Ian came with the idea of having support to read the pipe data also from
file. Currently pipe mode files fail like:

  $ perf record -o - sleep 1 > /tmp/perf.pipe.data
  $ perf report -i /tmp/perf.pipe.data
  incompatible file format (rerun with -v to learn more)

This patch adds the support to do that by trying the pipe header first,
and if its successfully detected, switching the perf data to pipe mode.

Committer testing:

  # ls
  # perf record -a -o - sleep 1 > /tmp/perf.pipe.data
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.000 MB - ]
  # ls
  # perf report -i /tmp/perf.pipe.data | head -25
  # To display the perf.data header info, please use --header/--header-only options.
  #
  #
  # Total Lost Samples: 0
  #
  # Samples: 511  of event 'cycles'
  # Event count (approx.): 178447276
  #
  # Overhead  Command   Shared Object      Symbol
  # ........  ........  .................  ...........................................................................................
  #
      65.49%  swapper   [kernel.kallsyms]  [k] native_safe_halt
       6.45%  chromium  libblink_core.so   [.] blink::SelectorChecker::CheckOne
       4.08%  chromium  libblink_core.so   [.] blink::SelectorQuery::ExecuteForTraverseRoot<blink::AllElementsSelectorQueryTrait>
       2.25%  chromium  libblink_core.so   [.] blink::SelectorQuery::FindTraverseRootsAndExecute<blink::AllElementsSelectorQueryTrait>
       2.11%  chromium  libblink_core.so   [.] blink::SelectorChecker::MatchSelector
       1.91%  chromium  libblink_core.so   [.] blink::Node::OwnerShadowHost
       1.31%  chromium  libblink_core.so   [.] blink::Node::parentNode@plt
       1.22%  chromium  libblink_core.so   [.] blink::Node::parentNode
       0.59%  chromium  libblink_core.so   [.] blink::AnyAttributeMatches
       0.58%  chromium  libv8.so           [.] v8::internal::GlobalHandles::Create
       0.58%  chromium  libblink_core.so   [.] blink::NodeTraversal::NextAncestorSibling
       0.55%  chromium  libv8.so           [.] v8::internal::RegExpGlobalCache::RegExpGlobalCache
       0.55%  chromium  libblink_core.so   [.] blink::Node::ContainingShadowRoot
       0.55%  chromium  libblink_core.so   [.] blink::NodeTraversal::NextAncestorSibling@plt
  #

Original-patch-by: Ian Rogers <irogers@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Khuong <pvk@pvk.ca>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200507095024.2789147-4-jolsa@kernel.org


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