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

[Ingo Molnar <mingo@elte.hu>]

* 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