hw_random: add support for the TPM chip as a hardware RNG source

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

Acked-by: David Safford <safford@linux.vnet.ibm.com>
Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>

3 files changed, 64 insertions, 0 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 7c0d391996b..fbd9b2b850e 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -289,3 +289,16 @@ config HW_RANDOM_EXYNOS
           module will be called exynos-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 39a757ca15b..1fd7eec9fbf 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -25,3 +25,4 @@ 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_EXYNOS)  += exynos-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 00000000000..d6d448266f0
--- /dev/null
+++ b/drivers/char/hw_random/tpm-rng.c
@@ -0,0 +1,50 @@
+/*
+ * 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)
+{
+        return tpm_get_random(TPM_ANY_NUM, data, 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");