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Architectures are expected to know if AUX area sampling is supported by
the hardware. Add a function perf_can_aux_sample() which will determine
whether the kernel supports it.

Committer notes:

I reported that this message was taking place on a kernel without the
required bits:

  # perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
  Error:
  The sys_perf_event_open() syscall returned with 7 (Argument list too long) for event (branch-misses:u).
  /bin/dmesg | grep -i perf may provide additional information.

Adrian sent a patch addressing it, with this explanation:

 ----
  perf_can_aux_sample_size() always returned true because it did not pass
  the attribute size to sys_perf_event_open, nor correctly check the
  return value and errno.
 ----

After applying it I get, later in the series, when --aux-sample is
added:

  # perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
  AUX area sampling is not supported by kernel
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20191115124225.5247-4-adrian.hunter@intel.com

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>