Nios2 dynobj handling fixes

A number of places in elf32-nios.c created dynamic sections but didn't
set the hash table dynobj.  That meant we could have duplicate dynamic
sections connected to a number of bfds, so size_dynamic_sections
didn't properly discard or allocate contents.

Also, the entire set of dynamic sections was created in check_relocs
on seeing GOT relocs, when only .got related sections are needed,
probably done to hide segfaults later in finish_dynamic_sections.

The patch fixes these issues and makes the assembler emit errors when
nios2 lacks the necessary pc-relative relocs for subtraction
expressions, rather than silently generating bad code.
eg. ld-elf/merge.  I've also tidied uses of elf32_nios2_hash_table and
elf_hash_table.

bfd/
	PR 20995
	* elf32-nios2.c (nios2_elf32_relocate_section): Use htab
	rather than elf32_nios2_hash_table or elf_hash_table.
	(create_got_section): Likewise.
	(nios2_elf32_finish_dynamic_symbol): Likewise.
	(nios2_elf32_adjust_dynamic_symbol): Likewise.
	(nios2_elf32_size_dynamic_sections): Likewise.
	(nios2_elf32_check_relocs): Delete dynobj, sgot, and srelgot
	vars.  Use htab equivalents directly instead.  Don't create
	all dynamic sections on needing just the GOT.  Use a goto
	rather than a fall-through with reloc test.  Ensure
	htab->dynobj is set when making dynamic sreloc section.
	(nios2_elf32_finish_dynamic_sections): Delete dynobj, use htab
	equivalent directly instead.  Don't segfault on looking for
	.dynamic when dynamic sections have not been created.  Don't
	segfault on .got.plt being discarded.
	(nios2_elf32_size_dynamic_sections): Delete plt and got vars.
	Don't set "relocs" on .rela.plt.  Do handle .sbss.  Delete
	fixme and another not so relevant comment.
	(nios2_elf_add_symbol_hook): Delete dynobj var.  If not
	already set, set hash table dynobj on creating .sbss.
gas/
	* config/tc-nios2.h (TC_FORCE_RELOCATION_SUB_LOCAL): Define.
ld/
	* testsuite/ld-elf/merge.d: xfail for nios.

1 files changed, 53 insertions, 101 deletions

diff --git a/bfd/elf32-nios2.c b/bfd/elf32-nios2.c
index d07ef67..a2045bf 100644
--- a/bfd/elf32-nios2.c
+++ b/bfd/elf32-nios2.c
@@ -3713,10 +3713,10 @@ nios2_elf32_relocate_section (bfd *output_bfd,
   splt = htab->root.splt;
   local_got_offsets = elf_local_got_offsets (input_bfd);
 
-  if (elf32_nios2_hash_table (info)->h_gp_got == NULL)
+  if (htab->h_gp_got == NULL)
     got_base = 0;
   else
-    got_base = elf32_nios2_hash_table (info)->h_gp_got->root.u.def.value;
+    got_base = htab->h_gp_got->root.u.def.value;
 
   for (rel = relocs; rel < relend; rel++)
     {
@@ -3998,7 +3998,7 @@ nios2_elf32_relocate_section (bfd *output_bfd,
 
 		  off = h->got.offset;
 		  BFD_ASSERT (off != (bfd_vma) -1);
-		  dyn = elf_hash_table (info)->dynamic_sections_created;
+		  dyn = htab->root.dynamic_sections_created;
 		  if (! WILL_CALL_FINISH_DYNAMIC_SYMBOL (dyn,
 							 bfd_link_pic (info),
 							 h)
@@ -4580,7 +4580,7 @@ create_got_section (bfd *dynobj, struct bfd_link_info *info)
      points to the base of the GOT while _gp_got may include a bias.  */
   h = _bfd_elf_define_linkage_sym (dynobj, info, htab->root.sgotplt,
 				   "_gp_got");
-  elf32_nios2_hash_table (info)->h_gp_got = h;
+  htab->h_gp_got = h;
   if (h == NULL)
     return FALSE;
 
@@ -4694,21 +4694,17 @@ static bfd_boolean
 nios2_elf32_check_relocs (bfd *abfd, struct bfd_link_info *info,
 			  asection *sec, const Elf_Internal_Rela *relocs)
 {
-  bfd *dynobj;
   Elf_Internal_Shdr *symtab_hdr;
   struct elf_link_hash_entry **sym_hashes, **sym_hashes_end;
   const Elf_Internal_Rela *rel;
   const Elf_Internal_Rela *rel_end;
   struct elf32_nios2_link_hash_table *htab;
-  asection *sgot;
-  asection *srelgot;
   asection *sreloc = NULL;
   bfd_signed_vma *local_got_refcounts;
 
   if (bfd_link_relocatable (info))
     return TRUE;
 
-  dynobj = elf_hash_table (info)->dynobj;
   symtab_hdr = &elf_tdata (abfd)->symtab_hdr;
   sym_hashes = elf_sym_hashes (abfd);
   sym_hashes_end = (sym_hashes
@@ -4718,8 +4714,6 @@ nios2_elf32_check_relocs (bfd *abfd, struct bfd_link_info *info,
   local_got_refcounts = elf_local_got_refcounts (abfd);
 
   htab = elf32_nios2_hash_table (info);
-  sgot = htab->root.sgot;
-  srelgot = htab->root.srelgot;
 
   rel_end = relocs + sec->reloc_count;
   for (rel = relocs; rel < rel_end; rel++)
@@ -4778,26 +4772,6 @@ nios2_elf32_check_relocs (bfd *abfd, struct bfd_link_info *info,
 		break;
 	      }
 
-	    if (dynobj == NULL)
-	      {
-		/* Create the .got section.  */
-		elf_hash_table (info)->dynobj = dynobj = abfd;
-		nios2_elf32_create_dynamic_sections (dynobj, info);
-	      }
-
-	    if (sgot == NULL)
-	      {
-		sgot = htab->root.sgot;
-		BFD_ASSERT (sgot != NULL);
-	      }
-
-	    if (srelgot == NULL
-		&& (h != NULL || bfd_link_pic (info)))
-	      {
-		srelgot = htab->root.srelgot;
-		BFD_ASSERT (srelgot != NULL);
-	      }
-
 	    if (h != NULL)
 	      {
 		struct elf32_nios2_link_hash_entry *eh
@@ -4856,11 +4830,7 @@ nios2_elf32_check_relocs (bfd *abfd, struct bfd_link_info *info,
 		  elf32_nios2_local_got_tls_type (abfd) [r_symndx] = tls_type;
 	      }
 	  }
-	  /* Fall through */
-	case R_NIOS2_TLS_LDM16:
-	  if (r_type == R_NIOS2_TLS_LDM16)
-	    htab->tls_ldm_got.refcount++;
-
+	make_got:
 	  if (htab->root.sgot == NULL)
 	    {
 	      if (htab->root.dynobj == NULL)
@@ -4870,6 +4840,10 @@ nios2_elf32_check_relocs (bfd *abfd, struct bfd_link_info *info,
 	    }
 	  break;
 
+	case R_NIOS2_TLS_LDM16:
+	  htab->tls_ldm_got.refcount++;
+	  goto make_got;
+
 	  /* This relocation describes the C++ object vtable hierarchy.
 	     Reconstruct it for later use during GC.  */
 	case R_NIOS2_GNU_VTINHERIT:
@@ -4925,8 +4899,11 @@ nios2_elf32_check_relocs (bfd *abfd, struct bfd_link_info *info,
 		 section in dynobj and make room for this reloc.  */
 	      if (sreloc == NULL)
 		{
+		  if (htab->root.dynobj == NULL)
+		    htab->root.dynobj = abfd;
+
 		  sreloc = _bfd_elf_make_dynamic_reloc_section
-		    (sec, dynobj, 2, abfd, TRUE);
+		    (sec, htab->root.dynobj, 2, abfd, TRUE);
 		  if (sreloc == NULL)
 		    return FALSE;
 		}
@@ -5291,8 +5268,8 @@ nios2_elf32_finish_dynamic_symbol (bfd *output_bfd,
 
   /* Mark _DYNAMIC, _GLOBAL_OFFSET_TABLE_, and _gp_got as absolute.  */
   if (strcmp (h->root.root.string, "_DYNAMIC") == 0
-      || h == elf_hash_table (info)->hgot
-      || h == elf32_nios2_hash_table (info)->h_gp_got)
+      || h == htab->root.hgot
+      || h == htab->h_gp_got)
     sym->st_shndx = SHN_ABS;
 
   return TRUE;
@@ -5303,24 +5280,22 @@ static bfd_boolean
 nios2_elf32_finish_dynamic_sections (bfd *output_bfd,
 				     struct bfd_link_info *info)
 {
-  bfd *dynobj;
   asection *sgotplt;
   asection *sdyn;
   struct elf32_nios2_link_hash_table *htab;
 
   htab = elf32_nios2_hash_table (info);
-  dynobj = elf_hash_table (info)->dynobj;
   sgotplt = htab->root.sgotplt;
-  BFD_ASSERT (sgotplt != NULL);
-  sdyn = bfd_get_linker_section (dynobj, ".dynamic");
+  sdyn = NULL;
 
-  if (elf_hash_table (info)->dynamic_sections_created)
+  if (htab->root.dynamic_sections_created)
     {
       asection *splt;
       Elf32_External_Dyn *dyncon, *dynconend;
 
       splt = htab->root.splt;
-      BFD_ASSERT (splt != NULL && sdyn != NULL);
+      sdyn = bfd_get_linker_section (htab->root.dynobj, ".dynamic");
+      BFD_ASSERT (splt != NULL && sdyn != NULL && sgotplt != NULL);
 
       dyncon = (Elf32_External_Dyn *) sdyn->contents;
       dynconend = (Elf32_External_Dyn *) (sdyn->contents + sdyn->size);
@@ -5329,7 +5304,7 @@ nios2_elf32_finish_dynamic_sections (bfd *output_bfd,
 	  Elf_Internal_Dyn dyn;
 	  asection *s;
 
-	  bfd_elf32_swap_dyn_in (dynobj, dyncon, &dyn);
+	  bfd_elf32_swap_dyn_in (htab->root.dynobj, dyncon, &dyn);
 
 	  switch (dyn.d_tag)
 	    {
@@ -5413,8 +5388,9 @@ nios2_elf32_finish_dynamic_sections (bfd *output_bfd,
 	    }
 	}
     }
+
   /* Fill in the first three entries in the global offset table.  */
-  if (sgotplt->size > 0)
+  if (sgotplt != NULL && sgotplt->size > 0)
     {
       if (sdyn == NULL)
 	bfd_put_32 (output_bfd, (bfd_vma) 0, sgotplt->contents);
@@ -5424,9 +5400,10 @@ nios2_elf32_finish_dynamic_sections (bfd *output_bfd,
 		    sgotplt->contents);
       bfd_put_32 (output_bfd, (bfd_vma) 0, sgotplt->contents + 4);
       bfd_put_32 (output_bfd, (bfd_vma) 0, sgotplt->contents + 8);
-    }
 
-  elf_section_data (sgotplt->output_section)->this_hdr.sh_entsize = 4;
+      if (sgotplt->output_section != bfd_abs_section_ptr)
+	elf_section_data (sgotplt->output_section)->this_hdr.sh_entsize = 4;
+    }
 
   return TRUE;
 }
@@ -5447,7 +5424,7 @@ nios2_elf32_adjust_dynamic_symbol (struct bfd_link_info *info,
   unsigned align2;
 
   htab = elf32_nios2_hash_table (info);
-  dynobj = elf_hash_table (info)->dynobj;
+  dynobj = htab->root.dynobj;
 
   /* Make sure we know what is going on here.  */
   BFD_ASSERT (dynobj != NULL
@@ -5834,18 +5811,16 @@ nios2_elf32_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 {
   bfd *dynobj;
   asection *s;
-  bfd_boolean plt;
-  bfd_boolean got;
   bfd_boolean relocs;
   bfd *ibfd;
   struct elf32_nios2_link_hash_table *htab;
 
   htab = elf32_nios2_hash_table (info);
-  dynobj = elf_hash_table (info)->dynobj;
+  dynobj = htab->root.dynobj;
   BFD_ASSERT (dynobj != NULL);
 
   htab->res_n_size = 0;
-  if (elf_hash_table (info)->dynamic_sections_created)
+  if (htab->root.dynamic_sections_created)
     {
       /* Set the contents of the .interp section to the interpreter.  */
       if (bfd_link_executable (info) && !info->nointerp)
@@ -5953,21 +5928,19 @@ nios2_elf32_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
      sym dynamic relocs.  */
   elf_link_hash_traverse (& htab->root, allocate_dynrelocs, info);
 
-  if (elf_hash_table (info)->dynamic_sections_created)
+  if (htab->root.dynamic_sections_created)
     {
       /* If the .got section is more than 0x8000 bytes, we add
 	 0x8000 to the value of _gp_got, so that 16-bit relocations
 	 have a greater chance of working. */
       if (htab->root.sgot->size >= 0x8000
-	  && elf32_nios2_hash_table (info)->h_gp_got->root.u.def.value == 0)
-	elf32_nios2_hash_table (info)->h_gp_got->root.u.def.value = 0x8000;
+	  && htab->h_gp_got->root.u.def.value == 0)
+	htab->h_gp_got->root.u.def.value = 0x8000;
     }
 
   /* The check_relocs and adjust_dynamic_symbol entry points have
      determined the sizes of the various dynamic sections.  Allocate
      memory for them.  */
-  plt = FALSE;
-  got = FALSE;
   relocs = FALSE;
   for (s = dynobj->sections; s != NULL; s = s->next)
     {
@@ -5980,51 +5953,37 @@ nios2_elf32_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 	 of the dynobj section names depend upon the input files.  */
       name = bfd_get_section_name (dynobj, s);
 
-      if (s == htab->root.splt)
-	{
-	  /* Remember whether there is a PLT.  */
-	  plt = s->size != 0;
-
-	  /* Correct for the number of res_N branches.  */
-	  if (plt && !bfd_link_pic (info))
-	    {
-	      htab->res_n_size = (s->size-28) / 3;
-	      s->size += htab->res_n_size;
-	    }
-	}
-      else if (CONST_STRNEQ (name, ".rela"))
+      if (CONST_STRNEQ (name, ".rela"))
 	{
 	  if (s->size != 0)
 	    {
-	      relocs = TRUE;
+	      if (s != htab->root.srelplt)
+		relocs = 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 if (s == htab->root.sgot
-	       || s == htab->root.sgotplt)
+      else if (s == htab->root.splt)
 	{
-	  if (s->size != 0)
-	    got = TRUE;
+	  /* Correct for the number of res_N branches.  */
+	  if (s->size != 0 && !bfd_link_pic (info))
+	    {
+	      htab->res_n_size = (s->size - 28) / 3;
+	      s->size += htab->res_n_size;
+	    }
 	}
-      else if (s != htab->root.sdynbss
+      else if (s != htab->sbss
+	       && s != htab->root.sgot
+	       && s != htab->root.sgotplt
+	       && s != htab->root.sdynbss
 	       && s != htab->root.sdynrelro)
 	/* It's not one of our sections, so don't allocate space.  */
 	continue;
 
       if (s->size == 0)
 	{
-	  /* If we don't need this section, strip it from the
-	     output file.  This is mostly to handle .rela.bss and
-	     .rela.plt.  We must create both sections in
-	     create_dynamic_sections, because they must be created
-	     before the linker maps input sections to output
-	     sections.  The linker does that before
-	     adjust_dynamic_symbol is called, and it is that
-	     function which decides whether anything needs to go
-	     into these sections.  */
 	  s->flags |= SEC_EXCLUDE;
 	  continue;
 	}
@@ -6033,11 +5992,6 @@ nios2_elf32_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 	continue;
 
       /* Allocate memory for the section contents.  */
-      /* FIXME: This should be a call to bfd_alloc not bfd_zalloc.
-	 Unused entries should be reclaimed before the section's contents
-	 are written out, but at the moment this does not happen.  Thus in
-	 order to prevent writing out garbage, we initialize the section's
-	 contents to zero.  */
       s->contents = (bfd_byte *) bfd_zalloc (dynobj, s->size);
       if (s->contents == NULL)
 	return FALSE;
@@ -6048,7 +6002,7 @@ nios2_elf32_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
   if (htab->res_n_size)
     elf_link_hash_traverse (& htab->root, adjust_dynrelocs, info);
 
-  if (elf_hash_table (info)->dynamic_sections_created)
+  if (htab->root.dynamic_sections_created)
     {
       /* Add some entries to the .dynamic section.  We fill in the
 	 values later, in elf_nios2_finish_dynamic_sections, but we
@@ -6061,10 +6015,11 @@ nios2_elf32_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
       if (!bfd_link_pic (info) && !add_dynamic_entry (DT_DEBUG, 0))
 	return FALSE;
 
-      if (got && !add_dynamic_entry (DT_PLTGOT, 0))
+      if (htab->root.sgotplt->size != 0
+	  && !add_dynamic_entry (DT_PLTGOT, 0))
 	return FALSE;
 
-      if (plt
+      if (htab->root.splt->size != 0
 	  && (!add_dynamic_entry (DT_PLTRELSZ, 0)
 	      || !add_dynamic_entry (DT_PLTREL, DT_RELA)
 	      || !add_dynamic_entry (DT_JMPREL, 0)))
@@ -6171,8 +6126,6 @@ nios2_elf_add_symbol_hook (bfd *abfd,
 			   asection **secp,
 			   bfd_vma *valp)
 {
-  bfd *dynobj;
-
   if (sym->st_shndx == SHN_COMMON
       && !bfd_link_relocatable (info)
       && sym->st_size <= elf_gp_size (abfd)
@@ -6187,12 +6140,11 @@ nios2_elf_add_symbol_hook (bfd *abfd,
 	{
 	  flagword flags = SEC_IS_COMMON | SEC_LINKER_CREATED;
 
-	  dynobj = elf_hash_table (info)->dynobj;
-	  if (!dynobj)
-	    dynobj = abfd;
+	  if (htab->root.dynobj == NULL)
+	    htab->root.dynobj = abfd;
 
-	  htab->sbss = bfd_make_section_anyway_with_flags (dynobj, ".sbss",
-							   flags);
+	  htab->sbss = bfd_make_section_anyway_with_flags (htab->root.dynobj,
+							   ".sbss", flags);
 	  if (htab->sbss == NULL)
 	    return FALSE;
 	}