Date:	Fri, 24 Jun 2016 09:54:22 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH] perf: symbols: dso__load(): remove check of file on
 uninitialized memory

On 06/24/2016 08:43 AM, Jiri Olsa wrote:
> On Thu, Jun 23, 2016 at 04:20:21PM +0200, Marc Kleine-Budde wrote:
>> In commit "403567217d3f 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)
>>
>> This patch fixes the problem by removing the check.
>>
>> Fixes: 403567217d3f perf symbols: Do not read symbols/data from device files
>> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
>> ---
>>  tools/perf/util/symbol.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
>> index 8a747dc6cf86..b4070daeb17f 100644
>> --- a/tools/perf/util/symbol.c
>> +++ b/tools/perf/util/symbol.c
>> @@ -1432,8 +1432,7 @@ 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) &&
>> -	    filename__read_build_id(dso->long_name, build_id, BUILD_ID_SIZE) > 0)
>> +	if (filename__read_build_id(dso->long_name, build_id, BUILD_ID_SIZE) > 0)
>>  		dso__set_build_id(dso, build_id);
> 
> ouch copy&paste error.. we better fix it properly,
> could you please check attached patch?

The use of uninitialized memory is gone, but the "--symfs" option is
ignored:

> stat("/lib/libpthread-2.20.so", 0x7ffe440c1270) = -1 ENOENT (No such file or directory)

You'll look for the dso in the root file system not in the sysroot.

> stat("./root//lib/libpthread-2.20.so", {st_mode=S_IFREG|0755, st_size=68048, ...}) = 0
> open("./root//lib/libpthread-2.20.so", O_RDONLY) = 4
> stat("./root//lib/libpthread-2.20.so", {st_mode=S_IFREG|0755, st_size=68048, ...}) = 0
> open("./root//lib/libpthread-2.20.so", O_RDONLY) = 4
> stat("./root//usr/lib/debug/lib/libpthread-2.20.so.debug", 0x7ffe440c1270) = -1 ENOENT (No such file or directory)
> stat("./root//usr/lib/debug/lib/libpthread-2.20.so", 0x7ffe440c1270) = -1 ENOENT (No such file or directory)
> stat("./root//lib/libpthread-2.20.so", {st_mode=S_IFREG|0755, st_size=68048, ...}) = 0
> open("./root//lib/libpthread-2.20.so", O_RDONLY) = 5
> stat("./root//lib/.debug/libpthread-2.20.so", {st_mode=S_IFREG|0644, st_size=266508, ...}) = 0
> open("./root//lib/.debug/libpthread-2.20.so", O_RDONLY) = 5

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
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