[PATCH-WIP 01/13] xen/arm: use r12 to pass the hypercall number to the hypervisor

Ian Campbell Ian.Campbell at citrix.com
Wed Feb 29 09:56:02 UTC 2012


On Wed, 2012-02-29 at 09:34 +0000, Dave Martin wrote:
> On Tue, Feb 28, 2012 at 12:28:29PM +0000, Stefano Stabellini wrote:

> > I don't have a very strong opinion on which register we should use, but
> > I would like to avoid r7 if it is already actively used by gcc.
> 
> But there is no framepointer for Thumb-2 code (?)

Peter Maydell suggested there was:
> r7 is (used by gcc as) the Thumb frame pointer; I don't know if this
> makes it worth avoiding in this context.

Sounds like it might be a gcc-ism, possibly a non-default option?

Anyway, I think r12 will be fine for our purposes so the point is rather
moot.

Ian.




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