[PATCH] Not append rela for abs_symbol

[Xi Ruoyao]

On Thu, 2024-08-15 at 14:12 +0800, Xin Wang wrote:
> LoongArch: Not append rela for absolute symbol
> 
> Use la.global to get absolute symbol like la.abs.
> la.global put address of a global symbol into got and
> append a rela for it, which will be used to relocate by
> dynamic linker. Dynamic linker should not relocate for
> got entry of absolute symbol as it stores symval not
> symbol's address.
> 
> Signed-off-by: Xin Wang <wangxin03@loongson.cn>

You shouldn't use S-o-b if this is done as a Loongson employee (in the
working time): the attribution should belong to the Loongson company,
and the company uses FSF copyright assignment instead of DCO.

Some comment follows.

/* snip */

> @@ -5482,7 +5485,18 @@ loongarch_elf_relax_section (bfd *abfd,
> asection *sec,
>  	  break;
>  
>  	case R_LARCH_GOT_PC_HI20:
> +	  if (h)
> +	    is_abs_symbol = bfd_is_abs_section(h-
> >root.u.def.section);
> +	  else
> +	    {
> +	      Elf_Internal_Sym *sym = (Elf_Internal_Sym *)symtab_hdr-
> >contents
> +				    + ELFNN_R_SYM (rel->r_info);
> +	      is_abs_symbol = sym->st_shndx == SHN_ABS;
> +	    }
>  	  if (local_got && 0 == info->relax_pass
> +	      // We can not change the r_type which will be
> +	      // needed when relocate for absolute symbol.

AFAIK BFD code base prefer /* ... */ over //.

Technically we can relax pcalau12i + ld.d to lu12i.w + ori if the
absolute symbol is in [-2^31, 2^31), and then r_type can be changed to
R_LARCH_ABS_{HI20,LO12}.  It's OK not to implement this in the patch,
but the comment should say "not implemented yet" instead of "cannot."

> +	      && !is_abs_symbol
>  	      && (i + 4) <= sec->reloc_count)
>  	    {
>  	      if (loongarch_relax_pcala_ld (abfd, sec, rel))

A test case should be added into ld/testsuite/ld-loongarch-elf/ld-
loongarch-elf.exp.

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University