FreeRTOS-MPU Specific

Group that contains function that contains MPU specific functions. More...

Collaboration diagram for FreeRTOS-MPU Specific:

Functions
BaseType_t	xTaskCreateRestricted (const TaskParameters_t *const pxTaskDefinition, TaskHandle_t *pxCreatedTask) PRIVILEGED_FUNCTION
	Create a new task and add it to the list of tasks that are ready to run. The function parameters define the memory regions and associated access permissions allocated to the task. More...
void	vTaskAllocateMPURegions (TaskHandle_t xTask, const MemoryRegion_t *const pxRegions) PRIVILEGED_FUNCTION
	Memory regions are assigned to a restricted task when the task is created by a call to xTaskCreateRestricted(). These regions can be redefined using vTaskAllocateMPURegions(). More...

Detailed Description

Group that contains function that contains MPU specific functions.

Function Documentation

vTaskAllocateMPURegions()

void vTaskAllocateMPURegions	(	TaskHandle_t	xTask,
		const MemoryRegion_t *const	pxRegions
	)

#include <task.h>

Memory regions are assigned to a restricted task when the task is created by a call to xTaskCreateRestricted(). These regions can be redefined using vTaskAllocateMPURegions().

Parameters

xTask	The handle of the task being updated.
xRegions	A pointer to an MemoryRegion_t structure that contains the new memory region definitions.

Example usage:

// Define an array of MemoryRegion_t structures that configures an MPU region
// allowing read/write access for 1024 bytes starting at the beginning of the
// ucOneKByte array.  The other two of the maximum 3 definable regions are
// unused so set to zero.
static const MemoryRegion_t xAltRegions[ portNUM_CONFIGURABLE_REGIONS ] =
{
    // Base address     Length      Parameters
    { ucOneKByte,       1024,       portMPU_REGION_READ_WRITE },
    { 0,                0,          0 },
    { 0,                0,          0 }
};
 
void vATask( void *pvParameters )
{
    // This task was created such that it has access to certain regions of
    // memory as defined by the MPU configuration.  At some point it is
    // desired that these MPU regions are replaced with that defined in the
    // xAltRegions const struct above.  Use a call to vTaskAllocateMPURegions()
    // for this purpose.  NULL is used as the task handle to indicate that this
    // function should modify the MPU regions of the calling task.
    vTaskAllocateMPURegions( NULL, xAltRegions );
 
    // Now the task can continue its function, but from this point on can only
    // access its stack and the ucOneKByte array (unless any other statically
    // defined or shared regions have been declared elsewhere).
}

xTaskCreateRestricted()

BaseType_t xTaskCreateRestricted	(	const TaskParameters_t *const	pxTaskDefinition,
		TaskHandle_t *	pxCreatedTask
	)

#include <task.h>

Create a new task and add it to the list of tasks that are ready to run. The function parameters define the memory regions and associated access permissions allocated to the task.

Note

xTaskCreateRestricted() should only be used in systems that include an MPU implementation.

Parameters

pxTaskDefinition	Pointer to a structure that contains a member for each of the normal xTaskCreate() parameters (see the xTaskCreate() API documentation) plus an optional stack buffer and the memory region definitions.
pxCreatedTask	Used to pass back a handle by which the created task can be referenced.

Returns

pdPASS if the task was successfully created and added to a ready list, otherwise an error code defined in the file projdefs.h

Example usage:

// Create an TaskParameters_t structure that defines the task to be created.
static const TaskParameters_t xCheckTaskParameters =
{
    vATask,     // pvTaskCode - the function that implements the task.
    "ATask",    // pcName - just a text name for the task to assist debugging.
    100,        // usStackDepth - the stack size DEFINED IN WORDS.
    NULL,       // pvParameters - passed into the task function as the function parameters.
    ( 1UL | portPRIVILEGE_BIT ),// uxPriority - task priority, set the portPRIVILEGE_BIT if the task should run in a privileged state.
    cStackBuffer,// puxStackBuffer - the buffer to be used as the task stack.
 
    // xRegions - Allocate up to three separate memory regions for access by
    // the task, with appropriate access permissions.  Different processors have
    // different memory alignment requirements - refer to the FreeRTOS documentation
    // for full information.
    {
        // Base address                 Length  Parameters
        { cReadWriteArray,              32,     portMPU_REGION_READ_WRITE },
        { cReadOnlyArray,               32,     portMPU_REGION_READ_ONLY },
        { cPrivilegedOnlyAccessArray,   128,    portMPU_REGION_PRIVILEGED_READ_WRITE }
    }
};
 
int main( void )
{
TaskHandle_t xHandle;
 
    // Create a task from the const structure defined above.  The task handle
    // is requested (the second parameter is not NULL) but in this case just for
    // demonstration purposes as its not actually used.
    xTaskCreateRestricted( &xRegTest1Parameters, &xHandle );
 
    // Start the scheduler.
    vTaskStartScheduler();
 
    // Will only get here if there was insufficient memory to create the idle
    // and/or timer task.
    for( ;; );
}