linux-kernel - Re: [PATCH 0/2] powerpc: kretprobe updates

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Message-Id: <20170220094626.GA12165@naverao1-tp.localdomain>
Date:   Mon, 20 Feb 2017 15:16:26 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 0/2] powerpc: kretprobe updates

On 2017/02/17 05:42PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Feb 17, 2017 at 07:44:33PM +0900, Masami Hiramatsu escreveu:
> > On Thu, 16 Feb 2017 13:47:37 +0530
> > "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> > 
> > > I am posting the powerpc bits in the same thread so as to keep these
> > > changes together. I am not sure how this should be taken upstream as
> > > there are atleast three different trees involved: one for the core
> > > kprobes infrastructure, one for powerpc and one for perf.
> 
> > Hmm, could you make these (and other related) patches and
> > other series in one series? Or wait for the other series
> > are merged correctly.
> 
> Well, patches like these should be done in a way that the tooling parts
> can deal with kernels with or without the kernel changes, so that older
> tools work with new kernels and new tools work with older kernels.
> 
> "work" as in the previous behaviour is kept when a new tool deals with
> an older kernel and an older tool would warn the user that what it needs
> is not present in that kernel.
> 
> Is this the case? I just looked briefly at the patch commit logs.

Thanks, that makes sense.

All the kernel patches here can go in as they are about removing the 
restrictions around use of kretprobes with kprobe_event, except for the 
first patch which hardens use of kretprobes in general by validating 
addresses. None of that should cause issues with the existing tools.

> 
> If it is, then I can pick the tool ones, and the others can be submitted
> to the relevant trees, at some point all will be in, kernels eventually
> gets updated everywhere, ditto for the tooling, all gets well.

Older perf tools with newer kernels will be fine. However, with the 
current perf patches, newer perf will fail with older kernels. I will 
redo the perf patches to address this. So, please don't merge the perf 
bits in this series.


Regards,
Naveen