STACKALIGN
fp = (struct sigframe *)STACKALIGN(fp);
tf = (struct trapframe *)STACKALIGN(tf);
limit = (struct callframe *)STACKALIGN(p->p_addr + USPACE -
fp = (struct sigframe *)STACKALIGN(fp);
tf->tf_sp = STACKALIGN(stack);
tf = (struct trapframe *)STACKALIGN(tf);
fp = (struct sigframe *)(STACKALIGN(fp - 1) - 288);
tf->fixreg[1] = STACKALIGN(stack);
tf->tf_sp = STACKALIGN(stack);
fp = (struct sigframe *)STACKALIGN(fp);
tf = (struct trapframe *)STACKALIGN(tf);
tf->tf_sp = STACKALIGN(stack);