linux-kernel - Re: [PATCH] perf tests: evsel-tp-sched: Fix bitwise operator

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Date:   Wed, 23 Jan 2019 09:33:38 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf tests: evsel-tp-sched: Fix bitwise operator

On Tue, Jan 22, 2019 at 05:34:39PM -0600, Gustavo A. R. Silva wrote:
> Notice that the use of the bitwise OR operator '|' always leads to
> true in this particular case, which seems a bit suspicious due to
> the context in which this expression is being used.
> 
> Fix this by using bitwise AND operator '&' instead.
> 
> This bug was detected with the help of Coccinelle.
> 
> Fixes: 6a6cd11d4e57 ("perf test: Add test for the sched tracepoint format fields")
> Cc: stable@...r.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

nice catch

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka


> ---
> 
> NOTE: Notice that this code has been there since 2012. So, it would
>       be helpful if someone can double-check this. Thanks.
> 
>  tools/perf/tests/evsel-tp-sched.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/tests/evsel-tp-sched.c b/tools/perf/tests/evsel-tp-sched.c
> index 5f8501c68da4..5cbba70bcdd0 100644
> --- a/tools/perf/tests/evsel-tp-sched.c
> +++ b/tools/perf/tests/evsel-tp-sched.c
> @@ -17,7 +17,7 @@ static int perf_evsel__test_field(struct perf_evsel *evsel, const char *name,
>  		return -1;
>  	}
>  
> -	is_signed = !!(field->flags | TEP_FIELD_IS_SIGNED);
> +	is_signed = !!(field->flags & TEP_FIELD_IS_SIGNED);
>  	if (should_be_signed && !is_signed) {
>  		pr_debug("%s: \"%s\" signedness(%d) is wrong, should be %d\n",
>  			 evsel->name, name, is_signed, should_be_signed);
> -- 
> 2.20.1
>