diff --git a/MDK_405_dr/board/board.c b/MDK_405_dr/board/board.c
index 276f390..6f74961 100644
--- a/MDK_405_dr/board/board.c
+++ b/MDK_405_dr/board/board.c
@@ -59,9 +59,6 @@ void SystemClock_Config(void)
   HAL_RCC_EnableCSS();
 }
 
-extern int iap_main_entry(void);
-INIT_ENV_EXPORT(iap_main_entry);
-
 #include "shell.h"
 INIT_APP_EXPORT(finsh_system_init);
 
diff --git a/libraries/STM32F4xx_HAL/CMSIS/Device/ST/STM32F4xx/Source/Templates/arm/startup_stm32f405xx.s b/libraries/STM32F4xx_HAL/CMSIS/Device/ST/STM32F4xx/Source/Templates/arm/startup_stm32f405xx.s
index 397ef3c..18ffe14 100644
--- a/libraries/STM32F4xx_HAL/CMSIS/Device/ST/STM32F4xx/Source/Templates/arm/startup_stm32f405xx.s
+++ b/libraries/STM32F4xx_HAL/CMSIS/Device/ST/STM32F4xx/Source/Templates/arm/startup_stm32f405xx.s
@@ -221,6 +221,9 @@ SysTick_Handler PROC
                 EXPORT  SysTick_Handler            [WEAK]
                 B       .
                 ENDP
+rt_hw_cpu_link_port PROC
+                EXPORT  rt_hw_cpu_link_port
+                ENDP
 
 Default_Handler PROC
 
diff --git a/rt-thread/src/components.c b/rt-thread/src/components.c
index 78eb002..c6e00b9 100644
--- a/rt-thread/src/components.c
+++ b/rt-thread/src/components.c
@@ -272,3 +272,11 @@ int rtthread_startup(void)
     return 0;
 }
 #endif /* RT_USING_USER_MAIN */
+
+// empty function for link only.
+void rt_hw_cpu_link_port(void);
+int rt_conponents_init()
+{
+	RT_ASSERT(rt_hw_cpu_link_port != RT_NULL);
+	return 0;
+}