VMWare Workstation 6 for debugging Linux Kernel (!)

VMWare Workstation 6 for debugging Linux Kernel (!)

[roland]

Hi !

I think this one is damn interestig for linux kernel development:

link: http://stackframe.blogspot.com/
contents: see below

regards
roland

ps:
i`m not directly related to vmware - so this is no advertisement!


Tuesday, April 17, 2007
Debugging Linux kernels with Workstation 6.0
We just quietly added an exciting feature to Workstation 6.0. I believe it 
will make WS6 a great tool for Linux kernel development. You can now debug 
kernel of Linux VM with gdb running on the Host without changing anything in 
the Guest VM. No kdb, no recompiling and no need for second machine. All you 
need is a single line in VM's configuration file.

To use the new feature, grab the latest build of WS6 here:

http://www.vmware.com/products/beta/ws/

Put this line into configuration file of your Linux VM:

debugStub.listen.guest32=1

Now whenever you run the virtual machine, you'll see the following on the 
Host console:

VMware Workstation is listening for debug connection on port 8832.

Run gdb on the Host, reference it to the kernel with symbols and attach to 
the virtual machine:

% gdb
(gdb) file vmlinux-2.4.21-27.EL.debug
(gdb) target remote localhost:8832

That's it. The VM is blocked now, so you can "continue" it and "^C" back to 
gdb. Breakpoints, single step, memory inspection - all this works as usual. 
If you have SMP VM, then each VCPU is mapped on a thread, so use "info 
threads" and "thread NN" to switch between them.

The kernels with symbols are sadly lacking on most distributions, but if you 
use RHEL then this website may help (look for kernel-debuginfo rpm):

http://people.redhat.com/duffy/debuginfo/index-js.html

The gdb support in WS6 is experimental, so there may be rough edges here and 
there. Please post on community forums if something doesn't work right or if 
you have a suggestion:

http://www.vmware.com/community/

There are more debugging specific features in WS6 (for example, you can use 
gdb hand-in-hand with Record/Replay!). I will describe them shortly.

RE: VMWare Workstation 6 for debugging Linux Kernel (!)

[albcamus]

Hi roland,
 It's really an interesting feature,  IMHO,  maybe the UML would be no
more needed.
thanks very much;-)

Regards,


2007/4/20, roland <devzero@web.de>:
> Hi !
>
> I think this one is damn interestig for linux kernel development:
>
> link: http://stackframe.blogspot.com/
> contents: see below
>
> regards
> roland
>
> ps:
> i`m not directly related to vmware - so this is no advertisement!
>
>
> Tuesday, April 17, 2007
> Debugging Linux kernels with Workstation 6.0
> We just quietly added an exciting feature to Workstation 6.0. I believe it
> will make WS6 a great tool for Linux kernel development. You can now debug
> kernel of Linux VM with gdb running on the Host without changing anything in
> the Guest VM. No kdb, no recompiling and no need for second machine. All you
> need is a single line in VM's configuration file.
>
> To use the new feature, grab the latest build of WS6 here:
>
> http://www.vmware.com/products/beta/ws/
>
> Put this line into configuration file of your Linux VM:
>
> debugStub.listen.guest32=1
>
> Now whenever you run the virtual machine, you'll see the following on the
> Host console:
>
> VMware Workstation is listening for debug connection on port 8832.
>
> Run gdb on the Host, reference it to the kernel with symbols and attach to
> the virtual machine:
>
> % gdb
> (gdb) file vmlinux-2.4.21-27.EL.debug
> (gdb) target remote localhost:8832
>
> That's it. The VM is blocked now, so you can "continue" it and "^C" back to
> gdb. Breakpoints, single step, memory inspection - all this works as usual.
> If you have SMP VM, then each VCPU is mapped on a thread, so use "info
> threads" and "thread NN" to switch between them.
>
> The kernels with symbols are sadly lacking on most distributions, but if you
> use RHEL then this website may help (look for kernel-debuginfo rpm):
>
> http://people.redhat.com/duffy/debuginfo/index-js.html
>
> The gdb support in WS6 is experimental, so there may be rough edges here and
> there. Please post on community forums if something doesn't work right or if
> you have a suggestion:
>
> http://www.vmware.com/community/
>
> There are more debugging specific features in WS6 (for example, you can use
> gdb hand-in-hand with Record/Replay!). I will describe them shortly.
>
>
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>

Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Xavier Bestel]

On Fri, 2007-04-20 at 00:46 +0200, roland wrote:

> We just quietly added an exciting feature to Workstation 6.0. I believe it 
> will make WS6 a great tool for Linux kernel development. You can now debug 
> kernel of Linux VM with gdb running on the Host without changing anything in 
> the Guest VM. No kdb, no recompiling and no need for second machine. All you 
> need is a single line in VM's configuration file.

I think qemu has the exact same feature.

	Xav

Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Andi Kleen]

Xavier Bestel <xavier.bestel@free.fr> writes:

> On Fri, 2007-04-20 at 00:46 +0200, roland wrote:
> 
> > We just quietly added an exciting feature to Workstation 6.0. I believe it 
> > will make WS6 a great tool for Linux kernel development. You can now debug 
> > kernel of Linux VM with gdb running on the Host without changing anything in 
> > the Guest VM. No kdb, no recompiling and no need for second machine. All you 
> > need is a single line in VM's configuration file.
> 
> I think qemu has the exact same feature.

It doesn't seem to work for x86-64 there though.

AMD SimNow! and Virtutech Simics can do it too. But great the Vmware catches up.

-Andi

RE: VMWare Workstation 6 for debugging Linux Kernel (!)

[devzero]

>  It's really an interesting feature,  IMHO,  maybe the UML would be no
> more needed.

if you speak of debugging , uml seems to have another competitor now.

maybe somebody make some side by side comparison of vmware & uml regarding kernel debugging. (and also compare that to traditional debugging via serial line or network)

regards
roland



> -----Ursprüngliche Nachricht-----
> Von: albcamus <albcamus@gmail.com>
> Gesendet: 20.04.07 09:16:53
> An: roland <devzero@web.de>
> CC: linux-kernel@vger.kernel.org
> Betreff: RE: VMWare Workstation 6 for debugging Linux Kernel (!)


> 
> Hi roland,
>  It's really an interesting feature,  IMHO,  maybe the UML would be no
> more needed.
> thanks very much;-)
> 
> Regards,
> 
> 
> 2007/4/20, roland <devzero@web.de>:
> > Hi !
> >
> > I think this one is damn interestig for linux kernel development:
> >
> > link: http://stackframe.blogspot.com/
> > contents: see below
> >
> > regards
> > roland
> >
> > ps:
> > i`m not directly related to vmware - so this is no advertisement!
> >
> >
> > Tuesday, April 17, 2007
> > Debugging Linux kernels with Workstation 6.0
> > We just quietly added an exciting feature to Workstation 6.0. I believe it
> > will make WS6 a great tool for Linux kernel development. You can now debug
> > kernel of Linux VM with gdb running on the Host without changing anything in
> > the Guest VM. No kdb, no recompiling and no need for second machine. All you
> > need is a single line in VM's configuration file.
> >
> > To use the new feature, grab the latest build of WS6 here:
> >
> > http://www.vmware.com/products/beta/ws/
> >
> > Put this line into configuration file of your Linux VM:
> >
> > debugStub.listen.guest32=1
> >
> > Now whenever you run the virtual machine, you'll see the following on the
> > Host console:
> >
> > VMware Workstation is listening for debug connection on port 8832.
> >
> > Run gdb on the Host, reference it to the kernel with symbols and attach to
> > the virtual machine:
> >
> > % gdb
> > (gdb) file vmlinux-2.4.21-27.EL.debug
> > (gdb) target remote localhost:8832
> >
> > That's it. The VM is blocked now, so you can "continue" it and "^C" back to
> > gdb. Breakpoints, single step, memory inspection - all this works as usual.
> > If you have SMP VM, then each VCPU is mapped on a thread, so use "info
> > threads" and "thread NN" to switch between them.
> >
> > The kernels with symbols are sadly lacking on most distributions, but if you
> > use RHEL then this website may help (look for kernel-debuginfo rpm):
> >
> > http://people.redhat.com/duffy/debuginfo/index-js.html
> >
> > The gdb support in WS6 is experimental, so there may be rough edges here and
> > there. Please post on community forums if something doesn't work right or if
> > you have a suggestion:
> >
> > http://www.vmware.com/community/
> >
> > There are more debugging specific features in WS6 (for example, you can use
> > gdb hand-in-hand with Record/Replay!). I will describe them shortly.
> >
> >
> >
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> >
> 


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Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Petr Vandrovec]

Andi Kleen wrote:
> Xavier Bestel <xavier.bestel@free.fr> writes:
> 
>> On Fri, 2007-04-20 at 00:46 +0200, roland wrote:
>>
>>> We just quietly added an exciting feature to Workstation 6.0. I believe it 
>>> will make WS6 a great tool for Linux kernel development. You can now debug 
>>> kernel of Linux VM with gdb running on the Host without changing anything in 
>>> the Guest VM. No kdb, no recompiling and no need for second machine. All you 
>>> need is a single line in VM's configuration file.
>> I think qemu has the exact same feature.
> 
> It doesn't seem to work for x86-64 there though.

Hello,

Do you mean with qemu or with VMware?  Yes, we do not support replay 
with 64bit guests, but debug interface should just work.  Only gotcha is 
that for 64bit guest you need another option:

debugStub.listen.guest64 = "TRUE"

and then you need to attach gdb to port 8864 (*).  Unfortunately it does 
not seem possible to build gdb which would support 16bit/32bit code 
while using 64bit gdb on-wire format, so there are two interfaces.  And 
if you single-step switch from 64bit mode to 32bit mode or back, you 
also have to switch gdbs.  Yes, it is a bit unintuitive, and 
additionally one gdb silently ignores breakpoints set up by other gdb, 
so you need to keep breakpoints in sync between two gdbs yourself :-(

(*) If you are using gdb which has both 32bit and 64bit support, be sure 
to issue appropriate 'set architecture xxx' before 'target remote 
localhost:88xx' (i386:x86-64 for port 8864, i386 or i8086 for port 
8832).  Otherwise gdb is going to die complaining it could not parse 
remote reply.

				Best regards,
					Petr Vandrovec

P.S.: Yes, I'm associated with VMware.

Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Nigel Cunningham]

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Hi.

On Fri, 2007-04-20 at 12:27 +0200, Andi Kleen wrote:
> Xavier Bestel <xavier.bestel@free.fr> writes:
> 
> > On Fri, 2007-04-20 at 00:46 +0200, roland wrote:
> > 
> > > We just quietly added an exciting feature to Workstation 6.0. I believe it 
> > > will make WS6 a great tool for Linux kernel development. You can now debug 
> > > kernel of Linux VM with gdb running on the Host without changing anything in 
> > > the Guest VM. No kdb, no recompiling and no need for second machine. All you 
> > > need is a single line in VM's configuration file.
> > 
> > I think qemu has the exact same feature.
> 
> It doesn't seem to work for x86-64 there though.

You mean the VMware one doesn't work? I tried it and got:

(gdb) target remote localhost:8832 
Remote debugging using localhost:8832 
Ignoring packet error, continuing... 
warning: unrecognized item "timeout" in "qSupported" respoonse 
Ignoring packet error, continuing... 
Ignoring packet error, continuing... 
Ignoring packet error, continuing... 
Malformed response to offset query, timeout 
(gdb)

Hopefully that's not too hard to fix. Made the appropriate noises :)

Nigel

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Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Nigel Cunningham]

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Hi.

On Fri, 2007-04-20 at 04:21 -0700, Petr Vandrovec wrote:
> Andi Kleen wrote:
> > Xavier Bestel <xavier.bestel@free.fr> writes:
> > 
> >> On Fri, 2007-04-20 at 00:46 +0200, roland wrote:
> >>
> >>> We just quietly added an exciting feature to Workstation 6.0. I believe it 
> >>> will make WS6 a great tool for Linux kernel development. You can now debug 
> >>> kernel of Linux VM with gdb running on the Host without changing anything in 
> >>> the Guest VM. No kdb, no recompiling and no need for second machine. All you 
> >>> need is a single line in VM's configuration file.
> >> I think qemu has the exact same feature.
> > 
> > It doesn't seem to work for x86-64 there though.
> 
> Hello,
> 
> Do you mean with qemu or with VMware?  Yes, we do not support replay 
> with 64bit guests, but debug interface should just work.  Only gotcha is 
> that for 64bit guest you need another option:
> 
> debugStub.listen.guest64 = "TRUE"

Ah. That might help :)

> and then you need to attach gdb to port 8864 (*).  Unfortunately it does 
> not seem possible to build gdb which would support 16bit/32bit code 
> while using 64bit gdb on-wire format, so there are two interfaces.  And 
> if you single-step switch from 64bit mode to 32bit mode or back, you 
> also have to switch gdbs.  Yes, it is a bit unintuitive, and 
> additionally one gdb silently ignores breakpoints set up by other gdb, 
> so you need to keep breakpoints in sync between two gdbs yourself :-(
> 
> (*) If you are using gdb which has both 32bit and 64bit support, be sure 
> to issue appropriate 'set architecture xxx' before 'target remote 
> localhost:88xx' (i386:x86-64 for port 8864, i386 or i8086 for port 
> 8832).  Otherwise gdb is going to die complaining it could not parse 
> remote reply.

That too.

Thanks!

Nigel

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Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Avi Kivity]

Andi Kleen wrote:
> Xavier Bestel <xavier.bestel@free.fr> writes:
>
>   
>> On Fri, 2007-04-20 at 00:46 +0200, roland wrote:
>>
>>     
>>> We just quietly added an exciting feature to Workstation 6.0. I believe it 
>>> will make WS6 a great tool for Linux kernel development. You can now debug 
>>> kernel of Linux VM with gdb running on the Host without changing anything in 
>>> the Guest VM. No kdb, no recompiling and no need for second machine. All you 
>>> need is a single line in VM's configuration file.
>>>       
>> I think qemu has the exact same feature.
>>     
>
> It doesn't seem to work for x86-64 there though.
>   

kvm's qemu has a patch that allows qemu to be an x86_64 gdbserver (with
or without kvm).

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Nigel Cunningham]

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Hi.

On Fri, 2007-04-20 at 14:45 +0300, Avi Kivity wrote:
> Andi Kleen wrote:
> > Xavier Bestel <xavier.bestel@free.fr> writes:
> >
> >   
> >> On Fri, 2007-04-20 at 00:46 +0200, roland wrote:
> >>
> >>     
> >>> We just quietly added an exciting feature to Workstation 6.0. I believe it 
> >>> will make WS6 a great tool for Linux kernel development. You can now debug 
> >>> kernel of Linux VM with gdb running on the Host without changing anything in 
> >>> the Guest VM. No kdb, no recompiling and no need for second machine. All you 
> >>> need is a single line in VM's configuration file.
> >>>       
> >> I think qemu has the exact same feature.
> >>     
> >
> > It doesn't seem to work for x86-64 there though.
> >   
> 
> kvm's qemu has a patch that allows qemu to be an x86_64 gdbserver (with
> or without kvm).

I was meaning that vmware wasn't working, but it is now - I was trying a
64 host and client, and needed to know both the different line in the
config file and the different port number.

Regards,

Nigel

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Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Avi Kivity]

Nigel Cunningham wrote:
> Hi.
>
> On Fri, 2007-04-20 at 14:45 +0300, Avi Kivity wrote:
>   
>> Andi Kleen wrote:
>>     
>>> Xavier Bestel <xavier.bestel@free.fr> writes:
>>>
>>>   
>>>       
>>>> On Fri, 2007-04-20 at 00:46 +0200, roland wrote:
>>>>
>>>>     
>>>>         
>>>>> We just quietly added an exciting feature to Workstation 6.0. I believe it 
>>>>> will make WS6 a great tool for Linux kernel development. You can now debug 
>>>>> kernel of Linux VM with gdb running on the Host without changing anything in 
>>>>> the Guest VM. No kdb, no recompiling and no need for second machine. All you 
>>>>> need is a single line in VM's configuration file.
>>>>>       
>>>>>           
>>>> I think qemu has the exact same feature.
>>>>     
>>>>         
>>> It doesn't seem to work for x86-64 there though.
>>>   
>>>       
>> kvm's qemu has a patch that allows qemu to be an x86_64 gdbserver (with
>> or without kvm).
>>     
>
> I was meaning that vmware wasn't working, but it is now - I was trying a
> 64 host and client, and needed to know both the different line in the
> config file and the different port number.
>   

Andi was talking about qemu, not VMware, I believe.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: VMWare Workstation 6 for debugging Linux Kernel (!)

[Andi Kleen]

> Do you mean with qemu 

qemu.

-Andi