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

[Yonghong Song <yhs@fb.com>]

On 7/31/21 7:32 AM, Hengqi Chen wrote:
> 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;

Should we do `btf__free(vmlinux_btf)` before `return`?
 From implementation perspective, maybe use "goto" so we have one
place to do `btf__free(vmlinux_btf)`.

> +
> +	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);
> +}
>