Passive form of "Who knows what to do?"

Question

Who knows what to do?

How to make it in a passive form?

Actually, I am confused. I changed it like this.

What to do is known to whom?

Is correct? What about these?

What to do is known to by whom?
What to do is known by whom?

Please correct me.

Answer 1

There are two verbs in the sentence: knows and do. You've tried to change knows into passive voice, and all of those sentences are very awkward.

On the other hand, making do passive works:

Who knows what is to be done?

Answer 2

A less awkward example could be:

By whom is it known what to do?

or,

To whom is it known what to do?

But still, if you really (that's a big IF) need to switch it to a passive voice, I believe 200_success's answer is best.