linux-kernel - [PATCH v3] tools: perf: fix linker error when libelf config is disabled

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Date:   Wed,  4 Jan 2017 17:30:02 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        Stephane Eranian <eranian@...gle.com>
Subject: [PATCH v3] tools: perf: fix linker error when libelf config is disabled

When libelf is disabled in the configuration, we get the following
linker error:
  LINK     libperf-jvmti.so
  ld: cannot find -lelf
  Makefile.perf:515: recipe for target 'libperf-jvmti.so' failed

Jiri pointed out that both librt and libelf are not really required. So
this patch fixes the linker error by getting rid of unwanted libraries
in the linker stage.

Fixes: 209045adc2bb ("perf tools: add JVMTI agent library")
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 tools/perf/Makefile.perf | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

v2->v3:
	- Corrected the original commit under "Fixes:" tag that
	  introduced the libraries initially
v1->v2:
	- Dropped libelf and librt as they are not required

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 8fc24824705e..9e4a7ea84637 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -512,7 +512,7 @@ $(LIBJVMTI_IN): FORCE
 	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=jvmti obj=jvmti

 $(OUTPUT)$(LIBJVMTI): $(LIBJVMTI_IN)
-	$(QUIET_LINK)$(CC) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ $< -lelf -lrt
+	$(QUIET_LINK)$(CC) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ $<
 endif

 $(patsubst perf-%,%.o,$(PROGRAMS)): $(wildcard */*.h)
--
2.7.4