- TopOfStack = BaseOfStack + EFI_SIZE_TO_PAGES (STACK_SIZE) * EFI_PAGE_SIZE - CPU_STACK_ALIGNMENT;\r
- TopOfStack = (EFI_PHYSICAL_ADDRESS) ALIGN_POINTER (TopOfStack, CPU_STACK_ALIGNMENT);\r
+ // The first four parameters to a function are passed in rcx, rdx, r8 and r9. \r
+ // Any further parameters are pushed on the stack. Furthermore, space (4 * 8bytes) for the \r
+ // register parameters is reserved on the stack, in case the called function \r
+ // wants to spill them; this is important if the function is variadic. \r
+ //\r
+ TopOfStack = BaseOfStack + EFI_SIZE_TO_PAGES (STACK_SIZE) * EFI_PAGE_SIZE - 32;\r
+\r
+ //\r
+ // X64 Calling Conventions requires that the stack must be aligned to 16 bytes\r
+ //\r
+ TopOfStack = (EFI_PHYSICAL_ADDRESS) (UINTN) ALIGN_POINTER (TopOfStack, 16);\r