Re: [PATCH -tip 0/4 V3] tracing: kprobe-based event tracer

Andi Kleen
2009-04-01T22:14:16Z

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.