From patchwork Wed Jul 8 01:53:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 1324854 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: incoming-bpf@patchwork.ozlabs.org Delivered-To: patchwork-incoming-bpf@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=bpf-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=reject dis=none) header.from=fb.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=fb.com header.i=@fb.com header.a=rsa-sha256 header.s=facebook header.b=QzcRe1Dj; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4B1j5N0MxJz9sQt for ; Wed, 8 Jul 2020 11:53:44 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728184AbgGHBxm (ORCPT ); Tue, 7 Jul 2020 21:53:42 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:35366 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729204AbgGHBxm (ORCPT ); Tue, 7 Jul 2020 21:53:42 -0400 Received: from pps.filterd (m0109332.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0681oxmi022189 for ; Tue, 7 Jul 2020 18:53:40 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=uKe0Rqu/r8EUcwlq4+3OEpaNXECRyxw+e5bKJErRnsE=; b=QzcRe1DjlYYJE49Zv+h3nRyY6vgkOSynIKD4hps+eg57QBz2XmLSq8rz7oCtJPbRBBPS 2uhPIAs2q5HR7Vw5naC3BaHHUUoxBR1aLdjhXAfDUX45L5pcX5LW3q7mbvlJuBG8FJP+ Udbkl8NQga+bHnhwIdsgMnUgs01Zx8MV+KM= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 324tug2v52-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 07 Jul 2020 18:53:40 -0700 Received: from intmgw004.03.ash8.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::d) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Tue, 7 Jul 2020 18:53:39 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 65EA52EC39F5; Tue, 7 Jul 2020 18:53:31 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Andrii Nakryiko Smtp-Origin-Hostname: devbig012.ftw2.facebook.com To: , , , CC: , , Andrii Nakryiko , Matthew Lim Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH bpf-next 5/6] libbpf: handle missing BPF_OBJ_GET_INFO_BY_FD gracefully in perf_buffer Date: Tue, 7 Jul 2020 18:53:17 -0700 Message-ID: <20200708015318.3827358-6-andriin@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200708015318.3827358-1-andriin@fb.com> References: <20200708015318.3827358-1-andriin@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-07_15:2020-07-07,2020-07-07 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 cotscore=-2147483648 priorityscore=1501 lowpriorityscore=0 suspectscore=9 clxscore=1015 spamscore=0 malwarescore=0 phishscore=0 adultscore=0 mlxlogscore=999 impostorscore=0 bulkscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007080010 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org perf_buffer__new() is relying on BPF_OBJ_GET_INFO_BY_FD availability for few sanity checks. OBJ_GET_INFO for maps is actually much more recent feature than perf_buffer support itself, so this causes unnecessary problems on old kernels before BPF_OBJ_GET_INFO_BY_FD was added. This patch makes those sanity checks optional and just assumes best if command is not supported. If user specified something incorrectly (e.g., wrong map type), kernel will reject it later anyway, except user won't get a nice explanation as to why it failed. This seems like a good trade off for supporting perf_buffer on old kernels. Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index b4f50d12f51f..6f86b57a7e24 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -8587,7 +8587,7 @@ static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt, struct perf_buffer_params *p) { const char *online_cpus_file = "/sys/devices/system/cpu/online"; - struct bpf_map_info map = {}; + struct bpf_map_info map; char msg[STRERR_BUFSIZE]; struct perf_buffer *pb; bool *online = NULL; @@ -8600,19 +8600,28 @@ static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt, return ERR_PTR(-EINVAL); } + /* best-effort sanity checks */ + memset(&map, 0, sizeof(map)); map_info_len = sizeof(map); err = bpf_obj_get_info_by_fd(map_fd, &map, &map_info_len); if (err) { err = -errno; - pr_warn("failed to get map info for map FD %d: %s\n", - map_fd, libbpf_strerror_r(err, msg, sizeof(msg))); - return ERR_PTR(err); - } - - if (map.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) { - pr_warn("map '%s' should be BPF_MAP_TYPE_PERF_EVENT_ARRAY\n", - map.name); - return ERR_PTR(-EINVAL); + /* if BPF_OBJ_GET_INFO_BY_FD is supported, will return + * -EBADFD, -EFAULT, or -E2BIG on real error + */ + if (err != -EINVAL) { + pr_warn("failed to get map info for map FD %d: %s\n", + map_fd, libbpf_strerror_r(err, msg, sizeof(msg))); + return ERR_PTR(err); + } + pr_debug("failed to get map info for FD %d; API not supported? Ignoring...\n", + map_fd); + } else { + if (map.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) { + pr_warn("map '%s' should be BPF_MAP_TYPE_PERF_EVENT_ARRAY\n", + map.name); + return ERR_PTR(-EINVAL); + } } pb = calloc(1, sizeof(*pb)); @@ -8644,7 +8653,7 @@ static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt, err = pb->cpu_cnt; goto error; } - if (map.max_entries < pb->cpu_cnt) + if (map.max_entries && map.max_entries < pb->cpu_cnt) pb->cpu_cnt = map.max_entries; }