random: printk notifications for urandom pool initialization

Print a notification to the console when the nonblocking pool is
initialized.  Also printk a warning when a process tries reading from
/dev/urandom before it is fully initialized.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

drivers/char/random.c

@@ -655,6 +655,9 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
 	r->entropy_total += nbits;
 	if (!r->initialized && nbits > 0) {
 		if (r->entropy_total > 128) {
+			if (r == &nonblocking_pool)
+				pr_notice("random: %s pool is initialized\n",
+					  r->name);
 			r->initialized = 1;
 			r->entropy_total = 0;
 		}
@@ -1327,7 +1330,14 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 static ssize_t
 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 {
-	int ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
+	int ret;
+
+	if (unlikely(nonblocking_pool.initialized == 0))
+		printk_once(KERN_NOTICE "random: %s urandom read "
+			    "with %d bits of entropy available\n",
+			    current->comm, nonblocking_pool.entropy_total);
+
+	ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
 
 	trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
 			   ENTROPY_BITS(&input_pool));