Re: [PATCHv8 14/17] x86/traps: Handle LASS thrown #SS

H. Peter Anvin
2025-07-06T15:08:56Z

On July 6, 2025 2:22:13 AM PDT, David Laight <david.laight.linux@gmail.com> wrote:
>On Tue, 01 Jul 2025 19:06:10 -0700
>"H. Peter Anvin" <hpa@zytor.com> wrote:
>...
>> Note: for a FRED system, ERETU can generate #SS for a non-canonical user space
>> RSP even in the absence of LASS, so if that is not currently handled that is an active bug.
>
>Is that a fault in kernel space, or a fault in user space.
>
>Some of the traps for 'iret' happen after the transition to user space,
>so the kernel doesn't have to handle them as special cases.
>(I simplified (and fixed) one version of that code.)
>
> David
>

It's a fault in user space. I had a brain fart and managed to forget that RSP is technically a GPR and as such is not limited to the VA width of the machine.