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Subject: Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)
From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@redhat.com>
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Date: Mon, 18 Jan 2010 13:14:17 +0100
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On Mon, 2010-01-18 at 14:09 +0200, Avi Kivity wrote:
> On 01/18/2010 02:06 PM, Peter Zijlstra wrote:
> > On Mon, 2010-01-18 at 14:01 +0200, Avi Kivity wrote:
> >    
> >> Maybe you place no value on uprobes.  But people who debug userspace
> >> likely will see a reason.
> >>      
> > I do see value in uprobes, I just don't like it mucking about with the
> > address space. Nor does it appear required.
> >    
> 
> Well, the alternatives are very unappealing.  Emulation and 
> single-stepping are going to be very slow compared to a couple of jumps.

With CPL2 or RPL on user segments the protection issue seems to be
manageable for running the instructions from kernel space.