a212d0b2e8
srandom(9) is meaningless on SMP systems or any system with, say, interrupts. One could never rely on random(9) to produce a reproducible sequence of outputs on the basis of a specific srandom() seed because the global state was shared by all kernel contexts. As such, removing it is literally indistinguishable to random(9) consumers (as compared with retaining it). Mark random(9) as deprecated and slated for quick removal. This is not to say we intend to remove all fast, non-cryptographic PRNG(s) in the kernel. It/they just won't be random(9), as it exists today, in either name or implementation. Before random(9) is removed, a replacement will be provided and in-tree consumers will be converted. Note that despite the name, the random(9) interface does not bear any resemblance to random(3). Instead, it is the same crummy 1988 Park-Miller LCG used in libc rand(3).
79 lines
2.7 KiB
C
79 lines
2.7 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. 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
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* 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 REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)random.c 8.1 (Berkeley) 6/10/93
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/libkern.h>
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#include <sys/systm.h>
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static u_long randseed = 937186357; /* after srandom(1), NSHUFF counted */
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/*
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* Pseudo-random number generator for perturbing the profiling clock,
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* and whatever else we might use it for. The result is uniform on
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* [0, 2^31 - 1].
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*/
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u_long
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random(void)
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{
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static bool warned = false;
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long x, hi, lo, t;
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/* Warn only once, or it gets very spammy. */
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if (!warned) {
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gone_in(13,
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"random(9) is the obsolete Park-Miller LCG from 1988");
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warned = true;
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}
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/*
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* Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
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* From "Random number generators: good ones are hard to find",
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* Park and Miller, Communications of the ACM, vol. 31, no. 10,
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* October 1988, p. 1195.
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*/
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/* Can't be initialized with 0, so use another value. */
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if ((x = randseed) == 0)
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x = 123459876;
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hi = x / 127773;
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lo = x % 127773;
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t = 16807 * lo - 2836 * hi;
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if (t < 0)
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t += 0x7fffffff;
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randseed = t;
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return (t);
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}
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