perf tools: Add file-handle feature test

The file handle (FHANDLE) support is configurable so some systems might not
have it.  So add a config feature item to check it on build time so that we
don't add the cgroup tracking feature based on that.

Committer notes:

Had to make the test use the same construct as its later use in
synthetic-events.c, in the next patch in this series. i.e. make it be:

	struct {
		struct file_handle fh;
		uint64_t cgroup_id;
	} handle;

To cope with:

    CC       /tmp/build/perf/util/cloexec.o
  util/synthetic-events.c:428:22: error: field 'fh' with   CC       /tmp/build/perf/util/call-path.o
  variable sized type 'struct file_handle' not at the end of a struct or class is a GNU
        extension [-Werror,-Wgnu-variable-sized-type-not-at-end]
                  struct file_handle fh;
                                     ^
  1 error generated.

Deal with this at some point, i.e. investigate if the right thing is to
remove that -Wgnu-variable-sized-type-not-at-end from our CFLAGS, for
now do the test the same way as it is used looks more sensible.
Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200402015249.3800462-1-namhyung@kernel.org
[ split from a larger patch, removed blank line at EOF ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/build/Makefile.feature

@@ -72,7 +72,8 @@ FEATURE_TESTS_BASIC :=                  \
         setns				\
         libaio				\
         libzstd				\
-        disassembler-four-args
+        disassembler-four-args		\
+        file-handle
 
 # FEATURE_TESTS_BASIC + FEATURE_TESTS_EXTRA is the complete list
 # of all feature tests

tools/build/feature/Makefile

@@ -67,7 +67,8 @@ FILES=                                          \
          test-llvm.bin				\
          test-llvm-version.bin			\
          test-libaio.bin			\
-         test-libzstd.bin
+         test-libzstd.bin			\
+         test-file-handle.bin
 
 FILES := $(addprefix $(OUTPUT),$(FILES))
 
@@ -321,6 +322,9 @@ $(OUTPUT)test-libaio.bin:
 $(OUTPUT)test-libzstd.bin:
 	$(BUILD) -lzstd
 
+$(OUTPUT)test-file-handle.bin:
+	$(BUILD)
+
 ###############################
 
 clean:

tools/build/feature/test-file-handle.c

+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <inttypes.h>
+
+int main(void)
+{
+	struct {
+		struct file_handle fh;
+		uint64_t cgroup_id;
+	} handle;
+	int mount_id;
+
+	name_to_handle_at(AT_FDCWD, "/", &handle.fh, &mount_id, 0);
+	return 0;
+}

tools/perf/Makefile.config

@@ -348,6 +348,10 @@ ifeq ($(feature-gettid), 1)
   CFLAGS += -DHAVE_GETTID
 endif
 
+ifeq ($(feature-file-handle), 1)
+  CFLAGS += -DHAVE_FILE_HANDLE
+endif
+
 ifdef NO_LIBELF
   NO_DWARF := 1
   NO_DEMANGLE := 1