From patchwork Wed Mar 17 03:03:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 403803 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 9A4C8C4332D for ; Wed, 17 Mar 2021 03:04:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6766064FA8 for ; Wed, 17 Mar 2021 03:04:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229919AbhCQDDx convert rfc822-to-8bit (ORCPT ); Tue, 16 Mar 2021 23:03:53 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:33562 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229657AbhCQDDV (ORCPT ); Tue, 16 Mar 2021 23:03:21 -0400 Received: from pps.filterd (m0044012.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 12H30XwD013999 for ; Tue, 16 Mar 2021 20:03:21 -0700 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 37b3brstty-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 16 Mar 2021 20:03:21 -0700 Received: from intmgw006.03.ash8.facebook.com (2620:10d:c085:108::4) by mail.thefacebook.com (2620:10d:c085:11d::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 16 Mar 2021 20:03:20 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id AAC422ED23D6; Tue, 16 Mar 2021 20:03:18 -0700 (PDT) From: Andrii Nakryiko To: , , , CC: , Subject: [PATCH bpf-next 1/4] bpftool: generate NULL definition in vmlinux.h Date: Tue, 16 Mar 2021 20:03:09 -0700 Message-ID: <20210317030312.802233-2-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210317030312.802233-1-andrii@kernel.org> References: <20210317030312.802233-1-andrii@kernel.org> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.761 definitions=2021-03-16_09:2021-03-16,2021-03-16 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 mlxlogscore=999 suspectscore=0 malwarescore=0 impostorscore=0 mlxscore=0 spamscore=0 clxscore=1015 bulkscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2103170023 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Given that vmlinux.h is not compatible with headers like stdint.h, NULL poses an annoying problem: it is defined as #define, so is not captured in BTF, so is not emitted into vmlinux.h. This leads to users either sticking to explicit 0, or defining their own NULL (as progs/skb_pkt_end.c does). It's pretty trivial for bpftool to generate NULL definition, though, so let's just do that. This might cause compilation warning for existing BPF applications: progs/skb_pkt_end.c:7:9: warning: 'NULL' macro redefined [-Wmacro-redefined] progs/skb_pkt_end.c:7:9: error: 'NULL' macro redefined [-Werror,-Wmacro-redefined] #define NULL 0 ^ /tmp/linux/tools/testing/selftests/bpf/tools/include/vmlinux.h:4:9: note: previous definition is here #define NULL ((void *)0) ^ It is trivial to fix, though, so long-term benefits outweight temporary inconveniences. Signed-off-by: Andrii Nakryiko --- tools/bpf/bpftool/btf.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index 62953bbf68b4..ff6a76632873 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -405,6 +405,8 @@ static int dump_btf_c(const struct btf *btf, printf("#ifndef __VMLINUX_H__\n"); printf("#define __VMLINUX_H__\n"); printf("\n"); + printf("#define NULL ((void *)0)\n"); + printf("\n"); printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n"); printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n"); printf("#endif\n\n");