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Memory Protection Unit (MPU) Enhancements (#705)

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Memory Protection Unit (MPU) Enhancements

This commit introduces a new MPU wrapper that places additional
restrictions on unprivileged tasks. The following is the list of changes
introduced with the new MPU wrapper:

1. Opaque and indirectly verifiable integers for kernel object handles:
   All the kernel object handles (for example, queue handles) are now
   opaque integers. Previously object handles were raw pointers.

2. Saving the task context in Task Control Block (TCB): When a task is
   swapped out by the scheduler, the task's context is now saved in its
   TCB. Previously the task's context was saved on its stack.

3. Execute system calls on a separate privileged only stack: FreeRTOS
   system calls, which execute with elevated privilege, now use a
   separate privileged only stack. Previously system calls used the
   calling task's stack. The application writer can control the size of
   the system call stack using new configSYSTEM_CALL_STACK_SIZE config
   macro.

4. Memory bounds checks: FreeRTOS system calls which accept a pointer
   and de-reference it, now verify that the calling task has required
   permissions to access the memory location referenced by the pointer.

5. System call restrictions: The following system calls are no longer
   available to unprivileged tasks:
    - vQueueDelete
    - xQueueCreateMutex
    - xQueueCreateMutexStatic
    - xQueueCreateCountingSemaphore
    - xQueueCreateCountingSemaphoreStatic
    - xQueueGenericCreate
    - xQueueGenericCreateStatic
    - xQueueCreateSet
    - xQueueRemoveFromSet
    - xQueueGenericReset
    - xTaskCreate
    - xTaskCreateStatic
    - vTaskDelete
    - vTaskPrioritySet
    - vTaskSuspendAll
    - xTaskResumeAll
    - xTaskGetHandle
    - xTaskCallApplicationTaskHook
    - vTaskList
    - vTaskGetRunTimeStats
    - xTaskCatchUpTicks
    - xEventGroupCreate
    - xEventGroupCreateStatic
    - vEventGroupDelete
    - xStreamBufferGenericCreate
    - xStreamBufferGenericCreateStatic
    - vStreamBufferDelete
    - xStreamBufferReset
   Also, an unprivileged task can no longer use vTaskSuspend to suspend
   any task other than itself.

We thank the following people for their inputs in these enhancements:
- David Reiss of Meta Platforms, Inc.
- Lan Luo, Xinhui Shao, Yumeng Wei, Zixia Liu, Huaiyu Yan and Zhen Ling
  of School of Computer Science and Engineering, Southeast University,
  China.
- Xinwen Fu of Department of Computer Science, University of
  Massachusetts Lowell, USA.
- Yuequi Chen, Zicheng Wang, Minghao Lin of University of Colorado
  Boulder, USA.
This commit is contained in:
kar-rahul-aws 2023-07-13 16:51:04 +05:30 • committed by GitHub
parent 18e2937239
commit 97050a17aa
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GPG key ID: 4AEE18F83AFDEB23
123 changed files with 94802 additions and 6515 deletions
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21
tasks.c
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@ -975,17 +975,17 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
{
#if ( portSTACK_GROWTH < 0 )
{
pxNewTCB->pxTopOfStack = pxPortInitialiseStack( pxTopOfStack, pxNewTCB->pxStack, pxTaskCode, pvParameters, xRunPrivileged );
pxNewTCB->pxTopOfStack = pxPortInitialiseStack( pxTopOfStack, pxNewTCB->pxStack, pxTaskCode, pvParameters, xRunPrivileged, &( pxNewTCB->xMPUSettings ) );
}
#else /* portSTACK_GROWTH */
{
pxNewTCB->pxTopOfStack = pxPortInitialiseStack( pxTopOfStack, pxNewTCB->pxEndOfStack, pxTaskCode, pvParameters, xRunPrivileged );
pxNewTCB->pxTopOfStack = pxPortInitialiseStack( pxTopOfStack, pxNewTCB->pxEndOfStack, pxTaskCode, pvParameters, xRunPrivileged, &( pxNewTCB->xMPUSettings ) );
}
#endif /* portSTACK_GROWTH */
}
#else /* portHAS_STACK_OVERFLOW_CHECKING */
{
pxNewTCB->pxTopOfStack = pxPortInitialiseStack( pxTopOfStack, pxTaskCode, pvParameters, xRunPrivileged );
pxNewTCB->pxTopOfStack = pxPortInitialiseStack( pxTopOfStack, pxTaskCode, pvParameters, xRunPrivileged, &( pxNewTCB->xMPUSettings ) );
}
#endif /* portHAS_STACK_OVERFLOW_CHECKING */
}
@ -5493,6 +5493,21 @@ static void prvAddCurrentTaskToDelayedList( TickType_t xTicksToWait,
}
#endif /* INCLUDE_vTaskSuspend */
}
/*-----------------------------------------------------------*/
#if ( portUSING_MPU_WRAPPERS == 1 )
xMPU_SETTINGS * xTaskGetMPUSettings( TaskHandle_t xTask )
{
TCB_t * pxTCB;
pxTCB = prvGetTCBFromHandle( xTask );
return &( pxTCB->xMPUSettings );
}
#endif /* portUSING_MPU_WRAPPERS */
/*-----------------------------------------------------------*/
/* Code below here allows additional code to be inserted into this source file,
* especially where access to file scope functions and data is needed (for example