  We present a counting of microstates of a class of dyonic BPS black holes in
AdS$_4$ which precisely reproduces their Bekenstein-Hawking entropy. The
counting is performed in the dual boundary description, that provides a
non-perturbative definition of quantum gravity, in terms of a twisted and
mass-deformed ABJM theory. We evaluate its twisted index and propose an
extremization principle to extract the entropy, which reproduces the attractor
mechanism in gauged supergravity.
