Re: [PATCH 03/16] x86/entry/32: Leave the kernel via the trampoline stack

[Joerg Roedel]

On Wed, Jan 17, 2018 at 05:57:53AM -0800, Brian Gerst wrote:
> On Wed, Jan 17, 2018 at 1:24 AM, Joerg Roedel <joro@xxxxxxxxxx> wrote:

> > I have no real idea on how to switch back to the entry stack without
> > access to per_cpu variables. I also can't access the cpu_entry_area for
> > the cpu yet, because for that we need to be on the entry stack already.
> 
> Switch to the trampoline stack before loading user segments.

That requires to copy most of pt_regs from task- to trampoline-stack,
not sure if that is faster than temporily restoring kernel %fs.


	Joerg