On 02/03/2021 20:47, Kinsey Moore wrote:
Enforce alignment of the stack begin and end by allocating enough stack
area that the desired size can be aligned to CPU_STACK_ALIGNMENT. This
also ensures that the space reserved for TLS data falls on stack
alignment boundaries which satisfies TLS alignment requirements.
---
cpukit/rtems/src/taskcreate.c | 5 ++++-
cpukit/score/src/threadinitialize.c | 8 +++++---
cpukit/score/src/tlsallocsize.c | 22 ++++++++++++++--------
3 files changed, 23 insertions(+), 12 deletions(-)
diff --git a/cpukit/rtems/src/taskcreate.c b/cpukit/rtems/src/taskcreate.c
index c065a159c6..bad13cb532 100644
--- a/cpukit/rtems/src/taskcreate.c
+++ b/cpukit/rtems/src/taskcreate.c
@@ -53,8 +53,11 @@ static rtems_status_code
_RTEMS_tasks_Allocate_and_prepare_stack(
thread_config->stack_free = _Stack_Free;
size = _Stack_Ensure_minimum( config->storage_size );
size = _Stack_Extend_size( size, thread_config->is_fp );
+ size = RTEMS_ALIGN_UP( size, CPU_STACK_ALIGNMENT );
This can overflow. It needs to move into _Stack_Extend_size() which
performs overflow handling. I think we need the following invariants
which should be checked by static assertions (if not already done):
CPU_STACK_ALIGNMENT is a power of two
CPU_HEAP_ALIGNMENT is a power of two
CPU_STACK_ALIGNMENT >= CPU_HEAP_ALIGNMENT
The _Stack_Extend_size() should add CPU_STACK_ALIGNMENT - 1 to the size.
thread_config->stack_size = size;
- thread_config->stack_area = _Stack_Allocate( size );
+
+ /* Allocate enough stack space to enforce alignment on use */
+ thread_config->stack_area = _Stack_Allocate( size + CPU_STACK_ALIGNMENT - 1
);
We don't need this change with the modified _Stack_Extend_size().
if ( thread_config->stack_area == NULL ) {
return RTEMS_UNSATISFIED;
diff --git a/cpukit/score/src/threadinitialize.c
b/cpukit/score/src/threadinitialize.c
index 05c30c3d43..04f62df4de 100644
--- a/cpukit/score/src/threadinitialize.c
+++ b/cpukit/score/src/threadinitialize.c
@@ -84,7 +84,9 @@ bool _Thread_Initialize(
}
#endif
- stack_begin = config->stack_area;
+ /* There is guaranteed to be enough space allocated to enforce alignment */
+ stack_begin = (void * const) RTEMS_ALIGN_UP( (uintptr_t) config->stack_area,
const?
stack_begin is a char pointer.
+ CPU_STACK_ALIGNMENT );
Placement of ( ) and arguments wrong.
stack_end = stack_begin + config->stack_size;
/* Allocate floating-point context in stack area */
@@ -104,8 +106,8 @@ bool _Thread_Initialize(
stack_end -= tls_size;
tls_align = (uintptr_t) _TLS_Alignment;
- the_thread->Start.tls_area = (void *)
- ( ( (uintptr_t) stack_end + tls_align - 1 ) & ~( tls_align - 1 ) );
+ the_thread->Start.tls_area =
+ (void *)RTEMS_ALIGN_UP( (uintptr_t)stack_end, tls_align );
' ' between the casts. This change is an unrelated clean up. It should
be in a separate patch.
}
_Stack_Initialize(
diff --git a/cpukit/score/src/tlsallocsize.c b/cpukit/score/src/tlsallocsize.c
index e7854c677a..0a7ff7d27a 100644
--- a/cpukit/score/src/tlsallocsize.c
+++ b/cpukit/score/src/tlsallocsize.c
@@ -62,23 +62,29 @@ uintptr_t _TLS_Get_allocation_size( void )
allocation_size = _TLS_Heap_align_up( size );
alignment = _TLS_Heap_align_up( (uintptr_t) _TLS_Alignment );
- /*
- * The stack allocator does not support aligned allocations. Allocate
- * enough to do the alignment manually.
- */
- if ( alignment > CPU_HEAP_ALIGNMENT ) {
- allocation_size += alignment;
- }
-
allocation_size += _TLS_Get_thread_control_block_area_size( alignment );
#ifndef __i386__
allocation_size += sizeof(TLS_Dynamic_thread_vector);
#endif
+ /*
+ * Increase the TLS allocation size to the stack alignment requirements
+ * since it is pulled from the top of the stack allocation. This preserves
+ * the alignment of the top of the stack.
+ */
+ allocation_size = RTEMS_ALIGN_UP( allocation_size, CPU_STACK_ALIGNMENT );
+
if ( _Thread_Maximum_TLS_size != 0 ) {
if ( allocation_size <= _Thread_Maximum_TLS_size ) {
allocation_size = _Thread_Maximum_TLS_size;
+
+ /*
+ * Decrease the TLS allocation size to the stack alignment requirements
+ * since the TLS area has reached maximum size.
+ */
+ allocation_size =
+ RTEMS_ALIGN_DOWN( allocation_size, CPU_STACK_ALIGNMENT );
I think we should enforce that _Thread_Maximum_TLS_size is an integral
multiple of RTEMS_TASK_STORAGE_ALIGNMENT (which needs to be fixed as well).
} else {
_Internal_error( INTERNAL_ERROR_TOO_LARGE_TLS_SIZE );
}
--
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