[PATCH v4 1/2] ld: bfd: sframe: KEEP .sframe sections and support gc-sections

[claudiu.zissulescu-ianculescu@oracle.com]

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.

The stub changes in bfd_elf_discard_info skip checking the return
value of _bfd_elf_parse_sframe because it may have already been
parsed.

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.

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>

fix
---
 bfd/elf-bfd.h         |  5 +++++
 bfd/elflink.c         | 36 ++++++++++++++++++++++++++----------
 ld/scripttempl/elf.sc |  4 ++--
 3 files changed, 33 insertions(+), 12 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/elflink.c b/bfd/elflink.c
index 64c1a57b465..26db981dad3 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);
 	}
+
+      /* Now parse each .sframe section.  Point each .sframe section
+	 to each bfd.  */
+      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.  */
@@ -15302,15 +15320,13 @@ bfd_elf_discard_info (bfd *output_bfd, struct bfd_link_info *info)
 	  if (!init_reloc_cookie_for_section (&cookie, info, i, false))
 	    return -1;
 
-	  if (_bfd_elf_parse_sframe (abfd, info, i, &cookie))
+	  _bfd_elf_parse_sframe (abfd, info, i, &cookie);
+	  if (_bfd_elf_discard_section_sframe (i,
+					       bfd_elf_reloc_symbol_deleted_p,
+					       &cookie))
 	    {
-	      if (_bfd_elf_discard_section_sframe (i,
-						   bfd_elf_reloc_symbol_deleted_p,
-						   &cookie))
-		{
-		  if (i->size != i->rawsize)
-		    changed = 1;
-		}
+	      if (i->size != i->rawsize)
+		changed = 1;
 	    }
 	  fini_reloc_cookie_for_section (&cookie, i);
 	}
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+*}) }
-- 
2.52.0