Re: RFC: userspace exception fixups

[Jethro Beekman]

On 2018-11-07 02:17, Andy Lutomirski wrote:
> On Tue, Nov 6, 2018 at 4:02 PM Sean Christopherson
> <sean.j.christopherson@xxxxxxxxx> wrote:
> > /*
> >   * EEXIT or EENTER faulted.  In the latter case, %RAX already holds some
> >   * fault indicator, e.g. -EFAULT.
> >   */
> > eexit_or_eenter_fault:
> >      ret
>
> But userspace wants to know whether it was a fault or not.  So I think
> we either need two landing pads or we need to hijack a flag bit (are
> there any known-zeroed flag bits after EEXIT?) to say whether it was a
> fault.  And, if it was a fault, we should give the vector, the
> sanitized error code, and possibly CR2.

On AEX, %rax will contain ENCLU_LEAF_ERESUME (0x3). On EEXIT, %rax will 
contain ENCLU_LEAF_EEXIT (0x4).

--
Jethro Beekman | Fortanix

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