1 files changed, 73 insertions, 0 deletions
diff --git a/services/std_svc/rmmd/aarch64/rmmd_helpers.S b/services/std_svc/rmmd/aarch64/rmmd_helpers.S
new file mode 100644
index 000000000..6229baf4d
--- /dev/null
+++ b/services/std_svc/rmmd/aarch64/rmmd_helpers.S
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2021, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "../rmmd_private.h"
+#include <asm_macros.S>
+
+	.global rmmd_rmm_enter
+	.global rmmd_rmm_exit
+
+	/* ---------------------------------------------------------------------
+	 * This function is called with SP_EL0 as stack. Here we stash our EL3
+	 * callee-saved registers on to the stack as a part of saving the C
+	 * runtime and enter the secure payload.
+	 * 'x0' contains a pointer to the memory where the address of the C
+	 *  runtime context is to be saved.
+	 * ---------------------------------------------------------------------
+	 */
+func rmmd_rmm_enter
+	/* Make space for the registers that we're going to save */
+	mov	x3, sp
+	str	x3, [x0, #0]
+	sub	sp, sp, #RMMD_C_RT_CTX_SIZE
+
+	/* Save callee-saved registers on to the stack */
+	stp	x19, x20, [sp, #RMMD_C_RT_CTX_X19]
+	stp	x21, x22, [sp, #RMMD_C_RT_CTX_X21]
+	stp	x23, x24, [sp, #RMMD_C_RT_CTX_X23]
+	stp	x25, x26, [sp, #RMMD_C_RT_CTX_X25]
+	stp	x27, x28, [sp, #RMMD_C_RT_CTX_X27]
+	stp	x29, x30, [sp, #RMMD_C_RT_CTX_X29]
+
+	/* ---------------------------------------------------------------------
+	 * Everything is setup now. el3_exit() will use the secure context to
+	 * restore to the general purpose and EL3 system registers to ERET
+	 * into the secure payload.
+	 * ---------------------------------------------------------------------
+	 */
+	b	el3_exit
+endfunc rmmd_rmm_enter
+
+	/* ---------------------------------------------------------------------
+	 * This function is called with 'x0' pointing to a C runtime context.
+	 * It restores the saved registers and jumps to that runtime with 'x0'
+	 * as the new SP register. This destroys the C runtime context that had
+	 * been built on the stack below the saved context by the caller. Later
+	 * the second parameter 'x1' is passed as a return value to the caller.
+	 * ---------------------------------------------------------------------
+	 */
+func rmmd_rmm_exit
+	/* Restore the previous stack */
+	mov	sp, x0
+
+	/* Restore callee-saved registers on to the stack */
+	ldp	x19, x20, [x0, #(RMMD_C_RT_CTX_X19 - RMMD_C_RT_CTX_SIZE)]
+	ldp	x21, x22, [x0, #(RMMD_C_RT_CTX_X21 - RMMD_C_RT_CTX_SIZE)]
+	ldp	x23, x24, [x0, #(RMMD_C_RT_CTX_X23 - RMMD_C_RT_CTX_SIZE)]
+	ldp	x25, x26, [x0, #(RMMD_C_RT_CTX_X25 - RMMD_C_RT_CTX_SIZE)]
+	ldp	x27, x28, [x0, #(RMMD_C_RT_CTX_X27 - RMMD_C_RT_CTX_SIZE)]
+	ldp	x29, x30, [x0, #(RMMD_C_RT_CTX_X29 - RMMD_C_RT_CTX_SIZE)]
+
+	/* ---------------------------------------------------------------------
+	 * This should take us back to the instruction after the call to the
+	 * last rmmd_rmm_enter().* Place the second parameter to x0
+	 * so that the caller will see it as a return value from the original
+	 * entry call.
+	 * ---------------------------------------------------------------------
+	 */
+	mov	x0, x1
+	ret
+endfunc rmmd_rmm_exit