linux-kernel - Re: [PATCH] perf record: Limit --intr-regs to platforms supporting PERF

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Message-ID: <CABPqkBSaxTm6-7x7VpwRtw6aS2qmHup_VsWK0VYFJVwZSMG10w@mail.gmail.com>
Date:	Thu, 24 Sep 2015 08:32:12 -0700
From:	Stephane Eranian <eranian@...gle.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...hat.com" <mingo@...hat.com>
Subject: Re: [PATCH] perf record: Limit --intr-regs to platforms supporting PERF_REGS

On Thu, Sep 24, 2015 at 5:57 AM, Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Thu, Sep 24, 2015 at 05:41:58PM +0530, Naveen N. Rao wrote:
> > perf build currently fails on powerpc:
> >
> >   LINK     perf
> > libperf.a(libperf-in.o):(.toc+0x120): undefined reference to
> > `sample_reg_masks'
> > libperf.a(libperf-in.o):(.toc+0x130): undefined reference to
> > `sample_reg_masks'
> > collect2: error: ld returned 1 exit status
> > make[1]: *** [perf] Error 1
> > make: *** [all] Error 2
> >
> > This is due to parse-regs-options.c using sample_reg_masks, which is
> > defined only with CONFIG_PERF_REGS.
> >
> > In addition, perf record -I is only useful if the arch supports
> > PERF_REGS. Hence, let's expose -I conditionally.
> >
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
>
> hum, I wonder why we have sample_reg_masks defined as weak in util/perf_regs.c
> which is also built only via CONFIG_PERF_REGS
>
> I wonder we could get rid of the weak definition via attached patch, Stephane?
>
But the whole point of having it weak is to avoid this error scenario
on any arch without support
and avoid ugly #ifdef HAVE_ in generic files.

if perf_regs.c is compiled on PPC, then why do we get the undefined?

>
>
> anyway this looks ok
>
> Acked-by: Jiri Olsa <jolsa@...nel.org>
>
> thanks,
> jirka
>
>
> ---
> diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
> index ff63649fa9ac..e5627b3d1bb8 100644
> --- a/tools/perf/arch/x86/util/Build
> +++ b/tools/perf/arch/x86/util/Build
> @@ -2,7 +2,7 @@ libperf-y += header.o
>  libperf-y += tsc.o
>  libperf-y += pmu.o
>  libperf-y += kvm-stat.o
> -libperf-y += perf_regs.o
> +libperf-$(CONFIG_PERF_REGS) += perf_regs.o
>
>  libperf-$(CONFIG_DWARF) += dwarf-regs.o
>
> diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
> index 885e8ac83997..43168fb0d9a2 100644
> --- a/tools/perf/util/perf_regs.c
> +++ b/tools/perf/util/perf_regs.c
> @@ -2,10 +2,6 @@
>  #include "perf_regs.h"
>  #include "event.h"
>
> -const struct sample_reg __weak sample_reg_masks[] = {
> -       SMPL_REG_END
> -};
> -
>  int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
>  {
>         int i, idx = 0;
--
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