Do I have a blown piston/ring?

I have an 88 Chevy Suburban with a 350. This morning I was driving and it starting making a knocking sound which sped up as I accelerated and slowed down as I decelerated. Then, white/grey smoke started billowing from under the hood a few seconds later. I'm talking HUGE amounts of smoke. I'm thinking it's a blown piston or ring, but the smoke wasn't blueish like it would be with burning oil, it was more white/light grey. Anyone know what it might be? Thanks!