On Tue, Jul 07, 2020 at 06:01:51AM +0300, Jarkko Sakkinen wrote:
> Intel Software Guard eXtensions (SGX) is a set of CPU instructions that
> can be used by applications to set aside private regions of code and
> data. The code outside the SGX hosted software entity is disallowed to
s/disallowed to/prevented from/
> access the memory inside the enclave enforced by the CPU. We call these
s/enforced//
> entities enclaves.
>
> Add a driver that provides an ioctl API to construct and run enclaves.
> Enclaves are constructed from pages residing in reserved physical memory
> areas. The contents of these pages can only be accessed when they are
> mapped as part of an enclave, by a hardware thread running inside the
> enclave.
>
> The starting state of an enclave consists of a fixed measured set of
> pages that are copied to the EPC during the construction process by
> using ENCLS leaf functions and Software Enclave Control Structure (SECS)
> that defines the enclave properties.
>
> Enclaves are constructed by using ENCLS leaf functions ECREATE, EADD and
> EINIT. ECREATE initializes SECS, EADD copies pages from system memory to
> the EPC and EINIT checks a given signed measurement and moves the enclave
> into a state ready for execution.
What's a leaf function? Is it like a CPU instruction?
> The mmap() permissions are capped by the contained enclave page
> permissions. The mapped areas must also be opaque, i.e. each page address
> must contain a page. This logic is implemented in sgx_encl_may_map().
do you mean "populated" instead of "opaque"?
> + atomic_set(&encl->flags, 0);
> + kref_init(&encl->refcount);
> + INIT_RADIX_TREE(&encl->page_tree, GFP_KERNEL);
Why are you using a radix tree instead of an xarray?
> +int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start,
> + unsigned long end, unsigned long vm_prot_bits)
> +{
> + unsigned long idx, idx_start, idx_end;
> + struct sgx_encl_page *page;
> +
> + /*
> + * Disallow RIE tasks as their VMA permissions might conflict with the
> + * enclave page permissions.
> + */
> + if (!!(current->personality & READ_IMPLIES_EXEC))
> + return -EACCES;
> +
> + idx_start = PFN_DOWN(start);
> + idx_end = PFN_DOWN(end - 1);
> +
> + for (idx = idx_start; idx <= idx_end; ++idx) {
> + mutex_lock(&encl->lock);
> + page = radix_tree_lookup(&encl->page_tree, idx);
> + mutex_unlock(&encl->lock);
> +
> + if (!page || (~page->vm_max_prot_bits & vm_prot_bits))
> + return -EACCES;
You should really use an iterator here instead of repeated lookups.
xas_for_each() will probably be what you want.
