1 files changed, 64 insertions, 5 deletions

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 334601cc81cf..48b3c812b9ec 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -38,6 +38,7 @@
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/miscdevice.h>
+#include <linux/kthread.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/random.h>
@@ -50,10 +51,18 @@
 
 
 static struct hwrng *current_rng;
+static struct task_struct *hwrng_fill;
 static LIST_HEAD(rng_list);
 static DEFINE_MUTEX(rng_mutex);
 static int data_avail;
-static u8 *rng_buffer;
+static u8 *rng_buffer, *rng_fillbuf;
+static unsigned short current_quality = 700; /* an arbitrary 70% */
+
+module_param(current_quality, ushort, 0644);
+MODULE_PARM_DESC(current_quality,
+                 "current hwrng entropy estimation per mill");
+
+static void start_khwrngd(void);
 
 static size_t rng_buffer_size(void)
 {
@@ -62,9 +71,18 @@ static size_t rng_buffer_size(void)
 
 static inline int hwrng_init(struct hwrng *rng)
 {
-        if (!rng->init)
-                return 0;
-        return rng->init(rng);
+        int err;
+
+        if (rng->init) {
+                err = rng->init(rng);
+                if (err)
+                        return err;
+        }
+
+        if (current_quality > 0 && !hwrng_fill)
+                start_khwrngd();
+
+        return 0;
 }
 
 static inline void hwrng_cleanup(struct hwrng *rng)
@@ -300,6 +318,36 @@ err_misc_dereg:
         goto out;
 }
 
+static int hwrng_fillfn(void *unused)
+{
+        long rc;
+
+        while (!kthread_should_stop()) {
+                if (!current_rng)
+                        break;
+                rc = rng_get_data(current_rng, rng_fillbuf,
+                                  rng_buffer_size(), 1);
+                if (rc <= 0) {
+                        pr_warn("hwrng: no data available\n");
+                        msleep_interruptible(10000);
+                        continue;
+                }
+                add_hwgenerator_randomness((void *)rng_fillbuf, rc,
+                                           (rc*current_quality)>>10);
+        }
+        hwrng_fill = 0;
+        return 0;
+}
+
+static void start_khwrngd(void)
+{
+        hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
+        if (hwrng_fill == ERR_PTR(-ENOMEM)) {
+                pr_err("hwrng_fill thread creation failed");
+                hwrng_fill = NULL;
+        }
+}
+
 int hwrng_register(struct hwrng *rng)
 {
         int err = -EINVAL;
@@ -320,6 +368,13 @@ int hwrng_register(struct hwrng *rng)
                 if (!rng_buffer)
                         goto out_unlock;
         }
+        if (!rng_fillbuf) {
+                rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
+                if (!rng_fillbuf) {
+                        kfree(rng_buffer);
+                        goto out_unlock;
+                }
+        }
 
         /* Must not register two RNGs with the same name. */
         err = -EEXIST;
@@ -375,8 +430,11 @@ void hwrng_unregister(struct hwrng *rng)
                                 current_rng = NULL;
                 }
         }
-        if (list_empty(&rng_list))
+        if (list_empty(&rng_list)) {
                 unregister_miscdev();
+                if (hwrng_fill)
+                        kthread_stop(hwrng_fill);
+        }
 
         mutex_unlock(&rng_mutex);
 }
@@ -387,6 +445,7 @@ static void __exit hwrng_exit(void)
         mutex_lock(&rng_mutex);
         BUG_ON(current_rng);
         kfree(rng_buffer);
+        kfree(rng_fillbuf);
         mutex_unlock(&rng_mutex);
 }