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Re: [PATCH -tip 0/6 V4] tracing: kprobe-based event tracer
- From: Ingo Molnar <mingo at elte dot hu>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: 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>, Jim Keniston <jkenisto at us dot ibm dot com>, 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, 3 Apr 2009 16:23:25 +0200
- 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>
* 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?
Ingo