From:   Stephan Mueller <smueller@chronox.de>
To:     Tso Ted <tytso@mit.edu>, linux-crypto@vger.kernel.org,
        kernel test robot <lkp@intel.com>
Cc:     kbuild-all@lists.01.org, Willy Tarreau <w@1wt.eu>,
        Nicolai Stange <nstange@suse.de>,
        LKML <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "Alexander E. Patrakov" <patrakov@gmail.com>,
        "Ahmed S. Darwish" <darwish.07@gmail.com>
Subject: Re: [PATCH v43 01/15] Linux Random Number Generator
Date:   Mon, 22 Nov 2021 12:47:43 +0100
Message-ID: <5540546.7F5nsSknLy@tauon.chronox.de>
In-Reply-To: <202111221831.lPHo6KJJ-lkp@intel.com>
References: <4641592.OV4Wx5bFTl@positron.chronox.de> <202111221831.lPHo6KJJ-lkp@intel.com>
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Am Montag, 22. November 2021, 11:33:26 CET schrieb kernel test robot:

Hi,

> All errors (new ones prefixed by >>):
> >> drivers/char/lrng/lrng_chacha20.c:32:8: error: structure variable
> >> 'chacha20' with 'latent_entropy' attribute has a non-integer field
> >> 'block'
>       32 | struct chacha20_state chacha20 __latent_entropy;
> 
>          |        ^~~~~~~~~~~~~~
> 
> vim +32 drivers/char/lrng/lrng_chacha20.c

Thanks for the notification.

I think this is a false-positive discussed before. __latent_entropy is 
seemingly allowed for an entire linear buffer as seen in the declaration of 
the variable input_pool_data in driver/char/random.c which is an array of u32.

The struct chacha20_state is a linear buffer of u32 words. 

struct chacha20_block {
        u32 constants[4];
        union {
                u32 u[CHACHA_KEY_SIZE_WORDS];
                u8  b[CHACHA_KEY_SIZE];
        } key;
        u32 counter;
        u32 nonce[3];
};

Therefore it should be identical to the aforementioned example. The 
__latent_entropy marker therefore seems to be appropriate for this structure.

Ciao
Stephan