guest hardware breakpoint

guest hardware breakpoint

[Michael Le]

Hi,

I'm trying to set a hardware breakpoint inside the guest using gdb. This 
doesn't seem to work. Execution just skips right over it. I've have also 
tried writing some code to set a breakpoint by directly accessing the db 
registers from the guest. This also did not cause a breakpoint to be 
generated in the guest. Is it possible to use hardware breakpoints 
inside the guest? Is there some configuration that must be set in qemu 
or in the kvm modules?

The guest vm is running linux 2.6.18.

I'm using kvm-77 with linux kernel 2.6.27. I used the kvm kernel modules 
that came with the linux kernel and not from kvm-77. I have an x86 
machine. The command I use to run the vm is the following:

../kvm/qemu-system-x86_64 main.img -m 512 -vnc :0

Thanks,
Michael Le

Re: guest hardware breakpoint

[Jan Kiszka]

Michael Le wrote:
> Hi,
> 
> I'm trying to set a hardware breakpoint inside the guest using gdb. This
> doesn't seem to work. Execution just skips right over it. I've have also
> tried writing some code to set a breakpoint by directly accessing the db
> registers from the guest. This also did not cause a breakpoint to be
> generated in the guest. Is it possible to use hardware breakpoints
> inside the guest? Is there some configuration that must be set in qemu
> or in the kvm modules?
> 
> The guest vm is running linux 2.6.18.
> 
> I'm using kvm-77 with linux kernel 2.6.27. I used the kvm kernel modules
> that came with the linux kernel and not from kvm-77. I have an x86
> machine. The command I use to run the vm is the following:
> 
> ../kvm/qemu-system-x86_64 main.img -m 512 -vnc :0

For now you need these patch queues for hw breakpoint support:

http://thread.gmane.org/gmane.comp.emulators.kvm.devel/22838
http://thread.gmane.org/gmane.comp.emulators.kvm.devel/22818

Dunno if they applied to -77, but I can provide rebases against latest
git on request.

Jan

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