mdb_amd64_next
extern int mdb_amd64_next(mdb_tgt_t *, uintptr_t *, kreg_t, mdb_instr_t);
#define mdb_isa_next mdb_amd64_next
return (mdb_amd64_next(t, p, psp->pr_reg[REG_RIP], pt_read_instr(t)));