Re: Special ELF section flags vs. linker-specified bfd flags

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

On Wed, Oct 18, 2006 at 11:15:32AM +0100, Richard Sandiford wrote:
> There seems to be a bad interaction between:
> 
> bfd/
> 2006-04-26  H.J. Lu  <hongjiu.lu@intel.com>
> 
> 	PR binutils/2593
> 	* elf.c (_bfd_elf_new_section_hook): Don't set section ELF type
> 	and flags if its BFD flags have been set.
> 	(_bfd_elf_init_private_section_data): Don't copy the output ELF
> 	section type from input if it has been set to something
> 	different.
> 
> and:
> 
> ld/
> 2006-08-01  H.J. Lu  <hongjiu.lu@intel.com>
> 
> 	* ldlang.c (init_os): Add flags. Replace bfd_make_section with
> 	bfd_make_section_with_flags.
> 	(exp_init_os): Updated.
> 	(lang_add_section): Call init_os with flags.
> 	(map_input_to_output_sections): Likewise.
> 
> The _bfd_elf_new_section_hook hunk was:
> 
>    bed = get_elf_backend_data (abfd);
>    sec->use_rela_p = bed->default_use_rela_p;
>  
> -  /* When we read a file, we don't need section type and flags unless
> -     it is a linker created section.  They will be overridden in
> -     _bfd_elf_make_section_from_shdr anyway.  */
> -  if (abfd->direction != read_direction
> +  /* When we read a file or section BFD flags have been set, we don't
> +     need section type and flags unless it is a linker created section.
> +     They will be overridden in _bfd_elf_make_section_from_shdr
> +     anyway.  */
> +  if ((!sec->flags && abfd->direction != read_direction)
>        || (sec->flags & SEC_LINKER_CREATED) != 0)
>      {
>        ssect = (*bed->get_sec_type_attr) (abfd, sec);
> 
> but the later linker change makes init_os propagate the input section's
> bfd flags to the new output section.  We therefore skip the get_sec_type_attr
> stuff for normal sections, even though the user hasn't overridden the flags.
> This in turn means we miss target-specific SHF_* flags that have no
> corresponding bfd section flag.
> 
> This caused reloc-1-rel.d and reloc-1-n32.d to fail on MIPS.  This loop:
> 
>       else if (info->relocatable)
> 	{
> 	  bfd_vma lo = MINUS_ONE;
> 
> 	  /* Find the GP-relative section with the lowest offset.  */
> 	  for (o = abfd->sections; o != NULL; o = o->next)
> 	    if (o->vma < lo
> 		&& (elf_section_data (o)->this_hdr.sh_flags & SHF_MIPS_GPREL))
> 	      lo = o->vma;
> 
> 	  /* And calculate GP relative to that.  */
> 	  elf_gp (abfd) = lo + ELF_MIPS_GP_OFFSET (info);
> 	}
> 
> wouldn't see any SHF_MIPS_GPREL sections, and would use -1 as the
> GP value.
> 
> I think the fix below is in the spirit of HJ's other changes.
> Patch tested on mips{,64}{,el}-{elf,linux-gnu} and mips-sgi-irix6.5.
> OK to install?
> 

"makec check" failed in ld on Linux/x86-64:

FAIL: Run with libdl3a.so
FAIL: Run with libdl3b.so
FAIL: Run with libdl3c.so
...
ERROR: tmpdir/3.x: nm failed
ERROR: tmpdir/4.x: nm failed
ERROR: tmpdir/5.x: nm failed


H.J.