perf tools: Do not attempt to run perf-read-vdso32 if it wasn't built

popen() causes an error message to print if perf-read-vdso32 does not
run.  Avoid that by not trying to run it if it was not built.  Ditto
perf-read-vdsox32.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1414061124-26830-17-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/config/Makefile

@@ -627,7 +627,9 @@ endif
 ifeq (${IS_64_BIT}, 1)
   ifndef NO_PERF_READ_VDSO32
     $(call feature_check,compile-32)
-    ifneq ($(feature-compile-32), 1)
+    ifeq ($(feature-compile-32), 1)
+      CFLAGS += -DHAVE_PERF_READ_VDSO32
+    else
       NO_PERF_READ_VDSO32 := 1
     endif
   endif
@@ -636,7 +638,9 @@ ifeq (${IS_64_BIT}, 1)
   endif
   ifndef NO_PERF_READ_VDSOX32
     $(call feature_check,compile-x32)
-    ifneq ($(feature-compile-x32), 1)
+    ifeq ($(feature-compile-x32), 1)
+      CFLAGS += -DHAVE_PERF_READ_VDSOX32
+    else
       NO_PERF_READ_VDSOX32 := 1
     endif
   endif

tools/perf/util/vdso.c

@@ -255,6 +255,16 @@ static int vdso__dso_findnew_compat(struct machine *machine,
 	enum dso_type dso_type;
 
 	dso_type = machine__thread_dso_type(machine, thread);
+
+#ifndef HAVE_PERF_READ_VDSO32
+	if (dso_type == DSO__TYPE_32BIT)
+		return 0;
+#endif
+#ifndef HAVE_PERF_READ_VDSOX32
+	if (dso_type == DSO__TYPE_X32BIT)
+		return 0;
+#endif
+
 	switch (dso_type) {
 	case DSO__TYPE_32BIT:
 		*dso = vdso__findnew_compat(machine, &vdso_info->vdso32);