nuttx/arch/arm/src/stm32/stm32_rng.c

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/****************************************************************************
* arch/arm/src/stm32/stm32_rng.c
*
* Copyright (C) 2012 Max Holtzberg. All rights reserved.
* Author: Max Holtzberg <mh@uvc.de>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/irq.h>
#include <nuttx/arch.h>
#include "up_arch.h"
#include "chip/stm32_rng.h"
#include "up_internal.h"
#if defined(CONFIG_STM32_RNG)
#if defined(CONFIG_DEV_RANDOM) || defined(CONFIG_DEV_URANDOM_ARCH)
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int stm32_rng_initialize(void);
static int stm32_interrupt(int irq, void *context);
static void stm32_enable(void);
static void stm32_disable(void);
static ssize_t stm32_read(struct file *filep, char *buffer, size_t);
/****************************************************************************
* Private Types
****************************************************************************/
struct rng_dev_s
{
sem_t rd_devsem; /* Threads can only exclusively access the RNG */
sem_t rd_readsem; /* To block until the buffer is filled */
char *rd_buf;
size_t rd_buflen;
uint32_t rd_lastval;
bool rd_first;
};
/****************************************************************************
* Private Data
****************************************************************************/
static struct rng_dev_s g_rngdev;
static const struct file_operations g_rngops =
{
0, /* open */
0, /* close */
stm32_read, /* read */
0, /* write */
0, /* seek */
0 /* ioctl */
#ifndef CONFIG_DISABLE_POLL
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, 0 /* poll */
#endif
};
/****************************************************************************
* Private functions
****************************************************************************/
static int stm32_rng_initialize()
{
uint32_t regval;
_info("Initializing RNG\n");
memset(&g_rngdev, 0, sizeof(struct rng_dev_s));
sem_init(&g_rngdev.rd_devsem, 0, 1);
if (irq_attach(STM32_IRQ_RNG, stm32_interrupt))
{
/* We could not attach the ISR to the interrupt */
_info("Could not attach IRQ.\n");
return -EAGAIN;
}
/* Enable interrupts */
regval = getreg32(STM32_RNG_CR);
regval |= RNG_CR_IE;
putreg32(regval, STM32_RNG_CR);
up_enable_irq(STM32_IRQ_RNG);
return OK;
}
static void stm32_enable()
{
uint32_t regval;
g_rngdev.rd_first = true;
regval = getreg32(STM32_RNG_CR);
regval |= RNG_CR_RNGEN;
putreg32(regval, STM32_RNG_CR);
}
static void stm32_disable()
{
uint32_t regval;
regval = getreg32(STM32_RNG_CR);
regval &= ~RNG_CR_RNGEN;
putreg32(regval, STM32_RNG_CR);
}
static int stm32_interrupt(int irq, void *context)
{
uint32_t rngsr;
uint32_t data;
rngsr = getreg32(STM32_RNG_SR);
if ((rngsr & (RNG_SR_SEIS | RNG_SR_CEIS)) /* Check for error bits */
|| !(rngsr & RNG_SR_DRDY)) /* Data ready must be set */
{
/* This random value is not valid, we will try again. */
return OK;
}
data = getreg32(STM32_RNG_DR);
/* As required by the FIPS PUB (Federal Information Processing Standard
* Publication) 140-2, the first random number generated after setting the
* RNGEN bit should not be used, but saved for comparison with the next
* generated random number. Each subsequent generated random number has to be
* compared with the previously generated number. The test fails if any two
* compared numbers are equal (continuous random number generator test).
*/
if (g_rngdev.rd_first)
{
g_rngdev.rd_first = false;
g_rngdev.rd_lastval = data;
return OK;
}
if (g_rngdev.rd_lastval == data)
{
/* Two subsequent same numbers, we will try again. */
return OK;
}
/* If we get here, the random number is valid. */
g_rngdev.rd_lastval = data;
if (g_rngdev.rd_buflen >= 4)
{
g_rngdev.rd_buflen -= 4;
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*(uint32_t *)&g_rngdev.rd_buf[g_rngdev.rd_buflen] = data;
}
else
{
while (g_rngdev.rd_buflen > 0)
{
g_rngdev.rd_buf[--g_rngdev.rd_buflen] = (char)data;
data >>= 8;
}
}
if (g_rngdev.rd_buflen == 0)
{
/* Buffer filled, stop further interrupts. */
stm32_disable();
sem_post(&g_rngdev.rd_readsem);
}
return OK;
}
/****************************************************************************
* Name: stm32_read
****************************************************************************/
static ssize_t stm32_read(struct file *filep, char *buffer, size_t buflen)
{
if (sem_wait(&g_rngdev.rd_devsem) != OK)
{
return -errno;
}
else
{
/* We've got the semaphore. */
/* Initialize semaphore with 0 for blocking until the buffer is filled from
* interrupts.
*/
sem_init(&g_rngdev.rd_readsem, 0, 1);
g_rngdev.rd_buflen = buflen;
g_rngdev.rd_buf = buffer;
/* Enable RNG with interrupts */
stm32_enable();
/* Wait until the buffer is filled */
sem_wait(&g_rngdev.rd_readsem);
/* Free RNG for next use */
sem_post(&g_rngdev.rd_devsem);
return buflen;
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: devrandom_register
*
* Description:
* Initialize the RNG hardware and register the /dev/random driver.
* Must be called BEFORE devurandom_register.
*
* Input Parameters:
* None
*
* Returned Value:
* None
*
****************************************************************************/
#ifdef CONFIG_DEV_RANDOM
int devrandom_register(void)
{
stm32_rng_initialize();
return register_driver("/dev/random", &g_rngops, 0444, NULL);
}
#endif
/****************************************************************************
* Name: devurandom_register
*
* Description:
* Register /dev/urandom
*
****************************************************************************/
#ifdef CONFIG_DEV_URANDOM_ARCH
int devurandom_register(void)
{
#ifndef CONFIG_DEV_RANDOM
stm32l4_rnginitialize();
#endif
return register_driver("/dev/urandom", &g_rngops, 0444, NULL);
}
#endif
#endif /* CONFIG_DEV_RANDOM || CONFIG_DEV_URANDOM_ARCH */
#endif /* CONFIG_STM32_RNG */