aarch64: Add support for GCS in AArch64 linker.

This patch adds support for GCS in AArch64 linker.

This patch implements the following:
1) Defines GNU_PROPERTY_AARCH64_FEATURE_1_GCS bit for GCS in
GNU_PROPERTY_AARCH64_FEATURE_1_AND macro.

2) Adds readelf support to read and print the GNU properties
in AArch64.

Displaying notes found in: .note.gnu.property
[      ]+Owner[        ]+Data size[    ]+Description
  GNU                  0x00000010      NT_GNU_PROPERTY_TYPE_0
      Properties: AArch64 feature: GCS

3) Adds support for -z experimental-gcs linker option and document
all the values allowed with option (-z experimental-gcs[=always|never|implicit]).
-z experimental-gcs is equivalent to -z experimental-gcs=always and
when option is not passed in the command line, it defaults to implicit.

4) Adds support for -z experimental-gcs-report linker option and document
all the values allowed with this option (-z experimental-gcs-report[=none|warning|error]).
-z experimental-gcs-report is equivalent to -z experimental-gcs-report=none
and when option is not passed in the command line, it defaults to none.

The ABI changes adding GNU_PROPERTY_AARCH64_FEATURE_1_GCS to the
GNU property GNU_PROPERTY_AARCH64_FEATURE_1_AND is merged into main and
can be found below.
https://github.com/ARM-software/abi-aa/blob/main/sysvabi64/sysvabi64.rst

bfd/elfnn-aarch64.c

@@ -2546,6 +2546,12 @@ struct elf_aarch64_obj_tdata
      GNU_PROPERTY_AARCH64_FEATURE_1_BTI.  */
   int no_bti_warn;
 
+  /* Mark ouput with GCS based on -z experimental-gcs.  */
+  aarch64_gcs_type gcs_type;
+  /* Report linker warning/error for -z experimental-gcs-report based on
+     -z experimental-gcs.  */
+  aarch64_gcs_report gcs_report;
+
   /* PLT type based on security.  */
   aarch64_plt_type plt_type;
 };
@@ -5011,7 +5017,7 @@ bfd_elfNN_aarch64_set_options (struct bfd *output_bfd,
 			       int fix_erratum_835769,
 			       erratum_84319_opts fix_erratum_843419,
 			       int no_apply_dynamic_relocs,
-			       aarch64_bti_pac_info bp_info)
+			       aarch64_gnu_prop_info bp_info)
 {
   struct elf_aarch64_link_hash_table *globals;
 
@@ -5039,6 +5045,24 @@ bfd_elfNN_aarch64_set_options (struct bfd *output_bfd,
     default:
       break;
     }
+
+  switch (bp_info.gcs_type)
+    {
+    case GCS_ALWAYS:
+      elf_aarch64_tdata (output_bfd)->gnu_and_prop
+	|= GNU_PROPERTY_AARCH64_FEATURE_1_GCS;
+      break;
+    case GCS_NEVER:
+      elf_aarch64_tdata (output_bfd)->gnu_and_prop
+	&= ~GNU_PROPERTY_AARCH64_FEATURE_1_GCS;
+      break;
+
+    default:
+      break;
+    }
+
+  elf_aarch64_tdata (output_bfd)->gcs_type = bp_info.gcs_type;
+  elf_aarch64_tdata (output_bfd)->gcs_report = bp_info.gcs_report;
   elf_aarch64_tdata (output_bfd)->plt_type = bp_info.plt_type;
   setup_plt_values (link_info, bp_info.plt_type);
 }
@@ -10196,7 +10220,12 @@ static bfd *
 elfNN_aarch64_link_setup_gnu_properties (struct bfd_link_info *info)
 {
   uint32_t prop = elf_aarch64_tdata (info->output_bfd)->gnu_and_prop;
-  bfd *pbfd = _bfd_aarch64_elf_link_setup_gnu_properties (info, &prop);
+  aarch64_gcs_report gcs_report
+    = elf_aarch64_tdata (info->output_bfd)->gcs_report;
+  aarch64_gcs_report gcs_type
+    = elf_aarch64_tdata (info->output_bfd)->gcs_type;
+  bfd *pbfd = _bfd_aarch64_elf_link_setup_gnu_properties (info, &prop,
+							  gcs_report, gcs_type);
   elf_aarch64_tdata (info->output_bfd)->gnu_and_prop = prop;
   elf_aarch64_tdata (info->output_bfd)->plt_type
     |= (prop & GNU_PROPERTY_AARCH64_FEATURE_1_BTI) ? PLT_BTI : 0;
@@ -10215,30 +10244,54 @@ elfNN_aarch64_merge_gnu_properties (struct bfd_link_info *info,
 {
   uint32_t prop
     = elf_aarch64_tdata (info->output_bfd)->gnu_and_prop;
+  aarch64_gcs_report gcs_report
+    = elf_aarch64_tdata (info->output_bfd)->gcs_report;
+  aarch64_gcs_type gcs_type
+    = elf_aarch64_tdata (info->output_bfd)->gcs_type;
 
-  /* If output has been marked with BTI using command line argument, give out
-     warning if necessary.  */
   /* Properties are merged per type, hence only check for warnings when merging
      GNU_PROPERTY_AARCH64_FEATURE_1_AND.  */
-  if (((aprop && aprop->pr_type == GNU_PROPERTY_AARCH64_FEATURE_1_AND)
+  if ((aprop && aprop->pr_type == GNU_PROPERTY_AARCH64_FEATURE_1_AND)
 	|| (bprop && bprop->pr_type == GNU_PROPERTY_AARCH64_FEATURE_1_AND))
-      && (prop & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)
-      && (!elf_aarch64_tdata (info->output_bfd)->no_bti_warn))
     {
-      if ((aprop && !(aprop->u.number & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
+      /* If output has been marked with BTI using command line argument, give
-	   || !aprop)
+	 out warning if necessary.  */
+      if ((prop & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)
+	  && (!elf_aarch64_tdata (info->output_bfd)->no_bti_warn))
 	{
-	  _bfd_error_handler (_("%pB: warning: BTI turned on by -z force-bti when "
+	  if ((aprop && !(aprop->u.number & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
-				"all inputs do not have BTI in NOTE section."),
+	      || !aprop)
-			      abfd);
+	    {
+	      _bfd_error_handler (_("%pB: warning: BTI turned on by -z "
+				  "force-bti when all inputs do not have BTI "
+				  "in NOTE section."), abfd);
+	    }
+	  if ((bprop && !(bprop->u.number & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
+	      || !bprop)
+	    {
+	      _bfd_error_handler (_("%pB: warning: BTI turned on by -z "
+				  "force-bti when all inputs do not have BTI "
+				  "in NOTE section."), bbfd);
+	    }
 	}
-      if ((bprop && !(bprop->u.number & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
+
-	   || !bprop)
+      /* If output has been marked with GCS using -z experimental-gcs and input
+	 is missing GCS marking throw warning/error on
+	 -z experimental-gcs-report=warning/error.  */
+      if ((prop & GNU_PROPERTY_AARCH64_FEATURE_1_GCS) && gcs_report != GCS_NONE)
 	{
-	  _bfd_error_handler (_("%pB: warning: BTI turned on by -z force-bti when "
+	  if ((aprop && !(aprop->u.number & GNU_PROPERTY_AARCH64_FEATURE_1_GCS))
-				"all inputs do not have BTI in NOTE section."),
+	      || !aprop)
-			      bbfd);
+	    _bfd_aarch64_elf_check_gcs_report (gcs_report, abfd);
+	  if ((bprop && !(bprop->u.number & GNU_PROPERTY_AARCH64_FEATURE_1_GCS))
+	      || !bprop)
+	    _bfd_aarch64_elf_check_gcs_report (gcs_report, bbfd);
 	}
+
+      if (gcs_type == GCS_NEVER && aprop != NULL)
+	aprop->u.number &= ~GNU_PROPERTY_AARCH64_FEATURE_1_GCS;
+      if (gcs_type == GCS_NEVER && bprop != NULL)
+	bprop->u.number &= ~GNU_PROPERTY_AARCH64_FEATURE_1_GCS;
     }
 
   return  _bfd_aarch64_elf_merge_gnu_properties (info, abfd, aprop,

bfd/elfxx-aarch64.c

@@ -702,7 +702,9 @@ _bfd_aarch64_elf_write_core_note (bfd *abfd, char *buf, int *bufsiz, int note_ty
    GPROP accordingly.  */
 bfd *
 _bfd_aarch64_elf_link_setup_gnu_properties (struct bfd_link_info *info,
-					    uint32_t *gprop)
+					    uint32_t *gprop,
+					    aarch64_gcs_report gcs_report,
+					    aarch64_gcs_type gcs_type)
 {
   asection *sec;
   bfd *pbfd;
@@ -738,6 +740,11 @@ _bfd_aarch64_elf_link_setup_gnu_properties (struct bfd_link_info *info,
 	    _bfd_error_handler (_("%pB: warning: BTI turned on by -z force-bti "
 				  "when all inputs do not have BTI in NOTE "
 				  "section."), ebfd);
+
+      if ((gnu_prop & GNU_PROPERTY_AARCH64_FEATURE_1_GCS)
+	  && !(prop->u.number & GNU_PROPERTY_AARCH64_FEATURE_1_GCS))
+	_bfd_aarch64_elf_check_gcs_report (gcs_report, ebfd);
+
       prop->u.number |= gnu_prop;
       prop->pr_kind = property_number;
 
@@ -765,6 +772,14 @@ _bfd_aarch64_elf_link_setup_gnu_properties (struct bfd_link_info *info,
 	  elf_section_type (sec) = SHT_NOTE;
 	}
     }
+  else if (ebfd != NULL && gcs_type == GCS_NEVER)
+    {
+      prop = _bfd_elf_get_property (ebfd, GNU_PROPERTY_AARCH64_FEATURE_1_AND,
+				    4);
+      prop->u.number &= ~GNU_PROPERTY_AARCH64_FEATURE_1_GCS;
+      if (prop->u.number == 0)
+	prop->pr_kind = property_remove;
+    }
 
   pbfd = _bfd_elf_link_setup_gnu_properties (info);
 
@@ -785,7 +800,8 @@ _bfd_aarch64_elf_link_setup_gnu_properties (struct bfd_link_info *info,
 	    {
 	      gnu_prop = (p->property.u.number
 			  & (GNU_PROPERTY_AARCH64_FEATURE_1_PAC
-			      | GNU_PROPERTY_AARCH64_FEATURE_1_BTI));
+			      | GNU_PROPERTY_AARCH64_FEATURE_1_BTI
+			      | GNU_PROPERTY_AARCH64_FEATURE_1_GCS));
 	      break;
 	    }
 	  else if (GNU_PROPERTY_AARCH64_FEATURE_1_AND < p->property.pr_type)
@@ -922,3 +938,20 @@ _bfd_aarch64_elf_link_fixup_gnu_properties
 	}
     }
 }
+
+/* Check AArch64 GCS report.  */
+void
+_bfd_aarch64_elf_check_gcs_report (aarch64_gcs_report gcs_report, bfd *ebfd)
+{
+  if (gcs_report == GCS_WARN)
+    _bfd_error_handler (_("%pB: warning: GCS turned on by -z experimental-gcs "
+			"on the output when all inputs do not have GCS in NOTE "
+			"section."), ebfd);
+  else if (gcs_report == GCS_ERROR)
+    {
+      _bfd_error_handler (_("%pB: error: GCS turned on by -z experimental-gcs "
+			  "on the output when all inputs do not have GCS in "
+			  "NOTE section."), ebfd);
+      _exit (EXIT_FAILURE);
+    }
+}

bfd/elfxx-aarch64.h

@@ -46,6 +46,27 @@ typedef enum
   BTI_WARN	= 1,  /* BTI is enabled with -z force-bti.  */
 } aarch64_enable_bti_type;
 
+/* To indicate whether GNU_PROPERTY_AARCH64_FEATURE_1_GCS bit is
+   enabled/disabled on the output when -z experimental-gcs linker
+   command line option is passed.  */
+typedef enum
+{
+  GCS_NEVER	= 0,  /* gcs is disabled on output.  */
+  GCS_IMPLICIT  = 1,  /* gcs is deduced from input object.  */
+  GCS_ALWAYS	= 2,  /* gsc is enabled on output.  */
+} aarch64_gcs_type;
+
+/* To indicate whether to generate linker warning/errors for
+   -z experimental-gcs-report when -z experimental-gcs=always is passed.  */
+typedef enum
+{
+  GCS_NONE	= 0,  /* Does not emit any warning/error messages.  */
+  GCS_WARN	= 1,  /* Emit warning when the input objects are missing gcs
+			 markings and output have gcs marking.  */
+  GCS_ERROR	= 2,  /* Emit error when the input objects are missing gcs
+			 markings and output have gcs marking.  */
+} aarch64_gcs_report;
+
 /* A structure to encompass all information coming from BTI or PAC
    related command line options.  This involves the "PLT_TYPE" to determine
    which version of PLTs to pick and "BTI_TYPE" to determine if
@@ -54,7 +75,9 @@ typedef struct
 {
   aarch64_plt_type plt_type;
   aarch64_enable_bti_type bti_type;
-} aarch64_bti_pac_info;
+  aarch64_gcs_type gcs_type;
+  aarch64_gcs_report gcs_report;
+} aarch64_gnu_prop_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.  */
@@ -67,11 +90,11 @@ typedef enum
 
 extern void bfd_elf64_aarch64_set_options
   (bfd *, struct bfd_link_info *, int, int, int, int, erratum_84319_opts, int,
-   aarch64_bti_pac_info);
+   aarch64_gnu_prop_info);
 
 extern void bfd_elf32_aarch64_set_options
   (bfd *, struct bfd_link_info *, int, int, int, int, erratum_84319_opts, int,
-   aarch64_bti_pac_info);
+   aarch64_gnu_prop_info);
 
 /* AArch64 stub generation support for ELF64.  Called from the linker.  */
 extern int elf64_aarch64_setup_section_lists
@@ -135,8 +158,9 @@ _bfd_aarch64_elf_write_core_note (bfd *, char *, int *, int, ...);
 #define elf_backend_write_core_note	_bfd_aarch64_elf_write_core_note
 
 extern bfd *
-_bfd_aarch64_elf_link_setup_gnu_properties (struct bfd_link_info *,
+_bfd_aarch64_elf_link_setup_gnu_properties (struct bfd_link_info *, uint32_t *,
-					    uint32_t *);
+					    aarch64_gcs_report,
+					    aarch64_gcs_type);
 
 extern enum elf_property_kind
 _bfd_aarch64_elf_parse_gnu_properties (bfd *, unsigned int,
@@ -146,6 +170,8 @@ extern bool
 _bfd_aarch64_elf_merge_gnu_properties (struct bfd_link_info *, bfd *,
 				       elf_property *, elf_property *,
 				       uint32_t);
+extern void
+_bfd_aarch64_elf_check_gcs_report (aarch64_gcs_report, bfd *);
 
 extern void
 _bfd_aarch64_elf_link_fixup_gnu_properties (struct bfd_link_info *,

binutils/readelf.c

@@ -20638,6 +20638,10 @@ decode_aarch64_feature_1_and (unsigned int bitmask)
 	  printf ("PAC");
 	  break;
 
+	case GNU_PROPERTY_AARCH64_FEATURE_1_GCS:
+	  printf ("GCS");
+	  break;
+
 	default:
 	  printf (_("<unknown: %x>"), bit);
 	  break;

include/elf/common.h

@@ -1001,6 +1001,7 @@
 
 #define GNU_PROPERTY_AARCH64_FEATURE_1_BTI	(1U << 0)
 #define GNU_PROPERTY_AARCH64_FEATURE_1_PAC	(1U << 1)
+#define GNU_PROPERTY_AARCH64_FEATURE_1_GCS	(1U << 2)
 
 /* Values used in GNU .note.ABI-tag notes (NT_GNU_ABI_TAG).  */
 #define GNU_ABI_TAG_LINUX	0

ld/emultempl/aarch64elf.em

@@ -36,6 +36,12 @@ static erratum_84319_opts fix_erratum_843419 = ERRAT_NONE;
 static int no_apply_dynamic_relocs = 0;
 static aarch64_plt_type plt_type = PLT_NORMAL;
 static aarch64_enable_bti_type bti_type = BTI_NONE;
+static aarch64_gcs_type gcs_type = GCS_IMPLICIT;
+static aarch64_gcs_report gcs_report = GCS_NONE;
+static const char * egr = "experimental-gcs-report";
+static const char * eg = "experimental-gcs";
+#define EGR_LEN strlen (egr)
+#define EG_LEN strlen (eg)
 
 static void
 gld${EMULATION_NAME}_before_parse (void)
@@ -321,9 +327,11 @@ aarch64_elf_create_output_section_statements (void)
       return;
     }
 
-  aarch64_bti_pac_info bp_info;
+  aarch64_gnu_prop_info bp_info;
   bp_info.plt_type = plt_type;
   bp_info.bti_type = bti_type;
+  bp_info.gcs_type = gcs_type;
+  bp_info.gcs_report = gcs_report;
 
   bfd_elf${ELFSIZE}_aarch64_set_options (link_info.output_bfd, &link_info,
 				 no_enum_size_warning,
@@ -398,6 +406,19 @@ PARSE_AND_LIST_OPTIONS='
   fprintf (file, _("  --no-apply-dynamic-relocs    Do not apply link-time values for dynamic relocations\n"));
   fprintf (file, _("  -z force-bti                  Turn on Branch Target Identification mechanism and generate PLTs with BTI. Generate warnings for missing BTI on inputs\n"));
   fprintf (file, _("  -z pac-plt                    Protect PLTs with Pointer Authentication.\n"));
+  fprintf (file, _("\
+  -z experimental-gcs[=always|never|implicit]		Turn on Guarded Control Stack(gcs) mechanism on the output.\n\
+							implicit(default): deduce gcs from input objects.\n\
+							always: always marks the output with gcs.\n\
+							never: never marks the output with gcs.\n"));
+  fprintf (file, _("\
+  -z experimental-gcs-report[=none|warning|error]	Emit warning/error on mismatch of gcs marking between input objects and ouput.\n\
+							none (default): Does not emit any warning/error messages.\n\
+							warning: Emit warning when the input objects are missing gcs markings\n\
+								 and output have gcs marking.\n\
+							error: Emit error when the input objects are missing gcs markings\n\
+							       and output have gcs marking.\n"));
+
 '
 
 PARSE_AND_LIST_ARGS_CASE_Z_AARCH64='
@@ -408,6 +429,28 @@ PARSE_AND_LIST_ARGS_CASE_Z_AARCH64='
 	}
       else if (strcmp (optarg, "pac-plt") == 0)
 	plt_type |= PLT_PAC;
+     else if (strncmp (optarg, egr, EGR_LEN) == 0)
+	{
+	  if (strlen (optarg) == EGR_LEN || strcmp (optarg + EGR_LEN, "=none") == 0)
+	    gcs_report = GCS_NONE;
+	  else if (strcmp (optarg + EGR_LEN, "=warning") == 0)
+	    gcs_report = GCS_WARN;
+	  else if (strcmp (optarg + EGR_LEN, "=error") == 0)
+	    gcs_report = GCS_ERROR;
+	  else
+	    einfo (_("%P: error: unrecognized: `%s'\''\n"), optarg);
+	}
+     else if (strncmp (optarg, eg, EG_LEN) == 0)
+	{
+	  if (strlen (optarg) == EG_LEN || strcmp (optarg + EG_LEN, "=always") == 0)
+	    gcs_type = GCS_ALWAYS;
+	  else if (strcmp (optarg + EG_LEN, "=never") == 0)
+	    gcs_type = GCS_NEVER;
+	  else if (strcmp (optarg + EG_LEN, "=implicit") == 0)
+	    gcs_type = GCS_IMPLICIT;
+	  else
+	    einfo (_("%P: error: unrecognized: `%s'\''\n"), optarg);
+	}
 '
 PARSE_AND_LIST_ARGS_CASE_Z="$PARSE_AND_LIST_ARGS_CASE_Z $PARSE_AND_LIST_ARGS_CASE_Z_AARCH64"
 

ld/testsuite/ld-aarch64/aarch64-elf.exp

@@ -471,3 +471,26 @@ run_dump_test_lp64 "bti-far-3"
 if { ![skip_sframe_tests] } {
   run_dump_test "sframe-simple-1"
 }
+
+run_dump_test "property-gcs1"
+run_dump_test "property-gcs2"
+run_dump_test "property-gcs3"
+run_dump_test "property-gcs4"
+run_dump_test "property-gcs5"
+run_dump_test "property-gcs6"
+run_dump_test "property-gcs7"
+run_dump_test "property-gcs8"
+run_dump_test "property-gcs9"
+run_dump_test "property-gcs10"
+run_dump_test "property-gcs11"
+run_dump_test "property-gcs12"
+run_dump_test "property-gcs13"
+run_dump_test "property-gcs14"
+run_dump_test "property-gcs15"
+run_dump_test "property-gcs16"
+run_dump_test "property-gcs17"
+run_dump_test "property-gcs18"
+run_dump_test "property-gcs19"
+run_dump_test "property-gcs20"
+run_dump_test "property-gcs21"
+run_dump_test "property-gcs22"

ld/testsuite/ld-aarch64/property-bti-pac1.d

@@ -8,4 +8,4 @@
 Displaying notes found in: .note.gnu.property
 [ 	]+Owner[ 	]+Data size[ 	]+Description
   GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
-      Properties: AArch64 feature: BTI, PAC
+      Properties: AArch64 feature: BTI, PAC, GCS

ld/testsuite/ld-aarch64/property-bti-pac1.s

@@ -12,6 +12,20 @@ _start:
 	.long 5f - 2f		/* data length */
 	.long 5			/* note type */
 0:	.asciz "GNU"		/* vendor name */
+1:
+	.p2align 3
+2:	.long 0xc0000000	/* pr_type.  */
+	.long 4f - 3f		/* pr_datasz.  */
+3:
+	.long 0x4		/* GCS.  */
+4:
+	.p2align 3
+5:
+	.p2align 3
+	.long 1f - 0f		/* name length */
+	.long 5f - 2f		/* data length */
+	.long 5			/* note type */
+0:	.asciz "GNU"		/* vendor name */
 1:
 	.p2align 3
 2:	.long 0xc0000000	/* pr_type.  */

ld/testsuite/ld-aarch64/property-gcs.s

@@ -0,0 +1,25 @@
+	.text
+	.globl _start
+	.type _start,@function
+_start:
+	mov x1, #2
+.ifndef __mult__
+	bl foo
+.endif
+.ifdef __property_gcs__
+	.section ".note.gnu.property", "a"
+	.p2align 3
+	.long 1f - 0f		/* name length */
+	.long 5f - 2f		/* data length */
+	.long 5			/* note type */
+0:	.asciz "GNU"		/* vendor name */
+1:
+	.p2align 3
+2:	.long 0xc0000000	/* pr_type.  */
+	.long 4f - 3f		/* pr_datasz.  */
+3:
+	.long 0x4		/* GCS.  */
+4:
+	.p2align 3
+5:
+.endif

ld/testsuite/ld-aarch64/property-gcs1.d

@@ -0,0 +1,6 @@
+#name: GNU Property (input without gcs)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -shared
+#readelf: -n

ld/testsuite/ld-aarch64/property-gcs10.d

@@ -0,0 +1,6 @@
+#name: GNU Property (input without gcs ouput forced with experimental-gcs=always experimental-gcs-report=error)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs=always -z experimental-gcs-report=error
+#error: .*property-gcs.*: error: GCS turned on by -z experimental-gcs on the output when all inputs do not have GCS in NOTE section.

ld/testsuite/ld-aarch64/property-gcs11.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs output forced with experimental-gcs)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs12.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs ouput forced with experimental-gcs=always)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs=always
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs13.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs ouput forced with experimental-gcs experimental-gcs-report=none)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs -z experimental-gcs-report=none
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs14.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs ouput forced with experimental-gcs experimental-gcs-report=warning)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs -z experimental-gcs-report=warning
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs15.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs ouput forced with experimental-gcs experimental-gcs-report=error)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs -z experimental-gcs-report=error
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs16.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs ouput forced with experimental-gcs=always experimental-gcs-report=none)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs=always -z experimental-gcs-report=none
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs17.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs ouput forced with experimental-gcs=always experimental-gcs-report=warning)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs=always -z experimental-gcs-report=warning
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs18.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs ouput forced with experimental-gcs=always experimental-gcs-report=error)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs=always -z experimental-gcs-report=error
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs19.d

@@ -0,0 +1,6 @@
+#name: GNU Property (input without gcs output forced with experimental-gcs=never)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs=never
+#readelf: -n

ld/testsuite/ld-aarch64/property-gcs2.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -shared
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs2.s

@@ -0,0 +1,33 @@
+	.text
+	.global	foo
+	.type	foo, %function
+foo:
+	sub	sp, sp, #16
+	mov	w0, 9
+	str	w0, [sp, 12]
+	ldr	w0, [sp, 12]
+	add	w0, w0, 4
+	str	w0, [sp, 12]
+	nop
+	add	sp, sp, 16
+	ret
+	.size	foo, .-foo
+	.global	bar
+	.type	bar, %function
+.ifdef __property_gcs__
+	.section ".note.gnu.property", "a"
+	.p2align 3
+	.long 1f - 0f		/* name length */
+	.long 5f - 2f		/* data length */
+	.long 5			/* note type */
+0:	.asciz "GNU"		/* vendor name */
+1:
+	.p2align 3
+2:	.long 0xc0000000	/* pr_type.  */
+	.long 4f - 3f		/* pr_datasz.  */
+3:
+	.long 0x4		/* GCS.  */
+4:
+	.p2align 3
+5:
+.endif

ld/testsuite/ld-aarch64/property-gcs20.d

@@ -0,0 +1,6 @@
+#name: GNU Property (input without gcs output forced with experimental-gcs=implicit)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs=implicit
+#readelf: -n

ld/testsuite/ld-aarch64/property-gcs21.d

@@ -0,0 +1,6 @@
+#name: GNU Property (input with gcs output forced with experimental-gcs=never)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs=never
+#readelf: -n

ld/testsuite/ld-aarch64/property-gcs22.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input with gcs output forced with experimental-gcs=implicit)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0 -defsym __property_gcs__=1
+#ld: -z experimental-gcs=implicit
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs3.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input without gcs output forced with experimental-gcs)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs4.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input without gcs ouput forced with experimental-gcs=always)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs=always
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs5.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input without gcs ouput forced with experimental-gcs experimental-gcs-report=none)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs -z experimental-gcs-report=none
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs6.d

@@ -0,0 +1,12 @@
+#name: GNU Property (input without gcs ouput forced with experimental-gcs experimental-gcs-report=warning)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs -z experimental-gcs-report=warning
+#readelf: -n
+#warning: .*property-gcs.*: warning: GCS turned on by -z experimental-gcs on the output when all inputs do not have GCS in NOTE section.
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs7.d

@@ -0,0 +1,6 @@
+#name: GNU Property (input without gcs ouput forced with experimental-gcs experimental-gcs-report=error)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs -z experimental-gcs-report=error
+#error: .*property-gcs.*: error: GCS turned on by -z experimental-gcs on the output when all inputs do not have GCS in NOTE section.

ld/testsuite/ld-aarch64/property-gcs8.d

@@ -0,0 +1,11 @@
+#name: GNU Property (input without gcs ouput forced with experimental-gcs=always experimental-gcs-report=none)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs=always -z experimental-gcs-report=none
+#readelf: -n
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS

ld/testsuite/ld-aarch64/property-gcs9.d

@@ -0,0 +1,12 @@
+#name: GNU Property (input without gcs ouput forced with experimental-gcs=always experimental-gcs-report=warning)
+#source: property-gcs.s
+#alltargets: [check_shared_lib_support] *linux*
+#as: -march=armv9.4-a+gcs -defsym __mult__=0
+#ld: -z experimental-gcs=always -z experimental-gcs-report=warning
+#readelf: -n
+#warning: .*property-gcs.*: warning: GCS turned on by -z experimental-gcs on the output when all inputs do not have GCS in NOTE section.
+
+Displaying notes found in: .note.gnu.property
+[ 	]+Owner[ 	]+Data size[ 	]+Description
+  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
+      Properties: AArch64 feature: GCS