linux-kernel - [PATCH 01/10] perf: Track build id faults for mmap2 event

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Date:   Tue, 22 Jun 2021 17:39:09 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 01/10] perf: Track build id faults for mmap2 event

Keep track of build id parsing faults per event,
so we can report it in following patches.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 include/linux/perf_event.h |  1 +
 kernel/events/core.c       | 11 +++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f5a6a2f069ed..5110a998f59b 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -669,6 +669,7 @@ struct perf_event {
 	unsigned int			attach_state;
 	local64_t			count;
 	atomic64_t			child_count;
+	local64_t			build_id_faults;
 
 	/*
 	 * These are the total time in nanoseconds that the event
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6fee4a7e88d7..d83ccb58a3c1 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8183,6 +8183,7 @@ struct perf_mmap_event {
 	u32			prot, flags;
 	u8			build_id[BUILD_ID_SIZE_MAX];
 	u32			build_id_size;
+	bool			build_id_fault;
 
 	struct {
 		struct perf_event_header	header;
@@ -8244,6 +8245,9 @@ static void perf_event_mmap_output(struct perf_event *event,
 	if (event->attr.mmap2 && use_build_id)
 		mmap_event->event_id.header.misc |= PERF_RECORD_MISC_MMAP_BUILD_ID;
 
+	if (mmap_event->build_id_fault)
+		local64_inc(&event->build_id_faults);
+
 	perf_output_put(&handle, mmap_event->event_id);
 
 	if (event->attr.mmap2) {
@@ -8386,8 +8390,11 @@ 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(vma, mmap_event->build_id, &mmap_event->build_id_size);
+	if (atomic_read(&nr_build_id_events)) {
+		int err = build_id_parse(vma, mmap_event->build_id,
+					 &mmap_event->build_id_size);
+		mmap_event->build_id_fault = err == -EFAULT;
+	}
 
 	perf_iterate_sb(perf_event_mmap_output,
 		       mmap_event,
-- 
2.31.1