[PATCH v1 1/2] score: Enforce stack_end alignment

[Sebastian Huber]

On 19/02/2021 07:12, Sebastian Huber wrote:

> On 18/02/2021 19:59, Kinsey Moore wrote:
>
>> The size of the reserved TLS space is not guaranteed to adhere to stack
>> alignment requirements which can cause stack_end to become misaligned.
>> This enforces the alignment of stack_end.
>> ---
>>   cpukit/score/src/threadinitialize.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/cpukit/score/src/threadinitialize.c 
>> b/cpukit/score/src/threadinitialize.c
>> index 05c30c3d43..ad5dccbbb2 100644
>> --- a/cpukit/score/src/threadinitialize.c
>> +++ b/cpukit/score/src/threadinitialize.c
>> @@ -108,6 +108,10 @@ bool _Thread_Initialize(
>>         ( ( (uintptr_t) stack_end + tls_align - 1 ) & ~( tls_align - 
>> 1 ) );
>>     }
>>   +  /* Enforce stack alignment */
>> +  stack_end = (char *)((uintptr_t) stack_end &
>> +    ~( (uintptr_t) CPU_STACK_ALIGNMENT - 1 ));
>> +
>>     _Stack_Initialize(
>>       &the_thread->Start.Initial_stack,
>>       stack_begin,
> I think the bug is in _TLS_Get_allocation_size(). It assumes 
> CPU_HEAP_ALIGNMENT >= CPU_STACK_ALIGNMENT. It should probably use the 
> maximum of these two values.

There is also an issue in the stack allocation, for example

static rtems_status_code _RTEMS_tasks_Allocate_and_prepare_stack(
   Thread_Configuration    *thread_config,
   const rtems_task_config *config
)
{
   size_t size;

   thread_config->stack_free = _Stack_Free;
   size = _Stack_Ensure_minimum( config->storage_size );
   size = _Stack_Extend_size( size, thread_config->is_fp );
   thread_config->stack_size = size;
   thread_config->stack_area = _Stack_Allocate( size );

   if ( thread_config->stack_area == NULL ) {
     return RTEMS_UNSATISFIED;
   }

   return RTEMS_SUCCESSFUL;
}

and

/* Generated from spec:/rtems/task/if/storage-alignment */

/**
  * @ingroup RTEMSAPIClassicTasks
  *
  * @brief This constant defines the recommended alignment of a task storage
  *   area in bytes.
  *
  * @par Notes
  * Use it with RTEMS_ALIGNED() to define the alignment of a statically
  * allocated task storage area.
  */
#define RTEMS_TASK_STORAGE_ALIGNMENT CPU_HEAP_ALIGNMENT

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