  We show that in IIB string theory and for D1D5p black holes in ten dimensions
the method of entropy function works. Despite the more complicated Wald formula
for the entropy of D1D5p black holes in ten dimensions, their entropy is given
by entropy function at its extremum point. We use this method for computing the
entropy of the system both at the level of supergravity and for its higher
order alpha'^3R^4 corrections.
