105 lines
3.0 KiB
C
105 lines
3.0 KiB
C
/*
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* Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* Neither the name of ARM nor the names of its contributors may be used
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* to endorse or promote products derived from this software without specific
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* prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <assert.h>
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#include <mmio.h>
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#include <string.h>
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#include <utils_def.h>
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#include "juno_def.h"
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#define NSAMPLE_CLOCKS 1 /* min 1 cycle, max 231 cycles */
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#define NRETRIES 5
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static inline int output_valid(void)
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{
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int i;
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for (i = 0; i < NRETRIES; i++) {
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uint32_t val;
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val = mmio_read_32(TRNG_BASE + TRNG_STATUS);
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if (val & 1U)
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break;
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}
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if (i >= NRETRIES)
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return 0; /* No output data available. */
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return 1;
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}
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/*
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* This function fills `buf` with `len` bytes of entropy.
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* It uses the Trusted Entropy Source peripheral on Juno.
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* Returns 0 when the buffer has been filled with entropy
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* successfully and -1 otherwise.
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*/
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int juno_getentropy(void *buf, size_t len)
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{
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uint8_t *bp = buf;
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assert(buf);
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assert(len);
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assert(!check_uptr_overflow((uintptr_t)bp, len));
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/* Disable interrupt mode. */
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mmio_write_32(TRNG_BASE + TRNG_INTMASK, 0);
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/* Program TRNG to sample for `NSAMPLE_CLOCKS`. */
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mmio_write_32(TRNG_BASE + TRNG_CONFIG, NSAMPLE_CLOCKS);
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while (len > 0) {
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int i;
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/* Start TRNG. */
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mmio_write_32(TRNG_BASE + TRNG_CONTROL, 1);
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/* Check if output is valid. */
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if (!output_valid())
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return -1;
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/* Fill entropy buffer. */
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for (i = 0; i < TRNG_NOUTPUTS; i++) {
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size_t n;
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uint32_t val;
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val = mmio_read_32(TRNG_BASE + i * sizeof(uint32_t));
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n = MIN(len, sizeof(uint32_t));
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memcpy(bp, &val, n);
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bp += n;
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len -= n;
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if (len == 0)
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break;
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}
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/* Reset TRNG outputs. */
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mmio_write_32(TRNG_BASE + TRNG_STATUS, 1);
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}
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return 0;
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}
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