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Re: PATCH: PR ld/5522: Section contents partially overwritten with zero
On Tue, Jan 08, 2008 at 05:25:42AM -0800, H.J. Lu wrote:
> On Tue, Jan 08, 2008 at 09:29:56PM +1030, Alan Modra wrote:
> > > >2007-12-27 H.J. Lu <hongjiu.lu@intel.com>
> > > >
> > > > PR ld/5522
> > > > * elflink.c (elf_link_input_bfd): Don't write out a section if
> > > > its output section is marked with SEC_NEVER_LOAD.
> >
> > ld.info gives an example of NOLOAD output sections saying "The
> > contents of the section will appear in the linker output file as
> > usual". NOLOAD sets SEC_NEVER_LOAD on the output section, therefore
> > not writing out the section here is wrong. I think we are suffering
> > bit rot. Probably partly my fault..
> >
> > >From what I can see of the history (I can't access private Cygnus CVS,
> > so can't see before 1999), it appears that SEC_NEVER_LOAD was
> > invented for COFF to mirror STYP_NOLOAD. I'm inclined to think it
> > should remain that way. ie. Only used in COFF code or in the generic
> > linker code to hanlde NOLOAD. ELF doesn't have an external section
> > flag similar to STYP_NOLOAD so SEC_NEVER_LOAD should not appear
> > anywhere in ELF specific code. SEC_LOAD is sufficient. Does anyone
> > have any enlightening comments?
> >
>
> bfd/section.c has
>
> . {* An instruction to the linker to not output the section
> . even if it has information which would normally be written. *}
> .#define SEC_NEVER_LOAD 0x200
>
> I don't know which one is correct.
Both.
bfd overloads SEC_NEVER_LOAD with different meanings for input and
output sections. For input sections, SEC_NEVER_LOAD does as per the
section.c comment; The section contents are replaced with padding.
For output sections, SEC_NEVER_LOAD is set via NOLOAD in a link
script.
--
Alan Modra
Australia Development Lab, IBM