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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


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