linux-kernel - Re: [PATCH] perf cs-etm: Fix contextid validation

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Date:   Wed, 10 May 2023 14:41:11 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     James Clark <james.clark@....com>
Cc:     linux-perf-users@...r.kernel.org, Leo Yan <leo.yan@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf cs-etm: Fix contextid validation

Em Thu, May 04, 2023 at 03:48:22PM +0100, James Clark escreveu:
> Pre 5.11 kernels don't support 'contextid1' and 'contextid2' so
> validation would be skipped. By adding an additional check for
> 'contextid', old kernels will still have validation done even though
> contextid would either be contextid1 or contextid2.
> 
> Additionally now that it's possible to override options, an existing bug
> in the validation is revealed. 'val' is overwritten by the contextid1
> validation, and re-used for contextid2 validation causing it to always
> fail. '!val || val != 0x4' is the same as 'val != 0x4' because 0 is also
> != 4, so that expression can be simplified and the temp variable not
> overwritten.
> 
> Fixes: 35c51f83dd1e ("perf cs-etm: Validate options after applying them")

Thanks, applied to perf-tools, for v6.4.

- Arnaldo

> Reviewed-by: Leo Yan <leo.yan@...aro.org>
> Link: https://lore.kernel.org/all/20230501073452.GA4660@leoy-yangtze.lan
> Signed-off-by: James Clark <james.clark@....com>
> ---
>  tools/perf/arch/arm/util/cs-etm.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
> index 77cb03e6ff87..9ca040bfb1aa 100644
> --- a/tools/perf/arch/arm/util/cs-etm.c
> +++ b/tools/perf/arch/arm/util/cs-etm.c
> @@ -78,9 +78,9 @@ static int cs_etm_validate_context_id(struct auxtrace_record *itr,
>  	char path[PATH_MAX];
>  	int err;
>  	u32 val;
> -	u64 contextid =
> -		evsel->core.attr.config &
> -		(perf_pmu__format_bits(&cs_etm_pmu->format, "contextid1") |
> +	u64 contextid = evsel->core.attr.config &
> +		(perf_pmu__format_bits(&cs_etm_pmu->format, "contextid") |
> +		 perf_pmu__format_bits(&cs_etm_pmu->format, "contextid1") |
>  		 perf_pmu__format_bits(&cs_etm_pmu->format, "contextid2"));
>  
>  	if (!contextid)
> @@ -114,8 +114,7 @@ static int cs_etm_validate_context_id(struct auxtrace_record *itr,
>  		 *  0b00100 Maximum of 32-bit Context ID size.
>  		 *  All other values are reserved.
>  		 */
> -		val = BMVAL(val, 5, 9);
> -		if (!val || val != 0x4) {
> +		if (BMVAL(val, 5, 9) != 0x4) {
>  			pr_err("%s: CONTEXTIDR_EL1 isn't supported, disable with %s/contextid1=0/\n",
>  			       CORESIGHT_ETM_PMU_NAME, CORESIGHT_ETM_PMU_NAME);
>  			return -EINVAL;
> -- 
> 2.34.1
> 

-- 

- Arnaldo