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

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Message-ID: <20141024132141.GB14687@kernel.org>
Date:	Fri, 24 Oct 2014 10:21:41 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Adrian Hunter <adrian.hunter@...el.com>,
	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

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;
 	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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