[PATCH v2 07/10] tpm: rng: Move the TPM RNG functionality to driver model

[Simon Glass]

Hi Sughosh,

On Mon, 28 Feb 2022 at 05:07, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
>
> Currently, the TPM random number generator(RNG) functions are defined
> as part of the library functions under the corresponding tpm files for
> tpmv1 and tpmv2. Move the RNG functionality under TPM RNG drivers
> complying with the driver model.
>
> Also make changes to the tpm_get_random function to have it call the
> TPM RNG driver functions instead of the library functions.
>
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
>
> Changes since V1:
> * Added existing copyrights for the rng functions taken from the tpm
>   library routines
> * Return -EIO for TPM command returning an error
> * Simplify the logic in tpm_get_random based on the review comments
>   from Ilias
>
>  drivers/rng/Makefile   |  1 +
>  drivers/rng/tpm1_rng.c | 87 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/rng/tpm2_rng.c | 86 +++++++++++++++++++++++++++++++++++++++++
>  lib/tpm-v1.c           | 44 ---------------------
>  lib/tpm-v2.c           | 44 ---------------------
>  lib/tpm_api.c          | 23 +++++++++--
>  6 files changed, 193 insertions(+), 92 deletions(-)
>  create mode 100644 drivers/rng/tpm1_rng.c
>  create mode 100644 drivers/rng/tpm2_rng.c
>
> diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> index 39f7ee3f03..129cfbd006 100644
> --- a/drivers/rng/Makefile
> +++ b/drivers/rng/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_RNG_MSM) += msm_rng.o
>  obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o
>  obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o
>  obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o
> +obj-$(CONFIG_TPM) += tpm1_rng.o tpm2_rng.o
> diff --git a/drivers/rng/tpm1_rng.c b/drivers/rng/tpm1_rng.c
> new file mode 100644
> index 0000000000..7e629756b3
> --- /dev/null
> +++ b/drivers/rng/tpm1_rng.c
> @@ -0,0 +1,87 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (c) 2013 The Chromium OS Authors.
> + * Coypright (c) 2013 Guntermann & Drunck GmbH
> + * Copyright (c) 2022, Linaro Limited
> + */
> +
> +#include <common.h>
> +#include <dm.h>
> +#include <rng.h>
> +#include <tpm-utils.h>
> +#include <tpm-v1.h>
> +
> +#include <linux/errno.h>
> +
> +#define TPM_HEADER_SIZE                10
> +
> +#define TPMV1_DATA_OFFSET      14
> +
> +/**
> + * tpm1_rng_read() - Read the random bytes from TPMv1 device
> + * @param dev          TPMv1 RNG device
> + * @param data         data buffer to write random bytes
> + * @param count                number of random bytes to read from
> + *                      the device
> + *
> + * Function to read the random bytes from the RNG pseudo device
> + * built into the TPMv1 device. Reads 'count' number of bytes
> + * from the random number generator and copies them into the
> + * 'data' buffer.
> + *
> + * Return: 0 if OK, -ve on error.
> + *
> + */
> +static int tpm1_rng_read(struct udevice *dev, void *data, size_t count)
> +{
> +       const u8 command[14] = {
> +               0x0, 0xc1,              /* TPM_TAG */
> +               0x0, 0x0, 0x0, 0xe,     /* parameter size */
> +               0x0, 0x0, 0x0, 0x46,    /* TPM_COMMAND_CODE */
> +       };
> +       const size_t length_offset = TPM_HEADER_SIZE;
> +       const size_t data_size_offset = TPM_HEADER_SIZE;
> +       const size_t data_offset = TPMV1_DATA_OFFSET;
> +       u8 buf[COMMAND_BUFFER_SIZE], response[COMMAND_BUFFER_SIZE];
> +       size_t response_length = sizeof(response);
> +       u32 data_size;
> +       u8 *out = data;
> +

The current model is that all TPM calls are set up in lib/tpm and I
don't think we should change it. You should be able to move these
functions into lib/tpm and add your random_read function to tpm_api.h

Regards,
Simon