On Thu, 2014-08-07 at 19:42 +0400, Max Filippov wrote: > On Thu, Aug 7, 2014 at 7:32 PM, Nicolas Pitre <nicolas.pi...@linaro.org> > wrote: > > On Thu, 7 Aug 2014, Rob Herring wrote: > > > >> On Thu, Aug 7, 2014 at 10:15 AM, Max Filippov <jcmvb...@gmail.com> wrote: > >> > Hi, > >> > > >> > On Wed, Aug 6, 2014 at 11:32 PM, Kees Cook <keesc...@chromium.org> wrote: > >> >> ARM is different from other architectures in that fixmap pages are > >> >> indexed > >> >> with a positive offset from FIXADDR_START. Other architectures index > >> >> with > >> >> a negative offset from FIXADDR_TOP. In order to use the generic > >> >> fixmap.h > >> > > >> > Does anybody know if there's any reason why generic fixmap.h uses > >> > negative > >> > offsets? It complicates things with no obvious benefit if you e.g. try > >> > to align > >> > virtual address in the fixmap region with physical page color (that's > >> > why I've > >> > switched xtensa to positive fixmap addressing in v3.17). > >> > >> No, but each arch doing it differently is even more annoying. > > > > Why not switching everybody to positive offsets then? > > I can cook a patch if people agree that that'd be good. >
I think that would be fine. I think x86 was first and used a negative negative offset. Others that followed just copied that. When I did the generic fixmap patch, using a negative offset was the natural thing to do. Arm was only arch doing it differently. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
