Re: [Xen-devel] [PATCH v6 14/27] x86/percpu: Adapt percpu for PIE support

[Thomas Garnier <thgarnie@xxxxxxxxxxxx>]

On Mon, Apr 8, 2019 at 10:56 AM Christopher Lameter <cl@xxxxxxxxx> wrote:
>
> On Mon, 8 Apr 2019, Thomas Garnier wrote:
>
> > > It didn't work originally but I will revisit to see if I missed something.
> >
> > I revisited and couldn't find a way to prevent relocations to the
> > percpu section. Without PIE, you can reference absolute address which
> > was convenient for percpu.
>
> Can you switch PIE off for the percpu section? If not maybe the linker
> needs to have an additional option?

I don't think so or I didn't find any option to do that. Changing the
linker might be a bit too much if we have a software solution which
doesn't impact performance.

>
> Cannot imagine that this is not possible. You neeed to be able to
> reference registers that are in fixed memory locations.
>
>
> > Christopher: Did you have something specific in mind?
>
> I thought that we just leave it as is.

I would like to as well. I will try couple things at the assembly
level instead of the linker and come back to this thread.

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