perf symbols: Check return value of filename__read_debuglink()

When dso__read_binary_type_filename() called, it doesn't check the
return value of filename__read_debuglink() so that it'll try to open the
debuglink file even if it doesn't exist.

Also fix return value of the filename__read_debuglink() as it always
return -1 regardless of the result.

Signed-off-by: Namhyung Kim <[e-mail]>
Cc: Cody P Schafer <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/dso.c

···
 			debuglink--;
 		if (*debuglink == '/')
 			debuglink++;
-		filename__read_debuglink(dso->long_name, debuglink,
-					 size - (debuglink - filename));
+		ret = filename__read_debuglink(dso->long_name, debuglink,
+					       size - (debuglink - filename));
 		}
 		break;
 	case DSO_BINARY_TYPE__BUILD_ID_CACHE:

tools/perf/util/symbol-elf.c

···
 	/* the start of this section is a zero-terminated string */
 	strncpy(debuglink, data->d_buf, size);
 
+	err = 0;
+
 out_elf_end:
 	elf_end(elf);
 out_close: