[PATCH 3/4] random: Seed pools from arch_get_slow_rng_u64 at startup

[Andy Lutomirski]

This should help solve the problem of guests starting out with
predictable RNG state.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
---
 drivers/char/random.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0a7ac0a..bd88a24 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1248,7 +1248,7 @@ EXPORT_SYMBOL(get_random_bytes_arch);
  */
 static void init_std_data(struct entropy_store *r)
 {
-	int i;
+	int i, slow_rng_bits = 0;
 	ktime_t now = ktime_get_real();
 	unsigned long rv;
 
@@ -1261,6 +1261,18 @@ static void init_std_data(struct entropy_store *r)
 		mix_pool_bytes(r, &rv, sizeof(rv), NULL);
 	}
 	mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
+
+	for (i = 0; i < 4; i++) {
+		u64 rv64;
+
+		if (arch_get_slow_rng_u64(&rv64)) {
+			mix_pool_bytes(r, &rv64, sizeof(rv64), NULL);
+			slow_rng_bits += 8 * sizeof(rv64);
+		}
+	}
+	if (slow_rng_bits)
+		pr_info("random: seeded %s pool with %d bits of arch slow rng data\n",
+		       r->name, slow_rng_bits);
 }
 
 /*
-- 
1.9.3

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