From nobody Wed Feb 11 21:31:07 2026 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 924D7C77B6E for ; Wed, 12 Apr 2023 09:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230157AbjDLJyj (ORCPT ); Wed, 12 Apr 2023 05:54:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41060 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229586AbjDLJyg (ORCPT ); Wed, 12 Apr 2023 05:54:36 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9B39526BE; Wed, 12 Apr 2023 02:54:34 -0700 (PDT) Received: from kwepemm600003.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4PxHyp38YFz16Ny5; Wed, 12 Apr 2023 17:50:58 +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, 12 Apr 2023 17:54:31 +0800 From: Yang Jihong To: , , , , , , , , , , CC: Subject: [PATCH] perf/core: Fix perf_sample_data not properly initialized for different swevents in perf_tp_event() Date: Wed, 12 Apr 2023 09:52:40 +0000 Message-ID: <20230412095240.181516-1-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: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm600003.china.huawei.com (7.193.23.202) X-CFilter-Loop: Reflected 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: Add perf_sample_data_flags_{save, restore} helpers to save and restore sample_flags when processing different swevents 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 --- include/linux/perf_event.h | 11 +++++++++++ kernel/events/core.c | 13 ++++++++++++- 2 files changed, 23 insertions(+), 1 deletion(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d5628a7b5eaa..7499bd3a2ed5 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1185,6 +1185,17 @@ struct perf_sample_data { PERF_MEM_S(LOCK, NA) |\ PERF_MEM_S(TLB, NA)) =20 +/* Note: caller must ensure flags is not NULL */ +static inline void perf_sample_data_flags_save(struct perf_sample_data *da= ta, u64 *flags) +{ + *flags =3D data->sample_flags; +} + +static inline void perf_sample_data_flags_restore(struct perf_sample_data = *data, u64 flags) +{ + data->sample_flags =3D flags; +} + static inline void perf_sample_data_init(struct perf_sample_data *data, u64 addr, u64 period) { diff --git a/kernel/events/core.c b/kernel/events/core.c index 435815d3be3f..ea1fb63a6037 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10136,6 +10136,7 @@ void perf_tp_event(u16 event_type, u64 count, void = *record, int entry_size, { struct perf_sample_data data; struct perf_event *event; + u64 sample_flags; =20 struct perf_raw_record raw =3D { .frag =3D { @@ -10150,8 +10151,18 @@ void perf_tp_event(u16 event_type, u64 count, void= *record, int entry_size, 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)) { + /* + * sample_flags may be modified in perf_event_output_* + * (see perf_prepare_sample). For different swevents, + * use the same on-stack perf_sample_data, therefore, + * need to save samle_flags, and restore it + * after perf_swevent_event. + */ + perf_sample_data_flags_save(&data, &sample_flags); perf_swevent_event(event, count, &data, regs); + perf_sample_data_flags_restore(&data, sample_flags); + } } =20 /* --=20 2.30.GIT