bpf: Add selftest for BPF_ENABLE_STATS

Add test for BPF_ENABLE_STATS, which should enable run_time_ns stats.

~/selftests/bpf# ./test_progs -t enable_stats  -v
test_enable_stats:PASS:skel_open_and_load 0 nsec
test_enable_stats:PASS:get_stats_fd 0 nsec
test_enable_stats:PASS:attach_raw_tp 0 nsec
test_enable_stats:PASS:get_prog_info 0 nsec
test_enable_stats:PASS:check_stats_enabled 0 nsec
test_enable_stats:PASS:check_run_cnt_valid 0 nsec
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200430071506.1408910-4-songliubraving@fb.com

tools/testing/selftests/bpf/prog_tests/enable_stats.c

+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "test_enable_stats.skel.h"
+
+void test_enable_stats(void)
+{
+	struct test_enable_stats *skel;
+	int stats_fd, err, prog_fd;
+	struct bpf_prog_info info;
+	__u32 info_len = sizeof(info);
+	int duration = 0;
+
+	skel = test_enable_stats__open_and_load();
+	if (CHECK(!skel, "skel_open_and_load", "skeleton open/load failed\n"))
+		return;
+
+	stats_fd = bpf_enable_stats(BPF_STATS_RUN_TIME);
+	if (CHECK(stats_fd < 0, "get_stats_fd", "failed %d\n", errno)) {
+		test_enable_stats__destroy(skel);
+		return;
+	}
+
+	err = test_enable_stats__attach(skel);
+	if (CHECK(err, "attach_raw_tp", "err %d\n", err))
+		goto cleanup;
+
+	test_enable_stats__detach(skel);
+
+	prog_fd = bpf_program__fd(skel->progs.test_enable_stats);
+	memset(&info, 0, info_len);
+	err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
+	if (CHECK(err, "get_prog_info",
+		  "failed to get bpf_prog_info for fd %d\n", prog_fd))
+		goto cleanup;
+	if (CHECK(info.run_time_ns == 0, "check_stats_enabled",
+		  "failed to enable run_time_ns stats\n"))
+		goto cleanup;
+
+	CHECK(info.run_cnt != skel->bss->count, "check_run_cnt_valid",
+	      "invalid run_cnt stats\n");
+
+cleanup:
+	test_enable_stats__destroy(skel);
+	close(stats_fd);
+}

tools/testing/selftests/bpf/progs/test_enable_stats.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include <linux/types.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+__u64 count = 0;
+
+SEC("raw_tracepoint/sys_enter")
+int test_enable_stats(void *ctx)
+{
+	count += 1;
+	return 0;
+}