linux-kernel - Re: [PATCH 02/16] perf pmu: Let pmu's with no events show up on perf list

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Date:	Fri, 24 Oct 2014 17:38:49 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 02/16] perf pmu: Let pmu's with no events show up on perf
 list

On 24/10/2014 5:36 p.m., Adrian Hunter wrote:
> On 24/10/2014 4:21 p.m., Arnaldo Carvalho de Melo wrote:
>> Em Fri, Oct 24, 2014 at 10:03:20AM -0300, Arnaldo Carvalho de Melo escreveu:
>>> Em Fri, Oct 24, 2014 at 09:57:02AM -0300, Arnaldo Carvalho de Melo escreveu:
>>>> Em Fri, Oct 24, 2014 at 02:15:52PM +0900, Namhyung Kim escreveu:
>>>>> On Thu, 23 Oct 2014 13:45:10 +0300, Adrian Hunter wrote:
>>>>>> +        if (pmu->selectable) {
>>>>>> +            scnprintf(buf, sizeof(buf), "%s//", pmu->name);
>>>>>> +            aliases[j] = strdup(buf);
>>>>>
>>>>> You need to check the return value here (and above too).
>>>>
>>>> Well spotted, fixing this up.
>>>
>>> Oh well, this print_pmu_events() function needs some care, it starts by
>>> trying to alloc the array, if it fails, it silently returns, does that
>>> mean that there are no pmu events? Or that memory allocation failed?
>>>
>>> Ok, will do the fixes in a separate patch...
>>>
>>> - Arnaldo
>>
>> The patch below should check everything and warn the user, even
>> maintaining that void return...
>>
>> Acked-by tags welcome as always :-)
>>
>> - Arnaldo
>>
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 91dca60..881b754 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -753,9 +753,9 @@ void print_pmu_events(const char *event_glob, bool name_only)
>>           if (pmu->selectable)
>>               len++;
>>       }
>> -    aliases = malloc(sizeof(char *) * len);
>> +    aliases = zalloc(sizeof(char *) * len);
>>       if (!aliases)
>> -        return;
>> +        goto out_enomem;
>
> That path tries to free aliases[j] but aliases is null.  You could set len to 0 in that case.

Than again, no it doesn't sorry for the noise.

>
>>       pmu = NULL;
>>       j = 0;
>>       while ((pmu = perf_pmu__scan(pmu)) != NULL) {
>> @@ -768,16 +768,20 @@ void print_pmu_events(const char *event_glob, bool name_only)
>>                     (!is_cpu && strglobmatch(alias->name,
>>                                  event_glob))))
>>                   continue;
>> -            aliases[j] = name;
>> +
>>               if (is_cpu && !name_only)
>> -                aliases[j] = format_alias_or(buf, sizeof(buf),
>> -                                  pmu, alias);
>> -            aliases[j] = strdup(aliases[j]);
>> +                name = format_alias_or(buf, sizeof(buf), pmu, alias);
>> +
>> +            aliases[j] = strdup(name);
>> +            if (aliases[j] == NULL)
>> +                goto out_enomem;
>>               j++;
>>           }
>>           if (pmu->selectable) {
>> -            scnprintf(buf, sizeof(buf), "%s//", pmu->name);
>> -            aliases[j] = strdup(buf);
>> +            char *s;
>> +            if (asprintf(&s, "%s//", pmu->name) < 0)
>> +                goto out_enomem;
>> +            aliases[j] = s;
>>               j++;
>>           }
>>       }
>> @@ -789,12 +793,20 @@ void print_pmu_events(const char *event_glob, bool name_only)
>>               continue;
>>           }
>>           printf("  %-50s [Kernel PMU event]\n", aliases[j]);
>> -        zfree(&aliases[j]);
>>           printed++;
>>       }
>>       if (printed)
>>           printf("\n");
>> -    free(aliases);
>> +out_free:
>> +    for (j = 0; j < len; j++)
>> +        zfree(&aliases[j]);
>> +    zfree(&aliases);
>> +    return;
>> +
>> +out_enomem:
>> +    printf("FATAL: not enough memory to print PMU events\n");
>> +    if (aliases)
>> +        goto out_free;
>>   }
>>
>>   bool pmu_have_event(const char *pname, const char *name)
>>
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