perf tools: Fix annotation with kcore

Patch "perf tools: Fix build-id matching on vmlinux" breaks annotation
with kcore.  The problem is that symbol__annotate() first gets the
filename based on the build-id which was previously not set.

This patch provides a quick fix, however there should probably be only
one way to determine the filename. e.g.  symbol__annotate() should use
the same way as dso__data_fd().

Signed-off-by: Adrian Hunter <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/annotate.c

@@ -915,6 +915,8 @@ int symbol__annotate(struct symbol *sym, struct map *map, size_t privsize)
 			return -ENOMEM;
 		}
 		goto fallback;
+	} else if (dso__is_kcore(dso)) {
+		goto fallback;
 	} else if (readlink(symfs_filename, command, sizeof(command)) < 0 ||
 		   strstr(command, "[kernel.kallsyms]") ||
 		   access(symfs_filename, R_OK)) {