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 <milian.wolff@kdab.com>
Closes: https://lore.kernel.org/linux-perf-users/23879991.0LEYPuXRzz@milian-workstation/
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240611050626.1223155-1-irogers@google.com

diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index ae64090184d328f3089832139d8d385f4bd934af..37bb7771d9143466e99b431f9943a3fe1e31bbf7 100644 (file)
--- 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 66a3de8ac66186b024226cd03cf0fdeb6ff99f34..019305b94e5fc8b6b36223d708277bc6e17d98a4 100644 (file)
--- 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.
         */