From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27E7A3D1ABD for ; Tue, 25 Aug 2026 20:54:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=66.220.144.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787691297; cv=none; b=rzTxNnJh6z84p+O/4T51k9dwQe+xm7bPrbHyxU9x5HYelCZbTO5NKlnbfCcyZc91J0k/rT2OfAU7/xWDuPsyUA39fMcONrpjqkfXrBGDUCGRqfnvLDrCAlqoYz/datFM3CK3ykcZ/rV1Y+6XwO+RU7jXo9IuDqardRwohNNfujg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787691297; c=relaxed/simple; bh=klaBTrbxVvFG7CpDP19YZMLtsp6WhOBhOZQujvm6EFU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fHbiNRbKnFO69ZzRkEiFX2y9fqtfeySZii8/My6iDCxLVx06UUAfy6Qn64+qHu+gTYpWmgD+b0cGvsf9Y1JlarPqgDiwrnCHlsreHsPOkPETJBpvYCCtoPokBBtGoyZucOAAWA5hZpr+aqrgV5KlVdOcaSZw8P9fpnQlGUbHS+M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=fail smtp.mailfrom=linux.dev; arc=none smtp.client-ip=66.220.144.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=linux.dev Received: by devvm16039.vll0.facebook.com (Postfix, from userid 128203) id 21260268293D90; Tue, 25 Aug 2026 13:54:43 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , kernel-team@fb.com Subject: [PATCH bpf-next v2 06/10] bpf: Allow a global function to return arena pointers by value Date: Tue, 25 Aug 2026 13:54:43 -0700 Message-ID: <20260825205443.1323867-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260825205412.1320099-1-yonghong.song@linux.dev> References: <20260825205412.1320099-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable A global function may already return an arena pointer on its own, and check_global_ret_scalar_reg() accepts one in either half of the R0:R2 pair. Let the members of a by-value struct it returns be arena pointers as well, rather than scalars only. Signed-off-by: Yonghong Song --- kernel/bpf/btf.c | 17 +++++++++++------ .../selftests/bpf/progs/exceptions_fail.c | 2 +- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index b1f4ef614d4c..70481fadacc0 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -7972,14 +7972,18 @@ static int btf_validate_return_type(struct bpf_ve= rifier_env *env, struct btf *bt =20 if (btf_type_is_struct(t) && t->size <=3D 16) { /* - * A global function's caller models the return as an opaque - * scalar pair, so it may only return scalars by value. A local - * function is verified inline, so a pointer field stays tracked - * and needs no such restriction. + * A global function may return a struct with scalar(s) or arena + * pointer(s) as its members. A local function is verified inline, + * so its caller receives the real register state and any member + * is fine. */ bool local_func =3D subprog && !is_global; + u32 member_kinds =3D BTF_MEMBER_SCALAR; =20 - if (local_func || btf_struct_is_composed_of(env, btf, t, BTF_MEMBER_SC= ALAR)) + if (subprog) + member_kinds |=3D BTF_MEMBER_ARENA_PTR; + + if (local_func || btf_struct_is_composed_of(env, btf, t, member_kinds)= ) return 0; } =20 @@ -8075,7 +8079,8 @@ int btf_prepare_func_args(struct bpf_verifier_env *= env, int subprog) if (is_global) { bpf_log(log, "Global function %s() has unsupported return type. " - "Only void, scalar, or a scalar-only struct/union up to 16 bytes is = supported.\n", + "Only void, a scalar, an arena pointer, or a struct/union of " + "those up to 16 bytes is supported.\n", tname); } return err; diff --git a/tools/testing/selftests/bpf/progs/exceptions_fail.c b/tools/= testing/selftests/bpf/progs/exceptions_fail.c index 9708efb93683..35794329640b 100644 --- a/tools/testing/selftests/bpf/progs/exceptions_fail.c +++ b/tools/testing/selftests/bpf/progs/exceptions_fail.c @@ -60,7 +60,7 @@ __noinline int exception_cb_ok_arg_small(int a) =20 SEC("?tc") __exception_cb(exception_cb_bad_ret_type1) -__failure __msg("Only void, scalar, or a scalar-only struct/union up to = 16 bytes is supported.") +__failure __msg("Only void, a scalar, an arena pointer, or a struct/unio= n of those") int reject_exception_cb_type_1(struct __sk_buff *ctx) { bpf_throw(0); --=20 2.53.0-Meta