linux-kernel - Re: [PATCH v6 10/12] perf tools: Improve IBS error handling

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Message-ID: <5609a43a-afbe-7629-b84d-75ace62da4fe@amd.com>
Date:   Tue, 15 Mar 2022 11:53:22 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     peterz@...radead.org, kim.phillips@....com, acme@...hat.com,
        jolsa@...hat.com, songliubraving@...com,
        Ravi Bangoria <ravi.bangoria@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 10/12] perf tools: Improve IBS error handling

>> +static bool is_amd(const char *arch, const char *cpuid)
>> +{
>> +       return arch && !strcmp("x86", arch) && cpuid && strstarts(cpuid, "AuthenticAMD");
>> +}
>> +
>> +static bool is_amd_ibs(struct evsel *evsel)
>> +{
>> +       return evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, "ibs", 3);
>> +}
>> +
>>  int evsel__open_strerror(struct evsel *evsel, struct target *target,
>>                          int err, char *msg, size_t size)
>>  {
>> +       struct perf_env *env = evsel__env(evsel);
>> +       const char *arch = perf_env__arch(env);
>> +       const char *cpuid = perf_env__cpuid(env);
> 
> 
> This code dies for me on the latest tip.git because env = NULL and
> perf_env_cpuid() is broken for NULL argument.
> I don't quite know where this env global variable is set but I hope
> there is a better way of doing this, maybe using
> the evsel__env() function in the same util/evsel.c file.
> 
> Similarly, the is_amd_ibs() suffers from a NULL pointer dereference
> because evsel->pmu_name maybe NULL:
> 
> $ perf record -e rc2 .....
> 
> causes a NULL pmu_name.

This should fix the issue:

@@ -2965,7 +2989,7 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,

 struct perf_env *evsel__env(struct evsel *evsel)
 {
-	if (evsel && evsel->evlist)
+	if (evsel && evsel->evlist && evsel->evlist->env)
 		return evsel->evlist->env;
 	return &perf_env;
 }

Thanks,
Ravi