Re: [PATCH V2 19/32] x86/sgx: Support adding of pages to an initialized enclave

Jarkko Sakkinen
2022-02-23T15:46:12Z

On Tue, Feb 22, 2022 at 11:19:11AM -0800, Reinette Chatre wrote:
> Hi Jarkko,
>
> On 2/20/2022 10:40 AM, Jarkko Sakkinen wrote:
> ...
>
> > Do you know if it is possible to do EAUG, EMODPR and the do a single
> > EACCEPT for both? Just looking at pseudo-code, it looked doable but
> > I need to check this.
> >
> > I.e. EAUG has this
> >
> > EPCM(DS:RCX).BLOCKED := 0;
> > EPCM(DS:RCX).PENDING := 1;
> > EPCM(DS:RCX).MODIFIED := 0;
> > EPCM(DS:RCX).PR := 0;
> > (* associate the EPCPAGE with the SECS by storing the SECS identifier of DS:TMP_SECS *)
> > Update EPCM(DS:RCX) SECS identifier to reference DS:TMP_SECS identifier;
> > (* Set EPCM valid fields *)
> > EPCM(DS:RCX).VALID := 1;
> >
> > And EMODPR only checks .VALID.
>
> After that check there is also:
> IF (EPCM(DS:RCX).PENDING is not 0 or (EPCM(DS:RCX).MODIFIED is not 0) )
> THEN
> RFLAGS.ZF := 1;
> RAX := SGX_PAGE_NOT_MODIFIABLE;
> GOTO DONE;
> FI;
>
> Attempting the SGX_IOC_ENCLAVE_RESTRICT_PERMISSIONS ioctl() on a recently
> added page (EAUG) that has not yet been EACCEPTed is thus expected to fail
> with errno of EFAULT (indicating ENCLS[EMODPR] failure) and the returned
> structure's result field set to 20 (SGX_PAGE_NOT_MODIFIABLE).
>
> I confirmed this behavior by modifying the "augment" kselftest test by adding
> a SGX_IOC_ENCLAVE_RESTRICT_PERMISSIONS call between the new memory access and
> the EACCEPT.

Thank you, also Mark confirmed this.

BR, Jarkko