Reserving a bit in ELF segment flags for huge page mappings

[Sriraman Tallam]

Hi,

    I am working on a patch to allow subsets of text sections to be
mapped to different ELF segments :
http://sourceware.org/ml/binutils/2012-07/msg00153.html using linker
plugins.

    This will allow splitting hot and cold functions into separate
segments so that only the hot segment can be then mapped to text huge
pages. It has been found for some Google applications that mapping
functions to huge pages, along with function layout, provides a
significant performance benefit and this feature can take this further
by only mapping certain functions to huge pages.

  To do this, I would like to reserve a bit in the segment flags to
indicate that this segment is to be mapped to huge pages if possible.
Can I reserve something like a PF_LARGE_PAGE bit?

Thanks,
-Sri.