hwtracer assumes that any decoder can decode a trace from any collector.

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This is not strictly correct. Depending on the platform, Linux perf can collect different kinds of traces. For example on ARM perf can collect coresight traces instead of Intel PT traces.

If we supported collecting coresight traces (we don't any trace is currently assumed to be an Intel PT trace), hwtracer would happily let us pass a coresight trace to the libipt decoder.

I wonder if the Trace trait should have a fn format() -> TraceFormat which is checked.