bpf: Add btf_type_is_arena_ptr()

Add btf_type_is_arena_ptr() to test whether a BTF type is a pointer
carrying the "arena" type tag, and use it to simplify both
btf_scan_type_tags() and btf_validate_return_type(). The helper has
external linkage because a later patch calls it from verifier.c to
decide whether a struct member returned by value may be an arena
pointer.

btf_scan_type_tags() drove btf_type_tag_walk() with a one-entry match
table, so the "multiple type tags" error it checked for could never
fire: btf_type_tag_walk() only fails when the walk sets more than one
flag. Dropping that error path, and with it the int return, is
therefore no functional change.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260829061529.1693266-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 89d5a5c4f117..ddd0f4f32d24 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -235,6 +235,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 				    u32 field_mask, u32 value_size);
 int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec);
 bool btf_type_is_void(const struct btf_type *t);
+bool btf_type_is_arena_ptr(const struct btf *btf, const struct btf_type *t);
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
 s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p);
 struct btf *btf_get_module_btf(const struct module *module);