Re: [PATCH v6 2/7] tpm: rng: Add driver model interface for TPM RNG device

On Mon, Jul 04, 2022 at 07:04:39PM +0530, Sughosh Ganu wrote:

The TPM device has a builtin random number generator(RNG) functionality. Expose the RNG functions of the TPM device to the driver model so that they can be used by the EFI_RNG_PROTOCOL if the protocol is installed.

Also change the function arguments and return type of the random number functions to comply with the driver model api.

Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org

Changes since V5:

• Use the dev_get_parent() interface for getting the TPM device when calling the tpm_get_random() function

drivers/rng/Kconfig | 11 +++++++++++ drivers/rng/Makefile | 1 + drivers/rng/tpm_rng.c | 23 +++++++++++++++++++++++ lib/Kconfig | 1 + lib/tpm-v1.c | 13 +++++++------ lib/tpm-v2.c | 6 +++--- lib/tpm_api.c | 6 +++--- 7 files changed, 49 insertions(+), 12 deletions(-) create mode 100644 drivers/rng/tpm_rng.c

diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig index c10f7d345b..67c65311c7 100644 --- a/drivers/rng/Kconfig +++ b/drivers/rng/Kconfig @@ -58,4 +58,15 @@ config RNG_IPROC200 depends on DM_RNG help Enable random number generator for RPI4.

+config TPM_RNG

• bool "Enable random number generator on TPM device"
• depends on TPM
• default y
• help

•  The TPM device has an inbuilt random number generator
  

•  functionality. Enable random number generator on TPM
  

•  devices.
  

Maybe we discussed this on a previous version, but why do we want to have this as a config option? Code size? A TPM will always be able to generate a random number. Couldn't we compile this based on an existing TPM Kconfig option?

endif diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile index 435b3b965a..e4ca9c4149 100644 --- a/drivers/rng/Makefile +++ b/drivers/rng/Makefile @@ -11,3 +11,4 @@ obj-$(CONFIG_RNG_OPTEE) += optee_rng.o obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o +obj-$(CONFIG_TPM_RNG) += tpm_rng.o diff --git a/drivers/rng/tpm_rng.c b/drivers/rng/tpm_rng.c new file mode 100644 index 0000000000..1a5e9e2e4b --- /dev/null +++ b/drivers/rng/tpm_rng.c @@ -0,0 +1,23 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/*

• • Copyright (c) 2022, Linaro Limited
• */

+#include <dm.h> +#include <rng.h> +#include <tpm_api.h>

+static int rng_tpm_random_read(struct udevice *dev, void *data, size_t count) +{

• return tpm_get_random(dev_get_parent(dev), data, count);

+}

+static const struct dm_rng_ops tpm_rng_ops = {

• .read = rng_tpm_random_read,

+};

+U_BOOT_DRIVER(tpm_rng) = {

• .name = "tpm-rng",
• .id = UCLASS_RNG,
• .ops = &tpm_rng_ops,

+}; diff --git a/lib/Kconfig b/lib/Kconfig index acc0ac081a..17efaa4c80 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -358,6 +358,7 @@ source lib/crypt/Kconfig config TPM bool "Trusted Platform Module (TPM) Support" depends on DM

• imply DM_RNG help This enables support for TPMs which can be used to provide security features for your board. The TPM can be connected via LPC or I2C

diff --git a/lib/tpm-v1.c b/lib/tpm-v1.c index 22a769c587..f7091e5bc7 100644 --- a/lib/tpm-v1.c +++ b/lib/tpm-v1.c @@ -9,12 +9,13 @@ #include <common.h> #include <dm.h> #include <log.h> -#include <asm/unaligned.h> -#include <u-boot/sha1.h> #include <tpm-common.h> #include <tpm-v1.h> #include "tpm-utils.h"

+#include <asm/unaligned.h> +#include <u-boot/sha1.h>

#ifdef CONFIG_TPM_AUTH_SESSIONS

#ifndef CONFIG_SHA1 @@ -892,19 +893,19 @@ u32 tpm1_get_random(struct udevice *dev, void *data, u32 count) if (pack_byte_string(buf, sizeof(buf), "sd", 0, command, sizeof(command), length_offset, this_bytes))

• 	return TPM_LIB_ERROR;
  

• 	return -EIO;
  

  err = tpm_sendrecv_command(dev, buf, response, &response_length); if (err) return err; if (unpack_byte_string(response, response_length, "d", data_size_offset, &data_size))

• 	return TPM_LIB_ERROR;
  

• 	return -EIO;
  

  if (data_size > count)

• 	return TPM_LIB_ERROR;
  

• 	return -EIO;
  

  if (unpack_byte_string(response, response_length, "s", data_offset, out, data_size))

• 	return TPM_LIB_ERROR;
  

• 	return -EIO;
  
  

  count -= data_size; out += data_size;

diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c index 1bf627853a..abca9a14b0 100644 --- a/lib/tpm-v2.c +++ b/lib/tpm-v2.c @@ -585,19 +585,19 @@ u32 tpm2_get_random(struct udevice *dev, void *data, u32 count) if (pack_byte_string(buf, sizeof(buf), "sw", 0, command_v2, sizeof(command_v2), sizeof(command_v2), this_bytes))

• 	return TPM_LIB_ERROR;
  

• 	return -EIO;
  

  err = tpm_sendrecv_command(dev, buf, response, &response_length); if (err) return err; if (unpack_byte_string(response, response_length, "w", data_size_offset, &data_size))

• 	return TPM_LIB_ERROR;
  

• 	return -EIO;
  

  if (data_size > this_bytes) return TPM_LIB_ERROR; if (unpack_byte_string(response, response_length, "s", data_offset, out, data_size))

• 	return TPM_LIB_ERROR;
  

• 	return -EIO;
  
  

  count -= data_size; out += data_size;

diff --git a/lib/tpm_api.c b/lib/tpm_api.c index 4ac4612c81..032f383ca0 100644 --- a/lib/tpm_api.c +++ b/lib/tpm_api.c @@ -269,7 +269,7 @@ u32 tpm_get_random(struct udevice *dev, void *data, u32 count) if (tpm_is_v1(dev)) return tpm1_get_random(dev, data, count); else if (tpm_is_v2(dev))

• return -ENOSYS; /* not implemented yet */
  

• else

• return -ENOSYS;
  

• return tpm2_get_random(dev, data, count);
  

• return -ENOSYS;

}

2.25.1

Thanks /Ilias