perf report: Provide libtraceevent with a kernel symbol resolver

So that beautifiers wanting to resolve kernel function addresses to
names can do its work, and when we use "perf report" for output of "perf
kmem record", we will get kernel symbol output.

This patch affect the output of "perf report" for the record data
generated by "perf kmem record" looks like below:

Before patch:
0.01%  call_site=ffffffff814e5828 ptr=0x99bb000 bytes_req=3616 bytes_alloc=4096 gfp_flags=GFP_ATOMIC
0.01%  call_site=ffffffff81370b87 ptr=0x428a3060 bytes_req=32 bytes_alloc=32 gfp_flags=GFP_KERNEL|GFP_ZERO

After patch:
0.01%  (aa_alloc_task_context+0x27) call_site=ffffffff81370b87 ptr=0x428a3060 bytes_req=32 bytes_alloc=32 gfp_flags=GFP_KERNEL|GFP_ZERO
0.01%  (__tty_buffer_request_room+0x88) call_site=ffffffff814e5828 ptr=0x99bb000 bytes_req=3616 bytes_alloc=4096 gfp_flags=GFP_ATOMIC

Signed-off-by: Wang YanQing <udknight@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180308032850.GA12383@udknight-ThinkPad-E550
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-report.c

@@ -1348,6 +1348,15 @@ repeat:
 		report.range_num = 1;
 	}
 
+	if (session->tevent.pevent &&
+	    pevent_set_function_resolver(session->tevent.pevent,
+					 machine__resolve_kernel_addr,
+					 &session->machines.host) < 0) {
+		pr_err("%s: failed to set libtraceevent function resolver\n",
+		       __func__);
+		return -1;
+	}
+
 	sort__setup_elide(stdout);
 
 	ret = __cmd_report(&report);