On Tue, 08 Oct 2019 23:42:34 -0500, Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
Enhance the SGX_IOC_ENCLAVE_ADD_PAGE{S} ioctl so that userspace can add
multiple pages to an enclave in a single syscall. Also provide a flag
that allows replicating a single source page to multiple target pages so
that userspace doesn't need to allocate a giant chunk of memory when
initializing things like the enlave's .bss, heap, etc...
People that actually develop runtimes, please weigh in. Jarkko also
suggested going with a fully flexible ioctl, e.g. essentially creating an
array of the existing struct so that mrmask and/or secinfo can be unique
per page. AFAICT that's overkill and more cumbersome to use as it forces
userspace to allocate the full array. My understanding is that the
majority of enclaves will have contiguous blocks of pages with identical
mrmask and secinfo, e.g. code segments, ro data, etc..., thus the less
flexible but easier-in-theory to use approach proposed here.
We think using the same mask for all pages (solution in this patch set) is
reasonable. Although it seems odd that all pages would apply the same
mask, this allows enough flexibility we can foresee.
Another option acceptable to us (Intel SGX runtime) is to change it to a
flag and have bit zero define whether the whole page is measured via
EEXTEND. This is simpler and allows other bits reserved for future usages.
However, it would fail any SGX runtime that is measuring partial page for
optimization purposes.
