Re: [RFC PATCH v3 2/3] selftests/bpf: add tests for BTF type permutation

[Eduard Zingerman <eddyz87@gmail.com>]

On Mon, 2025-10-27 at 21:54 +0800, Donglin Peng wrote:
> Verify that BTF type permutation functionality works correctly.
> 
> Cc: Eduard Zingerman <eddyz87@gmail.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Cc: Alan Maguire <alan.maguire@oracle.com>
> Cc: Song Liu <song@kernel.org>
> Signed-off-by: pengdonglin <pengdonglin@xiaomi.com>
> Signed-off-by: Donglin Peng <dolinux.peng@gmail.com>
> ---

Do we need a test case for split btf?
We probably do, as there is index arithmetic etc.

[...]

> @@ -8022,6 +8026,72 @@ static struct btf_dedup_test dedup_tests[] = {
>  		BTF_STR_SEC("\0foo\0x\0y\0foo_ptr"),
>  	},
>  },
> +{
> +	.descr = "permute: func/func_param/struct/struct_member tags",
> +	.input = {
> +		.raw_types = {
> +			/* int */
> +			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
> +			/* void f(int a1, int a2) */
> +			BTF_FUNC_PROTO_ENC(0, 2),			/* [2] */
> +				BTF_FUNC_PROTO_ARG_ENC(NAME_NTH(1), 1),
> +				BTF_FUNC_PROTO_ARG_ENC(NAME_NTH(2), 1),
> +			BTF_FUNC_ENC(NAME_NTH(3), 2),			/* [3] */
> +			/* struct t {int m1; int m2;} */
> +			BTF_STRUCT_ENC(NAME_NTH(4), 2, 8),		/* [4] */
> +				BTF_MEMBER_ENC(NAME_NTH(5), 1, 0),
> +				BTF_MEMBER_ENC(NAME_NTH(6), 1, 32),
> +			/* tag -> f: tag1, tag2, tag3 */
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 3, -1),		/* [5] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 3, -1),		/* [6] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 3, -1),		/* [7] */
> +			/* tag -> f/a2: tag1, tag2, tag3 */
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 3, 1),		/* [8] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 3, 1),		/* [9] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 3, 1),		/* [10] */
> +			/* tag -> t: tag1, tag2, tag3 */
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 4, -1),		/* [11] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 4, -1),		/* [12] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 4, -1),		/* [13] */
> +			/* tag -> t/m2: tag1, tag3 */
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 4, 1),		/* [14] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 4, 1),		/* [15] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 4, 1),		/* [16] */
> +			BTF_END_RAW,
> +		},
> +		BTF_STR_SEC("\0a1\0a2\0f\0t\0m1\0m2\0tag1\0tag2\0tag3"),
> +	},

Nit: I think that this test is a bit too large.
     Having fewer decl_tags would still test what we want to test.

> +	.expect = {
> +		.raw_types = {
> +			BTF_FUNC_ENC(NAME_NTH(3), 16),			/* [1] */
> +			BTF_STRUCT_ENC(NAME_NTH(4), 2, 8),		/* [2] */
> +				BTF_MEMBER_ENC(NAME_NTH(5), 15, 0),
> +				BTF_MEMBER_ENC(NAME_NTH(6), 15, 32),
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 1, -1),		/* [3] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 1,  1),		/* [4] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 2, -1),		/* [5] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(7), 2,  1),		/* [6] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 1, -1),		/* [7] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 1,  1),		/* [8] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 2, -1),		/* [9] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(8), 2,  1),		/* [10] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 1, -1),		/* [11] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 1,  1),		/* [12] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 2, -1),		/* [13] */
> +			BTF_DECL_TAG_ENC(NAME_NTH(9), 2,  1),		/* [14] */
> +			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [15] */
> +			BTF_FUNC_PROTO_ENC(0, 2),			/* [16] */
> +				BTF_FUNC_PROTO_ARG_ENC(NAME_NTH(1), 15),
> +				BTF_FUNC_PROTO_ARG_ENC(NAME_NTH(2), 15),
> +			BTF_END_RAW,
> +		},
> +		BTF_STR_SEC("\0a1\0a2\0f\0t\0m1\0m2\0tag1\0tag2\0tag3"),
> +	},
> +	.permute = true,
> +	.permute_opts = {
> +		.ids = permute_ids_sort_by_kind_name,
> +	},
> +},
>  };

[...]