On Fri, Dec 14, 2018 at 07:12:04AM -0800, Sean Christopherson wrote: > On Fri, Dec 14, 2018 at 09:55:49AM +0000, Jethro Beekman wrote: > > On 2018-12-14 03:01, Sean Christopherson wrote: > > >+2: pop %rbx > > >+ pop %r12 > > >+ pop %r13 > > >+ pop %r14 > > >+ pop %r15 > > >+ pop %rbp > > >+ ret > > > > x86-64 ABI requires that you call CLD here (enclave may set it). > > Ugh. Technically MXCSR and the x87 CW also need to be preserved. > > What if rather than treating the enclave as hostile we require it to be > compliant with the x86-64 ABI like any other function? That would solve > the EFLAGS.DF, MXCSR and x87 issues without adding unnecessary overhead. > And we wouldn't have to save/restore R12-R15. It'd mean we couldn't use > the stack's red zone to hold @regs and @e, but that's poor form anyways.
Grr, except the processor crushes R12-R15, FCW and MXCSR on asynchronous exits. But not EFLAGS.DF, that's real helpful.
