RFC: Add SHT_GNU_PHDRS

[Florian Weimer]

* Michael Matz:

> On Thu, 27 Sep 2018, Florian Weimer wrote:
>
>> I'm now under the impression that the bits that are PT_LOAD'ed all need 
>> to be covered by (allocated) sections.
>
> That is wrong.  Szabolcs is reading too much into some careless wording of 
> the ELF text that simply tries to convey the idea that usually segments 
> contents are the result of some sections combined by the link editor.  
> Sections are purely optional in the execution view.
>
> This section hack isn't necessary at all for what we need.  The link 
> editor merely needs to ensure that the program headers are part of some 
> loadable segment, either by placing it not at the start of the file 
> (though that would mean the ELF header isn't part of the loaded image, 
> which is desirable to have), or by creating such loadble segment if 
> necessary.
>
> No gABI extensions are needed.

That would certainly be nice.

Can we try to update the ELF specification to clarify this?  That should
give us additional feedback whether this reading of the specification is
correct.

Thanks,
Florian