On Wed, Sep 26, 2018 at 03:37:45PM -0700, Andy Lutomirski wrote:
> Yeah. Maybe like this: > > xorl %eax,%eax > eenter_insn:
> ENCLU[whatever]
> eenter_landing_pad:
> ret
>
> And the kernel would use the existing vdso2c vdso-symbol-finding
> mechanism to do the fixup.
>
> >
> > How would a syscall work, though? I assume we can't just enter the
> > enclave from ring0.
>
> My understanding of how AEX works is a bit vague, but maybe a syscall
> could reuse the mechanism? The vDSO approach seems considerably
> simpler.
>
> We do need to make sure that a fault that happens on or after return
> from an AEX event does the right thing. But I'm still vague on how
> that works, sigh.
>
> --Andy
Returning from AEX does not differ from any other memory access event so
AFAIK it should be handled right with the proposed solution already.
For convenience I think we could have a fixed trampoline for AEX e.g.
this how it is implemented in the open source LE that I did:
sgx_get_token:
push %rbx
mov $0x02, %rax
mov %rsi, %rbx
mov %rdx, %rsi
mov $sgx_async_exit, %rcx
sgx_async_exit:
ENCLU
pop %rbx
ret
BTW, if I converted the in-kernel LE as a standalone test program, would
that be useful for basic testing of the series?
/Jarkko
