perf symbols: debuglink should take symfs option into account

Currently code that tries to read corresponding debug symbol file from
.gnu_debuglink section (DSO_BINARY_TYPE__DEBUGLINK) does not take in
account symfs option, so filename__read_debuglink function cannot open
ELF file, if symfs option is used.

Fix is to add proper handling of symfs as it is done in other places:
use __symbol__join_symfs function to get real file name of target ELF
file.

Signed-off-by: Victor Kamensky <[e-mail]>
Tested-by: David Ahern <[e-mail]>
Acked-by: David Ahern <[e-mail]>
Acked-by: Namhyung Kim <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Anton Blanchard <[e-mail]>
Cc: Avi Kivity <[e-mail]>
Cc: Dave Martin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Russell King <[e-mail]>
Cc: Waiman Long <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/dso.c

···
 	case DSO_BINARY_TYPE__DEBUGLINK: {
 		char *debuglink;
 
-		strncpy(filename, dso->long_name, size);
-		debuglink = filename + dso->long_name_len;
+		len = __symbol__join_symfs(filename, size, dso->long_name);
+		debuglink = filename + len;
 		while (debuglink != filename && *debuglink != '/')
 			debuglink--;
 		if (*debuglink == '/')
 			debuglink++;
-		ret = filename__read_debuglink(dso->long_name, debuglink,
+		ret = filename__read_debuglink(filename, debuglink,
 					       size - (debuglink - filename));
 		}
 		break;