> Listening on port 9999
> Remote debugging from host 172.16.1.122
> 
> (After that, I found the vm became paused, but next, I should run gdb
> on centos-domU,
> so I set the vm to be unpaused by xl unpause 22)
Don't unpause the guest. Follow instructions in README in
tools/debugger/gdbsx.

thanks
Mukesh

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Thanks all the same.

I found the resolution that run gdb at the host not the VM and target
remote to 127.0.0.1.
But I have no idea why the VM kernel''s debuginfo should be copied to
the
host, otherwise, the function symbols were displayed  as `??` when using bt
command in gdb.


On Wed, May 1, 2013 at 3:06 AM, Mukesh Rathor
<mukesh.rathor@oracle.com>wrote:
> On Tue, 30 Apr 2013 14:00:53 +0800
> 马磊 <aware.why@gmail.com> wrote:
>
> > I run a centos6.2 guest VM in xen4.1.2,  the id of centos-domU is 22.
> >
> > The info of dom0 is:
> > 2.6.32-131.21.1.el6.xendom0.x86_64 #1 SMP Tue Dec 13 18:09:29 EST 2011
> > x86_64 x86_64 x86_64 GNU/Linux
> >
> > Centos-domU:
> > 2.6.32-220.7.1.el6.x86_64 #1 SMP Wed Mar 7 00:52:02 GMT 2012 x86_64
> > x86_64 x86_64 GNU/Linux
> >
> >
> > At dom0, I went like this:
> > [malei@xentest-4-1 Tue Apr 30 ~]$ sudo gdbsx -a 22 64 9999
> > Listening on port 9999
> > Remote debugging from host 172.16.1.122
> >
> > (After that, I found the vm became paused, but next, I should run gdb
> > on centos-domU,
> > so I set the vm to be unpaused by xl unpause 22)
>
> Don''t unpause the guest. Follow instructions in README in
> tools/debugger/gdbsx.
>
> thanks
> Mukesh
>

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