Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack

[Yu, Yu-cheng]

On 8/24/2020 5:36 PM, Andy Lutomirski wrote:
> On Mon, Aug 24, 2020 at 5:30 PM Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> wrote:
>
> > arch_prctl(ARCH_X86_CET_MMAP_SHSTK, u64 *args)
> >      Allocate a new shadow stack.
> >
> >      The parameter 'args' is a pointer to a user buffer.
> >
> >      *args = desired size
> >      *(args + 1) = MAP_32BIT or MAP_POPULATE
> >
> >      On returning, *args is the allocated shadow stack address.
>
> This is hideous.  Would this be better as a new syscall?

Could you point out why this is hideous, so that I can modify the 
arch_prctl?

I think this is more arch-specific.  Even if it becomes a new syscall, 
we still need to pass the same parameters.

Yu-cheng