3e455e9792
The same seed will only occur if the board is the same, the RTC has the same time (eg freshly powered up) and the first call to this function (eg via an "import random") is done at exactly the same time since reset. Signed-off-by: Damien George <damien@micropython.org>
101 lines
3.2 KiB
C
101 lines
3.2 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2013-2018 Damien P. George
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "rtc.h"
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#include "rng.h"
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#if MICROPY_HW_ENABLE_RNG
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#define RNG_TIMEOUT_MS (10)
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uint32_t rng_get(void) {
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// Enable the RNG peripheral if it's not already enabled
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if (!(RNG->CR & RNG_CR_RNGEN)) {
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#if defined(STM32H7)
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// Set RNG Clock source
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__HAL_RCC_PLLCLKOUT_ENABLE(RCC_PLL1_DIVQ);
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__HAL_RCC_RNG_CONFIG(RCC_RNGCLKSOURCE_PLL);
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#endif
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__HAL_RCC_RNG_CLK_ENABLE();
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RNG->CR |= RNG_CR_RNGEN;
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}
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// Wait for a new random number to be ready, takes on the order of 10us
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uint32_t start = HAL_GetTick();
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while (!(RNG->SR & RNG_SR_DRDY)) {
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if (HAL_GetTick() - start >= RNG_TIMEOUT_MS) {
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return 0;
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}
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}
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// Get and return the new random number
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return RNG->DR;
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}
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// Return a 30-bit hardware generated random number.
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STATIC mp_obj_t pyb_rng_get(void) {
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return mp_obj_new_int(rng_get() >> 2);
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}
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MP_DEFINE_CONST_FUN_OBJ_0(pyb_rng_get_obj, pyb_rng_get);
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#else // MICROPY_HW_ENABLE_RNG
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// For MCUs that don't have an RNG we still need to provide a rng_get() function,
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// eg for lwIP and random.seed(). A pseudo-RNG is not really ideal but we go with
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// it for now, seeding with numbers which will be somewhat different each time. We
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// don't want to use urandom's pRNG because then the user won't see a reproducible
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// random stream.
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// Yasmarang random number generator by Ilya Levin
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// http://www.literatecode.com/yasmarang
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STATIC uint32_t pyb_rng_yasmarang(void) {
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static bool seeded = false;
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static uint32_t pad = 0, n = 0, d = 0;
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static uint8_t dat = 0;
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if (!seeded) {
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seeded = true;
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rtc_init_finalise();
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pad = *(uint32_t *)MP_HAL_UNIQUE_ID_ADDRESS ^ SysTick->VAL;
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n = RTC->TR;
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d = RTC->SSR;
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}
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pad += dat + d * n;
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pad = (pad << 3) + (pad >> 29);
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n = pad | 2;
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d ^= (pad << 31) + (pad >> 1);
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dat ^= (char)pad ^ (d >> 8) ^ 1;
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return pad ^ (d << 5) ^ (pad >> 18) ^ (dat << 1);
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}
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uint32_t rng_get(void) {
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return pyb_rng_yasmarang();
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}
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#endif // MICROPY_HW_ENABLE_RNG
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