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From:   Florian Weimer <fweimer@redhat.com>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     linux-kernel@vger.kernel.org, patches@lists.linux.dev,
        tglx@linutronix.de, linux-crypto@vger.kernel.org,
        linux-api@vger.kernel.org, x86@kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>,
        Carlos O'Donell <carlos@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Christian Brauner <brauner@kernel.org>
Subject: Re: [PATCH v10 3/4] random: introduce generic vDSO getrandom()
 implementation
References: <20221129210639.42233-1-Jason@zx2c4.com>
        <20221129210639.42233-4-Jason@zx2c4.com>
Date:   Wed, 30 Nov 2022 11:44:30 +0100
In-Reply-To: <20221129210639.42233-4-Jason@zx2c4.com> (Jason A. Donenfeld's
        message of "Tue, 29 Nov 2022 22:06:38 +0100")
Message-ID: <878rjs7mcx.fsf@oldenburg.str.redhat.com>
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* Jason A. Donenfeld:

> diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
> index 73eb622e7663..9ae4d76b36c7 100644
> --- a/include/vdso/datapage.h
> +++ b/include/vdso/datapage.h
> @@ -109,6 +109,16 @@ struct vdso_data {
>  	struct arch_vdso_data	arch_data;
>  };
>  
> +/**
> + * struct vdso_rng_data - vdso RNG state information
> + * @generation:	a counter representing the number of RNG reseeds
> + * @is_ready:	whether the RNG is initialized
> + */
> +struct vdso_rng_data {
> +	unsigned long	generation;
> +	bool		is_ready;
> +};
> +

I don't think you can use a type like long here.  The header says this:

 * vdso_data will be accessed by 64 bit and compat code at the same time
 * so we should be careful before modifying this structure.

So the ABI must be same for 32-bit and 64-bit mode, and long isn't.

Thanks,
Florian