libbpf: Split field iter code into its own file kernel

This will allow it to be shared with the kernel. No functional change.

Suggested-by: Andrii Nakryiko <[e-mail]>
Signed-off-by: Alan Maguire <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/lib/bpf/Build

···
 libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o \
 	    netlink.o bpf_prog_linfo.o libbpf_probes.o hashmap.o \
 	    btf_dump.o ringbuf.o strset.o linker.o gen_loader.o relo_core.o \
-	    usdt.o zip.o elf.o features.o btf_relocate.o
+	    usdt.o zip.o elf.o features.o btf_iter.o btf_relocate.o

tools/lib/bpf/btf.c

···
 	return btf__parse_split(path, vmlinux_btf);
 }
 
-int btf_field_iter_init(struct btf_field_iter *it, struct btf_type *t, enum btf_field_iter_kind iter_kind)
-{
-	it->p = NULL;
-	it->m_idx = -1;
-	it->off_idx = 0;
-	it->vlen = 0;
-
-	switch (iter_kind) {
-	case BTF_FIELD_ITER_IDS:
-		switch (btf_kind(t)) {
-		case BTF_KIND_UNKN:
-		case BTF_KIND_INT:
-		case BTF_KIND_FLOAT:
-		case BTF_KIND_ENUM:
-		case BTF_KIND_ENUM64:
-			it->desc = (struct btf_field_desc) {};
-			break;
-		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:
-		case BTF_KIND_VAR:
-		case BTF_KIND_DECL_TAG:
-		case BTF_KIND_TYPE_TAG:
-			it->desc = (struct btf_field_desc) { 1, {offsetof(struct btf_type, type)} };
-			break;
-		case BTF_KIND_ARRAY:
-			it->desc = (struct btf_field_desc) {
-				2, {sizeof(struct btf_type) + offsetof(struct btf_array, type),
-				    sizeof(struct btf_type) + offsetof(struct btf_array, index_type)}
-			};
-			break;
-		case BTF_KIND_STRUCT:
-		case BTF_KIND_UNION:
-			it->desc = (struct btf_field_desc) {
-				0, {},
-				sizeof(struct btf_member),
-				1, {offsetof(struct btf_member, type)}
-			};
-			break;
-		case BTF_KIND_FUNC_PROTO:
-			it->desc = (struct btf_field_desc) {
-				1, {offsetof(struct btf_type, type)},
-				sizeof(struct btf_param),
-				1, {offsetof(struct btf_param, type)}
-			};
-			break;
-		case BTF_KIND_DATASEC:
-			it->desc = (struct btf_field_desc) {
-				0, {},
-				sizeof(struct btf_var_secinfo),
-				1, {offsetof(struct btf_var_secinfo, type)}
-			};
-			break;
-		default:
-			return -EINVAL;
-		}
-		break;
-	case BTF_FIELD_ITER_STRS:
-		switch (btf_kind(t)) {
-		case BTF_KIND_UNKN:
-			it->desc = (struct btf_field_desc) {};
-			break;
-		case BTF_KIND_INT:
-		case BTF_KIND_FLOAT:
-		case BTF_KIND_FWD:
-		case BTF_KIND_ARRAY:
-		case BTF_KIND_CONST:
-		case BTF_KIND_VOLATILE:
-		case BTF_KIND_RESTRICT:
-		case BTF_KIND_PTR:
-		case BTF_KIND_TYPEDEF:
-		case BTF_KIND_FUNC:
-		case BTF_KIND_VAR:
-		case BTF_KIND_DECL_TAG:
-		case BTF_KIND_TYPE_TAG:
-		case BTF_KIND_DATASEC:
-			it->desc = (struct btf_field_desc) {
-				1, {offsetof(struct btf_type, name_off)}
-			};
-			break;
-		case BTF_KIND_ENUM:
-			it->desc = (struct btf_field_desc) {
-				1, {offsetof(struct btf_type, name_off)},
-				sizeof(struct btf_enum),
-				1, {offsetof(struct btf_enum, name_off)}
-			};
-			break;
-		case BTF_KIND_ENUM64:
-			it->desc = (struct btf_field_desc) {
-				1, {offsetof(struct btf_type, name_off)},
-				sizeof(struct btf_enum64),
-				1, {offsetof(struct btf_enum64, name_off)}
-			};
-			break;
-		case BTF_KIND_STRUCT:
-		case BTF_KIND_UNION:
-			it->desc = (struct btf_field_desc) {
-				1, {offsetof(struct btf_type, name_off)},
-				sizeof(struct btf_member),
-				1, {offsetof(struct btf_member, name_off)}
-			};
-			break;
-		case BTF_KIND_FUNC_PROTO:
-			it->desc = (struct btf_field_desc) {
-				1, {offsetof(struct btf_type, name_off)},
-				sizeof(struct btf_param),
-				1, {offsetof(struct btf_param, name_off)}
-			};
-			break;
-		default:
-			return -EINVAL;
-		}
-		break;
-	default:
-		return -EINVAL;
-	}
-
-	if (it->desc.m_sz)
-		it->vlen = btf_vlen(t);
-
-	it->p = t;
-	return 0;
-}
-
-__u32 *btf_field_iter_next(struct btf_field_iter *it)
-{
-	if (!it->p)
-		return NULL;
-
-	if (it->m_idx < 0) {
-		if (it->off_idx < it->desc.t_off_cnt)
-			return it->p + it->desc.t_offs[it->off_idx++];
-		/* move to per-member iteration */
-		it->m_idx = 0;
-		it->p += sizeof(struct btf_type);
-		it->off_idx = 0;
-	}
-
-	/* if type doesn't have members, stop */
-	if (it->desc.m_sz == 0) {
-		it->p = NULL;
-		return NULL;
-	}
-
-	if (it->off_idx >= it->desc.m_off_cnt) {
-		/* exhausted this member's fields, go to the next member */
-		it->m_idx++;
-		it->p += it->desc.m_sz;
-		it->off_idx = 0;
-	}
-
-	if (it->m_idx < it->vlen)
-		return it->p + it->desc.m_offs[it->off_idx++];
-
-	it->p = NULL;
-	return NULL;
-}
-
 int btf_ext_visit_type_ids(struct btf_ext *btf_ext, type_id_visit_fn visit, void *ctx)
 {
 	const struct btf_ext_info *seg;

tools/lib/bpf/btf_iter.c

···
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+/* Copyright (c) 2021 Facebook */
+/* Copyright (c) 2024, Oracle and/or its affiliates. */
+
+#include "btf.h"
+#include "libbpf_internal.h"
+
+int btf_field_iter_init(struct btf_field_iter *it, struct btf_type *t,
+			enum btf_field_iter_kind iter_kind)
+{
+	it->p = NULL;
+	it->m_idx = -1;
+	it->off_idx = 0;
+	it->vlen = 0;
+
+	switch (iter_kind) {
+	case BTF_FIELD_ITER_IDS:
+		switch (btf_kind(t)) {
+		case BTF_KIND_UNKN:
+		case BTF_KIND_INT:
+		case BTF_KIND_FLOAT:
+		case BTF_KIND_ENUM:
+		case BTF_KIND_ENUM64:
+			it->desc = (struct btf_field_desc) {};
+			break;
+		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:
+		case BTF_KIND_VAR:
+		case BTF_KIND_DECL_TAG:
+		case BTF_KIND_TYPE_TAG:
+			it->desc = (struct btf_field_desc) { 1, {offsetof(struct btf_type, type)} };
+			break;
+		case BTF_KIND_ARRAY:
+			it->desc = (struct btf_field_desc) {
+				2, {sizeof(struct btf_type) + offsetof(struct btf_array, type),
+				sizeof(struct btf_type) + offsetof(struct btf_array, index_type)}
+			};
+			break;
+		case BTF_KIND_STRUCT:
+		case BTF_KIND_UNION:
+			it->desc = (struct btf_field_desc) {
+				0, {},
+				sizeof(struct btf_member),
+				1, {offsetof(struct btf_member, type)}
+			};
+			break;
+		case BTF_KIND_FUNC_PROTO:
+			it->desc = (struct btf_field_desc) {
+				1, {offsetof(struct btf_type, type)},
+				sizeof(struct btf_param),
+				1, {offsetof(struct btf_param, type)}
+			};
+			break;
+		case BTF_KIND_DATASEC:
+			it->desc = (struct btf_field_desc) {
+				0, {},
+				sizeof(struct btf_var_secinfo),
+				1, {offsetof(struct btf_var_secinfo, type)}
+			};
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case BTF_FIELD_ITER_STRS:
+		switch (btf_kind(t)) {
+		case BTF_KIND_UNKN:
+			it->desc = (struct btf_field_desc) {};
+			break;
+		case BTF_KIND_INT:
+		case BTF_KIND_FLOAT:
+		case BTF_KIND_FWD:
+		case BTF_KIND_ARRAY:
+		case BTF_KIND_CONST:
+		case BTF_KIND_VOLATILE:
+		case BTF_KIND_RESTRICT:
+		case BTF_KIND_PTR:
+		case BTF_KIND_TYPEDEF:
+		case BTF_KIND_FUNC:
+		case BTF_KIND_VAR:
+		case BTF_KIND_DECL_TAG:
+		case BTF_KIND_TYPE_TAG:
+		case BTF_KIND_DATASEC:
+			it->desc = (struct btf_field_desc) {
+				1, {offsetof(struct btf_type, name_off)}
+			};
+			break;
+		case BTF_KIND_ENUM:
+			it->desc = (struct btf_field_desc) {
+				1, {offsetof(struct btf_type, name_off)},
+				sizeof(struct btf_enum),
+				1, {offsetof(struct btf_enum, name_off)}
+			};
+			break;
+		case BTF_KIND_ENUM64:
+			it->desc = (struct btf_field_desc) {
+				1, {offsetof(struct btf_type, name_off)},
+				sizeof(struct btf_enum64),
+				1, {offsetof(struct btf_enum64, name_off)}
+			};
+			break;
+		case BTF_KIND_STRUCT:
+		case BTF_KIND_UNION:
+			it->desc = (struct btf_field_desc) {
+				1, {offsetof(struct btf_type, name_off)},
+				sizeof(struct btf_member),
+				1, {offsetof(struct btf_member, name_off)}
+			};
+			break;
+		case BTF_KIND_FUNC_PROTO:
+			it->desc = (struct btf_field_desc) {
+				1, {offsetof(struct btf_type, name_off)},
+				sizeof(struct btf_param),
+				1, {offsetof(struct btf_param, name_off)}
+			};
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (it->desc.m_sz)
+		it->vlen = btf_vlen(t);
+
+	it->p = t;
+	return 0;
+}
+
+__u32 *btf_field_iter_next(struct btf_field_iter *it)
+{
+	if (!it->p)
+		return NULL;
+
+	if (it->m_idx < 0) {
+		if (it->off_idx < it->desc.t_off_cnt)
+			return it->p + it->desc.t_offs[it->off_idx++];
+		/* move to per-member iteration */
+		it->m_idx = 0;
+		it->p += sizeof(struct btf_type);
+		it->off_idx = 0;
+	}
+
+	/* if type doesn't have members, stop */
+	if (it->desc.m_sz == 0) {
+		it->p = NULL;
+		return NULL;
+	}
+
+	if (it->off_idx >= it->desc.m_off_cnt) {
+		/* exhausted this member's fields, go to the next member */
+		it->m_idx++;
+		it->p += it->desc.m_sz;
+		it->off_idx = 0;
+	}
+
+	if (it->m_idx < it->vlen)
+		return it->p + it->desc.m_offs[it->off_idx++];
+
+	it->p = NULL;
+	return NULL;
+}