cilium/cilium · error

loading marshaled BTF: %w

Error message

loading marshaled BTF: %w

What it means

marshalSorted re-loads the bytes it just marshaled via btf.LoadSpecFromReader to obtain a spec whose types it can sort. If the freshly marshaled BTF cannot be parsed back, the error is wrapped with this message. Since the input bytes come straight from bb.Marshal, a failure here indicates the produced blob is malformed (or a library bug).

Source

Thrown at tools/dpgen/util.go:266

	// declaration, so it needs to be queryable by name in the resulting BTF blob.
	if added != nil {
		added.Insert(name)
	}
	return nil
}

// marshalSorted marshals the BTF types in the builder into a byte slice,
// ensuring the types are sorted by name in the resulting BTF blob for
// more deterministic output.
func marshalSorted(bb *btf.Builder) ([]byte, error) {
	b, err := bb.Marshal(nil, nil)
	if err != nil {
		return nil, fmt.Errorf("marshaling BTF before sort: %w", err)
	}

	spec, err := btf.LoadSpecFromReader(bytes.NewReader(b))
	if err != nil {
		return nil, fmt.Errorf("loading marshaled BTF: %w", err)
	}

	var types []btf.Type
	for t, err := range spec.All() {
		if err != nil {
			return nil, fmt.Errorf("iterating BTF types: %w", err)
		}

		// Can't sort anonymous types. These are typically referred to by named
		// types, so they will be included by dependency when adding named types to
		// the builder.
		if t.TypeName() == "" {
			continue
		}

		types = append(types, t)
	}

View on GitHub (pinned to ac7b90affa)

Solutions

1. Verify the cilium/ebpf version is consistent (no mixed versions of vendor packages).
2. Check the wrapped LoadSpecFromReader error for which BTF feature/offset failed.
3. Try upgrading cilium/ebpf so marshal and parse support the same BTF features.
4. As a workaround, dump the marshaled bytes with bpftool btf to inspect the blob.

b, err := marshalSorted(bb)
if err != nil {
    if strings.Contains(err.Error(), "loading marshaled BTF") {
        log.Printf("BTF round-trip parse failed (library bug or feature mismatch): %v", err)
    }
    return err
}

When it happens

Trigger: Marshal or runMaps calls marshalSorted; bb.Marshal succeeded but btf.LoadSpecFromReader on the in-memory blob returns an error (corrupt split-BTF blob, incompatible BTF features the parser can't round-trip).

Common situations: BTF features (e.g. enum64, kind-specific encodings) written by the builder cannot be re-parsed by the same library version — usually signals a cilium/ebpf version mismatch or bug; memory blob truncated by an intermediate writer.

Related errors

• adding type %s: %w
• marshaling BTF before sort: %w
• iterating BTF types: %w
• creating BTF builder: %w
• cannot parse BTF debug info %s: %w

AI-assisted analysis of cilium/cilium@ac7b90affa (2026-08-31). Data as JSON: /api/errors/3e9df54c241e3357. Report an issue: GitHub.