82 lines
1.8 KiB
C
82 lines
1.8 KiB
C
/*
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* Copyright (c) 2016 ARM Limited.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <device.h>
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#include <entropy.h>
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#include <random/rand32.h>
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#include <init.h>
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#include "fsl_rnga.h"
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static u8_t entropy_mcux_rnga_get_uint8(void)
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{
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u32_t random;
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u8_t output = 0;
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int i;
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RNGA_SetMode(RNG, kRNGA_ModeNormal);
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/* The Reference manual states that back to back reads from
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* the RNGA deliver one or two bits of entropy per 32-bit
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* word, therefore to deliver 8 bits of entropy we need
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* between 4 and 8 samples. Conservatively, we take 8.
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*/
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for (i = 0; i < 8; i++) {
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status_t status;
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status = RNGA_GetRandomData(RNG, &random, sizeof(random));
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__ASSERT_NO_MSG(!status);
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output ^= random;
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}
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RNGA_SetMode(RNG, kRNGA_ModeSleep);
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return output;
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}
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static int entropy_mcux_rnga_get_entropy(struct device *dev, u8_t *buffer,
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u16_t length)
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{
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int i;
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ARG_UNUSED(dev);
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for (i = 0; i < length; i++) {
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buffer[i] = entropy_mcux_rnga_get_uint8();
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}
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return 0;
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}
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static const struct entropy_driver_api entropy_mcux_rnga_api_funcs = {
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.get_entropy = entropy_mcux_rnga_get_entropy
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};
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static int entropy_mcux_rnga_init(struct device *);
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DEVICE_AND_API_INIT(entropy_mcux_rnga, CONFIG_ENTROPY_NAME,
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entropy_mcux_rnga_init, NULL, NULL,
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PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
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&entropy_mcux_rnga_api_funcs);
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static int entropy_mcux_rnga_init(struct device *dev)
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{
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u32_t seed = k_cycle_get_32();
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ARG_UNUSED(dev);
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RNGA_Init(RNG);
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/* The range of seed values acquired by this method is likely
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* to be relatively small. The RNGA hardware uses two free
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* running oscillators to add entropy to the seed value, we
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* take care below to ensure the read rate is lower than the
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* rate at which the hardware can add entropy.
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*/
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RNGA_Seed(RNG, seed);
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RNGA_SetMode(RNG, kRNGA_ModeSleep);
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return 0;
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}
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