Messages in this thread | | | Date | Mon, 5 Jun 2023 09:42:52 -0700 | Subject | Re: [PATCH v8 31/33] x86/fred: BUG() when ERETU with %rsp not equal to that when the ring 3 event was just delivered | From | "H. Peter Anvin" <> |
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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
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