When eBPF pt_regs reads return garbage on the latest Linux kernels, blame Fred

Author here, yeah indeed. Earlier I was worried if eBPF verifier would even let me do plain integer arithmetic and then just use it as a struct pointer to an "arbitrary" kernel memory location, but it works.

Another research/testing area is whether I need to worry about memory ordering and possibly add some memory barriers, especially on ARM platform, as the eBPF task iterator passive sampler is an outside observer, periodically running on a different CPU, not injected to the context (and critical path!) of the monitored threads via tracepoints/probes.