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,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 786B6C433E0 for ; Wed, 5 Aug 2020 06:13:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D69922B40 for ; Wed, 5 Aug 2020 06:13:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="n6Y2H2WW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726232AbgHEGNB (ORCPT ); Wed, 5 Aug 2020 02:13:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725920AbgHEGNB (ORCPT ); Wed, 5 Aug 2020 02:13:01 -0400 Received: from mail-yb1-xb43.google.com (mail-yb1-xb43.google.com [IPv6:2607:f8b0:4864:20::b43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 619F4C06174A; Tue, 4 Aug 2020 23:13:01 -0700 (PDT) Received: by mail-yb1-xb43.google.com with SMTP id e187so10892185ybc.5; Tue, 04 Aug 2020 23:13:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=9iXihjRFVPg2A7GpZV7d5YBUlfuYnief6L8DzAwhNQU=; b=n6Y2H2WWmCMbfqbcljcDHEqK1L+Ew6tQnJwT1yINtKYqsk2lozkArB54gZVRfb4Lqp BX+JkfGswldenIkYA4ZtPlHkBCoH/4Pcd8mqKuw1nTvhtvV/cQdj8k7s9C4WYr8sj6zS JHbi/dIzy+GxYIh0+vrA/VoJtqY7KZx9jYXck+pwuEFVZidIB5vaVHoBL0kEA1aOUTym goZZ92Axo07KJrviU+TVyCEv4nC+RSqJqxisK55gfii+FZrBAY9kvW32DTdPedzYAvRk x/Ldn89C1dvXZGK8AXOwfsLhNQ0jKnXEiuTCAfwvfKnOvU3ZIcz+ZT8c0u6YUj4fA1kA Gz/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=9iXihjRFVPg2A7GpZV7d5YBUlfuYnief6L8DzAwhNQU=; b=WVYPQmeEy1oNUTiC9jtW0yqO5AyigiMA+HGSv56D+oMYPmyrE2fHBTz40fZTc1Cjhw c4QZTfGjLRHk+ANZQrlwgpSu9QgY2hpJqV6CJ1S89iDbNoP4R/hize0AebInytk7UmYD pFkNPFn6ks/56bW7uKHivlJMQbTCVgbXOpiNqlv/aUA12nylXpBYdC8OeQAwPwrbxCxe JlNSZs0rI6ORt4M0M/O5C8iLJx5tgllRbQ5Y+ibKuBaRAbi2v24zSa/jh+8uksFHJsfB g6Bb/KSR5zO3f3RP05mk06K7osSBpBK9G7PXVOGetVsTLqZPBPKZiDsUbhuv7oHq1xRe YGQQ== X-Gm-Message-State: AOAM530onvrawmvh9uJd0Oxv4+Ruf0Ax8DDO5XkZzUOx61QVXcwYqmNe s5368ompeQwjz4LLWPV6UmWo/gPHvat3X3svyTM= X-Google-Smtp-Source: ABdhPJxTcYVEbJrxK9CDw9YdYiRjgtL8ctcMiDxLOHWTnUuVYoW6JtMFG5/PxsWXYdlpbC0npmNhUuqOKLj1uEZjskA= X-Received: by 2002:a25:d84a:: with SMTP id p71mr2582970ybg.347.1596607980723; Tue, 04 Aug 2020 23:13:00 -0700 (PDT) MIME-Version: 1.0 References: <20200801170322.75218-1-jolsa@kernel.org> <20200801170322.75218-7-jolsa@kernel.org> In-Reply-To: <20200801170322.75218-7-jolsa@kernel.org> From: Andrii Nakryiko Date: Tue, 4 Aug 2020 23:12:49 -0700 Message-ID: Subject: Re: [PATCH v9 bpf-next 06/14] bpf: Remove recursion call in btf_struct_access To: Jiri Olsa Cc: 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 Content-Type: text/plain; charset="UTF-8" Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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. > > error: > bpf_log(log, "access beyond struct %s at off %u size %u\n", > -- > 2.25.4 >