perf script: Add generic perl handler to process events

perf script: Add generic perl handler to process events

The current perf scripting facility only supports tracepoints. This
patch implements a generic perl handler to support other events than
tracepoints too.

This patch introduces a function process_event() that is called by
perf for each sample. The function is called with byte streams as
arguments containing information about the event, its attributes, the
sample and raw data. Perl's unpack() function can easily be used for
byte decoding. The following is the default implementation for
process_event() that can also be generated with perf script:

 # Packed byte string args of process_event():
 #
 # $event:       union perf_event        util/event.h
 # $attr:        struct perf_event_attr  linux/perf_event.h
 # $sample:      struct perf_sample      util/event.h
 # $raw_data:    perf_sample->raw_data   util/event.h

 sub process_event
 {
         my ($event, $attr, $sample, $raw_data) = @_;

         my @event       = unpack("LSS", $event);
         my @attr        = unpack("LLQQQQQLLQQ", $attr);
         my @sample      = unpack("QLLQQQQQLL", $sample);
         my @raw_data    = unpack("C*", $raw_data);

         use Data::Dumper;
         print Dumper \@event, \@attr, \@sample, \@raw_data;
 }

Signed-off-by: Robert Richter <robert.richter@amd.com>