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

[Dave Martin]

On Tue, Aug 25, 2020 at 04:34:27PM -0700, Yu, Yu-cheng wrote:
> On 8/25/2020 4:20 PM, Dave Hansen wrote:
> >On 8/25/20 2:04 PM, Yu, Yu-cheng wrote:
> >>>>I think this is more arch-specific.  Even if it becomes a new syscall,
> >>>>we still need to pass the same parameters.
> >>>
> >>>Right, but without the copying in and out of memory.
> >>>
> >>Linux-api is already on the Cc list.  Do we need to add more people to
> >>get some agreements for the syscall?
> >What kind of agreement are you looking for?  I'd suggest just coding it
> >up and posting the patches.  Adding syscalls really is really pretty
> >straightforward and isn't much code at all.
> >
> 
> Sure, I will do that.

Alternatively, would a regular prctl() work here?

arch_prctl() feels like a historical weirdness for x86 -- other arches
all seem to be using regular prctl(), which allows for 4 args.  I don't
know the history behind the difference here.

(Since prctl() and arch_prctl() use non-clashing command numbers, I had
wondered whether it would be worth just merging the x86 calls in with
the rest and making the two calls aliases.  That's one for later,
though...)

Cheers
---Dave