On Fri, May 31, 2019 at 04:31:52PM -0700, Sean Christopherson wrote: > SGX enclaves have an associated Enclave Linear Range (ELRANGE) that is > tracked and enforced by the CPU using a base+mask approach, similar to > how hardware range registers such as the variable MTRRs. As a result, > the ELRANGE must be naturally sized and aligned. > > To reduce boilerplate code that would be needed in every userspace > enclave loader, the SGX driver naturally aligns the mmap() address and > also requires the range to be naturally sized. Unfortunately, SGX fails > to grant a waiver to the MAP_FIXED case, e.g. incorrectly rejects mmap() > if userspace is attempting to map a small slice of an existing enclave. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Why you want to allow mmap() to be called multiple times? mmap() could be allowed only once with PROT_NONE and denied afterwards. Is this for sending fd to another process that would map already existing enclave? I don't see any checks for whether the is enclave underneath. Also, I think that in all cases mmap() callback should allow only PROT_NONE as permissions for clarity even if it could called multiple times. /Jarkko
