'perf record' post-processes the event stream  to create a list of
build-ids for object files for which sample events have been recorded.
That results in those object files being recorded in the build-id cache.

In the case of VDSO, perf tools reads it from memory and copies it into
a temporary file, which as decribed above, gets added to the build-id
cache.

Then when the perf.data file is processed by other tools, the build-id
of VDSO is listed in the perf.data file and the VDSO can be read from
the build-id cache.  In that case the name of the map, the short name of
the DSO, and the entry in the build-id cache are all "[vdso]".

However, in the 64-bit case, there also can be 32-bit compatibility
VDSOs.

A previous patch added programs "perf-read-vdso32" and "perf
read-vdsox32".

This patch uses those programs to read the correct VDSO for a thread and
create a temporary file just as for the 64-bit VDSO.

The map name and the entry in the build-id cache are still "[vdso]" but
the DSO short name becomes "[vdso32]" and "[vdsox32]" respectively.
Signed-off-by: NAdrian 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/1414061124-26830-16-git-send-email-adrian.hunter@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>