stm32h7/start/getentropy-rng.c

0001 /* SPDX-License-Identifier: BSD-2-Clause */
0002
0003 /*
0004  * Copyright (C) 2020 embedded brains GmbH & Co. KG
0005  *
0006  * Redistribution and use in source and binary forms, with or without
0007  * modification, are permitted provided that the following conditions
0008  * are met:
0009  * 1. Redistributions of source code must retain the above copyright
0010  *    notice, this list of conditions and the following disclaimer.
0011  * 2. Redistributions in binary form must reproduce the above copyright
0012  *    notice, this list of conditions and the following disclaimer in the
0013  *    documentation and/or other materials provided with the distribution.
0014  *
0015  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0016  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0017  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0018  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0019  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0020  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0021  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0022  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0023  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0024  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0025  * POSSIBILITY OF SUCH DAMAGE.
0026  */
0027
0028 #include <stm32h7/hal.h>
0029
0030 #include <rtems.h>
0031 #include <rtems/sysinit.h>
0032
0033 #include <sys/param.h>
0034 #include <unistd.h>
0035 #include <string.h>
0036
0037 static RNG_HandleTypeDef stm32h7_rng_instance = {
0038   .Instance = RNG,
0039   .Init.ClockErrorDetection = RNG_CED_DISABLE
0040 };
0041
0042 static void stm32h7_rng_enable(void)
0043 {
0044   stm32h7_clk_enable(STM32H7_MODULE_RNG);
0045   HAL_RNG_Init(&stm32h7_rng_instance);
0046 }
0047
0048 int getentropy(void *ptr, size_t n)
0049 {
0050   while (n > 0) {
0051     rtems_interrupt_level level;
0052     uint32_t random;
0053     bool ok;
0054     size_t copy;
0055
0056     do {
0057       rtems_interrupt_disable(level);
0058
0059       ok = (RNG->SR & RNG_FLAG_DRDY) != 0;
0060       if (ok) {
0061         random = RNG->DR;
0062       }
0063
0064       rtems_interrupt_enable(level);
0065     } while (!ok);
0066
0067     copy = MIN(sizeof(random), n);
0068     ptr = memcpy(ptr, &random, copy);
0069     n -= copy;
0070     ptr += copy;
0071   }
0072
0073   return 0;
0074 }
0075
0076 RTEMS_SYSINIT_ITEM(
0077   stm32h7_rng_enable,
0078   RTEMS_SYSINIT_DEVICE_DRIVERS,
0079   RTEMS_SYSINIT_ORDER_LAST_BUT_5
0080 );