Added a simple mangle testcase which messes with the ucontext_t
from within the sig_handler, trying to toggle PSTATE SSBS bit.
Expect SIGILL if SSBS feature unsupported or that the value set in
PSTATE.SSBS is preserved on test PASS.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
 .../arm64/signal/testcases/.gitignore         |  1 +
 .../testcases/mangle_pstate_ssbs_regs.c       | 41 +++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 tools/testing/selftests/arm64/signal/testcases/mangle_pstate_ssbs_regs.c

diff --git a/tools/testing/selftests/arm64/signal/testcases/.gitignore b/tools/testing/selftests/arm64/signal/testcases/.gitignore
index e7a1d998b650..c2972c3f33ca 100644
--- a/tools/testing/selftests/arm64/signal/testcases/.gitignore
+++ b/tools/testing/selftests/arm64/signal/testcases/.gitignore

@@ -5,3 +5,4 @@ mangle_pstate_invalid_state_toggle
 mangle_pstate_invalid_mode_el1
 mangle_pstate_invalid_mode_el2
 mangle_pstate_invalid_mode_el3
+mangle_pstate_ssbs_regs

diff --git a/tools/testing/selftests/arm64/signal/testcases/mangle_pstate_ssbs_regs.c b/tools/testing/selftests/arm64/signal/testcases/mangle_pstate_ssbs_regs.c
new file mode 100644
index 000000000000..d997ebf742d9
--- /dev/null
+++ b/tools/testing/selftests/arm64/signal/testcases/mangle_pstate_ssbs_regs.c

@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 ARM Limited */
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+static int mangle_invalid_pstate_ssbs_run(struct tdescr *td,
+					  siginfo_t *si, ucontext_t *uc)
+{
+	ASSERT_GOOD_CONTEXT(uc);
+
+	/* toggle bit value */
+	uc->uc_mcontext.pstate ^= PSR_SSBS_BIT;
+	/* Save after mangling...it should be preserved */
+	td->saved_uc = *uc;
+
+	return 1;
+}
+
+static int pstate_ssbs_bit_checks(struct tdescr *td)
+{
+	uint64_t val = 0;
+
+	get_regval(MRS_SSBS_SYSREG, val);
+	/* pass when preserved */
+	td->pass = (!!(val & MRS_SSBS_BIT) ==
+		    !!(td->saved_uc.uc_mcontext.pstate & PSR_SSBS_BIT));