Re: [PATCH v21 16/28] x86/sgx: Add the Linux SGX Enclave Driver

[Jarkko Sakkinen]

On Wed, Aug 07, 2019 at 06:15:34PM +0300, Jarkko Sakkinen wrote:
> On Mon, Jul 29, 2019 at 11:17:57AM +0000, Ayoun, Serge wrote:
> > > +	/* TCS pages need to be RW in the PTEs, but can be 0 in the EPCM. */
> > > +	if ((secinfo.flags & SGX_SECINFO_PAGE_TYPE_MASK) ==
> > > SGX_SECINFO_TCS)
> > > +		prot |= PROT_READ | PROT_WRITE;
> > 
> > For TCS pages you add both RD and WR maximum protection bits.
> > For the enclave to be able to run, user mode will have to change the
> > "vma->vm_flags" from PROT_NONE to PROT_READ | PROT_WRITE (otherwise
> > eenter fails).  This is exactly what your selftest  does.
> 
> Recap where the TCS requirements came from? Why does it need
> RW in PTEs and can be 0 in the EPCM? The comment should explain
> it rather leave it as a claim IMHO.

I mean after ~3 weeks of not looking into SGX (because being
on vacation etc.) I cannot remember details of this.

/Jarkko