Re: [Qemu-devel] Re: software breakpoints disappearing/reappearing in KVM/qemu

[Avi Kivity <avi@redhat.com>]

On 04/10/2011 05:23 PM, Jan Kiszka wrote:
> On 2011-04-10 16:01, Avi Kivity wrote:
> >  On 04/08/2011 11:52 PM, Jan Kiszka wrote:
> >>  QEMU's gdbstub in KVM mode is simply not designed to account for guests
> >>  swapping out code pages that contain breakpoints. Due to the fact that
> >>  the Linux kernel does not do these weird things to its own code,
> >
> >  It actually happily patches its own code at certain circumstances.  If
> >  you debug early boot or suspend/resume or cpu hotplug you're likely to
> >  encounter them.
>
> Yes, it patches (alternates, jump_labels, mcount etc.), but it doesn't
> swap or move code pages. At least so far.
>

Try using modules (though that's different - the virtual addresses will 
change too).  Or debugging a mixed kernel/user workload.

> If you need to break at such locations, there are still hardware
> breakpoints, though only 4.

Right.

-- 
error compiling committee.c: too many arguments to function