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Subject: RE: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)
Thread-Topic: SGX vs LSM (Re: [PATCH v20 00/28] Intel SGX1 support)
Thread-Index: AQHVC0vUmIXibKT8TUm/EUnHn2XAfqZtq8EAgAEIegCAABy+AP//k24g
Date:   Thu, 16 May 2019 23:29:47 +0000
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> > > There is a problem here though. Usually the enclave itself is just a
> > > loader that then loads the application from outside source and
> > > creates the executable pages from the content.
> > >
> > > A great example of this is Graphene that bootstraps unmodified Linux
> > > applications to an enclave:
> > >
> > > https://github.com/oscarlab/graphene
> > >
> >
> > ISTM you should need EXECMEM or similar to run Graphene, then.
> 
> Agreed, Graphene is effectively running arbitrary enclave code.  I'm
> guessing there is nothing that prevents extending/reworking Graphene to
> allow generating the enclave ahead of time so as to avoid populating the
> guts of the enclave at runtime, i.e. it's likely possible to run an
> unmodified application in an enclave without EXECMEM if that's something
> Graphene or its users really care about.

Inefficient use of memory is a problem of running Graphene on SGX1, from at least 2 aspects: 1) heaps/stacks have to be pre-allocated but only a small portion of those pages will be actually used; and 2) dynamic linking is commonly used in *unmodified* applications and all dependent libraries have to be loaded, but only a subset of those pages will actually be used - e.g. most applications use only a small set of functions in libc.so but the whole library still has to be loaded. Hence a practical/efficient solution will require/involve EDMM features available in SGX2. I guess we shall look a bit further into future in order to address this problem properly. And I think it necessary to distinguish enclave virtual ranges from regular ones (probably at VMA level) before we could have a practical solution.