Re: [PATCH v5 5/8] sandbox: rng: Add a random number generator(rng) driver

On 12/26/19 6:25 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@linaro.org Reviewed-by: Patrice Chotard patrice.chotard@st.com

---

Changes since V4:

• Return number of bytes read on a successful read, and a -ve value on error.

• Modify the logic of sandbox_rng_read function to use rand and srand functions to return random data, based on feedback from Heinrich Schuchardt.

  arch/sandbox/dts/test.dts | 4 ++++ drivers/rng/Kconfig | 8 +++++++ drivers/rng/Makefile | 1 + drivers/rng/sandbox_rng.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 69 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@0 {

• compatible = "sandbox,sandbox-rng";
  

• };
• rproc_1: rproc@1 { compatible = "sandbox,test-processor"; remoteproc-name = "remoteproc-test-dev1";

diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig index c9c4751..35a3bd1 100644 --- a/drivers/rng/Kconfig +++ b/drivers/rng/Kconfig @@ -6,6 +6,14 @@ 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
• select CONFIG_LIB_RAND
• 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..5de1799 --- /dev/null +++ b/drivers/rng/sandbox_rng.c @@ -0,0 +1,56 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/*

• • Copyright (c) 2019, Linaro Limited
• */

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

+#include <linux/string.h>

+static int sandbox_rng_read(struct udevice *dev, void *data, size_t len) +{

• int nbytes;
• unsigned int i, seed;
• unsigned int *buf = data;

You assume here that data is 4 byte aligned which may not hold true and hence may lead to a crash on ARM.

Best regards

Heinrich

• size_t nrem, nloops;
• /*

• * Only INT_MAX number of bytes can be returned. If more
  

• * bytes need to be read, the caller must do it in a loop.
  

• */
  

• if (len > INT_MAX)

• len = INT_MAX;
  

• nbytes = len;
• nloops = len / sizeof(unsigned int);
• seed = get_timer(0) ^ rand();
• srand(seed);
• for (i = 0, nrem = len; i < nloops; i++, nrem -= sizeof(unsigned int))

• *buf++ = rand();
  

• seed = rand();
• memcpy(buf, &seed, nrem);
• return nbytes;

+}

+static const struct dm_rng_ops sandbox_rng_ops = {

• .read = sandbox_rng_read,

+};

+static const struct udevice_id sandbox_rng_match[] = {

• {

• .compatible = "sandbox,sandbox-rng",
  

• },
• {},

+};

+U_BOOT_DRIVER(sandbox_rng) = {

• .name = "sandbox-rng",
• .id = UCLASS_RNG,
• .of_match = sandbox_rng_match,
• .ops = &sandbox_rng_ops,

+};