From nobody Wed Dec 17 15:10:38 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56190C6FD18 for ; Wed, 19 Apr 2023 02:50:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231643AbjDSCum (ORCPT ); Tue, 18 Apr 2023 22:50:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231349AbjDSCuj (ORCPT ); Tue, 18 Apr 2023 22:50:39 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 05EC6E66; Tue, 18 Apr 2023 19:50:33 -0700 (PDT) Received: from kwepemm600003.china.huawei.com (unknown [7.193.23.202]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Q1QGh6HrjzsRNd; Wed, 19 Apr 2023 10:49:00 +0800 (CST) Received: from localhost.localdomain (10.67.174.95) by kwepemm600003.china.huawei.com (7.193.23.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Wed, 19 Apr 2023 10:50:30 +0800 From: Yang Jihong To: , , , , , , , , , , CC: Subject: [PATCH v2] perf/core: Fix perf_sample_data not properly initialized for different swevents in perf_tp_event() Date: Wed, 19 Apr 2023 02:48:32 +0000 Message-ID: <20230419024832.181874-1-yangjihong1@huawei.com> X-Mailer: git-send-email 2.30.GIT MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.67.174.95] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemm600003.china.huawei.com (7.193.23.202) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" data->sample_flags may be modified in perf_prepare_sample(), in perf_tp_event(), different swevents use the same on-stack perf_sample_data, the previous swevent may change sample_flags in perf_prepare_sample(), as a result, some members of perf_sample_data are not correctly initialized when next swevent_event preparing sample (for example data->id, the value varies according to swevent). A simple scenario triggers this problem is as follows: # perf record -e sched:sched_switch --switch-output-event sched:sched_swi= tch -a sleep 1 [ perf record: dump data: Woken up 0 times ] [ perf record: Dump perf.data.2023041209014396 ] [ perf record: dump data: Woken up 0 times ] [ perf record: Dump perf.data.2023041209014662 ] [ perf record: dump data: Woken up 0 times ] [ perf record: Dump perf.data.2023041209014910 ] [ perf record: Woken up 0 times to write data ] [ perf record: Dump perf.data.2023041209015164 ] [ perf record: Captured and wrote 0.069 MB perf.data. ] # ls -l total 860 -rw------- 1 root root 95694 Apr 12 09:01 perf.data.2023041209014396 -rw------- 1 root root 606430 Apr 12 09:01 perf.data.2023041209014662 -rw------- 1 root root 82246 Apr 12 09:01 perf.data.2023041209014910 -rw------- 1 root root 82342 Apr 12 09:01 perf.data.2023041209015164 # perf script -i perf.data.2023041209014396 0x11d58 [0x80]: failed to process type: 9 [Bad address] Solution: Re-initialize perf_sample_data before processing different sweven= ts. After fix: # perf record -e sched:sched_switch --switch-output-event sched:sched_swi= tch -a sleep 1 [ perf record: dump data: Woken up 0 times ] [ perf record: Dump perf.data.2023041209442259 ] [ perf record: dump data: Woken up 0 times ] [ perf record: Dump perf.data.2023041209442514 ] [ perf record: dump data: Woken up 0 times ] [ perf record: Dump perf.data.2023041209442760 ] [ perf record: Woken up 0 times to write data ] [ perf record: Dump perf.data.2023041209443003 ] [ perf record: Captured and wrote 0.069 MB perf.data. ] # ls -l total 864 -rw------- 1 root root 100166 Apr 12 09:44 perf.data.2023041209442259 -rw------- 1 root root 606438 Apr 12 09:44 perf.data.2023041209442514 -rw------- 1 root root 82246 Apr 12 09:44 perf.data.2023041209442760 -rw------- 1 root root 82342 Apr 12 09:44 perf.data.2023041209443003 # perf script -i perf.data.2023041209442259 | head -n 5 perf 232 [000] 66.846217: sched:sched_switch: prev_comm= =3Dperf prev_pid=3D232 prev_prio=3D120 prev_state=3DD =3D=3D> next_comm=3Dp= erf next_pid=3D234 next_prio=3D120 perf 234 [000] 66.846449: sched:sched_switch: prev_comm= =3Dperf prev_pid=3D234 prev_prio=3D120 prev_state=3DS =3D=3D> next_comm=3Dp= erf next_pid=3D232 next_prio=3D120 perf 232 [000] 66.846546: sched:sched_switch: prev_comm= =3Dperf prev_pid=3D232 prev_prio=3D120 prev_state=3DR =3D=3D> next_comm=3Dp= erf next_pid=3D234 next_prio=3D120 perf 234 [000] 66.846606: sched:sched_switch: prev_comm= =3Dperf prev_pid=3D234 prev_prio=3D120 prev_state=3DS =3D=3D> next_comm=3Dp= erf next_pid=3D232 next_prio=3D120 perf 232 [000] 66.846646: sched:sched_switch: prev_comm= =3Dperf prev_pid=3D232 prev_prio=3D120 prev_state=3DR =3D=3D> next_comm=3Dp= erf next_pid=3D234 next_prio=3D120 Fixes: bb447c27a467 ("perf/core: Set data->sample_flags in perf_prepare_sam= ple()") Signed-off-by: Yang Jihong --- kernel/events/core.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 435815d3be3f..6c4356ad453f 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10144,14 +10144,22 @@ void perf_tp_event(u16 event_type, u64 count, voi= d *record, int entry_size, }, }; =20 - perf_sample_data_init(&data, 0, 0); - perf_sample_save_raw_data(&data, &raw); - perf_trace_buf_update(record, event_type); =20 hlist_for_each_entry_rcu(event, head, hlist_entry) { - if (perf_tp_event_match(event, &data, regs)) + if (perf_tp_event_match(event, &data, regs)) { + /* + * Here use the same on-stack perf_sample_data, + * some members in data are event-specific and + * need to be re-computed for different sweveents. + * Re-initialize data->sample_flags each time safely + * to avoid the problem that next event skips preparing + * data because data->sample_flags is set. + */ + perf_sample_data_init(&data, 0, 0); + perf_sample_save_raw_data(&data, &raw); perf_swevent_event(event, count, &data, regs); + } } =20 /* --=20 2.30.GIT