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

Andy Lutomirski
2014-07-16T02:48:09Z

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

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
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