Re: [PATCH 3/3] x86_64: Use relative per-cpu offsets

[H. Peter Anvin]

On 11/13/21 17:18, Andy Lutomirski wrote:
> On Sat, Nov 13, 2021, at 4:40 AM, Brian Gerst wrote:
> > The per-cpu section is currently linked at virtual address 0, because
> > older compilers hardcoded the stack protector canary value at a fixed
> > offset from the start of the GS segment.  Use a standard relative offset
> > as the GS base when the stack protector is disabled, or a newer compiler
> > is used that supports a configurable location for the stack canary.
>
> Can you explain the benefit?  Also, I think we should consider dropping support for the fixed model like we did on x86_32.

It would seem that UNLESS the fixed model is dropped, the benefit is 
probably negative.

	-hpa