Question: 

I wanted to know if the buying and selling of shares is permissible, but for that companies that primary source of income is the 'sale' of halaal good, eg petrol, phones, clothing.

Is the dividends earned on said shares halaal too?

If not, could I please have the reasoning behind the fatwa?

I know that the buying of selling of shares of banks, and financial institutions which main source of income is through futures and interest is not permissible.