[PATCH v4 5/8] sandbox: rng: Add a random number generator(rng) driver

[Sughosh Ganu]

On Wed, 25 Dec 2019 at 03:44, Heinrich Schuchardt <xypron.glpk at gmx.de>
wrote:

> Resending with Cc Tom, Simon, Ilias
>
> On 12/17/19 12:52 PM, Sughosh Ganu wrote:
> > Add a sandbox driver for random number generation. Mostly aimed at
> > providing a unit test for rng uclass.
> >
> > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > Reviewed-by: Patrice Chotard <patrice.chotard at st.com>
> > ---
> > Changes since V3:
> >   Handle review comments from Patrick Delaunay.
> >
> >   arch/sandbox/dts/test.dts |  4 ++++
> >   drivers/rng/Kconfig       |  7 +++++++
> >   drivers/rng/Makefile      |  1 +
> >   drivers/rng/sandbox_rng.c | 39 +++++++++++++++++++++++++++++++++++++++
> >   4 files changed, 51 insertions(+)
> >   create mode 100644 drivers/rng/sandbox_rng.c
> >
> > diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
> > index fdb08f2..2c85540 100644
> > --- a/arch/sandbox/dts/test.dts
> > +++ b/arch/sandbox/dts/test.dts
> > @@ -599,6 +599,10 @@
> >               reset-names = "other", "test";
> >       };
> >
> > +     rng at 0 {
> > +             compatible = "sandbox,sandbox-rng";
> > +     };
> > +
> >       rproc_1: rproc at 1 {
> >               compatible = "sandbox,test-processor";
> >               remoteproc-name = "remoteproc-test-dev1";
> > diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
> > index 5fc11db..3a1d3f0 100644
> > --- a/drivers/rng/Kconfig
> > +++ b/drivers/rng/Kconfig
> > @@ -6,6 +6,13 @@ config DM_RNG
> >         This interface is used to initialise the rng device and to
> >         read the random seed from the device.
> >
> > +config RNG_SANDBOX
> > +       bool "Sandbox random number generator"
> > +       depends on SANDBOX && DM_RNG
> > +       help
> > +         Enable random number generator for sandbox. This is an
> > +      emulation of a rng device.
> > +
> >   config RNG_STM32MP1
> >          bool "Enable random number generator for STM32MP1"
> >          depends on ARCH_STM32MP && DM_RNG
> > diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> > index 699beb3..3517005 100644
> > --- a/drivers/rng/Makefile
> > +++ b/drivers/rng/Makefile
> > @@ -4,4 +4,5 @@
> >   #
> >
> >   obj-$(CONFIG_DM_RNG) += rng-uclass.o
> > +obj-$(CONFIG_RNG_SANDBOX) += sandbox_rng.o
> >   obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o
> > diff --git a/drivers/rng/sandbox_rng.c b/drivers/rng/sandbox_rng.c
> > new file mode 100644
> > index 0000000..8262e0d
> > --- /dev/null
> > +++ b/drivers/rng/sandbox_rng.c
> > @@ -0,0 +1,39 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (c) 2019, Linaro Limited
> > + */
> > +
> > +#include <common.h>
> > +#include <dm.h>
> > +#include <rng.h>
> > +
> > +static unsigned long random = 0xdeadbeef;
> > +
> > +static int sandbox_rng_read(struct udevice *dev, void *data, size_t len)
> > +{
> > +     if (len != sizeof(random))
> > +             return -EINVAL;
>
> This will drop on our feet once we use the RNG class for anything real.
>
> Just imagine an EFI_RNG_PROTOCOL test failing on the sandbox because we
> cannot read 128 bit.
>
> Can't we use a PRNG here and reinitialize it when len == ~0UL?
>
> Functions rand() and srand() are good enough for the job.
>

Have sent a V5 using srand and rand functions for returning random bytes.
Please take a look. Thanks.

-sughosh