This is required by vsprint, because it can't do things synchronously
from hardirq context, and it will be useful for an EFI notifier as well.
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
---
drivers/char/random.c | 30 ++++++++++++++++++++++++++++++
include/linux/random.h | 1 +
2 files changed, 31 insertions(+)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 6b7aca683b81..b3cad16ec567 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -84,6 +84,8 @@ static DEFINE_STATIC_KEY_FALSE(crng_is_ready);
/* Various types of waiters for crng_init->CRNG_READY transition. */
static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
static struct fasync_struct *fasync;
+static DEFINE_SPINLOCK(random_ready_chain_lock);
+static RAW_NOTIFIER_HEAD(random_ready_chain);
/* Control how we warn userspace. */
static struct ratelimit_state urandom_warning =
@@ -140,6 +142,33 @@ int wait_for_random_bytes(void)
}
EXPORT_SYMBOL(wait_for_random_bytes);
+/*
+ * Add a callback function that will be invoked when the crng is initialised,
+ * or immediately if it already has been.
+ */
+int __cold notify_on_rng_initialized(struct notifier_block *nb)
+{
+ unsigned long flags;
+ int ret = 0;
+
+ spin_lock_irqsave(&random_ready_chain_lock, flags);
+ if (crng_ready())
+ nb->notifier_call(nb, 0, NULL);
+ else
+ ret = raw_notifier_chain_register(&random_ready_chain, nb);
+ spin_unlock_irqrestore(&random_ready_chain_lock, flags);
+ return ret;
+}
+
+static void __cold process_random_ready_list(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&random_ready_chain_lock, flags);
+ raw_notifier_call_chain(&random_ready_chain, 0, NULL);
+ spin_unlock_irqrestore(&random_ready_chain_lock, flags);
+}
+
#define warn_unseeded_randomness() \
if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \
printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \
@@ -685,6 +714,7 @@ static void __cold _credit_init_bits(size_t bits)
crng_reseed(); /* Sets crng_init to CRNG_READY under base_crng.lock. */
if (static_key_initialized)
execute_in_process_context(crng_set_ready, &set_ready);
+ process_random_ready_list();
wake_up_interruptible(&crng_init_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
pr_notice("crng init done\n");
diff --git a/include/linux/random.h b/include/linux/random.h
index acaa328fb34d..566ffc3ab80d 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -119,6 +119,7 @@ void __init random_init_early(const char *command_line);
void __init random_init(void);
bool rng_is_initialized(void);
int wait_for_random_bytes(void);
+int notify_on_rng_initialized(struct notifier_block *nb);
/* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes).
* Returns the result of the call to wait_for_random_bytes. */
--
2.38.1
