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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 27 Jul 2018 09:21:30 +0100 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w6R8LTHU30605454 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 27 Jul 2018 08:21:29 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3486911C050; Fri, 27 Jul 2018 11:21:42 +0100 (BST) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CDB1C11C04A; Fri, 27 Jul 2018 11:21:41 +0100 (BST) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 27 Jul 2018 11:21:41 +0100 (BST) From: Thomas Richter To: daniel@iogearbox.net, ast@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: heiko.carstens@de.ibm.com, brueckner@linux.vnet.ibm.com, schwidefsky@de.ibm.com, jakub.kicinski@netronome.com, Thomas Richter Subject: [PATCH] perf build: Build error in libbpf missing initialization Date: Fri, 27 Jul 2018 10:21:26 +0200 X-Mailer: git-send-email 2.16.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 18072708-0028-0000-0000-000002E0FAAF X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18072708-0029-0000-0000-00002398F1EF Message-Id: <20180727082126.87530-1-tmricht@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-07-27_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807270087 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In linux-next tree compiling the perf tool with additional make flags "EXTRA_CFLAGS="-Wp,-D_FORTIFY_SOURCE=2 -O2" causes a compiler error. It is the warning 'variable may be used uninitialized' which is treated as error: I compile it using a FEDORA 28 installation, my gcc compiler version: gcc (GCC) 8.0.1 20180324 (Red Hat 8.0.1-0.20) The file that causes the error is tools/lib/bpf/libbpf.c Here is the error message: [root@p23lp27] # make V=1 EXTRA_CFLAGS="-Wp,-D_FORTIFY_SOURCE=2 -O2" [...] Makefile.config:849: No openjdk development package found, please install JDK package, e.g. openjdk-8-jdk, java-1.8.0-openjdk-devel Warning: Kernel ABI header at 'tools/include/uapi/linux/if_link.h' differs from latest version at 'include/uapi/linux/if_link.h' CC libbpf.o libbpf.c: In function ‘bpf_perf_event_read_simple’: libbpf.c:2342:6: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized] int ret; ^ cc1: all warnings being treated as errors mv: cannot stat './.libbpf.o.tmp': No such file or directory /home6/tmricht/linux-next/tools/build/Makefile.build:96: recipe for target 'libbpf.o' failed Fix this warning and add an addition check at the beginning of the while loop. Cc: Alexei Starovoitov Cc: Daniel Borkmann Suggested-by: Jakub Kicinski Signed-off-by: Thomas Richter --- tools/lib/bpf/libbpf.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 73465caa33ba..66965ca96113 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -2349,6 +2349,8 @@ bpf_perf_event_read_simple(void *mem, unsigned long size, begin = base + data_tail % size; end = base + data_head % size; + if (begin == end) + return LIBBPF_PERF_EVENT_ERROR; while (begin != end) { struct perf_event_header *ehdr; -- 2.16.4