Re: [PATCH v3 02/31] arm64: Kernel booting and initialisation
From: Catalin Marinas
Date: Mon Sep 10 2012 - 10:54:05 EST
On Mon, Sep 10, 2012 at 03:48:20PM +0100, Arnd Bergmann wrote:
> On Monday 10 September 2012, Nicolas Pitre wrote:
> > On Mon, 10 Sep 2012, Arnd Bergmann wrote:
> > > On Monday 10 September 2012, Catalin Marinas wrote:
> > > > On Mon, Sep 10, 2012 at 06:53:39AM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > > I think a bunch of other architectures can have relocatable kernels, which
> > > is useful e.g. for kdump. It does imply a small runtime cost and may have
> > > other disadvantages though.
> > Relocatable in physical space is what kdump actually needs, and that's
> > what we already have here (as well as on ARM32 for that matter with
> > CONFIG_ARM_PATCH_PHYS_VIRT). Relocatable in the virtual space is costly
> > and we shouldn't need to go there.
> Ah, I see. I thought that the other architectures (powerpc and x86)
> doing this were actually building with -fPIC, but they do the same
> kind of early patching that we do.
On arm64 I don't have run-time code patching (yet) but a PHYS_OFFSET
variable set at boot time. It may prove useful to have run-time code
patching but that's just an optimisation that can be added later.
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