forked from Imagelibrary/rtems
c344e5828c
Use RTEMS_SYSINIT_ORDER_LAST_BUT_5 instead of RTEMS_SYSINIT_ORDER_LAST to allow applications and support functions to place system initialization handlers behind the standard handlers. Update #3838.
70 lines
1.4 KiB
C
70 lines
1.4 KiB
C
/*
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* Copyright (c) 2017 embedded brains GmbH. All rights reserved.
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*
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* embedded brains GmbH
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* Dornierstr. 4
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* 82178 Puchheim
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* Germany
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* <rtems@embedded-brains.de>
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*
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* The license and distribution terms for this file may be
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* found in the file LICENSE in this distribution or at
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* http://www.rtems.org/license/LICENSE.
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*/
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/*
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* ATTENTION: THIS IS A VERY LIMITED ENTROPY SOURCE.
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*
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* This implementation uses a time-based value for it's entropy. The only thing
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* that makes it random are interrupts from external sources. Don't use it if
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* you need for example a strong crypto.
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*/
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#include <sys/param.h>
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#include <unistd.h>
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#include <string.h>
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#include <rtems/bsd.h>
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#include <rtems/counter.h>
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#include <rtems/sysinit.h>
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static uint32_t state;
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int getentropy(void *ptr, size_t n)
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{
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uint8_t *dest = ptr;
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state ^= rtems_counter_read();
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state *= 25169206;
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state += 1679610226;
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while (n > 0) {
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size_t m;
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m = MIN(n, sizeof(state));
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memcpy(dest, &state, m);
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n -= m;
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dest += m;
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state *= 85236167;
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state += 30557471;
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}
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return 0;
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}
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static void getentropy_init(void)
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{
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struct bintime bt;
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rtems_bsd_bintime(&bt);
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state = (uint32_t) bt.frac;
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state ^= (uint32_t) (bt.frac >> 32);
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state ^= (uint32_t) bt.sec;
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state ^= (uint32_t) (bt.sec >> 32);
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}
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RTEMS_SYSINIT_ITEM(
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getentropy_init,
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RTEMS_SYSINIT_DEVICE_DRIVERS,
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RTEMS_SYSINIT_ORDER_LAST_BUT_5
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);
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