AArch64: Implement choice between Cortex-A53 erratum workarounds. (PR ld/24373)

The Cortex-A53 erratum currently has two ways it can resolve the erratum when
using the flag --fix-cortex-a53-843419:

1) If the address is within the range of an ADR instruction it rewrites the ADRP
   into an ADR, and those doesn't need the use of a veneer.

2) If the address is not within range, it adds a branch to a veneer which will
   execute the final bit of the erratum workaround and branch back to the call
   site.

When we do this we always generate the veneers and we always align the size of
the text section to 4KB.  This is because we only know which workaround we can
use after all linking has finished and all addresses are known.  This means even
though the veneers are not used, we still generate the section and we still
change the size of the input section.

This is problematic for small memory devices as this would require the user to
take about a ~4KB hit in memory even though it's not even used.

Since there's no real way to restart the linking process from the final write
phase this patch solves the issue by allowing the user more control over which
erratum workaround gets used.

Concretely this changes the option --fix-cortex-a53-843419 to take optional
arguments --fix-cortex-a53-843419[=full|adr|adrp]

- full (default): Use both ADRP and ADR workaround. This is equivalent to not
		  specifying any options and is the default behavior before this
		  patch.

- adr: Only use the ADR workaround, this will not cause any increase in binary
       size but linking will fail if the referenced address is out of range of
       an ADR instruction.

- adrp: Use only the ADRP workaround, this will never rewrite your ADRP.

In the cases where the user knows how big their binaries are the `adr` option
would prevent the unneeded overhead.

bfd/ChangeLog:

	PR ld/24373
	* bfd-in.h (enum erratum_84319_opts): New
	(bfd_elf64_aarch64_set_options, bfd_elf32_aarch64_set_options): Change
	int to enum erratum_84319_opts.
	* bfd-in2.h: Regenerate.
	* elfnn-aarch64.c (struct elf_aarch64_link_hash_table): Change
	fix_erratum_843419 to use new enum, remove fix_erratum_843419_adr.
	(_bfd_aarch64_add_stub_entry_after): Conditionally create erratum stub.
	(aarch64_size_one_stub): Conditionally size erratum 843419 stubs.
	(_bfd_aarch64_resize_stubs): Amend comment.
	(elfNN_aarch64_size_stubs): Don't generate stubs when no workaround
	requested.
	(bfd_elfNN_aarch64_set_options): Use new fix_erratum_843419 enum.
	(_bfd_aarch64_erratum_843419_branch_to_stub): Implement selection of
	erratum workaround.
	(clear_erratum_843419_entry): Update erratum conditional.

ld/ChangeLog:

	PR ld/24373
	* emultempl/aarch64elf.em (PARSE_AND_LIST_LONGOPTS): Add optional args
	to flags.
	* NEWS: Add changes to flag.
	(PARSE_AND_LIST_OPTIONS): Update help descriptions.
	(PARSE_AND_LIST_ARGS_CASES): Add new options to parser.
	* testsuite/ld-aarch64/aarch64-elf.exp: Add new run_dump_tests.
	* testsuite/ld-aarch64/erratum843419-adr.d: New test.
	* testsuite/ld-aarch64/erratum843419-adrp.d: New test.
	* testsuite/ld-aarch64/erratum843419-far-adr.d: New test.
	* testsuite/ld-aarch64/erratum843419-far-full.d: New test.
	* testsuite/ld-aarch64/erratum843419-far.s: New test.
	* testsuite/ld-aarch64/erratum843419-full.d: New test.
	* testsuite/ld-aarch64/erratum843419-near.s: New test.
	* testsuite/ld-aarch64/erratum843419-no-args.d: New test.

4 files changed, 95 insertions, 23 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 7d22cc0..2e7158f 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,22 @@
+2019-05-21  Tamar Christina  <tamar.christina@arm.com>
+
+	PR ld/24373
+	* bfd-in.h (enum erratum_84319_opts): New
+	(bfd_elf64_aarch64_set_options, bfd_elf32_aarch64_set_options): Change
+	int to enum erratum_84319_opts.
+	* bfd-in2.h: Regenerate.
+	* elfnn-aarch64.c (struct elf_aarch64_link_hash_table): Change
+	fix_erratum_843419 to use new enum, remove fix_erratum_843419_adr.
+	(_bfd_aarch64_add_stub_entry_after): Conditionally create erratum stub.
+	(aarch64_size_one_stub): Conditionally size erratum 843419 stubs.
+	(_bfd_aarch64_resize_stubs): Amend comment.
+	(elfNN_aarch64_size_stubs): Don't generate stubs when no workaround
+	requested.
+	(bfd_elfNN_aarch64_set_options): Use new fix_erratum_843419 enum.
+	(_bfd_aarch64_erratum_843419_branch_to_stub): Implement selection of
+	erratum workaround.
+	(clear_erratum_843419_entry): Update erratum conditional.
+
 2019-05-21  Senthil Kumar Selvaraj  <senthilkumar.selvaraj@microchip.com>
 
 	PR ld/24571
diff --git a/bfd/bfd-in.h b/bfd/bfd-in.h
index b753a9e..890a79d 100644
--- a/bfd/bfd-in.h
+++ b/bfd/bfd-in.h
@@ -1027,12 +1027,21 @@ typedef struct
   aarch64_enable_bti_type bti_type;
 } aarch64_bti_pac_info;
 
+/* An enum to define what kind of erratum fixes we should apply.  This gives the
+   user a bit more control over the sequences we generate.  */
+typedef enum
+{
+  ERRAT_NONE  = (1 << 0),  /* No erratum workarounds allowed.  */
+  ERRAT_ADR   = (1 << 1),  /* Erratum workarounds using ADR allowed.  */
+  ERRAT_ADRP  = (1 << 2),  /* Erratum workarounds using ADRP are allowed.  */
+} erratum_84319_opts;
+
 extern void bfd_elf64_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int, int,
+  (bfd *, struct bfd_link_info *, int, int, int, int, erratum_84319_opts, int,
    aarch64_bti_pac_info);
 
 extern void bfd_elf32_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int, int,
+  (bfd *, struct bfd_link_info *, int, int, int, int, erratum_84319_opts, int,
    aarch64_bti_pac_info);
 
 /* ELF AArch64 mapping symbol support.  */
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 9f60f57..65e2e01 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -1034,12 +1034,21 @@ typedef struct
   aarch64_enable_bti_type bti_type;
 } aarch64_bti_pac_info;
 
+/* An enum to define what kind of erratum fixes we should apply.  This gives the
+   user a bit more control over the sequences we generate.  */
+typedef enum
+{
+  ERRAT_NONE  = (1 << 0),  /* No erratum workarounds allowed.  */
+  ERRAT_ADR   = (1 << 1),  /* Erratum workarounds using ADR allowed.  */
+  ERRAT_ADRP  = (1 << 2),  /* Erratum workarounds using ADRP are allowed.  */
+} erratum_84319_opts;
+
 extern void bfd_elf64_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int, int,
+  (bfd *, struct bfd_link_info *, int, int, int, int, erratum_84319_opts, int,
    aarch64_bti_pac_info);
 
 extern void bfd_elf32_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int, int,
+  (bfd *, struct bfd_link_info *, int, int, int, int, erratum_84319_opts, int,
    aarch64_bti_pac_info);
 
 /* ELF AArch64 mapping symbol support.  */
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 8940f4e..2931018 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -2628,10 +2628,7 @@ struct elf_aarch64_link_hash_table
   int fix_erratum_835769;
 
   /* Fix erratum 843419.  */
-  int fix_erratum_843419;
-
-  /* Enable ADRP->ADR rewrite for erratum 843419 workaround.  */
-  int fix_erratum_843419_adr;
+  erratum_84319_opts fix_erratum_843419;
 
   /* Don't apply link-time values for dynamic relocations.  */
   int no_apply_dynamic_relocs;
@@ -3229,7 +3226,10 @@ _bfd_aarch64_add_stub_entry_after (const char *stub_name,
   asection *stub_sec;
   struct elf_aarch64_stub_hash_entry *stub_entry;
 
-  stub_sec = _bfd_aarch64_get_stub_for_link_section (link_section, htab);
+  stub_sec = NULL;
+  /* Only create the actual stub if we will end up needing it.  */
+  if (htab->fix_erratum_843419 & ERRAT_ADRP)
+    stub_sec = _bfd_aarch64_get_stub_for_link_section (link_section, htab);
   stub_entry = aarch64_stub_hash_lookup (&htab->stub_hash_table, stub_name,
 					 TRUE, FALSE);
   if (stub_entry == NULL)
@@ -3374,14 +3374,15 @@ aarch64_build_one_stub (struct bfd_hash_entry *gen_entry,
    we know stub section sizes.  */
 
 static bfd_boolean
-aarch64_size_one_stub (struct bfd_hash_entry *gen_entry,
-		       void *in_arg ATTRIBUTE_UNUSED)
+aarch64_size_one_stub (struct bfd_hash_entry *gen_entry, void *in_arg)
 {
   struct elf_aarch64_stub_hash_entry *stub_entry;
+  struct elf_aarch64_link_hash_table *htab;
   int size;
 
   /* Massage our args to the form they really have.  */
   stub_entry = (struct elf_aarch64_stub_hash_entry *) gen_entry;
+  htab = (struct elf_aarch64_link_hash_table *) in_arg;
 
   switch (stub_entry->stub_type)
     {
@@ -3395,7 +3396,11 @@ aarch64_size_one_stub (struct bfd_hash_entry *gen_entry,
       size = sizeof (aarch64_erratum_835769_stub);
       break;
     case aarch64_stub_erratum_843419_veneer:
-      size = sizeof (aarch64_erratum_843419_stub);
+      {
+	if (htab->fix_erratum_843419 == ERRAT_ADR)
+	  return TRUE;
+	size = sizeof (aarch64_erratum_843419_stub);
+      }
       break;
     default:
       abort ();
@@ -4060,8 +4065,10 @@ _bfd_aarch64_resize_stubs (struct elf_aarch64_link_hash_table *htab)
       /* Ensure all stub sections have a size which is a multiple of
 	 4096.  This is important in order to ensure that the insertion
 	 of stub sections does not in itself move existing code around
-	 in such a way that new errata sequences are created.  */
-      if (htab->fix_erratum_843419)
+	 in such a way that new errata sequences are created.  We only do this
+	 when the ADRP workaround is enabled.  If only the ADR workaround is
+	 enabled then the stubs workaround won't ever be used.  */
+      if (htab->fix_erratum_843419 & ERRAT_ADRP)
 	if (section->size)
 	  section->size = BFD_ALIGN (section->size, 0x1000);
     }
@@ -4284,7 +4291,7 @@ elfNN_aarch64_size_stubs (bfd *output_bfd,
       (*htab->layout_sections_again) ();
     }
 
-  if (htab->fix_erratum_843419)
+  if (htab->fix_erratum_843419 != ERRAT_NONE)
     {
       bfd *input_bfd;
 
@@ -4755,7 +4762,7 @@ 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,
+			       erratum_84319_opts fix_erratum_843419,
 			       int no_apply_dynamic_relocs,
 			       aarch64_bti_pac_info bp_info)
 {
@@ -4764,8 +4771,10 @@ bfd_elfNN_aarch64_set_options (struct bfd *output_bfd,
   globals = elf_aarch64_hash_table (link_info);
   globals->pic_veneer = pic_veneer;
   globals->fix_erratum_835769 = fix_erratum_835769;
+  /* If the default options are used, then ERRAT_ADR will be set by default
+     which will enable the ADRP->ADR workaround for the erratum 843419
+     workaround.  */
   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));
@@ -5235,9 +5244,18 @@ _bfd_aarch64_erratum_843419_branch_to_stub (struct bfd_hash_entry *gen_entry,
       || stub_entry->stub_type != aarch64_stub_erratum_843419_veneer)
     return TRUE;
 
-  insn = bfd_getl32 (contents + stub_entry->target_value);
-  bfd_putl32 (insn,
-	      stub_entry->stub_sec->contents + stub_entry->stub_offset);
+  BFD_ASSERT (((htab->fix_erratum_843419 & ERRAT_ADRP) && stub_entry->stub_sec)
+	      || (htab->fix_erratum_843419 & ERRAT_ADR));
+
+  /* Only update the stub section if we have one.  We should always have one if
+     we're allowed to use the ADRP errata workaround, otherwise it is not
+     required.  */
+  if (stub_entry->stub_sec)
+    {
+      insn = bfd_getl32 (contents + stub_entry->target_value);
+      bfd_putl32 (insn,
+		  stub_entry->stub_sec->contents + stub_entry->stub_offset);
+    }
 
   place = (section->output_section->vma + section->output_offset
 	   + stub_entry->adrp_offset);
@@ -5251,14 +5269,16 @@ _bfd_aarch64_erratum_843419_branch_to_stub (struct bfd_hash_entry *gen_entry,
      ((bfd_vma) _bfd_aarch64_decode_adrp_imm (insn) << 12, 33)
      - (place & 0xfff));
 
-  if (htab->fix_erratum_843419_adr
+  if ((htab->fix_erratum_843419 & ERRAT_ADR)
       && (imm >= AARCH64_MIN_ADRP_IMM  && imm <= AARCH64_MAX_ADRP_IMM))
     {
       insn = (_bfd_aarch64_reencode_adr_imm (AARCH64_ADR_OP, imm)
 	      | AARCH64_RT (insn));
       bfd_putl32 (insn, contents + stub_entry->adrp_offset);
+      /* Stub is not needed, don't map it out.  */
+      stub_entry->stub_type = aarch64_stub_none;
     }
-  else
+  else if (htab->fix_erratum_843419 & ERRAT_ADRP)
     {
       bfd_vma veneered_insn_loc;
       bfd_vma veneer_entry_loc;
@@ -5285,6 +5305,21 @@ _bfd_aarch64_erratum_843419_branch_to_stub (struct bfd_hash_entry *gen_entry,
       branch_insn |= branch_offset;
       bfd_putl32 (branch_insn, contents + stub_entry->target_value);
     }
+  else
+    {
+      abfd = stub_entry->target_section->owner;
+      _bfd_error_handler
+	(_("%pB: error: erratum 843419 immediate 0x%lx "
+	   "out of range for ADR (input file too large) and "
+	   "--fix-cortex-a53-843419=adr used.  Run the linker with "
+	   "--fix-cortex-a53-843419=full instead"), abfd, imm);
+      bfd_set_error (bfd_error_bad_value);
+      /* This function is called inside a hashtable traversal and the error
+	 handlers called above turn into non-fatal errors.  Which means this
+	 case ld returns an exit code 0 and also produces a broken object file.
+	 To prevent this, issue a hard abort.  */
+      BFD_FAIL ();
+    }
   return TRUE;
 }
 
@@ -6154,7 +6189,7 @@ static void
 clear_erratum_843419_entry (struct elf_aarch64_link_hash_table *globals,
 			    bfd_vma adrp_offset, asection *input_section)
 {
-  if (globals->fix_erratum_843419)
+  if (globals->fix_erratum_843419 & ERRAT_ADRP)
     {
       struct erratum_843419_branch_to_stub_clear_data data;
       data.adrp_offset = adrp_offset;