2013-09-04 08:49:53

by Torsten Duwe

Subject: Resend: [PATCH 2/2] s390: provide hardware randomness from zcrypt card to /dev/random

[Checkpatch'ed, IBM folks Cc'ed]

Running completely virtualised, system Z severely lacks good true random sources.
Gathering entropy in a virtual environment is difficult. To compensate, there is
specialised crypto hardware which includes a source for hardware randomness;
the zcrypt driver is able to access this random source. This patch adds a kernel
thread that feeds the random bits via the interface created with the previous patch.

Signed-off-by: Torsten Duwe <[email protected]>

---
zcrypt_api.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 51 insertions(+)
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -38,6 +38,8 @@
#include <linux/atomic.h>
#include <asm/uaccess.h>
#include <linux/hw_random.h>
+#include <linux/kthread.h>
+#include <linux/delay.h>
#include <linux/debugfs.h>
#include <asm/debug.h>

@@ -99,6 +99,13 @@ static ssize_t zcrypt_online_store(struc

if (sscanf(buf, "%d\n", &online) != 1 || online < 0 || online > 1)
return -EINVAL;
+ if (zdev->ops->rng) {
+ if (zdev->online == 0 && online == 1)
+ zcrypt_rng_device_add();
+ if (zdev->online == 1 && online == 0)
+ zcrypt_rng_device_remove();
+
+ }
zdev->online = online;
ZCRYPT_DBF_DEV(DBF_INFO, zdev, "dev%04xo%dman", zdev->ap_dev->qid,
zdev->online);
@@ -1117,6 +1119,7 @@ static int zcrypt_rng_device_count;
static u32 *zcrypt_rng_buffer;
static int zcrypt_rng_buffer_index;
static DEFINE_MUTEX(zcrypt_rng_mutex);
+static struct task_struct *zcrypt_hwrng_fill;

static int zcrypt_rng_data_read(struct hwrng *rng, u32 *data)
{
@@ -1141,6 +1144,36 @@ static struct hwrng zcrypt_rng_dev = {
.data_read = zcrypt_rng_data_read,
};

+static int zcrypt_hwrng_fillfn(void *unused)
+{
+ long rc;
+
+ while (!kthread_should_stop()) {
+ rc = zcrypt_rng((char *)zcrypt_rng_buffer);
+ if (rc == -ENODEV || rc == -EINVAL || rc == -ENOMEM) {
+ pr_err("zcrypt_rng unavailable: %ld", rc);
+ break;
+ }
+ if (rc == -EAGAIN || rc == -ERESTARTSYS) {
+ pr_info("zcrypt_rng interrupted: %ld", rc);
+ msleep_interruptible(1000);
+ continue;
+ }
+ if (rc == 0) {
+ pr_err("zcrypt_rng: no data available");
+ msleep_interruptible(10000);
+ continue;
+ }
+ if (rc < 0) {
+ pr_err("zcrypt_rng unknown error: %ld", rc);
+ break;
+ }
+ add_hwgenerator_randomness((void *)zcrypt_rng_buffer, rc);
+ }
+ zcrypt_hwrng_fill = 0;
+ return 0;
+}
+
static int zcrypt_rng_device_add(void)
{
int rc = 0;
@@ -1157,6 +1189,12 @@ static int zcrypt_rng_device_add(void)
if (rc)
goto out_free;
zcrypt_rng_device_count = 1;
+ zcrypt_hwrng_fill = kthread_run(zcrypt_hwrng_fillfn,
+ NULL, "zc_hwrng");
+ if (zcrypt_hwrng_fill == ERR_PTR(-ENOMEM)) {
+ pr_err("zcrypt_hwrng_fill thread creation failed");
+ zcrypt_hwrng_fill = 0;
+ }
} else
zcrypt_rng_device_count++;
mutex_unlock(&zcrypt_rng_mutex);
@@ -1174,6 +1211,10 @@ static void zcrypt_rng_device_remove(voi
mutex_lock(&zcrypt_rng_mutex);
zcrypt_rng_device_count--;
if (zcrypt_rng_device_count == 0) {
+ if (zcrypt_hwrng_fill) {
+ kthread_stop(zcrypt_hwrng_fill);
+ zcrypt_hwrng_fill = 0;
+ }
hwrng_unregister(&zcrypt_rng_dev);
free_page((unsigned long) zcrypt_rng_buffer);
}

2013-09-11 00:39:39

by Joe Perches

Subject: Re: Resend: [PATCH 2/2] s390: provide hardware randomness from zcrypt card to /dev/random

On Wed, 2013-09-04 at 10:48 +0200, Torsten Duwe wrote:
[]
> +++ b/drivers/s390/crypto/zcrypt_api.c

> @@ -1141,6 +1144,36 @@ static struct hwrng zcrypt_rng_dev = {
][
> +static int zcrypt_hwrng_fillfn(void *unused)
> +{
> + long rc;
> +
> + while (!kthread_should_stop()) {
> + rc = zcrypt_rng((char *)zcrypt_rng_buffer);
> + if (rc == -ENODEV || rc == -EINVAL || rc == -ENOMEM) {
> + pr_err("zcrypt_rng unavailable: %ld", rc);

please add terminating newlines

pr_err("zcrypt_rng unavailable: %ld\n", rc);

etc...