/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 * 1 tab == 4 spaces!
 */

/* Secure context includes. */
#include "secure_context.h"

/* Secure port macros. */
#include "secure_port_macros.h"

#if ( configENABLE_FPU == 1 )
    #error Cortex-M23 does not have a Floating Point Unit (FPU) and therefore configENABLE_FPU must be set to 0.
#endif

secureportNON_SECURE_CALLABLE void SecureContext_LoadContext( SecureContextHandle_t xSecureContextHandle )
{
    /* xSecureContextHandle value is in r0. */
    __asm volatile
    (
        "	.syntax unified							\n"
        "											\n"
        "	mrs r1, ipsr							\n"/* r1 = IPSR. */
        "	cbz r1, load_ctx_therad_mode			\n"/* Do nothing if the processor is running in the Thread Mode. */
        "	ldmia r0!, {r1, r2}						\n"/* r1 = xSecureContextHandle->pucCurrentStackPointer, r2 = xSecureContextHandle->pucStackLimit. */
        #if ( configENABLE_MPU == 1 )
            "	ldmia r1!, {r3}							\n"/* Read CONTROL register value from task's stack. r3 = CONTROL. */
            "	msr control, r3							\n"/* CONTROL = r3. */
        #endif /* configENABLE_MPU */
        "	msr psplim, r2							\n"/* PSPLIM = r2. */
        "	msr psp, r1								\n"/* PSP = r1. */
        "											\n"
        " load_ctx_therad_mode:						\n"
        "	nop										\n"
        "											\n"
        ::: "r0", "r1", "r2"
    );
}
/*-----------------------------------------------------------*/

secureportNON_SECURE_CALLABLE void SecureContext_SaveContext( SecureContextHandle_t xSecureContextHandle )
{
    /* xSecureContextHandle value is in r0. */
    __asm volatile
    (
        "	.syntax unified							\n"
        "											\n"
        "	mrs r1, ipsr							\n"/* r1 = IPSR. */
        "	cbz r1, save_ctx_therad_mode			\n"/* Do nothing if the processor is running in the Thread Mode. */
        "	mrs r1, psp								\n"/* r1 = PSP. */
        #if ( configENABLE_MPU == 1 )
            "	mrs r2, control							\n"/* r2 = CONTROL. */
            "	subs r1, r1, #4							\n"/* Make space for the CONTROL value on the stack. */
            "	str r1, [r0]							\n"/* Save the top of stack in context. xSecureContextHandle->pucCurrentStackPointer = r1. */
            "	stmia r1!, {r2}							\n"/* Store CONTROL value on the stack. */
        #else /* configENABLE_MPU */
            "	str r1, [r0]							\n"/* Save the top of stack in context. xSecureContextHandle->pucCurrentStackPointer = r1. */
        #endif /* configENABLE_MPU */
        "	movs r1, %0								\n"/* r1 = securecontextNO_STACK. */
        "	msr psplim, r1							\n"/* PSPLIM = securecontextNO_STACK. */
        "	msr psp, r1								\n"/* PSP = securecontextNO_STACK i.e. No stack for thread mode until next task's context is loaded. */
        "											\n"
        " save_ctx_therad_mode:						\n"
        "	nop										\n"
        "											\n"
        ::"i" ( securecontextNO_STACK ) : "r1", "memory"
    );
}
/*-----------------------------------------------------------*/