> > > 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.
