perf symbols: Use proper dso name for is_regular_file

Marc reported use of uninitialized memory:

> In commit "40356721 perf symbols: Do not read symbols/data from
> device files" a check to uninitialzied memory was added. This leads to
> the following valgrind output:
>
>  ==24515== Syscall param stat(file_name) points to uninitialised byte(s)
>  ==24515==    at 0x75B26D5: _xstat (in /lib/x86_64-linux-gnu/libc-2.22.so)
>  ==24515==    by 0x4E548D: stat (stat.h:454)
>  ==24515==    by 0x4E548D: is_regular_file (util.c:687)
>  ==24515==    by 0x4A5BEE: dso__load (symbol.c:1435)
>  ==24515==    by 0x4BB1AE: map__load (map.c:289)
>  ==24515==    by 0x4BB1AE: map__find_symbol (map.c:333)
>  ==24515==    by 0x4835B3: thread__find_addr_location (event.c:1300)
>  ==24515==    by 0x4B5342: add_callchain_ip (machine.c:1652)
>  ==24515==    by 0x4B5342: thread__resolve_callchain_sample (machine.c:1906)
>  ==24515==    by 0x4B9E7D: thread__resolve_callchain (machine.c:1958)
>  ==24515==    by 0x441B3E: process_event (builtin-script.c:795)
>  ==24515==    by 0x441B3E: process_sample_event (builtin-script.c:920)
>  ==24515==    by 0x4BEE29: perf_evlist__deliver_sample (session.c:1192)
>  ==24515==    by 0x4BEE29: machines__deliver_event (session.c:1229)
>  ==24515==    by 0x4BF770: perf_session__deliver_event (session.c:1286)
>  ==24515==    by 0x4BF770: ordered_events__deliver_event (session.c:114)
>  ==24515==    by 0x4C1D17: __ordered_events__flush (ordered-events.c:207)
>  ==24515==    by 0x4C1D17: ordered_events__flush.part.3 (ordered-events.c:274)
>  ==24515==    by 0x4BF44C: perf_session__process_user_event (session.c:1325)
>  ==24515==    by 0x4BF44C: perf_session__process_event (session.c:1451)
>  ==24515==  Address 0x807c6a0 is 0 bytes inside a block of size 4,096 alloc'd
>  ==24515==    at 0x4C29C0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
>  ==24515==    by 0x4A5BCB: dso__load (symbol.c:1421)
>  ==24515==    by 0x4BB1AE: map__load (map.c:289)
>  ==24515==    by 0x4BB1AE: map__find_symbol (map.c:333)
>  ==24515==    by 0x4835B3: thread__find_addr_location (event.c:1300)
>  ==24515==    by 0x4B5342: add_callchain_ip (machine.c:1652)
>  ==24515==    by 0x4B5342: thread__resolve_callchain_sample (machine.c:1906)
>  ==24515==    by 0x4B9E7D: thread__resolve_callchain (machine.c:1958)
>  ==24515==    by 0x441B3E: process_event (builtin-script.c:795)
>  ==24515==    by 0x441B3E: process_sample_event (builtin-script.c:920)
>  ==24515==    by 0x4BEE29: perf_evlist__deliver_sample (session.c:1192)
>  ==24515==    by 0x4BEE29: machines__deliver_event (session.c:1229)
>  ==24515==    by 0x4BF770: perf_session__deliver_event (session.c:1286)
>  ==24515==    by 0x4BF770: ordered_events__deliver_event (session.c:114)
>  ==24515==    by 0x4C1D17: __ordered_events__flush (ordered-events.c:207)
>  ==24515==    by 0x4C1D17: ordered_events__flush.part.3 (ordered-events.c:274)
>  ==24515==    by 0x4BF44C: perf_session__process_user_event (session.c:1325)
>  ==24515==    by 0x4BF44C: perf_session__process_event (session.c:1451)
>  ==24515==    by 0x4C0EAC: __perf_session__process_events (session.c:1804)
>  ==24515==    by 0x4C0EAC: perf_session__process_events (session.c:1858)

The reason was a typo that passed global 'name' variable as the
is_regular_file argument instead dso->long_name.
Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 40356721 ("perf symbols: Do not read symbols/data from device files")
Link: http://lkml.kernel.org/r/1466772025-17471-2-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol.c

@@ -1430,7 +1430,7 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
 	 * Read the build id if possible. This is required for
 	 * DSO_BINARY_TYPE__BUILDID_DEBUGINFO to work
 	 */
-	if (is_regular_file(name) &&
+	if (is_regular_file(dso->long_name) &&
 	    filename__read_build_id(dso->long_name, build_id, BUILD_ID_SIZE) > 0)
 		dso__set_build_id(dso, build_id);