[2.43 PATCH] LoongArch: Fix broken DESC => IE transition for 2.43 branch

[Lulu Cai]

When I apply this patch on the 2.43 branch and compile with gcc 15, the 
following warning is triggered.

binutils-gdb/bfd/elfnn-loongarch.c: In function 
‘loongarch_elf_relax_section’:
binutils-gdb/bfd/elfnn-loongarch.c:5471:16: error: ‘symval’ may be used 
uninitialized [-Werror=maybe-uninitialized]
5471 | symval += rel->r_addend;
| ~~~~~~~^~~~~~~~~~~~~~~~~
binutils-gdb/bfd/elfnn-loongarch.c:5328:15: note: ‘symval’ was declared here
5328 | bfd_vma symval;
| ^~~~~~
cc1: all warnings being treated as errors

On 12/19/24 1:23 PM, Xi Ruoyao wrote:
> If code compiled with -fPIC -mtls-dialect=desc is linked into a PDE or
> PIE, and the code refers to external DSO symbols, we can produce broken
> link unit as check_relocs expects DESC => IE transition to happen and
> emits a TLS IE entry in the GOT, but a too early "continue" in
> relax_section actually jumps over the DESC => IE transition so the code
> sequence is unchanged and still expecting a TLS descriptor (instead of
> an IE entry) in the GOT.
>
> The bug is already fixed in master branch by commit 5c3d09c1855b
> ("LoongArch: Optimize the relaxation process") so this fix is only
> needed for the 2.43 branch.
>
> Reported-by: Icenowy Zheng <uwu@icenowy.me>
> Closes: https://gcc.gnu.org/PR118114
> Signed-off-by: Xi Ruoyao <xry111@xry111.site>
> ---
>   bfd/elfnn-loongarch.c | 43 ++++++++++++++++++++++---------------------
>   1 file changed, 22 insertions(+), 21 deletions(-)
>
> diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
> index 312707bb00b..1c34797c2e1 100644
> --- a/bfd/elfnn-loongarch.c
> +++ b/bfd/elfnn-loongarch.c
> @@ -5326,7 +5326,7 @@ loongarch_elf_relax_section (bfd *abfd, asection *sec,
>       {
>         char symtype;
>         bfd_vma symval;
> -      asection *sym_sec;
> +      asection *sym_sec = NULL;
>         bool local_got = false;
>         Elf_Internal_Rela *rel = relocs + i;
>         struct elf_link_hash_entry *h = NULL;
> @@ -5418,14 +5418,33 @@ loongarch_elf_relax_section (bfd *abfd, asection *sec,
>   	      symval = h->root.u.def.value;
>   	      sym_sec = h->root.u.def.section;
>   	    }
> -	  else
> -	    continue;
>   
>   	  if (h && LARCH_REF_LOCAL (info, h))
>   	    local_got = true;
>   	  symtype = h->type;
>   	}
>   
> +      /* If the conditions for tls type transition are met, type
> +	 transition is performed instead of relax.
> +	 During the transition from DESC->IE/LE, there are 2 situations
> +	 depending on the different configurations of the relax/norelax
> +	 option.
> +	 If the -relax option is used, the extra nops will be removed,
> +	 and this transition is performed in pass 0.
> +	 If the --no-relax option is used, nop will be retained, and
> +	 this transition is performed in pass 1.  */
> +      if (IS_LOONGARCH_TLS_TRANS_RELOC (r_type)
> +	  && (i + 1 != sec->reloc_count)
> +	  && ELFNN_R_TYPE (rel[1].r_info) == R_LARCH_RELAX
> +	  && loongarch_can_trans_tls (abfd, info, h, r_symndx, r_type))
> +	{
> +	  loongarch_tls_perform_trans (abfd, sec, rel, h, info);
> +	  r_type = ELFNN_R_TYPE (rel->r_info);
> +	}
> +
> +      if (!sym_sec)
> +	continue;
> +
>         if (sym_sec->sec_info_type == SEC_INFO_TYPE_MERGE
>   	   && (sym_sec->flags & SEC_MERGE))
>   	{
> @@ -5453,24 +5472,6 @@ loongarch_elf_relax_section (bfd *abfd, asection *sec,
>   
>         symval += sec_addr (sym_sec);
>   
> -      /* If the conditions for tls type transition are met, type
> -	 transition is performed instead of relax.
> -	 During the transition from DESC->IE/LE, there are 2 situations
> -	 depending on the different configurations of the relax/norelax
> -	 option.
> -	 If the -relax option is used, the extra nops will be removed,
> -	 and this transition is performed in pass 0.
> -	 If the --no-relax option is used, nop will be retained, and
> -	 this transition is performed in pass 1.  */
> -      if (IS_LOONGARCH_TLS_TRANS_RELOC (r_type)
> -	  && (i + 1 != sec->reloc_count)
> -	  && ELFNN_R_TYPE (rel[1].r_info) == R_LARCH_RELAX
> -	  && loongarch_can_trans_tls (abfd, info, h, r_symndx, r_type))
> -	{
> -	  loongarch_tls_perform_trans (abfd, sec, rel, h, info);
> -	  r_type = ELFNN_R_TYPE (rel->r_info);
> -	}
> -
>         switch (r_type)
>   	{
>   	case R_LARCH_ALIGN:
>
> base-commit: 834b779ad28c3cecb5ad91a1ab2af3c8453c3b3a