Re: load of in-place relocation addend in AArch64

[Nick Clifton <nickc@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 1247 bytes --]

Hi Frédéric,

   OK, I have produced a small patch (attached) which adds this warning
   message to the linker's output:

     $ ld test_AArch64_with_REL.o
     ld: test_AArch64_with_REL.o: Warning: REL type relocations are not expected for architecture 'aarch64' - support may be incomplete

   This warning does not actually stop the link from completing however.
   The reason for this is that the code where the relocations are loaded
   is shared by other tools, which do still work with REL relocations.
   For example the objdump tool is able to display the relocations without
   any problems:

     $ objdump -r test_AArch64_with_REL.o
     BFD: test_AArch64_with_REL.o: Warning: REL type relocations are not expected for architecture 'aarch64' - support may be incomplete

     test_AArch64_with_REL.o:     file format elf64-littleaarch64

     RELOCATION RECORDS FOR [.text.__icetea__virtual__com_is2t_icetea_support_test_BImpl___bar__I]:
     OFFSET           TYPE              VALUE
     0000000000000008 R_AARCH64_ABS32   com_is2t_icetea_support_test_AImpl___bar
     [...]

   This strikes me as a compromise solution at best, but it is better
   than the current situation nonetheless.

   What do you think ?

Cheers
   Nick




[-- Attachment #2: rel.warning.patch --]
[-- Type: text/x-patch, Size: 1589 bytes --]

diff --git a/bfd/elf.c b/bfd/elf.c
index db45d1a074b..02246b1360c 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -2928,6 +2928,44 @@ bfd_section_from_shdr (bfd *abfd, unsigned int shindex)
 	    goto success;
 	  }
 
+	/* Check to make sure that the target supports this type of relocation.
+	   Note - we do not treat lack of support as a failure, since we may
+	   just be displaying information from an experimental file that is
+	   using an unexpected relocation type.  Plus if we 'goto fail' here
+	   our error message will be suppressed by the format matching code.
+	   Instead we tell the users that they might not be getting the
+	   results that they expect.  */
+	static bool already_warned = false;  /* Only warn once.  */
+	if (! already_warned)
+	  {
+	    bool supported;
+	    const char * rel_name;
+
+	    switch (hdr->sh_type)
+	      {
+	      case SHT_REL:
+		supported = get_elf_backend_data (abfd)->may_use_rel_p;
+		rel_name = "REL";
+		break;
+
+	      case SHT_RELA:
+		supported = get_elf_backend_data (abfd)->may_use_rela_p;
+		rel_name = "RELA";
+		break;
+
+	      default:
+		supported = true;
+	      }
+
+	    if (! supported)
+	      {
+		/* xgettext:c-format */
+		_bfd_error_handler (_("%pB: Warning: %s type relocations are not expected for architecture '%s' - supprt may be incomplete"),
+				    abfd, rel_name, bfd_printable_name (abfd));
+		already_warned = true;
+	      }
+	  }
+
 	/* Get the symbol table.  */
 	if ((elf_elfsections (abfd)[hdr->sh_link]->sh_type == SHT_SYMTAB
 	     || elf_elfsections (abfd)[hdr->sh_link]->sh_type == SHT_DYNSYM)