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, 46 insertions, 22 deletions

diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index d1f61be5044..25977cc56bd 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -2473,8 +2473,10 @@ elf_i386_relocate_section (bfd *output_bfd,
 		      bfd_put_32 (output_bfd, relocation,
 				  htab->elf.sgot->contents + off);
 		      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))
 			{
 			  /* PR ld/21402: If this symbol isn't dynamic
 			     in PIC, generate R_386_RELATIVE here.  */
@@ -2504,7 +2506,9 @@ elf_i386_relocate_section (bfd *output_bfd,
 			      htab->elf.sgot->contents + off);
 		  local_got_offsets[r_symndx] |= 1;
 
-		  if (bfd_link_pic (info))
+		  /* NB: Don't generate relative relocation here if it
+		     has been generated by DT_RELR.  */
+		  if (!info->enable_dt_relr && bfd_link_pic (info))
 		    relative_reloc = true;
 		}
 	    }
@@ -2707,6 +2711,7 @@ elf_i386_relocate_section (bfd *output_bfd,
 	    {
 	      Elf_Internal_Rela outrel;
 	      bool skip, relocate;
+	      bool generate_dynamic_reloc = true;
 	      asection *sreloc;
 
 	      /* When generating a shared object, these relocations
@@ -2734,23 +2739,33 @@ elf_i386_relocate_section (bfd *output_bfd,
 		{
 		  /* This symbol is local, or marked to become local.  */
 		  relocate = true;
-		  outrel.r_info = ELF32_R_INFO (0, R_386_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 = ELF32_R_INFO (0, R_386_RELATIVE);
 
-		  if (htab->params->report_relative_reloc)
-		    _bfd_x86_elf_link_report_relative_reloc
-		      (info, input_section, h, sym, "R_386_RELATIVE",
-		       &outrel);
+		      if (htab->params->report_relative_reloc)
+			_bfd_x86_elf_link_report_relative_reloc
+			  (info, input_section, h, sym, "R_386_RELATIVE",
+			   &outrel);
+		    }
 		}
 
-	      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;
 
-	      elf_append_rel (output_bfd, sreloc, &outrel);
+		  if (sreloc == NULL || sreloc->contents == NULL)
+		    {
+		      r = bfd_reloc_notsupported;
+		      goto check_relocation_error;
+		    }
+
+		  elf_append_rel (output_bfd, sreloc, &outrel);
+		}
 
 	      /* If this reloc is against an external symbol, we do
 		 not want to fiddle with the addend.  Otherwise, we
@@ -3776,6 +3791,7 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd,
       Elf_Internal_Rela rel;
       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.  */
@@ -3858,8 +3874,13 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd,
 	       && SYMBOL_REFERENCES_LOCAL_P (info, h))
 	{
 	  BFD_ASSERT((h->got.offset & 1) != 0);
-	  rel.r_info = ELF32_R_INFO (0, R_386_RELATIVE);
-	  relative_reloc_name = "R_386_RELATIVE";
+	  if (info->enable_dt_relr)
+	    generate_dynamic_reloc = false;
+	  else
+	    {
+	      rel.r_info = ELF32_R_INFO (0, R_386_RELATIVE);
+	      relative_reloc_name = "R_386_RELATIVE";
+	    }
 	}
       else
 	{
@@ -3870,12 +3891,15 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd,
 	  rel.r_info = ELF32_R_INFO (h->dynindx, R_386_GLOB_DAT);
 	}
 
-      if (relative_reloc_name != NULL
-	  && htab->params->report_relative_reloc)
-	_bfd_x86_elf_link_report_relative_reloc
-	  (info, relgot, h, sym, relative_reloc_name, &rel);
+      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, &rel);
 
-      elf_append_rel (output_bfd, relgot, &rel);
+	  elf_append_rel (output_bfd, relgot, &rel);
+	}
     }
 
   if (h->needs_copy)