RFR 8224676: Java crash if VSYSCALL is missing

[Florian Weimer]

* Vladimir Kempik:

> This patch remove VSYSCALL functionality and does perform simple asm
> instruction to get cpu id.

I don't think this is future-proof because the kernel may store the CPU
number in another way and update the code in the vDSO accordingly.
Using the segment limit is an implementation detail.

Is there a reason why you can't call sched_getcpu?  Is it too slow?

Thanks,
Florian