Re: [PATCH] s390/zcrypt: enable s390 hwrng to seed kernel entropy

From: Ingo Tuchscherer
Date: Mon Aug 11 2014 - 11:12:14 EST


On 08/11/2014 03:56 PM, Torsten Duwe wrote:
On Wed, Jul 30, 2014 at 02:17:36PM +0200, Ingo Tuchscherer wrote:
Set the 'quality' property in the zcrypt rng device structure to enable the
zcrypt hwrng device to take part in the kernel entropy seeding process.
A module parameter named hwrng_seed will be introduced to disable the
participation. By default this parameter is set to 1 (enabled).
I only had a one-liner that simply enabled it. I guess the extra switch
is for certification scenarios?
I introduced this switch for several reasons. I would like to have the possibility to prevent the card from being interrupted with rng queries (in case of heavy workload) or card verification/certification or other measurement processes.
Last but not least we are able to deactivate this feature in case of any failures/attacks.

Anyway,

Acked-by: Torsten Duwe <duwe@xxxxxxx>
Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@xxxxxxxxxx>
---
drivers/s390/crypto/ap_bus.c | 5 +++++
drivers/s390/crypto/ap_bus.h | 1 +
drivers/s390/crypto/zcrypt_api.c | 3 +++
3 files changed, 9 insertions(+)

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index 4038437..19fac5f 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -85,6 +85,11 @@ static int ap_thread_flag = 0;
module_param_named(poll_thread, ap_thread_flag, int, S_IRUSR|S_IRGRP);
MODULE_PARM_DESC(poll_thread, "Turn on/off poll thread, default is 0 (off).");
+int ap_hwrng_seed = 1;
+EXPORT_SYMBOL(ap_hwrng_seed);
+module_param_named(hwrng_seed, ap_hwrng_seed, int, S_IRUSR|S_IRGRP);
+MODULE_PARM_DESC(hwrng_seed, "Turn on/off hwrng auto seed, default is 1 (on).");
+
static struct device *ap_root_device = NULL;
static struct ap_config_info *ap_configuration;
static DEFINE_SPINLOCK(ap_device_list_lock);
diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
index 6405ae2..b0be09a 100644
--- a/drivers/s390/crypto/ap_bus.h
+++ b/drivers/s390/crypto/ap_bus.h
@@ -38,6 +38,7 @@
#define AP_POLL_TIME 1 /* Time in ticks between receive polls. */
extern int ap_domain_index;
+extern int ap_hwrng_seed;
/**
* The ap_qid_t identifier of an ap queue. It contains a
diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
index 0e18c5d..ed91665 100644
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -1374,6 +1374,7 @@ static int zcrypt_rng_data_read(struct hwrng *rng, u32 *data)
static struct hwrng zcrypt_rng_dev = {
.name = "zcrypt",
.data_read = zcrypt_rng_data_read,
+ .quality = 990,
};
static int zcrypt_rng_device_add(void)
@@ -1388,6 +1389,8 @@ static int zcrypt_rng_device_add(void)
goto out;
}
zcrypt_rng_buffer_index = 0;
+ if (!ap_hwrng_seed)
+ zcrypt_rng_dev.quality = 0;
rc = hwrng_register(&zcrypt_rng_dev);
if (rc)
goto out_free;
--
1.8.5.5

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