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-rw-r--r--kernel/events/core.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index dd236b66ca3a..cb4238e85b38 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: