From patchwork Wed Jul 8 01:53:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 1324850 Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@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=netdev-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=CsLaUozC; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4B1j554L85z9sSt for ; Wed, 8 Jul 2020 11:53:29 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729096AbgGHBx2 (ORCPT ); Tue, 7 Jul 2020 21:53:28 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:30678 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728676AbgGHBx0 (ORCPT ); Tue, 7 Jul 2020 21:53:26 -0400 Received: from pps.filterd (m0148461.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0681r0Mr023096 for ; Tue, 7 Jul 2020 18:53:25 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=facebook; bh=aLozRH8QA8pa4wgTxRX8nO0d/fW5eY/X566EgGILmBA=; b=CsLaUozC3MJp3RAZ3haQDa0cVD1Wa1JGdOtewo8f7N4kBpFN0YzVOGPpEJKR2ey7KRFD iy2bsZ3A6vwJEXFonRyvubqjqA54X2YUO/xn9ROmx0UzwI5AZh20wocCJVQPP3VKCQF3 g/TXOnpupiechycuSxTbSe0hlgCn15TfBSk= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 3239rs4xdt-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 07 Jul 2020 18:53:25 -0700 Received: from intmgw004.03.ash8.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::e) 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 18:53:23 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 844622EC39F5; Tue, 7 Jul 2020 18:53:20 -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 0/6] Improve libbpf support of old kernels Date: Tue, 7 Jul 2020 18:53:12 -0700 Message-ID: <20200708015318.3827358-1-andriin@fb.com> X-Mailer: git-send-email 2.24.1 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 mlxlogscore=685 mlxscore=0 suspectscore=8 clxscore=1015 impostorscore=0 adultscore=0 malwarescore=0 cotscore=-2147483648 lowpriorityscore=0 phishscore=0 spamscore=0 bulkscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007080010 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This patch set improves libbpf's support of old kernels, missing features like BTF support, global variables support, etc. Most critical one is a silent drop of CO-RE relocations if libbpf fails to load BTF (despite sanitization efforts). This is frequently the case for kernels that have no BTF support whatsoever. There are still useful BPF applications that could work on such kernels and do rely on CO-RE. To that end, this series revamps the way BTF is handled in libbpf. Failure to load BTF into kernel doesn't prevent libbpf from using BTF in its full capability (e.g., for CO-RE relocations) internally. Another issue that was identified was reliance of perf_buffer__new() on BPF_OBJ_GET_INFO_BY_FD command, which is more recent that perf_buffer support itself. Furthermore, BPF_OBJ_GET_INFO_BY_FD is needed just for some sanity checks to provide better user errors, so could be safely omitted if kernel doesn't provide it. Perf_buffer selftest was adjusted to use skeleton, instead of bpf_prog_load(). The latter uses BPF_F_TEST_RND_HI32 flag, which is a relatively recent addition and unnecessary fails selftest in libbpf's Travis CI tests. By using skeleton we both get a shorter selftest and it work on pretty ancient kernels, giving better libbpf test coverage. One new selftest was added that relies on basic CO-RE features, but otherwise doesn't expect any recent features (like global variables) from kernel. Again, it's good to have better coverage of old kernels in libbpf testing. Cc: Matthew Lim Andrii Nakryiko (6): libbpf: make BTF finalization strict libbpf: add btf__set_fd() for more control over loaded BTF FD libbpf: improve BTF sanitization handling selftests/bpf: add test relying only on CO-RE and no recent kernel features libbpf: handle missing BPF_OBJ_GET_INFO_BY_FD gracefully in perf_buffer selftests/bpf: switch perf_buffer test to tracepoint and skeleton tools/lib/bpf/btf.c | 7 +- tools/lib/bpf/btf.h | 1 + tools/lib/bpf/libbpf.c | 150 ++++++++++-------- tools/lib/bpf/libbpf.map | 1 + .../selftests/bpf/prog_tests/core_retro.c | 33 ++++ .../selftests/bpf/prog_tests/perf_buffer.c | 42 ++--- .../selftests/bpf/progs/test_core_retro.c | 30 ++++ .../selftests/bpf/progs/test_perf_buffer.c | 4 +- 8 files changed, 167 insertions(+), 101 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/core_retro.c create mode 100644 tools/testing/selftests/bpf/progs/test_core_retro.c