aarch64: Add support for GCS in AArch64 linker.users/ARM/gcs-binutils-gdb-master

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

1 files changed, 4 insertions, 0 deletions

diff --git a/binutils/readelf.c b/binutils/readelf.c
index e3bf680..bcef2be 100644
--- a/binutils/readelf.c
+++ b/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;