[PATCH] elf: Cache ".interp" section pointer in elf_link_hash_table

[Alan Modra]

On Sun, Sep 14, 2025 at 02:54:11PM -0700, H.J. Lu wrote:
> If there is no interpreter (no ".interp" sectio), weak undefined symbols
> will always be zero at run-time.  Cache ".interp" section pointer in
> elf_link_hash_table so that a backend can use it to check if weak
> undefined symbols should be resolved to zero at link-time.

Since you are moving this to the main elf_link_hash_table, I assume
you have a followup patch that updates occurrences of
	bfd_get_linker_section (dynobj, ".interp");
If so this patch is OK and I'll preapprove the bfd_get_linker_section
changes.

> 	PR ld/33427
> 	* elf-bfd.h (elf_link_hash_table): Add interp.
> 	* elflink.c (_bfd_elf_link_create_dynamic_sections): Cache the
> 	pointer to ".interp" section in interp.
> 	* elfxx-x86.c (_bfd_x86_elf_link_symbol_references_local): Check
> 	htab->elf.interp instead of htab->interp.
> 	(_bfd_x86_elf_link_setup_gnu_properties): Use htab->elf.interp.
> 	* elfxx-x86.h (elf_x86_link_hash_table): Remove interp.
> 
> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
> ---
>  bfd/elf-bfd.h   | 1 +
>  bfd/elflink.c   | 1 +
>  bfd/elfxx-x86.c | 7 ++-----
>  bfd/elfxx-x86.h | 1 -
>  4 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
> index de7cc410a99..51e6ae7bb78 100644
> --- a/bfd/elf-bfd.h
> +++ b/bfd/elf-bfd.h
> @@ -774,6 +774,7 @@ struct elf_link_hash_table
>    asection *dynsym;
>    asection *srelrdyn;
>    asection *dynamic;
> +  asection *interp;
>  };
>  
>  /* Returns TRUE if the hash table is a struct elf_link_hash_table.  */
> diff --git a/bfd/elflink.c b/bfd/elflink.c
> index 53ec792852c..b8ffcab419c 100644
> --- a/bfd/elflink.c
> +++ b/bfd/elflink.c
> @@ -354,6 +354,7 @@ _bfd_elf_link_create_dynamic_sections (bfd *abfd, struct bfd_link_info *info)
>  					      flags | SEC_READONLY);
>        if (s == NULL)
>  	return false;
> +      elf_hash_table (info)->interp = s;
>      }
>  
>    /* Create sections to hold version informations.  These are removed
> diff --git a/bfd/elfxx-x86.c b/bfd/elfxx-x86.c
> index 06265ee4e15..4ca4c3a3948 100644
> --- a/bfd/elfxx-x86.c
> +++ b/bfd/elfxx-x86.c
> @@ -3665,7 +3665,7 @@ _bfd_x86_elf_link_symbol_references_local (struct bfd_link_info *info,
>        || (h->root.type == bfd_link_hash_undefweak
>  	  && (ELF_ST_VISIBILITY (h->other) != STV_DEFAULT
>  	      || (bfd_link_executable (info)
> -		  && htab->interp == NULL)
> +		  && htab->elf.interp == NULL)
>  	      || info->dynamic_undefined_weak == 0))
>        || ((h->def_regular || ELF_COMMON_DEF_P (h))
>  	  && info->version_info != NULL
> @@ -4704,13 +4704,10 @@ _bfd_x86_elf_link_setup_gnu_properties
>  	 section to the interpreter.  */
>        if (bfd_link_executable (info) && !info->nointerp)
>  	{
> -	  asection *s = bfd_get_linker_section (dynobj, ".interp");
> -	  if (s == NULL)
> -	    abort ();
> +	  asection *s = htab->elf.interp;
>  	  s->size = htab->dynamic_interpreter_size;
>  	  s->contents = (unsigned char *) htab->dynamic_interpreter;
>  	  s->alloced = 1;
> -	  htab->interp = s;
>  	}
>  
>        if (normal_target)
> diff --git a/bfd/elfxx-x86.h b/bfd/elfxx-x86.h
> index 5593203f9ec..1ebc9d2f2e5 100644
> --- a/bfd/elfxx-x86.h
> +++ b/bfd/elfxx-x86.h
> @@ -602,7 +602,6 @@ struct elf_x86_link_hash_table
>    struct elf_link_hash_table elf;
>  
>    /* Short-cuts to get to dynamic linker sections.  */
> -  asection *interp;
>    asection *plt_eh_frame;
>    asection *plt_second;
>    asection *plt_second_eh_frame;
> -- 
> 2.51.0

-- 
Alan Modra