arm-gcs: add test for GCS CHKFEAT

Add a new recipes-test layer and GCS test.
The test checks that CHKFEAT reports GCS as enabled.

Signed-off-by: Ross Burton <ross.burton@arm.com>

meta-arm-gcs/gcs.yml

@@ -53,7 +53,7 @@ local_conf_header:
     IMAGE_CLASSES += "testimage"
     TEST_SUITES = "ping ssh gcs"
     IMAGE_FEATURES += "ssh-server-dropbear"
-    CORE_IMAGE_EXTRA_INSTALL += "ssh-pregen-hostkeys binutils kselftest"
+    CORE_IMAGE_EXTRA_INSTALL += "ssh-pregen-hostkeys binutils kselftest gcs-test"
 
 target:
   - core-image-full-cmdline

meta-arm-gcs/lib/oeqa/runtime/cases/gcs.py

@@ -47,6 +47,21 @@ class GCSTests(OERuntimeTestCase):
         self.assertEqual(status, 0, f"ls failed: {output}")
         self.assertEqual(output, "/usr")
 
+    def test_chkfeat(self):
+        """
+        Verify that CHKFEAT reports GCS as enabled when running with the tunables.
+
+        If this fails then GCS is not being properly enabled at runtime glibc. The kernel
+        and glibc patches may be out of sync.
+        """
+        cmd = "GLIBC_TUNABLES=glibc.cpu.aarch64_gcs=1:glibc.cpu.aarch64_gcs_policy=2 gcs-test"
+        status, output = self.target.run(cmd)
+        self.assertEqual(status, 0, f"gcs-test failed: {output}")
+
+        # gcs-test should return 1 if GCS is not enabled via the tunables
+        cmd = "gcs-test"
+        status, output = self.target.run(cmd)
+        self.assertEqual(status, 1, f"gcs-test failed: {output}")
 
     @OEHasPackage(['kselftest'])
     @unittest.expectedFailure

meta-arm-gcs/recipes-test/gcs-test/files/chkfeat.s

@@ -0,0 +1,22 @@
+/* Copyright (C) 2024 Arm Ltd */
+/* SPDX-License-Identifier: MIT */
+
+.global gcs_enabled
+.type gcs_enabled,@function
+gcs_enabled:
+	mov x16, #0x1
+	hint 40
+	eor x0, x16, #0x1
+	ret
+
+.pushsection .note.gnu.property, "a"
+.balign 8
+.long 4
+.long 0x10
+.long 0x5
+.asciz "GNU"
+.long 0xc0000000
+.long 4
+.long 4
+.long 0
+.popsection

meta-arm-gcs/recipes-test/gcs-test/files/gcs_enabled.c

@@ -0,0 +1,9 @@
+// Copyright (C) 2024 Arm Ltd
+// SPDX-License-Identifier: MIT
+
+extern int gcs_enabled(void);
+
+int main(void)
+{
+	return gcs_enabled() ? 0 : 1;
+}

meta-arm-gcs/recipes-test/gcs-test/gcs-test.bb

@@ -0,0 +1,18 @@
+SUMMARY = "test"
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
+
+SRC_URI = "file://chkfeat.s file://gcs_enabled.c"
+
+S = "${WORKDIR}"
+
+LDFLAGS:append = " -z experimental-gcs=always"
+
+do_compile() {
+    ${CC} ${CFLAGS} ${LDFLAGS} ${WORKDIR}/gcs_enabled.c ${WORKDIR}/chkfeat.s -o gcs-test 
+}
+
+do_install() {
+    install -d ${D}${bindir}
+    install -m 0755 gcs-test ${D}${bindir}
+}