[PATCH v4 bpf-next 03/17] libbpf: use kind layout to compute an unknown kind size

[Alan Maguire <alan.maguire@xxxxxxxxxx>]

This allows BTF parsing to proceed even if we do not know the
kind.

Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
 tools/lib/bpf/btf.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1d043fe49d4c..973da2b21df2 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -350,7 +350,29 @@ static int btf_parse_kind_layout_sec(struct btf *btf)
 	return 0;
 }
 
-static int btf_type_size(const struct btf_type *t)
+/* for unknown kinds, consult kind layout. */
+static int btf_type_size_unknown(const struct btf *btf, const struct btf_type *t)
+{
+	int size = sizeof(struct btf_type);
+	struct btf_kind_layout *k = NULL;
+	__u16 vlen = btf_vlen(t);
+	__u8 kind = btf_kind(t);
+
+	if (btf->kind_layout)
+		k = &((struct btf_kind_layout *)btf->kind_layout)[kind];
+
+	if (!k || (void *)k > ((void *)btf->kind_layout + btf->hdr->kind_layout_len)) {
+		pr_debug("Unsupported BTF_KIND: %u\n", btf_kind(t));
+		return -EINVAL;
+	}
+
+	size += k->info_sz;
+	size += vlen * k->elem_sz;
+
+	return size;
+}
+
+static int btf_type_size(const struct btf *btf, const struct btf_type *t)
 {
 	const int base_size = sizeof(struct btf_type);
 	__u16 vlen = btf_vlen(t);
@@ -386,8 +408,7 @@ static int btf_type_size(const struct btf_type *t)
 	case BTF_KIND_DECL_TAG:
 		return base_size + sizeof(struct btf_decl_tag);
 	default:
-		pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));
-		return -EINVAL;
+		return btf_type_size_unknown(btf, t);
 	}
 }
 
@@ -486,7 +507,7 @@ static int btf_parse_type_sec(struct btf *btf)
 		if (btf->swapped_endian)
 			btf_bswap_type_base(next_type);
 
-		type_size = btf_type_size(next_type);
+		type_size = btf_type_size(btf, next_type);
 		if (type_size < 0)
 			return type_size;
 		if (next_type + type_size > end_type) {
@@ -1862,7 +1883,7 @@ int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_t
 	struct btf_type *t;
 	int sz, err;
 
-	sz = btf_type_size(src_type);
+	sz = btf_type_size(src_btf, src_type);
 	if (sz < 0)
 		return libbpf_err(sz);
 
@@ -1943,7 +1964,7 @@ int btf__add_btf(struct btf *btf, const struct btf *src_btf)
 	memcpy(t, src_btf->types_data, data_sz);
 
 	for (i = 0; i < cnt; i++) {
-		sz = btf_type_size(t);
+		sz = btf_type_size(src_btf, t);
 		if (sz < 0) {
 			/* unlikely, has to be corrupted src_btf */
 			err = sz;
@@ -4939,7 +4960,7 @@ static int btf_dedup_compact_types(struct btf_dedup *d)
 			continue;
 
 		t = btf__type_by_id(d->btf, id);
-		len = btf_type_size(t);
+		len = btf_type_size(d->btf, t);
 		if (len < 0)
 			return len;
 
-- 
2.31.1