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random: access input_pool_data directly rather than through pointer 

This gets rid of another abstraction we no longer need. It would be nice
if we could instead make pool an array rather than a pointer, but the
latent entropy plugin won't be able to do its magic in that case. So
instead we put all accesses to the input pool's actual data through the
input_pool_data array directly.

Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2022-01-15 14:40:04 +01:00
parent 18263c4e8e
commit 6c0eace6e1
1 changed files with 8 additions and 13 deletions
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21
drivers/char/random.c
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@ -496,17 +496,12 @@ MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
static u32 input_pool_data[POOL_WORDS] __latent_entropy;
static struct {
/* read-only data: */
u32 *pool;
/* read-write data: */
spinlock_t lock;
u16 add_ptr;
u16 input_rotate;
int entropy_count;
} input_pool = {
.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
.pool = input_pool_data
};
static ssize_t extract_entropy(void *buf, size_t nbytes, int min);
@ -544,15 +539,15 @@ static void _mix_pool_bytes(const void *in, int nbytes)
i = (i - 1) & POOL_WORDMASK;
/* XOR in the various taps */
w ^= input_pool.pool[i];
w ^= input_pool.pool[(i + POOL_TAP1) & POOL_WORDMASK];
w ^= input_pool.pool[(i + POOL_TAP2) & POOL_WORDMASK];
w ^= input_pool.pool[(i + POOL_TAP3) & POOL_WORDMASK];
w ^= input_pool.pool[(i + POOL_TAP4) & POOL_WORDMASK];
w ^= input_pool.pool[(i + POOL_TAP5) & POOL_WORDMASK];
w ^= input_pool_data[i];
w ^= input_pool_data[(i + POOL_TAP1) & POOL_WORDMASK];
w ^= input_pool_data[(i + POOL_TAP2) & POOL_WORDMASK];
w ^= input_pool_data[(i + POOL_TAP3) & POOL_WORDMASK];
w ^= input_pool_data[(i + POOL_TAP4) & POOL_WORDMASK];
w ^= input_pool_data[(i + POOL_TAP5) & POOL_WORDMASK];
/* Mix the result back in with a twist */
input_pool.pool[i] = (w >> 3) ^ twist_table[w & 7];
input_pool_data[i] = (w >> 3) ^ twist_table[w & 7];
/*
* Normally, we add 7 bits of rotation to the pool.
@ -1369,7 +1364,7 @@ static void extract_buf(u8 *out)
/* Generate a hash across the pool */
spin_lock_irqsave(&input_pool.lock, flags);
blake2s_update(&state, (const u8 *)input_pool.pool, POOL_BYTES);
blake2s_update(&state, (const u8 *)input_pool_data, POOL_BYTES);
blake2s_final(&state, hash); /* final zeros out state */
/*