refactor(spm-mm): reorganize secure partition manager shim code

In preparation for adding the support for SEL0 SP in EL3 SPMC,
restructure the existing SPM_MM shim code in a way that allows reuse
of the code for both SPM_MM interface and FF-A EL3 SPMC interface. The
code for changing exception levels is identical for both.

With this restructuring of the code, the shim exception code is moved to
the common sub-directory.

Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Signed-off-by: Nishant Sharma <nishant.sharma@arm.com>
Change-Id: Iadda9cf73f12b56e6a1d31fc21b5ba5dc355867f
diff --git a/services/std_svc/spm/common/aarch64/spm_shim_exceptions.S b/services/std_svc/spm/common/aarch64/spm_shim_exceptions.S
new file mode 100644
index 0000000..836f75c
--- /dev/null
+++ b/services/std_svc/spm/common/aarch64/spm_shim_exceptions.S
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2017-2022, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch.h>
+#include <asm_macros.S>
+#include <common/bl_common.h>
+#include <context.h>
+
+/* -----------------------------------------------------------------------------
+ * Very simple stackless exception handlers used by the spm shim layer.
+ * -----------------------------------------------------------------------------
+ */
+	.globl	spm_shim_exceptions_ptr
+
+vector_base spm_shim_exceptions_ptr, .spm_shim_exceptions
+
+	/* -----------------------------------------------------
+	 * Current EL with SP0 : 0x0 - 0x200
+	 * -----------------------------------------------------
+	 */
+vector_entry SynchronousExceptionSP0, .spm_shim_exceptions
+	b	.
+end_vector_entry SynchronousExceptionSP0
+
+vector_entry IrqSP0, .spm_shim_exceptions
+	b	.
+end_vector_entry IrqSP0
+
+vector_entry FiqSP0, .spm_shim_exceptions
+	b	.
+end_vector_entry FiqSP0
+
+vector_entry SErrorSP0, .spm_shim_exceptions
+	b	.
+end_vector_entry SErrorSP0
+
+	/* -----------------------------------------------------
+	 * Current EL with SPx: 0x200 - 0x400
+	 * -----------------------------------------------------
+	 */
+vector_entry SynchronousExceptionSPx, .spm_shim_exceptions
+	b	.
+end_vector_entry SynchronousExceptionSPx
+
+vector_entry IrqSPx, .spm_shim_exceptions
+	b	.
+end_vector_entry IrqSPx
+
+vector_entry FiqSPx, .spm_shim_exceptions
+	b	.
+end_vector_entry FiqSPx
+
+vector_entry SErrorSPx, .spm_shim_exceptions
+	b	.
+end_vector_entry SErrorSPx
+
+	/* -----------------------------------------------------
+	 * Lower EL using AArch64 : 0x400 - 0x600. No exceptions
+	 * are handled since secure_partition does not implement
+	 * a lower EL
+	 * -----------------------------------------------------
+	 */
+vector_entry SynchronousExceptionA64, .spm_shim_exceptions
+	msr	tpidr_el1, x30
+	mrs	x30, esr_el1
+	ubfx	x30, x30, #ESR_EC_SHIFT, #ESR_EC_LENGTH
+
+	cmp	x30, #EC_AARCH64_SVC
+	b.eq 	do_smc
+
+	cmp	x30, #EC_AARCH32_SVC
+	b.eq	do_smc
+
+	cmp	x30, #EC_AARCH64_SYS
+	b.eq	handle_sys_trap
+
+	/* Fail in all the other cases */
+	b	panic
+
+	/* ---------------------------------------------
+	 * Tell SPM that we are done initialising
+	 * ---------------------------------------------
+	 */
+do_smc:
+	mrs	x30, tpidr_el1
+	smc	#0
+	exception_return
+
+	/* AArch64 system instructions trap are handled as a panic for now */
+handle_sys_trap:
+panic:
+	b	panic
+end_vector_entry SynchronousExceptionA64
+
+vector_entry IrqA64, .spm_shim_exceptions
+	b	.
+end_vector_entry IrqA64
+
+vector_entry FiqA64, .spm_shim_exceptions
+	b	.
+end_vector_entry FiqA64
+
+vector_entry SErrorA64, .spm_shim_exceptions
+	b	.
+end_vector_entry SErrorA64
+
+	/* -----------------------------------------------------
+	 * Lower EL using AArch32 : 0x600 - 0x800
+	 * -----------------------------------------------------
+	 */
+vector_entry SynchronousExceptionA32, .spm_shim_exceptions
+	b	.
+end_vector_entry SynchronousExceptionA32
+
+vector_entry IrqA32, .spm_shim_exceptions
+	b	.
+end_vector_entry IrqA32
+
+vector_entry FiqA32, .spm_shim_exceptions
+	b	.
+end_vector_entry FiqA32
+
+vector_entry SErrorA32, .spm_shim_exceptions
+	b	.
+end_vector_entry SErrorA32
diff --git a/services/std_svc/spm/common/include/spm_shim_private.h b/services/std_svc/spm/common/include/spm_shim_private.h
new file mode 100644
index 0000000..bcb1147
--- /dev/null
+++ b/services/std_svc/spm/common/include/spm_shim_private.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2017-2023, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef SPM_SHIM_PRIVATE_H
+#define SPM_SHIM_PRIVATE_H
+
+#include <stdint.h>
+
+#include <lib/utils_def.h>
+
+/* Assembly source */
+IMPORT_SYM(uintptr_t, spm_shim_exceptions_ptr,		SPM_SHIM_EXCEPTIONS_PTR);
+
+/* Linker symbols */
+IMPORT_SYM(uintptr_t, __SPM_SHIM_EXCEPTIONS_START__,	SPM_SHIM_EXCEPTIONS_START);
+IMPORT_SYM(uintptr_t, __SPM_SHIM_EXCEPTIONS_END__,	SPM_SHIM_EXCEPTIONS_END);
+
+/* Definitions */
+
+#define SPM_SHIM_EXCEPTIONS_SIZE	\
+	(SPM_SHIM_EXCEPTIONS_END - SPM_SHIM_EXCEPTIONS_START)
+
+#endif /* SPM_SHIM_PRIVATE_H */
diff --git a/services/std_svc/spm/common/spm.mk b/services/std_svc/spm/common/spm.mk
index 9aa96be..9491240 100644
--- a/services/std_svc/spm/common/spm.mk
+++ b/services/std_svc/spm/common/spm.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2022, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2022-2023, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -10,8 +10,9 @@
 
 INCLUDES	+=	-Iservices/std_svc/spm/common/include
 
-SPM_SOURCES	:=	$(addprefix services/std_svc/spm/common/,\
-			${ARCH}/spm_helpers.S)
+SPM_SOURCES	:=	$(addprefix services/std_svc/spm/common/,	\
+			${ARCH}/spm_helpers.S				\
+			${ARCH}/spm_shim_exceptions.S)
 
 # Let the top-level Makefile know that we intend to include a BL32 image
 NEED_BL32		:=	yes