Special ELF section flags vs. linker-specified bfd flags

Richard Sandiford richard@codesourcery.com
Wed Oct 18 13:09:00 GMT 2006

There seems to be a bad interaction between:

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


2006-08-01  H.J. Lu  <hongjiu.lu@intel.com>

	* ldlang.c (init_os): Add flags. Replace bfd_make_section with
	(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?


	* elf.c (_bfd_elf_init_private_section_data): Copy the ELF section
	flags as well as the section type.

Index: bfd/elf.c
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.359
diff -u -p -r1.359 elf.c
--- bfd/elf.c	15 Oct 2006 14:22:13 -0000	1.359
+++ bfd/elf.c	18 Oct 2006 10:10:31 -0000
@@ -5954,7 +5954,10 @@ _bfd_elf_init_private_section_data (bfd 
      section flags.  */
   if (osec->flags == isec->flags
       || (osec->flags == 0 && elf_section_type (osec) == SHT_NULL))
-    elf_section_type (osec) = elf_section_type (isec);
+    {
+      elf_section_type (osec) = elf_section_type (isec);
+      elf_section_flags (osec) = elf_section_flags (isec);
+    }
   /* Set things up for objcopy and relocatable link.  The output
      SHT_GROUP section will have its elf_next_in_group pointing back

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