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    SubjectRe: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver
    On Thu, Jun 25, 2020 at 08:53:34PM +0200, Borislav Petkov wrote:
    > 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

    I'll change it to "Add SGX enclave driver".

    >
    > > 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.

    Neither can I.

    > > 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)

    I rephrased the whole paragraph:

    "
    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().
    "

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

    Thank you.

    >
    > --
    > Regards/Gruss,
    > Boris.
    >
    > https://people.kernel.org/tglx/notes-about-netiquette

    /Jarkko

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