freebsd4_sigframe
struct freebsd4_sigframe sf, *sfp;
sfp = (struct freebsd4_sigframe *)((uintptr_t)td->td_sigstk.ss_sp +
td->td_sigstk.ss_size - sizeof(struct freebsd4_sigframe));
sfp = (struct freebsd4_sigframe *)regs->tf_esp - 1;
ASSYM(SIGF_UC4, offsetof(struct freebsd4_sigframe, sf_uc));