selftests/bpf: Add verif_stats test

verified_insns field was added to response of bpf_obj_get_info_by_fd
call on a prog. Confirm that it's being populated by loading a simple
program and asking for its info.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211020074818.1017682-3-davemarchevsky@fb.com

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <test_progs.h>
+
+#include "trace_vprintk.lskel.h"
+
+void test_verif_stats(void)
+{
+	__u32 len = sizeof(struct bpf_prog_info);
+	struct bpf_prog_info info = {};
+	struct trace_vprintk *skel;
+	int err;
+
+	skel = trace_vprintk__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "trace_vprintk__open_and_load"))
+		goto cleanup;
+
+	err = bpf_obj_get_info_by_fd(skel->progs.sys_enter.prog_fd, &info, &len);
+	if (!ASSERT_OK(err, "bpf_obj_get_info_by_fd"))
+		goto cleanup;
+
+	if (!ASSERT_GT(info.verified_insns, 0, "verified_insns"))
+		goto cleanup;
+
+cleanup:
+	trace_vprintk__destroy(skel);
+}