PSR_SS
if (regs->tf_spsr & PSR_SS) {
tf->tf_spsr |= PSR_SS;
tf->tf_spsr &= ~PSR_SS;
#define db_clear_single_step(regs) ((regs)->tf_spsr &= ~PSR_SS)
#define db_set_single_step(regs) ((regs)->tf_spsr |= PSR_SS)