Re: [PATCH v26 10/22] x86/sgx: Linux Enclave Driver

[Jarkko Sakkinen]

On Thu, Feb 20, 2020 at 04:32:22PM -0800, Andy Lutomirski wrote:
> > On Feb 20, 2020, at 2:16 PM, Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> > 
> > ïOn Thu, Feb 20, 2020 at 10:48:42AM -0800, Sean Christopherson wrote:
> >> My biggest concern for allowing PROT_EXEC if RIE is that it would result
> >> in #PF(SGX) (#GP on Skylake) due to an EPCM violation if the enclave
> >> actually tried to execute from such a page.  This isn't a problem for the
> >> kernel as the fault will be reported cleanly through the vDSO (or get
> >> delivered as a SIGSEGV if the enclave isn't entered through the vDSO), but
> >> it's a bit weird for userspace as userspace will see the #PF(SGX) and
> >> likely assume the EPC was lost, e.g. silently restart the enclave instead
> >> of logging an error that the enclave is broken.
> > 
> > I think right way to fix the current implementation is to -EACCES mmap()
> > (and mprotect) when !!(current->personality & READ_IMPLIES_EXEC).
> > 
> > This way supporting RIE can be reconsidered later on without any
> > potential ABI bottlenecks.
> > 
> 
> Sounds good to me.  I see no credible reason why anyone would use RIE and SGX.

Great, thanks Andy.

/Jarkko