let g:ctrlp_map = ''

function! CtrlP()
  if (getcwd() == $HOME)
    echo "Won't run in ~"
    return
  endif
  if (getcwd() == '/')
    echo "Won't run in /"
    return
  endif
  CtrlP
endfunction

nnoremap <C-p> :call CtrlP()<CR>