[RFC PATCH 4/9] um: Add stub side of SECCOMP/futex based process handling

[Benjamin Berg]

On Thu, 2024-10-10 at 13:51 +0200, Johannes Berg wrote:
> On Wed, 2024-09-25 at 22:32 +0200, Benjamin Berg wrote:
> > 
> > --- /dev/null
> > +++ b/arch/x86/um/shared/sysdep/stub-data.h
> > @@ -0,0 +1,18 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> 
> That new file should possibly have double-include guards as common.
> 
> Can we use #pragma once yet? ;)

Can we? That would be really nice!

> > +static __always_inline void
> > +stub_seccomp_restore_state(struct stub_data_arch *arch)
> > +{
> > +	/* TODO: Use _writefsbase_u64/_writegsbase_u64 when
> > possible */
> 
> Don't remember that, what was that about?

Don't think we ever discussed that. I think those map to instructions
that directly set the registers from userspace. But I feel like there
was no guarantee that this works on all machines/CPUs so the syscall
may still be needed.

Benjamin