[AArch64] PR18279, fix handling of GOT entry for local symbol

[Jiong Wang <jiong dot wang at arm dot com>]

I reproduced on current binutils-gdb HEAD. The reason is as what RTH has
explained we are handling GOT entry for local symbol incorrectly thus
that relocation still relocate the symbol itself instead of the
associated GOT entry. While the symbol itself may contains value not
8bytes aligned, then trigger alignment check errors.

Even worse, if that symbol contains a value 8bytes aligned, then we pass
the later alignment check, report nothing, and generate buggy binary
silently.

The patch will handle GOT entry for local symbol as the following:

  * apply the relocation using GOT entry address.
  * generate a R_AARCH64_RELATIVE relocation for the GOT entry, so the local
    symbol's address could be updated with the shared object's runtime base address.

OK for trunk?

no regression on binutils-gdb native test.
pass the testcase given by David.
pass my small "exectuable + .so" execution test, verified the runtime behavior is OK.

2015-04-20  Jiong. Wang  <jiong.wang@arm.com>

bfd/
  PR18279
  * elfnn-aarch64.c (elfNN_aarch64_size_dynamic): Count local symbol for
  GOT_NORMAL for both sgot/srelgot section.
  (elfNN_aarch64_final_link_relocate): Relocate against GOT entry
  address and generate necessary runtime relocation for GOT entry.
-- 
Regards,
Jiong

diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 85cf856..4695846 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -4447,10 +4447,11 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
   bfd_reloc_code_real_type new_bfd_r_type;
   unsigned long r_symndx;
   bfd_byte *hit_data = contents + rel->r_offset;
-  bfd_vma place;
+  bfd_vma place, off;
   bfd_signed_vma signed_addend;
   struct elf_aarch64_link_hash_table *globals;
   bfd_boolean weak_undef_p;
+  asection *base_got;
 
   globals = elf_aarch64_hash_table (info);
 
@@ -4490,8 +4491,6 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
     {
       asection *plt;
       const char *name;
-      asection *base_got;
-      bfd_vma off;
 
       if ((input_section->flags & SEC_ALLOC) == 0
 	  || h->plt.offset == (bfd_vma) -1)
@@ -4849,6 +4848,51 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
 	  value = _bfd_aarch64_elf_resolve_relocation (bfd_r_type, place, value,
 						       0, weak_undef_p);
 	}
+      else
+      {
+	struct elf_aarch64_local_symbol *locals
+	  = elf_aarch64_locals (input_bfd);
+
+	if (locals == NULL)
+	  abort ();
+
+	off = symbol_got_offset (input_bfd, h, r_symndx);
+	base_got = globals->root.sgot;
+	bfd_vma got_entry_addr = (base_got->output_section->vma
+				  + base_got->output_offset + off);
+
+	if (!symbol_got_offset_mark_p (input_bfd, h, r_symndx))
+	  {
+	    bfd_put_64 (output_bfd, value, base_got->contents + off);
+
+	    if (info->shared)
+	      {
+		asection *s;
+		Elf_Internal_Rela outrel;
+
+		/* For local symbol, we have done absolute relocation in static
+		   linking stageh. While for share library, we need to update
+		   the content of GOT entry according to the share objects
+		   loading base address. So we need to generate a
+		   R_AARCH64_RELATIVE reloc for dynamic linker.  */
+		s = globals->root.srelgot;
+		if (s == NULL)
+		  abort ();
+
+		outrel.r_offset = got_entry_addr;
+		outrel.r_info = ELFNN_R_INFO (0, AARCH64_R (RELATIVE));
+		outrel.r_addend = value;
+		elf_append_rela (output_bfd, s, &outrel);
+	      }
+
+	    symbol_got_offset_mark (input_bfd, h, r_symndx);
+	  }
+
+	/* Update the relocation value to GOT entry addr as we have transformed
+	   the direct data access into indirect data access through GOT.  */
+	value = got_entry_addr;
+      }
+
       break;
 
     case BFD_RELOC_AARCH64_TLSGD_ADR_PAGE21:
@@ -7504,7 +7548,8 @@ elfNN_aarch64_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 		  htab->root.sgot->size += GOT_ENTRY_SIZE * 2;
 		}
 
-	      if (got_type & GOT_TLS_IE)
+	      if (got_type & GOT_TLS_IE
+		  || got_type & GOT_NORMAL)
 		{
 		  locals[i].got_offset = htab->root.sgot->size;
 		  htab->root.sgot->size += GOT_ENTRY_SIZE;
@@ -7514,10 +7559,6 @@ elfNN_aarch64_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 		{
 		}
 
-	      if (got_type == GOT_NORMAL)
-		{
-		}
-
 	      if (info->shared)
 		{
 		  if (got_type & GOT_TLSDESC_GD)
@@ -7530,7 +7571,8 @@ elfNN_aarch64_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
 		  if (got_type & GOT_TLS_GD)
 		    htab->root.srelgot->size += RELOC_SIZE (htab) * 2;
 
-		  if (got_type & GOT_TLS_IE)
+		  if (got_type & GOT_TLS_IE
+		      || got_type & GOT_NORMAL)
 		    htab->root.srelgot->size += RELOC_SIZE (htab);
 		}
 	    }