linux-kernel - [PATCH v3 4/5] random: Log how many bits we managed to seed with in init_std

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Date:	Wed, 16 Jul 2014 14:45:36 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	kvm@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Theodore Ts'o <tytso@....edu>, linux-kernel@...r.kernel.org,
	Kees Cook <keescook@...omium.org>, x86@...nel.org
Cc:	Daniel Borkmann <dborkman@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, bsd@...hat.com,
	Andy Lutomirski <luto@...capital.net>
Subject: [PATCH v3 4/5] random: Log how many bits we managed to seed with in init_std_data

This is useful for making sure that init_std_data is working
correctly and for allaying fear when this happens:

    random: xyz urandom read with SMALL_NUMBER bits of entropy available

Signed-off-by: Andy Lutomirski <luto@...capital.net>
---
 drivers/char/random.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 17ad33d..10e9642 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1251,12 +1251,16 @@ static void init_std_data(struct entropy_store *r)
 	int i;
 	ktime_t now = ktime_get_real();
 	unsigned long rv;
+	int arch_seed_bits = 0, arch_random_bits = 0, slow_rng_bits = 0;
 
 	r->last_pulled = jiffies;
 	mix_pool_bytes(r, &now, sizeof(now), NULL);
 	for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
-		if (!arch_get_random_seed_long(&rv) &&
-		    !arch_get_random_long(&rv))
+		if (arch_get_random_seed_long(&rv))
+			arch_seed_bits += 8 * sizeof(rv);
+		else if (arch_get_random_long(&rv))
+			arch_random_bits += 8 * sizeof(rv);
+		else
 			rv = random_get_entropy();
 		mix_pool_bytes(r, &rv, sizeof(rv), NULL);
 	}
@@ -1265,9 +1269,14 @@ static void init_std_data(struct entropy_store *r)
 	for (i = 0; i < 4; i++) {
 		u64 rv64;
 
-		if (arch_get_slow_rng_u64(&rv64))
+		if (arch_get_slow_rng_u64(&rv64)) {
 			mix_pool_bytes(r, &rv64, sizeof(rv64), NULL);
+			slow_rng_bits += 8 * sizeof(rv64);
+		}
 	}
+
+	pr_info("random: seeded %s pool with %d bits of arch random seed, %d bits of arch random, and %d bits of arch slow rng\n",
+		r->name, arch_seed_bits, arch_random_bits, slow_rng_bits);
 }
 
 /*
-- 
1.9.3

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