Re: [BUG] perf: intel_pt won't display kernel function

[Song Liu]

> On Apr 3, 2019, at 11:59 AM, Song Liu <songliubraving@xxxxxx> wrote:
> 
> 
> 
>> On Apr 3, 2019, at 11:55 AM, Song Liu <songliubraving@xxxxxx> wrote:
>> 
>> 
>> 
>>> On Apr 3, 2019, at 11:50 AM, Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> wrote:
>>> 
>>> Em Wed, Apr 03, 2019 at 04:27:56PM +0000, Song Liu escreveu:
>>>> 
>>>> 
>>>>> On Apr 3, 2019, at 8:15 AM, Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> wrote:
>>>>> 
>>>>> Em Wed, Apr 03, 2019 at 11:53:53AM -0300, Arnaldo Carvalho de Melo escreveu:
>>>>>> Em Wed, Apr 03, 2019 at 04:37:38PM +0200, Jiri Olsa escreveu:
>>>>>>> hi,
>>>>>>> perf script --call-trace stop working for me recently,
>>>>>>> and displays only user space functions
>>>>>>> 
>>>>>>> I bisected that to:
>>>>>>> 7b612e291a5a perf tools: Synthesize PERF_RECORD_* for loaded BPF programs
>>>>>>> 
>>>>>>> data from following comands will display user space functions only:
>>>>>>> # perf-with-kcore record pt -e intel_pt// -- ls
>>>>>>> # perf-with-kcore script pt --call-trace
>>>>>>> 
>>>>>>> when I disable the bpf synthesizing (patch below), kernel functions are back
>>>>>>> 
>>>>>>> I guess the new events mess up with intel_pt decoder somehow
>>>>>> 
>>>>>> I.e. I'm adding the patch below to my perf/urgent branch.
>>>>> 
>>>>> Song, that is what I have, can I have your Acked-by and please consider
>>>>> taking a look at the bug Jiri reported,
>>>>> 
>>>>> Thanks,
>>>>> 
>>>>> - Arnaldo
>>>> 
>>>> Current logic with --no-bpf-event is to generate PERF_RECORD_KSYMBOL, but not
>>>> PERF_RECORD_BPF_EVENT:
>>> 
>>> I see... The opts is done later, after querying the kernel for existing
>>> BPF programs so that at least the KSYMBOL ones can be generated. So I'll
>>> keep it as is, no need for this patch.
>>> 
>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__elixir.bootlin.com_linux_v5.1-2Drc3_source_tools_perf_util_bpf-2Devent.c-23L254&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=8ITYgIrqFBIy1uQFQPHrsX5kBX5RlmhwcknKYJa2eGs&s=MdB2zA9JstwC93qKEonsfTQeQYiw-yeOLbPxm3QMRo8&e=
>>>> 
>>>> I will look into the intel_pt problem. 
>>> 
>>> Ok.
>>> 
>>>> In the meanwhile, let's fix it for now. 
>>> 
>>> I'll wait a bit.
>> 
>> I guess something like this might be a better fix? (Sorry for missing 
>> commit message):
>> 
>> diff --git i/tools/perf/util/map.c w/tools/perf/util/map.c
>> index e32628cd20a7..741430a35dca 100644
>> --- i/tools/perf/util/map.c
>> +++ w/tools/perf/util/map.c
>> @@ -261,6 +261,12 @@ bool __map__is_extra_kernel_map(const struct map *map)
>>       return kmap && kmap->name[0];
>> }
>> 
>> +bool __map__is_bpf_prog(const struct map *map)
>> +{
>> +       const char *name = map->dso->short_name;
>> +       return name && (strstr(name, "bpf_prog_") == name);
>> +}
>> +
>> bool map__has_symbols(const struct map *map)
>> {
>>       return dso__has_symbols(map->dso);
>> diff --git i/tools/perf/util/map.h w/tools/perf/util/map.h
>> index 0e20749f2c55..01079f1f4375 100644
>> --- i/tools/perf/util/map.h
>> +++ w/tools/perf/util/map.h
>> @@ -159,10 +159,12 @@ int map__set_kallsyms_ref_reloc_sym(struct map *map, const char *symbol_name,
>> 
>> bool __map__is_kernel(const struct map *map);
>> bool __map__is_extra_kernel_map(const struct map *map);
>> +bool __map__is_bpf_prog(const struct map *map);
>> 
>> static inline bool __map__is_kmodule(const struct map *map)
>> {
>> -       return !__map__is_kernel(map) && !__map__is_extra_kernel_map(map);
>> +       return !__map__is_kernel(map) && !__map__is_extra_kernel_map(map) &&
>> +               !__map__is_bpf_prog(map);
>> }
>> 
>> bool map__has_symbols(const struct map *map);
>> 
>> Thanks,
>> Song
> 
> Actually, it should be something like this:
> 
> diff --git i/tools/perf/util/map.c w/tools/perf/util/map.c
> index e32628cd20a7..31cd23612529 100644
> --- i/tools/perf/util/map.c
> +++ w/tools/perf/util/map.c
> @@ -261,6 +261,11 @@ bool __map__is_extra_kernel_map(const struct map *map)
>        return kmap && kmap->name[0];
> }
> 
> +bool __map__is_bpf_prog(const struct map *map)
> +{
> +       return map->dso->binary_type == DSO_BINARY_TYPE__BPF_PROG_INFO;
> +}
> +
> bool map__has_symbols(const struct map *map)
> {
>        return dso__has_symbols(map->dso);
> diff --git i/tools/perf/util/map.h w/tools/perf/util/map.h
> index 0e20749f2c55..01079f1f4375 100644
> --- i/tools/perf/util/map.h
> +++ w/tools/perf/util/map.h
> @@ -159,10 +159,12 @@ int map__set_kallsyms_ref_reloc_sym(struct map *map, const char *symbol_name,
> 
> bool __map__is_kernel(const struct map *map);
> bool __map__is_extra_kernel_map(const struct map *map);
> +bool __map__is_bpf_prog(const struct map *map);
> 
> static inline bool __map__is_kmodule(const struct map *map)
> {
> -       return !__map__is_kernel(map) && !__map__is_extra_kernel_map(map);
> +       return !__map__is_kernel(map) && !__map__is_extra_kernel_map(map) &&
> +               !__map__is_bpf_prog(map);
> }
> 
> bool map__has_symbols(const struct map *map);
> 
> 
>> 
>>> 
>>>> Acked-by: Song Liu <songliubraving@xxxxxx>
>>>> 
>>>> Thanks, 
>>>> Song
>>>> 
>>>> 
>>>>> commit 011318ccc2024ba03e96c32a06f74ca5d6ab5503
>>>>> Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>>>>> Date:   Wed Apr 3 12:05:15 2019 -0300
>>>>> 
>>>>> perf record: Do not synthesize BPF records when --no-bpf-event is used
>>>>> 
>>>>> By default we synthesize and ask the kernel for BPF events, having a
>>>>> --no-bpf-event option to disable that, which can be useful, for
>>>>> instance, if there are still bugs in that code, which seems to be the
>>>>> case as reported by Jiri Olsa in:
>>>>> 
>>>>>   "[BUG] perf: intel_pt won't display kernel function"
>>>>>   20190403143738.GB32001@krava">https://lore.kernel.org/lkml/20190403143738.GB32001@krava
>>>>> 
>>>>> So add the check for record_opts.no_bpf_event when considering
>>>>> synthesizing BPF events for pre-existing BPF programs in 'perf record'.
>>>>> 
>>>>> The reported bug needs further analysis and is a separate matter.
>>>>> 
>>>>> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>>>>> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
>>>>> Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
>>>>> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
>>>>> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
>>>>> Cc: Martin KaFai Lau <kafai@xxxxxx>
>>>>> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
>>>>> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>>>>> Cc: Song Liu <songliubraving@xxxxxx>
>>>>> Cc: Yonghong Song <yhs@xxxxxx>
>>>>> Fixes: 7b612e291a5a ("perf tools: Synthesize PERF_RECORD_* for loaded BPF programs")
>>>>> Link: https://lore.kernel.org/lkml/20190403145353.GE32553@xxxxxxxxxx
>>>>> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>>>>> 
>>>>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>>>>> index 4e2d953d4bc5..17d772f192ad 100644
>>>>> --- a/tools/perf/builtin-record.c
>>>>> +++ b/tools/perf/builtin-record.c
>>>>> @@ -1114,10 +1114,11 @@ static int record__synthesize(struct record *rec, bool tail)
>>>>> 		return err;
>>>>> 	}
>>>>> 
>>>>> -	err = perf_event__synthesize_bpf_events(session, process_synthesized_event,
>>>>> -						machine, opts);
>>>>> -	if (err < 0)
>>>>> -		pr_warning("Couldn't synthesize bpf events.\n");
>>>>> +	if (!opts->no_bpf_event) {
>>>>> +		err = perf_event__synthesize_bpf_events(session, process_synthesized_event, machine, opts);
>>>>> +		if (err < 0)
>>>>> +			pr_warning("Couldn't synthesize bpf events.\n");
>>>>> +	}
>>>>> 
>>>>> 	err = __machine__synthesize_threads(machine, tool, &opts->target, rec->evlist->threads,
>>>>> 					    process_synthesized_event, opts->sample_address,
>>> 
>>> -- 
>>> 
>>> - Arnaldo

Yet another version, with commit message and a little more logic: