[PATCH v5 1/2] ld: bfd: sframe: KEEP .sframe sections and support gc-sections

[Indu Bhagat]

On 1/27/26 12:45 PM, claudiu.zissulescu-ianculescu@oracle.com wrote:
> From: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
> 
> Fix PR ld/32769
> 
> Currently, specifying --gc-sections causes the linker to discard all
> input .sframe sections.  Fix this behaviour by adding KEEP for .sframe
> sections, like it is being done for .eh_frame sections, in the default
> ELF linker script.
> 
> Additionally, add logic in the linker to gc mark .sframe sections.
> _bfd_elf_gc_mark () now is aware of SFrame sections. It relies on
> elf_section_sframe () to get the SFrame section associated with the
> text section.
> 
> Also, the _bfd_elf_parse_sframe is changed to return TRUE when the
> input sframe section is already parsed. It fixes calling
> _bfd_elf_discard_section_sframe function in bfd_elf_discard_info,
> enabling correct behavior for discarding unneeded sframe sections.
> 
> ld/
> 	PR ld/32769
> 	* scripttempl/elf.sc: KEEP .sframe sections.
> bfd/
> 	* elf-bfd.h (struct elf_obj_tdata): Add sframe section pointer.
> 	(elf_sframe_section): New macro.
> 	* elflink.c (_bfd_elf_gc_mark): Handle SFrame sections.
> 	(bfd_elf_gc_sections): Likewise.
> 	(bfd_elf_discard_info): Update for handling gc operations.
> 	* elf-sframe.c (_bfd_elf_parse_sframe): Return TRUE for already
> 	parsed sframe sections.
> 
> Co-authored-by: Indu Bhagat <indu.bhagat@oracle.com>
> Reviewed-by: Jens Remus <jremus@linux.ibm.com>
> Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>

LGTM, one nit below.

Thanks

> ---
>   bfd/elf-bfd.h         |  5 +++++
>   bfd/elf-sframe.c      |  8 ++++++--
>   bfd/elflink.c         | 22 ++++++++++++++++++++--
>   ld/scripttempl/elf.sc |  4 ++--
>   4 files changed, 33 insertions(+), 6 deletions(-)
> 
> diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
> index c833b7d101b..94525b3606e 100644
> --- a/bfd/elf-bfd.h
> +++ b/bfd/elf-bfd.h
> @@ -2177,6 +2177,9 @@ struct elf_obj_tdata
>     /* A pointer to the .eh_frame section.  */
>     asection *eh_frame_section;
>   
> +  /* A pointer to the .sframe section.  */
> +  asection *sframe_section;
> +
>     /* Symbol buffer.  */
>     void *symbuf;
>   
> @@ -2258,6 +2261,8 @@ struct elf_obj_tdata
>   #define elf_dynverref(bfd)	(elf_tdata(bfd) -> dynverref_section)
>   #define elf_eh_frame_section(bfd) \
>   				(elf_tdata(bfd) -> eh_frame_section)
> +#define elf_sframe_section(bfd) \
> +				(elf_tdata(bfd) -> sframe_section)
>   #define elf_section_syms(bfd)	(elf_tdata(bfd) -> o->section_syms)
>   #define elf_num_section_syms(bfd) (elf_tdata(bfd) -> o->num_section_syms)
>   #define core_prpsinfo(bfd)	(elf_tdata(bfd) -> prpsinfo)
> diff --git a/bfd/elf-sframe.c b/bfd/elf-sframe.c
> index 77d9d33d602..afcf82f370b 100644
> --- a/bfd/elf-sframe.c
> +++ b/bfd/elf-sframe.c
> @@ -245,13 +245,17 @@ _bfd_elf_parse_sframe (bfd *abfd,
>       }
>   
>     if (sec->size == 0
> -      || (sec->flags & SEC_HAS_CONTENTS) == 0
> -      || sec->sec_info_type != SEC_INFO_TYPE_NONE)
> +      || (sec->flags & SEC_HAS_CONTENTS) == 0)
>       {
>         /* This file does not contain .sframe information.  */
>         return false;
>       }
>   
> +  /* Check if this section is already parsed.  */
> +  if (sec->sec_info_type == SEC_INFO_TYPE_SFRAME)
> +    return true;
> +
> +

Nit: Extra newline

>     if (bfd_is_abs_section (sec->output_section))
>       {
>         /* At least one of the sections is being discarded from the
> diff --git a/bfd/elflink.c b/bfd/elflink.c
> index 64c1a57b465..b2a04631b7a 100644
> --- a/bfd/elflink.c
> +++ b/bfd/elflink.c
> @@ -14151,7 +14151,7 @@ _bfd_elf_gc_mark (struct bfd_link_info *info,
>   		  elf_gc_mark_hook_fn gc_mark_hook)
>   {
>     bool ret;
> -  asection *group_sec, *eh_frame;
> +  asection *group_sec, *eh_frame, *sframe;
>   
>     sec->gc_mark = 1;
>   
> @@ -14164,9 +14164,12 @@ _bfd_elf_gc_mark (struct bfd_link_info *info,
>     /* Look through the section relocs.  */
>     ret = true;
>     eh_frame = elf_eh_frame_section (sec->owner);
> +  sframe = elf_sframe_section (sec->owner);
> +
>     if ((sec->flags & SEC_RELOC) != 0
>         && sec->reloc_count > 0
> -      && sec != eh_frame)
> +      && sec != eh_frame
> +      && sec != sframe)
>       {
>         struct elf_reloc_cookie cookie;
>   
> @@ -14703,6 +14706,21 @@ bfd_elf_gc_sections (bfd *abfd, struct bfd_link_info *info)
>   	  fini_reloc_cookie_for_section (&cookie, sec);
>   	  sec = bfd_get_next_section_by_name (NULL, sec);
>   	}
> +
> +      /* Handle .sframe section.  */
> +      sec = bfd_get_section_by_name (sub, ".sframe");
> +      while (sec && init_reloc_cookie_for_section (&cookie, info, sec,
> +						   false))
> +	{
> +	  _bfd_elf_parse_sframe (sub, info, sec, &cookie);
> +
> +	  if (sec->sec_info
> +	      && (sec->flags & SEC_LINKER_CREATED) == 0)
> +	    elf_sframe_section (sub) = sec;
> +
> +	  fini_reloc_cookie_for_section (&cookie, sec);
> +	  sec = bfd_get_next_section_by_name (NULL, sec);
> +	}
>       }
>   
>     /* Apply transitive closure to the vtable entry usage info.  */
> diff --git a/ld/scripttempl/elf.sc b/ld/scripttempl/elf.sc
> index 80b4b512536..8a0efc02c86 100644
> --- a/ld/scripttempl/elf.sc
> +++ b/ld/scripttempl/elf.sc
> @@ -719,7 +719,7 @@ cat <<EOF
>     ${OTHER_READONLY_SECTIONS}
>     .eh_frame_hdr ${RELOCATING-0} : { *(.eh_frame_hdr)${RELOCATING+ *(.eh_frame_entry .eh_frame_entry.*)} }
>     .eh_frame     ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.eh_frame))${RELOCATING+ *(.eh_frame.*)} }
> -  .sframe       ${RELOCATING-0} : ONLY_IF_RO { *(.sframe)${RELOCATING+ *(.sframe.*)} }
> +  .sframe       ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.sframe))${RELOCATING+ *(.sframe.*)} }
>     .gcc_except_table ${RELOCATING-0} : ONLY_IF_RO { *(.gcc_except_table${RELOCATING+ .gcc_except_table.*}) }
>     .gnu_extab ${RELOCATING-0} : ONLY_IF_RO { *(.gnu_extab*) }
>   
> @@ -794,7 +794,7 @@ emit_data()
>   cat <<EOF
>     /* Exception handling.  */
>     .eh_frame     ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.eh_frame))${RELOCATING+ *(.eh_frame.*)} }
> -  .sframe       ${RELOCATING-0} : ONLY_IF_RW { *(.sframe)${RELOCATING+ *(.sframe.*)} }
> +  .sframe       ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.sframe))${RELOCATING+ *(.sframe.*)} }
>     .gnu_extab    ${RELOCATING-0} : ONLY_IF_RW { *(.gnu_extab) }
>     .gcc_except_table ${RELOCATING-0} : ONLY_IF_RW { *(.gcc_except_table${RELOCATING+ .gcc_except_table.*}) }
>     .exception_ranges ${RELOCATING-0} : ONLY_IF_RW { *(.exception_ranges${RELOCATING+*}) }