[AArch64] Also puts value in place for R_AARCH64_RELATIVE

When handling absolute relocations for global symbols bind within the
shared object, AArch64 will generate one dynamic RELATIVE relocation,
but won't apply the value for this absolution relocations at static
linking stage. This is different from AArch64 gold linker and x86-64.

This is not a bug as AArch64 is RELA, there is only guarantee that
relocation addend is placed in the relocation entry.  But some
system softwares originally writen for x86-64 might assume AArch64
bfd linker gets the same behavior as x86-64, then they could take
advantage of this buy skipping those RELATIVE dynamic relocations
if the load address is the same as the static linking address.

This patch makes AArch64 BFD linker applies absolution relocations at
static linking stage for scenario described above.  Meanwhile old AArch64
android loader has a bug (PR19163) which relies on current linker behavior
as a workaround, so the same option --no-apply-dynamic-relocs added.

1 files changed, 7 insertions, 1 deletions

diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 5b9878e..eecbf87 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -2289,6 +2289,9 @@ struct elf_aarch64_link_hash_table
   /* Enable ADRP->ADR rewrite for erratum 843419 workaround.  */
   int fix_erratum_843419_adr;
 
+  /* Don't apply link-time values for dynamic relocations.  */
+  int no_apply_dynamic_relocs;
+
   /* The number of bytes in the initial entry in the PLT.  */
   bfd_size_type plt_header_size;
 
@@ -4334,7 +4337,8 @@ bfd_elfNN_aarch64_set_options (struct bfd *output_bfd,
 			       int no_enum_warn,
 			       int no_wchar_warn, int pic_veneer,
 			       int fix_erratum_835769,
-			       int fix_erratum_843419)
+			       int fix_erratum_843419,
+			       int no_apply_dynamic_relocs)
 {
   struct elf_aarch64_link_hash_table *globals;
 
@@ -4343,6 +4347,7 @@ bfd_elfNN_aarch64_set_options (struct bfd *output_bfd,
   globals->fix_erratum_835769 = fix_erratum_835769;
   globals->fix_erratum_843419 = fix_erratum_843419;
   globals->fix_erratum_843419_adr = TRUE;
+  globals->no_apply_dynamic_relocs = no_apply_dynamic_relocs;
 
   BFD_ASSERT (is_aarch64_elf (output_bfd));
   elf_aarch64_tdata (output_bfd)->no_enum_size_warning = no_enum_warn;
@@ -5208,6 +5213,7 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
 		 relocate the text and data segments independently,
 		 so the symbol does not matter.  */
 	      symbol = 0;
+	      relocate = globals->no_apply_dynamic_relocs ? FALSE : TRUE;
 	      outrel.r_info = ELFNN_R_INFO (symbol, AARCH64_R (RELATIVE));
 	      outrel.r_addend += value;
 	    }