2 files changed, 25 insertions, 5 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index f67ae3e473ba..eacd61479112 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1038,17 +1038,34 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
 
 /*
  * This function is the exported kernel interface.  It returns some
- * number of good random numbers, suitable for seeding TCP sequence
- * numbers, etc.
+ * number of good random numbers, suitable for key generation, seeding
+ * TCP sequence numbers, etc.  It does not use the hw random number
+ * generator, if available; use get_random_bytes_arch() for that.
  */
 void get_random_bytes(void *buf, int nbytes)
 {
+        extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
+}
+EXPORT_SYMBOL(get_random_bytes);
+
+/*
+ * This function will use the architecture-specific hardware random
+ * number generator if it is available.  The arch-specific hw RNG will
+ * almost certainly be faster than what we can do in software, but it
+ * is impossible to verify that it is implemented securely (as
+ * opposed, to, say, the AES encryption of a sequence number using a
+ * key known by the NSA).  So it's useful if we need the speed, but
+ * only if we're willing to trust the hardware manufacturer not to
+ * have put in a back door.
+ */
+void get_random_bytes_arch(void *buf, int nbytes)
+{
         char *p = buf;
 
         while (nbytes) {
                 unsigned long v;
                 int chunk = min(nbytes, (int)sizeof(unsigned long));
-                
+
                 if (!arch_get_random_long(&v))
                         break;
                 
@@ -1057,9 +1074,11 @@ void get_random_bytes(void *buf, int nbytes)
                 nbytes -= chunk;
         }
 
-        extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
+        if (nbytes)
+                extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
 }
-EXPORT_SYMBOL(get_random_bytes);
+EXPORT_SYMBOL(get_random_bytes_arch);
+
 
 /*
  * init_std_data - initialize pool with system data
diff --git a/include/linux/random.h b/include/linux/random.h
index e14b4387354a..29e217a7e6d0 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -56,6 +56,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code,
 extern void add_interrupt_randomness(int irq, int irq_flags);
 
 extern void get_random_bytes(void *buf, int nbytes);
+extern void get_random_bytes_arch(void *buf, int nbytes);
 void generate_random_uuid(unsigned char uuid_out[16]);
 
 #ifndef MODULE