From patchwork Fri May 7 05:41:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 432475 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=-17.0 required=3.0 tests=BAYES_00, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 AB7AEC433B4 for ; Fri, 7 May 2021 05:41:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8802161006 for ; Fri, 7 May 2021 05:41:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233751AbhEGFme convert rfc822-to-8bit (ORCPT ); Fri, 7 May 2021 01:42:34 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:58850 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233669AbhEGFmd (ORCPT ); Fri, 7 May 2021 01:42:33 -0400 Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 1475ZLe8028937 for ; Thu, 6 May 2021 22:41:34 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 38cswg982p-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 06 May 2021 22:41:34 -0700 Received: from intmgw001.25.frc3.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 6 May 2021 22:41:33 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 32B062ED7617; Thu, 6 May 2021 22:41:31 -0700 (PDT) From: Andrii Nakryiko To: , , , CC: , Subject: [RFC PATCH bpf-next 4/7] bpftool: stop emitting static variables in BPF skeleton Date: Thu, 6 May 2021 22:41:16 -0700 Message-ID: <20210507054119.270888-5-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210507054119.270888-1-andrii@kernel.org> References: <20210507054119.270888-1-andrii@kernel.org> X-FB-Internal: Safe X-Proofpoint-GUID: ZYNKuNgCf_h2xFL4WPr2xtS_SVh37s6l X-Proofpoint-ORIG-GUID: ZYNKuNgCf_h2xFL4WPr2xtS_SVh37s6l X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-05-07_01:2021-05-06,2021-05-07 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 mlxlogscore=999 lowpriorityscore=0 phishscore=0 mlxscore=0 bulkscore=0 impostorscore=0 clxscore=1015 suspectscore=0 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105070041 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org As discussed in [0], stop emitting static variables in BPF skeletons to avoid issues with name-conflicting static variables across multiple statically-linked BPF object files. Users using static variables to pass data between BPF programs and user-space should do a trivial one-time switch according to the following simple rules: - read-only `static volatile const` variables should be converted to `volatile const`; - read/write `static volatile` variables should just drop `static volatile` modifiers to become global variables/symbols. To better handle older Clang versions, such newly converted global variables should be explicitly initialized with a specific value or `= 0`/`= {}`, whichever is appropriate. [0] https://lore.kernel.org/bpf/CAEf4BzZo7_r-hsNvJt3w3kyrmmBJj7ghGY8+k4nvKF0KLjma=w@mail.gmail.com/T/#m664d4b0d6b31ac8b2669360e0fc2d6962e9f5ec1 Signed-off-by: Andrii Nakryiko --- tools/bpf/bpftool/gen.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index 06fee4a2910a..27dceaf66ecb 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -131,6 +131,10 @@ static int codegen_datasec_def(struct bpf_object *obj, int need_off = sec_var->offset, align_off, align; __u32 var_type_id = var->type; + /* static variables are not exposed through BPF skeleton */ + if (btf_var(var)->linkage == BTF_VAR_STATIC) + continue; + if (off > need_off) { p_err("Something is wrong for %s's variable #%d: need offset %d, already at %d.\n", sec_name, i, need_off, off);