Re: [PATCH v2 1/1] arm: perf: Fix ARCH=arm build with GCC

Uwe Kleine-König
2023-12-15T18:20:51Z

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On Fri, Dec 15, 2023 at 05:56:48PM +0000, James Clark wrote:
> LLVM ignores everything inside the if statement and doesn't generate
> errors, but GCC doesn't ignore it, resulting in the following error:
>
> drivers/perf/arm_pmuv3.c: In function ‘armv8pmu_write_evtype’:
> include/linux/bits.h:34:29: error: left shift count >= width of type [-Werror=shift-count-overflow]
> 34 | (((~UL(0)) - (UL(1) << (l)) + 1) & \
>
> Fix it by using GENMASK_ULL which doesn't overflow on arm32 (even though
> the value is never used there).
>
> Fixes: 3115ee021bfb ("arm64: perf: Include threshold control fields in PMEVTYPER mask")
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Closes: https://lore.kernel.org/linux-arm-kernel/20231215120817.h2f3akgv72zhrtqo@pengutronix.de/
> Signed-off-by: James Clark <james.clark@arm.com>
> ---
> include/linux/perf/arm_pmuv3.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/perf/arm_pmuv3.h b/include/linux/perf/arm_pmuv3.h
> index 0f4d62ef3a9a..46377e134d67 100644
> --- a/include/linux/perf/arm_pmuv3.h
> +++ b/include/linux/perf/arm_pmuv3.h
> @@ -234,8 +234,8 @@
> * PMXEVTYPER: Event selection reg
> */
> #define ARMV8_PMU_EVTYPE_EVENT GENMASK(15, 0) /* Mask for EVENT bits */
> -#define ARMV8_PMU_EVTYPE_TH GENMASK(43, 32)
> -#define ARMV8_PMU_EVTYPE_TC GENMASK(63, 61)
> +#define ARMV8_PMU_EVTYPE_TH GENMASK_ULL(43, 32) /* arm64 only */
> +#define ARMV8_PMU_EVTYPE_TC GENMASK_ULL(63, 61) /* arm64 only */

As expected this fixes compilation on my end, too and it's nicer than
v1.

Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Thanks
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
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