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Re: [Xen-devel] gdbsx - xg_attach:Unable to pause domain:1; failed to attach to domain:1 errno:13



Hi Mukesh:

 

Thanks for your help on enabling gdbsx…

 

> Hmm... that all seems ok then. Can you check your permissions on :

 

> /proc/xen/privcmd

 

  root@piet-openxen-blade:~# ls -l /proc/xen/privcmd

  -rw------- 1 root root 0 Aug 11 13:37 /proc/xen/privcmd

 

Privcmd seems to be a hypervisor call available from userland

For Xen developers:

 

      http://sanifool.com/2013/02/08/invoking-an-hypercall-from-userland-via-privcmd/

 

 

>  Other possibilities:

>   - do you have xsm enabled?

 

Don’t  think so. I’ve heard this security stuff can get in the way.

Doing a  ‘xl list –Z’ doesn’t show any security labels.                                            [Wish I had Synergy Installed]

 

 

>-  can you put a printk in xen file common/domctl.c:

 

Sure but first I likely need to start using the openxen code that I compiled from src.

I’m currently using openxen installed via a Ubuntu 14.04 package.

 

Mind explaining the best way to proceed on switching to the openxen

That I compiled from source? I thought  some of it might be installed at /usr/local/

And perhaps just changing a search path or two will be sufficient.

 

I suspect I’ll need to put a new xen kernel on /boot and update the grub config.

 

 

>    case XEN_DOMCTL_pausedomain:

>        ret = -EINVAL;

>+       printk(">>>>>>>>> Pause domain:%d current:%d\n", d->domain_id,

>+              current->domain->domain_id);

>      if ( d != current->domain )

>            ret = domain_pause_by_systemcontroller(d);

>        break;

 

Ok, I added your suggested prink() call above.

 

Ø  if you don't see this printk then the problem is in dom0 linux, prob some permissions either on the privcmd file or somewhere in FS path.

 

Ø  > Wondering if the host kernel has to be configured to support gdb

Ø  > attaching with gdbsx.

 

Ø  Nop, at this point you are just not able to establish connection with xen. gdb is not involved.

 

Great, perhaps I just need to do is install the openxen I just compiled.

Your suggestions on exactly how to do that would be greatly appreciated.

 

Ø  -Mukesh

 

-piet

 

--

Pete/Piet Delaney                                              

O: +1 408 935-1813

C: +1 408 646-8557

H: +1 408 243-8872

Home Email: piet.delaney@xxxxxxxxx

 

 

 

 

-----Original Message-----
From: Mukesh Rathor [mailto:mukesh.rathor@xxxxxxxxxx]
Sent: Wednesday, August 27, 2014 11:25 AM
To: Pete Delaney
Cc: xen-devel@xxxxxxxxxxxxx; piet.delaney@xxxxxxxxx; Elaine Huang
Subject: Re: gdbsx - xg_attach:Unable to pause domain:1; failed to attach to domain:1 errno:13

 

On Wed, 27 Aug 2014 03:02:54 +0000

Pete Delaney <pdelaney@xxxxxxxxxxxxxxx> wrote:

 

> Hi Mukesh:

>

>     > Hmm... I just tried and it worked for me, so things are ok it

>     > seems on latest xen/linux. The errno EPERM indicates something

>     > might not be properly setup. Are you able to run other xen

>     > commands like xl list, etc? I see you are running as root, are

>     > you running gdbsx on dom0?

> Gdbsx runs on dom0, which I believe is the same as running on the host

> when it's booting for Xen support in the grub selection. On the host

> the Xen commands are available as I showed in my initial email, I used

> the "xl list" and "xl pause" commands:

>

>     >  root@piet-openxen:~# xl list

>     >      Name                                        ID   Mem

>     > VCPUs  State   Time(s)

>     >      Domain-0                                     0 14734

>     >      12     r-----    8562.9

>     >      New_PV_Driver                                1  1023

>     >      4     -b----      50.3

>    >  root@piet-openxen:~#

>

>     > root@piet-openxen-blade:~# xl pause 1

>

>

> I was running as root on the host/dom0.

 

Hmm... that all seems ok then. Can you check your permissions on :

 

/proc/xen/privcmd

 

 

Other possibilites:

  - do you have xsm enabled?

 

  - can you put a printk in xen file common/domctl.c:

 

    case XEN_DOMCTL_pausedomain:

        ret = -EINVAL;

+       printk(">>>>>>>>> Pause domain:%d current:%d\n", d->domain_id,

+              current->domain->domain_id);

        if ( d != current->domain )

            ret = domain_pause_by_systemcontroller(d);

        break;

 

if you don't see this printk then the problem is in dom0 linux, prob some permissions either on the privcmd file or somewhere in FS path.

 

> Wondering if the host kernel has to be configured to support gdb

> attaching with gdbsx.

 

Nop, at this point you are just not able to establish connection with xen. gdb is not involved.

 

-Mukesh

 

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