From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 69-171-232-180.mail-mxout.facebook.com (69-171-232-180.mail-mxout.facebook.com [69.171.232.180]) (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 171DA3EE1EE for ; Thu, 15 Oct 2026 04:02:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=69.171.232.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792036934; cv=none; b=OMPTKQ0yKCc8B+JBBHeC3hskhmhIg+NtOIW8ucCsLxJJiE1GC1ph7aJMUdvAAAg78we/yiqoL1Tdw2v+jFX7I9qVjUDvohNQI1avjkoJ4D5tCpb2kM4TQxU5GNC3iwfF1PloMhMZSa0Hbze8+AajS1v7ci99hEKNlgRFSSRMqLk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792036934; c=relaxed/simple; bh=fYojV1QgPqqP475NiWHC1E5uSGKtRcohjGDPf9oOGXw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jRgbCSx9728q7uDw2sOdtdY68921qQILM025n2sC91/ApczaOqynJCrR3eJ+vPMTt2ICTwt+e5ruMJ8ZiEI3wCY0CnQoQVEaYpWJAVRTLEdY3nYr9Liq8hLb4r9EhIb7AirS4Ib8W4Odfr7vW1VMSgH1x8Hz/oakCB09vvYqul8= 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=69.171.232.180 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 25A5D31498D98F; Wed, 14 Oct 2026 21:01:59 -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 v11 03/26] bpf: Add the bpf_unwind() and bpf_unwind_resume() kfuncs Date: Wed, 14 Oct 2026 21:01:59 -0700 Message-ID: <20261015040159.855401-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261015040143.854070-1-yonghong.song@linux.dev> References: <20261015040143.854070-1-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 An exception cleanup needs two terminators: - bpf_unwind() begins an unwind: the frames it leaves run their landing pads on the way out to the program's exit. It is separate from bpf_throw(), which discards the frames in between. - bpf_unwind_resume() ends a landing pad, carrying the unwind on. The compiler calls it _Unwind_Resume, which a later libbpf patch resolves to this name, and passes it the exception object, which the kfunc takes as ptr__ign. Neither is registered yet: that waits for the patch that dispatches pads at run time. Signed-off-by: Yonghong Song --- kernel/bpf/helpers.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index a284f20c97d5..98ab22c6adc4 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -3424,6 +3424,10 @@ static bool bpf_stack_walker(void *cookie, u64 ip,= u64 sp, u64 bp) return false; } =20 +__bpf_kfunc void bpf_unwind(void) +{ +} + __bpf_kfunc void bpf_throw(u64 cookie) { struct bpf_throw_ctx ctx =3D {}; @@ -3445,6 +3449,15 @@ __bpf_kfunc void bpf_throw(u64 cookie) WARN(1, "A call to BPF exception callback should never return\n"); } =20 +__bpf_kfunc void bpf_unwind_resume(void *ptr__ign) +{ + /* + * Not meant to run: every call of this kfunc is to be lowered to + * 'r0 =3D 0; exit' by the verifier. + */ + WARN_ONCE(1, "exception cleanup resume was not lowered to a return\n"); +} + __bpf_kfunc int bpf_wq_init(struct bpf_wq *wq, void *p__const_map, unsig= ned int flags) { struct bpf_async_kern *async =3D (struct bpf_async_kern *)wq; --=20 2.53.0-Meta