CM32M433R 用户模式如何切换回机器模式

/** @addtogroup CM32M4xxR_StdPeriph_Examples

 * @{

 */

#define MACHINE_MODE_STACK_SIZE                        0x400

static uint8_t sMachineModeStack[MACHINE_MODE_STACK_SIZE] = {0};

//Configure test_array Acess Permission on PMP

void PMP_Config() {

        PMP_Region_InitTypeDef pmp_init;

        pmp_init.Number = PMP_REGION_NUMBER0;

        pmp_init.Enable = PMP_REGION_ENABLE;   // Enable Configuration

        pmp_init.Lock = PMP_REGION_UNLOCK; //

        pmp_init.BaseAddress = 0;  //

        pmp_init.Size = PMP_REGION_SIZE_4GB;    //Setting array size

        pmp_init.AddressMatching = PMP_ADDRESS_MATCHING_NAPOT; //Setting PMP Size to NAPOT mode -> 2^n

        pmp_init.AccessPermission = PMP_ACCESS_RWX; //Setting array permission is Read Only

        PMP_ConfigRegion(&pmp_init);

        sPMP_Region_InitTypeDef spmp_init;

        spmp_init.Number = SPMP_REGION_NUMBER0;

        spmp_init.Enable = SPMP_REGION_ENABLE;

        spmp_init.Lock = SPMP_REGION_UNLOCK;

        spmp_init.BaseAddress = 0;

        spmp_init.Size = SPMP_REGION_SIZE_4GB;

        spmp_init.AddressMatching = SPMP_ADDRESS_MATCHING_NAPOT;

        spmp_init.UserMode = SPMP_USERMODE_RESET;

        spmp_init.AccessPermission = SPMP_ACCESS_RWX;

        sPMP_ConfigRegion(&spmp_init);

}

/**

 * [url=home.php?mod=space&uid=247401]@brief[/url] Jump User Mode

 */

void JumpUserMode(uint32_t func)

{

        __RV_CSR_WRITE(CSR_MSCRATCH, sMachineModeStack + MACHINE_MODE_STACK_SIZE);

        __RV_CSR_CLEAR(CSR_MSTATUS, MSTATUS_MPP);

        __RV_CSR_WRITE(CSR_MEPC, func);

        __ASM  volatile ( "mret ");

}

void ECALL_Exception_Handler(unsigned long mcause,unsigned long sp)

{

   uint32_t saved_regs = sp;

   uint32_t mepc = ((uint32_t *)saved_regs)[12];

   printf("ECALL Exception Trigger\r\n");

   ((uint32_t *)saved_regs)[12] = mepc + 4;

}

/**

 * [url=home.php?mod=space&uid=247401]@brief[/url] User Mode Application

 */

void Led()

{

        LedInit(LED2_PORT, LED2_PIN);

        __ECALL();

}

/**

 * @brief Main function

 */

int main(void) {

        /* System Clocks Configuration */

        PMP_Config();

        Exception_Register_EXC(UmodeEcall_EXCn, (unsigned long)ECALL_Exception_Handler);

        JumpUserMode((uint32_t)Led);

        while (1) {

            LedBlink(LED2_PORT, LED2_PIN);

            delay_ms(1000);

        }

}