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author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2012-09-29 20:34:25 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2012-09-29 20:34:25 +0000 |
commit | 96a334a758bbdc466ba8ae0cb20f2f79958623ec (patch) | |
tree | 30c5dcd88c8d3a48442681bf495501d0b092d264 /nuttx/arch/arm/src/stm32/stm32_rng.c | |
parent | 253d3ab52353d640f11a95a148105d04d96a1d29 (diff) | |
download | px4-firmware-96a334a758bbdc466ba8ae0cb20f2f79958623ec.tar.gz px4-firmware-96a334a758bbdc466ba8ae0cb20f2f79958623ec.tar.bz2 px4-firmware-96a334a758bbdc466ba8ae0cb20f2f79958623ec.zip |
Implementation of /dev/random using the STM32 Random Number Generator (RNG)
git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5207 42af7a65-404d-4744-a932-0658087f49c3
Diffstat (limited to 'nuttx/arch/arm/src/stm32/stm32_rng.c')
-rw-r--r-- | nuttx/arch/arm/src/stm32/stm32_rng.c | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/nuttx/arch/arm/src/stm32/stm32_rng.c b/nuttx/arch/arm/src/stm32/stm32_rng.c new file mode 100644 index 000000000..38e8108fe --- /dev/null +++ b/nuttx/arch/arm/src/stm32/stm32_rng.c @@ -0,0 +1,264 @@ +/**************************************************************************** + * 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 <stdio.h> +#include <stdbool.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" + +/**************************************************************************** + * Private Function Prototypes + ****************************************************************************/ + +static int stm32_rnginitialize(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 + ,0 /* poll */ +#endif +}; + +/**************************************************************************** + * Private functions + ****************************************************************************/ + +static int stm32_rnginitialize() +{ + uint32_t regval; + + vdbg("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 */ + + vdbg("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; + *(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 + ****************************************************************************/ + +void up_rnginitialize() +{ + stm32_rnginitialize(); + register_driver("/dev/random", &g_rngops, 0444, NULL); +} |