x86: Add DT_RELR support

DT_RELR is implemented with linker relaxation:

1. During linker relaxation, we scan input relocations with the same
logic in relocate_section to determine if a relative relocation should
be generated and save the relative relocation candidate information for
sizing the DT_RELR section later after all symbols addresses can be
determined.  For these relative relocations which can't be placed in
the DT_RELR section, they will be placed in the rela.dyn/rel.dyn
section.
2. When DT_RELR is enabled, _bfd_elf_map_sections_to_segments calls a
backend function to size the DT_RELR section which will compute the
DT_RELR section size and tell ldelf_map_segments to layout sections
again when the DT_RELR section size has been increased.
3. After regular symbol processing is finished, bfd_elf_final_link calls
a backend function to finish the DT_RELR section.

	* elf32-i386.c (elf_i386_relocate_section): Don't generate
	relative relocation when DT_RELR is enabled.
	(elf_i386_finish_dynamic_symbol): Likewise.
	* elf64-x86-64.c (elf_x86_64_relocate_section): Don't generate
	relative relocation when DT_RELR is enabled.
	(elf_x86_64_finish_dynamic_symbol): Likewise.
	* elfxx-x86.c (_bfd_x86_elf_link_hash_table_create): Initialize
	relative_r_type, relative_r_name, elf_append_reloc,
	elf_write_addend and elf_write_addend_in_got.
	(elf_x86_relative_reloc_record_add): New function.
	(_bfd_x86_elf_link_relax_section): Likewise.
	(elf64_dt_relr_bitmap_add): Likewise.
	(elf32_dt_relr_bitmap_add): Likewise.
	(_bfd_elf32_write_addend): Likewise.
	(_bfd_elf64_write_addend): Likewise.
	(elf_x86_size_or_finish_relative_reloc): Likewise.
	(elf_x86_compute_dl_relr_bitmap): Likewise.
	(elf_x86_write_dl_relr_bitmap): Likewise.
	(elf_x86_relative_reloc_compare ): Likewise.
	(_bfd_elf_x86_size_relative_relocs): Likewise.
	(_bfd_elf_x86_finish_relative_relocs): Likewise.
	(_bfd_x86_elf_size_dynamic_sections): Skip the .relr.dyn section.
	(_bfd_x86_elf_finish_dynamic_sections): Convert 3 spare dynamic
	tags to DT_RELR, DT_RELRSZ and for compact relative relocation.
	* elfxx-x86.h (X86_64_GOT_TYPE_P): New.
	(I386_GOT_TYPE_P): Likewise.
	(X86_GOT_TYPE_P): Likewise.
	(X86_64_RELATIVE_RELOC_TYPE_P): Likewise.
	(I386_RELATIVE_RELOC_TYPE_P): Likewise.
	(X86_RELATIVE_RELOC_TYPE_P): Likewise.
	(X86_LOCAL_GOT_RELATIVE_RELOC_P): Likewise.
	(I386_PCREL_TYPE_P): Likewise.
	(X86_64_PCREL_TYPE_P): Likewise.
	(X86_64_NEED_DYNAMIC_RELOC_TYPE_P): Rewrite.
	(I386_NEED_DYNAMIC_RELOC_TYPE_P): Likewise.
	(GENERATE_DYNAMIC_RELOCATION_P): Also check rel_from_abs.
	(elf_x86_link_hash_entry): Add got_relative_reloc_done.
	(elf_x86_relative_reloc_record): New.
	(elf_x86_relative_reloc_data): Likewise.
	(elf_dt_relr_bitmap): Likewise.
	(elf_x86_link_hash_table): Add dt_relr_bitmap, relative_reloc,
	unaligned_relative_reloc, relative_r_type, relative_r_name,
	elf_append_reloc, elf_write_addend, elf_write_addend_in_got and
	relative_reloc_done.
	(elf_x86_relative_reloc_done): New.
	(relative_reloc_packed): Likewise.
	(_bfd_x86_elf_link_relax_section): Likewise.
	(_bfd_elf_x86_size_relative_relocs): Likewise.
	(_bfd_elf_x86_finish_relative_relocs): Likewise.
	(_bfd_elf32_write_addend): Likewise.
	(_bfd_elf64_write_addend): Likewise.
	(bfd_elf32_bfd_relax_section): Likewise.
	(bfd_elf64_bfd_relax_section): Likewise.
	(elf_backend_size_relative_relocs): Likewise.
	(elf_backend_finish_relative_relocs): Likewise.
	(elf_x86_allocate_local_got_info): Also allocate
	relative_reloc_done.

1 files changed, 55 insertions, 28 deletions

diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index ad885f8..02ca552 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -2867,7 +2867,10 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 			 as -1 | 1 still is -1.  */
 		      h->got.offset |= 1;
 
-		      if (GENERATE_RELATIVE_RELOC_P (info, h))
+		      /* NB: Don't generate relative relocation here if
+			 it has been generated by DT_RELR.  */
+		      if (!info->enable_dt_relr
+			  && GENERATE_RELATIVE_RELOC_P (info, h))
 			{
 			  /* If this symbol isn't dynamic in PIC,
 			     generate R_X86_64_RELATIVE here.  */
@@ -2899,8 +2902,11 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 
 		  /* NB: GOTPCREL relocations against local absolute
 		     symbol store relocation value in the GOT slot
-		     without relative relocation.  */
-		  if (bfd_link_pic (info)
+		     without relative relocation.  Don't generate
+		     relative relocation here if it has been generated
+		     by DT_RELR.  */
+		  if (!info->enable_dt_relr
+		      && bfd_link_pic (info)
 		      && !(sym->st_shndx == SHN_ABS
 			   && (r_type == R_X86_64_GOTPCREL
 			       || r_type == R_X86_64_GOTPCRELX
@@ -3215,6 +3221,7 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 	    {
 	      Elf_Internal_Rela outrel;
 	      bool skip, relocate;
+	      bool generate_dynamic_reloc = true;
 	      asection *sreloc;
 	      const char *relative_reloc_name = NULL;
 
@@ -3253,9 +3260,17 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 			  && htab->params->no_reloc_overflow_check))
 		    {
 		      relocate = true;
-		      outrel.r_info = htab->r_info (0, R_X86_64_RELATIVE);
-		      outrel.r_addend = relocation + rel->r_addend;
-		      relative_reloc_name = "R_X86_64_RELATIVE";
+		      /* NB: Don't generate relative relocation here if
+			 it has been generated by DT_RELR.  */
+		      if (info->enable_dt_relr)
+			generate_dynamic_reloc = false;
+		      else
+			{
+			  outrel.r_info =
+			    htab->r_info (0, R_X86_64_RELATIVE);
+			  outrel.r_addend = relocation + rel->r_addend;
+			  relative_reloc_name = "R_X86_64_RELATIVE";
+			}
 		    }
 		  else if (r_type == R_X86_64_64
 			   && !ABI_64_P (output_bfd))
@@ -3323,21 +3338,24 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 		    }
 		}
 
-	      sreloc = elf_section_data (input_section)->sreloc;
-
-	      if (sreloc == NULL || sreloc->contents == NULL)
+	      if (generate_dynamic_reloc)
 		{
-		  r = bfd_reloc_notsupported;
-		  goto check_relocation_error;
-		}
+		  sreloc = elf_section_data (input_section)->sreloc;
 
-	      if (relative_reloc_name
-		  && htab->params->report_relative_reloc)
-		_bfd_x86_elf_link_report_relative_reloc
-		  (info, input_section, h, sym, relative_reloc_name,
-		   &outrel);
+		  if (sreloc == NULL || sreloc->contents == NULL)
+		    {
+		      r = bfd_reloc_notsupported;
+		      goto check_relocation_error;
+		    }
 
-	      elf_append_rela (output_bfd, sreloc, &outrel);
+		  if (relative_reloc_name
+		      && htab->params->report_relative_reloc)
+		    _bfd_x86_elf_link_report_relative_reloc
+		      (info, input_section, h, sym,
+		       relative_reloc_name, &outrel);
+
+		  elf_append_rela (output_bfd, sreloc, &outrel);
+		}
 
 	      /* If this reloc is against an external symbol, we do
 		 not want to fiddle with the addend.  Otherwise, we
@@ -4424,6 +4442,7 @@ elf_x86_64_finish_dynamic_symbol (bfd *output_bfd,
       Elf_Internal_Rela rela;
       asection *relgot = htab->elf.srelgot;
       const char *relative_reloc_name = NULL;
+      bool generate_dynamic_reloc = true;
 
       /* This symbol has an entry in the global offset table.  Set it
 	 up.  */
@@ -4506,11 +4525,16 @@ elf_x86_64_finish_dynamic_symbol (bfd *output_bfd,
 	  if (!SYMBOL_DEFINED_NON_SHARED_P (h))
 	    return false;
 	  BFD_ASSERT((h->got.offset & 1) != 0);
-	  rela.r_info = htab->r_info (0, R_X86_64_RELATIVE);
-	  rela.r_addend = (h->root.u.def.value
-			   + h->root.u.def.section->output_section->vma
-			   + h->root.u.def.section->output_offset);
-	  relative_reloc_name = "R_X86_64_RELATIVE";
+	  if (info->enable_dt_relr)
+	    generate_dynamic_reloc = false;
+	  else
+	    {
+	      rela.r_info = htab->r_info (0, R_X86_64_RELATIVE);
+	      rela.r_addend = (h->root.u.def.value
+			       + h->root.u.def.section->output_section->vma
+			       + h->root.u.def.section->output_offset);
+	      relative_reloc_name = "R_X86_64_RELATIVE";
+	    }
 	}
       else
 	{
@@ -4522,12 +4546,15 @@ elf_x86_64_finish_dynamic_symbol (bfd *output_bfd,
 	  rela.r_addend = 0;
 	}
 
-      if (relative_reloc_name != NULL
-	  && htab->params->report_relative_reloc)
-	_bfd_x86_elf_link_report_relative_reloc
-	  (info, relgot, h, sym, relative_reloc_name, &rela);
+      if (generate_dynamic_reloc)
+	{
+	  if (relative_reloc_name != NULL
+	      && htab->params->report_relative_reloc)
+	    _bfd_x86_elf_link_report_relative_reloc
+	      (info, relgot, h, sym, relative_reloc_name, &rela);
 
-      elf_append_rela (output_bfd, relgot, &rela);
+	  elf_append_rela (output_bfd, relgot, &rela);
+	}
     }
 
   if (h->needs_copy)