2024-06-11 05:06:42

by Ian Rogers

Subject: [PATCH v2] perf record: Ensure space for lost samples

Previous allocation didn't account for sample ID written after the
lost samples event. Switch from malloc/free to a stack allocation.

Reported-by: Milian Wolff <[email protected]>
Closes: https://lore.kernel.org/linux-perf-users/23879991.0LEYPuXRzz@milian-workstation/
Signed-off-by: Ian Rogers <[email protected]>
---
v2. Switch from union to struct and place struct in header to clearly
tie it to the MAX_ID_HDR_ENTRIES.
---
tools/lib/perf/include/perf/event.h | 6 +++++
tools/perf/builtin-record.c | 34 ++++++++---------------------
2 files changed, 15 insertions(+), 25 deletions(-)

diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index ae64090184d3..37bb7771d914 100644
--- a/tools/lib/perf/include/perf/event.h
+++ b/tools/lib/perf/include/perf/event.h
@@ -77,6 +77,12 @@ struct perf_record_lost_samples {
__u64 lost;
};

+#define MAX_ID_HDR_ENTRIES 6
+struct perf_record_lost_samples_and_ids {
+ struct perf_record_lost_samples lost;
+ __u64 sample_ids[MAX_ID_HDR_ENTRIES];
+};
+
/*
* PERF_FORMAT_ENABLED | PERF_FORMAT_RUNNING | PERF_FORMAT_ID | PERF_FORMAT_LOST
*/
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 66a3de8ac661..019305b94e5f 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1926,7 +1926,7 @@ static void __record__save_lost_samples(struct record *rec, struct evsel *evsel,
static void record__read_lost_samples(struct record *rec)
{
struct perf_session *session = rec->session;
- struct perf_record_lost_samples *lost = NULL;
+ struct perf_record_lost_samples_and_ids lost;
struct evsel *evsel;

/* there was an error during record__open */
@@ -1951,20 +1951,13 @@ static void record__read_lost_samples(struct record *rec)

if (perf_evsel__read(&evsel->core, x, y, &count) < 0) {
pr_debug("read LOST count failed\n");
- goto out;
+ return;
}

if (count.lost) {
- if (!lost) {
- lost = zalloc(sizeof(*lost) +
- session->machines.host.id_hdr_size);
- if (!lost) {
- pr_debug("Memory allocation failed\n");
- return;
- }
- lost->header.type = PERF_RECORD_LOST_SAMPLES;
- }
- __record__save_lost_samples(rec, evsel, lost,
+ memset(&lost.lost, 0, sizeof(lost));
+ lost.lost.header.type = PERF_RECORD_LOST_SAMPLES;
+ __record__save_lost_samples(rec, evsel, &lost.lost,
x, y, count.lost, 0);
}
}
@@ -1972,21 +1965,12 @@ static void record__read_lost_samples(struct record *rec)

lost_count = perf_bpf_filter__lost_count(evsel);
if (lost_count) {
- if (!lost) {
- lost = zalloc(sizeof(*lost) +
- session->machines.host.id_hdr_size);
- if (!lost) {
- pr_debug("Memory allocation failed\n");
- return;
- }
- lost->header.type = PERF_RECORD_LOST_SAMPLES;
- }
- __record__save_lost_samples(rec, evsel, lost, 0, 0, lost_count,
+ memset(&lost.lost, 0, sizeof(lost));
+ lost.lost.header.type = PERF_RECORD_LOST_SAMPLES;
+ __record__save_lost_samples(rec, evsel, &lost.lost, 0, 0, lost_count,
PERF_RECORD_MISC_LOST_SAMPLES_BPF);
}
}
-out:
- free(lost);
}

static volatile sig_atomic_t workload_exec_errno;
@@ -3198,7 +3182,7 @@ static int switch_output_setup(struct record *rec)
unsigned long val;

/*
- * If we're using --switch-output-events, then we imply its
+ * If we're using --switch-output-events, then we imply its
* --switch-output=signal, as we'll send a SIGUSR2 from the side band
* thread to its parent.
*/
--
2.45.2.505.gda0bf45e8d-goog

2024-06-11 16:06:17

by Namhyung Kim

Subject: Re: [PATCH v2] perf record: Ensure space for lost samples

Hi Ian,

On Mon, Jun 10, 2024 at 10:06 PM Ian Rogers <[email protected]> wrote:
>
> Previous allocation didn't account for sample ID written after the
> lost samples event. Switch from malloc/free to a stack allocation.
>
> Reported-by: Milian Wolff <[email protected]>
> Closes: https://lore.kernel.org/linux-perf-users/23879991.0LEYPuXRzz@milian-workstation/
> Signed-off-by: Ian Rogers <[email protected]>

Acked-by: Namhyung Kim <[email protected]>

Thanks,
Namhyung

2024-06-14 13:31:27

by Namhyung Kim

Subject: Re: [PATCH v2] perf record: Ensure space for lost samples

On Mon, 10 Jun 2024 22:06:26 -0700, Ian Rogers wrote:

> Previous allocation didn't account for sample ID written after the
> lost samples event. Switch from malloc/free to a stack allocation.
>
>

Applied to perf-tools-next, thanks!

Arnaldo, I'll resolve the conflict when I merge perf-tools later which
has the revert.

Best regards,
Namhyung