$ cat /tmp/foo.d
#!/usr/sbin/dtrace -s
proc:::signal-send
/execname == "sshd"/
{
    printf("Pid: %d Signal: %d To pid: %d\n", pid, args[2], args[1]->pr_pid);
    ustack();
}

$ /tmp/foo.d
dtrace: script '/tmp/foo.d' matched 1 probe
CPU     ID                    FUNCTION:NAME
  2  15293            sigtoproc:signal-send Pid: 19849 Signal: 11 To pid: 19849