SSTATUS_SPP
#define CLKF_USERMODE(frame) ((frame->tf_sstatus & SSTATUS_SPP) == 0)
KASSERTMSG((csr_read(sstatus) & (SSTATUS_SPP | SSTATUS_SIE)) == 0,
KASSERTMSG((csr_read(sstatus) & (SSTATUS_SPP | SSTATUS_SIE)) ==
SSTATUS_SPP, "Came from S mode with interrupts enabled");
tf->tf_sstatus &= ~(SSTATUS_SPP); /* Enter user mode. */