[PATCH] kasan: Add documentation for CONFIG_KASAN_EXTRA_INFO

[Juntong Deng]

This patch adds CONFIG_KASAN_EXTRA_INFO introduction information to
KASAN documentation.

Signed-off-by: Juntong Deng <juntong.deng@xxxxxxxxxxx>
---
 Documentation/dev-tools/kasan.rst | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index a5a6dbe9029f..3dc48b08cf71 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -277,6 +277,27 @@ traces point to places in code that interacted with the object but that are not
 directly present in the bad access stack trace. Currently, this includes
 call_rcu() and workqueue queuing.
 
+CONFIG_KASAN_EXTRA_INFO
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Enabling CONFIG_KASAN_EXTRA_INFO allows KASAN to record and report more
+information, the extra information currently supported is the CPU number and
+timestamp at allocation and free. More information can help find the cause of
+the bug and correlate the error with other system events, at the cost of using
+extra memory to record more information (more cost details in the help text of
+CONFIG_KASAN_EXTRA_INFO).
+
+Here is the report with CONFIG_KASAN_EXTRA_INFO enabled (only the
+different parts are shown)::
+
+    ==================================================================
+    ...
+    Allocated by task 134 on cpu 5 at 229.133855s:
+    ...
+    Freed by task 136 on cpu 3 at 230.199335s:
+    ...
+    ==================================================================
+
 Implementation details
 ----------------------
 
-- 
2.39.2