[binutils-gdb] Fix the linker so that it will not silently generate ELF binaries with invalid program headers. Fix

[Alan Modra]

On Thu, Dec 08, 2016 at 12:14:49PM +0000, Nick Clifton wrote:
> Hi Alan,
> 
> > I think an equally valid and somewhat better fix would have been to not
> > emit PT_PHDR when no PT_LOAD header covers the program headers.  The
> > reason I say that is because PT_PHDR is optional.  A loader can read
> > the program headers itself from file using info in the ELF header.
> 
> That would be nicer, but there is explicit code in _bfd_elf_map_sections_to_segments()
> to create a PHDR segment whenever we create an INTERP segment.  I assumed
> that this was a requirement and hence could not be dropped.  (I did not
> explore why this was needed, I just assumed that I would break something,
> probably the kernel, if I dropped the requirement).

OK, so I experimented with a patch that omits PHDR when a script
doesn't leave enough room, and "hello world" no longer runs on Ubuntu
16.04.  Segfault in dl_main.  So it seems INTERP really does need
PHDR, at least with current glibc ld.so.

-- 
Alan Modra
Australia Development Lab, IBM