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Commit adc782da authored by Matt Mackall's avatar Matt Mackall Committed by Linus Torvalds
Browse files

random: simplify and rename credit_entropy_store 



- emphasize bits in the name
- make zero bits lock-free
- simplify logic

Signed-off-by: default avatarMatt Mackall <mpm@selenic.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e68e5b66

drivers/char/random.c

+15 −17
Original line number Diff line number Diff line
@@ -441,7 +441,7 @@ static struct entropy_store nonblocking_pool = { 
/*

 * This function adds bytes into the entropy "pool".  It does not

 * update the entropy estimate.  The caller should call

 * credit_entropy_store if this is appropriate.

 * credit_entropy_bits if this is appropriate.

 *

 * The pool is stirred with a primitive polynomial of the appropriate

 * degree, and then twisted.  We twist by three bits at a time because
@@ -515,24 +515,22 @@ static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes) 
/*

 * Credit (or debit) the entropy store with n bits of entropy

 */

static void credit_entropy_store(struct entropy_store *r, int nbits)

static void credit_entropy_bits(struct entropy_store *r, int nbits)

{

	unsigned long flags;



	if (!nbits)

		return;



	spin_lock_irqsave(&r->lock, flags);



	if (r->entropy_count + nbits < 0) {

		DEBUG_ENT("negative entropy/overflow (%d+%d)\n",

			  r->entropy_count, nbits);

	DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);

	r->entropy_count += nbits;

	if (r->entropy_count < 0) {

		DEBUG_ENT("negative entropy/overflow\n");

		r->entropy_count = 0;

	} else if (r->entropy_count + nbits > r->poolinfo->POOLBITS) {

	} else if (r->entropy_count > r->poolinfo->POOLBITS)

		r->entropy_count = r->poolinfo->POOLBITS;

	} else {

		r->entropy_count += nbits;

		if (nbits)

			DEBUG_ENT("added %d entropy credits to %s\n",

				  nbits, r->name);

	}



	/* should we wake readers? */

	if (r == &input_pool && r->entropy_count >= random_read_wakeup_thresh)
@@ -619,7 +617,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) 
		 * Round down by 1 bit on general principles,

		 * and limit entropy entimate to 12 bits.

		 */

		credit_entropy_store(&input_pool,

		credit_entropy_bits(&input_pool,

				    min_t(int, fls(delta>>1), 11));

	}

out:
@@ -702,7 +700,7 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) 
		bytes = extract_entropy(r->pull, tmp, bytes,

					random_read_wakeup_thresh / 8, rsvd);

		mix_pool_bytes(r, tmp, bytes);

		credit_entropy_store(r, bytes*8);

		credit_entropy_bits(r, bytes*8);

	}

}
@@ -1073,7 +1071,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) 
			return -EPERM;

		if (get_user(ent_count, p))

			return -EFAULT;

		credit_entropy_store(&input_pool, ent_count);

		credit_entropy_bits(&input_pool, ent_count);

		return 0;

	case RNDADDENTROPY:

		if (!capable(CAP_SYS_ADMIN))
@@ -1088,7 +1086,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) 
				    size);

		if (retval < 0)

			return retval;

		credit_entropy_store(&input_pool, ent_count);

		credit_entropy_bits(&input_pool, ent_count);

		return 0;

	case RNDZAPENTCNT:

	case RNDCLEARPOOL: