Re: [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES

From: Jarkko Sakkinen
Date: Mon Sep 21 2020 - 15:58:35 EST

On Mon, Sep 21, 2020 at 10:44:19PM +0300, Jarkko Sakkinen wrote:
> On Mon, Sep 21, 2020 at 09:49:48PM +0300, Jarkko Sakkinen wrote:
> > To have understandable semantics you have to map error codes to
> > conditions rather than opcodes. -EIO means loss of enclave in the event
> > of EPC gone invalid. Enclave is already lost, that is the reason why we
> > deinitialize the kernel data structures.
> >
> > EADD must have a different error code because nothing is actually lost
> > but the failure conditions are triggered outside. -EFAULT would be
> > probably the most reasonable choice for that.
> Now that I did all the changes discussed and then I remember why EADD
> and EEXTEND had a common error code, and common behaviour. Obviously EADD
> can also fail because of EPC reset because it depends on a valid SECS
> page.
> If we cannot distinct from EADD caused by EPC loss and EADD caused by
> problems with the source, it should have the same error code, and also
> the enclave should be deinitialized, whenver this happens.
> So I would just revert to v38 behaviour, keeping of course the whole
> check more visible in sgx_ioc_enclave_add_pages(), and just refine
> the documentation better describe the whole situation.

So now the behaviour is reverted back to same as it was before [*] and
I refined the documenation as:

* The function deinitializes kernel data structures for enclave and returns
* -EIO in any of the following conditions:
* - Enclave Page Cache (EPC), the physical memory holding enclaves, has
* been invalidated. This will cause EADD and EEXTEND to fail.
* - If the source address is corrupted somehow when executing EADD.