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/*
* Copyright (c) 2021-2022, ProvenRun S.A.S. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <asm_macros.S>
#include "pncd_private.h"
.global pncd_enter_sp
/* ---------------------------------------------
* 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 pncd_enter_sp
/* Make space for the registers that we're going to save */
mov x3, sp
str x3, [x0, #0]
sub sp, sp, #PNCD_C_RT_CTX_SIZE
/* Save callee-saved registers on to the stack */
stp x19, x20, [sp, #PNCD_C_RT_CTX_X19]
stp x21, x22, [sp, #PNCD_C_RT_CTX_X21]
stp x23, x24, [sp, #PNCD_C_RT_CTX_X23]
stp x25, x26, [sp, #PNCD_C_RT_CTX_X25]
stp x27, x28, [sp, #PNCD_C_RT_CTX_X27]
stp x29, x30, [sp, #PNCD_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 pncd_enter_sp
/* ---------------------------------------------
* This function is called 'x0' pointing to a C
* runtime context saved in pncd_enter_sp(). It
* restores the saved registers and jumps to
* that runtime with 'x0' as the new sp. 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 return value to the caller
* ---------------------------------------------
*/
.global pncd_exit_sp
func pncd_exit_sp
/* Restore the previous stack */
mov sp, x0
/* Restore callee-saved registers on to the stack */
ldp x19, x20, [x0, #(PNCD_C_RT_CTX_X19 - PNCD_C_RT_CTX_SIZE)]
ldp x21, x22, [x0, #(PNCD_C_RT_CTX_X21 - PNCD_C_RT_CTX_SIZE)]
ldp x23, x24, [x0, #(PNCD_C_RT_CTX_X23 - PNCD_C_RT_CTX_SIZE)]
ldp x25, x26, [x0, #(PNCD_C_RT_CTX_X25 - PNCD_C_RT_CTX_SIZE)]
ldp x27, x28, [x0, #(PNCD_C_RT_CTX_X27 - PNCD_C_RT_CTX_SIZE)]
ldp x29, x30, [x0, #(PNCD_C_RT_CTX_X29 - PNCD_C_RT_CTX_SIZE)]
/* ---------------------------------------------
* This should take us back to the instruction
* after the call to the last pncd_enter_sp().
* 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 pncd_exit_sp
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