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SPMD: add SPM dispatcher based upon SPCI Beta 0 spec    
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/*
 * Copyright (c) 2020, ARM Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <asm_macros.S>
#include "../spmd_private.h"

	.global spmd_spm_core_enter
	.global spmd_spm_core_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 spmd_spm_core_enter
	/* Make space for the registers that we're going to save */
	mov	x3, sp
	str	x3, [x0, #0]
	sub	sp, sp, #SPMD_C_RT_CTX_SIZE

	/* Save callee-saved registers on to the stack */
	stp	x19, x20, [sp, #SPMD_C_RT_CTX_X19]
	stp	x21, x22, [sp, #SPMD_C_RT_CTX_X21]
	stp	x23, x24, [sp, #SPMD_C_RT_CTX_X23]
	stp	x25, x26, [sp, #SPMD_C_RT_CTX_X25]
	stp	x27, x28, [sp, #SPMD_C_RT_CTX_X27]
	stp	x29, x30, [sp, #SPMD_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 spmd_spm_core_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 spmd_spm_core_exit
	/* Restore the previous stack */
	mov	sp, x0

	/* Restore callee-saved registers on to the stack */
	ldp	x19, x20, [x0, #(SPMD_C_RT_CTX_X19 - SPMD_C_RT_CTX_SIZE)]
	ldp	x21, x22, [x0, #(SPMD_C_RT_CTX_X21 - SPMD_C_RT_CTX_SIZE)]
	ldp	x23, x24, [x0, #(SPMD_C_RT_CTX_X23 - SPMD_C_RT_CTX_SIZE)]
	ldp	x25, x26, [x0, #(SPMD_C_RT_CTX_X25 - SPMD_C_RT_CTX_SIZE)]
	ldp	x27, x28, [x0, #(SPMD_C_RT_CTX_X27 - SPMD_C_RT_CTX_SIZE)]
	ldp	x29, x30, [x0, #(SPMD_C_RT_CTX_X29 - SPMD_C_RT_CTX_SIZE)]

	/* ---------------------------------------------------------------------
	 * This should take us back to the instruction after the call to the
	 * last spm_secure_partition_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 spmd_spm_core_exit