From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C89F41C04 for ; Tue, 9 May 2023 06:55:47 +0000 (UTC) Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com [67.231.153.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 136914EE3 for ; Mon, 8 May 2023 23:55:45 -0700 (PDT) Received: from pps.filterd (m0148460.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 348NkR5i023803 for ; Mon, 8 May 2023 23:55:45 -0700 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3qf78r3cyy-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 08 May 2023 23:55:44 -0700 Received: from twshared6687.46.prn1.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:21d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Mon, 8 May 2023 23:55:23 -0700 Received: by devbig019.vll3.facebook.com (Postfix, from userid 137359) id 9878A304D2F7A; Mon, 8 May 2023 23:55:03 -0700 (PDT) From: Andrii Nakryiko To: , , , CC: , , Lennart Poettering Subject: [PATCH bpf-next] libbpf: fix offsetof() and container_of() to work with CO-RE Date: Mon, 8 May 2023 23:55:02 -0700 Message-ID: <20230509065502.2306180-1-andrii@kernel.org> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-GUID: DWClpUxAlMypFAv7GB5EyA29vpuyUMAJ X-Proofpoint-ORIG-GUID: DWClpUxAlMypFAv7GB5EyA29vpuyUMAJ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-05-09_04,2023-05-05_01,2023-02-09_01 X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net It seems like __builtin_offset() doesn't preserve CO-RE field relocations properly. So if offsetof() macro is defined through __builtin_offset(), CO-RE-enabled BPF code using container_of() will be subtly and silently broken. To avoid this problem, redefine offsetof() and container_of() in the form that works with CO-RE relocations more reliably. Fixes: 5fbc220862fc ("tools/libpf: Add offsetof/container_of macro in bpf= _helpers.h") Reported-by: Lennart Poettering Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/bpf_helpers.h | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 929a3baca8ef..bbab9ad9dc5a 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -77,16 +77,21 @@ /* * Helper macros to manipulate data structures */ -#ifndef offsetof -#define offsetof(TYPE, MEMBER) ((unsigned long)&((TYPE *)0)->MEMBER) -#endif -#ifndef container_of + +/* offsetof() definition that uses __builtin_offset() might not preserve= field + * offset CO-RE relocation properly, so force-redefine offsetof() using + * old-school approach which works with CO-RE correctly + */ +#undef offsetof +#define offsetof(type, member) ((unsigned long)&((type *)0)->member) + +/* redefined container_of() to ensure we use the above offsetof() macro = */ +#undef container_of #define container_of(ptr, type, member) \ ({ \ void *__mptr =3D (void *)(ptr); \ ((type *)(__mptr - offsetof(type, member))); \ }) -#endif =20 /* * Compiler (optimization) barrier. --=20 2.34.1