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-rw-r--r--services/std_svc/rmmd/aarch64/rmmd_helpers.S73
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 0000000..6229baf
--- /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