2 files changed, 30 insertions, 8 deletions

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 62c25a25291c..42cb7b62ca59 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -134,8 +134,9 @@ enum perf_event_sample_format {
         PERF_SAMPLE_STACK_USER                  = 1U << 13,
         PERF_SAMPLE_WEIGHT                      = 1U << 14,
         PERF_SAMPLE_DATA_SRC                    = 1U << 15,
+        PERF_SAMPLE_IDENTIFIER                  = 1U << 16,
 
-        PERF_SAMPLE_MAX = 1U << 16,             /* non-ABI */
+        PERF_SAMPLE_MAX = 1U << 17,             /* non-ABI */
 };
 
 /*
@@ -492,12 +493,12 @@ enum perf_event_type {
         /*
          * If perf_event_attr.sample_id_all is set then all event types will
          * have the sample_type selected fields related to where/when
-         * (identity) an event took place (TID, TIME, ID, CPU, STREAM_ID)
-         * described in PERF_RECORD_SAMPLE below, it will be stashed just after
-         * the perf_event_header and the fields already present for the existing
-         * fields, i.e. at the end of the payload. That way a newer perf.data
-         * file will be supported by older perf tools, with these new optional
-         * fields being ignored.
+         * (identity) an event took place (TID, TIME, ID, STREAM_ID, CPU,
+         * IDENTIFIER) described in PERF_RECORD_SAMPLE below, it will be stashed
+         * just after the perf_event_header and the fields already present for
+         * the existing fields, i.e. at the end of the payload. That way a newer
+         * perf.data file will be supported by older perf tools, with these new
+         * optional fields being ignored.
          *
          * struct sample_id {
          *      { u32                   pid, tid; } && PERF_SAMPLE_TID
@@ -505,7 +506,12 @@ enum perf_event_type {
          *      { u64                   id;       } && PERF_SAMPLE_ID
          *      { u64                   stream_id;} && PERF_SAMPLE_STREAM_ID
          *      { u32                   cpu, res; } && PERF_SAMPLE_CPU
+         *      { u64                   id;       } && PERF_SAMPLE_IDENTIFIER
          * } && perf_event_attr::sample_id_all
+         *
+         * Note that PERF_SAMPLE_IDENTIFIER duplicates PERF_SAMPLE_ID.  The
+         * advantage of PERF_SAMPLE_IDENTIFIER is that its position is fixed
+         * relative to header.size.
          */
 
         /*
@@ -594,6 +600,13 @@ enum perf_event_type {
          * struct {
          *      struct perf_event_header        header;
          *
+         *      #
+         *      # Note that PERF_SAMPLE_IDENTIFIER duplicates PERF_SAMPLE_ID.
+         *      # The advantage of PERF_SAMPLE_IDENTIFIER is that its position
+         *      # is fixed relative to header.
+         *      #
+         *
+         *      { u64                   id;       } && PERF_SAMPLE_IDENTIFIER
          *      { u64                   ip;       } && PERF_SAMPLE_IP
          *      { u32                   pid, tid; } && PERF_SAMPLE_TID
          *      { u64                   time;     } && PERF_SAMPLE_TIME
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 928fae7ca8c7..15d0f2418e54 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1213,6 +1213,9 @@ static void perf_event__id_header_size(struct perf_event *event)
         if (sample_type & PERF_SAMPLE_TIME)
                 size += sizeof(data->time);
 
+        if (sample_type & PERF_SAMPLE_IDENTIFIER)
+                size += sizeof(data->id);
+
         if (sample_type & PERF_SAMPLE_ID)
                 size += sizeof(data->id);
 
@@ -4280,7 +4283,7 @@ static void __perf_event_header__init_id(struct perf_event_header *header,
         if (sample_type & PERF_SAMPLE_TIME)
                 data->time = perf_clock();
 
-        if (sample_type & PERF_SAMPLE_ID)
+        if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER))
                 data->id = primary_event_id(event);
 
         if (sample_type & PERF_SAMPLE_STREAM_ID)
@@ -4319,6 +4322,9 @@ static void __perf_event__output_id_sample(struct perf_output_handle *handle,
 
         if (sample_type & PERF_SAMPLE_CPU)
                 perf_output_put(handle, data->cpu_entry);
+
+        if (sample_type & PERF_SAMPLE_IDENTIFIER)
+                perf_output_put(handle, data->id);
 }
 
 void perf_event__output_id_sample(struct perf_event *event,
@@ -4432,6 +4438,9 @@ void perf_output_sample(struct perf_output_handle *handle,
 
         perf_output_put(handle, *header);
 
+        if (sample_type & PERF_SAMPLE_IDENTIFIER)
+                perf_output_put(handle, data->id);
+
         if (sample_type & PERF_SAMPLE_IP)
                 perf_output_put(handle, data->ip);