Re: PATCH: PR ld/3958: ELF linker failed to handle relocation against ABS section

[Alan Modra <amodra at bigpond dot net dot au>]

On Sat, Feb 03, 2007 at 11:58:12AM -0800, H. J. Lu wrote:
[snip]
> 	* elflink.c (elf_link_input_bfd): Don't remove the symbol
> 	reference from relocations against symbols from removed input
> 	section.
[snip]
> --- binutils/bfd/elflink.c.abs	2007-02-03 09:11:04.000000000 -0800
> +++ binutils/bfd/elflink.c	2007-02-03 11:52:45.000000000 -0800
> @@ -7754,14 +7754,17 @@ elf_link_input_bfd (struct elf_final_lin
>  			    }
>  			}
>  
> -		      /* Remove the symbol reference from the reloc, but
> -			 don't kill the reloc completely.  This is so that
> -			 a zero value will be written into the section,
> -			 which may have non-zero contents put there by the
> -			 assembler.  Zero in things like an eh_frame fde
> -			 pc_begin allows stack unwinders to recognize the
> -			 fde as bogus.  */
> -		      rel->r_info &= r_type_mask;
> +		      /* We can't use relocation against STN_UNDEF to
> +			 indicate that a relocation entry is against a
> +			 symbol from a removed input section since it is
> +			 used for relocation against constant.  See
> +			 PR 3958.  We need to use elf_discarded_section
> +			 to check if a zero value should be be written
> +			 into the section, which may have non-zero
> +			 contents put there by the assembler.  Zero
> +			 in things like an eh_frame fde pc_begin
> +			 allows stack unwinders to recognize the fde as
> +			 bogus.  */
>  		      rel->r_addend = 0;
>  		    }

Have you checked how "ld -r" and "ld --emit-relocs" are affected by
this change?  I suspect breakage..

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre