This patch removes the old error-prone way of tracking
whether the tracepoint is for a function entry or
return. Instead of trying to guess, let the data structure
simply tell us directly.
This patch enables the eBPF tracer backend to parse the ID of the
Goroutine which hit the uprobe. This implementation is specific to AMD64
and will have to be generalized further in order to be used on other
architectures.
