85 lines
2.8 KiB
C
85 lines
2.8 KiB
C
/* rand32.c - non-random number generator */
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/*
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* Copyright (c) 2013-2014 Wind River Systems, Inc.
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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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* 1) Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* 2) 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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* 3) Neither the name of Wind River Systems nor the names of its contributors
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* may be used to endorse or promote products derived from this software without
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* specific 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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/*
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DESCRIPTION
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This module provides a non-random implementation of _Rand32Get(), which is not
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meant to be used in a final product as a truly random number generator. It
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was provided to allow testing of kernel stack canaries on a BSP that does not
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(yet) provide a random number generator.
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*/
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#include <drivers/rand32.h>
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#if defined(CONFIG_TEST_RANDOM_GENERATOR)
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/*******************************************************************************
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*
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* _Rand32Init - initialize the random number generator
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*
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* The non-random number generator does not require any initialization.
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*
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* RETURNS: N/A
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*/
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void _Rand32Init(void)
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{
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}
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/*******************************************************************************
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*
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* _Rand32Get - get a 32 bit random number
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*
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* The non-random number generator returns values that are based off the
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* CPU's timestamp counter, which means that successive calls will normally
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* display ever-increasing values.
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*
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* RETURNS: a 32-bit number
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*/
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#if defined(__GNUC__)
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uint32_t _Rand32Get(void)
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{
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uint32_t rv;
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__asm__ volatile("rdtsc" : "=a"(rv) : : "%edx");
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return rv;
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}
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#elif defined(__DCC__)
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__asm volatile uint32_t _Rand32Get(void)
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{
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% !"ax", "dx" rdtsc
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}
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#endif /* __GNUCC__/__DCC__ */
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#endif /* CONFIG_TEST_RANDOM_GENERATOR */
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