perf: Add pipe-specific header read/write and event processing code

This patch makes several changes to allow the perf event stream
to be sent and received over a pipe:

- adds pipe-specific versions of the header read/write code

- adds pipe-specific version of the event processing code

- adds a range of event types to be used for header or other
  pseudo events, above the range used by the kernel

- checks the return value of event handlers, which they can use
  to skip over large events during event processing rather than actually
  reading them into event objects.

- unifies the multiple do_read() functions and updates its
  users.

Note that none of these changes affect the existing perf data
file format or processing - this code only comes into play if
perf output is sent to stdout (or is read from stdin).

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
Cc: k-keiichi@bx.jp.nec.com
Cc: acme@ghostprotocols.net
LKML-Reference: <1270184365-8281-2-git-send-email-tzanussi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/session.h

@@ -27,6 +27,7 @@ struct perf_session {
 	u64			sample_type;
 	struct ref_reloc_sym	ref_reloc_sym;
 	int			fd;
+	bool			fd_pipe;
 	int			cwdlen;
 	char			*cwd;
 	char filename[0];
@@ -92,6 +93,9 @@ static inline struct map *
 	return map_groups__new_module(&self->kmaps, start, filename);
 }
 
+int do_read(int fd, void *buf, size_t size);
+void perf_session__update_sample_type(struct perf_session *self);
+
 #ifdef NO_NEWT_SUPPORT
 static inline int perf_session__browse_hists(struct rb_root *hists __used,
 					      u64 nr_hists __used,