Re: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver

Borislav Petkov
2020-06-25T18:53:39Z

On Thu, Jun 18, 2020 at 01:08:33AM +0300, Jarkko Sakkinen wrote:

> Subject: Re: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver
^
Add

> 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
> access the memory inside the enclave enforced by the CPU. We call these
> entities as enclaves.

s/as //

> This commit implements a driver that provides an ioctl API to construct

s/This commit implements/Implement/

> 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.
>
> Enclave are constructed by using ENCLS leaf functions ECREATE, EADD and

Enclaves

> EINIT. ECREATE initializes SECS, EADD copies pages from system memory to
> the EPC and EINIT check a given signed measurement and moves the enclave

checks

> into a state ready for execution.
>
> An initialized enclave can only be accessed through special Thread Control
> Structure (TCS) pages by using ENCLU (ring-3 only) leaf EENTER. This leaf
> function converts a thread into enclave mode and continues the execution in
> the offset defined by the TCS provided to EENTER. An enclave is exited
> through syscall, exception, interrupts or by explicitly calling another
> ENCLU leaf EEXIT.
>
> The permissions, which enclave page is added will set the limit for maximum
> permissions that can be set for mmap() and mprotect().

I can't parse that sentence.

> This will
> effectively allow to build different security schemes between producers and
> consumers of enclaves. Later on we can increase granularity with LSM hooks
> for page addition (i.e. for producers) and mapping of the enclave (i.e. for
> consumers)

Other than that, nice explanation. I like that in a commit message.

Thx.

--
Regards/Gruss,
Boris.