[Qemu-devel] WinDbg module

[Qemu-devel] WinDbg module

[Mihail Abakumov]

Hello.

We made the debugger module WinDbg (like GDB) for QEMU. This is the 
replacement of the remote stub in Windows kernel. Used for remote 
Windows kernel debugging without debugging mode.

The latest build and instructions for the launch can be found here: 
https://github.com/ispras/qemu/releases/tag/v2.7.50-windbg

Currently only one ways to create a remote debugging connection is 
supported: using COM port with named pipe.

Should I prepare patches for inclusion in the master branch? Or is it 
too specific module and it is not needed?

-- 
Thanks,
Mihail Abakumov

Re: [Qemu-devel] WinDbg module

[Marc-André Lureau]

Hi

On Wed, Apr 12, 2017 at 6:44 PM Mihail Abakumov <mikhail.abakumov@ispras.ru>
wrote:

> Hello.
>
> We made the debugger module WinDbg (like GDB) for QEMU. This is the
> replacement of the remote stub in Windows kernel. Used for remote
> Windows kernel debugging without debugging mode.
>
> The latest build and instructions for the launch can be found here:
> https://github.com/ispras/qemu/releases/tag/v2.7.50-windbg
>
> Currently only one ways to create a remote debugging connection is
> supported: using COM port with named pipe.
>
> Should I prepare patches for inclusion in the master branch? Or is it
> too specific module and it is not needed?
>

Great news! A few years ago, I looked into this with a colleague to speed
up debugging, but we were stuck (can't remember the blocking factor, but
the lack of documentation was not helping). I think some windows driver
developers would be quite happy with it, which makes it a good candidate
for inclusion. Please prepare patches!


-- 
Marc-André Lureau

Re: [Qemu-devel] WinDbg module

[Roman Kagan]

On Wed, Apr 12, 2017 at 05:05:45PM +0300, Mihail Abakumov wrote:
> Hello.
> 
> We made the debugger module WinDbg (like GDB) for QEMU. This is the
> replacement of the remote stub in Windows kernel. Used for remote Windows
> kernel debugging without debugging mode.
> 
> The latest build and instructions for the launch can be found here:
> https://github.com/ispras/qemu/releases/tag/v2.7.50-windbg
> 
> Currently only one ways to create a remote debugging connection is
> supported: using COM port with named pipe.
> 
> Should I prepare patches for inclusion in the master branch? Or is it too
> specific module and it is not needed?

Please do!

Every once in a while dealing with a Windows guest problem I wished I
had this.  We at Virtuozzo looked into doing something like this but
never got around to.

Thanks,
Roman.

Re: [Qemu-devel] WinDbg module

[Stefan Weil]

Am 12.04.2017 um 18:30 schrieb Roman Kagan:
> On Wed, Apr 12, 2017 at 05:05:45PM +0300, Mihail Abakumov wrote:
>> Hello.
>>
>> We made the debugger module WinDbg (like GDB) for QEMU. This is the
>> replacement of the remote stub in Windows kernel. Used for remote Windows
>> kernel debugging without debugging mode.
>>
>> The latest build and instructions for the launch can be found here:
>> https://github.com/ispras/qemu/releases/tag/v2.7.50-windbg
>>
>> Currently only one ways to create a remote debugging connection is
>> supported: using COM port with named pipe.
>>
>> Should I prepare patches for inclusion in the master branch? Or is it too
>> specific module and it is not needed?
>
> Please do!
>
> Every once in a while dealing with a Windows guest problem I wished I
> had this.  We at Virtuozzo looked into doing something like this but
> never got around to.
>
> Thanks,
> Roman.
>

Hello Mihail,

from the previous answers you can see that there is a
need for WinDbg support.

If you want to prepare patches for the official QEMU,
you need signed commits from all developers who contributed
(Dmitry Koltunov and you?).

Make also sure that no licensed code (for example extracts
from MS header files) gets added.

See http://wiki.qemu-project.org/Contribute/SubmitAPatch for
more hints.

As far as I saw, WinDbg support adds several thousand lines
of code. Do you want to support that code after it has been
included in QEMU?

Cheers
Stefan

Re: [Qemu-devel] WinDbg module

[Mihail Abakumov]

Stefan Weil писал 2017-04-12 20:55:
> Am 12.04.2017 um 18:30 schrieb Roman Kagan:
>> On Wed, Apr 12, 2017 at 05:05:45PM +0300, Mihail Abakumov wrote:
>>> Hello.
>>> 
>>> We made the debugger module WinDbg (like GDB) for QEMU. This is the
>>> replacement of the remote stub in Windows kernel. Used for remote 
>>> Windows
>>> kernel debugging without debugging mode.
>>> 
>>> The latest build and instructions for the launch can be found here:
>>> https://github.com/ispras/qemu/releases/tag/v2.7.50-windbg
>>> 
>>> Currently only one ways to create a remote debugging connection is
>>> supported: using COM port with named pipe.
>>> 
>>> Should I prepare patches for inclusion in the master branch? Or is it 
>>> too
>>> specific module and it is not needed?
>> 
>> Please do!
>> 
>> Every once in a while dealing with a Windows guest problem I wished I
>> had this.  We at Virtuozzo looked into doing something like this but
>> never got around to.
>> 
>> Thanks,
>> Roman.
>> 
> 
> Hello Mihail,
> 
> from the previous answers you can see that there is a
> need for WinDbg support.
> 
> If you want to prepare patches for the official QEMU,
> you need signed commits from all developers who contributed
> (Dmitry Koltunov and you?).
> 
> Make also sure that no licensed code (for example extracts
> from MS header files) gets added.
> 
> See http://wiki.qemu-project.org/Contribute/SubmitAPatch for
> more hints.
> 
> As far as I saw, WinDbg support adds several thousand lines
> of code. Do you want to support that code after it has been
> included in QEMU?
> 
> Cheers
> Stefan

Yes, of course. We can support it.

Thanks,
Mihail Abakumov

Re: [Qemu-devel] WinDbg module

[Denis V. Lunev]

On 04/12/2017 05:05 PM, Mihail Abakumov wrote:
> Hello.
>
> We made the debugger module WinDbg (like GDB) for QEMU. This is the
> replacement of the remote stub in Windows kernel. Used for remote
> Windows kernel debugging without debugging mode.
>
> The latest build and instructions for the launch can be found here:
> https://github.com/ispras/qemu/releases/tag/v2.7.50-windbg
>
> Currently only one ways to create a remote debugging connection is
> supported: using COM port with named pipe.
>
> Should I prepare patches for inclusion in the master branch? Or is it
> too specific module and it is not needed?
>
this would be indeed useful. We have a lot of problems
with Windows debugging. In general, Windows behaviour
with and without debugger is different.

Den

Re: [Qemu-devel] WinDbg module

[Ladi Prosek]

Hi,

On Wed, Apr 12, 2017 at 4:05 PM, Mihail Abakumov
<mikhail.abakumov@ispras.ru> wrote:
> Hello.
>
> We made the debugger module WinDbg (like GDB) for QEMU. This is the
> replacement of the remote stub in Windows kernel. Used for remote Windows
> kernel debugging without debugging mode.

This is awesome!

> The latest build and instructions for the launch can be found here:
> https://github.com/ispras/qemu/releases/tag/v2.7.50-windbg
>
> Currently only one ways to create a remote debugging connection is
> supported: using COM port with named pipe.

The linked v2.7.50-windbg seems to be a Windows release. Does it also
work on Linux hosts with KVM?

Also,

  #ifdef TARGET_X86_64 // Unimplemented yet
  #error Unsupported Architecture
  #endif

can you estimate the amount of work to support 64-bit?

Thanks!
Ladi

> Should I prepare patches for inclusion in the master branch? Or is it too
> specific module and it is not needed?
>
> --
> Thanks,
> Mihail Abakumov
>

Re: [Qemu-devel] WinDbg module

[Mihail Abakumov]

Ladi Prosek писал 2017-04-13 10:02:
> 
> The linked v2.7.50-windbg seems to be a Windows release. Does it also
> work on Linux hosts with KVM?
> 

I haven't tested it yet, but it should work.

> 
> Also,
> 
>   #ifdef TARGET_X86_64 // Unimplemented yet
>   #error Unsupported Architecture
>   #endif
> 
> can you estimate the amount of work to support 64-bit?
> 

At the moment I can't implement support for x86_64 arch. At least due to 
the fact that any OS Windows that I tried crashes on this architecture.

Thanks,
Mihail Abakumov