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aaece95529
* Fix Tasks.c patch, line numbers were out of sync and patching was
broken.
* Add assumption to TaskCreate proof that a task's priority is less than
the configured max.
With the introduction of
9efe10b805
an assertion is added to ensure a new task's priority is less than the
confirmed max. The CBMC proof for TaskCreate needs to include this assumption
in order to not assert and fail. Since this is now enforced in the code
we can add an assumption to the proof that a task must be created with a
priority smaller than the configured max.
75 lines
4.1 KiB
Diff
75 lines
4.1 KiB
Diff
This patch removes the volatile qualifier from some global variable
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declarations in the tasks.c file. For task pool proofs, we are running
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`goto-instrument` with the `--nondet-volatile` flag on, which causes reads from
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volatile variable to be nondeterministic (i.e., any possible value can be
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returned). This is actually the desired behavior for volatile variables
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regarding verification purposes. However, this causes a lot of trouble when
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such variables are pointers, since one of the possible values we can get when
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dereferencing a volatile pointer is `NULL`.
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In the case of `uxPendedTicks`, a non-volatile copy of the variable is done
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before the following loop in tasks.c (lines 2231-2255):
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{
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UBaseType_t uxPendedCounts = uxPendedTicks; /* Non-volatile copy. */
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if( uxPendedCounts > ( UBaseType_t ) 0U )
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{
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do
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{
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if( xTaskIncrementTick() != pdFALSE )
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{
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xYieldPending = pdTRUE;
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}
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else
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{
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mtCOVERAGE_TEST_MARKER();
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}
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--uxPendedCounts;
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} while( uxPendedCounts > ( UBaseType_t ) 0U );
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uxPendedTicks = 0;
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}
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else
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{
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mtCOVERAGE_TEST_MARKER();
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}
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}
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Here, `uxPendedTicks` could return any value, making it impossible to unwind
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(or unroll) this loop in CBMC. Therefore, we require `uxPendedTicks` to behave
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as a regular variable so that the loop can be unwound.
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diff --git a/FreeRTOS/Source/tasks.c b/FreeRTOS/Source/tasks.c
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index c7be57cb2..9f76465d5 100644
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--- a/FreeRTOS/Source/tasks.c
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+++ b/FreeRTOS/Source/tasks.c
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@@ -296,7 +296,7 @@ typedef struct tskTaskControlBlock /* The old naming convention is used to
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#if ( configUSE_NEWLIB_REENTRANT == 1 )
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/* Allocate a Newlib reent structure that is specific to this task.
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- * Note Newlib support has been included by popular demand, but is not
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+ Note Newlib support has been included by popular demand, but is not
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* used by the FreeRTOS maintainers themselves. FreeRTOS is not
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* responsible for resulting newlib operation. User must be familiar with
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* newlib and must provide system-wide implementations of the necessary
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@@ -343,8 +343,8 @@ PRIVILEGED_DATA TCB_t * volatile pxCurrentTCB = NULL;
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PRIVILEGED_DATA static List_t pxReadyTasksLists[ configMAX_PRIORITIES ]; /*< Prioritised ready tasks. */
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PRIVILEGED_DATA static List_t xDelayedTaskList1; /*< Delayed tasks. */
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PRIVILEGED_DATA static List_t xDelayedTaskList2; /*< Delayed tasks (two lists are used - one for delays that have overflowed the current tick count. */
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-PRIVILEGED_DATA static List_t * volatile pxDelayedTaskList; /*< Points to the delayed task list currently being used. */
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-PRIVILEGED_DATA static List_t * volatile pxOverflowDelayedTaskList; /*< Points to the delayed task list currently being used to hold tasks that have overflowed the current tick count. */
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+PRIVILEGED_DATA static List_t * pxDelayedTaskList; /*< Points to the delayed task list currently being used. */
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+PRIVILEGED_DATA static List_t * pxOverflowDelayedTaskList; /*< Points to the delayed task list currently being used to hold tasks that have overflowed the current tick count. */
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PRIVILEGED_DATA static List_t xPendingReadyList; /*< Tasks that have been readied while the scheduler was suspended. They will be moved to the ready list when the scheduler is resumed. */
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#if ( INCLUDE_vTaskDelete == 1 )
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@@ -371,7 +371,7 @@ PRIVILEGED_DATA static volatile UBaseType_t uxCurrentNumberOfTasks = ( UBaseType
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PRIVILEGED_DATA static volatile TickType_t xTickCount = ( TickType_t ) configINITIAL_TICK_COUNT;
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PRIVILEGED_DATA static volatile UBaseType_t uxTopReadyPriority = tskIDLE_PRIORITY;
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PRIVILEGED_DATA static volatile BaseType_t xSchedulerRunning = pdFALSE;
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-PRIVILEGED_DATA static volatile TickType_t xPendedTicks = ( TickType_t ) 0U;
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+PRIVILEGED_DATA static TickType_t xPendedTicks = ( TickType_t ) 0U;
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PRIVILEGED_DATA static volatile BaseType_t xYieldPending = pdFALSE;
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PRIVILEGED_DATA static volatile BaseType_t xNumOfOverflows = ( BaseType_t ) 0;
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PRIVILEGED_DATA static UBaseType_t uxTaskNumber = ( UBaseType_t ) 0U;
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