perf bpf: Fix synthesized PERF_RECORD_KSYMBOL/BPF_EVENT

Added missing machine->id_hdr_size to event->header.size. Also fixed
size of PERF_RECORD_KSYMBOL by removing extra bytes for name.

Committer notes:

We need to malloc that extra machine->id_hdr_size at the start of
perf_event__synthesize_bpf_events() and also need to cast the event to
(void *) otherwise we segfault, fix it.

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Suggested-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team@fb.com
Fixes: 7b612e29 ("perf tools: Synthesize PERF_RECORD_* for loaded BPF programs")
Link: http://lkml.kernel.org/r/20190122210218.358664-1-songliubraving@fb.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>