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>

1 files changed, 50 insertions, 0 deletions

diff --git a/drivers/char/hw_random/tpm-rng.c b/drivers/char/hw_random/tpm-rng.c
new file mode 100644
index 000000000000..d6d448266f07
--- /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");