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

[Sughosh Ganu]

hi Simon,

On Tue, 1 Mar 2022 at 20:28, Simon Glass <sjg at chromium.org> wrote:
>
> 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

I moved these functions under separate drivers as I thought that
looked cleaner as against exporting the driver interface in
tpm-v{1,2}.c. If you strongly feel that these should remain under
lib/tpm, I will make the change. But I believe you do not have a
problem with exporting these rng functions as part of the driver
model. We do need that so that the EFI_RNG_PROTOCOL can use these for
getting the random bytes.

-sughosh

>
> Regards,
> Simon