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From
SubjectRe: [PATCH v35 01/13] Linux Random Number Generator
Date
Am Freitag, 18. September 2020, 15:02:17 CEST schrieb kernel test robot:

Hi,

> All errors (new ones prefixed by >>):
> >> drivers/char/lrng/lrng_chacha20.c:33:8: error: structure variable
> >> 'chacha20' with 'latent_entropy' attribute has a non-integer field
> >> 'block'
> 33 | struct chacha20_state chacha20 __latent_entropy;
>
> | ^~~~~~~~~~~~~~
>
> #
> https://github.com/0day-ci/linux/commit/ecb964754fd80cca434d6d2ad6db8f28a15
> 92fa1 git remote add linux-review https://github.com/0day-ci/linux
> git fetch --no-tags linux-review
> Stephan-M-ller/dev-random-a-new-approach/20200918-181505 git checkout
> ecb964754fd80cca434d6d2ad6db8f28a1592fa1
> vim +33 drivers/char/lrng/lrng_chacha20.c
>
> 27
> 28 /*
> 29 * Have a static memory blocks for the ChaCha20 DRNG instance to
> avoid calling 30 * kmalloc too early in the boot cycle. For
subsequent
> allocation requests, 31 * such as per-NUMA-node DRNG instances,
kmalloc
> will be used. 32 */
>
> > 33 struct chacha20_state chacha20 __latent_entropy;

I do not think this report is valid. The following definitions apply:

struct chacha20_state {
struct chacha20_block block;
};

struct chacha20_block {
u32 constants[4];
union {
#define CHACHA_KEY_SIZE_WORDS (CHACHA_KEY_SIZE / sizeof(u32))
u32 u[CHACHA_KEY_SIZE_WORDS];
u8 b[CHACHA_KEY_SIZE];
} key;
u32 counter;
u32 nonce[3];
};


This implies that struct chacha20_state and thus the chacha20 variable is a
linear buffer with in total 4 + 8 + 1 + 3 = 16 32-bit integers which are at
least aligned on a 32-bit boundary and are designated as u32 integers.

Please let me know if I need to make a tweak to the definitions to convince
the code analyzer it is a flat linear buffer consisting of integers and thus
to understand the structure correctly.

Thanks a lot.

Ciao
Stephan


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