On Mon, Jun 05 2023 at 09:42, H. Peter Anvin wrote: > 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. No objection.
