/**************************************************************************** * arch/arm/src/stm32/stm32_rng.c * * Copyright (C) 2012 Max Holtzberg. All rights reserved. * Author: Max Holtzberg * * 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 #include #include #include #include #include #include #include #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); }