linux-kernel - [RFC PATCH 12/41] random: convert add_interrupt_randomness() to queued

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Date:   Mon, 21 Sep 2020 09:58:28 +0200
From:   Nicolai Stange <nstange@...e.de>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-crypto@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Alexander E. Patrakov" <patrakov@...il.com>,
        "Ahmed S. Darwish" <darwish.07@...il.com>,
        Willy Tarreau <w@....eu>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Vito Caputo <vcaputo@...garu.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, Ray Strode <rstrode@...hat.com>,
        William Jon McCann <mccann@....edu>,
        zhangjs <zachary@...shancloud.com>,
        Andy Lutomirski <luto@...nel.org>,
        Florian Weimer <fweimer@...hat.com>,
        Lennart Poettering <mzxreary@...inter.de>,
        Peter Matthias <matthias.peter@....bund.de>,
        Marcelo Henrique Cerri <marcelo.cerri@...onical.com>,
        Roman Drahtmueller <draht@...altsekun.de>,
        Neil Horman <nhorman@...hat.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Julia Lawall <julia.lawall@...ia.fr>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Andy Lavr <andy.lavr@...il.com>,
        Eric Biggers <ebiggers@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Stephan Müller <smueller@...onox.de>,
        Torsten Duwe <duwe@...e.de>, Petr Tesarik <ptesarik@...e.cz>,
        Nicolai Stange <nstange@...e.de>
Subject: [RFC PATCH 12/41] random: convert add_interrupt_randomness() to queued_entropy API

In an effort to drop __credit_entropy_bits_fast() in favor of the new
__queue_entropy()/__dispatch_queued_entropy_fast() API, convert
add_interrupt_randomness() from the former to the latter.

There is no change in functionality at this point, because
__credit_entropy_bits_fast() has already been reimplemented on top of the
new API before.

Signed-off-by: Nicolai Stange <nstange@...e.de>
---
 drivers/char/random.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index e8c86abde901..bd3774c6be4b 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1512,6 +1512,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
 	unsigned long		seed;
 	int			credit = 0;
 	bool			reseed;
+	struct queued_entropy	q = { 0 };
 
 	if (cycles == 0)
 		cycles = get_reg(fast_pool, regs);
@@ -1546,24 +1547,27 @@ void add_interrupt_randomness(int irq, int irq_flags)
 	if (!spin_trylock(&r->lock))
 		return;
 
-	fast_pool->last = now;
-	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
-
 	/*
 	 * If we have architectural seed generator, produce a seed and
-	 * add it to the pool.  For the sake of paranoia don't let the
-	 * architectural seed generator dominate the input from the
-	 * interrupt noise.
+	 * add it to the pool further below. For the sake of paranoia
+	 * don't let the architectural seed generator dominate the
+	 * input from the interrupt noise.
 	 */
-	if (arch_get_random_seed_long(&seed)) {
-		__mix_pool_bytes(r, &seed, sizeof(seed));
-		credit = 1;
-	}
+	credit = !!arch_get_random_long(&seed);
 
+	fast_pool->last = now;
 	fast_pool->count = 0;
-
 	/* award one bit for the contents of the fast pool */
-	reseed = __credit_entropy_bits_fast(r, credit + 1);
+	__queue_entropy(r, &q, (credit + 1) << ENTROPY_SHIFT);
+	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
+	if (credit) {
+		/*
+		 * A seed has been obtained from
+		 * arch_get_random_seed_long() above, mix it in.
+		 */
+		__mix_pool_bytes(r, &seed, sizeof(seed));
+	}
+	reseed = __dispatch_queued_entropy_fast(r, &q);
 	spin_unlock(&r->lock);
 	if (reseed)
 		crng_reseed(&primary_crng, r);
-- 
2.26.2