[PATCHv3 bpf-next 2/9] perf: Use file object build id in perf_event_mmap_event

[Jiri Olsa]

Use build id from file object when available for perf's MMAP2 event
build id data.

The file's f_build_id is available (for CONFIG_FILE_BUILD_ID option)
when the file is mmap-ed and before the perf's callback is executed,
so we can use it, instead of reading it again.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 kernel/events/core.c | 43 +++++++++++++++++++++++++++++++++++++++----
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f79fd8b87f75..3a5398dda6f6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8527,6 +8527,9 @@ struct perf_mmap_event {
 	u32			prot, flags;
 	u8			build_id[BUILD_ID_SIZE_MAX];
 	u32			build_id_size;
+#ifdef CONFIG_FILE_BUILD_ID
+	struct build_id		*f_build_id;
+#endif
 
 	struct {
 		struct perf_event_header	header;
@@ -8539,6 +8542,38 @@ struct perf_mmap_event {
 	} event_id;
 };
 
+#ifdef CONFIG_FILE_BUILD_ID
+static void build_id_read(struct perf_mmap_event *mmap_event)
+{
+	struct vm_area_struct *vma = mmap_event->vma;
+
+	mmap_event->f_build_id = vma->vm_file ? vma->vm_file->f_build_id : NULL;
+}
+
+static bool has_build_id(struct perf_mmap_event *mmap_event)
+{
+	return !IS_ERR_OR_NULL(mmap_event->f_build_id);
+}
+
+#define build_id_data mmap_event->f_build_id->data
+#define build_id_size mmap_event->f_build_id->sz
+#else
+static void build_id_read(struct perf_mmap_event *mmap_event)
+{
+	struct vm_area_struct *vma = mmap_event->vma;
+
+	build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size);
+}
+
+static bool has_build_id(struct perf_mmap_event *mmap_event)
+{
+	return mmap_event->build_id_size;
+}
+
+#define build_id_data mmap_event->build_id
+#define build_id_size mmap_event->build_id_size
+#endif
+
 static int perf_event_mmap_match(struct perf_event *event,
 				 void *data)
 {
@@ -8583,7 +8618,7 @@ static void perf_event_mmap_output(struct perf_event *event,
 	mmap_event->event_id.pid = perf_event_pid(event, current);
 	mmap_event->event_id.tid = perf_event_tid(event, current);
 
-	use_build_id = event->attr.build_id && mmap_event->build_id_size;
+	use_build_id = event->attr.build_id && has_build_id(mmap_event);
 
 	if (event->attr.mmap2 && use_build_id)
 		mmap_event->event_id.header.misc |= PERF_RECORD_MISC_MMAP_BUILD_ID;
@@ -8592,10 +8627,10 @@ static void perf_event_mmap_output(struct perf_event *event,
 
 	if (event->attr.mmap2) {
 		if (use_build_id) {
-			u8 size[4] = { (u8) mmap_event->build_id_size, 0, 0, 0 };
+			u8 size[4] = { (u8) build_id_size, 0, 0, 0 };
 
 			__output_copy(&handle, size, 4);
-			__output_copy(&handle, mmap_event->build_id, BUILD_ID_SIZE_MAX);
+			__output_copy(&handle, build_id_data, BUILD_ID_SIZE_MAX);
 		} else {
 			perf_output_put(&handle, mmap_event->maj);
 			perf_output_put(&handle, mmap_event->min);
@@ -8727,7 +8762,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
 	mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
 
 	if (atomic_read(&nr_build_id_events))
-		build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size);
+		build_id_read(mmap_event);
 
 	perf_iterate_sb(perf_event_mmap_output,
 		       mmap_event,
-- 
2.39.2