Kernel: Move common aarch64 asm functions into kernel folder and NS

Kernel/Arch/aarch64/Aarch64Asm.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2021, James Mintram <me@jamesrm.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Arch/aarch64/Aarch64Registers.h>
+
+namespace Kernel {
+
+[[noreturn]] inline void halt()
+{
+    for (;;) {
+        asm volatile("wfi");
+    }
+}
+
+enum class ExceptionLevel : u8 {
+    EL0 = 0,
+    EL1 = 1,
+    EL2 = 2,
+    EL3 = 3,
+};
+
+inline ExceptionLevel get_current_exception_level()
+{
+    u64 current_exception_level;
+
+    asm("mrs  %[value], CurrentEL"
+        : [value] "=r"(current_exception_level));
+
+    current_exception_level = (current_exception_level >> 2) & 0x3;
+    return static_cast<ExceptionLevel>(current_exception_level);
+}
+
+}