From mboxrd@z Thu Jan 1 00:00:00 1970 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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=no 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 1555CC432C0 for ; Sun, 17 Nov 2019 07:08:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD10120740 for ; Sun, 17 Nov 2019 07:08:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="HELgwWiN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725942AbfKQHIO (ORCPT ); Sun, 17 Nov 2019 02:08:14 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:27230 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725901AbfKQHIO (ORCPT ); Sun, 17 Nov 2019 02:08:14 -0500 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 xAH744gM027326 for ; Sat, 16 Nov 2019 23:08:13 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type : content-transfer-encoding; s=facebook; bh=BqhFGWKCuC9qUWVvoI9kyc+5I4v5V82hLouZtrFOQ+0=; b=HELgwWiNO47HLEimjkNIigfANBABP3M/oyz43QjuuRBBoOVn+mEuEWjm8eoTy8m0nOJm KF9QbCc7UuUYrC9Xy13leyhATITw18bvjGIbZIFH45MJ1AavbE9+mw14QkqLyMmv6yZA miWVU1eNs2RxbQ9J3R+nwuJwWLmuDRPl7SY= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 2wafqr9gqc-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Sat, 16 Nov 2019 23:08:13 -0800 Received: from 2401:db00:2120:80d4:face:0:39:0 (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Sat, 16 Nov 2019 23:08:12 -0800 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 533762EC19AE; Sat, 16 Nov 2019 23:08:11 -0800 (PST) Smtp-Origin-Hostprefix: devbig From: Andrii Nakryiko Smtp-Origin-Hostname: devbig012.ftw2.facebook.com To: , , , CC: , , Andrii Nakryiko Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH bpf-next 0/6] Add libbpf-provided extern variables support Date: Sat, 16 Nov 2019 23:08:01 -0800 Message-ID: <20191117070807.251360-1-andriin@fb.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-11-17_01:2019-11-15,2019-11-16 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 phishscore=0 clxscore=1015 mlxscore=0 malwarescore=0 suspectscore=9 impostorscore=0 mlxlogscore=999 bulkscore=0 adultscore=0 spamscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1911170066 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org It's often important for BPF program to know kernel version or some speci= fic config values (e.g., CONFIG_HZ to convert jiffies to seconds) and change = or adjust program logic based on their values. As of today, any such need ha= s to be resolved by recompiling BPF program for specific kernel and kernel configuration. In practice this is usually achieved by using BCC and its embedded LLVM/Clang. With such set up #ifdef CONFIG_XXX and similar compile-time constructs allow to deal with kernel varieties. With CO-RE (Compile Once =E2=80=93 Run Everywhere) approach, this is not = an option, unfortunately. All such logic variations have to be done as a normal C language constructs (i.e., if/else, variables, etc), not a preprocessor directives. This patch series add support for such advanced scenarios thr= ough C extern variables. These extern variables will be recognized by libbpf a= nd supplied through extra .extern internal map, similarly to global data. Th= is .extern map is read-only, which allows BPF verifier to track its content precisely as constants. That gives an opportunity to have pre-compiled BP= F program, which can potentially use BPF functionality (e.g., BPF helpers) = or kernel features (types, fields, etc), that are available only on a subset= of targeted kernels, while effectively eleminating (through verifier's dead = code detection) such unsupported functionality for other kernels (typically, o= lder versions). Patch #5 contains all the details. Patch #5 explicitly tests a scenario of using unsupported BPF helper, to validate the approach. As part of this patch set, libbpf also allows usage of initialized global (non-static) variables, which provides better Clang semantics, which is c= loser and better aligned witht kernel vs userspace BPF map contents sharing. Outline of the patch set: - patches #1-#3 do some preliminary refactorings of libbpf relocation log= ic and some more clean ups; - patch #4 allows non-static variables and converts few tests to use them= ; - patch #5 adds support for externs to libbpf; - patch #6 adds tests for externs. Andrii Nakryiko (6): selftests/bpf: ensure no DWARF relocations for BPF object files libbpf: refactor relocation handling libbpf: fix various errors and warning reported by checkpatch.pl libbpf: support initialized global variables libbpf: support libbpf-provided extern variables selftests/bpf: add tests for libbpf-provided externs tools/lib/bpf/Makefile | 17 +- tools/lib/bpf/libbpf.c | 758 +++++++++++++----- tools/lib/bpf/libbpf.h | 8 +- tools/testing/selftests/bpf/Makefile | 4 +- .../selftests/bpf/prog_tests/core_extern.c | 186 +++++ .../selftests/bpf/progs/test_core_extern.c | 43 + .../bpf/progs/test_core_reloc_arrays.c | 4 +- .../progs/test_core_reloc_bitfields_direct.c | 4 +- .../progs/test_core_reloc_bitfields_probed.c | 4 +- .../bpf/progs/test_core_reloc_existence.c | 4 +- .../bpf/progs/test_core_reloc_flavors.c | 4 +- .../bpf/progs/test_core_reloc_ints.c | 4 +- .../bpf/progs/test_core_reloc_kernel.c | 4 +- .../bpf/progs/test_core_reloc_misc.c | 4 +- .../bpf/progs/test_core_reloc_mods.c | 4 +- .../bpf/progs/test_core_reloc_nesting.c | 4 +- .../bpf/progs/test_core_reloc_primitives.c | 4 +- .../bpf/progs/test_core_reloc_ptr_as_arr.c | 4 +- .../bpf/progs/test_core_reloc_size.c | 4 +- 19 files changed, 820 insertions(+), 248 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/core_extern.c create mode 100644 tools/testing/selftests/bpf/progs/test_core_extern.c --=20 2.17.1