Re: [PATCH] x86/sgx: Remove PROT_NONE branch from sgx_encl_may_map().

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Mon, Mar 30, 2020 at 09:54:52PM +0300, Jarkko Sakkinen wrote:
> sgx_encl_may_map() always succeeding when PROT_NONE is given is not that
> useful behaviour as one can just well as do an anonymous mapping as
> demonstrated by the change in this patch to the test program. As a
> consequence, remove the special case.
> 
> Pratically any possible way to make sure that you don't overwrite anything
> useful in the memory, should be fine. MAP_FIXED does not care what's
> underneath (if you want't it to care you ought to use
> MAP_FIXED_NO_REPLACE).
> 
> After this change, the selftest run called sgx_mmap() only three times
> (TCS, text, data) instead of four.
> 
>         test_sgx-1811  [002] ....   586.907585: sgx_mmap <-mmap_region
>         test_sgx-1811  [002] ....   586.911752: sgx_mmap <-mmap_region
>         test_sgx-1811  [002] ....   586.911756: sgx_mmap <-mmap_region
> 
> This also gives more angles to segregate enclave building and mapping as
> the mmap()'s need to be applied only when the enclave is fully built:
> 
> Cc: luto@kernel.org
> Cc: Haitao Huang <haitao.huang@linux.intel.com>
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

Sean, would be cool if you can try this out soonish because I'm
building on top of this.

I tried you vdso change on a GLK NUC and they seem to work.

/Jarkko