[BUG] gdbsx crashes Xen

[BUG] gdbsx crashes Xen

[Carl Patenaude Poulin]

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Hey folks,

With gdbsx running, Running `gdb -ex "target remote localhost:9999"
crashes Xen and reboots the server.

Example session: http://i.imgur.com/UXh3RCy.png

Minimal reproduction: https://github.com/lilred/xen-crash-repro

Top line of `xl dmesg`:

    Xen version 4.6.0 (root@CS.McGill.CA) (gcc (Ubuntu 5.2.1-22ubuntu2)
5.2.1 20151010) debug=y Mon Dec 28 21:34:16 EST 2015

Output of `lsb_release -a`:

    No LSB modules are available.
    Distributor ID: Ubuntu
    Description:    Ubuntu 15.10
    Release:        15.10
    Codename:       wily

I can provide more information if you tell me what to look for. Also,
I would LOVE a work-around.

Best

Carl Patenaude Poulin
B. Eng. Software Engineering student
McGill University

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Re: [BUG] gdbsx crashes Xen

[Andrew Cooper]

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On 11/02/16 16:25, Carl Patenaude Poulin wrote:
> Hey folks,
>
> With gdbsx running, Running `gdb -ex "target remote localhost:9999"
> crashes Xen and reboots the server.
>
> Example session: http://i.imgur.com/UXh3RCy.png
>
> Minimal reproduction: https://github.com/lilred/xen-crash-repro
>
> Top line of `xl dmesg`:
>
>     Xen version 4.6.0 (root@CS.McGill.CA <mailto:root@CS.McGill.CA>)
> (gcc (Ubuntu 5.2.1-22ubuntu2) 5.2.1 20151010) debug=y Mon Dec 28
> 21:34:16 EST 2015
>
> Output of `lsb_release -a`:
>
>     No LSB modules are available.
>     Distributor ID: Ubuntu
>     Description:    Ubuntu 15.10
>     Release:        15.10
>     Codename:       wily
>
> I can provide more information if you tell me what to look for. Also,
> I would LOVE a work-around.

At the very minimum, you need to set up a serial console and capture the
panic log.

Are you on Broadwell hardware by any chance?  I fixed a SMAP violation
in that hypercall a little while ago.

~Andrew

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Re: [BUG] gdbsx crashes Xen

[Carl Patenaude Poulin]

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Hi all,

Sorry for the delay. I've managed to get some serial console output.

https://gist.github.com/lilred/50285e1f33ab1c881ea0

I am not on Broadwell hardware. I'm using a PowerEdge R300 machine,
with a Xeon x5460 CPU.

Best

On Thu, Feb 11, 2016 at 11:35 AM, Andrew Cooper <andrew.cooper3@citrix.com>
wrote:

> On 11/02/16 16:25, Carl Patenaude Poulin wrote:
>
> Hey folks,
>
> With gdbsx running, Running `gdb -ex "target remote localhost:9999"
> crashes Xen and reboots the server.
>
> Example session: http://i.imgur.com/UXh3RCy.png
>
> Minimal reproduction: https://github.com/lilred/xen-crash-repro
>
> Top line of `xl dmesg`:
>
>     Xen version 4.6.0 (root@CS.McGill.CA) (gcc (Ubuntu 5.2.1-22ubuntu2)
> 5.2.1 20151010) debug=y Mon Dec 28 21:34:16 EST 2015
>
> Output of `lsb_release -a`:
>
>     No LSB modules are available.
>     Distributor ID: Ubuntu
>     Description:    Ubuntu 15.10
>     Release:        15.10
>     Codename:       wily
>
> I can provide more information if you tell me what to look for. Also,
> I would LOVE a work-around.
>
>
> At the very minimum, you need to set up a serial console and capture the
> panic log.
>
> Are you on Broadwell hardware by any chance?  I fixed a SMAP violation in
> that hypercall a little while ago.
>
> ~Andrew
>

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Re: [BUG] gdbsx crashes Xen

[Andrew Cooper]

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On 27/02/16 03:26, Carl Patenaude Poulin wrote:

Please don't top post.

> Hi all,
>
> Sorry for the delay. I've managed to get some serial console output.
>
> https://gist.github.com/lilred/50285e1f33ab1c881ea0
>
> I am not on Broadwell hardware. I'm using a PowerEdge R300 machine,
> with a Xeon x5460 CPU.
>
> Best

That is unfortunate.

Can you run `addr2line -e xen-syms ffff82d080217ae2` to find out exactly
which line the crash is from?

What kind of domain are you running?  It looks like an HVM domain.  If
so, can you possibly also, from dom0, run `xen-hvmctx $DOMID` before
attaching debugging?

~Andrew

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