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Mon, 23 Dec 2024 13:58:26 GMT Received: from smtprelay07.fra02v.mail.ibm.com ([9.218.2.229]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 43p8cy5yux-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Dec 2024 13:58:26 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay07.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 4BNDwM9b65274184 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 23 Dec 2024 13:58:22 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5173620043; Mon, 23 Dec 2024 13:58:22 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A19462004B; Mon, 23 Dec 2024 13:58:16 +0000 (GMT) Received: from localhost.localdomain (unknown [9.61.252.112]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 23 Dec 2024 13:58:16 +0000 (GMT) From: Athira Rajeev To: acme@kernel.org, jolsa@kernel.org, adrian.hunter@intel.com, irogers@google.com, namhyung@kernel.org, hbathini@linux.ibm.com Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, maddy@linux.ibm.com, atrajeev@linux.vnet.ibm.com, kjain@linux.ibm.com, disgoel@linux.vnet.ibm.com Subject: [PATCH] tools/perf: Fix segfault during perf record --off-cpu when debuginfo is not enabled Date: Mon, 23 Dec 2024 19:28:13 +0530 Message-Id: <20241223135813.8175-1-atrajeev@linux.vnet.ibm.com> X-Mailer: git-send-email 2.35.1 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: _Usv8j7BfTmHTlu8xyb9b-9efpx3QpCE X-Proofpoint-ORIG-GUID: joqh_Ar9x7orU_mJvjEJVY4aRvvpwQBU X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 impostorscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 phishscore=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 spamscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2412230121 When kernel is built without debuginfo, running perf record with --off-cpu results in segfault as below: ./perf record --off-cpu -e dummy sleep 1 libbpf: kernel BTF is missing at '/sys/kernel/btf/vmlinux', was CONFIG_DEBUG_INFO_BTF enabled? libbpf: failed to find '.BTF' ELF section in /lib/modules/6.13.0-rc3+/build/vmlinux libbpf: failed to find valid kernel BTF Segmentation fault (core dumped) The backtrace pointed to: #0 0x00000000100fb17c in btf.type_cnt () #1 0x00000000100fc1a8 in btf_find_by_name_kind () #2 0x00000000100fc38c in btf.find_by_name_kind () #3 0x00000000102ee3ac in off_cpu_prepare () #4 0x000000001002f78c in cmd_record () #5 0x00000000100aee78 in run_builtin () #6 0x00000000100af3e4 in handle_internal_command () #7 0x000000001001004c in main () Code sequence is: static void check_sched_switch_args(void) { struct btf *btf = btf__load_vmlinux_btf(); const struct btf_type *t1, *t2, *t3; u32 type_id; type_id = btf__find_by_name_kind(btf, "btf_trace_sched_switch", BTF_KIND_TYPEDEF); btf__load_vmlinux_btf fails when CONFIG_DEBUG_INFO_BTF is not enabled. Here bpf__find_by_name_kind calls btf__type_cnt with NULL btf value and results in segfault. To fix this, add a check to see if btf is not NULL before invoking bpf__find_by_name_kind Signed-off-by: Athira Rajeev --- tools/perf/util/bpf_off_cpu.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c index a590a8ac1f9d..4269b41d1771 100644 --- a/tools/perf/util/bpf_off_cpu.c +++ b/tools/perf/util/bpf_off_cpu.c @@ -100,6 +100,11 @@ static void check_sched_switch_args(void) const struct btf_type *t1, *t2, *t3; u32 type_id; + if (!btf) { + pr_debug("Missing btf, check if CONFIG_DEBUG_INFO_BTF is enabled\n"); + goto cleanup; + } + type_id = btf__find_by_name_kind(btf, "btf_trace_sched_switch", BTF_KIND_TYPEDEF); if ((s32)type_id < 0) -- 2.43.5