Messages in this thread | | | Date | Mon, 13 Dec 2021 14:12:44 -0800 | Subject | Re: [PATCH 10/25] x86/sgx: Support enclave page permission changes | From | Reinette Chatre <> |
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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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