[Commit]: AArch64: Refuse to link when unresolveable relocs are encountered

[Nick Clifton <nickc at redhat dot com>]

Hi Guys,

  I am checking in the patch below to fix a problem recently encountered
  with the AArch64 linker.  It would report unresolvable relocs but
  then continue to produce a (non-working) binary with no error code.
  
  The problem turns out to be the AArch64 final_link_relocate function,
  which was reporting the error but then returning a value of FALSE.
  Since the final_link_relocate functions return a bfd_reloc_status_type
  and a value of 0 corresponds to bfd_reloc_ok, the generic parts of the
  linker assumed that everything was OK.

  As well as fixing this issue in the AArch64 backend I have also taken
  the liberty of changing the starting value of the bfd_reloc_status
  enum so that TRUE and FALSE are no longer valid members of this enum.
  I could not find a way to have the compiler automatically detect and
  report when these unsupported values were used, but maybe that will
  come in the future.

Cheers
  Nick

bfd/ChangeLog
2017-10-12  Nick Clifton  <nickc@redhat.com>

	* reloc.c (enum bfd_reloc_status): Start values at 2.
	* bfd-in2.h: Regenerate.
	* elfnn-arch64.c (aarch64_relocate): Invert sense of function, so
	that a TRUE return indicates success.  Compare the result of
	calling _bfd_aarch64_elf_put_addend against bfd_reloc_ok.
	(build_one_stub): Change sense of tests against aarch64_relocate
	return value.
	(elfNN_aarch64_tls_relax): Return bfd_reloc_notsupported, rather
	than FALSE, when an error is detected.
	(elfNN_aarch64_final_link_relocate): Likewise.

ld/Changelog
2017-10-12  Nick Clifton  <nickc@redhat.com>

	* testsuite/ld-aarch64/pcrel_pic_defined.d: Expect errors not
	warnings.  Expect errors about unsupported relocations.
	* testsuite/ld-aarch64/pcrel_pic_undefined.d: Likewise.

diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 92970561ee..5fd314dee2 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -2610,6 +2610,8 @@ elfNN_aarch64_link_hash_table_create (bfd *abfd)
   return &ret->root.root;
 }
 
+/* Perform relocation R_TYPE.  Returns TRUE upon success, FALSE otherwise.  */
+
 static bfd_boolean
 aarch64_relocate (unsigned int r_type, bfd *input_bfd, asection *input_section,
 		  bfd_vma offset, bfd_vma value)
@@ -2625,7 +2627,7 @@ aarch64_relocate (unsigned int r_type, bfd *input_bfd, asection *input_section,
   value = _bfd_aarch64_elf_resolve_relocation (r_type, place, value, 0, FALSE);
   return _bfd_aarch64_elf_put_addend (input_bfd,
 				      input_section->contents + offset, r_type,
-				      howto, value);
+				      howto, value) == bfd_reloc_ok;
 }
 
 static enum elf_aarch64_stub_type
@@ -2965,22 +2967,22 @@ aarch64_build_one_stub (struct bfd_hash_entry *gen_entry,
   switch (stub_entry->stub_type)
     {
     case aarch64_stub_adrp_branch:
-      if (aarch64_relocate (AARCH64_R (ADR_PREL_PG_HI21), stub_bfd, stub_sec,
-			    stub_entry->stub_offset, sym_value))
+      if (!aarch64_relocate (AARCH64_R (ADR_PREL_PG_HI21), stub_bfd, stub_sec,
+			     stub_entry->stub_offset, sym_value))
 	/* The stub would not have been relaxed if the offset was out
 	   of range.  */
 	BFD_FAIL ();
 
-      if (aarch64_relocate (AARCH64_R (ADD_ABS_LO12_NC), stub_bfd, stub_sec,
-			    stub_entry->stub_offset + 4, sym_value))
+      if (!aarch64_relocate (AARCH64_R (ADD_ABS_LO12_NC), stub_bfd, stub_sec,
+			     stub_entry->stub_offset + 4, sym_value))
 	BFD_FAIL ();
       break;
 
     case aarch64_stub_long_branch:
       /* We want the value relative to the address 12 bytes back from the
          value itself.  */
-      if (aarch64_relocate (AARCH64_R (PRELNN), stub_bfd, stub_sec,
-			    stub_entry->stub_offset + 16, sym_value + 12))
+      if (!aarch64_relocate (AARCH64_R (PRELNN), stub_bfd, stub_sec,
+			     stub_entry->stub_offset + 16, sym_value + 12))
 	BFD_FAIL ();
       break;
 
@@ -3001,8 +3003,8 @@ aarch64_build_one_stub (struct bfd_hash_entry *gen_entry,
       break;
 
     case aarch64_stub_erratum_843419_veneer:
-      if (aarch64_relocate (AARCH64_R (JUMP26), stub_bfd, stub_sec,
-			    stub_entry->stub_offset + 4, sym_value + 4))
+      if (!aarch64_relocate (AARCH64_R (JUMP26), stub_bfd, stub_sec,
+			     stub_entry->stub_offset + 4, sym_value + 4))
 	BFD_FAIL ();
       break;
 
@@ -4998,7 +5000,7 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
 	    (_("%B(%A+%#Lx): unresolvable %s relocation against symbol `%s'"),
 	     input_bfd, input_section, rel->r_offset, howto->name, name);
 	  bfd_set_error (bfd_error_bad_value);
-	  return FALSE;
+	  return bfd_reloc_notsupported;
 	}
       else if (h->plt.offset == (bfd_vma) -1)
 	goto bad_ifunc_reloc;
@@ -5022,7 +5024,7 @@ bad_ifunc_reloc:
 	       "symbol `%s' isn't handled by %s"), input_bfd,
 	     howto->name, name, __FUNCTION__);
 	  bfd_set_error (bfd_error_bad_value);
-	  return FALSE;
+	  return bfd_reloc_notsupported;
 
 	case BFD_RELOC_AARCH64_NN:
 	  if (rel->r_addend != 0)
@@ -5038,7 +5040,7 @@ bad_ifunc_reloc:
 		   "symbol `%s' has non-zero addend: %Ld"),
 		 input_bfd, howto->name, name, rel->r_addend);
 	      bfd_set_error (bfd_error_bad_value);
-	      return FALSE;
+	      return bfd_reloc_notsupported;
 	    }
 
 	  /* Generate dynamic relocation only when there is a
@@ -5362,7 +5364,7 @@ bad_ifunc_reloc:
 	     input_bfd, elfNN_aarch64_howto_table[howto_index].name,
 	     h->root.root.string);
 	  bfd_set_error (bfd_error_bad_value);
-	  return FALSE;
+	  return bfd_reloc_notsupported;
 	}
       /* Fall through.  */
 
@@ -8766,7 +8768,8 @@ elf_aarch64_update_plt_entry (bfd *output_bfd,
 {
   reloc_howto_type *howto = elfNN_aarch64_howto_from_bfd_reloc (r_type);
 
-  _bfd_aarch64_elf_put_addend (output_bfd, plt_entry, r_type, howto, value);
+  /* FIXME: We should check the return value from this function call.  */
+  (void) _bfd_aarch64_elf_put_addend (output_bfd, plt_entry, r_type, howto, value);
 }
 
 static void
diff --git a/bfd/reloc.c b/bfd/reloc.c
index 97a17f5147..b4d8584037 100644
--- a/bfd/reloc.c
+++ b/bfd/reloc.c
@@ -65,8 +65,9 @@ CODE_FRAGMENT
 .
 .typedef enum bfd_reloc_status
 .{
-.  {* No errors detected.  *}
-.  bfd_reloc_ok,
+.  {* No errors detected.  Note - the value 2 is used so that it
+.     will not be mistaken for the boolean TRUE or FALSE values.  *}
+.  bfd_reloc_ok = 2,
 .
 .  {* The relocation was performed, but there was an overflow.  *}
 .  bfd_reloc_overflow,
diff --git a/ld/testsuite/ld-aarch64/pcrel_pic_defined.d b/ld/testsuite/ld-aarch64/pcrel_pic_defined.d
index 743e810b96..a611e313ff 100644
--- a/ld/testsuite/ld-aarch64/pcrel_pic_defined.d
+++ b/ld/testsuite/ld-aarch64/pcrel_pic_defined.d
@@ -1,10 +1,17 @@
 #name: PC-Rel relocation against defined
 #source: pcrel.s
 #ld: -shared -e0 -defsym global_a=0x1000 -defsym global_b=0x2000
-#warning: .*: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_ADR_PREL_PG_HI21_NC against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_ADR_PREL_LO21 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_LD_PREL_LO19 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_PREL16 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_PREL32 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_PREL64 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_ADR_PREL_PG_HI21_NC against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_ADR_PREL_LO21 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_LD_PREL_LO19 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_PREL16 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_PREL32 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_PREL64 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
diff --git a/ld/testsuite/ld-aarch64/pcrel_pic_undefined.d b/ld/testsuite/ld-aarch64/pcrel_pic_undefined.d
index f7f048d9da..b5d6372235 100644
--- a/ld/testsuite/ld-aarch64/pcrel_pic_undefined.d
+++ b/ld/testsuite/ld-aarch64/pcrel_pic_undefined.d
@@ -1,10 +1,17 @@
 #name: PC-Rel relocation against undefined
 #source: pcrel.s
 #ld: -shared -e0 -defsym global_b=0x2000
-#warning: .*: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_ADR_PREL_PG_HI21_NC against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_ADR_PREL_LO21 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_LD_PREL_LO19 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_PREL16 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_PREL32 against symbol `global_a.*bind externally.*fPIC.*
-#warning: .*: relocation R_AARCH64_PREL64 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_ADR_PREL_PG_HI21_NC against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_ADR_PREL_LO21 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_LD_PREL_LO19 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_PREL16 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_PREL32 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation
+#error: .*: relocation R_AARCH64_PREL64 against symbol `global_a.*bind externally.*fPIC.*
+#error: .*: dangerous relocation: unsupported relocation