/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * 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
 *
 */

/* Standard includes. */
#include <stdint.h>

/* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE ensures that PRIVILEGED_FUNCTION
 * is defined correctly and privileged functions are placed in correct sections. */
#define MPU_WRAPPERS_INCLUDED_FROM_API_FILE

/* Portasm includes. */
#include "portasm.h"

/* MPU_WRAPPERS_INCLUDED_FROM_API_FILE is needed to be defined only for the
 * header files. */
#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE

#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

#if ( configENABLE_MPU == 1 )

void vRestoreContextOfFirstTask( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        " .syntax unified                                 \n"
        "                                                 \n"
        " program_mpu_first_task:                         \n"
        "    ldr r3, pxCurrentTCBConst2                   \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "    ldr r0, [r3]                                 \n" /* r0 = pxCurrentTCB.*/
        "                                                 \n"
        "    dmb                                          \n" /* Complete outstanding transfers before disabling MPU. */
        "    ldr r1, xMPUCTRLConst2                       \n" /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
        "    ldr r2, [r1]                                 \n" /* Read the value of MPU_CTRL. */
        "    movs r3, #1                                  \n" /* r3 = 1. */
        "    bics r2, r3                                  \n" /* r2 = r2 & ~r3 i.e. Clear the bit 0 in r2. */
        "    str r2, [r1]                                 \n" /* Disable MPU. */
        "                                                 \n"
        "    adds r0, #4                                  \n" /* r0 = r0 + 4. r0 now points to MAIR0 in TCB. */
        "    ldr r1, [r0]                                 \n" /* r1 = *r0 i.e. r1 = MAIR0. */
        "    ldr r2, xMAIR0Const2                         \n" /* r2 = 0xe000edc0 [Location of MAIR0]. */
        "    str r1, [r2]                                 \n" /* Program MAIR0. */
        "                                                 \n"
        "    adds r0, #4                                  \n" /* r0 = r0 + 4. r0 now points to first RBAR in TCB. */
        "    ldr r1, xRNRConst2                           \n" /* r1 = 0xe000ed98 [Location of RNR]. */
        "                                                 \n"
        "    movs r3, #4                                  \n" /* r3 = 4. */
        "    str r3, [r1]                                 \n" /* Program RNR = 4. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read first set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst2                          \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write first set of RBAR/RLAR registers. */
        "    movs r3, #5                                  \n" /* r3 = 5. */
        "    str r3, [r1]                                 \n" /* Program RNR = 5. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read second set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst2                          \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write second set of RBAR/RLAR registers. */
        "    movs r3, #6                                  \n" /* r3 = 6. */
        "    str r3, [r1]                                 \n" /* Program RNR = 6. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read third set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst2                          \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write third set of RBAR/RLAR registers. */
        "    movs r3, #7                                  \n" /* r3 = 6. */
        "    str r3, [r1]                                 \n" /* Program RNR = 7. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read fourth set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst2                          \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write fourth set of RBAR/RLAR registers. */
        "                                                 \n"
        "   ldr r1, xMPUCTRLConst2                        \n" /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
        "   ldr r2, [r1]                                  \n" /* Read the value of MPU_CTRL. */
        "   movs r3, #1                                   \n" /* r3 = 1. */
        "   orrs r2, r3                                   \n" /* r2 = r2 | r3 i.e. Set the bit 0 in r2. */
        "   str r2, [r1]                                  \n" /* Enable MPU. */
        "   dsb                                           \n" /* Force memory writes before continuing. */
        "                                                 \n"
        " restore_context_first_task:                     \n"
        "    ldr r3, pxCurrentTCBConst2                   \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "    ldr r1, [r3]                                 \n" /* r1 = pxCurrentTCB.*/
        "    ldr r2, [r1]                                 \n" /* r2 = Location of saved context in TCB. */
        "                                                 \n"
        " restore_special_regs_first_task:                \n"
        "    subs r2, #20                                 \n"
        "    ldmia r2!, {r0, r3-r6}                       \n" /* r0 = xSecureContext, r3 = original PSP, r4 = PSPLIM, r5 = CONTROL, r6 = LR. */
        "    subs r2, #20                                 \n"
        "    msr psp, r3                                  \n"
        "    msr psplim, r4                               \n"
        "    msr control, r5                              \n"
        "    mov lr, r6                                   \n"
        "    ldr r4, xSecureContextConst2                 \n" /* Read the location of xSecureContext i.e. &( xSecureContext ). */
        "    str r0, [r4]                                 \n" /* Restore xSecureContext. */
        "                                                 \n"
        " restore_general_regs_first_task:                \n"
        "    subs r2, #32                                 \n"
        "    ldmia r2!, {r4-r7}                           \n" /* r4-r7 contain half of the hardware saved context. */
        "    stmia r3!, {r4-r7}                           \n" /* Copy half of the the hardware saved context on the task stack. */
        "    ldmia r2!, {r4-r7}                           \n" /* r4-r7 contain rest half of the hardware saved context. */
        "    stmia r3!, {r4-r7}                           \n" /* Copy rest half of the the hardware saved context on the task stack. */
        "    subs r2, #48                                 \n"
        "    ldmia r2!, {r4-r7}                           \n" /* Restore r8-r11. */
        "    mov r8, r4                                   \n" /* r8 = r4. */
        "    mov r9, r5                                   \n" /* r9 = r5. */
        "    mov r10, r6                                  \n" /* r10 = r6. */
        "    mov r11, r7                                  \n" /* r11 = r7. */
        "    subs r2, #32                                 \n"
        "    ldmia r2!, {r4-r7}                           \n" /* Restore r4-r7. */
        "    subs r2, #16                                 \n"
        "                                                 \n"
        " restore_context_done_first_task:                \n"
        "    str r2, [r1]                                 \n" /* Save the location where the context should be saved next as the first member of TCB. */
        "    bx lr                                        \n"
        "                                                 \n"
        " .align 4                                        \n"
        " pxCurrentTCBConst2: .word pxCurrentTCB          \n"
        " xSecureContextConst2: .word xSecureContext      \n"
        " xMPUCTRLConst2: .word 0xe000ed94                \n"
        " xMAIR0Const2: .word 0xe000edc0                  \n"
        " xRNRConst2: .word 0xe000ed98                    \n"
        " xRBARConst2: .word 0xe000ed9c                   \n"
    );
}

#else /* configENABLE_MPU */

void vRestoreContextOfFirstTask( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   ldr  r2, pxCurrentTCBConst2                     \n"/* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "   ldr  r3, [r2]                                   \n"/* Read pxCurrentTCB. */
        "   ldr  r0, [r3]                                   \n"/* Read top of stack from TCB - The first item in pxCurrentTCB is the task top of stack. */
        "                                                   \n"
        "   ldm  r0!, {r1-r3}                               \n"/* Read from stack - r1 = xSecureContext, r2 = PSPLIM and r3 = EXC_RETURN. */
        "   ldr  r4, xSecureContextConst2                   \n"
        "   str  r1, [r4]                                   \n"/* Set xSecureContext to this task's value for the same. */
        "   msr  psplim, r2                                 \n"/* Set this task's PSPLIM value. */
        "   movs r1, #2                                     \n"/* r1 = 2. */
        "   msr  CONTROL, r1                                \n"/* Switch to use PSP in the thread mode. */
        "   adds r0, #32                                    \n"/* Discard everything up to r0. */
        "   msr  psp, r0                                    \n"/* This is now the new top of stack to use in the task. */
        "   isb                                             \n"
        "   bx   r3                                         \n"/* Finally, branch to EXC_RETURN. */
        "                                                   \n"
        "   .align 4                                        \n"
        "pxCurrentTCBConst2: .word pxCurrentTCB             \n"
        "xSecureContextConst2: .word xSecureContext         \n"
    );
}

#endif /* configENABLE_MPU */
/*-----------------------------------------------------------*/

BaseType_t xIsPrivileged( void ) /* __attribute__ (( naked )) */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   mrs r0, control                                 \n"/* r0 = CONTROL. */
        "   movs r1, #1                                     \n"/* r1 = 1. */
        "   tst r0, r1                                      \n"/* Perform r0 & r1 (bitwise AND) and update the conditions flag. */
        "   beq running_privileged                          \n"/* If the result of previous AND operation was 0, branch. */
        "   movs r0, #0                                     \n"/* CONTROL[0]!=0. Return false to indicate that the processor is not privileged. */
        "   bx lr                                           \n"/* Return. */
        " running_privileged:                               \n"
        "   movs r0, #1                                     \n"/* CONTROL[0]==0. Return true to indicate that the processor is privileged. */
        "   bx lr                                           \n"/* Return. */
        "                                                   \n"
        "   .align 4                                        \n"
        ::: "r0", "r1", "memory"
    );
}
/*-----------------------------------------------------------*/

void vRaisePrivilege( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   mrs r0, control                                 \n"/* Read the CONTROL register. */
        "   movs r1, #1                                     \n"/* r1 = 1. */
        "   bics r0, r1                                     \n"/* Clear the bit 0. */
        "   msr control, r0                                 \n"/* Write back the new CONTROL value. */
        "   bx lr                                           \n"/* Return to the caller. */
        ::: "r0", "r1", "memory"
    );
}
/*-----------------------------------------------------------*/

void vResetPrivilege( void ) /* __attribute__ (( naked )) */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   mrs r0, control                                 \n"/* r0 = CONTROL. */
        "   movs r1, #1                                     \n"/* r1 = 1. */
        "   orrs r0, r1                                     \n"/* r0 = r0 | r1. */
        "   msr control, r0                                 \n"/* CONTROL = r0. */
        "   bx lr                                           \n"/* Return to the caller. */
        ::: "r0", "r1", "memory"
    );
}
/*-----------------------------------------------------------*/

void vStartFirstTask( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   ldr r0, xVTORConst                              \n"/* Use the NVIC offset register to locate the stack. */
        "   ldr r0, [r0]                                    \n"/* Read the VTOR register which gives the address of vector table. */
        "   ldr r0, [r0]                                    \n"/* The first entry in vector table is stack pointer. */
        "   msr msp, r0                                     \n"/* Set the MSP back to the start of the stack. */
        "   cpsie i                                         \n"/* Globally enable interrupts. */
        "   dsb                                             \n"
        "   isb                                             \n"
        "   svc %0                                          \n"/* System call to start the first task. */
        "   nop                                             \n"
        "                                                   \n"
        "   .align 4                                        \n"
        "xVTORConst: .word 0xe000ed08                       \n"
        ::"i" ( portSVC_START_SCHEDULER ) : "memory"
    );
}
/*-----------------------------------------------------------*/

uint32_t ulSetInterruptMask( void ) /* __attribute__(( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   mrs r0, PRIMASK                                 \n"
        "   cpsid i                                         \n"
        "   bx lr                                           \n"
        ::: "memory"
    );
}
/*-----------------------------------------------------------*/

void vClearInterruptMask( __attribute__( ( unused ) ) uint32_t ulMask ) /* __attribute__(( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   msr PRIMASK, r0                                 \n"
        "   bx lr                                           \n"
        ::: "memory"
    );
}
/*-----------------------------------------------------------*/

#if ( configENABLE_MPU == 1 )

void PendSV_Handler( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        " .syntax unified                                 \n"
        " .extern SecureContext_SaveContext               \n"
        " .extern SecureContext_LoadContext               \n"
        "                                                 \n"
        " ldr r3, xSecureContextConst                     \n" /* Read the location of xSecureContext i.e. &( xSecureContext ). */
        " ldr r0, [r3]                                    \n" /* Read xSecureContext - Value of xSecureContext must be in r0 as it is used as a parameter later. */
        " ldr r3, pxCurrentTCBConst                       \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        " ldr r1, [r3]                                    \n" /* Read pxCurrentTCB - Value of pxCurrentTCB must be in r1 as it is used as a parameter later.*/
        " ldr r2, [r1]                                    \n" /* r2 = Location in TCB where the context should be saved. */
        "                                                 \n"
        " cbz r0, save_ns_context                         \n" /* No secure context to save. */
        " save_s_context:                                 \n"
        "    push {r0-r2, lr}                             \n"
        "    bl SecureContext_SaveContext                 \n" /* Params are in r0 and r1. r0 = xSecureContext and r1 = pxCurrentTCB. */
        "    pop {r0-r3}                                  \n" /* LR is now in r3. */
        "    mov lr, r3                                   \n" /* Restore LR. */
        "                                                 \n"
        " save_ns_context:                                \n"
        "    mov r3, lr                                   \n" /* r3 = LR (EXC_RETURN). */
        "    lsls r3, r3, #25                             \n" /* r3 = r3 << 25. Bit[6] of EXC_RETURN is 1 if secure stack was used, 0 if non-secure stack was used to store stack frame. */
        "    bmi save_special_regs                        \n" /* r3 < 0 ==> Bit[6] in EXC_RETURN is 1 ==> secure stack was used to store the stack frame. */
        "                                                 \n"
        " save_general_regs:                              \n"
        "    mrs r3, psp                                  \n"
        "    stmia r2!, {r4-r7}                           \n" /* Store r4-r7. */
        "    mov r4, r8                                   \n" /* r4 = r8. */
        "    mov r5, r9                                   \n" /* r5 = r9. */
        "    mov r6, r10                                  \n" /* r6 = r10. */
        "    mov r7, r11                                  \n" /* r7 = r11. */
        "    stmia r2!, {r4-r7}                           \n" /* Store r8-r11. */
        "    ldmia r3!, {r4-r7}                           \n" /* Copy half of the  hardware saved context into r4-r7. */
        "    stmia r2!, {r4-r7}                           \n" /* Store the hardware saved context. */
        "    ldmia r3!, {r4-r7}                           \n" /* Copy rest half of the  hardware saved context into r4-r7. */
        "    stmia r2!, {r4-r7}                           \n" /* Store the hardware saved context. */
        "                                                 \n"
        " save_special_regs:                              \n"
        "    mrs r3, psp                                  \n" /* r3 = PSP. */
        "    mrs r4, psplim                               \n" /* r4 = PSPLIM. */
        "    mrs r5, control                              \n" /* r5 = CONTROL. */
        "    mov r6, lr                                   \n" /* r6 = LR. */
        "    stmia r2!, {r0, r3-r6}                       \n" /* Store xSecureContext, original PSP (after hardware has saved context), PSPLIM, CONTROL and LR. */
        "    str r2, [r1]                                 \n" /* Save the location from where the context should be restored as the first member of TCB. */
        "                                                 \n"
        " select_next_task:                               \n"
        "    cpsid i                                      \n"
        "    bl vTaskSwitchContext                        \n"
        "    cpsie i                                      \n"
        "                                                 \n"
        " program_mpu:                                    \n"
        "    ldr r3, pxCurrentTCBConst                    \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "    ldr r0, [r3]                                 \n" /* r0 = pxCurrentTCB.*/
        "                                                 \n"
        "    dmb                                          \n" /* Complete outstanding transfers before disabling MPU. */
        "    ldr r1, xMPUCTRLConst                        \n" /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
        "    ldr r2, [r1]                                 \n" /* Read the value of MPU_CTRL. */
        "    movs r3, #1                                  \n" /* r3 = 1. */
        "    bics r2, r3                                  \n" /* r2 = r2 & ~r3 i.e. Clear the bit 0 in r2. */
        "    str r2, [r1]                                 \n" /* Disable MPU. */
        "                                                 \n"
        "    adds r0, #4                                  \n" /* r0 = r0 + 4. r0 now points to MAIR0 in TCB. */
        "    ldr r1, [r0]                                 \n" /* r1 = *r0 i.e. r1 = MAIR0. */
        "    ldr r2, xMAIR0Const                          \n" /* r2 = 0xe000edc0 [Location of MAIR0]. */
        "    str r1, [r2]                                 \n" /* Program MAIR0. */
        "                                                 \n"
        "    adds r0, #4                                  \n" /* r0 = r0 + 4. r0 now points to first RBAR in TCB. */
        "    ldr r1, xRNRConst                            \n" /* r1 = 0xe000ed98 [Location of RNR]. */
        "                                                 \n"
        "    movs r3, #4                                  \n" /* r3 = 4. */
        "    str r3, [r1]                                 \n" /* Program RNR = 4. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read first set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst                           \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write first set of RBAR/RLAR registers. */
        "    movs r3, #5                                  \n" /* r3 = 5. */
        "    str r3, [r1]                                 \n" /* Program RNR = 5. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read second set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst                           \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write second set of RBAR/RLAR registers. */
        "    movs r3, #6                                  \n" /* r3 = 6. */
        "    str r3, [r1]                                 \n" /* Program RNR = 6. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read third set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst                           \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write third set of RBAR/RLAR registers. */
        "    movs r3, #7                                  \n" /* r3 = 6. */
        "    str r3, [r1]                                 \n" /* Program RNR = 7. */
        "    ldmia r0!, {r4-r5}                           \n" /* Read fourth set of RBAR/RLAR registers from TCB. */
        "    ldr r2, xRBARConst                           \n" /* r2 = 0xe000ed9c [Location of RBAR]. */
        "    stmia r2!, {r4-r5}                           \n" /* Write fourth set of RBAR/RLAR registers. */
        "                                                 \n"
        "    ldr r1, xMPUCTRLConst                        \n" /* r1 = 0xe000ed94 [Location of MPU_CTRL]. */
        "    ldr r2, [r1]                                 \n" /* Read the value of MPU_CTRL. */
        "    movs r3, #1                                  \n" /* r3 = 1. */
        "    orrs r2, r3                                  \n" /* r2 = r2 | r3 i.e. Set the bit 0 in r2. */
        "    str r2, [r1]                                 \n" /* Enable MPU. */
        "    dsb                                          \n" /* Force memory writes before continuing. */
        "                                                 \n"
        " restore_context:                                \n"
        "    ldr r3, pxCurrentTCBConst                    \n" /* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "    ldr r1, [r3]                                 \n" /* r1 = pxCurrentTCB.*/
        "    ldr r2, [r1]                                 \n" /* r2 = Location of saved context in TCB. */
        "                                                 \n"
        " restore_special_regs:                           \n"
        "    subs r2, #20                                 \n"
        "    ldmia r2!, {r0, r3-r6}                       \n" /* r0 = xSecureContext, r3 = original PSP, r4 = PSPLIM, r5 = CONTROL, r6 = LR. */
        "    subs r2, #20                                 \n"
        "    msr psp, r3                                  \n"
        "    msr psplim, r4                               \n"
        "    msr control, r5                              \n"
        "    mov lr, r6                                   \n"
        "    ldr r4, xSecureContextConst                  \n" /* Read the location of xSecureContext i.e. &( xSecureContext ). */
        "    str r0, [r4]                                 \n" /* Restore xSecureContext. */
        "    cbz r0, restore_ns_context                   \n" /* No secure context to restore. */
        "                                                 \n"
        " restore_s_context:                              \n"
        "    push {r1-r3, lr}                             \n"
        "    bl SecureContext_LoadContext                 \n" /* Params are in r0 and r1. r0 = xSecureContext and r1 = pxCurrentTCB. */
        "    pop {r1-r4}                                  \n" /* LR is now in r4. */
        "    mov lr, r4                                   \n"
        "                                                 \n"
        " restore_ns_context:                             \n"
        "    mov r0, lr                                   \n" /* r0 = LR (EXC_RETURN). */
        "    lsls r0, r0, #25                             \n" /* r0 = r0 << 25. Bit[6] of EXC_RETURN is 1 if secure stack was used, 0 if non-secure stack was used to store stack frame. */
        "    bmi restore_context_done                     \n" /* r0 < 0 ==> Bit[6] in EXC_RETURN is 1 ==> secure stack was used to store the stack frame. */
        "                                                 \n"
        " restore_general_regs:                           \n"
        "    subs r2, #32                                 \n"
        "    ldmia r2!, {r4-r7}                           \n" /* r4-r7 contain half of the hardware saved context. */
        "    stmia r3!, {r4-r7}                           \n" /* Copy half of the the hardware saved context on the task stack. */
        "    ldmia r2!, {r4-r7}                           \n" /* r4-r7 contain rest half of the hardware saved context. */
        "    stmia r3!, {r4-r7}                           \n" /* Copy rest half of the the hardware saved context on the task stack. */
        "    subs r2, #48                                 \n"
        "    ldmia r2!, {r4-r7}                           \n" /* Restore r8-r11. */
        "    mov r8, r4                                   \n" /* r8 = r4. */
        "    mov r9, r5                                   \n" /* r9 = r5. */
        "    mov r10, r6                                  \n" /* r10 = r6. */
        "    mov r11, r7                                  \n" /* r11 = r7. */
        "    subs r2, #32                                 \n"
        "    ldmia r2!, {r4-r7}                           \n" /* Restore r4-r7. */
        "    subs r2, #16                                 \n"
        "                                                 \n"
        " restore_context_done:                           \n"
        "    str r2, [r1]                                 \n" /* Save the location where the context should be saved next as the first member of TCB. */
        "    bx lr                                        \n"
        "                                                 \n"
        " .align 4                                        \n"
        " pxCurrentTCBConst: .word pxCurrentTCB           \n"
        " xSecureContextConst: .word xSecureContext       \n"
        " xMPUCTRLConst: .word 0xe000ed94                 \n"
        " xMAIR0Const: .word 0xe000edc0                   \n"
        " xRNRConst: .word 0xe000ed98                     \n"
        " xRBARConst: .word 0xe000ed9c                    \n"
    );
}

#else /* configENABLE_MPU */

void PendSV_Handler( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "   .extern SecureContext_SaveContext               \n"
        "   .extern SecureContext_LoadContext               \n"
        "                                                   \n"
        "   ldr r3, xSecureContextConst                     \n"/* Read the location of xSecureContext i.e. &( xSecureContext ). */
        "   ldr r0, [r3]                                    \n"/* Read xSecureContext - Value of xSecureContext must be in r0 as it is used as a parameter later. */
        "   ldr r3, pxCurrentTCBConst                       \n"/* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "   ldr r1, [r3]                                    \n"/* Read pxCurrentTCB - Value of pxCurrentTCB must be in r1 as it is used as a parameter later.*/
        "   mrs r2, psp                                     \n"/* Read PSP in r2. */
        "                                                   \n"
        "   cbz r0, save_ns_context                         \n"/* No secure context to save. */
        "   push {r0-r2, r14}                               \n"
        "   bl SecureContext_SaveContext                    \n"/* Params are in r0 and r1. r0 = xSecureContext and r1 = pxCurrentTCB. */
        "   pop {r0-r3}                                     \n"/* LR is now in r3. */
        "   mov lr, r3                                      \n"/* LR = r3. */
        "   lsls r1, r3, #25                                \n"/* r1 = r3 << 25. Bit[6] of EXC_RETURN is 1 if secure stack was used, 0 if non-secure stack was used to store stack frame. */
        "   bpl save_ns_context                             \n"/* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
        "   ldr r3, pxCurrentTCBConst                       \n"/* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "   ldr r1, [r3]                                    \n"/* Read pxCurrentTCB. */
        "   subs r2, r2, #12                                \n"/* Make space for xSecureContext, PSPLIM and LR on the stack. */
        "   str r2, [r1]                                    \n"/* Save the new top of stack in TCB. */
        "   mrs r1, psplim                                  \n"/* r1 = PSPLIM. */
        "   mov r3, lr                                      \n"/* r3 = LR/EXC_RETURN. */
        "   stmia r2!, {r0, r1, r3}                         \n"/* Store xSecureContext, PSPLIM and LR on the stack. */
        "   b select_next_task                              \n"
        "                                                   \n"
        " save_ns_context:                                  \n"
        "   ldr r3, pxCurrentTCBConst                       \n"/* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "   ldr r1, [r3]                                    \n"/* Read pxCurrentTCB. */
        "   subs r2, r2, #44                                \n"/* Make space for xSecureContext, PSPLIM, LR and the remaining registers on the stack. */
        "   str r2, [r1]                                    \n"/* Save the new top of stack in TCB. */
        "   mrs r1, psplim                                  \n"/* r1 = PSPLIM. */
        "   mov r3, lr                                      \n"/* r3 = LR/EXC_RETURN. */
        "   stmia r2!, {r0, r1, r3-r7}                      \n"/* Store xSecureContext, PSPLIM, LR and the low registers that are not saved automatically. */
        "   mov r4, r8                                      \n"/* r4 = r8. */
        "   mov r5, r9                                      \n"/* r5 = r9. */
        "   mov r6, r10                                     \n"/* r6 = r10. */
        "   mov r7, r11                                     \n"/* r7 = r11. */
        "   stmia r2!, {r4-r7}                              \n"/* Store the high registers that are not saved automatically. */
        "                                                   \n"
        " select_next_task:                                 \n"
        "   cpsid i                                         \n"
        "   bl vTaskSwitchContext                           \n"
        "   cpsie i                                         \n"
        "                                                   \n"
        "   ldr r3, pxCurrentTCBConst                       \n"/* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "   ldr r1, [r3]                                    \n"/* Read pxCurrentTCB. */
        "   ldr r2, [r1]                                    \n"/* The first item in pxCurrentTCB is the task top of stack. r2 now points to the top of stack. */
        "                                                   \n"
        "   ldmia r2!, {r0, r1, r4}                         \n"/* Read from stack - r0 = xSecureContext, r1 = PSPLIM and r4 = LR. */
        "   msr psplim, r1                                  \n"/* Restore the PSPLIM register value for the task. */
        "   mov lr, r4                                      \n"/* LR = r4. */
        "   ldr r3, xSecureContextConst                     \n"/* Read the location of xSecureContext i.e. &( xSecureContext ). */
        "   str r0, [r3]                                    \n"/* Restore the task's xSecureContext. */
        "   cbz r0, restore_ns_context                      \n"/* If there is no secure context for the task, restore the non-secure context. */
        "   ldr r3, pxCurrentTCBConst                       \n"/* Read the location of pxCurrentTCB i.e. &( pxCurrentTCB ). */
        "   ldr r1, [r3]                                    \n"/* Read pxCurrentTCB. */
        "   push {r2, r4}                                   \n"
        "   bl SecureContext_LoadContext                    \n"/* Restore the secure context. Params are in r0 and r1. r0 = xSecureContext and r1 = pxCurrentTCB. */
        "   pop {r2, r4}                                    \n"
        "   mov lr, r4                                      \n"/* LR = r4. */
        "   lsls r1, r4, #25                                \n"/* r1 = r4 << 25. Bit[6] of EXC_RETURN is 1 if secure stack was used, 0 if non-secure stack was used to store stack frame. */
        "   bpl restore_ns_context                          \n"/* bpl - branch if positive or zero. If r1 >= 0 ==> Bit[6] in EXC_RETURN is 0 i.e. non-secure stack was used. */
        "   msr psp, r2                                     \n"/* Remember the new top of stack for the task. */
        "   bx lr                                           \n"
        "                                                   \n"
        " restore_ns_context:                               \n"
        "   adds r2, r2, #16                                \n"/* Move to the high registers. */
        "   ldmia r2!, {r4-r7}                              \n"/* Restore the high registers that are not automatically restored. */
        "   mov r8, r4                                      \n"/* r8 = r4. */
        "   mov r9, r5                                      \n"/* r9 = r5. */
        "   mov r10, r6                                     \n"/* r10 = r6. */
        "   mov r11, r7                                     \n"/* r11 = r7. */
        "   msr psp, r2                                     \n"/* Remember the new top of stack for the task. */
        "   subs r2, r2, #32                                \n"/* Go back to the low registers. */
        "   ldmia r2!, {r4-r7}                              \n"/* Restore the low registers that are not automatically restored. */
        "   bx lr                                           \n"
        "                                                   \n"
        "   .align 4                                        \n"
        "pxCurrentTCBConst: .word pxCurrentTCB              \n"
        "xSecureContextConst: .word xSecureContext          \n"
    );
}

#endif /* configENABLE_MPU */
/*-----------------------------------------------------------*/

#if ( ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) )

void SVC_Handler( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
   __asm volatile
    (
        ".syntax unified                \n"
        ".extern vPortSVCHandler_C      \n"
        ".extern vSystemCallEnter       \n"
        ".extern vSystemCallEnter_1     \n"
        ".extern vSystemCallExit        \n"
        "                               \n"
        "movs r0, #4                    \n"
        "mov r1, lr                     \n"
        "tst r0, r1                     \n"
        "beq stack_on_msp               \n"
        "stack_on_psp:                  \n"
        "    mrs r0, psp                \n"
        "    b route_svc                \n"
        "stack_on_msp:                  \n"
        "    mrs r0, msp                \n"
        "    b route_svc                \n"
        "                               \n"
        "route_svc:                     \n"
        "    ldr r2, [r0, #24]          \n"
        "    subs r2, #2                \n"
        "    ldrb r3, [r2, #0]          \n"
        "    cmp r3, %0                 \n"
        "    beq system_call_enter      \n"
        "    cmp r3, %1                 \n"
        "    beq system_call_enter_1    \n"
        "    cmp r3, %2                 \n"
        "    beq system_call_exit       \n"
        "    b vPortSVCHandler_C        \n"
        "                               \n"
        "system_call_enter:             \n"
        "    b vSystemCallEnter         \n"
        "system_call_enter_1:           \n"
        "    b vSystemCallEnter_1       \n"
        "system_call_exit:              \n"
        "    b vSystemCallExit          \n"
        "                               \n"
        : /* No outputs. */
        :"i" ( portSVC_SYSTEM_CALL_ENTER ), "i" ( portSVC_SYSTEM_CALL_ENTER_1 ), "i" ( portSVC_SYSTEM_CALL_EXIT )
        : "r0", "r1", "r2", "r3", "memory"
    );
}

#else /* ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) */

void SVC_Handler( void ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   movs r0, #4                                     \n"
        "   mov r1, lr                                      \n"
        "   tst r0, r1                                      \n"
        "   beq stacking_used_msp                           \n"
        "   mrs r0, psp                                     \n"
        "   ldr r2, svchandler_address_const                \n"
        "   bx r2                                           \n"
        " stacking_used_msp:                                \n"
        "   mrs r0, msp                                     \n"
        "   ldr r2, svchandler_address_const                \n"
        "   bx r2                                           \n"
        "                                                   \n"
        "   .align 4                                        \n"
        "svchandler_address_const: .word vPortSVCHandler_C  \n"
    );
}

#endif /* ( configENABLE_MPU == 1 ) && ( configUSE_MPU_WRAPPERS_V1 == 0 ) */
/*-----------------------------------------------------------*/

void vPortAllocateSecureContext( uint32_t ulSecureStackSize ) /* __attribute__ (( naked )) */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   svc %0                                          \n"/* Secure context is allocated in the supervisor call. */
        "   bx lr                                           \n"/* Return. */
        ::"i" ( portSVC_ALLOCATE_SECURE_CONTEXT ) : "memory"
    );
}
/*-----------------------------------------------------------*/

void vPortFreeSecureContext( uint32_t * pulTCB ) /* __attribute__ (( naked )) PRIVILEGED_FUNCTION */
{
    __asm volatile
    (
        "   .syntax unified                                 \n"
        "                                                   \n"
        "   ldr r2, [r0]                                    \n"/* The first item in the TCB is the top of the stack. */
        "   ldr r1, [r2]                                    \n"/* The first item on the stack is the task's xSecureContext. */
        "   cmp r1, #0                                      \n"/* Raise svc if task's xSecureContext is not NULL. */
        "   bne free_secure_context                         \n"/* Branch if r1 != 0. */
        "   bx lr                                           \n"/* There is no secure context (xSecureContext is NULL). */
        " free_secure_context:                              \n"
        "   svc %0                                          \n"/* Secure context is freed in the supervisor call. */
        "   bx lr                                           \n"/* Return. */
        ::"i" ( portSVC_FREE_SECURE_CONTEXT ) : "memory"
    );
}
/*-----------------------------------------------------------*/