The VDSO temporary file is unlinked when a session is deleted.  That
precludes the possibilities that there is no session or there is more
than one session.

Correctly the vdso belongs to the machine so put the information on
'struct machine' and get rid of the global variables.
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/53CF9B14.7040408@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>