[PATCH bpf-next 2/2] bpf: Use bpf_core_types_are_compat functionality from relo_core.c

["Daniel Müller" <deso@posteo.net>]

This change adjusts the kernel BPF code to use
bpf_core_types_are_compat_recur() from relo_core.c for its
implementation of bpf_core_types_are_compat(). In so doing we fix an
oversight where we were still comparing local and target BTF kinds for
equality directly, as opposed to using btf_kind_core_compat() which
correctly handles enum/enum64 kinds.

Signed-off-by: Daniel Müller <deso@posteo.net>
---
 kernel/bpf/btf.c | 86 ++----------------------------------------------
 1 file changed, 2 insertions(+), 84 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index f08037..031511b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7416,87 +7416,6 @@ EXPORT_SYMBOL_GPL(register_btf_id_dtor_kfuncs);
 
 #define MAX_TYPES_ARE_COMPAT_DEPTH 2
 
-static
-int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
-				const struct btf *targ_btf, __u32 targ_id,
-				int level)
-{
-	const struct btf_type *local_type, *targ_type;
-	int depth = 32; /* max recursion depth */
-
-	/* caller made sure that names match (ignoring flavor suffix) */
-	local_type = btf_type_by_id(local_btf, local_id);
-	targ_type = btf_type_by_id(targ_btf, targ_id);
-	if (btf_kind(local_type) != btf_kind(targ_type))
-		return 0;
-
-recur:
-	depth--;
-	if (depth < 0)
-		return -EINVAL;
-
-	local_type = btf_type_skip_modifiers(local_btf, local_id, &local_id);
-	targ_type = btf_type_skip_modifiers(targ_btf, targ_id, &targ_id);
-	if (!local_type || !targ_type)
-		return -EINVAL;
-
-	if (btf_kind(local_type) != btf_kind(targ_type))
-		return 0;
-
-	switch (btf_kind(local_type)) {
-	case BTF_KIND_UNKN:
-	case BTF_KIND_STRUCT:
-	case BTF_KIND_UNION:
-	case BTF_KIND_ENUM:
-	case BTF_KIND_FWD:
-	case BTF_KIND_ENUM64:
-		return 1;
-	case BTF_KIND_INT:
-		/* just reject deprecated bitfield-like integers; all other
-		 * integers are by default compatible between each other
-		 */
-		return btf_int_offset(local_type) == 0 && btf_int_offset(targ_type) == 0;
-	case BTF_KIND_PTR:
-		local_id = local_type->type;
-		targ_id = targ_type->type;
-		goto recur;
-	case BTF_KIND_ARRAY:
-		local_id = btf_array(local_type)->type;
-		targ_id = btf_array(targ_type)->type;
-		goto recur;
-	case BTF_KIND_FUNC_PROTO: {
-		struct btf_param *local_p = btf_params(local_type);
-		struct btf_param *targ_p = btf_params(targ_type);
-		__u16 local_vlen = btf_vlen(local_type);
-		__u16 targ_vlen = btf_vlen(targ_type);
-		int i, err;
-
-		if (local_vlen != targ_vlen)
-			return 0;
-
-		for (i = 0; i < local_vlen; i++, local_p++, targ_p++) {
-			if (level <= 0)
-				return -EINVAL;
-
-			btf_type_skip_modifiers(local_btf, local_p->type, &local_id);
-			btf_type_skip_modifiers(targ_btf, targ_p->type, &targ_id);
-			err = __bpf_core_types_are_compat(local_btf, local_id,
-							  targ_btf, targ_id,
-							  level - 1);
-			if (err <= 0)
-				return err;
-		}
-
-		/* tail recurse for return type check */
-		btf_type_skip_modifiers(local_btf, local_type->type, &local_id);
-		btf_type_skip_modifiers(targ_btf, targ_type->type, &targ_id);
-		goto recur;
-	}
-	default:
-		return 0;
-	}
-}
-
 /* Check local and target types for compatibility. This check is used for
  * type-based CO-RE relocations and follow slightly different rules than
  * field-based relocations. This function assumes that root types were already
@@ -7519,9 +7438,8 @@ int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
 int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
 			      const struct btf *targ_btf, __u32 targ_id)
 {
-	return __bpf_core_types_are_compat(local_btf, local_id,
-					   targ_btf, targ_id,
-					   MAX_TYPES_ARE_COMPAT_DEPTH);
+	return bpf_core_types_are_compat_recur(local_btf, local_id, targ_btf, targ_id,
+					       MAX_TYPES_ARE_COMPAT_DEPTH);
 }
 
 static bool bpf_core_is_flavor_sep(const char *s)
-- 
2.30.2