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发表于 2020-2-20 15:42:08
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FreeRTOS-MPU Features
Compatible with the standard ARM Cortex-M3 and Cortex-M4F ports.
Tasks can be created to run in either Privileged mode or User mode. User mode tasks can only access their own stack and up to three user definable memory regions (three per task). User definable memory regions are assigned to tasks when the task is created, and can be reconfigured at run time if required.
User definable memory regions can be parameterised individually. For example, some regions may be set to read only, while others may be set to not executable (execute never, or simply XN, in ARM terminology), etc.
No data memory is shared between User mode tasks, but User mode tasks can pass messages to each other using the standard queue and semaphore mechanisms. Shared memory regions can be explicitly created by using a user definable memory region but this is discouraged.
A Privileged mode task can set itself into User mode, but once in User mode it cannot set itself back to Privileged mode.
The FreeRTOS API is located in a region of Flash that can only be accessed while the microcontroller is in Privileged mode (calling an API function causes a temporary switch to Privilege mode).
The data maintained by the RTOS kernel (all non stack data that is private to the FreeRTOS source files) is located in a region of RAM that can only be accessed while the microcontroller is in Privileged mode.
System peripherals can only be accessed while the microcontroller is in Privileged mode. Standard peripherals (UARTs, etc.) are accessible by any code but can be explicitly protected using a user definable memory region.
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发表于 2020-2-13 01:40:19
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