linux-kernel - Re: perf jvmti: unconditionally links against -lelf

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Message-ID: <1491997955.4510.42.camel@synopsys.com>
Date:   Wed, 12 Apr 2017 11:52:36 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     "jolsa@...hat.com" <jolsa@...hat.com>
CC:     "jolsa@...nel.org" <jolsa@...nel.org>,
        "acme@...hat.com" <acme@...hat.com>,
        "a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "davidcc@...gle.com" <davidcc@...gle.com>
Subject: Re: perf jvmti: unconditionally links against -lelf

Hi Jiri,

On Wed, 2017-04-12 at 12:19 +0200, Jiri Olsa wrote:
> On Wed, Apr 12, 2017 at 09:58:26AM +0000, Alexey Brodkin wrote:
> > 
> > Hi Jiri,
> > 
> > Just tried to cross-compile perf with pretty bare-minimal toolchain
> > which has no libelf installed for the target (for the record I used
> > SNPS ARC pre-built arc-2016.09 tools) like that:
> > --------------->8------------
> > make NO_LIBELF=1
> > --------------->8------------
> > 
> > And got the following build failure:
> > --------------->8------------
> >   LINK     libperf-jvmti.so
> > .../2016.09-uclibc-archs/bin/../lib/gcc/arc-snps-linux-uclibc/6.2.1/../../../../arc-snps-linux-uclibc/bin/ld: cannot find -lelf
> > --------------->8------------
> > 
> > First I was surprised because I intentionally disabled usage of libelf
> > but after some grepping figured out jvmti is linked against libelf
> > regardless any settings, see:
> > --------------->8------------
> > $(OUTPUT)$(LIBJVMTI): $(LIBJVMTI_IN)
> >        $(QUIET_LINK)$(CC) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ $< -lelf -lrt
> > endif
> > --------------->8------------
> > 
> > This comes from commit d4dfdf00d43e ("perf jvmti: Plug compilation into perf build").
> > 
> > I'm not really sure what could be the best solution to the problem I see.
> > If libelf is a real must for jvmti then probably we may force set NO_JVMTI=1
> > if NO_LIBELF=1 is passed on the command line.
> > 
> > At least the following builds perf for me without issues:
> > --------------->8------------
> > make NO_LIBELF=1 NO_JVMTI=1
> > --------------->8------------
> 
> hi,
> incidently, David just posted patch for this ;-)

So good to know somebody has already fixed my problem :)
Thanks for letting me know!

-Alexey