On Thu, 2014-08-07 at 19:42 +0400, Max Filippov wrote:

On Thu, Aug 7, 2014 at 7:32 PM, Nicolas Pitre [off-list ref] wrote:

quoted

On Thu, 7 Aug 2014, Rob Herring wrote:

quoted

On Thu, Aug 7, 2014 at 10:15 AM, Max Filippov [off-list ref] wrote:

quoted

Hi,

On Wed, Aug 6, 2014 at 11:32 PM, Kees Cook [off-list ref] wrote:

quoted

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.