diff options
Diffstat (limited to 'FreeRTOS-Plus/Test/CBMC/patches/0005-Remove-volatile-qualifier-from-tasks-variables.patch')
| -rw-r--r-- | FreeRTOS-Plus/Test/CBMC/patches/0005-Remove-volatile-qualifier-from-tasks-variables.patch | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/FreeRTOS-Plus/Test/CBMC/patches/0005-Remove-volatile-qualifier-from-tasks-variables.patch b/FreeRTOS-Plus/Test/CBMC/patches/0005-Remove-volatile-qualifier-from-tasks-variables.patch new file mode 100644 index 000000000..29cde0e77 --- /dev/null +++ b/FreeRTOS-Plus/Test/CBMC/patches/0005-Remove-volatile-qualifier-from-tasks-variables.patch @@ -0,0 +1,79 @@ +This patch removes the volatile qualifier from some global variable +declarations in the tasks.c file. For task pool proofs, we are running +`goto-instrument` with the `--nondet-volatile` flag on, which causes reads from +volatile variable to be nondeterministic (i.e., any possible value can be +returned). This is actually the desired behavior for volatile variables +regarding verification purposes. However, this causes a lot of trouble when +such variables are pointers, since one of the possible values we can get when +dereferencing a volatile pointer is `NULL`. + +In the case of `uxPendedTicks`, a non-volatile copy of the variable is done +before the following loop in tasks.c (lines 2231-2255): + +{ + UBaseType_t uxPendedCounts = uxPendedTicks; /* Non-volatile copy. */ + + if( uxPendedCounts > ( UBaseType_t ) 0U ) + { + do + { + if( xTaskIncrementTick() != pdFALSE ) + { + xYieldPending = pdTRUE; + } + else + { + mtCOVERAGE_TEST_MARKER(); + } + --uxPendedCounts; + } while( uxPendedCounts > ( UBaseType_t ) 0U ); + + uxPendedTicks = 0; + } + else + { + mtCOVERAGE_TEST_MARKER(); + } +} + +Here, `uxPendedTicks` could return any value, making it impossible to unwind +(or unroll) this loop in CBMC. Therefore, we require `uxPendedTicks` to behave +as a regular variable so that the loop can be unwound. + +--- +diff --git a/FreeRTOS/Source/tasks.c b/FreeRTOS/Source/tasks.c +index ff657733..8b57d198 100644 +--- a/FreeRTOS/Source/tasks.c ++++ b/FreeRTOS/Source/tasks.c +@@ -331,7 +331,7 @@ typedef tskTCB TCB_t; + + /*lint -save -e956 A manual analysis and inspection has been used to determine + which static variables must be declared volatile. */ +-PRIVILEGED_DATA TCB_t * volatile pxCurrentTCB = NULL; ++PRIVILEGED_DATA TCB_t * pxCurrentTCB = NULL; + + /* Lists for ready and blocked tasks. -------------------- + xDelayedTaskList1 and xDelayedTaskList2 could be move to function scople but +@@ -340,8 +340,8 @@ the static qualifier. */ + PRIVILEGED_DATA static List_t pxReadyTasksLists[ configMAX_PRIORITIES ];/*< Prioritised ready tasks. */ + PRIVILEGED_DATA static List_t xDelayedTaskList1; /*< Delayed tasks. */ + PRIVILEGED_DATA static List_t xDelayedTaskList2; /*< Delayed tasks (two lists are used - one for delays that have overflowed the current tick count. */ +-PRIVILEGED_DATA static List_t * volatile pxDelayedTaskList; /*< Points to the delayed task list currently being used. */ +-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. */ ++PRIVILEGED_DATA static List_t * pxDelayedTaskList; /*< Points to the delayed task list currently being used. */ ++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. */ + 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. */ + + #if( INCLUDE_vTaskDelete == 1 ) +@@ -368,10 +368,10 @@ PRIVILEGED_DATA static volatile UBaseType_t uxCurrentNumberOfTasks = ( UBaseTyp + + /* Other file private variables. --------------------------------*/ + PRIVILEGED_DATA static volatile UBaseType_t uxCurrentNumberOfTasks = ( UBaseType_t ) 0U; + PRIVILEGED_DATA static volatile TickType_t xTickCount = ( TickType_t ) configINITIAL_TICK_COUNT; + PRIVILEGED_DATA static volatile UBaseType_t uxTopReadyPriority = tskIDLE_PRIORITY; + PRIVILEGED_DATA static volatile BaseType_t xSchedulerRunning = pdFALSE; +-PRIVILEGED_DATA static volatile TickType_t xPendedTicks = ( TickType_t ) 0U; ++PRIVILEGED_DATA static TickType_t xPendedTicks = ( TickType_t ) 0U; + PRIVILEGED_DATA static volatile BaseType_t xYieldPending = pdFALSE; + PRIVILEGED_DATA static volatile BaseType_t xNumOfOverflows = ( BaseType_t ) 0; + PRIVILEGED_DATA static UBaseType_t uxTaskNumber = ( UBaseType_t ) 0U; |