syscall_fancy
void syscall_fancy(struct lwp *, u_int64_t, struct trapframe *);
p->p_md.md_syscall = syscall_fancy;
p->p_md.md_syscall = syscall_fancy;
p->p_md.md_syscall = syscall_fancy;
static void syscall_fancy(register_t, struct lwp *, struct frame *);