Background:
When CPU is going to idle state, it would inform RCU that
current CPU is entering idle through rcu_idle_enter(),
and RCU will ignore read-side critical sections of this CPU.
However, there is CFI check mechanism inside idle flow and
calls rcu_read_lock(), so "rcu_read_lock() used illegally while idle"
in rcu_read_lock() will be triggered because rcu_idle_enter()
was already called before.
Beside, the pointer of rcu_dereference() might be invalid
due to the RCU read-side critical sections will be ignoring in
this going idle CPU, it might cause problems like:
access the wrong data/address, kernel exception...
Based on above description:
We will add __nocfi to cpuidle_enter_state to avoid
“rcu_read_lock() used illegally while idle!”
and avoid the usage of invalid pointer of rcu_dereference()
in this situation.
Bug: 169017431
Change-Id: I8bbe25704e18cfde351a8f4277dd4b44b07421f5
Signed-off-by: rogercl.yang <rogercl.yang@mediatek.com>
Signed-off-by: Chun-Hung Wu <chun-hung.wu@mediatek.com>
b891b37591