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diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst
index 8ddb9b09451c..45e66a60a816 100644
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+++ b/Documentation/trace/events.rst
@@ -230,6 +230,16 @@ Currently the caret ('^') for an error always appears at the beginning of
the filter string; the error message should still be useful though
even without more accurate position info.
+5.2.1 Filter limitations
+------------------------
+
+If a filter is placed on a string pointer ``(char *)`` that does not point
+to a string on the ring buffer, but instead points to kernel or user space
+memory, then, for safety reasons, at most 1024 bytes of the content is
+copied onto a temporary buffer to do the compare. If the copy of the memory
+faults (the pointer points to memory that should not be accessed), then the
+string compare will be treated as not matching.
+
5.3 Clearing filters
--------------------