Re: [Fwd: RE: elf header bits for page migration support......]

["H. J. Lu" <hjl@lucon.org>]

On Sun, May 15, 2005 at 12:25:23PM -0700, Jack Carter wrote:
> Ray Bryant wrote:
> 
> >2/2
> >
> >-------- Original Message --------
> >Subject: RE: elf header bits for page migration support......
> >Date: Fri, 13 May 2005 10:54:11 -0700
> >From: Luck, Tony <tony.luck@intel.com>
> >To: Ray Bryant <raybry@engr.sgi.com>
> >CC: <linux-ia64@vger.kernel.org>
> >
> >>The alternative being suggested is to mark the elf header of object 
> >>files
> >>that should only have shared pages migrated, or that should not be 
> >>migrated
> >>(e. g. you don't want to migrate /bin/csh all the time.)
> >
> >
> >No ... I'd like you to replicate shared pages (of /bin/bash ... I 
> >personally don't
> >care what happens to the pages of /bin/csh :-)
> >
> >>Can I use some bits (I need 2) of p_flags of Elf64_Phdr for this 
> >>purpose?
> >>If so, which bits?
> >>
> >>If not which other fields can I use?
> >
> >
> >I think H.J's suggestion of an extra section makes sense ... then you 
> >can go
> >wild with as many bits as you can dream up uses for, rather than 
> >constraining
> >yourself to squeeze into just 2 bits.
> >
> >-Tony
> >
> >
> The fun part of  this is that if you introduce a new section and
> a new segment to point to it (only segments exist at load time)
> then you need to really muck with the bits because you will be
> growing the program header (segment table) and the section header
> as well as putting in a new section.
> 
> If this information is to be used by rld it will need to be in some
> element of the bits that will be loadable and that means the new
> section needs to be either contiguous to a currently marked (PT_LOAD)
> segment with it's size increase due to the new section or the new section
> needs to be in it's own segment which means increasing the number
> of PT_LOAD segment entries.

I am not sure I understand what you are saying. As far as I know,
you don't need PT_LOAD for it. The dynamic linker will handle it in
program header just fine.


H.J.