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

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Message-Id: <1406722656-6506-1-git-send-email-ingo.tuchscherer@de.ibm.com>
Date:	Wed, 30 Jul 2014 14:17:36 +0200
From:	Ingo Tuchscherer <ingo.tuchscherer@...ibm.com>
To:	linux-kernel@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>
Cc:	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	Heiko Carstens <heicars2@...ux.vnet.ibm.com>,
	Torsten Duwe <duwe@...e.de>,
	Hendrik Brueckner <brueckner@...ibm.com>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Harald Freudenberger <freude@...ibm.com>,
	Ingo Tuchscherer <ingo.tuchscherer@...ux.vnet.ibm.com>,
	Ingo Tuchscherer <ingo.tuchscherer@...ibm.com>
Subject: [PATCH] s390/zcrypt: enable s390 hwrng to seed kernel entropy

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).

Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@...ibm.com>
---
 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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