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

Ingo Molnar
2009-04-01T17:48:31Z

* Masami Hiramatsu <mhiramat@redhat.com> wrote:

> >> 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
> >
> > looks cool. Needs to be put somewhere in arch/x86/lib/, provided
> > as a generic facility, with a Kconfig variable that says that
> > the architecture supports it and then the kprobes-tracer could
> > make immediate use of it, right?
>
> Yeah, I'd rather add a safety checker in kprobes-x86 itself,
> because sometimes it has to fixup instructions modified by
> previous kprobes.

Oh, certainly! I didnt know how much you wanted to check things on
the kprobes side but by all means please add it there too, it will
be for the better.

A clear and actionable debug message to the syslog is important for
the case where the decoder rejects an action. This is especially
important for the kprobes side - we dont want silent breakage of
tools.

Ingo