[Hardy] SRU: XEN: on amd64 does not honour MAP_32BIT flag

[Stefan Bader]

Chuck, maybe you can have a look at this, too. Does this look good for you as well?

SRU justification:

Impact: The 64bit XEN kernel does not honour the MAP_32BIT flag. This reason 
for this is a change that removed the arch_get_unmapped_area_topdown() function 
from the code (probably to resolve a defined twice error)

Fix: attached patch to restore the architecture specific function and to define 
ARCH_HAVE_UNMAPPED_AREA_TOPDOWN

Testcase: running mono applications on 64bit XEN kernels.




James Troup wrote:
> Hi,
> 
> Could we please get the patch in:
> 
>   <https://bugs.launchpad.net/ubuntu/+source/linux/+bug/237724>
> 
> into the next hardy SRU?  The current kernel makes it impossible for
> mono users and developers to use Launchpad PPAs on amd64 machines.  
> 
> I'm obviously biased (since I wrote it), but the patch strikes me as
> obviously correct and safe.  AFAICT, when the Xen merge was done,
> sys_x86_64.c was reverted to it's 2.6.18 state to fix a
> 'defined-twice' compile time error, rather than simply updating Xen's
> copy of pgtable_64.h to define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN as the
> non-Xen version does.
> 
> In any event, I've tested the patch, it's in active use on one of the
> PPA builders and hasn't shown any problems so far and does fix mono.
> The change is also completely isolated to Xen and can't possibly
> affect non-Xen kernels.
> 
> Thanks
> 
-- 

When all other means of communication fail, try words!


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