[PATCH v2 6/7] bfd:pru: Enable REL relocations

[Dimitar Dimitrov <dimitar at dinux dot eu>]

Different TI toolchain versions use a mix of REL and RELA
relocations. Implement REL so that GNU LD can link object files
from all TI versions.

Unfortunately the GNU AS port does not emit REL relocations, so
I cannot add test cases.

2018-05-02  Dimitar Dimitrov  <dimitar@dinux.eu>

        * elf32-pru.c (pru_elf32_do_ldi32_relocate): Ignore addend.
        (pru_elf32_pmem_relocate): Trap - should not get here.
        (pru_elf32_relocate_section): Add support for REL relocations.
        (elf_info_to_howto_rel): Enable REL.
        (elf_backend_may_use_rel_p): Ditto.
        (elf_backend_may_use_rela_p): Ditto.
        (elf_backend_default_use_rela_p): Ditto.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>
---
 bfd/elf32-pru.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 104 insertions(+), 12 deletions(-)

diff --git a/bfd/elf32-pru.c b/bfd/elf32-pru.c
index 99ac8ade0c..0b9e7dc82b 100644
--- a/bfd/elf32-pru.c
+++ b/bfd/elf32-pru.c
@@ -539,7 +539,7 @@ pru_elf32_do_ldi32_relocate (bfd *abfd, reloc_howto_type *howto,
   bfd_signed_vma relocation;
   bfd_size_type octets = offset * bfd_octets_per_byte (abfd);
   bfd_byte *location;
-  unsigned long in1, in2, num;
+  unsigned long in1, in2;
 
   /* A hacked-up version of _bfd_final_link_relocate() follows.  */
 
@@ -564,12 +564,6 @@ pru_elf32_do_ldi32_relocate (bfd *abfd, reloc_howto_type *howto,
   in1 = bfd_get_32 (abfd, location);
   in2 = bfd_get_32 (abfd, location + 4);
 
-  /* Extract the addend - should be zero per my understanding.  */
-  num = (GET_INSN_FIELD (IMM16, in1) << 16) | GET_INSN_FIELD (IMM16, in2);
-  BFD_ASSERT (!num);
-
-  relocation += num;
-
   SET_INSN_FIELD (IMM16, in1, relocation >> 16);
   SET_INSN_FIELD (IMM16, in2, relocation & 0xffff);
 
@@ -605,6 +599,7 @@ pru_elf32_pmem_relocate (bfd *abfd, arelent *reloc_entry,
     return bfd_elf_generic_reloc (abfd, reloc_entry, symbol, data,
 				  input_section, output_bfd, error_message);
 
+  BFD_ASSERT (0);
   return pru_elf32_do_pmem_relocate (abfd, reloc_entry->howto,
 				     input_section,
 				     data, reloc_entry->address,
@@ -692,15 +687,24 @@ pru_elf32_relocate_section (bfd *output_bfd,
 			    Elf_Internal_Sym *local_syms,
 			    asection **local_sections)
 {
+  struct bfd_elf_section_data * esd = elf_section_data (input_section);
   Elf_Internal_Shdr *symtab_hdr;
   struct elf_link_hash_entry **sym_hashes;
   Elf_Internal_Rela *rel;
   Elf_Internal_Rela *relend;
+  bfd_boolean is_rel_reloc;
 
   symtab_hdr = &elf_tdata (input_bfd)->symtab_hdr;
   sym_hashes = elf_sym_hashes (input_bfd);
   relend = relocs + input_section->reloc_count;
 
+  /* See if we have a REL type relocation.  */
+  is_rel_reloc = (esd->rel.hdr != NULL);
+  /* Sanity check - only one type of relocation per section.
+     FIXME: Theoretically it is possible to have both types,
+     but if that happens how can we distinguish between the two ?  */
+  BFD_ASSERT (! is_rel_reloc || ! esd->rela.hdr);
+
   for (rel = relocs; rel < relend; rel++)
     {
       reloc_howto_type *howto;
@@ -713,6 +717,10 @@ pru_elf32_relocate_section (bfd *output_bfd,
       const char *name = NULL;
       const char* msg = (const char*) NULL;
       bfd_boolean unresolved_reloc;
+      bfd_vma addend;
+
+      /* If we are using a REL relocation then the addend should be empty.  */
+      BFD_ASSERT (! is_rel_reloc || rel->r_addend == 0);
 
       r_symndx = ELF32_R_SYM (rel->r_info);
 
@@ -755,15 +763,52 @@ pru_elf32_relocate_section (bfd *output_bfd,
 	      r = bfd_reloc_ok;
 	      break;
 
+	    case R_PRU_U16:
+	      if (is_rel_reloc)
+		{
+		  unsigned long insn;
+		  insn = bfd_get_32 (input_bfd, contents + rel->r_offset);
+		  addend = GET_INSN_FIELD (IMM16, insn);
+		}
+	      else
+		addend = rel->r_addend;
+	      r = _bfd_final_link_relocate (howto, input_bfd,
+					    input_section, contents,
+					    rel->r_offset, relocation,
+					    addend);
+	      break;
+
 	    case R_PRU_U16_PMEMIMM:
 	    case R_PRU_32_PMEM:
 	    case R_PRU_16_PMEM:
+	      if (is_rel_reloc && howto->type == R_PRU_U16_PMEMIMM)
+		{
+		  unsigned long insn;
+		  insn = bfd_get_32 (input_bfd, contents + rel->r_offset);
+		  addend = GET_INSN_FIELD (IMM16, insn) << 2;
+		}
+	      else if (is_rel_reloc && howto->type == R_PRU_32_PMEM)
+		{
+		  addend = bfd_get_32 (input_bfd, contents + rel->r_offset);
+		  addend <<= 2;
+		}
+	      else if (is_rel_reloc && howto->type == R_PRU_16_PMEM)
+		{
+		  addend = bfd_get_16 (input_bfd, contents + rel->r_offset);
+		  addend <<= 2;
+		}
+	      else
+		{
+		  BFD_ASSERT (!is_rel_reloc);
+		  addend = rel->r_addend;
+		}
 	      r = pru_elf32_do_pmem_relocate (input_bfd, howto,
 						input_section,
 						contents, rel->r_offset,
-						relocation, rel->r_addend);
+						relocation, addend);
 	      break;
 	    case R_PRU_S10_PCREL:
+	      BFD_ASSERT (! is_rel_reloc);
 	      r = pru_elf32_do_s10_pcrel_relocate (input_bfd, howto,
 						      input_section,
 						      contents,
@@ -772,6 +817,7 @@ pru_elf32_relocate_section (bfd *output_bfd,
 						      rel->r_addend);
 	      break;
 	    case R_PRU_U8_PCREL:
+	      BFD_ASSERT (! is_rel_reloc);
 	      r = pru_elf32_do_u8_pcrel_relocate (input_bfd, howto,
 						      input_section,
 						      contents,
@@ -780,29 +826,70 @@ pru_elf32_relocate_section (bfd *output_bfd,
 						      rel->r_addend);
 	      break;
 	    case R_PRU_LDI32:
+	      if (is_rel_reloc)
+		{
+		  unsigned long in1, in2;
+		  in1 = bfd_get_32 (input_bfd, contents + rel->r_offset);
+		  in2 = bfd_get_32 (input_bfd, contents + rel->r_offset + 4);
+		  addend = (GET_INSN_FIELD (IMM16, in1) << 16)
+			    | GET_INSN_FIELD (IMM16, in2);
+		}
+	      else
+		{
+		  addend = rel->r_addend;
+		}
 	      r = pru_elf32_do_ldi32_relocate (input_bfd, howto,
 					       input_section,
 					       contents,
 					       rel->r_offset,
 					       relocation,
-					       rel->r_addend);
+					       addend);
 	      break;
 	    case R_PRU_GNU_DIFF8:
 	    case R_PRU_GNU_DIFF16:
 	    case R_PRU_GNU_DIFF32:
 	    case R_PRU_GNU_DIFF16_PMEM:
 	    case R_PRU_GNU_DIFF32_PMEM:
+	      /* GNU extensions support only rela.  */
+	      BFD_ASSERT (! is_rel_reloc);
 	      /* Nothing to do here, as contents already contain the
 		 diff value.  */
 	      r = bfd_reloc_ok;
 	      break;
 
-	    default:
+	    case R_PRU_BFD_RELOC_16:
+	      if (is_rel_reloc)
+		addend = bfd_get_16 (input_bfd, contents + rel->r_offset);
+	      else
+		addend = rel->r_addend;
+	      r = _bfd_final_link_relocate (howto, input_bfd,
+					    input_section, contents,
+					    rel->r_offset, relocation,
+					    addend);
+	      break;
+
+	    case R_PRU_BFD_RELOC_32:
+	      if (is_rel_reloc)
+		addend = bfd_get_32 (input_bfd, contents + rel->r_offset);
+	      else
+		addend = rel->r_addend;
+	      r = _bfd_final_link_relocate (howto, input_bfd,
+					    input_section, contents,
+					    rel->r_offset, relocation,
+					    addend);
+	      break;
+
+	    case R_PRU_GNU_BFD_RELOC_8:
+	      BFD_ASSERT (! is_rel_reloc);
 	      r = _bfd_final_link_relocate (howto, input_bfd,
 					    input_section, contents,
 					    rel->r_offset, relocation,
 					    rel->r_addend);
 	      break;
+
+	    default:
+	      BFD_ASSERT (0);
+	      break;
 	    }
 	}
       else
@@ -1499,12 +1586,17 @@ pru_elf32_link_hash_table_create (bfd *abfd)
 #define bfd_elf32_bfd_reloc_type_lookup	  pru_elf32_bfd_reloc_type_lookup
 #define bfd_elf32_bfd_reloc_name_lookup	  pru_elf32_bfd_reloc_name_lookup
 
-/* elf_info_to_howto (using RELA relocations).  */
-
 #define elf_info_to_howto		pru_elf32_info_to_howto
+#define elf_info_to_howto_rel		NULL
 
 /* elf backend functions.  */
 
+/* TI folks like to use a mix of REL and RELA relocations.  See also
+   the MSP430 and TI C6X backends.  */
+#define elf_backend_may_use_rel_p  1
+#define elf_backend_may_use_rela_p 1
+#define elf_backend_default_use_rela_p 1
+
 #define elf_backend_rela_normal		1
 
 #define elf_backend_relocate_section	pru_elf32_relocate_section
-- 
2.11.0