Re: [PATCH bpf-next 2/2] selftests/bpf: Add a test where map key_type_id with decl_tag type

[Eduard Zingerman <eddyz87@gmail.com>]

On Sat, 2023-05-27 at 15:31 -0700, Yonghong Song wrote:
> Add a selftest where map creation key type_id is a decl_tag
> pointing to a struct. Without previous patch, a kernel warning will
> appear similar to the one in the previous patch. With the previous
> patch, the kernel warning is silenced.

Looks good to me with a nitpick:
commit message says "map creation key type_id is a decl_tag",
but test case uses ".key_type_id = 1" which is INT
and ".value_type_id = 3" which is DECL_TAG.

syscall.c:map_check_btf.c applies the same check both for key and value,
maybe make two tests?

> 
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
>  tools/testing/selftests/bpf/prog_tests/btf.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
> index 210d643fda6c..69521e1dc330 100644
> --- a/tools/testing/selftests/bpf/prog_tests/btf.c
> +++ b/tools/testing/selftests/bpf/prog_tests/btf.c
> @@ -3990,6 +3990,26 @@ static struct btf_raw_test raw_tests[] = {
>  	.btf_load_err = true,
>  	.err_str = "Invalid arg#1",
>  },
> +{
> +	.descr = "decl_tag test #18, struct member, decl_tag as the value type",
> +	.raw_types = {
> +		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
> +		BTF_STRUCT_ENC(0, 2, 8),			/* [2] */
> +		BTF_MEMBER_ENC(NAME_TBD, 1, 0),
> +		BTF_MEMBER_ENC(NAME_TBD, 1, 32),
> +		BTF_DECL_TAG_ENC(NAME_TBD, 2, -1),		/* [3] */
> +		BTF_END_RAW,
> +	},
> +	BTF_STR_SEC("\0m1\0m2\0tag"),
> +	.map_type = BPF_MAP_TYPE_ARRAY,
> +	.map_name = "tag_type_check_btf",
> +	.key_size = sizeof(int),
> +	.value_size = 8,
> +	.key_type_id = 1,
> +	.value_type_id = 3,
> +	.max_entries = 1,
> +	.map_create_err = true,
> +},
>  {
>  	.descr = "type_tag test #1",
>  	.raw_types = {