[BFD, LD, AArch64, 1/3] Add support for GNU PROPERTIES in AArch64 for BTI and PAC

This is part of the patch series to add support for BTI and
PAC in AArch64 linker.

This patch implements the following:
1) This extends in the gnu property support in the linker for
AArch64 by defining backend hooks for elf_backend_setup_gnu_properties,
elf_backend_merge_gnu_properties and elf_backend_parse_gnu_properties.
2) It defines AArch64 specific GNU property
GNU_PROPERTY_AARCH64_FEATURE_1_AND and 2 bit for BTI and PAC in it.
3) It also adds support in readelf.c to read and print these new
GNU properties in AArch64.
All these are made according to the new AArch64 ELF ABI
https://developer.arm.com/docs/ihi0056/latest/elf-for-the-arm-64-bit-architecture-aarch64-abi-2018q4

*** bfd/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>

	* elf-properties.c (_bfd_elf_link_setup_gnu_properties): Exclude
	linker created inputs from merge.
	* elfnn-aarch64.c (struct elf_aarch64_obj_tdata): Add field for
	GNU_PROPERTY_AARCH64_FEATURE_1_AND properties.
	(elfNN_aarch64_link_setup_gnu_properties): New.
	(elfNN_aarch64_merge_gnu_properties): New.
	(elf_backend_setup_gnu_properties): Define for AArch64.
	(elf_backend_merge_gnu_properties): Likewise.
	* elfxx-aarch64.c (_bfd_aarch64_elf_link_setup_gnu_properties): Define.
	(_bfd_aarch64_elf_parse_gnu_properties): Define.
	(_bfd_aarch64_elf_merge_gnu_properties): Define.
	* elfxx-aarch64.h (_bfd_aarch64_elf_link_setup_gnu_properties): Declare.
	(_bfd_aarch64_elf_parse_gnu_properties): Declare.
	(_bfd_aarch64_elf_merge_gnu_properties): Declare.
	(elf_backend_parse_gnu_properties): Define for AArch64.

*** binutils/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>

	* readelf.c (decode_aarch64_feature_1_and): New.
	(print_gnu_property_note): Add case for AArch64 gnu notes.

*** include/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>

	* elf/common.h (GNU_PROPERTY_AARCH64_FEATURE_1_AND): New.
	(GNU_PROPERTY_AARCH64_FEATURE_1_BTI): New.
	(GNU_PROPERTY_AARCH64_FEATURE_1_PAC): New.

*** ld/ChangeLog ***

2019-03-13  Sudakshina Das  <sudi.das@arm.com>

	* NEWS: Document GNU_PROPERTY_AARCH64_FEATURE_1_BTI and
	GNU_PROPERTY_AARCH64_FEATURE_1_PAC.
	* testsuite/ld-aarch64/aarch64-elf.exp: Add run commands for new tests.
	* testsuite/ld-aarch64/property-bti-pac1.d: New test.
	* testsuite/ld-aarch64/property-bti-pac1.s: New test.
	* testsuite/ld-aarch64/property-bti-pac2.d: New test.
	* testsuite/ld-aarch64/property-bti-pac2.s: New test.
	* testsuite/ld-aarch64/property-bti-pac3.d: New test.

1 files changed, 180 insertions, 0 deletions

diff --git a/bfd/elfxx-aarch64.c b/bfd/elfxx-aarch64.c
index 32a9d97..cae94d0 100644
--- a/bfd/elfxx-aarch64.c
+++ b/bfd/elfxx-aarch64.c
@@ -683,3 +683,183 @@ _bfd_aarch64_elf_write_core_note (bfd *abfd, char *buf, int *bufsiz, int note_ty
       }
     }
 }
+
+/* Find the first input bfd with GNU property and merge it with GPROP.  If no
+   such input is found, add it to a new section at the last input.  Update
+   GPROP accordingly.  */
+bfd *
+_bfd_aarch64_elf_link_setup_gnu_properties (struct bfd_link_info *info,
+					    uint32_t *gprop)
+{
+  asection *sec;
+  bfd *pbfd;
+  bfd *ebfd = NULL;
+  elf_property *prop;
+
+  uint32_t gnu_prop = *gprop;
+
+  /* Find a normal input file with GNU property note.  */
+  for (pbfd = info->input_bfds;
+       pbfd != NULL;
+       pbfd = pbfd->link.next)
+    if (bfd_get_flavour (pbfd) == bfd_target_elf_flavour
+	&& bfd_count_sections (pbfd) != 0)
+      {
+	ebfd = pbfd;
+
+	if (elf_properties (pbfd) != NULL)
+	  break;
+      }
+
+  /* If ebfd != NULL it is either an input with property note or the last
+     input.  Either way if we have gnu_prop, we should add it (by creating
+     a section if needed).  */
+  if (ebfd != NULL && gnu_prop)
+    {
+      prop = _bfd_elf_get_property (ebfd,
+				    GNU_PROPERTY_AARCH64_FEATURE_1_AND,
+				    4);
+      prop->u.number |= gnu_prop;
+      prop->pr_kind = property_number;
+
+      /* pbfd being NULL implies ebfd is the last input.  Create the GNU
+	 property note section.  */
+      if (pbfd == NULL)
+	{
+	  sec = bfd_make_section_with_flags (ebfd,
+					     NOTE_GNU_PROPERTY_SECTION_NAME,
+					     (SEC_ALLOC
+					      | SEC_LOAD
+					      | SEC_IN_MEMORY
+					      | SEC_READONLY
+					      | SEC_HAS_CONTENTS
+					      | SEC_DATA));
+	  if (sec == NULL)
+	    info->callbacks->einfo (
+	      _("%F%P: failed to create GNU property section\n"));
+
+	  elf_section_type (sec) = SHT_NOTE;
+	}
+    }
+
+  pbfd = _bfd_elf_link_setup_gnu_properties (info);
+
+  if (bfd_link_relocatable (info))
+    return pbfd;
+
+  /* If pbfd has any GNU_PROPERTY_AARCH64_FEATURE_1_AND properties, update
+     gnu_prop accordingly.  */
+  if (pbfd != NULL)
+    {
+      elf_property_list *p;
+
+      /* The property list is sorted in order of type.  */
+      for (p = elf_properties (pbfd); p; p = p->next)
+	{
+	  /* Check for all GNU_PROPERTY_AARCH64_FEATURE_1_AND.  */
+	  if (GNU_PROPERTY_AARCH64_FEATURE_1_AND == p->property.pr_type)
+	    {
+	      gnu_prop = (p->property.u.number
+			  & (GNU_PROPERTY_AARCH64_FEATURE_1_PAC
+			      | GNU_PROPERTY_AARCH64_FEATURE_1_BTI));
+	      break;
+	    }
+	  else if (GNU_PROPERTY_AARCH64_FEATURE_1_AND < p->property.pr_type)
+	    break;
+	}
+    }
+  *gprop = gnu_prop;
+  return pbfd;
+}
+
+/* Define elf_backend_parse_gnu_properties for AArch64.  */
+enum elf_property_kind
+_bfd_aarch64_elf_parse_gnu_properties (bfd *abfd, unsigned int type,
+				       bfd_byte *ptr, unsigned int datasz)
+{
+  elf_property *prop;
+
+  switch (type)
+    {
+    case GNU_PROPERTY_AARCH64_FEATURE_1_AND:
+      if (datasz != 4)
+	{
+	  _bfd_error_handler
+	    ( _("error: %pB: <corrupt AArch64 used size: 0x%x>"),
+	     abfd, datasz);
+	  return property_corrupt;
+	}
+      prop = _bfd_elf_get_property (abfd, type, datasz);
+      /* Combine properties of the same type.  */
+      prop->u.number |= bfd_h_get_32 (abfd, ptr);
+      prop->pr_kind = property_number;
+      break;
+
+    default:
+      return property_ignored;
+    }
+
+  return property_number;
+}
+
+/* Merge AArch64 GNU property BPROP with APROP also accounting for PROP.
+   If APROP isn't NULL, merge it with BPROP and/or PROP.  Vice-versa if BROP
+   isn't NULL.  Return TRUE if there is any update to APROP or if BPROP should
+   be merge with ABFD.  */
+bfd_boolean
+_bfd_aarch64_elf_merge_gnu_properties (struct bfd_link_info *info
+				       ATTRIBUTE_UNUSED,
+				       bfd *abfd ATTRIBUTE_UNUSED,
+				       elf_property *aprop,
+				       elf_property *bprop,
+				       uint32_t prop)
+{
+  unsigned int orig_number;
+  bfd_boolean updated = FALSE;
+  unsigned int pr_type = aprop != NULL ? aprop->pr_type : bprop->pr_type;
+
+  switch (pr_type)
+    {
+    case GNU_PROPERTY_AARCH64_FEATURE_1_AND:
+      {
+	if (aprop != NULL && bprop != NULL)
+	  {
+	    orig_number = aprop->u.number;
+	    aprop->u.number = (orig_number & bprop->u.number) | prop;
+	    updated = orig_number != aprop->u.number;
+	    /* Remove the property if all feature bits are cleared.  */
+	    if (aprop->u.number == 0)
+	      aprop->pr_kind = property_remove;
+	    break;
+	  }
+	/* If either is NULL, the AND would be 0 so, if there is
+	   any PROP, asign it to the input that is not NULL.  */
+	if (prop)
+	  {
+	    if (aprop != NULL)
+	      {
+		orig_number = aprop->u.number;
+		aprop->u.number = prop;
+		updated = orig_number != aprop->u.number;
+	      }
+	    else
+	      {
+		bprop->u.number = prop;
+		updated = TRUE;
+	      }
+	  }
+	/* No PROP and BPROP is NULL, so remove APROP.  */
+	else if (aprop != NULL)
+	  {
+	    aprop->pr_kind = property_remove;
+	    updated = TRUE;
+	  }
+      }
+      break;
+
+    default:
+      abort ();
+    }
+
+  return updated;
+}