Re: [PATCH V2 16/32] x86/sgx: Support restricting of enclave page permissions

Jarkko Sakkinen
2022-03-17T04:54:52Z

On Mon, Mar 14, 2022 at 08:32:28AM -0700, Reinette Chatre wrote:
> Hi Jarkko,
>
> On 3/13/2022 8:42 PM, Jarkko Sakkinen wrote:
> > On Fri, Mar 11, 2022 at 11:28:27AM -0800, Reinette Chatre wrote:
> >> Supporting permission restriction in an ioctl() enables the runtime to manage
> >> the enclave memory without needing to map it.
> >
> > Which is opposite what you do in EAUG. You can also augment pages without
> > needing the map them. Sure you get that capability, but it is quite useless
> > in practice.
> >
> >> I have considered the idea of supporting the permission restriction with
> >> mprotect() but as you can see in this response I did not find it to be
> >> practical.
> >
> > Where is it practical? What is your application? How is it practical to
> > delegate the concurrency management of a split mprotect() to user space?
> > How do we get rid off a useless up-call to the host?
> >
>
> The email you responded to contained many obstacles against using mprotect()
> but you chose to ignore them and snipped them all from your response. Could
> you please address the issues instead of dismissing them?

I did read the whole email but did not see anything that would make a case
for fully exposed EMODPR, or having asymmetrical towards how EAUG works.

I had the same discussion with Haitao about PROT_NONE earlier, and am
fully aware that PROT_READ is required.

BR, Jarkko