Re: strip vs group signature symbols

[Alan Modra <amodra at bigpond dot net dot au>]

On Thu, Sep 14, 2006 at 12:38:00AM +0930, Alan Modra wrote:
> Makes strip --strip-unneeded on relocatable object files keep group
> signature symbols.

This one makes strip remove group sections if the group signature is
stripped.  That loses the group info, of course, but we have a
precedent for destroying info in that we allow strip to destroy
relocations.

	PR 3182
	* elf.c (_bfd_elf_copy_private_header_data): Fix group members
	that have had their SHT_GROUP section removed.
	* objcopy.c (group_signature): New function, split out from..
	(setup_section): ..here.
	(is_strip_section): Return true for SHT_GROUP sections that are
	going to lose their group signature symbol.

Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.352
diff -u -p -r1.352 elf.c
--- bfd/elf.c	10 Sep 2006 23:51:09 -0000	1.352
+++ bfd/elf.c	14 Sep 2006 09:06:32 -0000
@@ -6012,6 +6012,8 @@ _bfd_elf_copy_private_section_data (bfd 
 bfd_boolean
 _bfd_elf_copy_private_header_data (bfd *ibfd, bfd *obfd)
 {
+  asection *isec;
+
   if (bfd_get_flavour (ibfd) != bfd_target_elf_flavour
       || bfd_get_flavour (obfd) != bfd_target_elf_flavour)
     return TRUE;
@@ -6027,6 +6029,27 @@ _bfd_elf_copy_private_header_data (bfd *
 	return FALSE;
     }
 
+  /* _bfd_elf_copy_private_section_data copied over the SHF_GROUP flag
+     but this might be wrong if we deleted the group section.  */
+  for (isec = ibfd->sections; isec != NULL; isec = isec->next)
+    if (elf_section_type (isec) == SHT_GROUP
+	&& isec->output_section == NULL)
+      {
+	asection *first = elf_next_in_group (isec);
+	asection *s = first;
+	while (s != NULL)
+	  {
+	    if (s->output_section != NULL)
+	      {
+		elf_section_flags (s->output_section) &= ~SHF_GROUP;
+		elf_group_name (s->output_section) = NULL;
+	      }
+	    s = elf_next_in_group (s);
+	    if (s == first)
+	      break;
+	  }
+      }
+
   return TRUE;
 }
 
Index: binutils/objcopy.c
===================================================================
RCS file: /cvs/src/src/binutils/objcopy.c,v
retrieving revision 1.100
diff -u -p -r1.100 objcopy.c
--- binutils/objcopy.c	13 Sep 2006 15:08:38 -0000	1.100
+++ binutils/objcopy.c	14 Sep 2006 09:06:34 -0000
@@ -785,6 +785,30 @@ is_specified_symbol (const char *name, s
   return FALSE;
 }
 
+/* Return a pointer to the symbol used as a signature for GROUP.  */
+
+static asymbol *
+group_signature (asection *group)
+{
+  bfd *abfd = group->owner;
+  Elf_Internal_Shdr *ghdr;
+
+  if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
+    return NULL;
+
+  ghdr = &elf_section_data (group)->this_hdr;
+  if (ghdr->sh_link < elf_numsections (abfd))
+    {
+      const struct elf_backend_data *bed = get_elf_backend_data (abfd);
+      Elf_Internal_Shdr *symhdr = elf_elfsections (abfd) [ghdr->sh_link];
+
+      if (symhdr->sh_type == SHT_SYMTAB
+	  && ghdr->sh_info < symhdr->sh_size / bed->s->sizeof_sym)
+	return isympp[ghdr->sh_info];
+    }
+  return NULL;
+}
+
 /* See if a section is being removed.  */
 
 static bfd_boolean
@@ -815,12 +839,30 @@ is_strip_section (bfd *abfd ATTRIBUTE_UN
 	return FALSE;
     }
 
-  /* PR binutils/3166
-     Group sections look like debugging sections but they are not.
-     (They have a non-zero size but they are not ALLOCated).  */
-  if ((bfd_get_section_flags (abfd, sec) & SEC_GROUP) != 0
-      && strip_symbols == STRIP_NONDEBUG)
-    return TRUE;
+  if ((bfd_get_section_flags (abfd, sec) & SEC_GROUP) != 0)
+    {
+      asymbol *gsym;
+      const char *gname;
+
+      /* PR binutils/3166
+	 Group sections look like debugging sections but they are not.
+	 (They have a non-zero size but they are not ALLOCated).  */
+      if (strip_symbols == STRIP_NONDEBUG)
+	return TRUE;
+
+      /* PR binutils/3181
+	 If we are going to strip the group signature symbol, then
+	 strip the group section too.  */
+      gsym = group_signature (sec);
+      if (gsym != NULL)
+	gname = gsym->name;
+      else
+	gname = sec->name;
+      if ((strip_symbols == STRIP_ALL
+	   && !is_specified_symbol (gname, keep_specific_list))
+	  || is_specified_symbol (gname, strip_specific_list))
+	return TRUE;
+    }
 
   return FALSE;
 }
@@ -2214,21 +2256,12 @@ setup_section (bfd *ibfd, sec_ptr isecti
       err = _("private data");
       goto loser;
     }
-  else if ((isection->flags & SEC_GROUP) != 0
-	   && bfd_get_flavour (ibfd) == bfd_target_elf_flavour)
+  else if ((isection->flags & SEC_GROUP) != 0)
     {
-      Elf_Internal_Shdr *ghdr;
+      asymbol *gsym = group_signature (isection);
 
-      ghdr = &elf_section_data (isection)->this_hdr;
-      if (ghdr->sh_link < elf_numsections (ibfd))
-	{
-	  const struct elf_backend_data *bed = get_elf_backend_data (ibfd);
-	  Elf_Internal_Shdr *symhdr = elf_elfsections (ibfd) [ghdr->sh_link];
-
-	  if (symhdr->sh_type == SHT_SYMTAB
-	      && ghdr->sh_info < symhdr->sh_size / bed->s->sizeof_sym)
-	    isympp[ghdr->sh_info]->flags |= BSF_KEEP;
-	}
+      if (gsym != NULL)
+	gsym->flags |= BSF_KEEP;
     }
 
   /* All went well.  */

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre