Fix GOT relocation overflow on SPARC.

There are 2 failures left in the linker testsuite on SPARC64/Linux and
they are caused by 2 different issues leading to the same end effect:
the overflow of the relocation section for the GOT, i.e. the linker
generates too many dynamic relocations for the GOT wrt the size of the
relocation section, leading to memory corruption and missing relocations
in the final binary.

The first issue was introduced by:
  https://sourceware.org/ml/binutils/2017-06/msg00368.html
which makes the linker generate more R_SPARC_RELATIVE relocations for
the GOT without adjusting the size of the relocation section.  This is
fixed by (1) preventively adjusting this size in allocate_dynrelocs and
(2) generating R_SPARC_NONE if needed when R_SPARC_GOTDATA_OP is relaxed.

The second issue is that we generate a GOT relocation for an undefined
weak symbol with non-default visibility in a PIC binary without accounting
for that  in the size of the relocation section.  Since the address of the
symbol should resolve to 0 at run time, it is fixed by not generating the
relocation at all, i.e. leaving the GOT entry zeroed.

bfd/
	* elfxx-sparc.c (UNDEFINED_WEAK_RESOLVED_TO_ZERO): Reorder conditions.
	(sparc_elf_append_rela): Assert that there is enough room in section.
	(_bfd_sparc_elf_copy_indirect_symbol): Fix formatting.
	(_bfd_sparc_elf_adjust_dynamic_symbol): Minor tweak.
	(allocate_dynrelocs): Remove outdated comments and reorder conditions.
	For a symbol subject to a GOT relocation, reserve a slot in the
	relocation section if the symbol isn't dynamic and we are in PIC mode.
	(_bfd_sparc_elf_relocate_section) <R_SPARC_GOTDATA_OP>: If relocation
	is relaxed and a slot was reserved, generate a R_SPARC_NONE relocation.
	<R_SPARC_GOTDATA_OP_HIX22>: Adjust comments.
	<R_SPARC_PC10>: Reorder conditions.  Remove always-false assertion.
	(_bfd_sparc_elf_finish_dynamic_symbol): Rename local_undefweak into
	resolved_to_zero.  Do not generate a dynamic GOT relocation for an
	undefined weak symbol with non-default visibility.  Remove superfluous
	'else' and fix formatting.

2 files changed, 88 insertions, 52 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 812a024..20543d7 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,21 @@
+2018-02-08  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* elfxx-sparc.c (UNDEFINED_WEAK_RESOLVED_TO_ZERO): Reorder conditions.
+	(sparc_elf_append_rela): Assert that there is enough room in section.
+	(_bfd_sparc_elf_copy_indirect_symbol): Fix formatting.
+	(_bfd_sparc_elf_adjust_dynamic_symbol): Minor tweak.
+	(allocate_dynrelocs): Remove outdated comments and reorder conditions.
+	For a symbol subject to a GOT relocation, reserve a slot in the
+	relocation section if the symbol isn't dynamic and we are in PIC mode.
+	(_bfd_sparc_elf_relocate_section) <R_SPARC_GOTDATA_OP>: If relocation
+	is relaxed and a slot was reserved, generate a R_SPARC_NONE relocation.
+	<R_SPARC_GOTDATA_OP_HIX22>: Adjust comments.
+	<R_SPARC_PC10>: Reorder conditions.  Remove always-false assertion.
+	(_bfd_sparc_elf_finish_dynamic_symbol): Rename local_undefweak into
+	resolved_to_zero.  Do not generate a dynamic GOT relocation for an
+	undefined weak symbol with non-default visibility.  Remove superfluous
+	'else' and fix formatting.
+
 2018-02-09  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* elf32-i386.c (elf_i386_get_synthetic_symtab): Also handle
diff --git a/bfd/elfxx-sparc.c b/bfd/elfxx-sparc.c
index afd62d4..83ead75 100644
--- a/bfd/elfxx-sparc.c
+++ b/bfd/elfxx-sparc.c
@@ -673,9 +673,9 @@ _bfd_sparc_elf_info_to_howto (bfd *abfd ATTRIBUTE_UNUSED, arelent *cache_ptr,
   ((EH)->elf.root.type == bfd_link_hash_undefweak		\
    && bfd_link_executable (INFO)				\
    && (_bfd_sparc_elf_hash_table (INFO)->interp == NULL		\
-       || !(EH)->has_got_reloc					\
+       || !(INFO)->dynamic_undefined_weak			\
        || (EH)->has_non_got_reloc				\
-       || !(INFO)->dynamic_undefined_weak))
+       || !(EH)->has_got_reloc))
 
 /* SPARC ELF linker hash entry.  */
 
@@ -750,6 +750,7 @@ sparc_elf_append_rela (bfd *abfd, asection *s, Elf_Internal_Rela *rel)
   bfd_byte *loc;
 
   bed = get_elf_backend_data (abfd);
+  BFD_ASSERT (s->reloc_count * bed->s->sizeof_rela < s->size);
   loc = s->contents + (s->reloc_count++ * bed->s->sizeof_rela);
   bed->s->swap_reloca_out (abfd, rel, loc);
 }
@@ -1310,8 +1311,7 @@ _bfd_sparc_elf_copy_indirect_symbol (struct bfd_link_info *info,
       eind->dyn_relocs = NULL;
     }
 
-  if (ind->root.type == bfd_link_hash_indirect
-      && dir->got.refcount <= 0)
+  if (ind->root.type == bfd_link_hash_indirect && dir->got.refcount <= 0)
     {
       edir->tls_type = eind->tls_type;
       eind->tls_type = GOT_UNKNOWN;
@@ -1968,8 +1968,8 @@ _bfd_sparc_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
       if (h->plt.refcount <= 0
 	  || (h->type != STT_GNU_IFUNC
 	      && (SYMBOL_CALLS_LOCAL (info, h)
-		  || (ELF_ST_VISIBILITY (h->other) != STV_DEFAULT
-		      && h->root.type == bfd_link_hash_undefweak))))
+		  || (h->root.type == bfd_link_hash_undefweak
+		      && ELF_ST_VISIBILITY (h->other) != STV_DEFAULT))))
 	{
 	  /* This case can occur if we saw a WPLT30 reloc in an input
 	     file, but the symbol was never referred to by a dynamic
@@ -2088,12 +2088,11 @@ allocate_dynrelocs (struct elf_link_hash_entry *h, void * inf)
 	  && h->def_regular
 	  && h->ref_regular))
     {
-      /* Make sure this symbol is output as a dynamic symbol.
-	 Undefined weak syms won't yet be marked as dynamic.  */
-      if (h->dynindx == -1
-	  && !h->forced_local
+      /* Undefined weak syms won't yet be marked as dynamic.  */
+      if (h->root.type == bfd_link_hash_undefweak
 	  && !resolved_to_zero
-	  && h->root.type == bfd_link_hash_undefweak)
+	  && h->dynindx == -1
+	  && !h->forced_local)
 	{
 	  if (! bfd_elf_link_record_dynamic_symbol (info, h))
 	    return FALSE;
@@ -2201,12 +2200,11 @@ allocate_dynrelocs (struct elf_link_hash_entry *h, void * inf)
       bfd_boolean dyn;
       int tls_type = _bfd_sparc_elf_hash_entry(h)->tls_type;
 
-      /* Make sure this symbol is output as a dynamic symbol.
-	 Undefined weak syms won't yet be marked as dynamic.  */
-      if (h->dynindx == -1
-	  && !h->forced_local
+      /* Undefined weak syms won't yet be marked as dynamic.  */
+      if (h->root.type == bfd_link_hash_undefweak
 	  && !resolved_to_zero
-	  && h->root.type == bfd_link_hash_undefweak)
+	  && h->dynindx == -1
+	  && !h->forced_local)
 	{
 	  if (! bfd_elf_link_record_dynamic_symbol (info, h))
 	    return FALSE;
@@ -2220,21 +2218,25 @@ allocate_dynrelocs (struct elf_link_hash_entry *h, void * inf)
 	s->size += SPARC_ELF_WORD_BYTES (htab);
       dyn = htab->elf.dynamic_sections_created;
       /* R_SPARC_TLS_IE_{HI22,LO10} needs one dynamic relocation,
-	 R_SPARC_TLS_GD_{HI22,LO10} needs one if local symbol and two if
-	 global.  No dynamic relocations are needed against resolved
-	 undefined weak symbols in an executable.  */
+	 R_SPARC_TLS_GD_{HI22,LO10} needs one if local and two if global.  */
       if ((tls_type == GOT_TLS_GD && h->dynindx == -1)
 	  || tls_type == GOT_TLS_IE
 	  || h->type == STT_GNU_IFUNC)
 	htab->elf.srelgot->size += SPARC_ELF_RELA_BYTES (htab);
       else if (tls_type == GOT_TLS_GD)
 	htab->elf.srelgot->size += 2 * SPARC_ELF_RELA_BYTES (htab);
-      else if (((ELF_ST_VISIBILITY (h->other) == STV_DEFAULT
-		 && !resolved_to_zero)
-		|| h->root.type != bfd_link_hash_undefweak)
-	       && WILL_CALL_FINISH_DYNAMIC_SYMBOL (dyn,
-						   bfd_link_pic (info),
-						   h))
+      else if ((WILL_CALL_FINISH_DYNAMIC_SYMBOL (dyn, bfd_link_pic (info), h)
+		/* Even if the symbol isn't dynamic, we may generate a
+		   reloc for the dynamic linker in PIC mode.  */
+		|| (h->dynindx == -1
+		    && !h->forced_local
+		    && h->root.type != bfd_link_hash_undefweak
+		    && bfd_link_pic (info)))
+	       /* No dynamic relocations are needed against resolved
+		  undefined weak symbols in an executable.  */
+	       && !(h->root.type == bfd_link_hash_undefweak
+		    && (ELF_ST_VISIBILITY (h->other) != STV_DEFAULT
+			|| resolved_to_zero)))
 	htab->elf.srelgot->size += SPARC_ELF_RELA_BYTES (htab);
     }
   else
@@ -2344,12 +2346,11 @@ allocate_dynrelocs (struct elf_link_hash_entry *h, void * inf)
 		  && (h->root.type == bfd_link_hash_undefweak
 		      || h->root.type == bfd_link_hash_undefined))))
 	{
-	  /* Make sure this symbol is output as a dynamic symbol.
-	     Undefined weak syms won't yet be marked as dynamic.  */
-	  if (h->dynindx == -1
-	      && !h->forced_local
+	  /* Undefined weak syms won't yet be marked as dynamic.  */
+	  if (h->root.type == bfd_link_hash_undefweak
 	      && !resolved_to_zero
-	      && h->root.type == bfd_link_hash_undefweak)
+	      && h->dynindx == -1
+	      && !h->forced_local)
 	    {
 	      if (! bfd_elf_link_record_dynamic_symbol (info, h))
 		return FALSE;
@@ -3118,6 +3119,26 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
 	      /* {ld,ldx} [%rs1 + %rs2], %rd --> add %rs1, %rs2, %rd */
 	      relocation = 0x80000000 | (insn & 0x3e07c01f);
 	      bfd_put_32 (output_bfd, relocation, contents + rel->r_offset);
+
+	      /* If the symbol is global but not dynamic, an .rela.* slot has
+		 been allocated for it in the GOT so output R_SPARC_NONE here.
+		 See also the handling of other GOT relocations just below.  */
+	      if (h != NULL
+		  && h->dynindx == -1
+		  && !h->forced_local
+		  && h->root.type != bfd_link_hash_undefweak
+		  && (h->got.offset & 1) == 0
+		  && bfd_link_pic (info))
+		{
+		  asection *s = htab->elf.srelgot;
+		  Elf_Internal_Rela outrel;
+
+		  BFD_ASSERT (s != NULL);
+
+		  memset (&outrel, 0, sizeof outrel);
+		  sparc_elf_append_rela (output_bfd, s, &outrel);
+		  h->got.offset |= 1;
+		}
 	    }
 	  continue;
 	}
@@ -3170,15 +3191,13 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
 		    off &= ~1;
 		  else
 		    {
+		      /* If this symbol isn't dynamic in PIC mode, treat it
+			 like a local symbol in PIC mode below.  */
 		      if (h->dynindx == -1
 			  && !h->forced_local
 			  && h->root.type != bfd_link_hash_undefweak
 			  && bfd_link_pic (info))
-			{
-			  /* If this symbol isn't dynamic in PIC
-			     generate R_SPARC_RELATIVE here.  */
-			  relative_reloc = TRUE;
-			}
+			relative_reloc = TRUE;
 		      else
 			SPARC_ELF_PUT_WORD (htab, output_bfd, relocation,
 					    htab->elf.sgot->contents + off);
@@ -3202,6 +3221,8 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
 		off &= ~1;
 	      else
 		{
+		  /* For a local symbol in PIC mode, we need to generate a
+		     R_SPARC_RELATIVE reloc for the dynamic linker.  */
 		  if (bfd_link_pic (info))
 		    relative_reloc = TRUE;
 		  else
@@ -3213,12 +3234,9 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
 
 	  if (relative_reloc)
 	    {
-	      asection *s;
+	      asection *s = htab->elf.srelgot;
 	      Elf_Internal_Rela outrel;
 
-	      /* We need to generate a R_SPARC_RELATIVE reloc
-		 for the dynamic linker.  */
-	      s = htab->elf.srelgot;
 	      BFD_ASSERT (s != NULL);
 
 	      outrel.r_offset = (htab->elf.sgot->output_section->vma
@@ -3349,9 +3367,9 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
 	     in PIE.  */
 	  if ((bfd_link_pic (info)
 	       && (h == NULL
-		   || ((ELF_ST_VISIBILITY (h->other) == STV_DEFAULT
-			&& !resolved_to_zero)
-		       || h->root.type != bfd_link_hash_undefweak))
+		   || !(h->root.type == bfd_link_hash_undefweak
+			&& (ELF_ST_VISIBILITY (h->other) != STV_DEFAULT
+			    || resolved_to_zero)))
 	       && (! howto->pc_relative
 		   || !SYMBOL_CALLS_LOCAL (info, h)))
 	      || (!bfd_link_pic (info)
@@ -3438,7 +3456,6 @@ _bfd_sparc_elf_relocate_section (bfd *output_bfd,
 			   || !SYMBOLIC_BIND (info, h)
 			   || !h->def_regular))
 		{
-		  BFD_ASSERT (h->dynindx != -1);
 		  outrel.r_info = SPARC_ELF_R_INFO (htab, rel, h->dynindx, r_type);
 		  outrel.r_addend = rel->r_addend;
 		}
@@ -4270,7 +4287,7 @@ _bfd_sparc_elf_finish_dynamic_symbol (bfd *output_bfd,
   struct _bfd_sparc_elf_link_hash_table *htab;
   const struct elf_backend_data *bed;
   struct _bfd_sparc_elf_link_hash_entry  *eh;
-  bfd_boolean local_undefweak;
+  bfd_boolean resolved_to_zero;
 
   htab = _bfd_sparc_elf_hash_table (info);
   BFD_ASSERT (htab != NULL);
@@ -4281,7 +4298,7 @@ _bfd_sparc_elf_finish_dynamic_symbol (bfd *output_bfd,
   /* We keep PLT/GOT entries without dynamic PLT/GOT relocations for
      resolved undefined weak symbols in executable so that their
      references have value 0 at run-time.  */
-  local_undefweak = UNDEFINED_WEAK_RESOLVED_TO_ZERO (info, eh);
+  resolved_to_zero = UNDEFINED_WEAK_RESOLVED_TO_ZERO (info, eh);
 
   if (h->plt.offset != (bfd_vma) -1)
     {
@@ -4406,8 +4423,7 @@ _bfd_sparc_elf_finish_dynamic_symbol (bfd *output_bfd,
       loc += rela_index * bed->s->sizeof_rela;
       bed->s->swap_reloca_out (output_bfd, &rela, loc);
 
-      if (!local_undefweak
-	  && !h->def_regular)
+      if (!resolved_to_zero && !h->def_regular)
 	{
 	  /* Mark the symbol as undefined, rather than as defined in
 	     the .plt section.  Leave the value alone.  */
@@ -4421,12 +4437,14 @@ _bfd_sparc_elf_finish_dynamic_symbol (bfd *output_bfd,
 	}
     }
 
-  /* Don't generate dynamic GOT relocation against undefined weak
-     symbol in executable.  */
+  /* Don't generate dynamic GOT relocation against resolved undefined weak
+     symbols in an executable.  */
   if (h->got.offset != (bfd_vma) -1
       && _bfd_sparc_elf_hash_entry(h)->tls_type != GOT_TLS_GD
       && _bfd_sparc_elf_hash_entry(h)->tls_type != GOT_TLS_IE
-      && !local_undefweak)
+      && !(h->root.type == bfd_link_hash_undefweak
+	   && (ELF_ST_VISIBILITY (h->other) != STV_DEFAULT
+	       || resolved_to_zero)))
     {
       asection *sgot;
       asection *srela;
@@ -4462,8 +4480,8 @@ _bfd_sparc_elf_finish_dynamic_symbol (bfd *output_bfd,
 			      + (h->got.offset & ~(bfd_vma) 1));
 	  return TRUE;
 	}
-      else if (bfd_link_pic (info)
-	       && SYMBOL_REFERENCES_LOCAL (info, h))
+
+      if (bfd_link_pic (info) && SYMBOL_REFERENCES_LOCAL (info, h))
 	{
 	  asection *sec = h->root.u.def.section;
 	  if (h->type == STT_GNU_IFUNC)