[PATCH v2] tpm: Move Linux RNG connection to hwrng

Jason Gunthorpe
2017-10-31T20:05:05Z

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: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
---
drivers/char/hw_random/Kconfig | 13 -----------
drivers/char/hw_random/Makefile | 1 -
drivers/char/hw_random/tpm-rng.c | 50 ----------------------------------------
drivers/char/tpm/Kconfig | 11 +++++++++
drivers/char/tpm/tpm-chip.c | 41 ++++++++++++++++++++++++++++----
drivers/char/tpm/tpm.h | 4 ++++
6 files changed, 52 insertions(+), 68 deletions(-)
delete mode 100644 drivers/char/hw_random/tpm-rng.c

v2 applies against Jarkko's patch
"tpm: use struct tpm_chip for tpm_chip_find_get()"

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 95a031e9eced07..a20fed182cbcce 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 39a67defac67cb..91cb8e8213e7c1 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -26,7 +26,6 @@ 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 c5e363825af008..00000000000000
--- 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 a30352202f1fdc..18c81cbe4704ca 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 6faf4c3fa6dbbd..797ab962291333 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -26,6 +26,7 @@
#include <linux/spinlock.h>
#include <linux/freezer.h>
#include <linux/major.h>
+#include <linux/hw_random.h>
#include "tpm.h"
#include "tpm_eventlog.h"

@@ -391,6 +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.
@@ -423,11 +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) {
@@ -436,6 +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);

@@ -455,6 +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 7424511241031a..efe8ad0d137f74 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>
@@ -210,6 +211,9 @@ 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 */
--
2.7.4