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Actually, triggering rowhammer-induced bit flips does not require knowing the memory geometry. It is possible to trigger bit flips just by picking random pairs of addresses to hammer. See the README file at https://github.com/mseaborn/rowhammer-test.
Here is a program for testing for the DRAM rowhammer problem which runs as a normal userland process: https://github.com/mseaborn/rowhammer-test
Note that for the test to do row hammering effectively, it must pick two addresses that are in different rows but in the same bank. A good way of doing that is just to pick random pairs of addresses. If your machine has 16 banks of DRAM, for example (as various machines I've tested do), there should be a 1/16 chance that the two addresses are in the same bank. This is what the test above does. (Actually, it picks >2 addresses to hammer per iteration.)
Be careful about running the test, because on machines that are susceptible to rowhammer, it could cause bit flips that crash the machine (or worse, bit flips in data that gets written back to disc).