[PATCH 03/24] perf: Add build id data in mmap2 event

[Jiri Olsa]

Adding support to carry build id data in mmap2 event.

The build id data replaces maj/min/ino/ino_generation
fields, whichc are also used to identify map's binary,
so it's ok to replace them with build id data:

  union {
          struct {
                  u32       maj;
                  u32       min;
                  u64       ino;
                  u64       ino_generation;
          };
          struct {
                  u8        build_id[20];
                  u8        build_id_size;
                  u8        __reserved_1;
                  u16       __reserved_2;
          };
  };

Replaced maj/min/ino/ino_generation fields give us size
of 24 bytes. We use 20 bytes for build id data, 1 byte
for size and rest is unused.

There's new misc bit for mmap2 to signal there's build
id data in it:

  #define PERF_RECORD_MISC_BUILD_ID              (1 << 14)

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 include/uapi/linux/perf_event.h | 26 +++++++++++++++++++++-----
 kernel/events/core.c            | 31 +++++++++++++++++++++++++++----
 2 files changed, 48 insertions(+), 9 deletions(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index b95d3c485d27..b6caf61bf9fd 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -384,7 +384,8 @@ struct perf_event_attr {
 				aux_output     :  1, /* generate AUX records instead of events */
 				cgroup         :  1, /* include cgroup events */
 				text_poke      :  1, /* include text poke events */
-				__reserved_1   : 30;
+				build_id       :  1, /* use build id in mmap2 events */
+				__reserved_1   : 29;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
@@ -688,6 +689,7 @@ struct perf_event_mmap_page {
  *
  *   PERF_RECORD_MISC_EXACT_IP           - PERF_RECORD_SAMPLE of precise events
  *   PERF_RECORD_MISC_SWITCH_OUT_PREEMPT - PERF_RECORD_SWITCH* events
+ *   PERF_RECORD_MISC_BUILD_ID           - PERF_RECORD_MMAP2 event
  *
  *
  * PERF_RECORD_MISC_EXACT_IP:
@@ -697,9 +699,13 @@ struct perf_event_mmap_page {
  *
  * PERF_RECORD_MISC_SWITCH_OUT_PREEMPT:
  *   Indicates that thread was preempted in TASK_RUNNING state.
+ *
+ * PERF_RECORD_MISC_BUILD_ID:
+ *   Indicates that mmap2 event carries build id data.
  */
 #define PERF_RECORD_MISC_EXACT_IP		(1 << 14)
 #define PERF_RECORD_MISC_SWITCH_OUT_PREEMPT	(1 << 14)
+#define PERF_RECORD_MISC_BUILD_ID		(1 << 14)
 /*
  * Reserve the last bit to indicate some extended misc field
  */
@@ -911,10 +917,20 @@ enum perf_event_type {
 	 *	u64				addr;
 	 *	u64				len;
 	 *	u64				pgoff;
-	 *	u32				maj;
-	 *	u32				min;
-	 *	u64				ino;
-	 *	u64				ino_generation;
+	 *	union {
+	 *		struct {
+	 *			u32		maj;
+	 *			u32		min;
+	 *			u64		ino;
+	 *			u64		ino_generation;
+	 *		};
+	 *		struct {
+	 *			u8		build_id[20];
+	 *			u8		build_id_size;
+	 *			u8		__reserved_1;
+	 *			u16		__reserved_2;
+	 *		};
+	 *	};
 	 *	u32				prot, flags;
 	 *	char				filename[];
 	 * 	struct sample_id		sample_id;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index da467e1dd49a..808473b6ce85 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -51,6 +51,7 @@
 #include <linux/proc_ns.h>
 #include <linux/mount.h>
 #include <linux/min_heap.h>
+#include <linux/buildid.h>
 
 #include "internal.h"
 
@@ -395,6 +396,7 @@ static atomic_t nr_ksymbol_events __read_mostly;
 static atomic_t nr_bpf_events __read_mostly;
 static atomic_t nr_cgroup_events __read_mostly;
 static atomic_t nr_text_poke_events __read_mostly;
+static atomic_t nr_build_id_events __read_mostly;
 
 static LIST_HEAD(pmus);
 static DEFINE_MUTEX(pmus_lock);
@@ -4672,6 +4674,8 @@ static void unaccount_event(struct perf_event *event)
 		dec = true;
 	if (event->attr.mmap || event->attr.mmap_data)
 		atomic_dec(&nr_mmap_events);
+	if (event->attr.build_id)
+		atomic_dec(&nr_build_id_events);
 	if (event->attr.comm)
 		atomic_dec(&nr_comm_events);
 	if (event->attr.namespaces)
@@ -7942,6 +7946,8 @@ struct perf_mmap_event {
 	u64			ino;
 	u64			ino_generation;
 	u32			prot, flags;
+	u8			build_id[BUILD_ID_SIZE];
+	u32			build_id_size;
 
 	struct {
 		struct perf_event_header	header;
@@ -7997,13 +8003,23 @@ 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);
 
+	if (event->attr.mmap2 && event->attr.build_id)
+		mmap_event->event_id.header.misc |= PERF_RECORD_MISC_BUILD_ID;
+
 	perf_output_put(&handle, mmap_event->event_id);
 
 	if (event->attr.mmap2) {
-		perf_output_put(&handle, mmap_event->maj);
-		perf_output_put(&handle, mmap_event->min);
-		perf_output_put(&handle, mmap_event->ino);
-		perf_output_put(&handle, mmap_event->ino_generation);
+		if (event->attr.build_id) {
+			u8 size[4] = { (u8) mmap_event->build_id_size, 0, 0, 0 };
+
+			__output_copy(&handle, mmap_event->build_id, BUILD_ID_SIZE);
+			__output_copy(&handle, size, 4);
+		} else {
+			perf_output_put(&handle, mmap_event->maj);
+			perf_output_put(&handle, mmap_event->min);
+			perf_output_put(&handle, mmap_event->ino);
+			perf_output_put(&handle, mmap_event->ino_generation);
+		}
 		perf_output_put(&handle, mmap_event->prot);
 		perf_output_put(&handle, mmap_event->flags);
 	}
@@ -8132,6 +8148,11 @@ 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_size(vma, mmap_event->build_id,
+				    &mmap_event->build_id_size);
+	}
+
 	perf_iterate_sb(perf_event_mmap_output,
 		       mmap_event,
 		       NULL);
@@ -11069,6 +11090,8 @@ static void account_event(struct perf_event *event)
 		inc = true;
 	if (event->attr.mmap || event->attr.mmap_data)
 		atomic_inc(&nr_mmap_events);
+	if (event->attr.build_id)
+		atomic_inc(&nr_build_id_events);
 	if (event->attr.comm)
 		atomic_inc(&nr_comm_events);
 	if (event->attr.namespaces)
-- 
2.26.2