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

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Date:	Thu, 24 Sep 2015 18:07:44 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Stephane Eranian <eranian@...gle.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 08:32:12AM -0700, Stephane Eranian wrote:
> 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?

sample_reg_masks is touched via parse-regs-options.c as well
and perf_regs.o depends on CONFIG_PERF_REGS

so with keeping the weak deffinition, how about attached change

jirka


---
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 142eeb341b29..19c8fd22fbe3 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1082,9 +1082,11 @@ struct option __record_options[] = {
 		    "sample transaction flags (special events only)"),
 	OPT_BOOLEAN(0, "per-thread", &record.opts.target.per_thread,
 		    "use per-thread mmaps"),
+#ifdef HAVE_PERF_REGS_SUPPORT
 	OPT_CALLBACK_OPTARG('I', "intr-regs", &record.opts.sample_intr_regs, NULL, "any register",
 		    "sample selected machine registers on interrupt,"
 		    " use -I ? to list register names", parse_regs),
+#endif
 	OPT_BOOLEAN(0, "running-time", &record.opts.running_time,
 		    "Record running/enabled time of read (:S) events"),
 	OPT_CALLBACK('k', "clockid", &record.opts,
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 4bc7a9ab45b1..93c6371405a3 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -104,7 +104,7 @@ libperf-$(CONFIG_LIBBABELTRACE) += data-convert-bt.o
 
 libperf-y += scripting-engines/
 
-libperf-$(CONFIG_PERF_REGS) += perf_regs.o
+libperf-y += perf_regs.o
 libperf-$(CONFIG_ZLIB) += zlib.o
 libperf-$(CONFIG_LZMA) += lzma.o
 
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