From patchwork Thu Nov 5 04:33:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 11883163 X-Patchwork-Delegate: bpf@iogearbox.net 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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 C45B3C4741F for ; Thu, 5 Nov 2020 04:34:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 73C7C2083B for ; Thu, 5 Nov 2020 04:34:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604550870; bh=p9I8jJPRbqjKPJuJb+ffQuLcdMdw4hSH/CBDPa1m6CY=; h=From:To:CC:Subject:Date:In-Reply-To:References:List-ID:From; b=rwcAKxbFk2+fzLBc3Ho0D4gktsezBYqXaqFk5ZAOsVEwo6KoVLDHfUgKKjhenK/0p 0iahKU+fJV3jVTkv4YqW5EDM5ApAHiy/1eyLP9JeHUoP09LxlVLUYwMLPopDMwF5Aj vEt/1WqqtAHqBtOOb5hM32q2vbIEuGVqAfbtkPcw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731657AbgKEEe3 convert rfc822-to-8bit (ORCPT ); Wed, 4 Nov 2020 23:34:29 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:29728 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731587AbgKEEe3 (ORCPT ); Wed, 4 Nov 2020 23:34:29 -0500 Received: from pps.filterd (m0148461.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0A54SsZR026866 for ; Wed, 4 Nov 2020 20:34:28 -0800 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 34kmux6eqn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Wed, 04 Nov 2020 20:34:28 -0800 Received: from intmgw004.08.frc2.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Wed, 4 Nov 2020 20:34:27 -0800 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 637E02EC8E04; Wed, 4 Nov 2020 20:34:23 -0800 (PST) From: Andrii Nakryiko To: , , , CC: , , Song Liu Subject: [PATCH v2 bpf-next 09/11] libbpf: accomodate DWARF/compiler bug with duplicated identical arrays Date: Wed, 4 Nov 2020 20:33:59 -0800 Message-ID: <20201105043402.2530976-10-andrii@kernel.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20201105043402.2530976-1-andrii@kernel.org> References: <20201105043402.2530976-1-andrii@kernel.org> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-05_01:2020-11-05,2020-11-05 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 clxscore=1034 bulkscore=0 impostorscore=0 malwarescore=0 adultscore=0 suspectscore=8 mlxscore=0 mlxlogscore=643 priorityscore=1501 phishscore=0 spamscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011050032 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net In some cases compiler seems to generate distinct DWARF types for identical arrays within the same CU. That seems like a bug, but it's already out there and breaks type graph equivalence checks, so accommodate it anyway by checking for identical arrays, regardless of their type ID. Acked-by: Song Liu Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/btf.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 8d04d9becb67..2d0d064c6d31 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -3785,6 +3785,19 @@ static inline __u16 btf_fwd_kind(struct btf_type *t) return btf_kflag(t) ? BTF_KIND_UNION : BTF_KIND_STRUCT; } +/* Check if given two types are identical ARRAY definitions */ +static int btf_dedup_identical_arrays(struct btf_dedup *d, __u32 id1, __u32 id2) +{ + struct btf_type *t1, *t2; + + t1 = btf_type_by_id(d->btf, id1); + t2 = btf_type_by_id(d->btf, id2); + if (!btf_is_array(t1) || !btf_is_array(t2)) + return 0; + + return btf_equal_array(t1, t2); +} + /* * Check equivalence of BTF type graph formed by candidate struct/union (we'll * call it "candidate graph" in this description for brevity) to a type graph @@ -3895,8 +3908,18 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id, canon_id = resolve_fwd_id(d, canon_id); hypot_type_id = d->hypot_map[canon_id]; - if (hypot_type_id <= BTF_MAX_NR_TYPES) - return hypot_type_id == cand_id; + if (hypot_type_id <= BTF_MAX_NR_TYPES) { + /* In some cases compiler will generate different DWARF types + * for *identical* array type definitions and use them for + * different fields within the *same* struct. This breaks type + * equivalence check, which makes an assumption that candidate + * types sub-graph has a consistent and deduped-by-compiler + * types within a single CU. So work around that by explicitly + * allowing identical array types here. + */ + return hypot_type_id == cand_id || + btf_dedup_identical_arrays(d, hypot_type_id, cand_id); + } if (btf_dedup_hypot_map_add(d, canon_id, cand_id)) return -ENOMEM;