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Message-ID: <20230412095240.181516-1-yangjihong1@huawei.com>
Date: Wed, 12 Apr 2023 09:52:40 +0000
From: Yang Jihong <yangjihong1@...wei.com>
To: <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
<mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
<jolsa@...nel.org>, <namhyung@...nel.org>, <irogers@...gle.com>,
<adrian.hunter@...el.com>, <linux-perf-users@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
CC: <yangjihong1@...wei.com>
Subject: [PATCH] perf/core: Fix perf_sample_data not properly initialized for different swevents in perf_tp_event()
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_switch -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.<timestamp> ]
# 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_switch -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.<timestamp> ]
# 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=perf prev_pid=232 prev_prio=120 prev_state=D ==> next_comm=perf next_pid=234 next_prio=120
perf 234 [000] 66.846449: sched:sched_switch: prev_comm=perf prev_pid=234 prev_prio=120 prev_state=S ==> next_comm=perf next_pid=232 next_prio=120
perf 232 [000] 66.846546: sched:sched_switch: prev_comm=perf prev_pid=232 prev_prio=120 prev_state=R ==> next_comm=perf next_pid=234 next_prio=120
perf 234 [000] 66.846606: sched:sched_switch: prev_comm=perf prev_pid=234 prev_prio=120 prev_state=S ==> next_comm=perf next_pid=232 next_prio=120
perf 232 [000] 66.846646: sched:sched_switch: prev_comm=perf prev_pid=232 prev_prio=120 prev_state=R ==> next_comm=perf next_pid=234 next_prio=120
Fixes: bb447c27a467 ("perf/core: Set data->sample_flags in perf_prepare_sample()")
Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
---
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))
+/* Note: caller must ensure flags is not NULL */
+static inline void perf_sample_data_flags_save(struct perf_sample_data *data, u64 *flags)
+{
+ *flags = data->sample_flags;
+}
+
+static inline void perf_sample_data_flags_restore(struct perf_sample_data *data, u64 flags)
+{
+ data->sample_flags = 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;
struct perf_raw_record raw = {
.frag = {
@@ -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);
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);
+ }
}
/*
--
2.30.GIT
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