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Re: [PATCH -tip 0/4 V3] tracing: kprobe-based event tracer
- From: Andi Kleen <andi at firstfloor dot org>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: Andi Kleen <andi at firstfloor dot org>, Ingo Molnar <mingo at elte dot hu>, Arnaldo Carvalho de Melo <acme at redhat dot com>, Steven Rostedt <rostedt at goodmis dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Frederic Weisbecker <fweisbec at gmail dot com>, Linux Kernel Mailing List <linux-kernel at vger dot kernel dot org>, systemtap-ml <systemtap at sources dot redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, Jim Keniston <jkenisto at us dot ibm dot com>
- Date: Thu, 2 Apr 2009 00:15:40 +0200
- Subject: Re: [PATCH -tip 0/4 V3] tracing: kprobe-based event tracer
- References: <49CC08A2.5030602@redhat.com> <20090401133654.GB18677@elte.hu> <49D37584.50208@redhat.com> <873acsm8qp.fsf@basil.nowhere.org> <49D3D3B4.4060702@redhat.com>
On Wed, Apr 01, 2009 at 04:51:00PM -0400, Masami Hiramatsu wrote:
> Andi Kleen wrote:
> > Masami Hiramatsu <mhiramat@redhat.com> writes:
> >> I agreed. Fortunately, Jim Keniston and I wrote an x86 instruction
> >> decoder :-) which has been made originally for uprobe andd kprobes
> >> jump-optimizer.
> >>
> >> https://www.redhat.com/archives/utrace-devel/2009-March/msg00031.html
> >
> > An alternative would be to adapt the x86 interpreter in KVM.
> > I thought for some time that that one should be available in
> > a more generic form in a library.
>
> As far as I can see, KVM's instruction emulator is incomplete
That's fine for you -- you only care about a subset of instructions
anyways, don't you?
> (it doesn't cover all instructions...) and aims to emulate
> instructions, not to analyze (so I couldn't relay on it).
You can use it to analyze, just plug in the right callbacks that
do nothing. I looked at it some time ago for doing instruction
length checking for some application, but that application
then disappeared. The main obstacle with making it a library
is that some KVM specific dependencies have crept in that would
need to be abstracted again, but I don't think it would need a lot of
effort,
-Andi
--
ak@linux.intel.com -- Speaking for myself only.