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Fix undefined behavior in uxSchedulerCoreMask initialization and clamping logic

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Kuoping Hsu 2026-05-15 20:37:20 +08:00
parent 4f32c359ef
commit 54c3e971da
1 changed files with 14 additions and 4 deletions
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18
tasks.c
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@ -515,8 +515,14 @@ PRIVILEGED_DATA static TaskHandle_t xIdleTaskHandles[ configNUMBER_OF_CORES ];
/* Global scheduler core mask. Bit N = 1 means core N is allowed to run
* non-idle tasks. Defaults to all cores enabled. Use
* vTaskSetSchedulerCoreMask() / uxTaskGetSchedulerCoreMask() to change it
* at run time. */
PRIVILEGED_DATA static volatile UBaseType_t uxSchedulerCoreMask = ( UBaseType_t ) ( ( 1UL << configNUMBER_OF_CORES ) - 1UL );
* at run time.
*
* The mask is derived by right-shifting ~0 rather than left-shifting 1,
* because left-shifting by a value equal to the type width is undefined
* behaviour in C (C11 §6.5.7). Using UBaseType_t throughout also avoids
* the assumption that unsigned long is at least as wide as UBaseType_t. */
PRIVILEGED_DATA static volatile UBaseType_t uxSchedulerCoreMask =
( ( UBaseType_t ) ( ~( UBaseType_t ) 0U ) >> ( ( sizeof( UBaseType_t ) * ( size_t ) 8U ) - ( size_t ) configNUMBER_OF_CORES ) );
#endif /* #if ( ( configNUMBER_OF_CORES > 1 ) && ( configUSE_SCHEDULER_CORE_MASK == 1 ) ) */
/* Improve support for OpenOCD. The kernel tracks Ready tasks via priority lists.
@ -3141,8 +3147,12 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
{
uxOldMask = uxSchedulerCoreMask;
/* Clamp to the number of physical cores so stray bits are ignored. */
uxSchedulerCoreMask = uxCoreMask & ( UBaseType_t ) ( ( 1UL << configNUMBER_OF_CORES ) - 1UL );
/* Clamp to the number of physical cores so stray bits are ignored.
* The valid-core mask is derived by right-shifting ~0 to avoid
* left-shift UB and unsigned long width assumptions (see the
* uxSchedulerCoreMask initialiser for a full explanation). */
uxSchedulerCoreMask = uxCoreMask &
( ( UBaseType_t ) ( ~( UBaseType_t ) 0U ) >> ( ( sizeof( UBaseType_t ) * ( size_t ) 8U ) - ( size_t ) configNUMBER_OF_CORES ) );
if( xSchedulerRunning != pdFALSE )
{