perf test: Check environment before start real BPF test

Copying perf to old kernel system results:

  # perf test bpf
  37: Test BPF filter                                          :
  37.1: Test basic BPF filtering                               : FAILED!
  37.2: Test BPF prologue generation                           : Skip

However, in case when kernel doesn't support a test case it should
return 'Skip', 'FAILED!' should be reserved for kernel tests for when
the kernel supports a feature that then fails to work as advertised.

This patch checks environment before real testcase.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1453715801-7732-7-git-send-email-wangnan0@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/bpf.c

 #include <stdio.h>
 #include <sys/epoll.h>
+#include <util/util.h>
 #include <util/bpf-loader.h>
 #include <util/evlist.h>
+#include <linux/bpf.h>
+#include <linux/filter.h>
+#include <bpf/bpf.h>
 #include "tests.h"
 #include "llvm.h"
 #include "debug.h"
@@ -243,6 +247,36 @@ const char *test__bpf_subtest_get_desc(int i)
 	return bpf_testcase_table[i].desc;
 }
 
+static int check_env(void)
+{
+	int err;
+	unsigned int kver_int;
+	char license[] = "GPL";
+
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 1),
+		BPF_EXIT_INSN(),
+	};
+
+	err = fetch_kernel_version(&kver_int, NULL, 0);
+	if (err) {
+		pr_debug("Unable to get kernel version\n");
+		return err;
+	}
+
+	err = bpf_load_program(BPF_PROG_TYPE_KPROBE, insns,
+			       sizeof(insns) / sizeof(insns[0]),
+			       license, kver_int, NULL, 0);
+	if (err < 0) {
+		pr_err("Missing basic BPF support, skip this test: %s\n",
+		       strerror(errno));
+		return err;
+	}
+	close(err);
+
+	return 0;
+}
+
 int test__bpf(int i)
 {
 	int err;
@@ -255,6 +289,9 @@ int test__bpf(int i)
 		return TEST_SKIP;
 	}
 
+	if (check_env())
+		return TEST_SKIP;
+
 	err = __test__bpf(i);
 	return err;
 }