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    SubjectRe: [PATCH 10/25] x86/sgx: Support enclave page permission changes
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    Hi Jarkko,

    On 12/10/2021 11:57 PM, Jarkko Sakkinen wrote:
    > On Mon, 2021-12-06 at 13:42 -0800, Reinette Chatre wrote:
    >> Hi Jarkko,
    >>
    >> On 12/4/2021 3:08 PM, Jarkko Sakkinen wrote:
    >>> On Wed, Dec 01, 2021 at 11:23:08AM -0800, Reinette Chatre wrote:
    >>>> In the initial (SGX1) version of SGX, pages in an enclave need to be
    >>>> created with permissions that support all usages of the pages, from the
    >>>> time the enclave is initialized until it is unloaded. For example,
    >>>> pages used by a JIT compiler or when code needs to otherwise be
    >>>> relocated need to always have RWX permissions.
    >>>>
    >>>> SGX2 includes two functions that can be used to modify the enclave page
    >>>> permissions of regular enclave pages within an initialized enclave.
    >>>> ENCLS[EMODPR] is run from the OS and used to restrict enclave page
    >>>> permissions while ENCLU[EMODPE] is run from within the enclave to
    >>>> extend enclave page permissions.
    >>>>
    >>>> Enclave page permission changes need to be approached with care and
    >>>> for this reason this initial support is to allow enclave page
    >>>> permission changes _only_ if the new permissions are the same or
    >>>> more restrictive that the permissions originally vetted at the time the
    >>>> pages were added to the enclave. Support for extending enclave page
    >>>> permissions beyond what was originally vetted is deferred.
    >>>
    >>> This paragraph is out-of-scope for a commit message. You could have
    >>> this in the cover letter but not here. I would just remove it.
    >>
    >> I think this is essential information that is mentioned in the cover
    >> letter _and_ in this changelog. I will follow Dave's guidance and avoid
    >> "deferred" by just removing that last sentence.
    >>
    >>>
    >>>> Whether enclave page permissions are restricted or extended it
    >>>> is necessary to ensure that the page table entries and enclave page
    >>>> permissions are in sync. Introduce a new ioctl, SGX_IOC_PAGE_MODP, to
    >>>
    >>> SGX_IOC_PAGE_MODP does not match the naming convetion of these:
    >>>
    >>> * SGX_IOC_ENCLAVE_CREATE
    >>> * SGX_IOC_ENCLAVE_ADD_PAGES
    >>> * SGX_IOC_ENCLAVE_INIT
    >>
    >> ah - my understanding was that the SGX_IOC_ENCLAVE prefix related to
    >> operations related to the entire enclave and thus I introduced the
    >> prefix SGX_IOC_PAGE to relate to operations on pages within an enclave.
    >
    > SGX_IOC_ENCLAVE_ADD_PAGES is also operation working on pages within an
    > enclave.
    >
    > Also, to be aligned with SGX_IOC_ENCLAVE_ADD_PAGES, the new operations
    > should also take secinfo as input.

    ok, will do.

    >
    >>
    >>>
    >>> A better name would be SGX_IOC_ENCLAVE_MOD_PROTECTIONS. It doesn't
    >>> do harm to be a more verbose.
    >>
    >> Will do. I see later you propose SGX_IOC_ENCLAVE_MODIFY_TYPE - would you
    >> like them to be consistent wrt MOD/MODIFY?
    >
    > I would considering introducing just one new ioctl:
    >
    > SGX_IOC_ENCLAVE_MODIFY_PAGES
    >
    > and choose either operations based on e.g. a flag
    > (see flags field SGX_IOC_ENCLAVE_ADD_PAGES).
    >

    There seems to be different opinion about the single ioctl() as
    per:https://lore.kernel.org/lkml/0fb14185-5cc3-a963-253d-2e119b4a52bb@intel.com/

    I thus plan to proceed with the two ioctls, both taking secinfo as
    input. Would that be ok with you?

    Reinette


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