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PATCH: SHN_XINDEX support is broken

H. J. Lu hjl@lucon.org
Mon Feb 7 03:41:00 GMT 2005 
On Sun, Feb 06, 2005 at 11:48:10PM +1030, Alan Modra wrote:
> 
> "SHT_GROUP sections are typically ordered before SHT_SYMTAB and
> SHT_SYMTAB_SHNDX in the ELF section headers, and thus are loaded by
> elf_object_p before the symbol table sections.  When loading a group
> section, bfd_section_from_shdr calls group_signature to read a symbol
> name associated with the group.  group_signature ensures that the
> SHT_SYMTAB section is loaded, but doesn't load SHT_SYMTAB_SHNDX.  This
> can lead to an abort if the symbol st_shndx is SHN_XINDEX."
> 
> > > It only works without SHN_XINDEX
> > > since SHT_REL/SHT_RELA sections will load SHT_SYMTAB. The problem
> > > affects both bfd and readelf. I will see what I can do.
> > > 
> > 
> > 2005-02-04  H.J. Lu  <hongjiu.lu@intel.com>
> > 
> > 	* elfcode.h (elf_object_p): Read in SHT_SYMTAB and
> > 	SHT_SYMTAB_SHNDX sections first.
> 
> I don't think this is the best place to fix this problem.  One reason is
> that elfcode.h is compiled twice, once for 32-bit support and once for
> 64-bit, so we should avoid adding code to elfcode.h if at all possible.
> Another reason is that bfd_section_from_shdr already handles a number of
> similar section dependecies, so that's where I would add code to load
> SHT_SYMTAB_SHNDX when handling SHT_SYMTAB.
> 
> Like this.  Plus a few cleanups and minor optimizations.  I'll commit in
> the morning assuming my overnight tests look good.
> 
> 	* elf-bfd.h (elf_string_from_elf_strtab): Delete macro.
> 	* elf.c (bfd_elf_string_from_elf_section): Expand occurrence of
> 	elf_string_from_elf_strtab.
> 	(_bfd_elf_setup_group_pointers, bfd_section_from_shdr): Likewise.
> 	(bfd_section_from_shdr): For SHT_SYMTAB, load SHT_SYMTAB_SHNDX too
> 	if it exists.  Don't do the reverse for SHT_SYMTAB_SHNDX.  For
> 	SHT_STRTAB, check whether the strtab is for symtab or dynsymtab by
> 	looking at cached symtab info first, before iterating over headers.
> 	For SHT_REL and SHT_RELA, load dynsymtab if needed.
> 	* elfcode.h (elf_object_p): Don't load section header stringtab
> 	specially.
> 

I have been looking at the change. I am not 100% sure if it will be
always correct. Will the symbol table be read in by SHT_REL/SHT_RELA?
What if a file doesn't have them and does have SHT_GROUP? I will try
to come up with a testcase for that.


H.J.
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