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    Subject[PATCH v8 6/7] random: early initialization of ChaCha constants
    Date
    Previously, the ChaCha constants for the primary pool were only
    initialized once rand_initialize() calls crng_initialize_primary().
    However, some randomness is actually extracted from the primary pool
    beforehand, e.g. by kmem_cache_create(). Therefore, statically
    initialize the ChaCha constants for the primary pool.

    In exchange, we can remove the dynamic initialization in
    crng_initialize_primary(), as it is only called - as the name suggests -
    for the primary pool. Therefore, no parameter to this function is needed.

    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    ---
    drivers/char/random.c | 10 +++++++---
    include/crypto/chacha.h | 15 +++++++++++----
    2 files changed, 18 insertions(+), 7 deletions(-)

    diff --git a/drivers/char/random.c b/drivers/char/random.c
    index 9b5eb6cf82ce..a5bf662578cb 100644
    --- a/drivers/char/random.c
    +++ b/drivers/char/random.c
    @@ -457,6 +457,10 @@ struct crng_state {

    static struct crng_state primary_crng = {
    .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
    + .state[0] = CHACHA_CONSTANT_EXPA, /* "expa" */
    + .state[1] = CHACHA_CONSTANT_ND_3, /* "nd 3" */
    + .state[2] = CHACHA_CONSTANT_2_BY, /* "2-by" */
    + .state[3] = CHACHA_CONSTANT_TE_K, /* "te k" */
    };

    /*
    @@ -823,9 +827,9 @@ static void __maybe_unused crng_initialize_secondary(struct crng_state *crng)
    crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
    }

    -static void __init crng_initialize_primary(struct crng_state *crng)
    +static void __init crng_initialize_primary(void)
    {
    - chacha_init_consts(crng->state);
    + struct crng_state *crng = &primary_crng;
    _extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0);
    if (crng_init_try_arch_early(crng) && trust_cpu && crng_init < 2) {
    invalidate_batched_entropy();
    @@ -1797,7 +1801,7 @@ int __init rand_initialize(void)
    init_std_data(&input_pool);
    if (crng_need_final_init)
    crng_finalize_init(&primary_crng);
    - crng_initialize_primary(&primary_crng);
    + crng_initialize_primary();
    crng_global_init_time = jiffies;
    if (ratelimit_disable) {
    urandom_warning.interval = 0;
    diff --git a/include/crypto/chacha.h b/include/crypto/chacha.h
    index dabaee698718..147e56fc755e 100644
    --- a/include/crypto/chacha.h
    +++ b/include/crypto/chacha.h
    @@ -47,12 +47,19 @@ static inline void hchacha_block(const u32 *state, u32 *out, int nrounds)
    hchacha_block_generic(state, out, nrounds);
    }

    +enum chacha_constants { /* expand 32-byte k */
    + CHACHA_CONSTANT_EXPA = 0x61707865U,
    + CHACHA_CONSTANT_ND_3 = 0x3320646eU,
    + CHACHA_CONSTANT_2_BY = 0x79622d32U,
    + CHACHA_CONSTANT_TE_K = 0x6b206574U
    +};
    +
    static inline void chacha_init_consts(u32 *state)
    {
    - state[0] = 0x61707865; /* "expa" */
    - state[1] = 0x3320646e; /* "nd 3" */
    - state[2] = 0x79622d32; /* "2-by" */
    - state[3] = 0x6b206574; /* "te k" */
    + state[0] = CHACHA_CONSTANT_EXPA; /* "expa" */
    + state[1] = CHACHA_CONSTANT_ND_3; /* "nd 3" */
    + state[2] = CHACHA_CONSTANT_2_BY; /* "2-by" */
    + state[3] = CHACHA_CONSTANT_TE_K; /* "te k" */
    }

    void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
    --
    2.34.1
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