linux-kernel - Re: [PATCH v5 5/5] perf: powerpc: choose local entry point with kretprobes

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Message-Id: <20170308113952.GH11046@naverao1-tp.localdomain>
Date:   Wed, 8 Mar 2017 17:09:52 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v5 5/5] perf: powerpc: choose local entry point with
 kretprobes

On 2017/03/08 11:31AM, Masami Hiramatsu wrote:
> On Wed,  8 Mar 2017 13:56:10 +0530
> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> 
> > perf now uses an offset from _text/_stext for kretprobes if the kernel
> > supports it, rather than the actual function name. As such, let's choose
> > the LEP for powerpc ABIv2 so as to ensure the probe gets hit. Do it only
> > if the kernel supports specifying offsets with kretprobes.
> 
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
> 
> This patch is OK. And I found that most of functions in sym-handling.c
> are used only when libelf is supported. (e.g. probe-event.c itself
> is not built when we have no libelf)
> So, for the next cleanup, this file should not be compiled without
> libelf.

There are still a few functions there which work without libelf. But, I 
agree that the file has far too many #ifdefs between ABIv2 and libelf. I 
will see if I can simplify this file.

Thanks,
Naveen