From patchwork Wed Mar 17 03:12:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 12144629 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=-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=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 25E42C43381 for ; Wed, 17 Mar 2021 03:14:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E818F64F9C for ; Wed, 17 Mar 2021 03:14:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229608AbhCQDNh convert rfc822-to-8bit (ORCPT ); Tue, 16 Mar 2021 23:13:37 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:7134 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229660AbhCQDNV (ORCPT ); Tue, 16 Mar 2021 23:13:21 -0400 Received: from pps.filterd (m0001303.ppops.net [127.0.0.1]) by m0001303.ppops.net (8.16.0.43/8.16.0.43) with SMTP id 12H37GNA006095 for ; Tue, 16 Mar 2021 20:13:21 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by m0001303.ppops.net with ESMTP id 37armw5kjr-15 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 16 Mar 2021 20:13:21 -0700 Received: from intmgw001.37.frc1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) 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 20:13:07 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 628712ED23D6; Tue, 16 Mar 2021 20:13:01 -0700 (PDT) From: Andrii Nakryiko To: , , , CC: , Subject: [PATCH v2 bpf-next 1/4] bpftool: generate NULL definition in vmlinux.h Date: Tue, 16 Mar 2021 20:12:54 -0700 Message-ID: <20210317031257.846314-2-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210317031257.846314-1-andrii@kernel.org> References: <20210317031257.846314-1-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 adultscore=0 spamscore=0 bulkscore=0 malwarescore=0 suspectscore=0 clxscore=1015 mlxlogscore=999 phishscore=0 lowpriorityscore=0 mlxscore=0 impostorscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2103170024 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net 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] #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");