these two patches convert the s390 architecture to generic VDSO. The first patch adds an option to add architecture specific information to struct vdso_data. We need that information because the old s390 assembly code had a steering capability, which steered the clock slowly. To emulate that behaviour we need to add the steering offset to struct vdso_data.
This requirements results in the need for a seqlock kind of lock, which is implemented open-coded in __arch_get_hw_counter(). open-coded because we cannot include seqlock.h in userspace code (and using the normal seqlock interface on kernel side might result in people changing struct seqlock, but not changing the vdso userspace part), therefore both sides are open-coded. I think in theory we could also call vdso_write_begin()/ vdso_write_end(). What do you think? If there are no objections we would carry both patches through the s390 tree. Thanks Sven
