[RFC v2 7/7] perf: add AUX record

[Alexander Shishkin]

When there's new data in the AUX space, output a record indicating its
offset and size and weather it was truncated to fix in the ring buffer.

Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
---
 include/uapi/linux/perf_event.h | 15 +++++++++++++++
 kernel/events/core.c            | 38 ++++++++++++++++++++++++++++++++++++++
 kernel/events/internal.h        |  3 +++
 kernel/events/ring_buffer.c     |  1 +
 4 files changed, 57 insertions(+)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index dd10f16..7f8621f 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -726,6 +726,21 @@ enum perf_event_type {
 	 */
 	PERF_RECORD_MMAP2			= 10,
 
+	/*
+	 * Records that new data landed in the AUX buffer part.
+	 *
+	 * struct {
+	 * 	struct perf_event_header	header;
+	 *
+	 * 	u64				aux_offset;
+	 * 	u64				aux_size;
+	 *	u8				truncated;
+	 *	u64				id;
+	 *	u64				stream_id;
+	 * };
+	 */
+	PERF_RECORD_AUX				= 11,
+
 	PERF_RECORD_MAX,			/* non-ABI */
 };
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 44d6d01..cd64b75 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5394,6 +5394,44 @@ void perf_event_mmap(struct vm_area_struct *vma)
 	perf_event_mmap_event(&mmap_event);
 }
 
+void perf_event_aux_event(struct perf_event *event, unsigned long head,
+			  unsigned long size, bool truncated)
+{
+	struct perf_output_handle handle;
+	struct perf_sample_data sample;
+	struct perf_aux_event {
+		struct perf_event_header	header;
+		u64				offset;
+		u64				size;
+		u8				truncated;
+		u64				id;
+		u64				stream_id;
+	} rec = {
+		.header = {
+			.type = PERF_RECORD_AUX,
+			.misc = 0,
+			.size = sizeof(rec),
+		},
+		.offset		= head,
+		.size		= size,
+		.truncated	= truncated,
+		.id		= primary_event_id(event),
+		.stream_id	= event->id,
+	};
+	int ret;
+
+	perf_event_header__init_id(&rec.header, &sample, event);
+	ret = perf_output_begin(&handle, event, rec.header.size);
+
+	if (ret)
+		return;
+
+	perf_output_put(&handle, rec);
+	perf_event__output_id_sample(event, &handle, &sample);
+
+	perf_output_end(&handle);
+}
+
 /*
  * IRQ throttle logging
  */
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index e20d073..8bc4547 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -63,6 +63,9 @@ static inline bool rb_has_aux(struct ring_buffer *rb)
 	return !!rb->aux_nr_pages;
 }
 
+void perf_event_aux_event(struct perf_event *event, unsigned long head,
+			  unsigned long size, bool truncated);
+
 extern void
 perf_event_header__init_id(struct perf_event_header *header,
 			   struct perf_sample_data *data,
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 8f76e5c..4e6f815 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -280,6 +280,7 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size,
 
 	aux_head = local_read(&rb->aux_head);
 	local_add(size, &rb->aux_head);
+	perf_event_aux_event(handle->event, aux_head, size, truncated);
 
 	rb->user_page->aux_head = local_read(&rb->aux_head);
 	smp_wmb();
-- 
2.0.0

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