tpm: Move Linux RNG connection to hwrng

The tpm-rng.c approach is completely inconsistent with how the kernel
handles hotplug. Instead manage a hwrng device for each TPM. This will
cause the kernel to read entropy from the TPM when it is plugged in, and
allow access to the TPM rng via /dev/hwrng.

Signed-off-by: Jason Gunthorpe <jgg@ziepe.ca>
Tested-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

6 files changed, 52 insertions, 69 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index f6e3e5abc117..88044eda0ac6 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -306,19 +306,6 @@ config HW_RANDOM_POWERNV
 
           If unsure, say Y.
 
-config HW_RANDOM_TPM
-        tristate "TPM HW Random Number Generator support"
-        depends on 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.
-
 config HW_RANDOM_HISI
         tristate "Hisilicon Random Number Generator support"
         depends on HW_RANDOM && ARCH_HISI
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index f3728d008fff..0ef05c61d9c8 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -27,7 +27,6 @@ obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
 obj-$(CONFIG_HW_RANDOM_POWERNV) += powernv-rng.o
 obj-$(CONFIG_HW_RANDOM_HISI)    += hisi-rng.o
-obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
 obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
 obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
 obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
diff --git a/drivers/char/hw_random/tpm-rng.c b/drivers/char/hw_random/tpm-rng.c
deleted file mode 100644
index c5e363825af0..000000000000
--- a/drivers/char/hw_random/tpm-rng.c
+++ /dev/null
@@ -1,50 +0,0 @@
-/*
- * 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(NULL, 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");
diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index a30352202f1f..18c81cbe4704 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -26,6 +26,17 @@ menuconfig TCG_TPM
 
 if TCG_TPM
 
+config HW_RANDOM_TPM
+        bool "TPM HW Random Number Generator support"
+        depends on TCG_TPM && HW_RANDOM && !(TCG_TPM=y && HW_RANDOM=m)
+        default y
+        ---help---
+          This setting exposes the TPM's Random Number Generator as a hwrng
+          device. This allows the kernel to collect randomness from the TPM at
+          boot, and provides the TPM randomines in /dev/hwrng.
+
+          If unsure, say Y.
+
 config TCG_TIS_CORE
         tristate
         ---help---
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index bab9c14e040c..0a62c19937b6 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -27,7 +27,7 @@
 #include <linux/freezer.h>
 #include <linux/major.h>
 #include <linux/tpm_eventlog.h>
-
+#include <linux/hw_random.h>
 #include "tpm.h"
 
 DEFINE_IDR(dev_nums_idr);
@@ -392,6 +392,26 @@ static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
 
         return 0;
 }
+
+static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+        struct tpm_chip *chip = container_of(rng, struct tpm_chip, hwrng);
+
+        return tpm_get_random(chip, data, max);
+}
+
+static int tpm_add_hwrng(struct tpm_chip *chip)
+{
+        if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM))
+                return 0;
+
+        snprintf(chip->hwrng_name, sizeof(chip->hwrng_name),
+                 "tpm-rng-%d", chip->dev_num);
+        chip->hwrng.name = chip->hwrng_name;
+        chip->hwrng.read = tpm_hwrng_read;
+        return hwrng_register(&chip->hwrng);
+}
+
 /*
  * tpm_chip_register() - create a character device for the TPM chip
  * @chip: TPM chip to use.
@@ -424,11 +444,13 @@ int tpm_chip_register(struct tpm_chip *chip)
 
         tpm_add_ppi(chip);
 
+        rc = tpm_add_hwrng(chip);
+        if (rc)
+                goto out_ppi;
+
         rc = tpm_add_char_device(chip);
-        if (rc) {
-                tpm_bios_log_teardown(chip);
-                return rc;
-        }
+        if (rc)
+                goto out_hwrng;
 
         rc = tpm_add_legacy_sysfs(chip);
         if (rc) {
@@ -437,6 +459,14 @@ int tpm_chip_register(struct tpm_chip *chip)
         }
 
         return 0;
+
+out_hwrng:
+        if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
+                hwrng_unregister(&chip->hwrng);
+out_ppi:
+        tpm_bios_log_teardown(chip);
+
+        return rc;
 }
 EXPORT_SYMBOL_GPL(tpm_chip_register);
 
@@ -456,6 +486,8 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
 void tpm_chip_unregister(struct tpm_chip *chip)
 {
         tpm_del_legacy_sysfs(chip);
+        if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
+                hwrng_unregister(&chip->hwrng);
         tpm_bios_log_teardown(chip);
         if (chip->flags & TPM_CHIP_FLAG_TPM2)
                 cdev_device_del(&chip->cdevs, &chip->devs);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 6c189174c0d3..605c0be2b8dc 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -26,6 +26,7 @@
 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/fs.h>
+#include <linux/hw_random.h>
 #include <linux/mutex.h>
 #include <linux/sched.h>
 #include <linux/platform_device.h>
@@ -211,6 +212,9 @@ struct tpm_chip {
         int dev_num;            /* /dev/tpm# */
         unsigned long is_open;  /* only one allowed */
 
+        char hwrng_name[64];
+        struct hwrng hwrng;
+
         struct mutex tpm_mutex; /* tpm is processing */
 
         unsigned long timeout_a; /* jiffies */