tools/testing/selftests/vm/map_fixed_noreplace.c: add test for MAP_FIXED_NOREPLACE

tools/testing/selftests/vm/map_fixed_noreplace.c: add test for MAP_FIXED_NOREPLACE

Add a test for MAP_FIXED_NOREPLACE, based on some code originally by Jann
Horn.  This would have caught the overlap bug reported by Daniel Micay.

I originally suggested to Michal that we create MAP_FIXED_NOREPLACE, but
instead of writing a selftest I spent my time bike-shedding whether it
should be called MAP_FIXED_SAFE/NOCLOBBER/WEAK/NEW ..  mea culpa.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michael Ellerman <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Khalid Aziz <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Florian Weimer <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Abdul Haleem <[email protected]>
Cc: Joel Stanley <[email protected]>
Cc: Jason Evans <[email protected]>
Cc: David Goldblatt <[email protected]>
Cc: Daniel Micay <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>