perf report: Use properly build_id kernel binaries

If we bring the recorded perf data together with kernel binary from another
machine using:

	on server A:
	perf archive

	on server B:
	tar xjvf perf.data.tar.bz2 -C ~/.debug

the build_id kernel dso is not properly recognized during the "perf report"
command on server B.

The reason is, that build_id dsos are added during the session initialization,
while the kernel maps are created during the sample event processing.

The machine__create_kernel_maps functions ends up creating new dso object for
kernel, but it does not check if we already have one added by build_id
processing.

Also the build_id reading ABI quirk added in commit:

 - commit b25114817a73bbd2b84ce9dba02ee1ef8989a947
   perf build-id: Add quirk to deal with perf.data file format breakage

populates the "struct build_id_event::pid" with 0, which
is later interpreted as DEFAULT_GUEST_KERNEL_ID.

This is not always correct, so it's better to guess the pid
value based on the "struct build_id_event::header::misc" value.

- Tested with data generated on x86 kernel version v2.6.34
  and reported back on x86_64 current kernel.
- Not tested for guest kernel case.

Note the problem stays for PERF_RECORD_MMAP events recorded by perf that
does not use proper pid (HOST_KERNEL_ID/DEFAULT_GUEST_KERNEL_ID). They are
misinterpreted within the current perf code. Probably there's not much we
can do about that.

Cc: Avi Kivity <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Yanmin Zhang <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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