From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6948DC433E0 for ; Wed, 5 Aug 2020 17:37:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4520722D37 for ; Wed, 5 Aug 2020 17:37:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="dSwKQJeL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728634AbgHERhP (ORCPT ); Wed, 5 Aug 2020 13:37:15 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:44339 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728883AbgHERhM (ORCPT ); Wed, 5 Aug 2020 13:37:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596649031; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=oMaXr6AjoRreIUBU+G85r8nZDJYOJ3q1LtahtihDE/0=; b=dSwKQJeLu9IiD5H7LW2tn6p/DhisUSxvd1Bibq3O3FHE73fMnDqY0BleGmjSpL+UUiV4fl dV0d7uM79NU4w+3Gd7cpDU1jb5p8eOaR+ZbI1Di9KhP3r53FDWO2HeBVEY33JyHPTbMjG2 YAPZzW2z4RwMF3XqnIbjhuD95ufU2ww= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-295-jpzXJGi1N-K01UX5gt3qkA-1; Wed, 05 Aug 2020 13:37:07 -0400 X-MC-Unique: jpzXJGi1N-K01UX5gt3qkA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 31A628015F4; Wed, 5 Aug 2020 17:37:03 +0000 (UTC) Received: from krava (unknown [10.40.192.11]) by smtp.corp.redhat.com (Postfix) with SMTP id 9E45F87A46; Wed, 5 Aug 2020 17:36:59 +0000 (UTC) Date: Wed, 5 Aug 2020 19:36:58 +0200 From: Jiri Olsa To: Andrii Nakryiko Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Networking , bpf , Song Liu , Yonghong Song , Martin KaFai Lau , David Miller , John Fastabend , Wenbo Zhang , KP Singh , Brendan Gregg , Florent Revest , Al Viro Subject: Re: [PATCH v9 bpf-next 06/14] bpf: Remove recursion call in btf_struct_access Message-ID: <20200805173658.GB319954@krava> References: <20200801170322.75218-1-jolsa@kernel.org> <20200801170322.75218-7-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Aug 04, 2020 at 11:12:49PM -0700, Andrii Nakryiko wrote: > On Sat, Aug 1, 2020 at 10:04 AM Jiri Olsa wrote: > > > > Andrii suggested we can simply jump to again label > > instead of making recursion call. > > > > Suggested-by: Andrii Nakryiko > > Signed-off-by: Jiri Olsa > > --- > > kernel/bpf/btf.c | 11 +++++------ > > 1 file changed, 5 insertions(+), 6 deletions(-) > > > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > > index bc05a24f7361..0f995038b589 100644 > > --- a/kernel/bpf/btf.c > > +++ b/kernel/bpf/btf.c > > @@ -3931,14 +3931,13 @@ int btf_struct_access(struct bpf_verifier_log *log, > > /* Only allow structure for now, can be relaxed for > > * other types later. > > */ > > - elem_type = btf_type_skip_modifiers(btf_vmlinux, > > - array_elem->type, NULL); > > - if (!btf_type_is_struct(elem_type)) > > + t = btf_type_skip_modifiers(btf_vmlinux, array_elem->type, > > + NULL); > > + if (!btf_type_is_struct(t)) > > goto error; > > > > - off = (off - moff) % elem_type->size; > > - return btf_struct_access(log, elem_type, off, size, atype, > > - next_btf_id); > > + off = (off - moff) % t->size; > > + goto again; > > Transformation looks good, thanks. So: > > Acked-by: Andrii Nakryiko > > But this '% t->size' makes me wonder what will happen when we have an > array of zero-sized structs or multi-dimensional arrays with > dimensions of size 0... I.e.: > > struct {} arr[123]; > > or > > int arr[0][0]0]; > > We should probably be more careful with division here. right, definitely.. I'll send follow up patch for that thanks, jirka