ARC naughtiness causing assertion fail at elf-strtab.c:302

This patch fixes a number of issues in the ARC backend.

- The ARC size_dynamic_sections was trashing dynamic section contents,
  in particular the .gnu.version_d contents.  Those versions
  definitions are therefore lost so they do not drain from the strtab,
  resulting in assertion failures.
- The code attempting to set DT_TEXTREL was completely bogus.
- The ARC finish_dynamic_sections would segfault on trying to set
  sh_entsize for .rela.plt if that section had been discarded.
- arc_create_dynamic_sections wouldn't have ever created dynamics
  sections, which was just as well since the places it was called were
  way too late to create dynamic sections.  Its usefulness then
  devolved down to finding just one dynamic section.  All the others
  packaged into a struct were unused.
- .interp wasn't set for PIEs.

	* elf32-arc.c (struct dynamic_sections): Delete.
	(enum dyn_section_types): Delete.
	(dyn_section_names): Delete.
	(arc_create_dynamic_sections): Delete.
	(elf_arc_finish_dynamic_sections): Don't call the above.  Don't
	segfault on discarded .rela.plt section.
	(elf_arc_size_dynamic_sections): Formatting.  Don't call
	arc_create_dynamic_sections.  Don't allocate memory for sections
	handled by the generic linker.  Correct code finding relocs in
	read-only sections.  Set SEC_EXCLUDE on zero size .got,
	.got.plt, and .dynbss sections.  Do set .interp for pies.

2 files changed, 78 insertions, 135 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 7eda963..1118c19 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,17 @@
+2017-02-25  Alan Modra  <amodra@gmail.com>
+
+	* elf32-arc.c (struct dynamic_sections): Delete.
+	(enum dyn_section_types): Delete.
+	(dyn_section_names): Delete.
+	(arc_create_dynamic_sections): Delete.
+	(elf_arc_finish_dynamic_sections): Don't call the above.  Don't
+	segfault on discarded .rela.plt section.
+	(elf_arc_size_dynamic_sections): Formatting.  Don't call
+	arc_create_dynamic_sections.  Don't allocate memory for sections
+	handled by the generic linker.  Correct code finding relocs in
+	read-only sections.  Set SEC_EXCLUDE on zero size .got,
+	.got.plt, and .dynbss sections.  Do set .interp for pies.
+
 2017-02-24  Andrew Waterman  <andrew@sifive.com>
 
 	* elfnn-riscv.c (GP_NAME): New macro.
diff --git a/bfd/elf32-arc.c b/bfd/elf32-arc.c
index cc326bb..f31aeff 100644
--- a/bfd/elf32-arc.c
+++ b/bfd/elf32-arc.c
@@ -64,39 +64,6 @@ name_for_global_symbol (struct elf_link_hash_entry *h)
     bfd_elf32_swap_reloca_out (BFD, &_rel, _loc);			\
   }
 
-struct dynamic_sections
-{
-  bfd_boolean	  initialized;
-  asection *      sgot;
-  asection *      srelgot;
-  asection *      sgotplt;
-  asection *      srelgotplt;
-  asection *      sdyn;
-  asection *      splt;
-  asection *      srelplt;
-};
-
-enum dyn_section_types
-{
-  got = 0,
-  relgot,
-  gotplt,
-  dyn,
-  plt,
-  relplt,
-  DYN_SECTION_TYPES_END
-};
-
-const char * dyn_section_names[DYN_SECTION_TYPES_END] =
-{
-  ".got",
-  ".rela.got",
-  ".got.plt",
-  ".dynamic",
-  ".plt",
-  ".rela.plt"
-};
-
 
 /* The default symbols representing the init and fini dyn values.
    TODO: Check what is the relation of those strings with arclinux.em
@@ -1562,58 +1529,6 @@ elf_arc_relocate_section (bfd *		          output_bfd,
     (elf_hash_table_id ((struct elf_link_hash_table *) ((p)->hash)) \
   == ARC_ELF_DATA ? ((struct elf_arc_link_hash_table *) ((p)->hash)) : NULL)
 
-static struct dynamic_sections
-arc_create_dynamic_sections (bfd * abfd, struct bfd_link_info *info)
-{
-  struct elf_link_hash_table *htab;
-  bfd	 *dynobj;
-  struct dynamic_sections ds =
-    {
-      .initialized = FALSE,
-      .sgot = NULL,
-      .srelgot = NULL,
-      .sgotplt = NULL,
-      .srelgotplt = NULL,
-      .sdyn = NULL,
-      .splt = NULL,
-      .srelplt = NULL
-    };
-
-  htab = elf_hash_table (info);
-  BFD_ASSERT (htab);
-
-  /* Create dynamic sections for relocatable executables so that we
-     can copy relocations.  */
-  if (! htab->dynamic_sections_created && bfd_link_pic (info))
-    {
-      if (! _bfd_elf_link_create_dynamic_sections (abfd, info))
-	BFD_ASSERT (0);
-    }
-
-  dynobj = (elf_hash_table (info))->dynobj;
-
-  if (dynobj)
-    {
-      ds.sgot = htab->sgot;
-      ds.srelgot = htab->srelgot;
-
-      ds.sgotplt = bfd_get_section_by_name (dynobj, ".got.plt");
-      ds.srelgotplt = ds.srelplt;
-
-      ds.splt = bfd_get_section_by_name (dynobj, ".plt");
-      ds.srelplt = bfd_get_section_by_name (dynobj, ".rela.plt");
-    }
-
-  if (htab->dynamic_sections_created)
-    {
-      ds.sdyn = bfd_get_section_by_name (dynobj, ".dynamic");
-    }
-
-  ds.initialized = TRUE;
-
-  return ds;
-}
-
 static bfd_boolean
 elf_arc_check_relocs (bfd *			 abfd,
 		      struct bfd_link_info *     info,
@@ -2168,17 +2083,17 @@ static bfd_boolean
 elf_arc_finish_dynamic_sections (bfd * output_bfd,
 				 struct bfd_link_info *info)
 {
-  struct dynamic_sections ds = arc_create_dynamic_sections (output_bfd, info);
   struct elf_link_hash_table *htab = elf_hash_table (info);
   bfd *dynobj = (elf_hash_table (info))->dynobj;
+  asection *sdyn = bfd_get_linker_section (dynobj, ".dynamic");
 
-  if (ds.sdyn)
+  if (sdyn)
     {
       Elf32_External_Dyn *dyncon, *dynconend;
 
-      dyncon = (Elf32_External_Dyn *) ds.sdyn->contents;
+      dyncon = (Elf32_External_Dyn *) sdyn->contents;
       dynconend
-	= (Elf32_External_Dyn *) (ds.sdyn->contents + ds.sdyn->size);
+	= (Elf32_External_Dyn *) (sdyn->contents + sdyn->size);
       for (; dyncon < dynconend; dyncon++)
 	{
 	  Elf_Internal_Dyn internal_dyn;
@@ -2260,8 +2175,9 @@ elf_arc_finish_dynamic_sections (bfd * output_bfd,
 	}
 
       /* TODO: Validate this.  */
-      elf_section_data (htab->srelplt->output_section)->this_hdr.sh_entsize
-	= 0xc;
+      if (htab->srelplt->output_section != bfd_abs_section_ptr)
+	elf_section_data (htab->srelplt->output_section)
+	  ->this_hdr.sh_entsize = 12;
     }
 
   /* Fill in the first three entries in the global offset table.  */
@@ -2276,12 +2192,12 @@ elf_arc_finish_dynamic_sections (bfd * output_bfd,
 	{
 	  asection *sec = h->root.u.def.section;
 
-	  if (ds.sdyn == NULL)
+	  if (sdyn == NULL)
 	    bfd_put_32 (output_bfd, (bfd_vma) 0,
 			sec->contents);
 	  else
 	    bfd_put_32 (output_bfd,
-			ds.sdyn->output_section->vma + ds.sdyn->output_offset,
+			sdyn->output_section->vma + sdyn->output_offset,
 			sec->contents);
 	  bfd_put_32 (output_bfd, (bfd_vma) 0, sec->contents + 4);
 	  bfd_put_32 (output_bfd, (bfd_vma) 0, sec->contents + 8);
@@ -2300,26 +2216,25 @@ elf_arc_finish_dynamic_sections (bfd * output_bfd,
 
 /* Set the sizes of the dynamic sections.  */
 static bfd_boolean
-elf_arc_size_dynamic_sections (bfd * output_bfd,
+elf_arc_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 			       struct bfd_link_info *info)
 {
-  bfd *	   dynobj;
-  asection *      s;
-  bfd_boolean	  relocs_exist = FALSE;
-  bfd_boolean	  reltext_exist = FALSE;
-  struct dynamic_sections ds = arc_create_dynamic_sections (output_bfd, info);
+  bfd *dynobj;
+  asection *s;
+  bfd_boolean relocs_exist = FALSE;
+  bfd_boolean reltext_exist = FALSE;
   struct elf_link_hash_table *htab = elf_hash_table (info);
 
-  dynobj = (elf_hash_table (info))->dynobj;
+  dynobj = htab->dynobj;
   BFD_ASSERT (dynobj != NULL);
 
-  if ((elf_hash_table (info))->dynamic_sections_created)
+  if (htab->dynamic_sections_created)
     {
       struct elf_link_hash_entry *h;
 
       /* Set the contents of the .interp section to the
 	 interpreter.  */
-      if (!bfd_link_pic (info) && !info->nointerp)
+      if (bfd_link_executable (info) && !info->nointerp)
 	{
 	  s = bfd_get_section_by_name (dynobj, ".interp");
 	  BFD_ASSERT (s != NULL);
@@ -2347,54 +2262,70 @@ elf_arc_size_dynamic_sections (bfd * output_bfd,
 	htab->srelgot->size = 0;
     }
 
-  if (htab->splt != NULL && htab->splt->size == 0)
-    htab->splt->flags |= SEC_EXCLUDE;
   for (s = dynobj->sections; s != NULL; s = s->next)
     {
       if ((s->flags & SEC_LINKER_CREATED) == 0)
 	continue;
 
-      if (strncmp (s->name, ".rela", 5) == 0)
+      if (s == htab->splt
+	  || s == htab->sgot
+	  || s == htab->sgotplt
+	  || s == htab->sdynbss)
 	{
-	  if (s->size == 0)
-	    {
-	      s->flags |= SEC_EXCLUDE;
-	    }
-	  else
+	  /* Strip this section if we don't need it.  */
+	}
+      else if (strncmp (s->name, ".rela", 5) == 0)
+	{
+	  if (s->size != 0 && s != htab->srelplt)
 	    {
-	      if (strcmp (s->name, ".rela.plt") != 0)
+	      if (!reltext_exist)
 		{
-		  const char *outname =
-		    bfd_get_section_name (output_bfd,
-					  htab->srelplt->output_section);
-
-		  asection *target = bfd_get_section_by_name (output_bfd,
-							      outname + 4);
-
-		  relocs_exist = TRUE;
-		  if (target != NULL && target->size != 0
-		      && (target->flags & SEC_READONLY) != 0
-		      && (target->flags & SEC_ALLOC) != 0)
-		    reltext_exist = TRUE;
+		  const char *name = s->name + 5;
+		  bfd *ibfd;
+		  for (ibfd = info->input_bfds; ibfd; ibfd = ibfd->link.next)
+		    if (bfd_get_flavour (ibfd) == bfd_target_elf_flavour)
+		      {
+			asection *target = bfd_get_section_by_name (ibfd, name);
+			if (target != NULL
+			    && elf_section_data (target)->sreloc == s
+			    && ((target->output_section->flags
+				 & (SEC_READONLY | SEC_ALLOC))
+				== (SEC_READONLY | SEC_ALLOC)))
+			  {
+			    reltext_exist = TRUE;
+			    break;
+			  }
+		      }
 		}
+	      relocs_exist = TRUE;
 	    }
 
 	  /* We use the reloc_count field as a counter if we need to
 	     copy relocs into the output file.  */
 	  s->reloc_count = 0;
 	}
+      else
+	{
+	  /* It's not one of our sections, so don't allocate space.  */
+	  continue;
+	}
 
-      if (strcmp (s->name, ".dynamic") == 0)
-	continue;
+      if (s->size == 0)
+	{
+	  s->flags |= SEC_EXCLUDE;
+	  continue;
+	}
 
-      if (s->size != 0)
-	s->contents = (bfd_byte *) bfd_zalloc (dynobj, s->size);
+      if ((s->flags & SEC_HAS_CONTENTS) == 0)
+	continue;
 
-      if (s->contents == NULL && s->size != 0)
+      /* Allocate memory for the section contents.  */
+      s->contents = bfd_zalloc (dynobj, s->size);
+      if (s->contents == NULL)
 	return FALSE;
     }
 
-  if (ds.sdyn)
+  if (htab->dynamic_sections_created)
     {
       /* TODO: Check if this is needed.  */
       if (!bfd_link_pic (info))
@@ -2405,19 +2336,17 @@ elf_arc_size_dynamic_sections (bfd * output_bfd,
 	if (!_bfd_elf_add_dynamic_entry (info, DT_PLTGOT, 0)
 	    || !_bfd_elf_add_dynamic_entry (info, DT_PLTRELSZ, 0)
 	    || !_bfd_elf_add_dynamic_entry (info, DT_PLTREL, DT_RELA)
-	    || !_bfd_elf_add_dynamic_entry (info, DT_JMPREL, 0)
-	   )
+	    || !_bfd_elf_add_dynamic_entry (info, DT_JMPREL, 0))
 	  return FALSE;
 
-      if (relocs_exist == TRUE)
+      if (relocs_exist)
 	if (!_bfd_elf_add_dynamic_entry (info, DT_RELA, 0)
 	    || !_bfd_elf_add_dynamic_entry (info, DT_RELASZ, 0)
 	    || !_bfd_elf_add_dynamic_entry (info, DT_RELAENT,
-					    sizeof (Elf32_External_Rela))
-	   )
+					    sizeof (Elf32_External_Rela)))
 	  return FALSE;
 
-      if (reltext_exist == TRUE)
+      if (reltext_exist)
 	if (!_bfd_elf_add_dynamic_entry (info, DT_TEXTREL, 0))
 	  return FALSE;
     }