[PATCH 2/2] hw_random: add support for the TPM chip as a hardware RNG source

[Kent Yoder <key@linux.vnet.ibm.com>]

This driver will make use of any available TPM chip on the system as a
hwrng source.

Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>
---
 drivers/char/hw_random/Kconfig   |   13 +++++++++
 drivers/char/hw_random/Makefile  |    1 +
 drivers/char/hw_random/tpm-rng.c |   55 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+), 0 deletions(-)
 create mode 100644 drivers/char/hw_random/tpm-rng.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index f45dad3..4e8c01a 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -263,3 +263,16 @@ config HW_RANDOM_PSERIES
 	  module will be called pseries-rng.
 
 	  If unsure, say Y.
+
+config HW_RANDOM_TPM
+	tristate "TPM HW Random Number Generator support"
+	depends on HW_RANDOM && TCG_TPM
+	default HW_RANDOM
+	---help---
+	  This driver provides kernel-side support for the Random Number
+	  Generator in the Trusted Platform Module
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called tpm-rng.
+
+	  If unsure, say Y.
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index d901dfa..5dc10da 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -23,3 +23,4 @@ obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
 obj-$(CONFIG_HW_RANDOM_PICOXCELL) += picoxcell-rng.o
 obj-$(CONFIG_HW_RANDOM_PPC4XX) += ppc4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
+obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
diff --git a/drivers/char/hw_random/tpm-rng.c b/drivers/char/hw_random/tpm-rng.c
new file mode 100644
index 0000000..a869b42c
--- /dev/null
+++ b/drivers/char/hw_random/tpm-rng.c
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2012 Kent Yoder IBM Corporation
+ *
+ * HWRNG interfaces to pull RNG data from a TPM
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/module.h>
+#include <linux/hw_random.h>
+#include <linux/tpm.h>
+
+#define MODULE_NAME "tpm-rng"
+
+static int tpm_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	int err;
+	size_t tpm_max = max;
+
+	err = tpm_get_random(TPM_ANY_NUM, data, &tpm_max);
+
+	return err ? 0 : tpm_max;
+}
+
+static struct hwrng tpm_rng = {
+	.name = MODULE_NAME,
+	.read = tpm_rng_read,
+};
+
+static int __init rng_init(void)
+{
+	return hwrng_register(&tpm_rng);
+}
+module_init(rng_init);
+
+static void __exit rng_exit(void)
+{
+	hwrng_unregister(&tpm_rng);
+}
+module_exit(rng_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Kent Yoder <key@linux.vnet.ibm.com>");
+MODULE_DESCRIPTION("RNG driver for TPM devices");
-- 
1.7.5.4