Re: RFC: userspace exception fixups

[Jethro Beekman]

On 2018-11-02 10:01, Andy Lutomirski wrote:
> On Fri, Nov 2, 2018 at 9:56 AM Jethro Beekman <jethro@xxxxxxxxxxxx> wrote:
> > On 2018-11-02 09:52, Sean Christopherson wrote:
> > > On Fri, Nov 02, 2018 at 04:37:10PM +0000, Jethro Beekman wrote:
> > > > On 2018-11-02 09:30, Sean Christopherson wrote:
> > > > > ... The intended convention for EENTER is to have an ENCLU at the AEX target ...
> > > > >
> > > > > ... to further enforce that the AEX target needs to be ENCLU.
> > > >
> > > > Some SGX runtimes may want to use a different AEX target.
> > >
> > > To what end?  Userspace gets no indication as to why the AEX occurred.
> > > And if exceptions are getting transfered to userspace the trampoline
> > > would effectively be handling only INTR, NMI, #MC and EPC #PF.
> >
> > Various reasons...
> >
> > Userspace may have established an exception handling convention with the
> > enclave (by setting TCS.NSSA > 1) and may want to call EENTER instead of
> > ERESUME.
>
> Ugh,
>
> I sincerely hope that a future ISA extension lets the kernel return
> directly back to enclave mode so that AEX events become entirely
> invisible to user code.

Can you explain how this would work for things like #BR/#DE/#UD that 
need to be fixed up by code running in the enclave before it can be resumed?

--
Jethro Beekman | Fortanix

Attachment: smime.p7s
Description: S/MIME Cryptographic Signature