perf tools: Add guest_code support

A common case for KVM test programs is that the test program acts as the
hypervisor, creating, running and destroying the virtual machine, and
providing the guest object code from its own object code. In this case,
the VM is not running an OS, but only the functions loaded into it by the
hypervisor test program, and conveniently, loaded at the same virtual
addresses.

Normally to resolve addresses, MMAP events are needed to map addresses
back to the object code and debug symbols for that object code.

Currently, there is no way to get such mapping information from guests
but, in the scenario described above, the guest has the same mappings
as the hypervisor, so support for that scenario can be achieved.

To support that, copy the host thread's maps to the guest thread's maps.
Note, we do not discover the guest until we encounter a guest event,
which works well because it is not until then that we know that the host
thread's maps have been set up.

Typically the main function for the guest object code is called
"guest_code", hence the name chosen for this feature. Note, that is just a
convention, the function could be named anything, and the tools do not
care.

This is primarily aimed at supporting Intel PT, or similar, where trace
data can be recorded for a guest. Refer to the final patch in this series
"perf intel-pt: Add guest_code support" for an example.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220517131011.6117-4-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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