[PATCH] selftests/bpf: Test btf__load_vmlinux_btf/btf__load_module_btf APIs

[Hengqi Chen <hengqi.chen@gmail.com>]

Add test for btf__load_vmlinux_btf/btf__load_module_btf APIs. It first
checks that if btrfs module BTF exists, if yes, load module BTF and
check symbol existence.

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 .../selftests/bpf/prog_tests/btf_module.c     | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/btf_module.c

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_module.c b/tools/testing/selftests/bpf/prog_tests/btf_module.c
new file mode 100644
index 000000000000..cad1314e3356
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/btf_module.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Hengqi Chen */
+
+#include <test_progs.h>
+#include <bpf/btf.h>
+
+static const char *module_path = "/sys/kernel/btf/btrfs";
+static const char *module_name = "btrfs";
+
+void test_btf_module()
+{
+	struct btf *vmlinux_btf, *module_btf;
+	__s32 type_id;
+
+	if (access(module_path, F_OK))
+		return;
+
+	vmlinux_btf = btf__load_vmlinux_btf();
+	if (!ASSERT_OK_PTR(vmlinux_btf, "could not load vmlinux BTF"))
+		return;
+
+	module_btf = btf__load_module_btf(module_name, vmlinux_btf);
+	if (!ASSERT_OK_PTR(module_btf, "could not load module BTF"))
+		return;
+
+	type_id = btf__find_by_name(module_btf, "btrfs_file_open");
+	ASSERT_GT(type_id, 0, "func btrfs_file_open not found");
+
+	btf__free(module_btf);
+	btf__free(vmlinux_btf);
+}
-- 
2.30.2