Instead of having only one hwrng feeding /dev/random at a time, maintain
a list of devices and cycle between them when filling the entropy pool.
Signed-off-by: Keith Packard <kei...@keithp.com>
---
drivers/char/hw_random/core.c | 155 +++++++++++++++++++++++++++---------------
include/linux/hw_random.h | 2 +
2 files changed, 104 insertions(+), 53 deletions(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 9203f2d..97fd4a7 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -51,10 +51,10 @@
#define RNG_MISCDEV_MINOR 183 /* official */
-static struct hwrng *current_rng;
+static LIST_HEAD(active_rng);
static struct task_struct *hwrng_fill;
static LIST_HEAD(rng_list);
-/* Protects rng_list and current_rng */
+/* Protects rng_list and active_rng */
static DEFINE_MUTEX(rng_mutex);
/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
static DEFINE_MUTEX(reading_mutex);
@@ -70,7 +70,6 @@ module_param(default_quality, ushort, 0644);
MODULE_PARM_DESC(default_quality,
"default entropy content of hwrng per mill");
-static void drop_current_rng(void);
static int hwrng_init(struct hwrng *rng);
static void start_khwrngd(void);
@@ -104,31 +103,65 @@ static inline void cleanup_rng(struct kref *kref)
complete(&rng->cleanup_done);
}
-static int set_current_rng(struct hwrng *rng)
+static unsigned short rng_quality(struct hwrng *rng)
+{
+ unsigned short quality;
+
+ quality = current_quality;
+ if (!quality) {
+ quality = rng->quality;
+ if (!quality)
+ quality = default_quality;
+ }
+ if (quality > 1024)
+ quality = 1024;
+ return quality;
+}
+
+static int add_active_rng(struct hwrng *rng)
{
int err;
BUG_ON(!mutex_is_locked(&rng_mutex));
+ if (rng->is_active)
+ return 0;
+
err = hwrng_init(rng);
if (err)
return err;
- drop_current_rng();
- current_rng = rng;
+ if (rng_quality(rng) != 0) {
+ rng->is_active = true;
+ list_add(&rng->active, &active_rng);
+ if (!hwrng_fill)
+ start_khwrngd();
+ }
return 0;
}
-static void drop_current_rng(void)
+static int drop_active_rng(struct hwrng *rng)
{
BUG_ON(!mutex_is_locked(&rng_mutex));
- if (!current_rng)
- return;
+ if (!rng->is_active)
+ return 0;
+
+ list_del(&rng->active);
+ rng->is_active = false;
/* decrease last reference for triggering the cleanup */
- kref_put(¤t_rng->ref, cleanup_rng);
- current_rng = NULL;
+ kref_put(&rng->ref, cleanup_rng);
+
+ if (list_empty(&active_rng) && hwrng_fill)
+ kthread_stop(hwrng_fill);
+
+ return 0;
+}
+
+static struct hwrng *first_active_rng(void)
+{
+ return list_first_entry_or_null(&active_rng, struct hwrng, active);
}
/* Returns ERR_PTR(), NULL or refcounted hwrng */
@@ -139,18 +172,32 @@ static struct hwrng *get_current_rng(void)
if (mutex_lock_interruptible(&rng_mutex))
return ERR_PTR(-ERESTARTSYS);
- rng = current_rng;
+ rng = first_active_rng();
if (rng)
kref_get(&rng->ref);
mutex_unlock(&rng_mutex);
+
return rng;
}
+static int next_rng(void)
+{
+ if (mutex_lock_interruptible(&rng_mutex))
+ return -ERESTARTSYS;
+
+ if (!list_empty(&active_rng) && !list_is_singular(&active_rng))
+ list_rotate_left(&active_rng);
+
+ mutex_unlock(&rng_mutex);
+
+ return 0;
+}
+
static void put_rng(struct hwrng *rng)
{
/*
- * Hold rng_mutex here so we serialize in case they set_current_rng
+ * Hold rng_mutex here so we serialize in case they add_active_rng
* on rng again immediately.
*/
mutex_lock(&rng_mutex);
@@ -178,15 +225,6 @@ static int hwrng_init(struct hwrng *rng)
skip_init:
add_early_randomness(rng);
- current_quality = rng->quality ? : default_quality;
- if (current_quality > 1024)
- current_quality = 1024;
-
- if (current_quality == 0 && hwrng_fill)
- kthread_stop(hwrng_fill);
- if (current_quality > 0 && !hwrng_fill)
- start_khwrngd();
-
return 0;
}
@@ -246,6 +284,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user
*buf,
bytes_read = rng_get_data(rng, rng_buffer,
rng_buffer_size(),
!(filp->f_flags & O_NONBLOCK));
+ next_rng();
if (bytes_read < 0) {
err = bytes_read;
goto out_unlock_reading;
@@ -320,20 +359,30 @@ static ssize_t hwrng_attr_current_store(struct device
*dev,
const char *buf, size_t len)
{
int err;
+ int add = 1;
struct hwrng *rng;
err = mutex_lock_interruptible(&rng_mutex);
if (err)
return -ERESTARTSYS;
+ if (*buf == '-') {
+ add = 0;
+ buf++;
+ } else if (*buf == '+') {
+ add = 1;
+ buf++;
+ }
err = -ENODEV;
list_for_each_entry(rng, &rng_list, list) {
if (sysfs_streq(rng->name, buf)) {
- err = 0;
- if (rng != current_rng)
- err = set_current_rng(rng);
+ if (add)
+ err = add_active_rng(rng);
+ else
+ err = drop_active_rng(rng);
break;
}
}
+
mutex_unlock(&rng_mutex);
return err ? : len;
@@ -343,17 +392,26 @@ static ssize_t hwrng_attr_current_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
- ssize_t ret;
+ int err;
struct hwrng *rng;
- rng = get_current_rng();
- if (IS_ERR(rng))
- return PTR_ERR(rng);
-
- ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
- put_rng(rng);
+ err = mutex_lock_interruptible(&rng_mutex);
+ if (err)
+ return -ERESTARTSYS;
+ buf[0] = '\0';
+ if (list_empty(&active_rng)) {
+ strlcat(buf, "none", PAGE_SIZE);
+ } else {
+ list_for_each_entry(rng, &active_rng, active) {
+ if (rng != first_active_rng())
+ strlcat(buf, " ", PAGE_SIZE);
+ strlcat(buf, rng->name, PAGE_SIZE);
+ }
+ }
+ strlcat(buf, "\n", PAGE_SIZE);
+ mutex_unlock(&rng_mutex);
- return ret;
+ return strlen(buf);
}
static ssize_t hwrng_attr_available_show(struct device *dev,
@@ -412,6 +470,7 @@ static int hwrng_fillfn(void *unused)
rng = get_current_rng();
if (IS_ERR(rng) || !rng)
break;
+ next_rng();
mutex_lock(&reading_mutex);
rc = rng_get_data(rng, rng_fillbuf,
rng_buffer_size(), 1);
@@ -442,7 +501,7 @@ static void start_khwrngd(void)
int hwrng_register(struct hwrng *rng)
{
int err = -EINVAL;
- struct hwrng *old_rng, *tmp;
+ struct hwrng *tmp;
if (rng->name == NULL ||
(rng->data_read == NULL && rng->read == NULL))
@@ -472,19 +531,18 @@ int hwrng_register(struct hwrng *rng)
goto out_unlock;
}
+ rng->is_active = false;
+
init_completion(&rng->cleanup_done);
complete(&rng->cleanup_done);
- old_rng = current_rng;
- err = 0;
- if (!old_rng) {
- err = set_current_rng(rng);
- if (err)
- goto out_unlock;
- }
+ err = add_active_rng(rng);
+ if (err)
+ goto out_unlock;
+
list_add_tail(&rng->list, &rng_list);
- if (old_rng && !rng->init) {
+ if (!rng->init) {
/*
* Use a new device's input to add some randomness to
* the system. If this rng device isn't going to be
@@ -507,16 +565,7 @@ void hwrng_unregister(struct hwrng *rng)
mutex_lock(&rng_mutex);
list_del(&rng->list);
- if (current_rng == rng) {
- drop_current_rng();
- if (!list_empty(&rng_list)) {
- struct hwrng *tail;
-
- tail = list_entry(rng_list.prev, struct hwrng, list);
-
- set_current_rng(tail);
- }
- }
+ drop_active_rng(rng);
if (list_empty(&rng_list)) {
mutex_unlock(&rng_mutex);
@@ -579,7 +628,7 @@ static int __init hwrng_modinit(void)
static void __exit hwrng_modexit(void)
{
mutex_lock(&rng_mutex);
- BUG_ON(current_rng);
+ WARN_ON(!list_empty(&active_rng));
kfree(rng_buffer);
kfree(rng_fillbuf);
mutex_unlock(&rng_mutex);
diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index 4f7d8f4..c655563 100644
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -45,7 +45,9 @@ struct hwrng {
unsigned short quality;
/* internal. */
+ bool is_active;
struct list_head list;
+ struct list_head active;
struct kref ref;
struct completion cleanup_done;
};
--
2.8.1
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