RISC-V: Clarify link behaviors of R_RISCV_32/64 relocations with ABS symbol.

There are two improvements, which are all referenced to aarch64,

* R_RISCV_32 with non ABS symbol cannot be used under RV64 when making
  shard objects.

* Don't need dynamic relocation for R_RISCV_32/64 under RV32/RV64 when
  making shared objects, if the referenced symbol is local ABS symbol.

However, considering this link,
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/issues/341

Seems like we should makes all R_RISCV_32/64 relocs with ABS symbol
that don't need any dynamic relocations when making the shared objects.
But anyway, I just sync the current behavior as aarch64 ld, in case
there are any unexpected behaviors happen.

Passed the gcc/binutils regressions in riscv-gnu-toolchain.

bfd/
    * elfnn-riscv.c (riscv_elf_check_relocs): Only allow R_RISCV_32 with ABS
    symbol under RV64.
    (riscv_elf_relocate_section): R_RISCV_32/64 with local ABS symbol under
    RV32/RV64 doesn't need any dynamic relocation when making shared objects.
    I just make the implementations similar to other targets, so that will be
    more easy to mainatain.
ld/
    * testsuite/ld-riscv-elf/data-reloc*: New testcases.
    * testsuite/ld-riscv-elf/ld-riscv-elf.exp: Added new data-reloc* testcases,
    and need to make ifunc-seperate* testcases work for rv32.
    * testsuite/ld-riscv-elf/ifunc-seperate-caller-nonplt.s: Likewise.
    * testsuite/ld-riscv-elf/ifunc-seperate-caller-plt.s: Likewise.

1 files changed, 53 insertions, 8 deletions

diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index 59e949a..00f034a 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -734,6 +734,7 @@ riscv_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
       unsigned int r_type;
       unsigned int r_symndx;
       struct elf_link_hash_entry *h;
+      bool is_abs_symbol = false;
 
       r_symndx = ELFNN_R_SYM (rel->r_info);
       r_type = ELFNN_R_TYPE (rel->r_info);
@@ -753,6 +754,8 @@ riscv_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
 	  if (isym == NULL)
 	    return false;
 
+	  is_abs_symbol = isym->st_shndx == SHN_ABS ? true : false;
+
 	  /* Check relocation against local STT_GNU_IFUNC symbol.  */
 	  if (ELF_ST_TYPE (isym->st_info) == STT_GNU_IFUNC)
 	    {
@@ -778,6 +781,8 @@ riscv_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
 	  while (h->root.type == bfd_link_hash_indirect
 		 || h->root.type == bfd_link_hash_warning)
 	    h = (struct elf_link_hash_entry *) h->root.u.i.link;
+
+	  is_abs_symbol = bfd_is_abs_symbol (&h->root) ? true : false;
 	}
 
       if (h != NULL)
@@ -879,13 +884,31 @@ riscv_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
 	case R_RISCV_HI20:
 	  if (bfd_link_pic (info))
 	    return bad_static_reloc (abfd, r_type, h);
-	  /* Fall through.  */
+	  goto static_reloc;
+
+	case R_RISCV_32:
+	  if (ARCH_SIZE > 32
+	      && bfd_link_pic (info)
+	      && (sec->flags & SEC_ALLOC) != 0)
+	    {
+	      if (is_abs_symbol)
+		break;
+
+	      reloc_howto_type *r_t = riscv_elf_rtype_to_howto (abfd, r_type);
+	      _bfd_error_handler
+		(_("%pB: relocation %s against non-absolute symbol `%s' can "
+		   "not be used in RVNN when making a shared object"),
+		 abfd, r_t ? r_t->name : _("<unknown>"),
+		 h != NULL ? h->root.root.string : "a local symbol");
+	      bfd_set_error (bfd_error_bad_value);
+	      return false;
+	    }
+	  goto static_reloc;
 
 	case R_RISCV_COPY:
 	case R_RISCV_JUMP_SLOT:
 	case R_RISCV_RELATIVE:
 	case R_RISCV_64:
-	case R_RISCV_32:
 	  /* Fall through.  */
 
 	static_reloc:
@@ -2630,6 +2653,11 @@ riscv_elf_relocate_section (bfd *output_bfd,
 	  break;
 
 	case R_RISCV_32:
+	  /* Non ABS symbol should be blocked in check_relocs.  */
+	  if (ARCH_SIZE > 32)
+	    break;
+	  /* Fall through.  */
+
 	case R_RISCV_64:
 	  if ((input_section->flags & SEC_ALLOC) == 0)
 	    break;
@@ -2639,7 +2667,6 @@ riscv_elf_relocate_section (bfd *output_bfd,
 	    {
 	      Elf_Internal_Rela outrel;
 	      asection *sreloc;
-	      bool skip_static_relocation, skip_dynamic_relocation;
 
 	      /* When generating a shared object, these relocations
 		 are copied into the output file to be resolved at run
@@ -2648,26 +2675,44 @@ riscv_elf_relocate_section (bfd *output_bfd,
 	      outrel.r_offset =
 		_bfd_elf_section_offset (output_bfd, info, input_section,
 					 rel->r_offset);
-	      skip_static_relocation = outrel.r_offset != (bfd_vma) -2;
-	      skip_dynamic_relocation = outrel.r_offset >= (bfd_vma) -2;
+	      bool skip = false;
+	      bool relocate = false;
+	      if (outrel.r_offset == (bfd_vma) -1)
+		skip = true;
+	      else if (outrel.r_offset == (bfd_vma) -2)
+		{
+		  skip = true;
+		  relocate = true;
+		}
+	      else if (h != NULL && bfd_is_abs_symbol (&h->root))
+		{
+		  /* Don't need dynamic reloc when the ABS symbol is
+		     non-dynamic or forced to local.  Maybe just use
+		     SYMBOL_REFERENCES_LOCAL to check?  */
+		  skip = (h->forced_local || (h->dynindx == -1));
+		  relocate = skip;
+		}
+
 	      outrel.r_offset += sec_addr (input_section);
 
-	      if (skip_dynamic_relocation)
-		memset (&outrel, 0, sizeof outrel);
+	      if (skip)
+		memset (&outrel, 0, sizeof outrel);	/* R_RISCV_NONE.  */
 	      else if (RISCV_COPY_INPUT_RELOC (info, h))
 		{
+		  /* Maybe just use !SYMBOL_REFERENCES_LOCAL to check?  */
 		  outrel.r_info = ELFNN_R_INFO (h->dynindx, r_type);
 		  outrel.r_addend = rel->r_addend;
 		}
 	      else
 		{
+		  /* This symbol is local, or marked to become local.  */
 		  outrel.r_info = ELFNN_R_INFO (0, R_RISCV_RELATIVE);
 		  outrel.r_addend = relocation + rel->r_addend;
 		}
 
 	      sreloc = elf_section_data (input_section)->sreloc;
 	      riscv_elf_append_rela (output_bfd, sreloc, &outrel);
-	      if (skip_static_relocation)
+	      if (!relocate)
 		continue;
 	    }
 	  break;