feat(tftf): introduce handler for synchronous exceptions

Introduce a handler for synchronous exceptions (for aarch64) which
currently is treated as unhandled exception.

Also, added the capability to allow registering a custom handler by tftf
framework to allow graceful exit while doing negative tests.

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I4d8d1f5af9951edfe8f068ce85f7d434b2ec070f

1 files changed, 45 insertions, 0 deletions

diff --git a/lib/exceptions/aarch64/sync.c b/lib/exceptions/aarch64/sync.c
new file mode 100644
index 0000000..49b6bd8
--- /dev/null
+++ b/lib/exceptions/aarch64/sync.c
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include <stdbool.h>
+
+#include <arch_helpers.h>
+#include <debug.h>
+#include <sync.h>
+
+static exception_handler_t custom_sync_exception_handler;
+
+void register_custom_sync_exception_handler(exception_handler_t handler)
+{
+	custom_sync_exception_handler = handler;
+}
+
+void unregister_custom_sync_exception_handler(void)
+{
+	custom_sync_exception_handler = NULL;
+}
+
+bool tftf_sync_exception_handler(void)
+{
+	uint64_t elr_elx = IS_IN_EL2() ? read_elr_el2() : read_elr_el1();
+	bool resume = false;
+
+	if (custom_sync_exception_handler == NULL) {
+		return false;
+	}
+
+	resume = custom_sync_exception_handler();
+
+	if (resume) {
+		/* Move ELR to next instruction to allow tftf to continue */
+		if (IS_IN_EL2()) {
+			write_elr_el2(elr_elx + 4U);
+		} else {
+			write_elr_el1(elr_elx + 4U);
+		}
+	}
+
+	return resume;
+}