1 files changed, 21 insertions, 0 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1a825a486a25..4ccb29bb761e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3660,6 +3660,26 @@ static void calc_timer_values(struct perf_event *event,
         *running = ctx_time - event->tstamp_running;
 }
 
+static void perf_event_init_userpage(struct perf_event *event)
+{
+        struct perf_event_mmap_page *userpg;
+        struct ring_buffer *rb;
+
+        rcu_read_lock();
+        rb = rcu_dereference(event->rb);
+        if (!rb)
+                goto unlock;
+
+        userpg = rb->user_page;
+
+        /* Allow new userspace to detect that bit 0 is deprecated */
+        userpg->cap_bit0_is_deprecated = 1;
+        userpg->size = offsetof(struct perf_event_mmap_page, __reserved);
+
+unlock:
+        rcu_read_unlock();
+}
+
 void __weak arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
 {
 }
@@ -4044,6 +4064,7 @@ again:
         ring_buffer_attach(event, rb);
         rcu_assign_pointer(event->rb, rb);
 
+        perf_event_init_userpage(event);
         perf_event_update_userpage(event);
 
 unlock: