static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
{
	unsigned long vm_start = vma->vm_start;

	if (vma->vm_flags & VM_GROWSDOWN) {
		vm_start -= stack_guard_gap;
		if (vm_start > vma->vm_start)
			vm_start = 0;
	}
	return vm_start;
}
Unknown