The code in hotspot/src/share/vm/utilities/bitMap.inline.hpp
incorrectly swaps the usage of the idx_t and bm_word_t types. For most
platforms these 2 types are effectively the same, so the interchange is
uncaught, but on s390 (32-bit) the size_t is "unsigned long" which
makes it incompatible with "unsigned int". The patch is result of my
understanding of the logic inside bitMap.inline.hpp, so it needs
definitely a review although I think I'm right :-) The same patch is
used in our openjdk7 Fedora packages and the code compiles and works
without issue on both s390 and s390x architectures there.

from bitmap.hpp

  typedef size_t idx_t; // Type used for bit and word indices.
  typedef uintptr_t bm_word_t; // Element type of array that represents
                                // the bitmap.