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Re: [PATCH -tip 0/6 V4] tracing: kprobe-based event tracer
- From: Jim Keniston <jkenisto at us dot ibm dot com>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, Avi Kivity <avi at redhat dot com>, "H. Peter Anvin" <hpa at zytor dot com>, Frederic Weisbecker <fweisbec at gmail dot com>, Steven Rostedt <rostedt at goodmis dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Andrew Morton <akpm at linux-foundation dot org>, Andi Kleen <andi at firstfloor dot org>, kvm at vger dot kernel dot org, systemtap-ml <systemtap at sources dot redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>, Vegard Nossum <vegard dot nossum at gmail dot com>
- Date: Fri, 03 Apr 2009 10:59:55 -0700
- Subject: Re: [PATCH -tip 0/6 V4] tracing: kprobe-based event tracer
- References: <49D4F4B5.9040107@redhat.com> <20090403112639.GC31399@elte.hu> <49D5F80B.7000305@redhat.com> <49D61B56.9020408@redhat.com> <20090403142325.GA14932@elte.hu> <49D63F70.7040308@redhat.com>
On Fri, 2009-04-03 at 12:55 -0400, Masami Hiramatsu wrote:
> Ingo Molnar wrote:
> > * Masami Hiramatsu <mhiramat@redhat.com> wrote:
> >
> >> Hmm, I'd like to know actually kvm aims to emulate all kinds of
> >> instructions. If so, I might find some bugs in x86_emulate.c.
> >> However, I don't know all bugs. To find all of them, we have to
> >> port x86_emulate.c to user-space, decode binaries with it, and
> >> compare its output with another decoder, as Jim had done with
> >> insn.c.
> >>
> >> https://www.redhat.com/archives/utrace-devel/2009-March/msg00031.html
> >
> > btw., i'd suggest we put a build time check for this into the kernel
> > version as well. For example to decode the vmlinux via objdump, run
> > it through your decoder as well and compare the results. Put under a
> > CONFIG_DEBUG_X86_DECODER_TEST kind of (deault-off) build-time
> > self-test.
> >
> > This would ensure that the kernel we are running is fully supported
> > by the decoder - even as GCC/GAS starts using new instructions, etc.
> >
> > How does this sound to you?
>
> Thanks! That is a good idea.
> Jim, would you think you can port your script into kernel tree?
...
I'd be happy to do what's needed to make it happen, and maintain it in
the face of x86 changes. The script itself is practically nothing (~100
lines of awk and C), but what I don't know about the kernel build is a
lot, so I'd need some help from a kernel-build expert.
Jim