> selftests/bpf: Validate that btf__permute transfer works
>
> Add coverage for btf__permute() transfer mode, including type-ID
> remapping and LOCSEC record ordering in the resulting split BTF.
>
> Verify string handling for both cases: a string used only by transferred
> types is removed from the base BTF and deduplicated locally in the split
> BTF, while a string also referenced by a retained base type remains a
> base-string reference.
>
> Signed-off-by: Alan Maguire <[email protected]>
This isn't a bug, but would it be worth a sentence in the changelog for
the new permute_layout subtest too, so the layout-section coverage is
visible without reading the diff?
The commit message describes the transfer mode coverage in detail, but the
patch also adds test_permute_layout() which builds a BTF with .add_layout
= true, permutes it with a transfer, and re-parses btf__raw_data() to
verify the layout/string section offsets stayed consistent.
> diff --git a/tools/testing/selftests/bpf/prog_tests/btf_permute.c
> b/tools/testing/selftests/bpf/prog_tests/btf_permute.c
> index 04ade5ad77ac..ef75fd71df96 100644
> --- a/tools/testing/selftests/bpf/prog_tests/btf_permute.c
> +++ b/tools/testing/selftests/bpf/prog_tests/btf_permute.c
[ ... ]
> +/* Permuting BTF with a layout section must keep section offsets in sync. */
> +static void test_permute_layout(void)
> +{
> + LIBBPF_OPTS(btf_new_opts, opts, .add_layout = true);
> + LIBBPF_OPTS(btf_permute_opts, permute_opts);
> + struct btf *btf, *parsed, *transfer_btf = NULL;
> + const void *raw;
> + __u32 raw_sz;
> + __u32 permute_ids[] = { 0, 1, BTF_PERMUTE_ID_TRANSFER | 2 };
> + int err;
> +
> + btf = btf__new_empty_opts(&opts);
> + if (!ASSERT_OK_PTR(btf, "empty_layout_btf"))
> + return;
> +
> + btf__add_int(btf, "int", 4, BTF_INT_SIGNED);
> + btf__add_ptr(btf, 1);
> + permute_opts.transfer_btf = &transfer_btf;
> + err = btf__permute(btf, permute_ids, ARRAY_SIZE(permute_ids),
> &permute_opts);
> + if (!ASSERT_OK(err, "btf__permute_layout"))
> + goto cleanup;
> +
> + raw = btf__raw_data(btf, &raw_sz);
> + parsed = btf__new(raw, raw_sz);
> + if (!ASSERT_OK_PTR(parsed, "parse_permuted_layout"))
> + goto cleanup;
> + btf__free(parsed);
> +cleanup:
> + btf__free(transfer_btf);
> + btf__free(btf);
> +}
> +
> void test_btf_permute(void)
> {
> if (test__start_subtest("permute_base"))
> test_permute_base();
> if (test__start_subtest("permute_split"))
> test_permute_split();
> + if (test__start_subtest("permute_transfer"))
> + test_permute_transfer();
> + if (test__start_subtest("permute_layout"))
> + test_permute_layout();
> }
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/33537080133
