The x86 `syscall` instruction stores the return address into `rcx` as well as `RFLAGS` into `r11`. These are unconditionally clobbered and thus cannot be saved

The x86 `syscall` instruction stores the return address into `rcx` as well as `RFLAGS` into `r11`. These are unconditionally clobbered and thus cannot be saved or used in a `syscall` transition.