xiaoxiang781216 commented on a change in pull request #1562:
URL: https://github.com/apache/incubator-nuttx/pull/1562#discussion_r472870570
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File path: arch/arm/src/common/arm_usestack.c
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@@ -105,51 +102,54 @@ int up_use_stack(struct tcb_s *tcb, void *stack, size_t
stack_size)
up_release_stack(tcb, tcb->flags & TCB_FLAG_TTYPE_MASK);
}
+ /* The ARM uses a push-down stack: the stack grows toward lower
+ * addresses in memory. The stack pointer register, points to
+ * the lowest, valid work address (the "top" of the stack). Items
+ * on the stack are referenced as positive word offsets from sp.
+ */
+
+ /* We align all sizes and pointer to CONFIG_STACK_ALIGNMENT.
+ * Since the stack ptr is decremented before
+ * the first write, we can directly save our variables to struct
+ * tcb_s.
+ */
+
/* Save the new stack allocation */
tcb->stack_alloc_ptr = stack;
- /* The ARM uses a push-down stack: the stack grows toward lower addresses
- * in memory. The stack pointer register, points to the lowest, valid
- * work address (the "top" of the stack). Items on the stack are
- * referenced as positive word offsets from sp.
- */
+ /* Align stack top */
- top_of_stack = (uint32_t)tcb->stack_alloc_ptr + stack_size - 4;
+ tcb->adj_stack_ptr =
+ (FAR void *)STACK_ALIGN_DOWN((uintptr_t)stack + stack_size);
- /* The ARM stack must be aligned to 8-byte alignment for EABI.
- * If necessary top_of_stack must be rounded down to the next
- * boundary
- */
+ /* Offset by tls_size */
- top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
+ stack = (FAR void *)((uintptr_t)stack + sizeof(struct tls_info_s));
- /* The size of the stack in bytes is then the difference between
- * the top and the bottom of the stack (+4 because if the top
- * is the same as the bottom, then the size is one 32-bit element).
- * The size need not be aligned.
- */
+ /* Is there enough room for at least TLS ? */
- size_of_stack = top_of_stack - (uint32_t)tcb->stack_alloc_ptr + 4;
+ if ((uintptr_t)stack <= (uintptr_t)tcb->adj_stack_ptr)
Review comment:
could we change to:
```
if ((uintptr_t)stack > (uintptr_t)tcb->adj_stack_ptr)
{
return -ENOMEM;
}
```
to mininize the code change.
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