btf: extract BTF type size calculation

This pre-patch extracts calculation of amount of space taken by BTF type descriptor
for later reuse by btf_dedup functionality.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/btf.c

@@ -182,50 +182,53 @@ static int btf_parse_str_sec(struct btf *btf)
 	return 0;
 }
 
-static int btf_parse_type_sec(struct btf *btf)
+static int btf_type_size(struct btf_type *t)
 {
-	struct btf_header *hdr = btf->hdr;
-	void *nohdr_data = btf->nohdr_data;
-	void *next_type = nohdr_data + hdr->type_off;
-	void *end_type = nohdr_data + hdr->str_off;
-
-	while (next_type < end_type) {
-		struct btf_type *t = next_type;
+	int base_size = sizeof(struct btf_type);
 	__u16 vlen = BTF_INFO_VLEN(t->info);
-		int err;
 
-		next_type += sizeof(*t);
 	switch (BTF_INFO_KIND(t->info)) {
+	case BTF_KIND_FWD:
+	case BTF_KIND_CONST:
+	case BTF_KIND_VOLATILE:
+	case BTF_KIND_RESTRICT:
+	case BTF_KIND_PTR:
+	case BTF_KIND_TYPEDEF:
+	case BTF_KIND_FUNC:
+		return base_size;
 	case BTF_KIND_INT:
-			next_type += sizeof(int);
-			break;
+		return base_size + sizeof(__u32);
+	case BTF_KIND_ENUM:
+		return base_size + vlen * sizeof(struct btf_enum);
 	case BTF_KIND_ARRAY:
-			next_type += sizeof(struct btf_array);
-			break;
+		return base_size + sizeof(struct btf_array);
 	case BTF_KIND_STRUCT:
 	case BTF_KIND_UNION:
-			next_type += vlen * sizeof(struct btf_member);
-			break;
-		case BTF_KIND_ENUM:
-			next_type += vlen * sizeof(struct btf_enum);
-			break;
+		return base_size + vlen * sizeof(struct btf_member);
 	case BTF_KIND_FUNC_PROTO:
-			next_type += vlen * sizeof(struct btf_param);
-			break;
-		case BTF_KIND_FUNC:
-		case BTF_KIND_TYPEDEF:
-		case BTF_KIND_PTR:
-		case BTF_KIND_FWD:
-		case BTF_KIND_VOLATILE:
-		case BTF_KIND_CONST:
-		case BTF_KIND_RESTRICT:
-			break;
+		return base_size + vlen * sizeof(struct btf_param);
 	default:
-			pr_debug("Unsupported BTF_KIND:%u\n",
-			     BTF_INFO_KIND(t->info));
+		pr_debug("Unsupported BTF_KIND:%u\n", BTF_INFO_KIND(t->info));
 		return -EINVAL;
 	}
+}
 
+static int btf_parse_type_sec(struct btf *btf)
+{
+	struct btf_header *hdr = btf->hdr;
+	void *nohdr_data = btf->nohdr_data;
+	void *next_type = nohdr_data + hdr->type_off;
+	void *end_type = nohdr_data + hdr->str_off;
+
+	while (next_type < end_type) {
+		struct btf_type *t = next_type;
+		int type_size;
+		int err;
+
+		type_size = btf_type_size(t);
+		if (type_size < 0)
+			return type_size;
+		next_type += type_size;
 		err = btf_add_type(btf, t);
 		if (err)
 			return err;
@@ -252,21 +255,6 @@ static bool btf_type_is_void_or_null(const struct btf_type *t)
 	return !t || btf_type_is_void(t);
 }
 
-static __s64 btf_type_size(const struct btf_type *t)
-{
-	switch (BTF_INFO_KIND(t->info)) {
-	case BTF_KIND_INT:
-	case BTF_KIND_STRUCT:
-	case BTF_KIND_UNION:
-	case BTF_KIND_ENUM:
-		return t->size;
-	case BTF_KIND_PTR:
-		return sizeof(void *);
-	default:
-		return -EINVAL;
-	}
-}
-
 #define MAX_RESOLVE_DEPTH 32
 
 __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
@@ -280,11 +268,16 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
 	t = btf__type_by_id(btf, type_id);
 	for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
 	     i++) {
-		size = btf_type_size(t);
-		if (size >= 0)
-			break;
-
 		switch (BTF_INFO_KIND(t->info)) {
+		case BTF_KIND_INT:
+		case BTF_KIND_STRUCT:
+		case BTF_KIND_UNION:
+		case BTF_KIND_ENUM:
+			size = t->size;
+			goto done;
+		case BTF_KIND_PTR:
+			size = sizeof(void *);
+			goto done;
 		case BTF_KIND_TYPEDEF:
 		case BTF_KIND_VOLATILE:
 		case BTF_KIND_CONST:
@@ -308,6 +301,7 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
 	if (size < 0)
 		return -EINVAL;
 
+done:
 	if (nelems && size > UINT32_MAX / nelems)
 		return -E2BIG;