osThreadNew ignores MPU

[kossnikita]

Perhaps this is more of a usage question than a real issue.

I don't understand how to use the CMSIS OS2 wrapper when I have the MPU enabled. I selected the GCC_ARM_CM4_MPU port in FreeRTOS. I added the necessary sections to the linker script, and everything compiles and runs on the hardware.

The problem starts when I create a new task. I noticed that the task creation doesn't use the privileged/unprivileged mode selection.

  const osThreadAttr_t test_task_attr = {
      .name = "TestTask",
      .stack_size = 512,
      .priority = osPriorityNormal,
      .attr_bits = osThreadPrivileged,
  };
  osThreadNew(test_task, NULL, &test_task_attr);

CMSIS-FreeRTOS/CMSIS/RTOS2/FreeRTOS/Source/cmsis_os2.c

Lines 544 to 551 in 26970e1

	if (attr->priority != osPriorityNone) {
	prio = (UBaseType_t)attr->priority;
	}
	if ((prio < osPriorityIdle) || (prio > osPriorityISR) || ((attr->attr_bits & osThreadJoinable) == osThreadJoinable)) {
	/* Invalid priority or unsupported osThreadJoinable attribute used */
	return (NULL);
	}

Because of this, the xTaskCreate call fails because the unprivileged mode is selected by default, which is not supported.

CMSIS-FreeRTOS/Source/portable/Common/mpu_wrappers_v2.c

Lines 1562 to 1563 in 26970e1

	/* xTaskCreate() can only be used to create privileged tasks in MPU port. */
	if( ( uxPriority & portPRIVILEGE_BIT ) != 0 )

Have I configured something incorrectly? Or is MPU support with CMSIS OS2 implemented differently?

[VladimirUmek]

Sorry for a late reply - I just added this to the todo list and then forgot to reply.

You are right, currently this is not supported as privilege is not taken into account and this needs to be addressed.