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=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 0CC25C433DB for ; Wed, 3 Feb 2021 20:35:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4BBF64F76 for ; Wed, 3 Feb 2021 20:35:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232096AbhBCUfd convert rfc822-to-8bit (ORCPT ); Wed, 3 Feb 2021 15:35:33 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:1688 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S232027AbhBCUfc (ORCPT ); Wed, 3 Feb 2021 15:35:32 -0500 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 113KX2am026668 for ; Wed, 3 Feb 2021 12:34:51 -0800 Received: from mail.thefacebook.com ([163.114.132.120]) by m0001303.ppops.net with ESMTP id 36f3ej26mb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Wed, 03 Feb 2021 12:34:51 -0800 Received: from intmgw001.25.frc3.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:11d::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Wed, 3 Feb 2021 12:34:50 -0800 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id ECC4F2ECF298; Wed, 3 Feb 2021 12:34:46 -0800 (PST) From: Andrii Nakryiko To: , , , CC: , , Arnaldo Carvalho de Melo , Randy Dunlap Subject: [PATCH bpf-next] libbpf: stop using feature-detection Makefiles Date: Wed, 3 Feb 2021 12:34:45 -0800 Message-ID: <20210203203445.3356114-1-andrii@kernel.org> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.737 definitions=2021-02-03_08:2021-02-03,2021-02-03 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 spamscore=0 clxscore=1015 adultscore=0 suspectscore=0 mlxlogscore=999 impostorscore=0 priorityscore=1501 bulkscore=0 phishscore=0 mlxscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102030122 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Libbpf's Makefile relies on Linux tools infrastructure's feature detection framework, but libbpf's needs are very modest: it detects the presence of libelf and libz, both of which are mandatory. So it doesn't benefit much from the framework, but pays significant costs in terms of maintainability and debugging experience, when something goes wrong. The other feature detector, testing for the presernce of minimal BPF API in system headers is long obsolete as well, providing no value. So stop using feature detection and just assume the presence of libelf and libz during build time. Worst case, user will get a clear and actionable linker error, e.g.: /usr/bin/ld: cannot find -lelf On the other hand, we completely bypass recurring issues various users reported over time with false negatives of feature detection (libelf or libz not being detected, while they are actually present in the system). Cc: Arnaldo Carvalho de Melo Cc: Randy Dunlap Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/.gitignore | 1 - tools/lib/bpf/Makefile | 47 ++++------------------------------------ 2 files changed, 4 insertions(+), 44 deletions(-) diff --git a/tools/lib/bpf/.gitignore b/tools/lib/bpf/.gitignore index 8a81b3679d2b..5d4cfac671d5 100644 --- a/tools/lib/bpf/.gitignore +++ b/tools/lib/bpf/.gitignore @@ -1,7 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only libbpf_version.h libbpf.pc -FEATURE-DUMP.libbpf libbpf.so.* TAGS tags diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile index 55bd78b3496f..887a494ad5fc 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -58,28 +58,7 @@ ifndef VERBOSE VERBOSE = 0 endif -FEATURE_USER = .libbpf -FEATURE_TESTS = libelf zlib bpf -FEATURE_DISPLAY = libelf zlib bpf - INCLUDES = -I. -I$(srctree)/tools/include -I$(srctree)/tools/include/uapi -FEATURE_CHECK_CFLAGS-bpf = $(INCLUDES) - -check_feat := 1 -NON_CHECK_FEAT_TARGETS := clean TAGS tags cscope help -ifdef MAKECMDGOALS -ifeq ($(filter-out $(NON_CHECK_FEAT_TARGETS),$(MAKECMDGOALS)),) - check_feat := 0 -endif -endif - -ifeq ($(check_feat),1) -ifeq ($(FEATURES_DUMP),) -include $(srctree)/tools/build/Makefile.feature -else -include $(FEATURES_DUMP) -endif -endif export prefix libdir src obj @@ -157,7 +136,7 @@ all: fixdep all_cmd: $(CMD_TARGETS) check -$(BPF_IN_SHARED): force elfdep zdep bpfdep $(BPF_HELPER_DEFS) +$(BPF_IN_SHARED): force $(BPF_HELPER_DEFS) @(test -f ../../include/uapi/linux/bpf.h -a -f ../../../include/uapi/linux/bpf.h && ( \ (diff -B ../../include/uapi/linux/bpf.h ../../../include/uapi/linux/bpf.h >/dev/null) || \ echo "Warning: Kernel ABI header at 'tools/include/uapi/linux/bpf.h' differs from latest version at 'include/uapi/linux/bpf.h'" >&2 )) || true @@ -175,7 +154,7 @@ $(BPF_IN_SHARED): force elfdep zdep bpfdep $(BPF_HELPER_DEFS) echo "Warning: Kernel ABI header at 'tools/include/uapi/linux/if_xdp.h' differs from latest version at 'include/uapi/linux/if_xdp.h'" >&2 )) || true $(Q)$(MAKE) $(build)=libbpf OUTPUT=$(SHARED_OBJDIR) CFLAGS="$(CFLAGS) $(SHLIB_FLAGS)" -$(BPF_IN_STATIC): force elfdep zdep bpfdep $(BPF_HELPER_DEFS) +$(BPF_IN_STATIC): force $(BPF_HELPER_DEFS) $(Q)$(MAKE) $(build)=libbpf OUTPUT=$(STATIC_OBJDIR) $(BPF_HELPER_DEFS): $(srctree)/tools/include/uapi/linux/bpf.h @@ -264,34 +243,16 @@ install_pkgconfig: $(PC_FILE) install: install_lib install_pkgconfig install_headers -### Cleaning rules - -config-clean: - $(call QUIET_CLEAN, feature-detect) - $(Q)$(MAKE) -C $(srctree)/tools/build/feature/ clean >/dev/null - -clean: config-clean +clean: $(call QUIET_CLEAN, libbpf) $(RM) -rf $(CMD_TARGETS) \ *~ .*.d .*.cmd LIBBPF-CFLAGS $(BPF_HELPER_DEFS) \ $(SHARED_OBJDIR) $(STATIC_OBJDIR) \ $(addprefix $(OUTPUT), \ *.o *.a *.so *.so.$(LIBBPF_MAJOR_VERSION) *.pc) - $(call QUIET_CLEAN, core-gen) $(RM) $(OUTPUT)FEATURE-DUMP.libbpf - - -PHONY += force elfdep zdep bpfdep cscope tags +PHONY += force cscope tags force: -elfdep: - @if [ "$(feature-libelf)" != "1" ]; then echo "No libelf found"; exit 1 ; fi - -zdep: - @if [ "$(feature-zlib)" != "1" ]; then echo "No zlib found"; exit 1 ; fi - -bpfdep: - @if [ "$(feature-bpf)" != "1" ]; then echo "BPF API too old"; exit 1 ; fi - cscope: ls *.c *.h > cscope.files cscope -b -q -I $(srctree)/include -f cscope.out -- 2.24.1