On 6/5/23 07:15, Thomas Gleixner wrote:
On Mon, Apr 10 2023 at 01:14, Xin Li wrote:
A FRED stack frame generated by a ring 3 event should never be messed up, and
the first thing we must make sure is that at the time an ERETU instruction is
executed, %rsp must have the same address as that when the user level event
was just delivered.
However we don't want to bother the normal code path of ERETU because it's on
the hotest code path, a good choice is to do this check when ERETU
faults.
Which might be not catching bugs where the wrong frame makes ERETU not
fault.
We have CONFIG_DEBUG_ENTRY for catching this at the proper place.
This is true, but this BUG() is a cheap test on a slow path, and thus
can be included in production code.
-hpa
