linux-kernel - Re: [PATCH v3] selftests/futex: Convert 32bit timespec struct to 64bit version for 32bit compatibility mode

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Message-ID: <87y0t6jqnp.ffs@tglx>
Date: Wed, 02 Jul 2025 22:15:06 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Terry Tritton <terry.tritton@...aro.org>, Shuah Khan <shuah@...nel.org>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Darren Hart <dvhart@...radead.org>, Davidlohr Bueso <dave@...olabs.net>,
 André Almeida <andrealmeid@...lia.com>
Cc: ttritton@...gle.com, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, Terry Tritton <terry.tritton@...aro.org>,
 Wei Gao <wegao@...e.com>
Subject: Re: [PATCH v3] selftests/futex: Convert 32bit timespec struct to
 64bit version for 32bit compatibility mode

On Wed, Jul 02 2025 at 11:21, Terry Tritton wrote:

> Futex_waitv can not accept old_timespec32 struct, so userspace should

sys_futex_wait()

> convert it from 32bit to 64bit before syscall in 32bit compatible mode.
>
> This fix is based off [1]
>
> Link: https://lore.kernel.org/all/20231203235117.29677-1-wegao@suse.com/ [1]
>
> Originally-by: Wei Gao <wegao@...e.com>
> Signed-off-by: Terry Tritton <terry.tritton@...aro.org>
> ---
> Changes in v3:
> - Fix signed-off-by chain but for real this time
>
> Changes in v2:
> - Fix signed-off-by chain
>
>  .../testing/selftests/futex/include/futex2test.h  | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/tools/testing/selftests/futex/include/futex2test.h b/tools/testing/selftests/futex/include/futex2test.h
> index ea79662405bc..6780e51eb2d6 100644
> --- a/tools/testing/selftests/futex/include/futex2test.h
> +++ b/tools/testing/selftests/futex/include/futex2test.h
> @@ -55,6 +55,13 @@ struct futex32_numa {
>  	futex_t numa;
>  };
>  
> +#if !defined(__LP64__)
> +struct timespec64 {
> +	int64_t tv_sec;
> +	int64_t tv_nsec;
> +};
> +#endif

Why not use __kernel_timespec which is the actual data type that syscall
requests?

> +
>  /**
>   * futex_waitv - Wait at multiple futexes, wake on any
>   * @waiters:    Array of waiters
> @@ -65,7 +72,15 @@ struct futex32_numa {
>  static inline int futex_waitv(volatile struct futex_waitv *waiters, unsigned long nr_waiters,
>  			      unsigned long flags, struct timespec *timo, clockid_t clockid)
>  {
> +#if !defined(__LP64__)
> +	struct timespec64 timo64 = {0};
> +
> +	timo64.tv_sec = timo->tv_sec;
> +	timo64.tv_nsec = timo->tv_nsec;
> +	return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, &timo64, clockid);
> +#else
>  	return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, timo, clockid);
> +#endif

You simply can do

        struct __kernel_timespec ts = {
        	.tv_sec = timo->tv_sec,
                .tv_nsec = timo->tv_nsec,
        };

  	return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, &ts, clockid);
        
unconditionally. No?

Thanks,

        tglx