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 17:36:46 +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 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.

>   	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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