Re: RFC: userspace exception fixups

[Jarkko Sakkinen]

On Mon, Nov 19, 2018 at 07:29:36AM -0800, Andy Lutomirski wrote:
> 1. The kernel needs some way to know *when* to apply this fixup.
> Decoding the instruction stream and doing it to all exceptions that
> hit an ENCLU instruction seems like a poor design.

I'm not sure why you would ever need to do any type of fixup as the idea
is to just return to AEP i.e. from chosen exceptions (EPCM, #UD) the AEP
would work the same way as for exceptions that the kernel can deal with
except filling the exception information to registers.

> 2. It starts exposing what looks like a more generic exception
> handling mechanism to userspace, except that it's nonsensical for
> anything other than ENCLU.

Well, I see the user space and namely the run-time the host for the
enclave i.e. middle-man to provide services for emulating instructions
etc.

/Jarkko