This patch adds an interface to the random pool for feeding entropy in-kernel.
It might be dangerous when some driver writers think they have "good"
randomness when really they haven't.
Signed-off-by: Torsten Duwe <[email protected]>
---
include/linux/hw_random.h | 2 ++
drivers/char/random.c | 20 ++++++++++++++++++++
2 files changed, 22 insertions(+)
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -47,5 +47,7 @@ struct hwrng {
extern int hwrng_register(struct hwrng *rng);
/** Unregister a Hardware Random Number Generator driver. */
extern void hwrng_unregister(struct hwrng *rng);
+/** Feed random bits into the pool. */
+extern void add_hwgenerator_randomness(const char *buffer, size_t count);
#endif /* LINUX_HWRANDOM_H_ */
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -250,6 +250,7 @@
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
+#include <linux/kthread.h>
#include <linux/percpu.h>
#include <linux/cryptohash.h>
#include <linux/fips.h>
@@ -796,6 +797,25 @@ add_disk_randomness(
}
#endif
+/* Interface for in-kernel drivers of true hardware RNGs.
+ * Those devices may produce endless random bits and will be throttled
+ * when our pool is full.
+ */
+void add_hwgenerator_randomness(const char *buffer, size_t count)
+{
+ struct entropy_store *poolp = &input_pool;
+
+ /* Suspend writing if we're above the trickle threshold.
+ * We'll be woken up again once below random_write_wakeup_thresh,
+ * or when the calling thread is about to terminate.
+ */
+ wait_event_interruptible(random_write_wait, kthread_should_stop() ||
+ input_pool.entropy_count <= trickle_thresh);
+ mix_pool_bytes(poolp, buffer, count, NULL);
+ credit_entropy_bits(poolp, count*8);
+}
+EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
+
/*********************************************************************
*
* Entropy extraction routines