vTaskAllocateMPURegions
[FreeRTOS-MPU 特定]

task. h

void vTaskAllocateMPURegions(
               TaskHandle_t xTaskToModify,
               const MemoryRegion_t * const xRegions );

调用 xTaskCreateRestricted() 创建任务时，将内存区域分配给受限制的任务。然后，可以在运行时使用 vTaskAllocateMPURegions() 修改或重新定义区域。

vTaskAllocateMPURegions() 旨在与 FreeRTOS-MPU 配合使用，其演示应用程序包含正在使用的 vTaskAllocateMPURegions() 示例。

参数：

xTask

正在更新的任务的句柄。

xRegions

指向 MemoryRegion_t 结构体数组的指针，每个结构体都包含一个新的内存区域定义。应使用常量 portNUM_configurable_region 确定数组的大小，在 ARM Cortex-M3 上，该常量设置为 3。

MemoryRegion_t 在 task.h 中定义为：

typedef struct xMEMORY_REGION
{
    void *pvBaseAddress;
    unsigned long ulLengthInBytes;
    unsigned long ulParameters;
} MemoryRegion_t;

PvBaseAddress 和 ulLengthInBytes 成员分别作为内存区域的开始和内存区域的长度。必须指出，MPU 必须满足一些约束条件，特别是每个区域的大小和对齐方式必须都等于两个值的同底数幂。

ulParameters 定义任务并且可以采用以下值中的 OR：

    portMPU_REGION_READ_WRITE
    portMPU_REGION_PRIVILEGED_READ_ONLY
    portMPU_REGION_READ_ONLY
    portMPU_REGION_PRIVILEGED_READ_WRITE
    portMPU_REGION_CACHEABLE_BUFFERABLE
    portMPU_REGION_EXECUTE_NEVER

使用示例（请参阅FreeRTOS - MPU 演示应用程序了解更完整、更全面的示例）：



/* Define an array that the task will both read from and write to.  Make sure
the size and alignment are appropriate for an MPU region (note this uses GCC
syntax). */
static unsigned char ucOneKByte[ 1024 ] __attribute__((align( 1024 )));

/* 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). */
}

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vTaskAllocateMPURegions [FreeRTOS-MPU 特定]

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vTaskAllocateMPURegions
[FreeRTOS-MPU 特定]