linux-kernel - Re: [PATCH] perf: tests: Disable breakpoint tests on ARM (32-bit)

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Message-ID: <20181120114157.GA25498@arm.com>
Date:   Tue, 20 Nov 2018 11:41:58 +0000
From:   Will Deacon <will.deacon@....com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>,
        Thomas Richter <tmricht@...ux.vnet.ibm.com>
Subject: Re: [PATCH] perf: tests: Disable breakpoint tests on ARM (32-bit)

On Fri, Nov 16, 2018 at 02:53:07PM -0800, Florian Fainelli wrote:
> breakpoint tests on the ARM 32-bit kernel are broken in several ways.
> 
> The breakpoint length requested does not necessarily match whether the
> function address has the Thumb bit (bit 0) set or not, and this does
> matter to the ARM kernel hw_breakpoint infrastructure. See [1] for
> background.
> 
> [1]: https://lkml.org/lkml/2018/11/15/205
> 
> As Will indicated, the overflow handling would require single-stepping
> which is not supported at the moment. Just disable those tests for the
> ARM 32-bit platforms.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  tools/perf/tests/bp_signal.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/tests/bp_signal.c b/tools/perf/tests/bp_signal.c
> index a467615c5a0e..3b5471ea2331 100644
> --- a/tools/perf/tests/bp_signal.c
> +++ b/tools/perf/tests/bp_signal.c
> @@ -296,7 +296,7 @@ bool test__bp_signal_is_supported(void)
>   * instruction breakpoint using the perf event interface.
>   * Once it's there we can release this.
>   */
> -#if defined(__powerpc__) || defined(__s390x__)
> +#if defined(__powerpc__) || defined(__s390x__) || defined(__arm__)
>  	return false;
>  #else

I'm ok with disabling the test, but the comment above this #if is all about
powerpc.

Will