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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81698C07E9D for ; Fri, 23 Sep 2022 23:06:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231239AbiIWXGQ convert rfc822-to-8bit (ORCPT ); Fri, 23 Sep 2022 19:06:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52720 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229743AbiIWXGO (ORCPT ); Fri, 23 Sep 2022 19:06:14 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 680CA1138FA for ; Fri, 23 Sep 2022 16:06:13 -0700 (PDT) Received: from pps.filterd (m0109333.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 28NM8x3l013545 for ; Fri, 23 Sep 2022 16:06:13 -0700 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3jsb1nn0n2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 23 Sep 2022 16:06:13 -0700 Received: from twshared20183.05.prn5.facebook.com (2620:10d:c085:108::4) 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 15.1.2375.31; Fri, 23 Sep 2022 16:06:12 -0700 Received: by devbig019.vll3.facebook.com (Postfix, from userid 137359) id 8264C1F46384C; Fri, 23 Sep 2022 16:06:00 -0700 (PDT) From: Andrii Nakryiko To: , , CC: , , Grant Seltzer Richman Subject: [PATCH bpf-next] libbpf: restore memory layout of bpf_object_open_opts Date: Fri, 23 Sep 2022 16:05:59 -0700 Message-ID: <20220923230559.666608-1-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-ORIG-GUID: KsMVC_w8y9GJxtpbouavGkilbk3gSddt X-Proofpoint-GUID: KsMVC_w8y9GJxtpbouavGkilbk3gSddt X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-09-23_10,2022-09-22_02,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org When attach_prog_fd field was removed in libbpf 1.0 and replaced with `long: 0` placeholder, it actually shifted all the subsequent fields by 8 byte. This is due to `long: 0` promising to adjust next field's offset to long-aligned offset. But in this case we were already long-aligned as pin_root_path is a pointer. So `long: 0` had no effect, and thus didn't feel the gap created by removed attach_prog_fd. Non-zero bitfield should have been used instead. I validated using pahole. Originally kconfig field was at offset 40. With `long: 0` it's at offset 32, which is wrong. With this change it's back at offset 40. While technically libbpf 1.0 is allowed to break backwards compatibility and applications should have been recompiled against libbpf 1.0 headers, but given how trivial it is to preserve memory layout, let's fix this. Reported-by: Grant Seltzer Richman Fixes: 146bf811f5ac ("libbpf: remove most other deprecated high-level APIs") Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index e2d8c17f2e85..eee883f007f9 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -118,7 +118,9 @@ struct bpf_object_open_opts { * auto-pinned to that path on load; defaults to "/sys/fs/bpf". */ const char *pin_root_path; - long :0; + + __u32 :32; /* stub out now removed attach_prog_fd */ + /* Additional kernel config content that augments and overrides * system Kconfig for CONFIG_xxx externs. */ -- 2.30.2